CHAPTER 8
COMPONENT DEVELOPMENT*
8—1. INTRODUCTION
The reliability of equipment for handling radioactive fuel solutions and
suspensions 1s considerably more important in homogenecous than i heter-
ogeneous reactors becanse the residual radioactivity of such equipment
after shutdown of the reactor precludes direct maintenance. The possi-
bility of failures of individual components in a homogeneous reactor,
moreover, 1s considerably increased by the corrosive or erosive nature of
the media being handled and the temperature fluctuations encountered
during startup and shutdown operations. The technical feasibility of cir-
culating-fuel reactors is so dependent on the behavior and reliability of
mechanical components that there is little likelihood that large-seale plants
will be built before the performance of each piece of equipment has been
adequately demonstrated. In this regard, the development of satisfactory
valves, feed pumps, mechanical joints, and remote-maintenance equipment
for large-seale plants appears to be most difficult.
The component development work at ORNL has been directed primarily
toward equipment for use in the Homogeneous Reactor xperiment
(HRE-1) and the Homogeneous Reactor Test (IIRE-2). Although the
HRI-2 has both a core and a blanket, most of the components in these
two systems are identical and designed for use with solutions rather than
suspensions.
Since suspensions, or slurries, have not been used in either of the ho-
mogeneous reactors built by ORNL, the slurry equipment problems have
received less attention than corresponding solution problems. Much of
the solution technology can be applied to slurries, although additional
difficulties such as the settling tendency of slurries, their less ideal fluid-flow
behavior, and their erosiveness must be taken into consideration.
The following pages give descriptions and illustrations of the aqueous
reactor components which have been selected and developed for use at
ORNL.
*By 1. Spiewak, with contributions from R. D. Cheverton, C. . Gabbard,
E. C. Hise, C. G. Lawson, R. C. Robertson and D. 8. Toomb, Oak Ridge National
Laboratory.
408
8-2] PRIMARY-SYSTEM COMPONENTS 409
Alternate
Inlet Qutlet A
Frc. 8-1. Conceptual design of two-region reactor with slurry blanket. Arrows
indicate directions of slurry flow,
82, PrIMARY-SYsTEM COMPONENTS
8-2.1 Core and blanket vessel designs. Core hydrodynamies. TFlow
tests have been conducted on a variety of spherical vessels simulating
solution-reactor cores which have been selected to mcet the following
criteria;
(1) Heat removal from all points must be rapid and orderly to prevent
hot spots from being generated.
(2) Radiolytic gas formed from water decomposition cannot be per-
mitted to collect in the reactor.
(3) The pressure drop should be low.
(1) The core tank should be maintained at a low temperature to prevent
excessive corrosion rates.
Three geometries which satisfy the above requirements have been in-
vestigated. The first, straight-through [1], involves diffusing the inlet flow
through sereens or perforated plates [2] to achieve slug flow through the
sphere. The second, mixved [3], involves generating a great deal of turbu-
lence and mixing with the inlet jet so that the reactor is very nearly iso-
thermal. The third, rotational [4], is somewhat between the first two; the
fuel is introduced tangentially to the sphere and withdrawn at the center
of a vortex, at the north and south poles.
410 COMPONENT DEVELOPMENT [cHAP. 8
In the straight-through core, used in HRE-2, the flow enters upward
through a conical diffuser containing perforated plates. The number of
perforated plates is determined by the ratio of sphere diameter to inlet-pipe
diameter. In general, this ratio will be smaller for a larger reactor, resulting
in fewer plates and better performance. The velocity distribution leaving
the plates can be made to conform approximately to the flux distribution
of the reactor. As a result, the isotherms in the core are horizontal, and the
temperature rises smoothly toward the outlet at the top. The gas bubbles
rise upward at a velocity greater than that of the liquid and are removed
with the liquid. The over-all pressure drop is about 1.5 to 2.0 inlet-velocity
heads. The core tank is cooled by natural convection.
In the mixed core, illustrated in Tig. 81, the inlet and outlet are con-
centric at the top of the sphere. The inlet jet coincides with the vertical axis
of the sphere and 1s broken up when it hits the bottom surface. Tixeept for
the cold central jet, the bulk of the core is at outlet temperature. The
veloeity of eddies is great enough so that the gas bubbles travel along with
the liquid. The pressure drop is about 1.0 to 1.5 inlet-velocity heads.
The core-tank surface is maintained at a temperature very close to that
of the core fluid by the high turbulence.
In the rotational core, used in HRE-1, the flow pattern tends to produce
isotherms which are vertical cylinders. These are perturbed by boundary-
layer mixing at the sphere walls. The temperature generally inereases in
the direction of the central axis, which is at outlet temperature. The gas
bubbles are centrituged rapidly into a gas void which forms at the center
axis and from which gas can be removed. The gas void is quite stable 1n
cores up to about 2 ft in diameter, but in larger spheres the pumping re-
quirements to stabilize the void are excessive [5]. The pressure drop
through a rotational core is a function of the particular system, but is
usually above 5 inlet-velocity heads.
Slurry blanket hydrodynamics. The suspension contained in the blanket
vessel must be sufficiently well dispersed to assure that a maximum of the
core leakage neutrons are absorbed within the blanket, the neutron reflec-
tion from the blanket to the core remains steady, and the transport of
fluids through regions of high heat generation are sufficient for heat re-
moval. The primary flow is taken through a jet eductor where the flow rate
is amplified and forced through a spherical annulus containing the high
heat generation region surrounding the core. It appears that amplification
gains of 2.5 are attainable. The outlet may be located either (1) concentric
with the bottom inlet or (2) at the top. Configuration (1) has the advantage
of high circulation rates in the region outside the shroud. Configuration
(2) has the advantage of better natural circulation in the event of a cir-
culating-pump stoppage.
Also under consideration is a swirling flow pattern similar to the rota-
tional flow which was described under cores.
8-2] PRIMARY-SYSTEM COMPONENTS 411
Reactor pressure vessels. Three principal types of stresses should be con-
sidered in designing the pressure vessels of one- or two-region reactors:
(1) Stresses resulting from the confined pressure.
(2) Thermal stresses resulting from heat production, and consequent
temperature gradients in the metal.
(3) Stresses introduced by cladding if used. Because of the uncertain
residual stresses introduced during fabrication, this factor has not been
taken into account in the past.
The construction material can be chosen on the basis of corrosion re-
sistance and structural and thermal properties with little regard for nuclear
propertics. Carbon steel with a stainless-steel cladding was selected for
use in the HRE-2.
Usually the pressure-vessel wall is thin in comparison with the inner
radius of the vessel; the “thin-wall” formulas for calculating pressure
stressex are then applicable [6]. For precise calculations the general equa-
tions [7] for vessels with any wall thickness should be used. Thermal
stres=es are superposed on the pressure stresses and can be approximated
by conventional formulas for hollow eylinders and spheres [8].
Solution of the stress equations depends upon a knowledge of the radial
temperature distribution, which, in turn, depends upon the manner in
which heat Is generated in the metal wall and upon the temperatures at the
mner and outer surfaces. Ileat is produced in the metal by the following
Processes:
(11 The absorption of gamma rays arising from neutron capture, from
fiz<ion products, and from fission within the vessel.
(27 The recoil energy from the scattering of fast neutrons in the shell.
(31 The absorption of gamma rays produced by the inelastic scattering
of fust neutrons in the shell.
(4) The ubsorption of capture gamma rays produced as neutrons are
aptured in the shell.
Although 1t may be possible to obtain the heat-production function for
the desired cylindrical or spherical geometry, it is simpler and usually
sufliciently accurate to obtain the leakage fluxes of gnmma rays and neu-
trons mto the pressure shell for the desired geometry, and then to assume
that the heat-production function in the pressure vessel is the same as it
would be in a plate of the same material. Methods for obtaining the heat-
production function have been summarized by Alexander [9]. The function
can usuilly be deseribed by the sum and difference of several exponentials.
'or some purposes a single exponential can be used as a satisfactory ap-
proximation. The accuracy of the various methods has yet to be determined.
To arrive at a conservative design, reasonable methods indicating the
greatest amount of heat generation should be used. The surfuce tempera-
tures of the pressure vessel are estimated from o knowledge of the tem-
412 COMPONENT DEVELOPMENT [cHAP. 8
Core Access
-
= -
i % To Fuel
g Pressunizer
o
— M_M__ To Binnker
Bianket Outlet - ¢ | ilimanmtncts Pressurizer
X g -
e G
Fuel Outlet 4-.--“-*“*3
i
Expansion Joint
Blast Shield
Caore Vessel
Ditfuser Screens &
Cooling Coils
Pressure Vessel
Bianket
Iniet
Fic. 8-2. HRE-2 reactor vessel assembly, fabricated by Newport News Ship-
building & Dry Dock Company.
peratures of the adjacent fluids and the heat-transfer relationships between
metal and fluids.
Chapman [10] has shown in an analysis of thermal stresses in spherical
reactor vessels that minimum thermal stresses are obtained when the
inner and outer vessel wall temperatures are approximately equal. Pressure
stresses decrease and thermal stresses increase as shell thickness is increased ;
a minimum combined stress occurs at an optimum wall thickness. Often
this stress is greater than the permissible design stress; thermal shielding
must then be provided between the reactor and pressure vessel to reduce
heat production and obtain a reasonable stress.
HRE-2 core and pressure vessel. The HRE-2 reactor-vessel assembly
presented a number of special design and fabrication problems [11].
Since it was desired to minimize neutron losses, Zircaloy—2 was selected as
material for the core tank, which is 32 in. in diameter and 5/16 in. thick.
The main pressure vessel, 60 in. in inside diameter and 4.4 in. thick, was
constructed of carbon steel with a cladding of type—347 stainless steel.
Because of uncertainties in the long-term irradiation damage of carbon
8-2] PRIMARY-SYSTEM COMPONENTS 413
steel, the pressure vessel was surrounded by a stainless-steel, water-
cooled blast shield which will stop any possible missiles from the reactor
vessel. Thermal radiation from the pressure vessel to the blast shield
permits the pressure vessel to operate at close to an optimum temperature
distribution from the thermal-stress standpoint.
A special mechanical Joint was developed to join the Zircaloy core tank
to the stainless-steel piping system. A bellows expansion joint was used
to permit differential thermal expansion between core and pressure vessel.
Welding procedures were developed for joining Zirealoy and for making
the final girth weld in the clad pressure vessel entirely from the outside.
The HRIE-2 core and pressure vessel are illustrated in I'ig. 8-2.
8-2.2 Circulating pumps.* Pumps are required in aqueous homogeneous
reactors to circulate solutions and slurries at 250 to 300°C and 2000 psi
pressure, at heads of up to 100 psi. The two main considerations for these
pumps are that they must be absolutely leak free and that they must have
a long maintenance-iree life.
At this time the only pumps considered capable of meeting these require-
ments are of the hermetically sealed canned-motor centrifugal type.
They consist of a centrifugal pump of standard hydraulie design and an
electric drive motor, built in an integral unit.
To illustrate, the 400A pump used to circulate fuel solution in the HRE-2
is shown in I'ig. 8-3. The HRII-2 blanket pump is identical except for
having a lower-output impeller. The hydraulic end of the pump is separated
from the motor by the thermal barrier, which 1s used to restrict the transfer
of heat and fluid from the seroll into the motor section of the pump. This
minimizes thermal and radiation damage to bearings and motor insulation.
The thermal barrier 1s built with sealed air spaces which aid in thermal
insulation. A labyrinth seal around the shaft is used to reduce the fuel
mixing into the motor. Water-lubricated hydrodynamic journal bearings
and pivoted-shoe-type thrust bearings are used to tuke the radial and
thrust loads, respectively. In the HRE-2, contact of the motor and
bearings with radioactive solutions is minimized by feeding distilled water
continuously into the motor.
The electrie drive is a three-phase squirrel-cage inducetion motor with the
stator and rotor sealed in thin stainless-steel cans which prevent the
process fluid from coming in contact with the stator or rotor windings.
The cans are supported by the laminations to contain the system pressure
of 2000 psi. The motor is enclosed in a heavy pressure vessel which is
designed to hold the full system pressure in the event of a can failure.
The motor and bearings are cooled by the use of a small auxiliary impeller,
*Prepared from material submitted by C. H. Gabbard.
414 COMPONENT DEVELOPMENT [cHAP. 8
mounted on the rotor shaft, which recirculates motor fluid through a heat
exchanger.
In the IHRE-2, it is usually desirable to run the fuel pump at reduced
apneity during startups in order to limit reactivity changes. This is
accomplished by starting the 400A pump in reverse, which gives about one-
half of the normal flow. The ubility to do this depends on the design of the
impeller and the size of the pump. In larger pumps, it is considered better
to use a two-speed motor to obtain the reduced-capacity operation. The
two-speed motor hag an additional advantage in permitting the system to
be heated to operating density at reduced speed, thereby reducing the
required motor size and power consumption.
The service life of the 400A pump, based on out-of-pile tests with solu-
tions, is expected to be two years or more [12]. The slurry pumps currently
being operated have not proved as reliable as the solution pumps, but ruus
of up to 3800 hr have been obtained [13]. The hydraulic parts of the pump
are frequently severely eroded, but there has not been a significant change
in the pump output or power requirements during the runs. The pumps
will generally continue to run unless a bearing seizes or brenks down. It
is expected that improvements in bearings and hydraulic design will make
slurry pumps as reliable ag solution pumps.
The important problems in solution and slurry cireulating pumps are
discussed below.
Stators. Pumps have been built with oil-filled stators to improve heat
removal from the windings and to balance the pressure across the stator
:an. These pumps are undesirable for long-term reactor service because
the oil ig subject to radiation damage and requires frequent replacement.
Pressure-balanced stator cans have also proved to be unsatisfactory
because of the difficulty in maintaining the proper balance. In pumps of
up to 100-gpm capacity, the problem of cooling the stator windings does
not seem too severe, and the dry-stator design with the can capable of
withstanding the full 2000-psi system pressure seems to be the best and most
commonly used type. In larger pumps, manufacturers are tending to use
a compound of silicone resin and inert filler material to improve heat re-
moval from the windings.
Most manufacturers insulate their motors with class T insulation con-
sisting of I'iberglas cloth impregnated with a silicone varnish binder. This
insulation is probably good for several years’ operation in circulating-
fuel reactors, depending on the radiation level of the pump, but over a
period of time the insulation can be expected to fail because of the decrease
in resistivity and dielectric strength. Hydrogen, released from the silicone
varnish during irradiation, may also build up enough pressure to rupture
the stator ean when the system pressure is reduced. The HRE-2 1s expected
to yield much information on motor life. EKstimates made for the fuel
8-2] PRIMARY-SYSTEM COMPONENTS 415
Purge Water
Seal Weld | Inlet
[ -5 ~+— Conduit Box
i | i
SONE A e
/5 o T Upper Radllol Bearing
b |
B
|
i
i |
| ! !
Eg —— Coola .t Impeller
i o
Cooling Coil =
OO0
Stator Lamination
«+— Rotor
LY
= ¢ Thrust Bearing
Lower Radial Bearing
W o o
Seal Weld ey
Shaf: Labyrinth Secl\‘!
Upper Wear Ring
Thermal Barrier “FE-Balance Ports
Seal Weld
Impeller
Thermal Barrier %5
Casing Wear Ring
|
\1 —— e
]
Dif’ruser Q J
Fra. 8-3. The Westinghouse 400A pump used to circulate fuel solution through
the HRE-2.
circulating pump of the HRE-2 indicated that the insulation will be sub-
ject to failure in approximately five years, assuming that the outside of the
motor is protected by a 1-in. lead shield and the inside of the motor is
kept purged free of fuel solution [14]. Tests are being initiated at the
present time to determine the life expectancy more closely by irradiating
stators in gamma and gamma-neutron fields.
The ultimate solution to the insulation problem is probably the use of
ceramic insulation that would be completely radiation resistant. However,
considerably more development work will be required before this type of
insulation becomes usable. There are data available which indicate that
silicone-resin-bonded reconstituted mica (Isomica, trademark name of
Mica Insulator Co.) may have better radiation resistance than Fiberglas
and silicone varnish. If this material proves to be better from a radiation-
damage standpoint, it can probably be incorporated into a pump at a much
earlier date than the ceramic insulation.
416 COMPONENT DEVELOPMENT [cuaP. 8
Bearings. The standard Stellite-vs-Goraphitar hydrodynamic bearings
have indicated little or no wear in pressurized-water systems. Presumably
their performance in aqueous homogencous systems would be comparable
if the motor ean could be kept in contact with the water only. In practice,
bearing life of 13,0004 hr has been achieved in actual contact with uranyl
sulfate solutions; however, continuons wear wus observed, indicating that
eventually the bearing surfaces will fuil,
Laboratory tests inowater and tests on small pumps in solutions have
shown that aluminum oxide bearings and journals have superior wear
resistance as compared with the Stellite-vs-Graphitar combination. TIf
service tests conducted on larger pumps are successful, the aluminum
oxide bearings will be adopted as standard in solution pumps.
There 1s some doubt whether the hyvdrodynamie-type bearings currently
being used will be suitable for long-life slurry pumps. There have been very
few runs completed in which the bearings were not badly worn. IHowever,
prelimmary tests of small pumps with aluminum oxide bearings have
shown promize. It 1= planned, also, to evaluate the performance of hydro-
statie (pressurized-flnd) bearings i dilute slurries.
In ome cases, excessive wear has occurred in the thrust-bearing leveling
linkages of the 400 A-type solution and slurry pumps. In this bearing the
thrust load is supported by a linkage system which used 1/8- and 1/4-1n.-
diameter pins to transfer the load {from link to link. It is uncertain whether
this wear at the contact pomt is caused by high stresses or by fretting cor-
rosion, .\ thrust bearing with line-contact linkages and alternate materials
at the contact points will be evaluated inan attempt to correct this problem.
Huydraulic parts. In uranyl sulfate pumps, excellent wear resistance 1s
obtained by using titanium for impellers, wear rings, and diffusers.
Stainless-steel hydraulic parts have also been used successfully in many
cases [15], ’
The general design of slurry pumps 1s similar to that used for uranyl
sulfate pumps. The properties of the slurry ave such that only a power
correction for the higher specific gravity is necessary in the hydraulie
design of the impeller. The coeflicient of rigidity (viscosity) is generally
not high enough to require 2 correction to the head-capacity curve. A
most severe problem n slurry pumps is the combination of corrosive and
erosive attack on the hydraulic parts.
The primary difference m the design of a slurry impeller 12 the use of
radial balancing ribs on the top impeller shroud i place of the top wear
ring on a conventional pump. In a conventional pump (Fig. 8-3) there
are small holes which vent the area within the top wear ring to the pump
suction pressure. This is done to balance some of the hydraulic thrust and
therefore reduce the loud on the thrust bearing. In certain cases these
balancing holes have become plugged with slurry [16], which upsets the
8-2] PRIMARY-SYSTEM COMPONENTS 417
thrust balance and causes high thrust-bearing wear. The balancing vanes
eliminate one set of wear rings, which are subject to high attack rates,
and also tend to centrifuge the slurry particles to the outside, which aids
in preventing the slurry from entering the motor through the labyrinth
seal.
On the pumps currently in use, the damage to hydraulic parts is usually
limited to the wear rings, the tips of the impeller vanes, and to the volute
“cut water,”” which 1s the point adjacent to the pump discharge where the
volute curve starts. The attack at these points can be reduced by proper
material choice and by using proper design of the flow passages. The best
materials which have been found for the hydraulic parts are Zircaloy—2 and
titanium, with Zirealoy being better in laboratory corrosion tests. There are
no test results for pumps using Zircaloy parts at this time, but vacuum-
-ast parts have been obtained and placed into service. Other materials are
to be given laboratory corrosion tests, and promising materials will be
service tested.
The wear rings of the present pumps are being redesigned to provide
smooth throttling surfaces rather than the serrated type presently in use.
The smooth surfaces should reduce the turbulence and corrosion consider-
ably, with a very small increase in flow through the rings. One service test
has shown that the damage to this type of wear ring is decrcased con-
siderably [17]. A test 1s being planned to determine whether radial vanes
on the lower impeller shroud similar to the balancing vanes discussed
arlier will reduce the attack rate on the lower wear rings. The radial
vanes will reduce the pressure drop across the wear rings and may reduce
the concentration of slurry flowing through them by centrifugal action,
It is uncertain whether a volute type seroll or a diffuser type seroll is
preferable. The volute type scroll has the advantage of having only the
cut-water subject to high attack, but has the disadvantage of having a
pressure drop across this point, resulting in perpendicular flow across the
cut-water. The diffuser has numerous points which could be eroded, but
the flow around these points should be smoother than that at the cut-water
and may not cause excessive damage.
The surface finish on the hydraulic parts is also very eritical and the
surface variation should be held to 65 microinches or less, This is especially
evident at areas where the impeller surfaces have been ground during the
dynamic-balancing operation. If these areas are not properly finished,
the seratches will be severely attacked.
Thermal barriers. In pressurized-water pumps, the primary function
of the thermal barrier 1s to retard the transmission of heat mto the motor,
In solution and slurry pumps, another function, that of preventing fluid
mixing from pump to motor, is of eritical importance.
This mixing can occur at two places, at the shaft seal and around the
418 COMPONENT DEVELOPMENT [cHAP. 8
Coolant Impelier
L \\—777‘#L
2 ‘
_ _“Upper Radial Bearing
Stator Cooling Coil :
_— Stator Laminations
and Windings
| © . Rotor Assembly
7f313/16in.
33-in. Dig—~—/——
N
Belleville Spring To Load 7 _.._»..‘A
Ring Joint Gasket
Lower Radial Becrlng
Permanent Seal Weld
Shofi Lébyrlnth i
Seal b
Thermal Barrier
Ring Joint Gasket
Passage to Pump
Suction Pressure
Throttling Surfaces
Upper Wear Ring
Diffuser
Lower Wear Ring
7 Part of Pump Permanently
installed In Piping System
Fic. 8-4. 6000-gpm top-maintenance pump for circulating solutions through a
50-Mw reactor, being built by Reliance Electric Company.
outer edge of the barrier. In the 400A pump, the mixing rate at the shaft
labyrinth seal has been reduced to 3 cc/hr by redesign of the seal and by
the use of a 5-gph purge flow through the motor [18]. IFurther improve-
ments in shaft seals are being attempted.
The seal around the outer edge of the 400A thermal barrier was originally
a mechanical joint, with the head developed by the pump across it. The
purge system did not develop enough pressure to prevent solution leakage
8-2] PRIMARY-SYSTEM COMPONENTS 419
through this joint into the motor. Any small leak was rapidly enlarged
by corrosion until excessive motor temperatures were reached. The prob-
lem was solved by seal-welding the joint. However, it would have been
preferable if the joint had originally been designed for welding.
Pump closures. Conventional canned-rotor pumps, such as those used
in the HRIZ-2, have a large seal-welded closure at the bottom of the stator.
Dismantling this closure for pump maintenance is impractical at the
present time because of the extremely high level of radiation at the
closure,
I'rom a maintenance standpoint, a “top-maintenance” pump appears
to be advantageous. Direct-maintenance practices can be used to bolt and
unbolt the main flange. The pump casing is a permanent part of the
piping system. A top-maintenance pump being developed for the HRI2-3
is illustrated in T'ig. 8-4.
In a top-maintenance pump, a mechanical thermal-barrier joint cannot
be avoided, since the barrier must be removable from the casing. The
joint must be loaded using the top closure bolts, and the entire mechanical
system must have some flexibility to compensate for differential thermal
expansion of the long motor. A venting system, shown in Fig. 8-4, 1s used
to eliminate the pressure drop across the thermal-barrier gasket so that
there will not be significant leakage even if the joint is not perfectly tight.
In this case, the purge flow should be effective in preventing leakage of
process fluid into the motor.
8-2.3 Steam generators. The performance of steam generators required
for homogeneous reactor service, measured in terms of undetectable leak-
tightness during long-term operation, considerably excecds that of similar
units in conventional plants. Unfortunately, no method has yet been
developed of remotely locating and repairing leaks in a radioactive heat
exchanger without removing the entire unit. L'ailure of the steam generator
in a homogeneous power reactor, therefore, would lead to excessive shut-
down time and must be avoided if at all possible.
HRE-2 steam generators. The heat exchangers used in the HRIE-2,
shown in Fig. 8-5, place reliance on the careful welding and inspecting
of tube-to-tube-sheet joints and the extensive thermal-cycle tests which
were carried out prior to actual operation in the reactor. In addition,
thermal gradients which would lead to excessive stresses during reactor
startup and shutdown are held within specified limits. Although the
units fabricated for HHRIZ-2 have been tested with the most advanced
inspection methods available for both materials and workmanship and have
met initial leaktightness specifications, only through operation of the
reactor will it be possible to judge the adequacy of these precautions.
The characteristics of the HRE-2 steam generators, which were manu-
420 COMPONENT DEVELOPMENT [caap. 8
TasLE 8-1
DgrsigN Data ror THE HRE-2 HeEaT EXCHANGER
Shell side Tube side
Circulation rate, Ib/hr 1.62 x 104 1.79 x 10°
Temperature in, °F 180 572
Temperature out, °F 471 494.5
Operating pressure, psia 520 2000
Veloeity, fps 67 (in outlet pipe) 11.3
Pressure drop, psi 18.5
Heat exchanged, kw 5000 (1.71 x 107 Btu/hr)
Fouled Uy, Btu/(hr)(ft2)(°F) 670 (based on Up = 3/4 Ug)
Heat-transfer area, ft? 480
Tube outside diameter, in. 0.375
factured by the Foster Wheeler Company, are summarized in Table 8-1.
In fabricating these steam generators, all-welded construction was used on
components that were to be exposed to the process solution. Interpass
leakage 1s controlled by use of a gold gasket. Considerable attention was
given to obtalning the highest quality tubing, which was inspected by
ultrasonic and magnetic flaw detectors capable of detecting imperfections
as small as 0.002 in. Following the bending and annecaling operations,
each tube was inspected for surface defects with a liquid penetrant and
subjected to a 4000-psi hydrostatic test. After passing all these tests, the
tubes were rolled into the tube sheet and welded by an inert-gas-shielded
tungsten-arc process. Quality-control welds were made periodically during
the tube-joint welding and were subsequently examined by radiographic
and metallographic methods,
After fabrication, the units were subjected to 50 primary-side thermal
cycles covering temperature changes more severe than those likely to be
encountered in subsequent operation. The units were then helium-leak-
tested at atmospheric pressure with mass-spectrometer equipment capable
of detecting leakage lower than 0.1 ce of helium at STP per day. Leaks
were repaired and the thermal-cyele test and leak test were repeated until
no leakage was detectable.
The HRE-2 steam generators were thermal cyecled with diphenyl as the
heating medium. After the test, extensive carbon deposits were found in
the tubes. After considerable difficulty, the deposits were removed by
high-temperature flushing with oxygenated water and uranyl sulfate solu-
tion. Future thermal-cycle tests will be made with steam as the heating
medium.
Steam Steam }
To Safety Valve ' L — . Tap For Pressure
oo MR Indicator
Leak Detector
.
Y
Feed - Water '
Inlet t%::mfi
Seal Weld -~
T
~_.#"Support Plate
3ft 3% in. wmm——
— Fuel In
7
s
/7 Tliguid-Level
"3
Gasket
Drain Blowdown
: Line
Stainless-Steel-Clad
Carbon Steel
13 ft 6Vain,
Fic. 8-5. The HRE-2 main heat exchanger, fabricated by Foster-Wheeler Corporation.
[2-8
SLNANOdAWOD WHILSAS-AYVIIUL
1ev
422 COMPONENT DEVELOPMENT [cHAP. 8
Level Control Water
Connection Thermal Level
tnsulation
Biast Shieid
— Inlet
o -
Feedwater - 2 - . Header
Iniet R e TR
— i ——
t = II"‘E —
F\ % in. OD Tubes
P
:
Vi i
N ‘\ g 7 -
V P ;
Sy e - -
i <
- - T
RS SEETE
Outlet
Blowdown Header
Level Control Thermal
Connections Sleeves
F1c. 8-6. The HRE-2 spare heat exchanger, fabricated by Babcock & Wilcox
Company.
The tube-to-tube-sheet joint is the most damage-sensitive portion of the
steam generator. The primary side is subject to corrosive fuels, and the
secondary side is subject to crevice corrosion and stress-corrosion ecracking.
Primary-side corrosion is controlled satisfactorily by maintaining velocities
below 15 fps and minimizing high-velocity turbulence in the headers.
Secondary-side corrosion is limited by strict control of boiler-water chem-
istry, particularly chloride content. One method which has been proposed
for eliminating the stress-corrosion problem is the use of composite tubing
such as stainless steel-Inconel, where the two materials are exposed only
to fuel solution and boiler water, respectively.
Another problem in the operation of steam generators in a radioactive
environment is the generation of radiolytic oxygen in the boiler water.
This oxygen is stripped very rapidly by the steam, which contains about
2 ppm of oxygen. Hydrogen is released at the same time. The corrosivity
of this mixture is not yet known, but it can be controlled by the use of
inhibitors and by proper selection of materials for use in thin metal sections
where pitting attack is undesirable.
HRE-2 spare steam generator. The steam generator shown in Fig. 8-6
was constructed as a possible replacement in case of failure of an HRE-2
steam generator. Although the over-all geometry of this unit, fabricated
by the Babcock & Wilcox Company, conforms to the space requirements of
the present steam generators, the design was changed to minimize the
possibility of stress-corrosion cracking of the tubes on the shell side by
eliminating crevices in contact with boiler water.
The steam generator contains eighty-eight 5/8-in.-OD, 0.095-in.-thick,
type—347 stainless-steel tubes. The tubes have multiple U-bends to provide
8-2] PRIMARY-SYSTEM COMPONENTS 423
the required length for heat-transfer surface. KEach tube is brought out
through the shell of the exchanger, and then all the tubes are collected in
the inlet and outlet headers. Thermal sleeves are utilized at every con-
nection of the stainless tubes to the carbon-steel shell wall. Their function
is to prevent high thermal stresses in the tubes by distributing the tem-
perature gradient between shell and tubes along the length of the thermal
sleeves. The normal erevice between tubes and tube sheet, which is the
site of possible corrosion failures, is eliminated. Each sleeve consists of an
austenitic type—347 stainless-steel section which is welded to the tube on
one end and to a carbon-steel section of the sleeve on the other. The
carbon-steel sleeve is then welded to the carbon-steel shell to scal the
secondary side. Only austenitic type—3147 stainless steel is exposed to fuel
solution.
Slurry steam generators. The mechanical design of heat exchangers for
slurry service should not differ greatly from that for solution service.
However, the design must assure that
(1) The pressure drop across all tubes is sufficient to maintain the slurry
In suspension.
(2) The headers have no stagnant regions where sediment can accumu-
late.
(3) The tube-sheet joints are sufficiently smooth to prevent fretting
corrosion by the slurry.
(4) The headers and tubes drain freely.
From the heat-transfer relationships for Bingham plastic slurries,
described in Article 4-4.5, it is evident that for optimum design of steam
generators the flow of slurry through the tubes should be turbulent.
Large heat exchangers. The Foster Wheeler Corporation has prepared
preliminary designs of 50- and 300-Mw heat exchangers [19]. Both single-
drum integral units and units with separate steam drums were considered
in the 50-Mw size; only two-drum units were considered in the 300-Mw
size. Two-drum units, in gencral, give operational characteristics superior
to those of integral units, but requirc more shielded volume and reactor
space for installation. The two-drum unit has more stable steam generation
at power and provides greater assurance of high steam quality. The major
problems introduced by increasing size are higher tube-sheet thermal
stress and increased difficulty in the manufacture of large forgings.
The 50-Mw design employs approximately 2200 tubes 3/8 in. in diameter
(5960 ft2 of heat-transfer area); the 300-Mw design uses approximately
11,400 tubes of the same size (32,000 ft2). Most of the designs have stainless
steel clad on steel for tube sheets and heads, and steel for steam shells.
8-2.4 Pressurizers. A pressurizer is required in an acqueous fuel system
to provide (1) sufficiently high pressures to reduce bubble formation and
424 COMPONENT DEVELOPMENT [crAP. 8
cavitation in the ecirculating stream, (2) reactor safety by limiting the
pressure rise accompanying a sudden inerease in reactivity, and (3) a surge
chamber for relief of volume changes.
Three general methods of pressurizing have been used in test loops
and experimental reactors:
(1) Steam pressurization, such as is used in the HRF-2, where liquid
in the pressurizer is maintained at a higher temperature, hence a higher
vapor pressure, than that of the circulating system.
(2) Gas pressurization, where liquid in the pressurizer is at the same
temperature as the eirculating system but excess gas is added to the vapor
above it; if the pressurizing gas is free to diffuse into the cireulating liquid,
it reduces the solubility of radiolytic deuterium and enhances bubble
formation.
(3) Mechanical pressurization, where pressure is maintained with a
pump and relief valve; this system is most satisfactory except that it is
difficult to relicve sudden large volume changes following a reactivity
change. This system therefore has been limited to nonnuclear test loops.
Solution pressurizers. Solution steam pressurizers must satisfy rather
strict chemical criteria. Stainless-steel surfaces in contact with solutions
must not exceed temperatures at which heavy-liquid-phase solutions form,
giving rise to rapid corrosion [20]. Undesirable reduction of uranium must
be avoided by the presence of some dissolved oxygen. Undesirable hydroly-
sis of uranyl ion must be avoided by control of the chemistry and tem-
perature in pressurizer solutions [21]. The vapor-phase concentration of
deuterium should be maintained below the explosive limit. One solution
to these problems, used in the HRE-2, is the generation of steam from dis-
tilled water rather than from fuel solution. Another solution is the boiling
of solutions in corrosion-resistant titanium. A third solution is the use of
fission-product heating rather than external heating to reach the desired
temperature.
Gas pressurizers using Oy gas are attractive from the solution-stability
standpoint. Care must be exercised to prevent excessive amounts of dis-
solved oxygen appearing as bubbles in the circulating reactor stream. This
can be accomplished either by continuous letdown of fuel solution or by
use of a mixed steam-gas pressurizer where gas supplies only a portion of
the desired overpressure.
Heat may be supplied to pressurizers by several methods. Electrical
heating of pipes, used in the HRE-2 is very convenient but makes con-
trol of surface temperature difficult. Heating media such as steam, Dow-
therm, liquid metals, ete., simplify the temperature-control problem but
introduce costly auxiliaries. Fission-product heating is simple but rather
difficult to regulate. Since the heating problem is so complex, selection of
an optimum system for a specific application is quite difficult.
8-2] PRIMARY-SYSTEM COMPONENTS 425
Purge
Water Level
. Steam Baffle
Dry Pipe
Thermocouple Surge Pipe
Well Vent - % / Drain Pipe
-\ v i T Fd 7 //K
Al | T S A 28
- —l— 7=
F
& ‘B E 5l L
H
Fuel I ‘ :
Solution Level ‘ .| Purge Water
Overflow
i ; !
1 ! i
To Reactor ‘ :
System ™
%L F e
Downcomer fi Electric
Lower Header Heater
Purge Water
Inlet
Fia. 8-7. HRE-2 pressurizer.
Deuterium concentration may be controlled by designing the pressurizer
in a manner which makes buildup of gas improbable, by contacting the
vapor with solid or solution catalyst, or by venting.
HRE-2 pressurizer. Several design configurations were studied for
steam-pressurizing the HRE-2 core system [22]. Both an integral type
unit (Fig. 8-7) incorporating a steam generator and fuel surge volume
within the same vessel, and a two-unit system utilizing separate steam-
generator and surge-volume vessels were considered. The basis of both
systems was the vaporization of a stream of “clean” purge water, pumped
from the reactor low-pressure system, to obtain the required steam over-
pressure.
The integral unit was chosen because of its simpler design and its ability
to maintain a very low dissolved-solids concentration in the boiling water.
Approximately 609, of the purge water overflows and 409, is vaporized.
In determining the internal configuration of the unit, it was necessary
to establish a second basic design criterion. Owing to the nature of the
system selected, continuous operation of the purge pump is essential to
maintaining steam overpressure. Since this type of pump may fail, it was
decided that sufficient water should be stored in the steam generator to
maintain full operating pressure for at least 1 hr after a purge-pump failure.
This appeared to be adequate time for either emergency repair of faults
on the oil side of the purge-pump system or arrangement of an orderly
shutdown.
426 COMPONENT DEVELOPMENT [cHAP. 8
Y
" Yapor
Antivortex
" Baffles
H Liquid
e Water flt‘-
Jet
Cast e Eductor
Electric | _
Heater \ Antivortex
Baffles
= :v /Slurry f
Optional
Nozzle ——
(a) {b)
Steam Vapor
Dowtherm
Heater
Steam Separator
Solution | .aal
N
Cooler R
Fuel Storage Tank —
{el
Fic. 8-8. Typical pressurizers. (a) Slurry steam or gas pressurizer. (b) Solution
or slurry gas pressurizer. (c) Boiling-solution pressurizer.
A general description of the basic design and system operation follows:
The low-pressure condensate, pumped to loop operating pressure by a
diaphragm pump, passes through the letdown heat exchanger, where it is
preheated to about 280°C and then enters the lower header of the steam
generator, as shown in Fig. 8-7. Clamshell heaters are attached to four
pipes inclined upward at 55 deg. Heat-load calculations indicate that
32 kw are required under rapid-startup load conditions; however, at steady
state the heat load becomes 12.4 kw. Part of the purge water entering the
heater legs (40 Ib/hr) is vaporized to provide the desired steam overpres-
sure. The remainder enters a storage pool in the main pressurizer drum.
Natural recirculation of this water oceurs through two downcomers.
The storage-pool level is maintained constant by allowing excess purge
water to be removed through a series of 1/8-in. orifice holes located in the
end plate of the steam generator. A 1/2-in. hole centered 5/8 in. above
the orifice holes is provided as an overflow in case the orifice holes become
plugged. A method of increasing the surge volume, without changing the
8-2] PRIMARY-SYSTEM COMPONENTS 427
storage pool level, is to insert a pipe from the surge chamber through the
storage pool.
A single pipe connects the pressurizer surge chamber to the main core
loop. Liquid level in this pipe 1s maintained at a point about 10 in. below
the inside diameter of the pressurizer drum by a liquid-level controller.
The clamshell heaters are carefully machined to fit the heater pipes and
strongly clamped to promote contact. There are eight separate Calrod
heaters in each clamshell, so that failure of a few heater elements will not
affect the pressurizer greatly.
Vapor-phase deuterium is kept under control in that during normal
operation it has no way to enter the pressurizer. If a small amount of gas
does enter the pressurizer it will be dissolved in purge water overflowing
into the reactor system. A large amount of gas would be vented.
Slurry pressurizers. The physical problems of slurry pressurizers are
similar to those of solution pressurizers. The chemical problems are fortu-
nately not present. The pressurizer may be designed to promote settling
of solids so that pure supernatant water is available as a working fluid. It
is necessary, however, that the pressurizer be designed to prevent accumu-
lation of cakes or sludges. This is usually accomplished by flowing all or
part of the circulating stream through the bottom of the pressurizer. This
must be done carefully in steam pressurizers to prevent mixing of cool
circulating fluid with the heated pressurizer fluid above.
Typuical pressurizer designs. Several pressurizer designs applicable to
test systems or reactors are illustrated in Fig. 8-8.
In the slurry steam or gas pressurizer (a) slurry at circulating temperature
sweeps the bottom of the pressurizer tank, preventing the formation of
cakes. Two nozzle arrangements are shown. The baffles are used to mini-
mize turbulence and mixing in the system.
In the solution or slurry gas pressurizer (b) a jet is used to contact fucl,
which contains a liquid-phase catalyst, with pressurizer vapor. This main-
tains the vapor at a low Ds concentration. The high-velocity regions in
this system should be constructed of special wear-resistant inserts such as
titanium or zirconium.
The boiling-solution pressurizer (¢) has a fuel storage tank where solution
Just out of the reactor is heated by its own fission-product decay and
dissolved D32 recombines nearly quantitatively, Additional heating is
supplied, 1f necessary, by condensing Dowtherm. The mixture of steam
and fuel solution is separated; the steam flows into the pressurizer and the
fuel 1s cooled to a chemically acceptable temperature before re-entering the
circulating system. The fuel storage tank, Dowtherm heater, steam sepa-
rator, and solution cooler are made of titanium. High-strength alloy
T1-110-AT is preferred to commercially pure titanium in order to increase
the strength of these parts.
428 COMPONENT DEVELOPMENT [cHAP. 8
8-2.5 Piping and welded joints. The various codes [23] dealing with
pressure piping have proved very satisfuctory for determining the strength
required for reactor piping. Pipes are sized on the basis of experimentally
determined maximum veloeities for low corrosion and/or erosion rates.
The austenitie stainless steels are used for most piping applications.
Beeause of the fact that the piping system of & homogeneous reactor must
be absolutely leaktight throughout its service life, care is exercised in
selecting pipe of the highest obtainable quality. The chemical composition
and corrosion resistance are checked. Rigid cleanliness is maintained during
fabrication to prevent undesirable contaminants.
The design of solution piping systems must eliminate stagnant lines
where oxygen depletion may cause solution instability and plugging.
Slurry piping systems should be designed to prevent settling, which can
cause plugging or make decontamination very difficult.
Piping layouts. In laying out the piping system for an aqueous-fuel
homogeneous reactor, sufficient flexibility must be incorporated in the
system to absorb thermal expansions without creating excessive stresses
in the pipe wall, and to avoid high nozzle reaction loads at the equipment.
Equipment must be located where it will be accessible for maintenance,
and the piping adjacent to such equipment must be placed so that it can
be disconnected and reassembled remotely. These requirements may
result in a piping system of excessive length with resultant high fluid
holdup and pressure drop. The final design, therefore, must be a com-
promise between the various conflicting requirements of flexibility, main-
tenance, holdup, and pressure loss in the line.
Methods of piping analysis and evaluation as presented by Hanson and
Jahsman [24] may be used for analyzing the piping layouts in homogeneous
reactor systems. An application of the Kellogg method [25] was used by
Lundin [26] to analyze stresses in the HRE-2 system. Specific rules on
how to absorb the effects of thermal expansion of a piping system by the
provision of a flexible layout are given in the Code for Pressure Piping,
ASA B31.1-1942, Sec. 6.
Welded joints. Welded joints are recommended in preference to mechani-
cal joints for reactor piping. Welds are made approximately equal in
strength and corrosion resistance to the base metal. Pipe and fittings are
designed to utilize full-penetration butt welds throughout the piping sys-
tem. Welds that are to contact process fluids are inspected thoroughly to
ensure that no crevices are present and that penetration is complete. Such
defects could result in crevice corrosion leading to leaks.
The first 1/8 in. on the process side is deposited by use of bare-wire filler
metal and inert tungsten-arc welding techniques. The ferrite content of
the deposit is controlled to minimize the possibility of cracking. This de-
posit is inspected visually and with penetrant. If the weld thus far contains
8-2] PRIMARY-SYSTEM COMPONENTS 429
Carbon
Steel Bolts
Al
o;”/ T2
” g ”/’/‘
I’l
\\\
Leak Detection
Assembly
{Autoclave Fittings)
Fic. 8-9. HRE-2 ring-joint flange, showing leak-detector connection.
no visible defects, it is radiographed to ensure freedom from all defects.
The balance of the weld is then deposited from either bare or coated wire.
The completed weld is inspected again with dye penetrant and radiography.
A small number of inclusions or porosity are permitted in the final layers
which contact air.
Although welding techniques for clean piping are very satisfactory,
remote-welding procedures for repair of contaminated reactor systems are
only in the development stage. It is desirable to develop methods for
remote cutting, positioning, welding, and inspection of joints, particularly
in large pipes. Possession of these techniques would greatly increase the
maintainability of circulating-fuel reactors.
8-2.6 Flange closures. Piping flanges. Because a practical machine for
remotely rewelding pipe has not yet been developed, equipment which
must be removable from the system for replacement or maintenance must
be connected to the system with mechanical joints. Several types of
mechanical joints applicable to pressure systems have been described in
the literature, but most have been eliminated from consideration for ho-
mogeneous reactor service because their reliability with respect to leak-
tightness following thermal cycling has not been adequately demonstrated.
The ring-joint flange (Fig. 8-9) incorporating American Standard
430 COMPONENT DEVELOPMENT [cHAP. 8
welding-neck flanges and ring-joint gaskets, as described in ASA Standard
B16.20-1956, was used in the HRE-2 and is considered to be the most
reliable elosure for reactor piping systems to date. Since there are two
sealing surfaces in this type of joint, it 1s ideal for leak-detector purge
systems, described below, which prevent even minute leakage of con-
taminated fluids into the shield.
To enforce proper dimensions for HRIE-2 gaskets and grooves, special
master rings and grooves were manufactured to measure dimensions to
4+0.0001 in. Although ASA tolerances of +0.006 in. on pitch diameter are
acceplable, it was convenient to obtain manufacturing tolerances of
40.001 in. by using these gages and masters. The application of these
tolerances has permitted greater accuracy in fit-up and assures uniform
contact between the ring-joint gasket and the grooves of both mating
flanges. Soft oval or octagonal type—301 ELC stainless-steel rings are used
against the harder type—317 stainless-steel grooves. Typical leakage ex-
perienced in a 4-in. 2500-1b flange is 6 X 1077 g of water per day at service
conditions,
The bolting of flanged joints presents a serious problem because the
bolts, under thermal eycling, loosen up after only a very few cycles, thus
threatening the integrity of the joint. Whereas the flange bolts of a con-
ventional pressure piping system may be retightened after a few cycles,
this becomes impractical in a homogeneous reactor system after the reactor
has gone eritical. In the HRE-2 it was found desirable to initially stress
the low-alloy steel flange bolts to an average loading of 45,000 psi, as
indicated by a torque wrench. After about three thermal cyeles this bolt
loading fell to an asymptotic value of approximately 30,000 psi, which was
found to be adequate to maintain the integrity of the joint indefinitely
throughout further operations; no retightening of the bolts was found to
be necessary [27]. Some deformation of flange grooves and ring-joint
gaskets was found as a result of these high loadings. However, with the
use of flanges and rings machined to the close tolerances noted above, there
was no leakage even after test joints had been opened and reassembled
ten to a hundred times.
Although bolt torque measurements are usually considered very ap-
proximate indications of load, special techniques were developed which
gave reproducibility to +£10%. Bolts were lubricated with molybdenum
sulfide, and nuts were tightened several times against test blocks which
approximated the flange spacing. Nut-and-bolt combinations were ac-
cepted for use after reproducible compressive stresses were produced in
the test blocks for given torques.
Bolts may be loaded more precisely with the use of pin extensometers.
In this technique, a pin is spot-welded into one end of a hole drilled axially
through the bolt centerline. A depth gage measures quite precisely the
8-2] PRIMARY-SYSTEM COMPONENTS 431
relative strain between the lIoaded bolt and the unloaded pin. Since both
pin and bolt are at the same temperature, thermal cffeets are compensated
automatically. [xtensometers are inconvenient for contaminated main-
tenance, however.
Beeause mechanieal joints may be expected to leak, some provision must
he made to supply pressure greater than reactor system pressure to the
undersides of the ring-joint grooves. By this means, leaks may be detected
by observations of a drop in pressure in the auxiliary system. At the same
time inleakage of a nonradioactive fluid to the reactor system in the event
of a leak prevents radioactive spills. In the ease of the HRIE-2, D20 1s
supplied to the sealed annuli formed in the gasket grooves at a pressure
approximately 500 psi greater than that in the reactor system. A\ hole is
drilled through one flange at each pipe joint to the annulus of the ring
groove; the ring-joint gasket is also drilled to interconnect the annuli of
the two flanges. Heavy-wall, 1/1-in.~OD stainless-stee! tubing connects
ach flange pair with a header and pressurizer in the control area. ORNL
experience has indicated that water is more satisfactory as a leak-detector
fluid than gas, because its pressure change is a more sensitive leak ndi-
ation and beeause its surface tension reduces the magnitude of small leaks.
Viekers-Anderson joints.* Irom a remote-maintenance peint of view,
a flange requiring as few bolts as possible is desirable. Adaptation of the
Viekers-Anderson type closure appears to be a possible approach to the
problem, since it obtains uniform circumferential tightening with only
two bolts. In this type of joint, two split clamshell pieces are pressed
together with the two bolts. The clamshells bear on conical flange faces
which transform the tangential bolt forces into forces parallel with the
pipe centerline.
Usually a pressure-seal type of gasket is used with the above type of
closure beeause it is difficult to exert sufficient axial load to seat a ring-joint
gasket. Unfortunately, the present leak-detector coneept is not applicable
to such a gasket. Therefore, to permit use of Vickers—Anderson joints in a
reactor, cither a new gasket or a different leak-detector concept would
have to be developed.
Bi-metallic joints. A two-region reactor may have the problem of ob-
taining a leaktight low differential pressure mechanical joint between the
two regions. In the HRE-2, the regions are separated by a zirconium
and brazing techniques for joining the two materials are unsatisfactory.
Conventional flanges are not satisfactory because of the large difference
in thermal coefficients of expansion for the two materials. A solution to the
problem for the HRE-2 was obtained by using a titanium cylindrieal-
*Based on material submitted by R. D. Cheverton.
432 COMPONENT DEVELOPMENT
/
Bottom Pressure Vessel Flange— /
Stainless Steel
|
Bottom Core Vessel ‘ .
Flange—Zircaloy-2 st
Concentric Titanium Rings —t—k—a—%—,
Gold Foil (Top and Bonom)—‘r-*ea—/w o
f
B
Titanium Studs %
Titanium Ferrules —5‘-——-—«—4—
Stainless Steel Flange
Titanium Nuts
b
Fic. 8-10. Zircaloy-2 type-347 stainless steel transition joint for HRE-2
pressure vessel.
sleeve gasket with gold inserts for sealing, shown in Fig. 8-10. The gasket,
which consists of four concentric rings, flexes radially to absorb thermal
expansion. The gold-capped surfaces of the gasket that make the seal are
not permitted to rotate or slide relative to the flanges. The joint is loaded
with titanium-alloy bolts.
A ring joint for connecting stainless steel and titanium piping at tem-
peratures up to 650°F has also been developed [28] for possible use with
titanium letdown heat exchanger in the HRIE-2. The different thermal
coeflicients of expansion of the two materials are bridged by use of a
stainless-steel clad carbon-steel flange in the stainless half of the joint. An
HRE type of leak detector is placed in the clad flange.
8-2.7 Gas separators. The problem of removing relatively small amounts
of gas from a stream of liquid is usually solved by using a settling tank
which permits bubbles of gas to rise to a free surface. In applications in
which the amount of liquid holdup is critical, this approach has the serious
drawback of requiring too much liquid. However, a chamber which im-
parts centrifugal force to the liquid and “forces” the gas to a free surface
before the liquid leaves the chamber offers a possible solution. Of the
several types of separators which can be used, one of the most promising
1s the pipeline or axial gas separator (Fig. 8-11) used in the HRE-2.
The pipeline gas separator consists of stationary vanes or a volute,
followed by a section of pipe in which gas is centrifuged into a void which
forms at the pipe axis. whence it is removed. The energy of rotation is
8-2] PRIMARY-SYSTEM COMPONENTS 433
Stainless
4.500-in. OD .
Rotation Vanes Steel Pipe Recovery Vones\
7 LT ~ LR EZLL o ANNNG
=~ e
Re / T P T e e P P T 7 T b N :‘.
Titanium Sleeve
30%-in. Overall
Gas Takeoff Pipe
Fra. 8-11. HRE-2 gas separator.
partially recovered with vanes or a volute at the discharge end of the
separator.
A model of the gas separator was built and runs were made to test vanes
and volutes of different types for energy conversion and recovery, and
for gas-removal efficiency [29]. It was found possible to control the size
of the gas void by design of the takeoff nozzle. A separator utilizing vanes
was selected for the HRE-2 on the basis of ease of fabrication and because
high-efficiency recovery vanes could be designed. Titanium was used as
a construction material because of its excellent corrosion resistance under
highly turbulent conditions.
The design criteria for vane-type gas separators are discussed in the
following paragraphs.
Pressure distribution. The pressure drop of the liquid stream through a
well-designed gas separator can be approximated by assuming an efliciency
of conversion of pressure to velocity in the rotation system of 909 and a
recovery efficiency of 809,. Frictional drop in the vortex will be about
three times that which would be predicted if the absolute velocity of the
vortex near the wall were in axial flow. The Ap across the HRE-2 separator
is five inlet-velocity heads or 5 psi.
Length of separator. Length is usually selected to be that necessary to
bring a bubble from the periphery into the central void during the time the
bubble is moving axially through the separator. For the HRE-2 separator
about two pipe diameters are required, but for larger separators the length-
to-diameter ratio increases.
Vortezx stability. The degree of rotation for stable operation is such that
the centrifugal forces on a bubble are greater than the gravitational forces.
The dimensionless group expressing the ratio of these forces is Vt/\/g_r,
where V, is tangential velocity (ft/sec), g is 32.2 ft/sec?, and r is radius (ft).
For a stable vortex this ratio must be greater than 1; for best results it
should be greater than 4.
Entrainment. The minimum amount of entrainment for a given separator
is determined by the void stability and the geometry of the gas takeoff
434 COMPONENT DEVELOPMENT [cHAP. 8
D50 Steam
15 HP Motor sg6e ; :
;\_:%:Mj@g Gear Reduction Unit Riodme Recombiner Sparge
{ emover
Thermal Shields.. ok MGChdnti’l Seal Entrainment /- JIE: Yapoer ‘ Steam Outlet To
. Cartridge Separator __,.. “'Condenser = Separator
Vapor Exit . c | .__And Condenser
Slurry Inlet Section i Condensate -—
Outlet Pipe Full LeV&l:fiLfrf‘ Return - — Full Level
j ~Steam Heating | ‘ ) T‘
Paddle . Coll o
Steam . SRR
N Jacket)'\' o ~
Longitudinal . Slurr s
b Y L
Baoffles Outlet - == Slyrry Qutlet
(b) <)
Storage Tank
14-in. Pipe Baffle Plates
N ,
o f | T i ™ Full Level
° + Steam Jacketes, .77 i
- | B e
| e
P 0 wn
i 2%
4-in. Pipe /
(d)
F1a. 8-12. Fuel storage tanks. (a) Mechanically agitated tank (Westinghouse).
(b) Boiling tank. (¢) Sparged tank. (d) HRE-2 storage tank-evaporator.
nozzle. It is advantageous to have a high stability number. The nozzle
should be paraboloid facing the stream and have a small takeoff port.
Tests of the HRE-2 separator indicate that entrainment can be limited to
0.1 gpm at liquid and gas throughputs of 400 gpm and 4 gpm, respectively.
Tests of a 5000-gpm separator with 29}, gas gave 1 gpm of liquid entrain-
ment, minimum.
Gas-removal efficiency. One hundred percent removal of large gas bubbles
has been achieved in test models. Removal of very small bubbles is con-
siderably less efficient for gas separators of normal length.,
Although gas has been removed from slurries in an axial separator, the
design criteria are not known. The primary difficulty lies in the interaction
between small solid particles and bubbles, which may foam. The rates
of bubble rise in slurries have not been measured.
8-3. SurrorRTING-SYSTEM COMPONENTS
8-3.1 Storage tanks. Solution tank-evaporator. In the HRE-2 the stor-
age tank system has a threefold purpose: (a) it acts as a storage tank for
fuel solution during shutdowns and after removal from the high-pressure
system during the letdown of gaseous decomposition and fission products,
and after emergency dumping; (b) it acts as a generator of diluent steam
8-3] SUPPORTING-SYSTEM COMPONENTS 435
to lower the radiolytic D2 and O2 concentration to a nonexplosive mixture
prior to recombination; and (¢) it serves as a purge-water generator.
The storage tank-evaporator is designed to furnish the required amount
of steam diluent and purge water and also to agitate and mix the solution
stored in the tank. The HRI-2 evaporator is shown in I'ig. 8-12(d).
To keep the fuel solution well mixed, it was desired that the solution be
agitated by recirculation through the tank at a high rate. The recivculation
rate i such that the frictional loss in the vaporizing circuit is equal to the
hydrostatic driving force on the vaporizing fluid. Iror the HRE-2 evapo-
rator, a ratio of 176 lb of liquid cireulating for every pound of steam
generated was obtained [30].
The circulation of liquid through this type of long horizontal tank was
found to set up waves which interfered with vapor withdrawal. This inter-
ference was minimized by the use of baffle plates, as shown in Fig. 8-12(d).
Shurry storage tanks.* Three approaches are being pursued in the develop-
ment of slurry drain and storage tanks for reactor use: mechanieally
agitated tanks, agitation by steam-sparging the tank, and agitation by
surface boiling and conscquent vapor transport through the tank.
The development of a mechanically agitated tank accepts the problems
involved in obhtaining the necessary reactor-grade mechanical components
of motor, seals, drive shaft, bearings, and agitators. These are related to
the circulating-pump problems which have been discussed previously. A
conceptual design of a mechanically agitated tank proposed by Westing-
house [31] is shown in Fig. 8-12(a).
Agitation by addition of steam and agitation by addition of heat are
essentially similar, since both rely upon the turbulence created by vapor
transport to keep solids suspended.
Ixperimental investigations [32,33] of vapor transport through gas-
liquid mixtures have shown that the ratio of vapor to liquid volume may
be related to the vapor transport rate in tanks larger than 6 in. in diameter
by the relation:
1.415
el
8
where V, = superficial vapor velocity in ft/sec, fy = volume fraction of
vapor, and f, = volume fraction of slurry. This equation was found appli-
cable for slurries when V, was greater than 0.1 ft/sec and for water when
17, was greater than 0.6 ft/sec. The slurries were suspended at these vapor
velocities.
Conceptual tank designs based on agitation by vapor transport are
shown in Fig. 812 (b) and (c).
*Based on material prepared by C. G. Lawson.
436 COMPONENT DEVELOPMENT [cHAP. 8
Vapor Outlet —at—— I _ \
Fine “"Yorkmesh'' Demister Element
{0.0045-in. Wire Dia)
Coarse "'Yorkmesh'' Demister Eilement
{0.011-in. Wire Dia)
12-in. Pipe —————
Corrugated Plate Entrainment
Separator
Vapor
Inlet
Drain To Storage Tank
Vapor
Inlet
F16. 8-13. HRE-2 entrainment separator.
8-3.2 Entrainment separator. In conjunction with the storage tank-
evaporators, an efficient entrainment separator i1s required to keep the
purity of the condensate at the highest possible level. The entrainment
separator must be designed to function well during normal operation and
also during the emergency dumping operation of the reactor. I'rom the
results of a literature survey and from experimental work, the separator
in Fig., 813 was designed for the HRE-2 [34].
The HRE-2 design incorporates three modes of entrainment removal:
centrifugal separation, corrugated plates, and wire-mesh demister elements.
The centrifugal-flow inlet and corrugated plates precede the wire mesh and
remove the main portion of the liquid and the larger particles of entrained
moisture i the letdown from the gas separator. The wire-mesh demister
has a high efficiency for entrainment removal with a very low pressure
drop, and is used as the final separator stage. The wire mesh also serves
to keep the uranium reaching the recombiner below the maximum desirable
limit of 1 ppm.
8-3.3 Recombiners. For safety as well as economic reasons, it is desir-
able to recombine, either at high pressure or at low pressure, the D2 and
O2 which are formed by the decomposition of water in the fuel solution.
In the HRE-2, only low-pressure recombination has been used effectively
8-3] SUPPORTING-SYSTEM COMPONENTS 437
Thermocouple Welis
Stainless Steel Wire Screen
Catalyst Pellet Basket
Ceoling Water.
Connections .+ .-:_.::“‘ :—:- 7
I .3}' : . o
T i"_ By ee B Vapor In
1-im, Plate L \
- 12-in. Pipe
'
Condensate Out
-— 710 in.
Fic. 8~14. HRE-2 recombiner and condenser. The recombiner bed is steam
heated to keep the surface dry at all times.
for external recombination. The two most promising methods of external
recombination are the use of flame and catalytic recombiners.
For catalytic combination of Dy and O, platinum black has proved to
be the most satisfactory catalyst. It has been supported on alumina pellets
and on stainless-steel wire mesh. The platinum adheres better to the
alumina pellets, but the wire mesh is less liable to mechanical damage.
Design of the catalytic recombiners. The space-velocity method is a very
convenient basis for recombiner design. Space velocity is defined as the
cubic feet of gas-vapor mixture fed (STP) per cubic foot of catalyst bed
per hour. The maximum allowable space velocity for 1009 recombination
is approximately 4.2 X 10° hr~! at atmospheric pressure. However, the
packed bed should be shaped to ensure against channeling and to get a low
pressure drop. The HRE-2 low-pressure recombiner [35] was designed
by the space-velocity method with a safety factor of ten. To ensure against
channeling and to get as low a pressure drop as possible, an annular cylin-
drical bed was designed with a 4-in. inside diameter and 94-in. outside
diameter (Fig. 8-14).
The controlling mechanisms for catalytic reaction rates are outlined by
Hougen and Watson [36]. One of the important steps is the mass transfer
of the reactant gases to the catalytic surface. Most of the homogeneous-
reactor recombination work at ORNIL has been done in the range con-
trolled by mass transfer, at temperatures of 250 to 500°C.
However, experiments conducted at 50 psi indicated [37] mass-transfer
coefficients lower by a factor of three than the expected values based on
established mass-transfer correlations. This is explained on the basis of
poor bed configuration, channeling, and entrance and exit effects. Tests
run at 500 and 1000 psi have shown values about 60% of the theoretical
[38]. Standard mass-transfer calculations, with a suitable safety factor,
438 COMPONENT DEVELOPMENT [cuaP. 8
Coolant Air
Off-Gas
: Spark Plugs
_Jé\ Condenser Coils == }——*4-. Off-Gas
s ‘ Perfcorated
i D A
Thermowells ‘ d:j‘ = 02 In;’\j H2
Platinized
Spray Nozzle Wire Mesh
Heater - =
Liquid Level
Control Liquid Level
== (09, Hy And Control
Steam Mixture
Drain Drain
(@) (b)
Fig. 8-15. (a) Experimental flame recombiner designed to operate over wide
ranges of gas input. (b) Experimental natural-circulation recombiner used to
recombine HRE-2 off-gas after shutdown.
are believed to be the most accurate method of designing catalytic re-
combiners.
Flame recombiners. In a flame recombiner, the Hs {or D32} and O, are
actually ignited and burned to form water. The HRE-1 recombiner was
of this type. It consisted of a combustion chamber of 10-in. pipe 331 ft long
jacketed by a 12-in. pipe through which cooling water was circulated.
The combustible mixture of Hs and O was introduced through a many-
holed nozzle upon which a spark impinged from two spark plugs located
along the periphery of the nozzle. The spark impulse was produced by a
magnet, with an ignition transformer on standby. The cooling water re-
moved 70% of the heat of combustion at the design capacity of 15 sefm
of 2H3 + O2. The remainder of the heat was removed in the after-con-
denser. The condensed products of combustion were returned by gravity
to the dump tanks, and the excess Oz and fission-product gases were passed
into the off-gas system to the cold traps and charcoal adsorbers.
At low flow rates the flame burned too close to the nozzle, resulting in
overheating and flashbacks. To prevent flashbacks at low flows, a steamer
pot ahead of the flame recombiner added 2 to 3 sefm of steam to the gas
stream.
In developing flame recombiners to obtain an explosion-proof automatic
load-adjusting unit, the multiple spark-plug model shown schematically
in Fig. 8-15(a) was devised [39]. As the steam-gas mixture traveled up past
the condenser coils, the mixture eventually lost enough steam to become
8-3] SUPPORTING-SYSTEM COMPONENTS 439
combustible. The location at which the mixture became combustible de-
pended on the input concentration of gas.
Natural-circulation recombiner. For some applications it may be desirable
to have a catalytic recombiner which will operate satisfactorily without a
pump or evaporator to circulate diluent to keep the gases below the ex-
plosive limit. The natural-circulation recombiner [40] was developed for
such uses (Fig. 8-15b). Electric heaters or steam coils installed below the
catalyst start the eirculation of the diluent and keep the catalyst dry. A
cooling coil located in the annular space around the top of the chimney
completes the convective driving circuit.
High-pressure recombination. The use of high-pressure recombination in
homogeneous reactors would eliminate the need for continuous letdown of
the radiolytic gases and continuous feed-pump operation. To investigate
the possibilities of high-pressure recombination, tests [41] were made with
a loop built at ORNL.
Recombination rates were quite satisfactory. However, stress-corrosion
cracking was a significant problem in operating the stainless-steel loop.
Originally, the chloride content of the loop was high (50 ppm) and was
thought to be the cause of the stress corrosion. However, after the chloride
concentration was lowered to less than 1 ppm, stress corrosion still oc-
curred in the superheated region of the loop. It was established that en-
trained caustic was a contributing factor.
The c¢racking problem was solved by substitution of Inconel for austenitic
<teel; this material would be suitable in a slurry reactor system but not in
auranvl-sulfate system. One of the ferritic stainless steels might be suitable
for the latter application.
8-3.4 Condenser. A condenser is required in aqueous low-pressure sys-
tems (1) to condense the steam produced in the storage tank-evaporator
which 1z o source of distilled water, (2) to remove the heat of recombina-
tion, and (3) to cool the reactor contents during and after an emergency
drain. The surface-area requirements are usually determined on the basis
of item (3).
All-stainless-steel shell-and-tube condensers of conventional design
have been used in this application. The quality of construction from the
standpoint of leaktightness should approach that of the main steam gen-
erators. However, since the service conditions in the condenser are rela-
tively mild, its life should be indefinite if 1t passes acceptance tests. The
condenser used in the HRE-2 is illustrated in Fig. 8-14.
8-3.5 Cold traps.* Cold traps are usually required on fission-product
off-gas lines from homogeneous reactors to conserve D20 and to dry gases
*Based on material from R. C. Robertson, ORNL.
440 COMPONENT DEVELOPMENT [cuarp. 8
prior to adsorption in charcoal beds. Exit gas temperatures should be be-
tween —10 and —30°F. Tuypical evaporating refrigerant temperature in
the associated primary refrigeration system should be about —50 to —100°F.
The cold traps may be refrigerated either by a direct-expansion system
or by circulation of a chilled secondary fluid. The secondary type system
offers advantages of the elimination of the expansion valve from the shielded
area, and simpler defrosting procedures when using a warm supply of the
secondary refrigerant. Use of a primary system eliminates the heat ex-
changer and cireulating pump, and the sacrifice in about 10°1" temperature
difference needed in the heat exchanger, thus affording slightly better co-
efficients of performance for the refrigeration system.
The HRE-2 cold traps are double-pipe stainless-steel heat exchangers.
Flow of refrigerant is countercurrent, with the traps pitched to drain the
DoO when defrosting. The insulation is in the form of sealed cans of
Santo-Cel (8i02) fitted around the traps, this material having markedly
better resistance to radiation damage than the more commonly used Iow-
temperature insulating materials. Cold traps are used in pairs so that
icing and defrosting can be conducted simultaneously.
The major heat load on the HRE-2 cold traps was estimated to be the
internal heat generation due to radioactivity in the off-gases. Ior the
double-pipe design selected, increasing the heat-transter surface also in-
creases the mass of metal and the heat generation, so that the size must be
optimized. Over-all heat-transter coeflicients in the HRI:-2 cold traps,
using Amsco as the secondary refrigerant, were calculated to be in the range
of 30 to 35 Btu/(hr)(ft?)(°F). Velocities of the gas stream were kept quite
low; less than 5 fpm. Design velocities of the chilled coolant through the
annulus were from 1 to 2 fps.
8-3.6 Charcoal adsorbers. The oxygen off-gas from a homogeneous re-
actor contains the krypton and xenon fission products which are let down
with the radiolvtic gus. It is desired to discharge the oxygen to atmosphere,
but the permissible rare-gas discharge is limited by health physics con-
siderations. Charcoal adsorhers are used to hold up krypton and xenon
sufficiently to permit their decay to stable or slightly radioactive daughters.
The HRE-2 charcoal beds were designed [42] on the basis of adsorption
equilibrium data of krypton and xenon from the literature, with a safety
factor of six to compensate for luck of experimental data on the particular
conditions. An HRE-2 bed to process 250 ce/min of off-gas oxygen con-
tains 13.3 ft? of 8- to 14-mesh activated cocoanut charcoal. There are four
such beds immersed in a water-cooled underground conerete tank. In the
HRE-1, 13.9 ft3 of charcoal were used for a design flow rate of 470 cc,/ min.
The HRI:-1 beds operated suceessfully.
A more complete treatment of charcoal-udsorber design is given by
Anderson [43].
8-31] SUPPORTING-SYSTEM COMPONENTS 441
«——"Phasing
System .
To High Pressure
System
Intermediate
Y Water System
Screen Filters
T
[
T
Pulsating
Oil Supply —¢7
T
T T T I
& EEEEEN
Stainless Steel
Diaphram
Double Wall Shield
Rubber Pulsator «——From Dump
Tanks
F1g. 8-16. Sealed diaphragm feed pump with driving pulsator used to pump
fluids from low pressure to the high-pressure system in HRE-2.
8-3.7 Feed pumps.* High-pressure low-capacity pumps are required to
feed solutions, slurries, and water into aqueous homogeneous reactor
systems. In the HRE-2, which operates at 2000 psi, the requirements are
for from 0 to 1.5 gpm of fuel solution, 0.25 gpm of purge water to the
pressurizer, and 0.1 gpm of purge water to the circulating pump.
The types of pumps which could possibly be made to meet these require-
ments are the piston or plunger pump, the multistage centrifugal pump,
the turbine regenerative pump, and the hydraulically actuated diaphragm
pump. The piston and plunger pumps are handicapped because most
packing materials are subject to radiation damage and because there is no
absolutely leakproof sliding seal. There is no known commercial centrifugal
pump available in this high-head low-capacity range, and the develop-
ment of such a pump appears difficult. The regenerative turbine pump has
a more suitable head-capacity range, but again there is no existing multi-
stage pump mn the range desired. The hydraulically driven diaphragm
pump, as shown in Fig. 8-16, was selected for the HRIE-2 because it offers
the following advantages:
(1) The pump head and check valves are of all-welded construction and
are leakproof and maintenance-free for long periods of time.
(2) The only moving parts ingide the shield are the diaphragm and the
check valves.
(3) The drive mechanism is outside the shield, where conventional lu-
bricants and maintenance technigques may be used.
(4) The pump output is adjustable by changing the output of the drive
unit.
*Based on material prepared by E. C. Hise.
442 COMPONENT DEVELOPMENT [cHAP. 8
(5) In the event of u diaphragm rupture, radioactive fluid is still retained
within the piping system.
Subsequent development work has demonstrated that diaphragm pumps
will operate satistactorily for one year or more in this service [14-45].
Construction. The HRIE-2 duplex feed pump consists of three main
components: the drive unit, the pulsator assembly, and the diaphragm
heads. The drive unit and pulsator assembly are commercial products
built by Scott & Williams, Inc. The drive unit consists of a high-pressure
positive-displacement oil pump and a slide valve which alternately supplies
o1l to one pulsator and then the other at 78 strokes/min. While one pulsator
1s being supplied with oil from the pump, the other 1s being vented back to
the oil reservoir tank. During this venting period the elasticity of the
rubber pulsator forces the oil back to the tank and provides the energy for
the suction stroke of the diaphragm head. Reciprocating oil pumps are
used to drive smaller purge pumps on the HRE-2. The oil pulses are
transferred to the dianphragm head by the column of D20 filling the imter-
mediate systent (Fig. 8-16).
The diaphragm head consists of a stainless-steel diaphragm 0.031 in.
thick operating between two heavy flanges which have carefully machined
contoured surfaces 103-in. in diameter and 0.10 in. deep forming the
diaphragm cavity. The pumped fluid enters the pump through a 3/4-in.
pipe, passes up through the screen tube, and oscillates in and out of the
diaphragm cavity through rows of holes in the contoured surface of the
flange. The driving and pumping flanges are identical except that the
driving flange has only the top pipe connection, since the actuating column
of D20 needs only to oscillate. The sereen tube is self-cleaning, since the
flow through it is oscillating. The two flanges are clamped rigidly together
by means of heavy girth welds, which become highly stressed because of
shrinkage during fabrication.
The pump is equipped with all-welded, double-ball, gravity-operated
suction and discharge check valves. The 1-in. balls operate in close-fitting
cages (0.010-in. diametral clearance) which maintain the alignment of the
ball and seat and restrict the ball lift to 0.125 in.
Operation. The pump output can be varied from 0 to 2 gpm at 2000 psi
discharge pressure by changing either speed or displacement of the drive.
The pump performance is essentially independent of suction head and
temperature so long as cavitation does not ocecur.
To obtain proper operation of the pump, the amount of water in the
intermediate system between the rubber pulsator and the diaphragm must
be adjusted to ensure that the diaphragm does not bottom =olidly against
either contoured face of the head. This procedure, called “phasing,” is
accomplished manually by adding or venting water as required through
the phasing system shown in Fig. 8-16. For a specific pressure, there 1s a
8-3] SUPPORTING-SYSTEM COMPONENTS 443
fairly wide range of phasing in which the pump will operate properly, since
only one-third of the displacement volume in the head is used. At 2000 psi,
however, the compressibility of the drive and intermediate systems amounts
to another third of the displacement volume of the head. This results in
only a relatively narrow range of phasing in which the pump will operate
properly under all conditions of pressure and capacity.
The volume between the check valves 1s large compared with the volume
of the stroke, so that the pump is subject to gas-binding. An operational
error or a leaking discharge check valve that permits oxygenated solution
to flow back into the pump may inject sufficient gas so that the head will
not resume pumping against a high discharge pressure. A method of venting
the gas must therefore be provided.
Diaphragm development. The first heads used had a cavity 0.125 in.
deep, a 0.019-in.-thick annecaled stainless type—347 diaphragm, and had
no screening. These diaphragms suffered ecarly failure due to irregular
contour machining and dents caused by the trapping of dirt particles
between the contour face and the diaphragm. To reduce the over-all
diaphragm stress level and to reduce or eliminate the localized stress risers,
the coutour depth was reduced to 0.010 in., the machining procedure was
changed to produce a smooth, continuous contour, and 40-mesh screens
were installed. These changes increased the average diaphragm life to
about four and a half months. However, some failures occurred in as little
ax two months, An intensive program was initiated to develop a head
that would function consistently for one year or more.
The first objective of the program was to reduce or eliminate stress risers
cau=ed by dirt particles. Substitution of 100-mesh screen tubes for the
10-me=h =creens reduced denting observed on test diaphragims by an order
of magnitude. A sintered stainless-steel porous tube with 20-micron
openings 1s being evaluated at the present time in an experimental pump
to reduce the problem further.
A second objective was to investigate possible improvements in contour
in order to minimize diaphragm stress for the desired volumetrie displace-
ment. Theoretical and experimental stress analyses showed that the
original contour was nearly optimum, and it was retained [46].
A third objective was to determine the nature of the diaphragm motion
and improve 1t if necessary. A special spring-loaded magnetic instrument
was built to indicate diaphragm position while operating. Three such
indicators were installed in a standard head and recorded simultaneously
on a fast multichannel instrument. It was observed that the diaphragm
was displaced in a wave motion starting at the top of the head, producing a
sharp bend at the bottom where most failures occurred. It was observed
also that there was considerable flutter in the diaphragm, so that it was
heing flexed more frequently than anticipated. By increasing the thickness
444 COMPONENT DEVELOPMENT [cHAP. 8
of the diaphragm from 0.019 in. to 0.031 in., symmetrical deflections with
less flutter were obtained. Changes in the drive system which reduced the
noise level were cffective in creating smoother diaphragm deflection.
These changes were incorporated into later pumps.
The fourth point of the program involved determining the endurance
limit of annealed 347 stainless steel and other possible diaphragm materials
in fuel solution. A literature review indicated that in a corrosive environ-
ment there may be no endurance limit as such, but that the curve of stress
versus number of cycles would continue its downward slope indefinitely.
The literature also suggested that significant gaing in endurance limit may
be achieved by cold-working stainless steel, or by using a precipitation
hardening steel such as Allegheny-Ludlum AM-350. Standard reverse
bending sheet specimens of each material were operated at 2000 cycles/
min in environments of air, distilled water, and fuel solution [47]. Sur-
prisingly, it was found that hardened materials suffered a drastic reduction
in endurance limit in fuel solution but not in water, whercas the anncaled
347 stainless-steel endurance at 107 eyeles was 39,000, 36,000, and 34,000
psi, respectively, in air, water, and fuel. None of these media produce
appreciable corrosive attack on any of the materials tested.
Checl-valve materials. Stellite balls and seats have been operated in fuel
solutions for more than 10,000 hr with no sigh of damage. It was rather
surprising when, during preoperational testing of the HRE-2) four sets
of valves failed in oxygenated distilled water i about 500 hr. Further
testing showed that preconditioning by operation in uranyl sulfate made
Stellite suitable for oxygenated-water use. Armco 17-4 PH stainless steel
was also demonstrated to be an excellent seat material in both water and
uranyl sulfate.
HRIE-2 fuel pumps now contain Stellite Star J balls and Stellite No. 3
seats. Check valves are pre-run in fuel solution hefore being welded to the
pump heads. HRE-2 water pumps contain Stellite Star J balls and 17-4
PH ceats.
All the standard metals have failed very quickly in check valves pumping
ThO, slurry to high pressure. However, some success has been achieved
with aluminum oxide and other very hard ceramies.
Welding. Considerable difficulty has been experienced in the design of
welds subject to eyelic pressure stresses. Iixtreme conservatism with regard
to metal thickness is helpful in eliminating fatigue failure of welds. Nozzles
welded to pump heads have heavy sections at the weld. [Mull-penetration
welds are used throughout, and butt welds are used 1if possible. The inside
surfaces of welds are machined smooth when they are accessible.
Sturry diaphragm pumps. Two methods of pumping slurry with the dia-
phragm pump are being tested. In the first, the check valves are located
several feet below the head and connected thereto by a vertical pipe. By
8-3] SUPPORTING-SYSTEM COMPONENTS 445
sizing the vertical leg so as to maintain low oscillatory velocities, a stable
slurry-water interface forms, permitting the diaphragm head to operate in
relatively pure water while slurry pumps through the check valves. A
venting system is necessary. Such a pump has been operated satisfactorily
at low pressure and will be tested at high pressure.
The second method uses a diaphragm head having a contour in the
driving flinge, a recessed cavity in the pumping flange, and an arrange-
ment that permits the diaphragm to operate only from the driving contour
to center. This arrangement preciudes the possibility of slurry being trapped
between the diaphragm and contour, leading to undesirable diaphragm
deflection patterns. Such a pump head has been built and will be tested
8-3.8 Valves.* Valves are key components in reactor systems, since they
are the means by which process gas and liquid streams are controlled
[48,49]. In the HRE-2 system, which has no control rods, temperature
and reactivity are controlled by valves that control the concentration of the
fuel solution, and the power is controlled by valves that control the rate
of =team removal from the heat exchangers. “Dump” valves perform an
emergency scram and normal drain function by controlling the flow of
fuel solution to low-pressure storage tanks. Other valves perform pressure-
control functions, allow noncondensable gases to be bled from the system,
or are used to Isolate equipment.
Actuators. The problem of radiation damage to hydraulic fluids, elas-
tomers, or electrical insulations is avoided by utilizing pneumatically
powered metallie bellows for remote actuation of the valves. The actuator
ix a =imple linear device which can be controlled with standard pneumatic
controllers or regulators. The bellows may also be stacked to multiply the
forces available. In the HRIE-2, pneumatic actuators develop up to 540 Ib
force.
An actuator capable of developing o thrust of about 12,000 1b was cyeled
four times per minute at a stroke of 1,2 in. and a pressure of 80 psig for
265,000 cycles before developing a small leak in the stem sealing bellows.
Two and three bellows-spring assemblies from these units have been at-
tached to o common shaft and conneected in parallel to a source of air pres-
sure in preliminary tests of an even more powerful actuator.
Handwheel operators, with or without extension handles, have been
used successfully in all-welded valves for mildly radioactive service.
Valve designs used in HRE-2. The valve designs used on the HRI-2 are
all quite similar. Figure 8-17(a) illustrates the “letdown” valve, which is
typical. This valve throttles a mixture of cooled gas and liquid from the
2000-psi high-pressure system to the low-pressure storage tanks. The
flow is introduced under the seat to keep the bellows on the low-pressure
*Based on material furnished by D. 8. Toomb.
446 COMPONENT DEVELOFMENT [crAP. 8
Air Exhaust
Port %
. L J Secondary
£ 7 A Packing Gland
a2 - ' 1
Actuating - [_§ b | - Seal
™
Bellows ¢ ‘
I . -
(-t "E}A“\ACTUC’“”Q Beliows
T Air Port .
i . Leak-Detecting
L Backseating T
Steam Seal Stem : ap
Bellows
Bellows
Sedling Weld/
Primary Bellows Seal
= Secondary
2 Packing Glond
Backseating 4 Seal
Stem
7% in.
Bellows Sealing Bellows
Weld .
° Tap " ]
Primary ; > 4
101234 Bellows Seal // 3
inches /,/*;/’ 77— Integral
S Flanged Body
o 347 SS Body 77 T
With Integral Seat
—~—— 273 in,—
TQOOO psi Inlet Pressure
(a) (b)
Fic. 8-17. (a) HRE-2 letdown valve. (b) HRE-2 low-pressure valve.
side of the throttling orifice and thus under less strain. A seat integral
with the valve body is used to avoid the difficult problem of leakage around
removable seats. Stellite No. 6 and type 17-4 PH stainless steel plugs have
been used, since these very hard materials are corrosion resistant in uranyl-
sulfate solutions below 100°C and resist erosion due to flow impingement.
The primary bellows seal, 13-in. OD by 7 /8-in. ID and 32 in. long, is mechani-
cally f-=med of three plies of 0.0085-in. type—-347 stainless steel stock. The
bellows seal assembly i1s in two sections, welded together, because the
bellows length needed for the 1/2-in. stroke cannot be manufactured in a
single section at this time. An average bellows life of 50,000 5/8-in. strokes
has been obtained at 500-psi with this assembly. The stem 1s of hexagonal
stock and fits in a similarly shaped guide to prevent a torque from being
applied to the bellows. The leak-detecting tap between the bellews and the
secondary graphited-asbestos packing seal affords a means of detecting a
bellows leak, while the asbestos gland prevents gross leakage of process
fluid in case of bellows failure.
8-3] SUPPORTING-SYSTEM COMPONENTS 447
The valve, which was supplied by the Fulton Sylphon Division of Robert-
shaw-Fulton Controls Corporation, is rated for 2500-psi service with the
flow introduced under the seat; however, the downstream pressure is limited
to 500 psi by the bellows seal. The valve has a €, (flow coeflicient) of 0.1.
The reversible-action operator, supplied by The Annin Company, has a,
50-in? effective area. It is rated for a maximum of 60 psi air operating
pressure. The action illustrated is spring-closed, air-to-open; however,
by a simple interchange of parts, the actuator operation can be reversed.
The actuating bellows is made from type—321 stainless steel and was formed
by the Stainless Steel Products Company. The stem guide bushing is
brass.
The largest valve used in the HRE-2 is the blanket dran valve, which has
a 1-m. port and a C'y of 10. The valve and operator were supplied by Fulton-
Sylphon. The operator supplies a maximum force of 5440 Ib, and the full
stroke 1s 3/4 in.
The only two process valves in the HRE-2 which operate with full system
pressure on the bellows seal are those which are used to isolate the reactor
from the chemical plant. The bellows used here, supplied by Fulton-
Sylphon, are rated at 2000 psi and 300°C.
The low-pressure HRE-2 valves are novel in that ring-joint grooves are
integral with the valve body, as illustrated in Iig. 8-17(b). Long bolts at
the corners of the valve body hold the companion flanges; the valve is
replaceable with the disassembly of only one set of bolts.
The main problems encountered in HRE-2 valves have been valve stem
misalignment and corrosion of valve plugs.
Valve trem materials. In uranyl sulfate service, stainless steel seats are
used with type 17-4 PH stainless steel or Stellite plugs. The latter material
is uzeful only below 100°C and where only a small amount of oxygenated-
water service i1s anticipated with a high pressure differential across the
valve.
In slurry service, metallic trims such as those above have been satis-
factory for low-pressure valves but unsatisfactory for long life in high-
pressure service. Ceramic materials appear promising, but little experience
has been obtained to date.
A gold-gasketed valve has been developed for tight shutoff of gases.
The gasket 1s placed into a groove machined in the valve plug, which mates
with a tongue machined into the seat. This type of trim has also given ex-
cellent results in one hot uranyl-sulfate loop application.
Slurry service valves. In addition to the erosiveness of slurries, other
problems are introduced by their tendency to settle out in the primary
bellows seal or at stem guiding surfaces, thus interfering with valve action.
This may be avoided by purging slurry from the bellows compartment with
distilled water. It is hikely that the hydrodynamic design of slurry valves
448 COMPONENT DEVELOPMENT [cHAP. 8
Asbestos Tape
PV IIIII S S B FIPIE S ST N
T ',[ g il { -
g ey 2 Thermocouples 1TH;E) \l[ & -
\ &_’4’."{_’_' T T T T T T A T T T T T T T T e T e e SIS Sl ."."Ti
Conax Gland
Fic. 8-18. Differential thermal expansion valve to control gas flow in the HRE-2.
may be revised to make entry of solids into the bellows compartment
improbable.
Slurry throttling has been accomplished by use of long tubes or capil-
laries. These have the disadvantage of fixed orifices, in that continuous
flow control 1s not possible.
Special gas-metering valve. An ORNL-developed* differential thermal-
expansion metering valve is used to regulate the flow of oxygen gas to the
HRE-2 high-pressure system [50]. The required flow is very small and is
difficult to control by conventional mechanical positioning methods. The
valve shown in Fig. 8-18 utilizes the difference in thermal coefficient of
expansion of tantalum and stainless steel to effect flow control. The tan-
talum plug is used to avoid any possibility of an ignition reaction between
the oxygen gas and the metal, the temperature of which for a flow of 2000
std. ec/min with a 400 psi differential can reach 300°C. The design incor-
porates all-welded construction and is covered with a waterproof protective
housing. The resistance heating element and thermocouple are duplicated
to ensure continuity of service.
8-3.9 Sampling equipment. Operation of an aqueous homogeneous re-
actor requires that numerous samples be taken in maintaining control of
the chemical composition of the solutions. Because of the radioactivity
associated with these fluids, standard sampling equipment must be modi-
ried, or entirely new apparatus must be devised for taking the samples.
Examples of sampling equipment presented here were designed for use on
the HRE-2 at ORNL.
Samples of liquid and suspended solids will be taken from the high- and
low-pressure systems of the HRE-2. Solution from the high-pressure
system is reduced in temperature and pressure from 300°C and 2000 psl to
approximately 80°C and 1 atm by a cooler and throttling valve before
*17.S. Patent 2,610,300 (1952). [Assigned to the U.S. Atomic Energy Commis-
sion by W. W. Walton and R. C. Brewer.]
8-3] SUPPORTING-SYSTEM COMPONENTS 449
- .. ¢ Valve 5t
Loading . ave Stems I
Tube 7 T }\\. - ]
i@t @ Universal Joint
e - /
Plan “
(With Carrier Removed) R fi.fi
i 04 812 N L
Tos . —=r—Valve Stem
_ _ Inches f\k g5
Packing Gland v | | A
: : ' \ \1
Carrier | _ B
e Vent A i Bellows
L Positioning Handle ! 1 f
... < . - 11|
E Overflow ~— (it -
| | _
Stop | Sample
Isolation Chamber ‘ ‘ Cooling Coil
i i
‘ Flask Holder
Loading Plunger
Tube — Needle Holder
Needle
Isolation L
Chamber™} s ——— Sample Yalve
i Rubber
Top of Flask +——Tubing Disconnect Diaphragm
Holder ™ .
Transfer
. -~y
Mechanism
Air .
Cylinder |_.Differential Pressure Cell Receptacie
Fia. 8-19. (a) HRE-2 sampling facility. Flask holder has just been lowered
through the loading tube. It is then moved under the isolation chamber by the
transfer mechanism. (b) HRE-2 sampler head, shown in the position of transferring
sample to the receptacle.
entering the sample station. There, a sample of 4 to 5 ml is isolated and
removed for analysis [51].
Figure 8-19(a) shows the general assembly of the sampling facility.
Virtually all the mechanism is suspended from a shield plug. Personnel
shielding is provided by a 2-ft depth of lead shot and water in the plug.
The loading tube is sealed by a plug valve to maintain a slight vacuum in
the housing. Threaded backup rods extending through the plug are em-
45() COMPONENT DEVELOPMENT [cuap. 8
ployed to make the final connections with reactor piping after the plug
assembly is lowered into its housing. Each sampling facility contains two
isolation chambers: one for isolating samples from the high-pressure system
and the other for obtaining samples from the low-pressure system. Each
chamber in the station is served by a common loading and manipulating
device.
When a sample is being taken, solution from the desired system is al-
lowed to flow through its isolation chamber until a representative sample
is obtained. The isolation chamber is then valved off. An evacuated
sample flask is placed in the holder and lowered through the loading tube
to the transfer mechanism. The assembly is then indexed under the proper
isolation chamber, where the flask holder is raised by an air cylinder until
contact is made between the isolation-chamber nozzle and the inverse cone
of the carrier head (Fig. 8-19h). Further hfting of the flask holder causes
the hypodermic needle to puneture the rubber diaphragm. The sample is
then discharged into the flask by opening the valve on the chamber. When
the sample is in the flask the procedures are reversed, and the flask holder
is removed into a shielded carrier for transport to the analytical laboratory.
Electrical contacts indicate positive positioning of the flask holder under
the isolation chamber and closure of the isolation-chamber nozzle.
A third sampling station for the HRE-2, identical to the fuel and blanket
facilities except for larger passages and a modified isolation chamber, is
employed for sampling a fuel stream in the chemical processing facility.
This stream has the order of 50 times the solids concentration of the other
streams being sampled.
8-3.10 Letdown heat exchanger. The purpose of the letdown heat ex-
changer is to conserve the sensible and latent heat of the solution-steam-
gas mixture removed in the gas separator prior to discharging it to the
dump-tank system. It is necessary also to cool the letdown stream to below
100°C hefore it reaches the letdown valve to minimize corrosion of the
valve trim.
The thermal design of the exchanger is conventional [52]. In the HRE-2
stainless-steel triple-pipe unit, 400,000 Btu/hr arc removed from the
letdown stream into the countercurrent fuel feed stream, the pressurizer
purge-water stream, and a cooling-water stream.
The unique feature of the design deals, with the flow geometry of the
letdown stream [53]. To promote cfficient flow of the two-phase mixture
through the letdown valve, it is necessary to prevent flow separation of
the two phases. This is done by utilizing the annulus of the exchanger,
with weld-bead spacers every 3 in. to promote turbulence. The velocity
of the letdown stream is not permitted to fall below 5 ft/sec for any pipe
lengths above 1 ft anywhere between the gas separator takeoff and the
letdown valve.
8-3] SUPPORTING-SYSTEM COMPONENTS 451
During the transit from reactor operating temperature to 100°C in the
letdown heat exchanger, fuel solution must go through the temperature
range 175 to 225°C at which stainless-steel corrosion resistance passes
through a minimum. This suggests that after several years leakage would
occur between the feed and letdown streams. This problem can be ecireum-
vented by substitution of titanium for stainless steel.
8-3.11 Freeze plugs. Several reactor installations have employed freeze
plugs on liquid-carrying process lines to assure absolute leaktight shutoff.
Lines up to 4 in. in diameter have been frozen with a simple wrap-around
coil of copper tubing when there was no flow in the pipe other than the
convective currents set up by the freczing process. It is conceivable that
leaktightness in very large lines might be achieved by refrigerating the
passages of valves to freeze a relatively small amount of liquid at the
valve seat. This freezing technique is most helpful in reducing the spread
of contamination during maintenance.
The most efficient frecze-jacket design is one which provides an annular
space around the process pipe and allows direct contact of the refrigerant
with the pipe. This is generally considered undesirable, however, from the
standpoint that if process fluid should leak into the refrigerant, activity
would be carried outside the shielded area. I'reeze jackets consisting of
tubing wound around the process pipe perform noticeably better if soldered
or welded to the process pipe; filling the interstitial space with poured
lead also appears to be o worth-while refinement for lines difficult to freeze.
Tubing 5/16-in. in diameter has been used on 1/4- to 1/2-in. standard pipe
sizes; 3/8-in. tubing on 3/4- to 13-in. pipe sizes, and 1,/2-in. tubing on sizes
up to 4 in. Clamp-on, or clamshell, types of freeze juckets were developed
for the HRE-2 for temporarily freezing certain lines,
On the HRE-2, stainless-steel refrigerant tubing is used for permanent
freeze jackets on hines which normally operate at or above 350°F. Copper
tubing, which is oxidized more readily in air, is used for lower temperature
lines. A jacket length of 3 to 4 pipe diameters has been demonstrated to be
optimum:.
Freezing times of a few minutes for 1/2-in. and smaller lines and up to
several hours for 3- and 4-in. sizes have been obscerved when the refrigerant
temperature is in the —20 to —40°F range and with flows through the
jacket of 3 to 5 gpm. Insulation outside the freeze jacket materially aids
in the ability to freeze lines with particularly high heat load, such as those
subjected to gamma heating. If the freeze jacket must be operated sub-
merged, such as for underwater maintenance, it has been found that pro-
tecting the jacket from convection water currents by means of aluminum-
foil wrapping aids materially in the freezing process.
452 COMPONENT DEVELOPMENT [caaPp. 8
8-4. AuxiLiARY COMPONENTS
8-4.1 Refrigeration system.* Refrigeration is required in the HRE-2
for operation of freeze plugs and cold traps. The refrigeration system con-
sists of a primary loop, which is not irradiated, and a secondary liquid eir-
culating system which enters the shield.
A two-stage primary mechanical refrigeration system is employed in the
HRE-2. Refrigerants commonly used in such a system are the halogenated
hydrocarbons, provided that the primary refrigerant remains outside the
reactor shield. Breakdown of this series of refrigerants under radiation has
been observed to have the serious effects of forming phosgene gas and in-
soluble tarry polymers, thus creating conditions corrosive to stainless steel.
Carbon dioxide 1s probably the best refrigerant for use in an irradiated
direct-expansion system, but it must be used at high pressure.
Choice of a secondary refrigerant to be circulated through radioactive
equipment is difficult in that the fluild must not only meet the obviously
desirable properties of having a low freezing point, suitable viscosity, low
vapor pressure, noncorrosiveness, nontoxicity, and nonflammability, but it
must also be resistant to radiation damage, not contain chloride ions which
might promote stress-corrosion cracking of staimnless steels, and not evap-
orate to insoluble residues. Misecibility with water would be advantageous
if underwater maintenance techniques are employed in that if some refriger-
ant escapes, there is less impairment of vision and a film is not left on
equipment when the water is drained.
After considering many possible secondary refrigerants, Amsco 125-82,
an odorless mineral spirit resembling kerosene in its physical properties,
was selected for the HRE-2. Its performance to date has been quite satis-
factory.
In addition to the primary refrigeration system used to maintain a
central supply of chilled Amsco, it was useful for short-term maintenance
operations at the HRE-2 to have also a portable rig, consisting of an in-
sulated tank and circulating pump. Chilling was accomplished by floating
blocks of COs-ice directly in the liquid; secondary refrigerant tempera-
tures of about —75°F were maintained with a circulation rate of about
4 gpm and with an ice consumption rate of 75 to 100 Ib/hr.
8—4.2 Oxygen injection equipment.f Oxygen is needed in the high-
pressure fuel system to maintain chemical stability of the uranyl-sulfate
solution and to reduce corrosion of the stainless steel container. This oxy-
*Based on material furnished by R. C. Robertson.
fMaterial submitted by K. C, Hise.
8-4] AUXILIARY COMPONENTS 453
gen may be introduced most conveniently into the fuel feed stream, at
either the suction or discharge of the feed pump. As a result of operational
experience, high-pressure injection has been found to be more flexible and
to give better feed-pump performance.
The oxygen system requires a high-pressure gas supply and a metering
device. The first supply used in the HRE-2 was a converter manufactured
by Cambridge Corp. of Lowell, Mass. This has been replaced by high-
pressure cylinders, which have considerably lower operating costs. Oxygen
compressors may be desirable to recirculate contaminated oxygen and are
being investigated. Metering is accomplished with a thermal valve (de-
scribed earlier) controlled by a capillary flowmeter.
Oxygen converter. The HRE-2 oxygen generator is designed to convert
liquid oxygen to the gaseous state and deliver it to the fuel and blanket
high-pressure systems at pressures up to 3000 psig. The capacity of the
generator 1s 0.47 {3, or 30 Ib of oxygen, when 909 filled with liquid. This
will permit delivery of approximately 21 1b of oxygen gas at 3000 psig and
70°F. This pressure is automatically maintained over a flow range of from
0.01 to 0.7 Ib/hr.
The oxygen generator consists of an insulated high-pressure container,
with an electric heater and automatic pressure and temperature controls.
The high-pressure inner vessel 1s fabricated of type-304 stainless steel.
Charging of the converter with liquid oxygen is a manual operation. The
labor of charging and the inefficient utilization of oxygen are disadvantages
of this unit.
High-pressure cylinders. The HRE-2 is now using 300-liter high-pressure
cylinders which are commercially charged to 2400 psi and are used down
to 2000 psi. A hank of three eylinders will last for about two days of normal
operation. This system involves no waste of gas, since the cylinders are
recharged from 2000 psi to 2400 psi, with very little operator attention or
hazard.
Oxygen compressors. High-pressure low-capacity laboratory-type oxygen
compressors have recently become commercially available. Pressure
Products Industrics, of Hatboro, Pa., produces a compressor having a
stainless-steel diaphragm hydraulically actuated in a contoured chamber
by a reciprocating drive. A single-stage machine capable of compressing
approximately 0.8 sefm of Oy from 500 psi to 2500 psi has been purchased
and placed in service in the HR'T mockup. Although there have been some
difficulties with the hydraulic plunger packing, it has been generally satis-
factory.
A three-stage machine capable of compressing 2 sefm of contaminated
oxygen from atmospheric pressure to 2500 psi is being designed. The
diaphragm heads will be located remotely with respect to the drive, as is
done in diaphragm feed pumps.
454 COMPONENT DEVELOPMENT [cHAP. 8
85. INsSTRUMENT COMPONENTS*
The instrumentation and controls systems for aqueous homogeneous
reactors are similar to those used in modern high-pressure steam power and
chemical plants. However, problems attendant on radiation damage to
insulations, the difficulty of performing maintenance or replacement
operations, the requirement for the absolute leaktightness and the very
high reliability of components necessary for safety and plant operability
have required considerable development of special components.
8-5.1 Signal transmission systems. In a typical control loop the pri-
mary and final control elemets are in a radioactive area isolated from the
control room by a vapor container and a concrete radiation shield.
Electric. Advantages for electric transmission under these conditions
include the ease of readjusting system zeros and spans from the control
room and the ability to sense motion from weld-sealed transmitters without
the use of flexure seals such as bellows and torque tubes. The speed of
information transmission, the ease of switching signals, and the ability of
the sensing elements to operate over wide temperature ranges may also be
important. Disadvantages of the electrical system include the possible
radiation damage to insulations and the present unavailability of a cheap,
reliable linear-power actuator for control valves.
Pneumatic. Advantages of a pneumatic system include the utilization
of all-metallic radiation-resistant construction for the transmitters and
valve actuators by the use of metallic bellows, bourdon tubes, and con-
voluted diaphragms. The advantages of the high state of commercial
development, low cost, reliability, miniaturization, and ease of paralleling
of receiving elements are considerable. A disadvantage of the penumatic
system is the tubing transmission line, which affords a path out of the
radiation enclosure for contaminated fluids or vapors in case of a release
of radioactivity coupled with a line break.
HRE-2 system. A combined electric-pneumatic system (described in
Article 7-4.8) is used in HRE-2. In the control room, electric signals from
primary variable sensing elements (temperature, flow, liquid level, pressure,
etc.) are converted by transducers to penumatic signals, and these are used
to actuate miniature pneumatic display instruments and pneumatic valves
in the reactor. The escape of radioactivity through air lines is prevented
by the automatic closure of “block’” valves within the vapor-contained
area, on a signal of the release of radiation. Radiation damage to primary
elements is avoided by the use of inorganic electrical insulations such as
glass, ceramics, mica, magnesium oxide, and magnesium silicate. Electric
control actions are derived from the pneumatic signals by pressure switches.
These switches are simple devices in which diaphragm deflection opens or
*Material submitted by D. S. Toomb.
8-5] INSTRUMENT COMPONENTS 455
Waterproof Coil Housing
A_E/(DifferenfiolTrcmsformer)
3
T
T' | Piston Position Sensing Coil
Magnetic Piston With
Stainless Steel Sheath
i
Helical
Permanent Magnet Yoke Suspension Springs
Copper Damping Ring
Sheathed in Stainless Steel
L 7
VoporTcp<‘f‘_i‘ S
| -
‘W\ 3
R
7
e
T
77
e
¥
v
o
14 in,
1 “
5 é% Displacer (*'Float’")
- \\
N
’
v
;.
V/
?
%
;’%,-‘
R ¥X§§§L\\\\\\K§\
Low Level Tap
. N
Fic. 8-20. HRE-2 float-type level indicator (covers a 5-in. range at psi-2000
operating pressure).
closes an electric snap-acting switch. Electric interlock control of the
penumatic signals to final control elements is achieved by the use of
solenoid-actuated pilot valves.
8-5.2 Primary variable sensing elements. Liquid-level transmatters.
Knowledge of liquid levels in reactor systems and loops is eritical for main-
taining the proper balance of liquid and vapor in pressurizers and storage
tanks. It is desired also to be able to maintain accurate inventories of the
hazardous and valuable fluids which are contained.
456 COMPONENT DEVELOPMENT [cHap, 8
There are a large number of liquid-level sensing devices in use, since no
one device has been developed which satisfies all the criteria of precision,
rapid response, insensitivity to temperature and pressure, and utility of its
signal for control functions. Devices which have been used at ORNL are
described in the following paragraphs.
(1) Displacement or Float Transmitters, The ORNIL-developed dis-
placement transmitter, used to control HR¥-2 pressurizer level, consists of
a 5-in.-long displacer suspended by two helical springs (Fig. 8-20). An
extension rod above the springs positions a magnetic piston in the center
of a differential transformer. Troublesome vibration of the float is damped
by the action of the field from permanent magnets on a one-turn copper
ring. The only nonwelded closure is the ring-joint flange, which makes the
unit easily replaceable.
The differential transformer is a compact, highly sensitive, linear device
which is commercially available. The most satisfactory instrument system
for the differential transformer is a high-frequency oscillator-amplifier
phase-sensitive demodulator carrier system which provides the necessary
sensitivity and stability and eliminates phase-motion ambiguity associated
with the null voltage.
Float transmitters of this type have also been built with cantilever
springs, with floats up to 47 in. long, and with hydraulic damping vanes
attached to the hottom of the float in lieu of the magnetic damping [34].
They have given excellent service in continuous control applications.
However, the displaccment transmitter is quite sensitive to fluid densities,
and the springs exhibit some changes in properties with temperature. The
best spring material tested to date is Isoelastic spring alloy supplied by
John Chatillon and Sons, which may be gold-plated for supplementary
corrosion resistance.
Hollow spherical floats, lighter than water, have also been used at pres-
sures below 600 psi. Magnetrol, Ine., makes a unit in which float position is
transmitted magnetically. Moore Products Company supplies a level
alarm where float position is transmitted mechanically through the all-
welded housing by a flexible shaft.
(2) Differential-Pressure Cells. D/P cells have been used successfully
in HRE-1 and in loops as level transmitters. The variable liquid leg is
compared to a reference level maintained by condensation or liquid addi-
tion. Since the density of water is temperature-dependent, the temperature
of the primary systemn and the lines to the D/P cell must be known for
accurate level measurement.
(3) Weigh Systems. For obtaining an accurate inventory of IHRI-2
storage tanks, they are weighed with pneumatic weigh cells. This was
found to be the only feasible method of measuring the quantity of liquid
in long, horizontal storage tanks. Piping to the tanks is kept flexible by
8-5] INSTRUMENT COMPONENTS 457
the use of horizontal L and U bends. A pneumatic system is selected pri-
marily because taring can be done remotely with balancing air pressures,
and components are less susceptible to radiation damage. The pneumatic
load cells, which are supplied by the A. H. Emery Corporation, have an
accuracy of 1/10%; however, when used in a system with solid pipe con-
nections to the weighed vessels, an accuracy of 19 of full load results.
(4) Heated Thermocouple Wells. Heated thermocouple wells have been
used for liquid-level alarm or control. The thermocouple junction is
normally held a few degrees above the vapor temperature; as the liquid level
surrounds the probe, the increased heat transmission to the fluid from the
probe lowers the thermocouple signal output [55]. Several wells must be
used for control purposes. This system gives rather sluggish response.
(5) Capacitance Probe. An aluminum oxide capacitance probe, manu-
factured by Fielden Instrument Division, has been recently received by
ORNTL but has not vet been evaluated. This instrument senses the dielectrie
constant of the medium it contacts. Its ceramic-to-metal seal is rated at
2000 psi and 636°F. This type of instrument may prove useful in water or
slurry service.
Differential Transformer
o . - Cast Aluminum
Position Adjustment \{..
Electrical Housing
Core Guide Bearing
i lTerminaI Strip
B
Differential Transformer
Core Motion Sensing Element |-
Stainless Steel
Bourdon Tubes
‘\ ;Mognefic Core
"0 . .
a Differential Transformer
a . Retaining Spring
! Core Drive Rod
2
Scale In
; Inches
3
-
4
| Stainless Steet
57 Safety Housing
Fie. 821. Bourdon-tube pressure transmitter in safety housing. Sensing ele-
ment, twin Bourdon tubes; range, 0 to 2500 psi; test pressure, 3750 psi; accuracy,
+ 19, of range; transmission, electrical; fabricated by the Swartwout Company.
458 COMPONENT DEVELOPMENT [cHAP. 8
Magnetic Piston Cased
T In Stainless Steel
Differential Pressure Sensing Diaphragmgy: Electrical Cable Gland
1.9 ] 2 3 4 5 ¢ 7 L Piston Motion Sensing Coil
Scale In Inches - Loy Differential Pressure Transmitter
ol SN ) [Foxboro Company)
L T !
T Autoclave Disconnect Fitting L
apillary |
AN
F16. 8-22. Capillary flowmeter, used to meter small gas or liquid streams,
shown with high-pressure seal-welded differential-pressure transmitter.
(6) Fluid Damping Transmitters. The Dynatrol transmitter, manu-
factured by Automation Products, Inc., is an interesting possibility for
use as a fluid damping transmitter. It contains a vane exposed to the
process system and vibrated through a pressure housing by alternating-
current excitation of a solenoid. The degree of damping, which is dependent
on the area of the vane covered with liquid, is measured by a second sensing
coill. No test experience with this transmitter is yet available.
Unusually difficult level-sensing problems are introduced when it is
desired to measure or control the true level of a slurry or a boiling liquid.
Most proven devices are density-sensitive, and the mean density of two-
phase systems 1s usually unknown. Of the level transmitter types cited
above, none appears adequate for continuous-range indication. IFor spot
indication, float, capacitance, and Dynatrol transmitters are promising.
Pressure and differential-pressure measurement. Bourdon tubes of weld-
sealed 347 stainless steel are used for pressure transmission in the HRE-2.
Most suitable for reactor use are units contained within secondary pressure
housings, such as the 2500-psi pressure transmitter shown in Fig, 8-21.
Baldwin cells have been widely used for accurate pressure measurement
in loops.
Bellows or diaphragm differential-pressure cells have been used to meas-
ure pressure differentials with full-scale sensitivity of 25 in. of water to 125
pst. A typical D/P cell with electric transmitter is shown in Fig. 8-22,
Pressure transmitters are usually tied into the steam or water portions
of aqueous homogeneous systems to reduce the probability of plugging or
other damage. Where it is necessary to connect a D/P cell into a slurry
system, the pipe connection is regularly purged with 10 to 30 cc/min of
water. Large vertical piping connections with the transmitter mounted
above the primary piping have also been used. Diaphragm transmitters
mounted flush with the pipe surface are being developed for slurry applica-
tions.
8-5] INSTRUMENT COMPONENTS 459
Flow transmitters. Tlow measurements are made in high-pressure lines
by sensing the pressure drop across a calibrated orifice or venturi, or by the
transmitting variable-area type of flowmeter. The latter meter resembles a
Rotameter with float position transmitted electrically. It has the ad-
vantage of being an in-line element but is not readily applicable to large
flows.
Another system for metering and controlling small liquid and gas flows
in the HRE-2 is illustrated in Fig. 8-22. The pressure drop across the
metering capillary is measured by the differential-pressure transmitter and
the output signal is calibrated in terms of flow. The “snubbing” capillary
is used to prevent the sudden application of pressure to the inlet side of
the differential-pressure transmitter, which would cause undesirable zero
shift.
A technique widely used in the HRIE-2 for metermg purge flows 1s a
“heat balance” flowmeter in which a known amount of heat is added or
extracted from the process stream and the temperature change noted.
Temperature measurement. 'The most commonly used method of tempera-
ture detection in the HRE-2 is the thermocouple measurement of vessel
and pipe wall temperaturcs; the couples are spot-welded directly to the
wall and then covered with insulation. When faster response is desired,
thermocouples are spring-loaded into thin thermowells. Chromel-Alumel
wire is generally used because its resistance to corrosive attack by moisture
is better than that of iron-constantan alloys.
Thermocouple wire insulated by compressed magnesium oxide powder
and housed in various alloy tubes is available from the Thermo Electric
Company. Another commonly used wire supplied by the Claud 8. Gordon
Company is insulated as follows: each strand is coated with phenol formal-
dehyde varnish and Fiberglas-impregnated with a silicone alkyd copolymer,
and the entire wire is Fiberglas-impregnated with a silicone alkyd co-
polymer.
Sound transmitters. Waterproof microphones are attached to pumps to
monitor bearing and check-valve noises.
8-5.3 Nuclear instrumentation in the HRE-2. The purpose of the nu-
clear instrumentation in homogeneous reactors is to provide neutron-level
measurement and the gamma monitoring of auxiliary process lines and
control areas for the detection of radioactive leaks (see Article 7—1.8).
Gamma radiation measurement. Gamma monitors for detecting process
leaks, manufactured by the Victoreen Instrument Company, consist of a
simple one-tube, three-decade logarithmic amplifier sealed within the
chamber head and a remote-contact-making meter and multipoint recorder.
These detectors can be remotely calibrated by exposing a radioactive source
on the actuation of a solenoid-operated shielding shutter. All channels are
460 COMPONENT DEVELQPMENT [crAP. 8
Fluorethene Insulator
.
Y O lNifrogen Gas
e
& .
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o TR
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LT
il
|
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RG 59-U Coaxial |
Cables :
i
s B Y
¥ . W 7 T %
\l {4
Kovar Seals g Sl i ~ \\ Positive Electrode \Signcl Electrode \Aluminum Housing
Brass Ground Rod
™Fluorethene !nsulator
1 0 1 2 3 4
Scale In Inches
Fia. 8-23. High-level gamma ionization chamber. Effective volume, 120 cm3;
electrode spacing, 1/8 in.; performance, 20 ua, chamber saturated at 100 volts at
radiation level of 3 X 107 r/hr; design temperature, 130°F.
duplicated, and control action is initiated only upon a simultaneous signal
from both channels to minimize false “‘scrams.” However, a signal from
either channel is annunciated. For monitoring control areas for personnel
protection, more stable and accurate vibrating-condenser types of elec-
trometers are used.
The cell air monitors, which provide an alarm in case of a leak of radio-
active vapor from the reactor system, are installed in an instrument cubicle.
Cell air is circulated through a 2-in. pipe from the reactor tank, past the
enclosed monitors, and then back to the cell. The blower is sized so that
only 5 sec is required for cell air to reach the radiation monitors.
A high-level gamma ionization chamber, developed at ORNL [56], is
used to measure cell ambient radiation levels up to 107 r/hr (Fig. 8-23).
This measurement is needed to evaluate the effectiveness of shielding, to
assay the rate of radiation damage to reactor components, to measure
radiation levels during maintenance operations, and to provide data for
future reactor designs. The chamber is of inexpensive construction and is
discarded upon failure.
8-5.4 Electrical wiring and accessories. Copper-clad compressed mag-
nesium-oxide spaced and insulated electrical cable is very desirable for
service in extremely high-temperature, radioactive, or wet areas because
no organic material subject to cracking and outgassing is used in the insula-
tion. A waterproof disconnect, designed to be broken remotely to permit
the removal of reactor electrical equipment, is used with this type of cable.
The electrical connectors are terminated inside the disconnect with a
multiple-header ceramic-to-metal seal, voids being filled with magnesium-
8-5] INSTRUMENT COMPONENTS 461
oxide powder. The outside guides are tapered to simplify remote main-
tenance. Long insulators are used on the connecting terminals to minimize
leakage currents after submersion. The cable is available in a varted num-
ber of conductors and sizes, from single to seven conductors in a copper
sheath, as wire sizes No. 16 AWG to 4/0 AWG, from the General Cable
Company. The hermetic end seals are available from the Advanced Vacuum
Products Corporation or Permaseal Corporation.
A compression seal designed around an inorganie material, magnesium
silicate, is used to seal wires at conduit terminations. These seals are
supplied by the Conax Company. A similar device but utilizing a glass-
to-metal seal is manufactured by the Stupakoff Ceramic and Manufactur-
ing Company.
For the windings used on the motion-sensing coils of instruments, 30-
gage anodized aluminum wire supplied by the Sigmund Cohn Company
has successfully withstood temperatures up to 300°C and radiation ex-
posure of 6 X 10'7 nvt fast neutron and 1 X 10% r gamma without failure.
The only electrical insulation on the wire is that afforded by the oxide
film on the aluminum. This wire must be handled carefully to avoid abra-
sion and is suitable only for low-voltage use. For lower temperatures, the
Ceroe magnet wire available from the Sprague Electric Company has been
used very sucecesstully.
162 COMPONENT DEVELOPMENT [cHAP. 8
REFERENCES
1. P. H. Harurey, Straight Through ITRT Core Model Test, USAT.C Report
CF-54-9-129, Oak Ridge National Laboratory, Sept. 22, 1954,
2. 1. Seiewaxk, Preliminary Destgn of Screens for the Inlet of the ISHR Core,
T'SAEC Report CF-52-10-181, Oak Ridge National Laboratorv, Oct. 18, 1952,
W. D. Bamxes and BE. G. Prterson, Trans. Am. Soc. Mech. Engrs. 73(3), 467
(July 1951).
3. L. B. Lesem and P. H. Harney, Scale-up of Mernate HRT Core, USAEC
Report ARECD-3971. Oak Ridge National Laboratory, Mav 7, 1954, L. B.
Lesem and I. Serewak, Aternate Core Proposal for the HRT, USAEC Report
CTF-54-1-80, Oak Ridge National Laboratory, Jan. 28, 1954,
4. ¥. N. PreBres and H. J. Garsrr, Studies on the Swirling Motion of Water
within a Spherical Vessel, University of Tennessee, Report 8-370, January 1956,
5. L. B. Lesesm et al., Hydrodynamie Studies in an Fight-foot Sphere Utilizing
Rotatron Flow, USAEC Report ('F-53-7-29, Oak Ridge National Laboratory,
July 20, 1953.
6. 8. TrvosuENko, Strength of Materials, 2nd ed. New York: D, Van Nostrand
Co., Inec., 1940. (Part I1, pp. 160, 162)
7. 8. Trvosuexko and J. N. Goopier, Theory of Flasticity. 2nd ed. New York:
McGraw-Hill Book Co., Tne., 1951, (pp. 59, 359}
8. 8. TrvmosuexNko and J. N, Goonier, Theory of Elasticity. 2nd ed. New York:
MceGraw-Hill Book Co.. Ine., 1931, {(pp. 412, 418)
9. I.. G. ALEXANDER, Fstimaiton of Heat Sources tn Nuclewr Reactors, A.1.
Ch. E. Journal 2: 177 (June 1956).
10. R. H. Crapyman, Analysis of Spherical Pressure Vessel Having an Fnergy
Source Within the Wall, USAEC Report ORNL-1987, Oak Ridge National Lab-
oratory, Oct. 26, 1954,
11. L. F. Brensor et al.. Welding J., N. Y., 35, 997-1006 (October 1956).
W. R. Garr, Nucleonies 14(10), pp. 32-33 (October 19306).
12. .. C. Movxyers, Long-term Run of Westingliouse 4001-1 Pump, USAEC
Report CF-57-9-1, Oak Ridge National Laboratory, Sept. 3, 1957.
13. R. B. KorsMEYER et al., in Homogenecous Reactor Project Quarterly Progress
Report for the Period Inding Jan. 31, 1955, USAEC Report ORNL-2493. Oak
Ridge National Laboratory, 1958,
14. H. A. Ru~prLL et al., I'nvestigation of Effect of Seal Configiration on Mixing
Flow and Radiation Damage tn HRT-Type Circulating Pumps. USALE.(C Report
CF-57-10-48, Oak Ridge National Laboratory, Oct. 10, 1057,
15. J. C. Movers, Long-term Run of Westinghouse 1004-1 Pump. USALC
Report CF-57-9-1, Oak Ridge National Laboratory, Sept. 3, 1957.
16. R. B. KorsMEYER et al., in Homogeneous Reactor Project Quarterly Progress
Report for the Period Ending July 31, 1957, USALC Report ORNL-2379, Oak
Ridge National Laboratory, Oct. 10, 1957. (p. 59)
17. R. B. KorsMuEYER et al., in [Homegeneous Reactor Project Quarterly Progress
Report for the Period Ending Jan. 31, 1958, USALEC Report ORNL-2493, Ouk
Ridge National Laboratory, 1958.
REFERENCES 463
18. H. A. RunpeLu et al., Tnvestigation of Effect of Secal Configuration on
Mixing Flow and Radiation Damage in IIRT-Type Circulating Pumps, USAEC
Report CF-57-10-48, Ouk Ridge National Laboratory, Oct. 10, 1957,
19. W, J. Finax and 1. Gra~ver, Final Reports on Union Carbide Nuclear
Company Contract No. W35X-31312, Phase 1, Foster-Wheeler Corp., Nov. 15
and Dec. 15, 1956.
20. J. C. Griess et al.. Solution Corroston Group Quarterly Report for the
Period Ending July 31, 1957, USAEC Report CF-57-7-121, Oak Ridge National
Laboratory, July 31, 1957. (p. 33 ff)
21. C. H. Secoy, Aqueous [Fuel Systems, USALC Report CEF-57-2-139, Oak
Ridge National Laboratory, Feb. 28, 1957,
22. C. Micurrson, ITRT Modified Pressurizer Design, USALEC Report CI-
56-5-165, Oak Ridege National Laboratory, May 25, 1956,
23. Boiler Construction Code, Section I, Power Boilers, American Society of
AMechanical ngineers (1956); ASA Code for Pressure Piping, B31.1-1935.
24, K. L. Haxso~n and W. E. Jausyax, An Fealvation of Piping Analysts
Methods, USALEC Report KAPL-1384, Knolls Atomic Power Laboratory, Aug.
10, 1955.
25. M. W. Krnrose Cosmeany, Design of Piping Systems. 2nd ed. New
York: John Wiley & Sons, Inc., 1956.
26. M. 1. Lu~pix, HRT High Pressure System Piping Line Deflections and
Reactions on Fquipment Nozzles, USAEC Report CF-55-8-83, Oak Ridge Na-
tional Laboratory, Aug. 10, 1955.
27. W. R. GavrL ct al., In Homogeneous Reactor Project Quarterly Progress
Report for the Period Ending Apr. 30, 1957, USAEC Report ORNL-2331, Oak
Ridge National Laboratory, Aug. 14, 1957, (pp. 22-25)
28. B. Drarrrand H. C. RoLurr, Design and Development of a ! 5-in. Tifanium
to Stainless Flange, USAEC Report CF-57-11-140, Oak Ridge National Labora-
torv, Nov. 27, 1957,
29. J. A. Harvorp, Development of the Pipe-line Gas Separator, USAEC
Report ORNL-1602, Oak Ridge National Laboratory, Nov. 2, 1953.
30. P. H. Haruey, Performance Tests of [TRT ['uel Solution Evaporator and
Entrainment Separator, USATC Report CF-534-10-531, Oak Ridge National
Laboratory, Oct. 13, 1954,
31. WestiNGgHOUsE ELEcTtric CORPORATION AND PENNsSYLVANIA POWER AND
LigrT Conmpany, 1957. [Unpublished.
32, 0. A. FarBrr, Bubble and Slug Flow in Gas-Liquid and Gas (Vapor)-
Liguid Solid Mixtures, Research Progress Report on Subeontract N.996 to REED
of Oak Ridge National Laboratory, 1957.
33. R. V. BatLey et al., Transport of Guases Through Liguid-Gas Mixtures,
USAEC Report CF-55-12-118, Oak Ridge National Laboratory, Dee. 21, 1955.
34. C. L.Segaser, HRT Entrainment Separator Design Study, USALCReport
CF-54-7-122, Oak Ridge National Laboratory, July 23, 1954.
35. R. &, Aven, IHTRT Recombiner Condenser Design, USAEC Report CF-54-
11-1, Oak Ridge National Laboratory, Nov. 1, 1954,
36. 0. A. Hovaen and K. M. Watsox, Chemical Process Principles, Vol. 111,
New York: John Wiley & Sons, Inc., 1947, (pp. 902-910)
464 COMPONENT DEVELOPMENT [cHAP. 8
37. J. A, Ransonorr and 1. Seiewak, in Development of Hydrogen-Oxygen
Recombiners, USAEC Report ORNIL-1583, Oak Ridge National Laboratory,
Oct. 22, 1953, (p. 40)
3%. P. H. Hawwey, [ligh-pressure Recombination Loop Progress Report, USAEC
Report CF-57-1-90, Ouk Ridge National Laboratory, Jan. 4, 1957.
39. J. A, Ransonorr and . Seiewax, in Development of Ilydrogen-Oxygen
Recombiners, USATIC Report ORNL-1583, Oct. 22, 1953, (pp. 48-56)
40. 1. K. Namna, Natvral Ciurculation Recombiner Report, USAEC Report
CF-56-9-27, Oak Ridge National Laboratory, Sept. 10, 1956.
41. P. H. Harrney, High-pressure Recombination Loop Progress Report, USAEC
Report CF-57-1-90, Oak Ridge National Laboratory, Jan. 4, 1957.
42. T. W. Lrrann, Design of Charcoal Adsorbers for the HRT, USAEC Report
CF-55-9-12, Oak Ridge National Laboratory, Sept. 6, 1955,
43. I.. B, ANpErsoN, Oak Ridge National Laboratory, 1955. Unpublished.
44. ). S. Cuuver and C. B. Granay, High-pressure Diaphragm Pumps for
Reactors, in Safety Features of Nuclear Reactors; Selected Papers from the 1st
Nuclear Engineering Science Congress, December 12-16, 1955, Cleveland, Ohio.
New York: Pergamon Press, 1957. (pp. 225-230)
45, C. H. GaBBanp, Diaphragm Feed Pumps for Homogeneous Reactors, 4th
Fngincering and Science Conference, Held in Chicago, Illinois, March 17-21,
1958. (Preprint 74)
46. R. BLuumsira ot al., Diaphragm Feed Pump Development Program Progress
Report, USAEC Report CI-56-10-114, Oak Ridge National Laboratory, Oect.
29, 1956.
47. Ohio State University, Union Carbide Nuclear Company, Contract
No. 81X-44934.
48. A. M. BiruuNgs, Control Valves for the Homogeneous Reactor Test, 4th
Nuclear Engineering and Science Conference, Held in Chicago, Illinois, March
17-21, 1958, (Preprint, 149)
49. A. M. Bruuinas, Life Tesis of Stem-sealing Bellows for HRT Valves,
USAEC Report CF-58-3-39, Oak Ridge National Laboratory, Mar. 17, 1958.
50. D. 8. Tooums ct al., in Homogeneous Reactor Project Quarterly Progress
Report for the Period Inding Jan. 81, 1957, USAEC Report ORNL-2272, Oak
Ridge National Laboratory, Apr. 22, 1957. (p. 34)
51. B. A. Han~narorn, HRT Sampler Development, USAEC Report CF-57-
1-87, Oak Ridge National Laboratory, Jan. 22, 1957,
52. R. VaNn WinkLE, Fuel Let-down Heat Exchanger, USAEC Report CF-54-
9-143, Oak Ridge National Laboratory, Sept. 20, 1954.
53. C. D. Zersy, Design of Smoothly Flowing Gas and Liquid JMaxtures,
TSAEC Report CF-51-10-130, Oak Ridge National Laboratory, Oect. 11,
1951.
54, D. 8. Tooms et al., in Homogeneous Reactor Project Quarterly Progress
Report for Period Ending Apr. 30, 1956, USAEC Report ORNL-2096, Oak Ridge
National Laboratory, May 10, 1956. (p. 32)
55. D. 8. Tooums et al., in Homogeneous Reactor Project Quarterly Progress Re-
port for Pertod Ending July 31, 1956, USAEC Report ORNL-2148(Del.), Oak
Ridge National Laboratory, Oct. 3, 1956. (p. 67)
REFERENCES 465
56. D. 8. Toowms et al., in Homogeneous Reactor Project Quarterly Progress Re-
port for Period Ending Jan. 31, 1957, USAEC Report ORNL-2272, Oak Ridge
National Laboratory, Apr. 22, 1957. (p. 35)