- e
-"‘f ’,‘\,' g -

. L e ORNL/TM-5104

   
  
   

 

 

A Study of Tritium Removal from Fusion
Reactor Blankets of Molten Salt
and Lithium-Aluminum

Jan B. Talbot

 

 

 
 

 

Printed in the United States of America. Available from
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road, Springfield, Virginia 22161
Price: Printed Copy $5.00; Microfiche $2.25

 

 

 

This report was prepared as an account of work sponsored by the United States
Government. Neither the United States nor the Energy Research and Development
Administration, nor any of their employees, nor any of their contractors,
subcontractors, or their employees, makes any warranty, express or implied, or
assumes any legal liability or responsibility for the accuracy, completeness or
usefulness of any information, apparatus, product or process disclosed, or represents
that its use would not infringe privately owned rights.

 

 

 

is

 
 

ORNL/TM-5104

a\

Contract No. W~T405-eng-26

CHEMICAL TECHNOLOGY DIVISION

A STUDY OF TRITTUM REMOVAL FROM FUSION REACTOR BLANKETS
OF MOLTEN SALT AND LITHIUM-ALUMINUM

Jan B. Talbot

 

 

NOTICE
This report was prepared as an account of york
sponsored by the United States Government. Neither
the United States nor the United States Energy
Research and Development Administration, nor any of
their employees, nor amy of their contractors,
subcontractors, or their employees, makes any
* warranty, express or implied, or assumes any Jegal
Yability or responsibility for the y, complet
or usefulness of any information, apparatus, product or
process disclosed, or represents that its use would not
infringe privately owned rights.

 

 

 

»d);

A thesis presented to the Graduate Council
of the Pennsylvania State University in
partial fulfillment of the requirements
for the degree of Master of Science

 

MARCH 1976

»

; - OAK RIDGE NATIONAL LABORATORY
I Oak Ridge, Tennessee 37830
operated by

~ UNION CARBIDE CORPORATION
. ' for the
“ ENERGY RESEARCH AND DEVELOPMENT ADMINTSTRATION

DISTRIBUTION OF THIS DOCUMENT {S UNLIMITED

 

 
 

.

 
 

 

&)

).

iii
ACKNOWLEDGMENTS

This study was carried out aé part of the Laboratory Graduate Parti-
cipation Program, which is conducted by Oak Ridge Associated Universities,
in cooperation with Oak Ridge National Laboratory, which is operated by
Union Carbide Corporation for the Energy Research and Development Admin-
istration. The writer wishes to thank G. C. Kyker, Head of the University

Programs Office, and D. E. Ferguson, Director, and C. D. Scott, Experi-

mental Engineering Section Chief, of the ORNL Chemical Technology Divi-

sion; whose support made this work possible.

The suthor wishes to acknowledge the advice and suggestions of P.
Barton, J. S. Watson, and F. J. Smith, who served as advisors fér this
study.

The lithium-aluminum samples were prepared by the Metals and Ceramics
Division under the supervision of J. H. DeVan. Chemical analyses were
performed by theAAnalytical Chemistry Division under the supefvision of
W. R. Laing. The mass spectrometer experiment was conducted by J. D.
Redman of the Chemistry Division. Special thanks are due J., F. Lénd;
who assisted with the operétion of the experiments. Much appreciation
is expressed fio Y. H. Callshan and M. G. Stewart, who edited the manu-

script, and to Janice Shanhoh, who typed the final edition. The drawings

- were prepared under the supervision of A. J. Farmer.

 

 
 

. »

 

 
 

4

)

ABSTRACT

The sorption of tritium by molten lithium-bismuth (Li-Bi, ~ 15 at.
% lithium) and solid equiatomic lithium-aluminum (Li-A1) was investigated
experimentally to evaluate the potential applications of both materials
in a controlled thermonuclear reactor. The Li-Bi alloy Was'proposed to
countercurrently extract tritium from a molten salt (Li2Bth) blanket.
However, because of the low solubility (< 10 ppb) at temperatures ranging
from 500 to TO0°C, the extraction process is not attractive.

Powell of Bfookhaven National Laboratory has proposed using solid
Li-Al as a minimum inventory blanket material. In the present study,
the tritium sorption was determined to range from ZLO-5 to 10—6 at. frac-
tion, which is in agreement with Powell's estimates. The quantities of
tritium sorbed seemed to be controlled by surface reaction and/or slow
internal diffusion.

The feasibility of the tritium recovery scheme suggested by Johnson
for the Princeton Reference Design Tokamaek was analyzed. The spray
disengager process to recover tritium from molten salt seems discouraging

due to the large Jjet velocity, the number of nozzles, and the droplet

size needed for mass transfer of tritium fluoride from salt.

 
 
 

4}

"

vii

TABLE OF CONTENTS

ACKNOWLEDGMENTS. .+ & & + o « o« o o o o o o o o & o o
ABSTRACT .
LISTOF TABLES . & &« &+ « o o o o o o & o s o
LIST OF FIGURES. . .
CHAPTER I. INTRODUCTION . . ¢ ¢« ¢ o & o o s o s o
CHAPTER II. REVIEW OF LITERATURE. . . . + ¢ ¢« ¢ « o o o s &
CHAPTER IIT. THEORY . . « « &« « & ¢ v o &+ o o &
CHAPTER IV. EXPERIMENTAL APPARATUS AND PROCEDURE.
Reagents.

Apparatus . . . . . ¢ ¢ « 4 s e s e e e e s
Li-Bi Sorption System. . . . « « ¢« ¢ ¢« ¢ « « « ¢ « &
Li~Al Sorption System.

Operational Procedures. . . . « « o ¢ « o
Li-Bi Sorption System. . . . . . .
Sampling Procedure .

Li~-Al Sorption System. . . . .

Analytical Procedure. . . . .« + o « o+ + = S
CHAPTER V. EXPERIMENTAL DATA. . + v o v v v v e v v e e o

Li-Bi Sorption System . . . . « . . . e,

Li-Al Sorption System . + v ¢ ¢« ¢ ¢ o ¢ 4 4 e e e s e
CHAPTER VI. DISCUSSION OF RESULTS . . . . . . . . .

Li-Bi Sorption System . . . . « . ¢« & &+ ¢ ¢ ¢ ¢ ¢ ¢ o & &

Li-Al Sorption System . . . . . « .+ « .« & S

CHAPTER VII. ANALYSIS OF THE TRITIUM RECOVERY SYSTEM FOR THE
PRINCETON REFERENCE DESIGN . . . . . . . . .

Description of the Process.

Disengager Analysis . + « &+ « & o o o o o s o s o s =

10
14
14

15
15
18

23
23
23
2L

26
28
28
32
37
37
38

L2
h2
45

 

 
 

 

 

viii

TABLE OF CONTENTS (Continued)

Cyclic Condenser AnalysisS. « « ¢ o o o o o o ¢ o o o o o o o«

Other Design Considerations. . . « « ¢« + ¢ ¢ o ¢ o o o & « &

CHAPTER VIII.

CONCLUSIONS AND RECOMMENDATIONS. . . « . + .« &

ConeluSionS. o o o « o o o » s o « o 5 o s o o o s o« s o o o =

RecommendationsS. « « « o o o » s ¢ o o 3 s o s o & s 8 o o o

BIBLIOGRAPHY.
APPENDIX A.

APPENDIX B.
 APPENDIX C.
APPENDIX D.
APPENDIX E.
APPENDIX F,
APPENDIX G.

APPENDIX H.

- - . * . - @ * L - * - . . . * * - . * - . - . . - e

THE COMPATIBILITY OF Li-Bi WITH Li2Bth. e e e o e

SAMPLE CALCULATIONS FOR Li-Bi~-TRITIUM SORPTION DATA
FOR SAMPLE NO. 2.7 AT 600°C. . « « &« « « &« « &

CALCULATION OF RESIDENCE TIME FOR MASS TRANSFER OF
TRITIUM FLUORIDE FROM A SALT DROPLET . . . . .

CALCULATION OF SPRAY DISENGAGER HEIGHT FOR SALT
DROPLETS OF VARIOUS SIZES (25) v & v ¢« v ¢ o o o o« o &

CALCULATION OF THE FREQUENCIES OF MOLECULAR COLLISIONS
(10) . . . . . . . - » . ® . . * . . s . . . . . . . .

CALCULATION OF MOLECULAR COLLISIONS WITH CONDENSER
WALLS - - . » . . o . * - * . - - o -* . . - * . - -

CALCULATION OF MEAN FREE PATHS OF TF AND HELIUM
COLLISIONS L4 - * - - . - - - . * . * - - - - - o o >

CALCULATION OF CYCLIC CONDENSER HEAT LOAD. + « + « «-®

6l
67
68
n
76

78
81

"
 

ix

LIST OF TABLES

Ieble
- I HYDROGEN REACTIONS WITH THE ELEMENTS (40). . . . . . . .
IT1. RESULTS OF Li-Bi METAL PHASE ANALYSES FOR TRITIUM.
IIT. RESULTS OF GAS-PHASE ANALYSES FOR TRITIUM CONCENTRATION.
| Iv. RESULTS OF Li-Al ANALYSES FOR TRITIUM AT L00°C . .
; V. TIME-INDEPENDENT RESULTS OF Li-Al ANALYSES FOR TRITIUM .
| VI. FLOW RATES AND CONCENTRATIONS FOR THE TRITIUM fiECOVERY
SYSTEM FOR THE PRINCETON REFERENCE REACTOR . . . . . .
VII. CHARACTERISTICS, ADVANTAGES, AND DISADVANTAGES OF PRESSURE
NOZZLES AND SPINNING-DISK ATOMIZERS (25) . . ..« « « + .« &
VIII. MOLECULAR AND WALL COLLISION FREQUENCIES AND MEAN FREE

PATHS OF He and TF IN THE CYCLIC CONDENSERS. . . . . .

»)

 
e e e

Figure

10
11

12

13

1k
15
16

 

LIST OF FIGURES

Slmpllfled Schematlc of a Controlled Thermonuclear Reactor

SystemD - - - . . - * ' a ‘e - » 2 . - - - . - - - » * . -
Apparatus for Study of Sorption of Tritium in Li—Bi Alloy

Reaction Vesgel for Studylng the Sorption of Tritium in
Ll-Bl Alloy » . . . . . . . . - . . . . . . . - . . - .

Initial Equipment Design for Studying Sorption of Tritium
in Li -Al AJ..loyo . - - . . . . . . . . . . . - - '. -

Revised Apparatus for Studying Sorptlon of Tritium in
Ll _Al All Oy' . . + . - . * . . - . . - . - . - . - . . -

Photograph of the7Equipment Used to Measure Tritium Sorp-
tion in Li—Al AJ.loy . - - » . . . - - - - - . . - - . . .

Sample Dissolution Apparatus for Tritium Analysis .

Page

Y
16

17
19
21

22

2T

Tritium Concentration in Li-Bi Samples at the Corresponding

Tritium Partial Pressure. « « o« « o o « o s « o » o

Tritium Concentration as a Function of Percent Li-Al
Sample Dissolved. . . & « o ¢ o ¢ & o ¢« o ¢ & 4 o o o . .

A Comparison of Sieverts' Constants for Aluminum, Lithium,

&nd Li-'Al Alloy . . - . . . . . . » . . . . . . . . .

Princeton's Reference Design Salt Blanket Processing
Sys tem > . - . . » L . - L] - - L] - - - . . * - . * * » -

Schematic of the Salt Disengager and Salt Trap. . . . . .

Residence Time vs Drop Diameter for Molten Salt Mass
Transfer. . « &« ¢ 4 ¢ o o o o o s o o o o o o s o s @

Schematic of the Cyclic Condensers. . . « « « ¢ ¢ o o &
Numerical Solution of Liquid Diffusion in a Sphere.

Ohnesorge's Chart (25) Showing Jet Breakup as a Function
of Reynolds Number and Ligquid Properties. . . . . « . . &

31

35

L0

43
46

148
52
67

69

%)

 
 

 

£

2)

CHAPTER I

INTRODUCTION

The feasibility of commercial fusion power reactors depends upon the
development of effeétive methods for containing and recovering tritium.
Difficult problems'are expected to be encountered in the handling,
recovery, and containment of the fuel inventory of a controlled thermo-
nuclear reactor (CTR) fueled with tritium and deuterium. Deuterium can
be obtained from natural fiaters; however, tritium, which does not exist
in useful concentrations in nature, must bé generated'by neutron bombard-
ment of lifhiumrcontaining material in a blanket surrounding the reactor
plasma. it is necessary to recycle tritium and deuterium from the exhaust
plasma and to recover bred tritium from its blanket system for subsequent
use as fuel..istringent limitations must be imposed on the use of tritiufi'
concentrations in the systém because of the direct effect fipon'the tritium
inventory, the tritium release rate to the environment, and the embrittle-
ment of structural materials by helium resulting from tritium decay.

Lithium—containihg materials havé_beén proposed fof a variety of
applications in CTRs: It is suggested in this study thatlmolten lithium-
bismuth (Li-Bi) alloy could be useful for extracting tritium from a CIR
‘breeding blanket consisting of a molten mixture of lithium and beryllium
fluorides. Of course, the applicability of such a recovery system depends
upon the equilibrium upteke of tritifim.by the Li-Bi alloy. Power (30)
has.suggested using a_sblid:lithium}aluminum (Li;Al) alloy ifi the tritium
breeding blanket. The alloy plus its aluminum structure would produce a

minimum neutron activation and a low tritium inventory. However, the

 
 

 

usefulness of the material is contingent upon its sorption of tritium
and its ebility to rapidly exchange tritium with a flush gas such as
helium, |

The objectives of thisrstudy were to evaluate experimentally'the
potentialrapplication of Li-Bi and Li-Al in a CTR. Thus, the tritium
solubility and thermochemical behaviqr of the lithium alloys were inves-

tigated. The Pennsylvania State University is not licensed to work rou-

- tinely with amounts of tritium greater than 100 uCi. Since samples of

more than ten times that amount were needed to attain meaningful experi-
mental results, this study was conducted at the Osk Ridge National
Laboratory (ORNL) as part of the Oak Ridge Associated Universities' Pro-
gram.

Another objective of the research was to analyze the blanket recovery
system proposed for the Princeton Reference Design CTR (21). In this con-
ceptual design, tritium is generated from g molten fluoride salt blanket.
The practicality of the blénket processing system was reviewedrin this
report by étudying each of the required process steps and estimating the

feasibility and equipment size involved.
 

CHAPTER II

é , REVIEW OF LITERATURE

=)

Many conceptual and engineering designs have been made for a CTR
(13,14,26,30,32). Most of the CTR concepts resemble the system shown in

FPig. 1. The thermonuclear reactions that release energy are:

T +—hHe + n, 17.6 MeV eq.

D ~ T +H, 4.03 Mev eq.
D - SHe + n, 3.27 MeV  eq.
3He - l‘lHe + H, 18.3 Mev : eq.
61i > JHe + bye. 4.0 MeV eq.

oY B Yo
+ + + + +
Vi oW

For the first generation of thermonuclear reactors, the deuterium-tritium
(D-T) reaction is favored because it releases one of the largest quanti—
ties of energy and its probability of occurrence (cross séction) is the

highest of the above reactions (19). In a D-T reactor, a small'percefi—;

)

tage of the D-T mixture fuses during its residence in the plfigfié'regiofi.
This fusion generates high-energy neutfons:which deposit heat.in the
surrounding blanket fluid. The'energy_is then transferred to a secondary
coolant fluid connected to a conventional steam cycle.

Tritium must be bred to fuel the reactor at a rate equal to,.or
greater than, the rate at which it is consumed in the plasma. The neu-

tron bombardment of lithium produces tritium by the following reactions:

6Li +n > hHe + T, eq. 6

»

Ii + n > 'He + n* + 1. eq. T

T

N

[ : Lithium must be included in the blanket material for breeding purposes.

Subsequently, tritium handling systems are needed to recover tritium

 
 

 

 

 

BLANKET
PROCESSING UNIT

 

 

P

 

ORNL DWG.

TURBINE
(OPTIONAL)

 

 

 

 

 

 

 

 

BLANKET-COOL ANT

 

 

 

 

 

 

 

 

 

 

75-8303

COOLANT-STEAM

 

 

 

 

 

HEAT-EXCHANGER HEAT- EXCHIANG ER
BLANKET FLUID COOLANT FLUID WATER
Figure 1. Simplified Schematic of a Controlled Thermonuclear

Reactor Systen.
 

 

"t

1)

»

d

 

from the blanket for recycling to the plasma. Although tritium breeding
is not necessary for the deuterium-deuterium (D-D) and deuterium-helium
(D~3He) fuel cycles, tritium will be %roduced by D-D reactions (Equa-
tion 2) and handling systems will still be required, although the prob-
lems will probably be less severe.

Low tritium concentrations must be maintained in the blanket mate-
rial by a tritium recovery system. Tritium has g half-life of 12.3 years

and undergoes radioactive decay according to the reaction

3

T > “He + e + 5.6 keV. eq. 8

The current Energy Research and Development Administiation (ERDA)
guidelines on radioactivity in effluents from light-water-cooled fission
fission reactors require (a) that the dose rate at the site boundary not
exceed 5 millirems/year and (b) that the annual averageuéoncehtration of
tritium prior to dilution in a natural body of water not exceed 5 x 10_3
uCi/liter (39). When considering a ~ 1000-MW(e) fusion reactor, these
guidelines imply (a) that the release of tritium into coolant water
should be limited to ~v 10 Ci/day and (b) that the amount discharged
through a stack (v~ 30 m high) should be limited to ~ 10 td 100 Ci/day

(37,38). However, current designs of fusion reactors attempt to limit

tritium release rates to a range of v 1 to 10 Ci/day. This limitation

constrains the concentration of tritifim in the blanket material. Trit-
ium, which is extremely mobile, will diffuse through all metal structureé
and heat transfer surfaces. Large'concenfirations of tritium in the
blanket would lead to high release rates; therefore, the blanket must be

processed to achieve the lowest possible concentration of tritium.

 
 

 

The thermonudléar power systems will process the blanket material
within the‘blanket loop, as shown in Fig. 1l; however, the choice of
blanket and coolant fluids will have an important effect in the tritium
recovery ééheme. The two reactor designs of interest in the present
study are those proposed by the ?rinceton Plasma Physics Laboratory (26)
and the Brookhaven Natiohal Laboratory (30). Princeton's Reference
Tokamsk produces 2030 MW of electric power. The blanket material chosen
to generate tritium is a mixtufe of lithium and beryllium fluorides
(LizBth). Helium fias chosen as a coolant to carry heat from the Li2Bth
blénket to the steam system. The Brookhaven conceptual design suggests
a solid LifAl allby as a blanket material in which tritium is bred and =a

helium coolant stream. This concept is advantageous because structural

~materials with very little long-lived activation (e.g. aluminum), which

are not compatible with-LizBth, can belused.

Récovery of tritium from molten Li BeF) is difficult because the
tritium concentration in the salt must be maintained at less than 1 ppm
to prevent tritium leskage. Watson (U41) has drawn several conclusions
from an evaluation of the tritium recovery process for the Li2Bth
blanket. Cold trapping and soiid sorbents are not attractive due to the
limited operating temperature range imposed by the salt and possible
tritium permeation through regenerator surfaces. Diffusion cells are not
practicai becfiuse of salt corrosivity and liquid film resistance. Counter-
currefit gas sparging with either helium or argon may be possible if a
suitable compromise between the sparge rate and corrosion can be made.

_ | -8 _
This necessitates that tritium pressures in the range of 10 to 10 1

O

 
 

 

 

 

 

.

1)

"

atm and tritium fluoride (TF) pressures in the range of 1072 to lo_l'l atm
be maintained.

In this study, the proposal examined is one in which LieBth,would
be contacted with an immiscible diffusion sink in a countercurrent liquid
extractor., A tritium getter, added to the molten metal, would form a
hydride to reduce the equilibrium activity of tritium and to obtain low
tritium concentrations in the salt phase. The contacting medium investi-
gated was Li-Bi, with lithium being the tritium getter. The tritium is
then recovered from the molten Li-Bi either by a precipitation process or
in diffusion cells.

The experimental apparatus used to determine the equilibrium distri-
bution of tritium at low concentration levels in molten Li-Bi was a modi-
fication of that utilized previously at ORNL for phase equilibrium studies
of molten salt and molten metal systems (12). The concentration of Li-Bi
compatible with LigBth was determined by using available thermodynamic
date (Appendix A). Lithium will reduce beryllium from the Li BeF) at
large concentrations and will subsequently form another immiscible phase.
A maximum concentration of 15 at. % lithium in bismuth was chosen for the
tritium solubility experiment; this molten ailoy is compatible with
LigBth at the temperatures observed. The proposed extractor_wofild use
8 lesser concentration of about 1 at. % lithium and operate at 900°K.

The process suggested by Johnson (21) in the Princeton Reference
Tokamek study offers another method for recovering tritium from LizBth.
The molten salt is sprayed continuously into eight towers which are fiain—
tained below 10'-LL atm and lodated around the reactor system. TF and

helium gases vaporize from the tiny droplets and are drawn through cold

 
 

 

 

traps, where all the TF is frozen out. The_salt is collected at the

bottom of each discharger and recirculated through the blanket. Period-

‘ically, the nitrogen-cooled traps are thawed, and liquid TF flows into

electrolytic cells, where it is eleétrolyzed to T2

.and.F2; ‘The tritium -
is recycled td the primary fuel loop. | | |

The tritium recovery scheme'fdr the solidrlithiumrcontaining blanket
proposed by Brookhaven (30) seems less ccmplex in coméarisén to the
LieBth recovery systems. The tritium bred in the Li-Al alloy diffuses
out of the solid, either into the vacuum region between the plasms and
the first wall or into the helium coolant stream. By letting the tritium
diffuse directly into the vacuum region, the tritium-concentrafion in the
Li-Al will eventually reach a steady-sfiéte value as it is geleased at
the same rate that it is bred. If thé resistance to tritium release is
sufficigntly small, the steady-state concentration will differ:little
from eqfiilibrium conditions. - If the vacuum region is maintained a.t'lo_6
torr tritium pressure (1 torr equals 1 mm Hg of pressure) and tfie residual
gas is assumed to be 100% tritium, the equilibrium atom fraction of trit-
ium in Li-Al is about 2 x.lO-6 (30). This corresponds to a tritium blan-
ket inventory of about 160 g (2 x 100 Ci). Since ~ 300 g of trifiium will
be burned déily in the plasma, 2 x lO—6 atom fraction represents less than
a day's inventory._ If the tritium inventory in the blanket is too large,
protium (normal hydrogen) could be used to scavenge the tritium. Finally,
the tritium is recovered, combined with purified D-T fuel from the plasma,
and recycled to the plasmna.

Alternatively, the tritium could diffuse out the Li-Al into the

helium coolant stream, where it is removed by absorption in a metal

 
 

»

)

u}

»

[ o]

 

 

hydride bed from which it is later recovered. The atom fraction of trit-

>

ium in Li~Al is estimated to be ~» 3 x 10 °, which is an order of magnitude
greater than the previous case (30). The tritium concentration in the
helium depends on the fiow rate of helium éoolant and the tritium diffu-
sion rate. Again, additions of protium céuld lower the tritium concen-
tration.

However,rthe difficulty of removing tritium from Li-Al depends uponr
both the equilibrium tritium concentration in Li-Al and the tritium
diffusion rate in Li-Al. An experimental study by Wiswalliand Wirsing
(43) tested the removal of tritium from granular forms of Li-Al, LiAlog,
and Li28103. The procedure was to flush helium through a bed of irra-
diated compounds at a controlled temperature in the range 400 to 600°C.
Tritium, generated by exposure to thermal neutrons, diffused out of a
sample and was carried to a tritium monitor. The data collected were

not successfully analyzed in terms of a physical model. Removal rates

were increased both by an increase in the helium flow rate and by addi-

tions of 1000 ppm of hydrogen to the helium; this shows that surface

sorption is important. Yet, the escaping rate increased with a decrease
in particle size, which indicates a8 slow diffusion within the alloy.
This would also result from surface sorption, for the same loading, and

surface resistance.

 
 

10

CHAPTER III

THEORY

The recovery of tritium from CTR materials depends on its distribu-
tion and leakage characteristics. These faétors are determined by tritium
solubility in the contacted materials, tritium diffusion rates through
reactor fluids and structural components, and the formation of stable
compounds.

The reaction for solutions of tritium in a metal can be firitten as

follows:

Ya) * ¥ Tate) = *(a) °- 9

where

dissolved in metal phase,

X(a)

T = tritium gas.
2(g) &

The equilibrium constant for the reaction is:
o xm@) _ Tem(a) Yxm(a)
1 1

Zz 2
a P a p
x{(4d) T2 x(4d) T2

’ eq. 10

where ‘
K = equilibrium constant,
a = activity of substance,

tritium partial pressures,

K
H
n

y = activity coefficient,

N = concentration.

 
 

1]

#)

solutions

pressures

il

W
il

Sieverts'

k

T

i

 

11

approaches zero, a and YXT(d) become constant. In dilute

X(d)

of tritium in metals, the relationship between solubility and

is given by Sieverts' law (27,33,36):

N, = k, P T, eq. 11

tritium concentration in the metal phase,

tritium partial pressure,
Sieverts' constant.

constant is exponentially dependent on temperature, as follows:

k =k _ exp(Q /kT) 12
s = kg exp Qs s eq.

material-related constant,
activation energy for the solution of tritium in the metal,

Boltzmann's constant,

absolute temperature, °K.

According to Cantor and Grimes (6), the solubility of tritium in molten

salt is related by Henry's law, which is expressed as follows:

where

k. , eq. 13

k, = Henry's law constant.

The permeation of tritium through bulk material is given by the

equation

 
 

 

12

Nj—

) B - exp(-Q/kT) , eq. 1k

where

£
i

flux of tritium through the interface,

A = area of the interface,

X = thickness of the interface,
p = tritium pressure on a side of the interface (Pi > po),
B = material-related parameter, -

Qp material-related parameter.
Tritides are readily formed since hydrogen and its isotopes react
with nearly eVery element. Table I illustrates the behavior of hydrogen

with groups of the periodic table.

 
)

)} i

TABLE I

HYDROGEN REACTIONS WITH THE ELEMENTS (L40)

 

» -

 

 

Period Elements Type of Hydrogen ‘Bond . Hydride Character

VIA 0, 5, Be, Te, Po Covalent Decomposable gases

VA N, P, As, Sb, Bi of liquids (except

IVA c, Si, Ge, Sn, Pb solid A1H3)

IITA B, Al, Ga, In, Ti

VIIA ¥, C1, Br, I, At Tonic with the hydrogen electro- Corrosive gases or
positive liquids

ITA Be, Mg, Ca, Se, Ba, Ra Ionic with the hydrogen electro- Saltlike (except

IA Li, Na, K, Rb, Cs, Fr negative noncrystalline BeHe)

IIB Zn, Cd, Hg Endothermic hydrogen occluder; Metallic; usually

IB Cu, Ag, Au, Ni, Pd, Pt no compound formation (except ductile

VIIIB Co, Rh, Ir, Fe, Ru, Os exothermic palladium)

VIIB Mn, Tc, Re

VIB Cr, Mo, W

VB Y, Nb, Ta Exothermic hydrogen occluder; Metallic; usually

IVB 71, Zr, Hf metallic or interstitial com—- brittle

IIIB Sc, Y, La,® AcP pound formation

 

®A11 lanthenides

bAll actinides

£T

 

 
 

 

 

14

CHAPTER IV

EXPERIMENTAL, APPARATUS AND PROCEDURE

Reagefits | -
| ihe bismuth was obtained from the Cominco American Company (99.9999%
purit&); The lithium metal was supplied.b& Fischer Scientific Company .
Just érior to loasding under an argon atmosphere, the pure lithium was cut
and c;eaned of oxide film. The Li-Al alloy was prepared by the Metals
and Céramibs Division of ORNL. The procedure consisted of wrapping known
amounts of lithium in aluminum foil, submerging the packets into a known
quantity df molten aluminum (99.999% purity) contained in a molybdenum
crucible, and continually mixing the alloy with a molybdenum stirrer. A
50-50 at. % mixture was then cast into 1/4~in.-OD rods (9). Each sample
was appfoximately l/h to 1/2 in. long and weighed about 0.5 g. The alloy

rods were thinly coated with a bluish oxide film. The intermetallic com-

~ pound Li-Al is & solid solution between 45 and 56 at. % lithium (18).

Li-Al displays & glaesslike brittleness, and its density has been deter-
mined as 1.725 g/ml at room temperature (2). The equiatomic composition
melts at 718°C.

All gases were of the highest purity commercially available. Argon,

which was used as the inert cover gas, was further purified by passage

through a titanium sponge trap; the lower section was held at 600°C for

the removal of oxygen and_water, end the upper poftion was held at about
206°C:for the removal of hydrogen. Tritium, obtained from the ORNL Isotopes
Di#ision, was supplied in 3/8-in. glass ampules, each containing 1 Ci in

a volume of 1 ml (pressure equal to ~ 324 torr).

 
 

 

»

.}

»)

[ 2]

»

 

15

Apparatus

Li-Bi Sorption System. Equilibration and tritium sorption were con-

 

ducted in a vessel of the type shown in Fig. 2. The apparatus has been
used previously at ORNL for phase equi}ibria studies of molten salts and
molten metal systems (12). Figure 3 illustrates the reaction vessel in
detail. The vessel was fabricated from a 22-in. length of 2-in.-0D
stainless steel pipe. quling fins welded to the exterior of the upper
section of the vessel served both to céol and to support the_féssel when
it was positioned in a well-type furnace, which heated 6 in. of the con-
tainer. A gas outlet tube was welded into the pipe between the furnace
support and the flange. The upper flange section was fitted with a 1/2-
in. ball valve, a thermocouple port, and a l/4-in.-diam molybdenum sparge
tube (v 10 to 20-mil wall thickness). A Cajon O-ring fitting at the top
of the épargé tube allowed raising and lowering. A Teflon plug, through
which the samplers were insertéd, was held in place by another O-ring,
which was connected to the top of the ball valve. The Li~-Bi alloy was
contained in a molybdenum crucible 6 in. long, 1-1/2 in. ID, and 1-3/kL
in. OD. The molybdenumrcfucible fitted loosely in the reaction vessel
as shown in Fig. 3. The appafatus was operated in a radiochemical hood,
which also provided secondary containment of tritium.

The temperature of the system was méasured by a calibrated Chromel-
Alumel thermocouple and recorded by a Brown potentiometric recorder. The
temperature of the systém was controlled with + 2°C by a Wheelco propor;
tional controller qperating from‘a control thermocouple, which was placed

against the exterior wall of the reactor vessel.

 
 

16

ORNL DWG. 75-5342R1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ar
T2 %( '
AMPULE LlQUIgOFSzt_'l_MPLE
_ T2 [ D | |
MONI!ITOR |
| H
éfl,fl ERMOCOUPLE
X md i
VAC < ] )
GAS SAMPLE
(vOL.~4.5 cc)
STAINLESS STEEL
VESSEL (VOL.-800cc)
Mo
CRUCIBLE
Meaved):
L \\\‘\\.:
Li-BI ALLOY fEEN

 

 

 

 

 

 

Figure 2. Apparatus for Study of Tritium in Li-Bi Alloy.

 
 

MOLYBDENUM
SPARGE TUBE
. GAS SAMPLE
PORT ——=
MOLYBDENUM -
CRUCIBLE
: in Li-Bi Alloy.

 

 

 

17

ORNL DWG. 75-8304R1
ARGON OR VACUUM

   
 
   

STAINLESS STEEL
FILTER-SAMPLER

CAJON O-RING FITTING

|~ BALL VALVE

 

~—THERMOCOUPLE

TEFLON O-RING

 

 

 

 

- N 8 8 ¥

 

 

ANSSNT

v

e—_i-Bi ALLOY

 

 

 

 

Figure 3. Reaction Vessel for Studying the Sorption of Tritium

 

 
 

18

The samplers were constructed as follows:
"The filter-type samplers were fabricated of stainless steel.

. The l-in.-long body was drilled from heavy-walled, 1/b-in.-

- OD tubing, leaving a 1/8-in.-thick shoulder on one end; the
wall thickness after drilling was about 30 mils. A 20-in.
length of 1/16-in.-0D capillary tubing was welded into the
shoulder to provide the_stem'for the sampler. The sampler
was completed by welding e disk of FELTMETAL fiber metal
(Huyck Metal Co., product No. FM 225), having a median pore
size of 20 p, into the open end of the body." (12)

Li-Al Sorption System. The preliminary sorption apparatus was con-
structed of Pyrex to minimize tritium permeatibn frém ££e_system. Figure
L4 shows a schematic of the equipment. Four Pyrex sample tubes were
attached by gfouna-glass joints to a Ub-ft-long by 1/2-in.-OD manifold;

a mechanicai vacuum pump was connected to one end of the manifold. Dow-
Corning high-vacuum greaée (No.'9TOV), & nonmelting silicone lubricant,
was sparingly applied to the ground-glass and stopcock joints. High-
vacuum stopcocks were used throughout the system. The pressure of the
system was measured by a Virtis McCloud mercury manometer (0.005 to 5.00

3

torr) and a Hastings vacuum gauge (10 - to 1 torr).

Each sample tube was positioned in a 1-1/4-in.-ID clamshell furnace.

The temperature of each semple was measured by a calibrated Chromel-
Alumel thermocouple and indicated on a Doric Digital Thermocouple Indicator
(No. DS-300) (-50 to +1350°d). The temperatures were controlled within
+ 2°C by a Wheelco proportidnai controller operating from a control
thermocouple placed against a copper shield inside each furnace.

" The tritium leakage from the ground-glass joints and vacuum stop-
cocks was excessive at the l-torr tritium partial pressure involved.

Although glass joints proved to be adequate for previous ORNL studies of

tritium sorption in lithium, the resulting errors became significant when

 
 

 

n

v

)

")

[ 2

19

 

ORNL DWG. 75-8300R1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4! - o“
420D, l

< & - T=VACUUM
HASTINGS

GAUGE ALL HIGH GROUND l

VACUUM {1F GLASS i 1) TO McCLOUD
STOPCOCKS JOINTS PRESSURE
—] fe—1/2%0.D. GAUGE
|0ll
14"
/ -
[ l § [ |z- % I78"'0.D.
U 8" [/ 1 U THERMOCOUPLE
¢ WELL
J [/ INSULATION
: ABOUT 1/4"iD.
CLAM-SHELL
FURNACE
I"0.D. Cu TUBING
6"LONG

Figure 4. 1Initial Equipment Design for Studying Sorption of
Tritium in Li-Al Alloy.

 
 

 

 

20

‘materials with low tritium uptake fiere used. - Thus, a more reliable stain-

less steel system was built.

Figure 5 shows a schematic of the revised tritium sorption system
used in this study. The pumping system had been used previously at ORNL
as part of a Sieverts' apparatus for obtaining measurements of equlllbrlum
hydrogen isotope Solubllltles in lithium (35). This pumping system con-
sisted of a mechanical pump coupled te a Consolidated Vacuum Corporation
oil diffusion pump. The pressure measurement instrumentS‘included‘twe
Wallace and Tlernan prec1s10n pressure gauges, Model FA160 (O to 20 torr)
and Model 62A-LD-0800 (0 to 800 torr), and a Hastings vacuum gauge (10 -3
to 1 torr). The sorption system conSisted of four 1/2-in.-0D by l4-in.-
long quartz sample tubes connected to a,3—ftflong manifold. The manifold
was constructed of 1l/k-in. stainless steel.tubing. Each quartz tube was
lined with a 10-in.-long by 3/8-in.-OD thin-walled (about 10 mil) stain-
less steel tube. A Cajon O-ring fitting connected each quartz tube to a
Hoke vacuum valve, which was attached to the sorption manifold by another
O-ring joint. Hoke vacuum valves were used throughout the system. Figure
6 shows a photograph of the equipment.

Each sample tube was positioned in a-l—l/héin;fID clamshell furnace

by raising a lab-jack which had been placed underneath each furnace. The

temperature of each sample tube was measured by a calibrated Chromel-

Alumel thermocouple and recorded by a Brown potentiometric recorder. A
Wheelco proportional controller regulated temperatures within + 2°C. A
control thermocouple was placed against a copper shield inside each fur-

nace.,

-

 
[ }]

 

")

*)

 

[}

W

Li-Al Alloy.

 

X

  

TRITIUM
ADDITION

 

 

 

 

 

 

 

 

 

VACUUM
'MANFOLD

PRESSURE GAUG

 

 

 

 

 

21

. ORNL DWG. 75-8302R1

JA
S

 

 

 

 

 

X

 

 

 

 

     
  
 

 

 

 

 

' QUARTZ TUBES LINED
 WITH STAINLESS STEEL,
CONTANING ~ Li-Al

TUBE
FURNACES

'LAB-JACKS

 

| ~ Figure 5.

Revised Apparatus for Studying Sorption of Tritium in

 
 

 

 

PHOTO 0072-75

 

 

kgl

Photograph of

the Equipment Used to Measure Tritium Sorption

-in Li-Al Alloy.

cc

 
 

 

»

»

.

*)

"

"

 

23

Operational Procedures

Li-Bi Sorption System. About 600 g of bismuth and 3.47 g of lithium
(v 15 at. %) were loaded under an argon atmosphere into a molybdenum cru-
cible, which was placed inside the reaction vessel. The upper flange
section was bolted into place. To test for leaks, the vessel was pres-
surized with argon. After ensuring that no leaks were present, the sys-
tem was heated to 600°C to melt the Li-Bi for sample analysis. (See

Sampling Procedure section.) The molybdenum sparge tube was lowered into

 

the molten metal, and argon was bubbled through’the Li-Bi. The tritium
ampule was attached to the sparge tube; the system was evacuated to about
0.1 torr; and the seal within the ampule was broken. To break the glass
seal, a small metal bar was placed inside the ampule before attaching it
to the sparge tube. Then a magnet was fised to pull the bar through the
seal, releasing the tritium. Argon was subsequently passed through the
sparge tube to sweep the residual tritium into the Li-Bi alloy; the total
system pressure was thereby increased to about 3 psi. Throughout the
experiment (except during sampling), the system was kept under a 1- to
5-psi staticrargon pressfire. A period of at least 24 hr was allowed to
attain equilibrium at each temperature (500, 600, or T00°C). Pairs of
liquid and gas_samples were removed for analysis.

Sampling Procedufé. Each sampler was polished with emery paper‘
before use. The stem of the sampler was then forced through a hole in
the Teflon plug and connectéd to a flexible tube which leads to a mani—
fold supplying both,argon and vacuum. The sampler was placed in the upper
chamber of the ball valve, and argon was flushed through the sampler and

chamber for several minutes. Subsequently, the Teflon plug was inserted

 
 

2l ' ‘ é
into the O-ring fitting and tightened. The ball valve was then opened
and the sampler, with argon flowing through it, was lowered and positioned
in the liquid alloy.' The flow of argon was cohtihued for 2 to 5 min while .
the sampler was heated’to the temperature of the alioy. The argon flow

was stopped, and a vacuum was applied to the sampler. Li-Bi rapidly -

 

- filled (< 10 sec) the samplér and solidified in the cool part of the

capiliary stem, thus sealing the sampler. The sampler was then drawn into
the upper chamber, afid the ball valve was closed. The outside of the
filled sémpler was carefully polished with emery cloth, and the stem
and fiiter ends were removed with tubing cutters. The remaining part of
the sampler containeci gbout 2 g of Li-Bi. The metal sample was dissolved
in nitric acid, and the solution was analyzed for tritium.-

Gas-phase sampling involved first inducing a vacuum ofi.the L .5-ml- .
volume gas sample tubing. The sampler was filled by opening a valve to
the vessel and releaéing the gas. The valve to the reaétion vessel was
then closed, and the gas sample was slowly flushed to the analysis system
by using argon contéining a trace of hydrogen as a cérfier-gas. For trit-
ium concentrations below 5 x 103 uCi/m3, the vapor phase was analyzed by
a Triton monitor (Johnston Laboratory, Inc., Model 1055 B). For higher
tritium concentrations, the tritium was oxidized at 600°C on qu and
trapped in water bubblers. Samples of the bubbler fluids w;re énaiyzed
by liquid secintillation. | |

Li-Al Sorptién System. The preliminary glass apparatus'was operated *
as described below. One rod—éhaped Li-Al semple was loaded uhder an inert
atmosphere into each Pyrex tube. A vacuum stopcock was attached to each

sample tube and closed also under an inert atmosphere. The sorption
 

 

0

*

*)

»

»

 

2>

manifold was evacuated and checked for leaks. The sample tubes were
fastened to the manifold, and the total system was éumped downuto about
10™2 torr to remove any residual gas.

After ensuring that there were no leaks, the sample tubes were posi-
tioned in the furnaces, heated to about 400°C, and continually evacu-
ated, as the Li-Al outgassed, until the system pressure remained steady.
Tritium was added as described in the Li-Bi sorption experiment. Usu-
ally, at least 24 hr was allowed for the Li-Al samples and tritium to
equilibrate. Finally, the sample tubes were quickly cooled with a flow
of air to ambient temperature and the samplés were removed for analysis.

The procedure for operating the stainless steel system was similar
to that used for the Pyrex equipment. A sample was 1oaded into each
stainless~steel-lined quartz tube under an inert atmosphere. The sample
was either used in rod form or was crushed into a powder (< 20 mesh)(
The vacuum valve was attached to the tube and tightly closed under an
inert atmosphere. The pumping system and sorption manifold were evacu~
ated. After ensuring that no leaks were present, the samplg tubes were
fastened to the evacuated manifold. Then the entire system was pumped
down tQ approximately J.O-2 torr to remove any residual gas. Again, the
system was tested for leaks, and the sample tubes were positioned in the
furnaces and heated. The system was continually evacuated until the
pressure remained steady. Tritium was gdded to the sorption system from
a glass ampule. The amounts of tritium used ranged from 1 to 16 Ci. The
Li-Al samples and tritium were allowed to equilibrate for at least 24 hr
at temperatures ranging from 400 to 600°C. After the samples had cooled

to ambient temperature, they were removed for analysis.

 
 

26

Analytical Procedure

The Li-Bi and Li-Al samples were analyzed by dissolving them in
nitric acid and counting a dilute portion of the résulting solutions by
rliquid scintillation. Figure 7 shows the apparatus uséd in the dissolu-
tion prdcess. A sample waé placed in a -300-ml reaction flask. .After an
argon sweep gas had been established, a gquantity of warm TB%Initric acid
in excess of the amount necessary to react with the sample was poured into
the flask. As the sample dissolved, the released tritium was oxidized by
hot Cu0 (600°C) and captured in water bubblers. A trace of hydrogen was
added‘to the argbn to continuously flush tritium from the CuO bed and
tubing walls. Since the granular Li-Al samples resacted violently when
nitric acid was added, a modified technique was used to dissolve’the
crushed samples. A sample was placed into the reaction flask, and water
was slowly sprayed from g syringe to start the dissolution. Once the
reaction was controlled, nitric acid was added and the aliguots were
énalyzed. The gas-phase samples were also swept through the Cu0 bed,

and the tritium was trapped in the water bubblers. About 90% of the oxi-

dized tritium was captured in the first bubbler; thus, essentially all

the tritium was trapped by two bubblers in series. The tritium monitor
did not register above background tritium in the gas exiting the second
water bubbler.

Diluted aliquots from the reactiofi vessel afid the water bubblers
were analyzed by conventional liquid scintillation techniques. The scin-
tillation solution recipe was:

12 g PPO (2,5-diphenyloxazole)

0.3 g POPOP (l,h-pi§72(5—phenquxazolyl)benzene)

2010 ml of toluene
990 ml of Triton X-100 (an emulsifier product of Rohm and Haas)

1.}

 
0

s

»

>

"

 

 

27

One milliliter of the sample solution was mixed with 10 ml of the secintil-
lation counting solution. The tritium in each solution was detected by

a Packard Model 5T4 Tri-carb scintillation spectrometer, which had an
efficiency of about 20%. Samples were also analyzed by a similar‘method

by the ORNL Analytical’Chemistry Division.

ORNL DWG. 75-5344

 

VENT

 

REACTION
FLASK

¥.°

WATER BUBBLERS

 

 

Figure 7. ©Sample Dissolution Apparatus for Tritium Analysis.

 
 

 

28

CHAPTER V

EXPERTMENTAL DATA

Li-Bi Sorption System

The analytical résulfs in Teble II and Table III éhow that the quan-
tities of tritium sbrbédby'molten-Li-Bi wéfe very low. 'Because of the
diffusion of tritium thrdugh fhe stginless steel reactor and the leakage
during sampling, the fidtal_amodnfis of tfitium continuously decreased from
the initial_l Ci add.:i.t:'.on.to'a.'bc_:'fi:t:f-il..o_h Ci. ‘Therefore, the solubility of
tritium in Li-Bi ranged frofi.afidut 0.1 to 0.01 ppb, respeéti%ély.  Multi-
ple metai;phase samples were taken to_éfieék the ;eproducibility of the
sampling and analysis téchniques, However,.SQmples 2.1 to 2.7 were -
exceptions, and the values in Table II représént,only'one concentration
value rather thafi an average of several values as do the remainder of
samples., Since the tritium concentration in the'gas was substantially
greater than that in the Li-Bi, crcss—cofltaminatipn fias found from using
one Cu0 bed and contaminated bubblers.. Conseduently; the lofieét concen-
tration value was used for the first seven sampies.. For fihe rest of the
samples, a separate catalyst bed was fised for each phase analfisisand
all glassware was carefully cleaned between runs.“Réproducibilify of
the gas-phase analyses in Table III was éhecked by a tritium monitor fit |
levels of less than 5 x lO3 uCi/m3.

-The idegl gas law was applied to determine tritium partigi pressures
above the Li~Bi phase. Data were taken at 500, 600, and T00°C. How-
ever, most of the simultaneous gas and metal sampling was done at 600°C.

Figure 8 shows all the date points and a least-squares fit of the data

at 600°C. The equation represented by the straight line is:

 
 

TABLE II

 RESULTS OF Li-Bi METAL PHASE ANALYSES FOR TRITIUM®

 

 

 

Sample | Temp Sample Wt Tritium Concentration in Li-Bi

No. (°c) (g) dpm/ml x 10° Ci g ppb at. %
2.1 600 1.9409 78.03 1.645 x 10-6 1.70k x 10~10 0.0878  6.057 x 10~7
2.2 600 1.7661 32.9 T7.409 x 1077 T.676 x 10~7 0.0435 3.001 x 10”7
2.3 500 . 1.9991 267 6.013 x 1078 6.229 x 10710 0.3129 2.159 x 1076
2.4 600 2.1573 107 2.409 x 107 2.496 x 10710 0.1157 7.982 x 1077
2.5 700 1.9043 32.7 7.365 x 10™7 7.630 x 10”11 0.0L401 2.766 x 10”7
2.6 500 0.8304 11.09 2.498 x 10-7 2,588 x 10~11 0.0312 2.152 x 10~7
2.7 600 1.8375 12.89 2.903 x 10-7 3.008 x 10~11 0.016k 1.131 x 1077
2,8A 700 1.8659 2.98 6.712 x 10~8 6.954 x 10-12 0.00373 5.111 x 10~8
2.8B 2.1041 2.16 4.865 x 10”8 5,040 x 10712 0.00239 ’
2.9A 500 2.0251 2.99 6.734 x 108 6.976 x 10~12 0.00345
2.98 2.3340 2.92 6.577 x 10~8 6.81% x 10712 0.00292 1.971 x 10~8
2.9C 2.3196 2.19 4.932 x 10~8 5.106 x 10712 0.00220
210A 600 2.1038 8.00 1.80 x 107 1.865 x 10-11 0.00886
210B : 1.90k41 4,9k 1.113 x 107 1.153 x 10~ 11 0.00606 4.953 x 108
210C 1.6492 %.68 1.054 x 10-7 1.092 x 10-11 0.00662
211A T00 2.1793 9.93 2.236 x 10~7 2.316 x 10711 0.01063
211B 2.2471 3.91 8.806 x 1078 9.123 x 10-12 0.00406, 6.821 x 1078
211C 1.51h7 9.72 2.189 x 1077 2.268 x 10711 0.01497
3.1A 500 . 1.5229 A 3.68 8.288 x 1078 8.586 x 10-12 0.0056h} 2.877 x 10-8
3.1B 2.0795 2.hoT 5.421 x 10-8 5.616 x 10~12 0.00270 .
3.2A 700 2. 042k 21.LY 4.828 x 10~7 5.002 x 10-11 o.oehs} 1.192 x 10-7
3.2B 2.0452 - 9.593 2.161 x 1077 2.239 x 10711 0.0109 '
3.3A 600 2.4211 . 5.73 1.291 x 10~7 1.337 x 10-11 0.00552 3.943 x 108
3.3B 2.0520 5.20 1.171 x 1077 1.213 x 10711 0.00591 '

 

®Sample calculations of values appear in Appendix B.

6c

 

 
TABLE III

 

RESULTS OF GAS-PHASE ANALYSES FOR TRITIUM CONCENTRATION®

 

Tritium Concentration in Gas Phase.

 

 

 

 

Sample Temp By Liquid Scintillation By Tritium Monitor T, Partial

No. (°c) (dpm/m1) (uCi/m3)b i g Preszsure (torr)

2.1 600 1.131 x 207 4,528 x 1072  h.691 x 106 1.059 x 1072

2.2 600 1.941 x 106 T.772 x 10~3 8.052 x 10”7 1.819 x 1072

2.3 500 1.802 x 107 7.215 x 10-2  T.475 x 1070 1.495 x 1071

2.4 600 3.57% x 10° 1.431 x 102 1.483 x 1076 3.349 x 1072

2.5 700 9.730 x 10 3.896 x 10" 4,036 x 107!  1.016 x 1072

2.6 500 5.011 x 106 2.002 x 1072 2.0Th x 10'6 4,148 x 1072

2.7 600 4.778 x 10° . 1.913 x 1073 1.982 x 1077 L.WTT x 1073
4.9 x 103 1.306 x 10-3

2.8 700 1.480 x 105 5.926 x 1073 6.139 x 1007 1.545 x 1072

2.9 500 2,629 x 10° 1.053 x 10-3  1.091 x 1071 2,182 x 1073
3.9 x 103 1.037 x 10~3

2.10 600 1.726 x 10° | 6.011 x 10~ 7.243 x 100 1.636 x 10™>
2.5 x 103 6.665 x 10-l

2.11 700 9.854 x 1oh 3.946 x 10~  4.088 x 10'8 1.029 x 1073
8.0 x 103 2,128 x 10~

3.1 500 6.525 x 10" | , 2.613 x 107%  2.707 x 10~ 5.4k x 1077
9.75 x 10 2.594 x 10~

3.2 700 9.246 x 10" 1.4 x 10° 3.702 x 10‘2 3.835 x 1070 9.654 x 107"

| 3.724% x 10~ o
3.3 600 1.680 x 10° 5 6.727 x 10°%  6.969 x 108 1.57h x 1073
2.05 x 10 5.466 x 10"

 

aSample calculations 6f values appear in Appendix B.

bTritium monitor is useful for tritium concentrations of < 5.0 x 103 I-ICi/m3 (¢<1.33 x 10-3 Ci).

0t

 

 
 

31

 

 
 
 
    

 

 

 

g ORNL DWG. 75-8301R1l
I I
_ P=472x 108 N; !-2°
A 500°C
L. 0800°c
a 700 °C
L
x
>
0 101
@10
0 4
o
-
g
—
a
5 <
a
=
e
@
'._
10-3
0-4 1 I
10708 10-7 10-6 10-8
: TRITIUM CONCENTRATION ( at. % T) IN Li-Bi
i j Figure 8. Tritium Concentration in Li-Bi Samples at the Corre-
' sponding Tritium Partial Pressure.

 
 

 

 

6 . 1.288

P f-thl6 x 10 fNT > ea, 15
2 . , ' x
where
Pp = tritium partial pressure above‘the'Li-Bi,'torr,
N, = fraction of trltlum 1n the L1-B1, at. %.

From statistical analy51s, the data at 600°C fall within the 957 confl-'
dence interval which is 1.288 + 0.535 (1.823 to 0.753) for the slope of

the line.

Li-Al Sorption System‘

The tritium sorption'data fér Li;Ai afe ;hown.in Tables Iv and;v.'
The time-dependent data of Table IV at'h06°0'wéré'm§asured'fihen the sys-
tem pressure was not remaining}steadyk The 1éakage'probl§m Wés'résolved,
and constant-pressure measurements wefefifiaken'(see Table V). Aléo,.the
most reliable data points are presenfied in'Table V..‘Partial dissolution
of Li-Al samples shows that the concentratlon of trltlum decreases as a
function of dissolved Li-Al (Table IV) Flgure 9 shows the data. graphl-
cally.

The limited data have noticeable discrepanéies;,hoWevér, the_tritium
concentration in the rod samples range frdm 0.0i fib-filwt bpm for tritium
pressures of 0.14 to 5.42 torr, respectively. Thé‘cohcentfation of
tritium was generally higher in most of the powdered samples.

The chemical properties of Li-Al were fioré complex than was initially
enticipated. According to the phase diagram (18); Li-Al forms an equi-
atomic homogereous solid solution. Yet, during heating of the samples,

some materisl volatilized. A ring of a shiny, metsllic silver substance

 
 

RESULTS OF Li-Al ANALYSES FOR TRITIUM AT 400°C

 

 

TABLE IV

 

 

Sample

Tritium Concentration in Li-Al

 

 

Sample Time Pressure (torr)
No. (days) Initial Final Wt (g) dpm/ml wt ppm at. %
Al 1 1.76 © 0.66 1.17 0.545 6.60 x 10° 0:565 %.305 x 10°%
Al 2 2.75 0.66 2.18 0.455 1.25 x 1079 1.282 9.765 x 107"
AL 3 5.78 0.66 2.37 0.450 7.6% x 10° 0.792 6.035 x 10~
281 1 0.95 1.36 1.06 0.78 1.1% x 1070 0.682 5.195 x 10"
281 2 3.75 1.36 3.40 0.79 h.22 x 100 2.661 2.027 x 1073
2A1 42 0.89 1.36 1.02 0.58 2.37 x 107t 19.07 1.453 x 1072
Li~Al Partial Dissolution Results
Percent Sample
Dissolved

Al 2.1 5.92 1.20 5.42. 0.8036 13.2 3.96 3.04 x 1073

Al 3.2 5.92 1.20 5.42 0.8968 15.7 3.53 2.70 x 1075

AL 1 5.92 1.20 5. 42 1.7018 49.8 1.39 1.06 x 1073

Al 3.1 5.92 .1.20 5, Lo 0.6110 68.8 3.22 2.64% x 1075

AL 2.2 5,92 1.20 5,42 0.5050 100.0 1.07 8.18 x 107

 

aPowder. '

€e

 

 
TABLE V

TIME-INDEPENDENT RESULTS OF Li-Al ANALYSES FOR TRITIUM

 

 

 

 

 

Sample Temperature Sample Wt Pressure Tritium Concentration in Li-Al

No. (°c) (g) (torr) wt ppm at. %
L AL 2 500 0.46 0.52 4.11 3.14 x 1073
4 A1 3 500 0.48 0.52 2.08 1.59 x 1075
3A1 1 550 0.458 0.1k 0.013 9.96 x 107
3 A1 3% 550 0.413 0.1k 0.067 5.14 x 1077
4 Al 1 550 0.39 0.53 0.136 1.04 x 107"
b a1 4% 550 0.50 0.53 33.29 2.36 x 1072
3 AL 2 * 600 0.534 0.13 0.158 1.21 x 102
Most Reliable Data
5 A1 1 Loo 0.35 0.032 0.343 2.62 x 107"
5 Al 2 450 0.37 0.0325 0.467 3.58 x 107
5 Al 3 500 0.29 0.029 0.513 3.92 x 107"
5 A1 4 550 0.29 0.028 1.086 8.32 x 10
aPowder.

i
o ¢

RE

 

 
 

 

LY)

"

¥}

1072

3
o

TRITIUM CONCENTRATION (at. %T)

o4

35

o ORNL DWG. 75-8294R1
| I I I

 

 

 

 

1 ] ] 1
0 20 40 60 80 100

% Li-Al SAMPLE DISSOLVED

 

Figure 9. Tritium Concentration as a Function of Percent Li-Al
Sample Dissolved.

 
 

36

condensed on the cooled portion of the quartz sample tube. Initially,
stainlessfsteel liners were not inserted in the sample tfibes to contain
the Li-Al; the quartz tubes were attacked and cracked by the substance.
Silica compounds, such as quartz, are rapidly attacked by molten lithium
(15); therefore, it was suspected that excess lithium was present. To
analyze the constituents of the volatilized material, a time-of-flight
mass specffometer experiment was conducted by John Redman of the ORNL
Chemistry Division. Several Li-~Al samples were afialyzed both under -
vacuun and with a pure hydrogen flow. The‘temperature of the sample
ranged from 400 to 650°C; however, no lithium~containing vapor species
were observed. This behavior needs to be verified before Li-Al is

selected for a CTR blanket material.
 

 

o)

"

*l

.

37

CHAPTER VI

DISCUSSION OF RESULTS

Li-Bi Sorption System

 

The solubility of tritium in molten Li-Bi (v 15 at. % lithium) was
determined to be less than 10 ppb at temperatures ranging from 500 to
700°C. Therefore, an extraction process based on this alloy would not
be feasible. |

The pressure-concentration relationship of Equation 15 does not
correspond to Sieverts' law (Equation 11) or Henry's law, which states
that the tritium partial pressure would be directly proporfional to its
concentration in the solution. If data followed Hefiry's law, the error
of the slope could be due to impurities in the metal. However, formation
of intermetallic Li-Bi compounds could cause a slope between 1 and 2. A
temperature dependence cannot be determined from the scatter of data from
Fig. 8. Further experiments would be needed to provide these correla-
tions. OSince the data clearly show that the proposed process is not
practical, no further experiments were made in this ares.

With appropriate egquipment alterations, the leakage rate of tritium
could be reduced and the sampling technique could b€ improved. Neverthe-
less, at such low solubility levels, the“sensitivity of the liquid scin-
tillation counting of samples could not be increased to enhancé'the
accuracy of the data. Thus it was concluded that, due to the low sorp-
tion of tritium in Li-Bi, the proposed extraction process would not
suffice as a tritium recovery method for a CTR molten salt blanket.

Further experiments are not likely to alter these conclusions.

 
 

 

38

One reason for the low solubility of tritium in Li-Bi is that the
lithium present is bonded so strongly with bismuth (18) that lithium
tritide is not easily formed. It has been suggested that Li-Pb, which
is chgmically similar to the Li-Bi ailoy, be used for neutron shields
and collimators (15). Previous studies suggest that this material is
potentially useful because it is-relatively inexpensive, easily handled
and fabricated, and stable in air at temperatures over 200°C and neutron
fluxes of the order of 1012 neutrons/cm2 sec. But, it was also consid-
ered useful because it was assumed that the tritium produced would be
bouna chemically, as lithium tritide, within the Li-Pb. This is doubt-
ful due to the low solubility of tritium in Li-Bi which was determined
in this investigation. This study could also be relevant to some pro-

posed uses of Li-Pb in fusion reactors.

Li-Al Sorption System

The tritium sorption data in Tables IV and V, although not conclu-
sive, do provide some insight into the relatively complex nature of Li-Al.
The limited amount of data and the apparent inconsistencies make corre-
lations of temperature, pressure, concentration, and sorption rate
impossible. Tritium sorption rates were low, and equilibrium probably
was not achieved in many of the experiménts.

The partial dissolution experiment does indicate that the loading
was determined by sorption ra£é rather than equilibrium, but it does not
explain the manner inlwhich the sorption occurred. The tritium concen-
tration decreased as more of the total sample was dissolved, the concen-
tration being higher at the surface. BSorption may be controlled by

either surface reaction or slow diffusion, or both. Surface adsorption
 

 

»

*

39

could be very important if the solid blanket material were to "powder"
under irradiation; alsc, diffusion by grain‘fioundarieé could be signifi-
cant. The sorption time does seem to be several days. This indicates
that a desorption time would be also several days, thus increasing the
tritium inventofy significantly.

The tritium solubilities observed in this study were low and in the
range of 10-8 to 10-6 atom fraction in Li-Al suggested by Powell (30).
Powell assumed that the tritium equilibrium solubilit& in Li-Al alloy
followed Sieverts' law; Sieverts' constant was chosen:to be L.4T x 102
torrl/2 (atom fraction)_l at 500°C. Assuming that Sieverts' law is
applicable to Li-Al, Sieverts' constants were determined for the most
reliable data (most likely to be equilibrium solubility data) in Table
V. Figure 10 is a plot of Sieverts' constants for this data set, liquid
lithium (35), and aluminum (11) as a fufiction of inverée-temperature.
Sieverts' constants for Li-Al are between the lithium and aluminum data;
the slopé of the line is in the same direction as that of the aluminum

1/2

date line. The value from Fig. 10 at 500°C is 3.k x 10h torr (atom

fraction)-l. Wiswall and Wirsing (43) found a typical value of 1.22 x
4 - |

iO at 500°C; therefore, Powell's estimate of a Sievefts' constant is too
sfiall.

Some of the data suggest that tritium inventories may not follofi a
simple Sieverts' relatiohship, but this'cannot,be determined conclusively
from the présent study. The tritium partiai pressure_readifigs were
affected by the presence of the stainless steel tube liners, which absofb

tritium throughout the experimental temperature range. Tritium solubil-

ity in stainless steel follows the Sieverts' relationship (28):

 
 

40

TEO

1000 900800 700 600
1 1 i I I

ORNL DWG. 75-8290R1l

500

 

0%

 

LiQuip Al

   
    

    
 

SOLID Af (10

400 300
I I

 

 

nl
— SOLID Li-Al
2[8
g
o' -
™
o
X
w
2
8 0% -
wn
[
«
w
>
i
o
il LIQUID Li (3%) -
|o o -
I ] 1 1 1 1
€ .8 1.0 L2 L4 1.6 1.8
1000
T(°K)

Figure 10. A Comparison of Sieverts'

Lithium, and Li-Al Alloy.

Constants for Aluminum,
 

 

n

)

‘tt .

L1

] -1.155] 4
Ny 2.47 exp[ 7(5K) PT2 , eq. 16
where
N, = mole fraction of tritium in 304 stainless steel,
Pp = tritium partial pressure, torr,
2

temperature, °K.

The stainless steel liners were necessary to prevent an attack of
the quartz containers. It has been reported (1) that Li-Al alloys with
a lithium content greater than 4 wt % (v 12 at. % lithium) form a sepa-
rate metallic lithium phase; however, the mass spectrometer experiments
did not verify this. The attack was probably due to excess lithium in

the Li-Al samples. Further thermochemical study of Li-Al is needed.

 
 

 

 

42

CHAPTER VII
ANALYSIS OF THE TRITIUM RECOVERY SYSTEM FOR THE
PRINCETON REFERENCE DESIGN
A Tokamsk fusion reactor consumes deuterium and tritium which are
injected continuously into the toroidal reactor. In the Princeton
Reference Design, about 10% of the fuel ions fuse and the resulting fast

neutrons are captured in the molten Li Bth blanket. Tritium fuel is

2
generated from the lithium in the salt blanket. The principal coolant
for the fusion plant is helium gas, which cools the reactor and divertor
walls, as well as the blanket. Conventional water boilers then cool
the helium and produce steam which is used to drive electric power
generators.

Tritium must be recovered from the blanket and recycled to replace

that consumed in the plasma. Johnson (21) has proposed the tritium

recovery scheme considered in this section.

Description of the Process

Figure 11 shows the tritium recovery system for the molten fluoride

loop. The flow rates and concentrations are listed in Table VI.

The breeder salt recirculates constantly through eight disengagers
arranged in parallel about the periphery of the reactor. The salt is
sprayed into the disengagers as small droplets to provide an extended
surface area for the dissolved helium and TF to diffuse from the liquid
salt. Salt collects in the bottom of the disengager and flows back to
the reactor blanket. An unspecified doctor system removes impurities
from the LiEBth and adds makeup agents to maintain the desired salt

composition to a small drag stream of salt.
 

*

L

 

43

ORNL DWG. 75-8288

 

DISENGAGER

 

 

 

b

 

SALT
DOCTOR
SYSTEM

]
T

 

 

Figure 11.

System.

 

 

 

 

 

 

RECEIVER

 

 

 

TF

CYCLIC
CONDENSERS

 

 

 

 

 

 

 

 

 

v__3 "

 

 

 

 

i
T

 

 

 

 

 

RF
~ [ELECTROLYTIC CELL

Princeton's Reference Design Salt Blanl;et _Processing

 
 

LY

TABLE VI

FLOW RATES AND CONCENTRATIONS FOR THE TRITIUM RECOVERY
SYSTEM FOR THE PRINCETON REFERENCE REACTOR

 

Li2Bth salt flow through disengagers 4.0 x 106 kg/hr

 

TF Concentration in salt
Entering disengagers 2.00 x lO-T mole fraction
Exiting disengagers - 1.29 x lO"8 mole fraction

Exhaust gas composition

L

TF | | 1.0 x 10~ ) Bt
He o 1.53 x lOE atm
Salt 1.3 x 1077 atm
; Tritium recovery 548 g/day
| Helium ash discharge 1120 g/day

 

 

. The gas effluent is drawn successively thrbugh a water-cooled salt

| : trap and liquid nitrogen-cooled cyclic condensers. The helium is dis-
charged to a storage system for final control. ©Solid TF is melted out

of the offstream cyclic condenser and collected in a small receiver. The
salt flows intermittently through a purification system and into an
electrolysis cell, where a solutioq of KF in TF is electrolyzed to F2
and T2. The gases emerging from the electrodes are saturated with TF

and must pass through the liQuid nitrogen-cooled traps to remove the TF.

The pure tritium gas is recycled to the primary fuel loop.
The main components of the processing scheme, the spray disengagers,

and cyclic condensers were investigated in detail to evaluate their asso-

g ciated problems. The areas that may cause problems for the usage of

disengagers are: (a) the diameter and residence time of the droplets
 

 

*r

&'

45

needed for adequate mass transfer of the dissolved TF and He in the salt,
(b) the ability to spray a molten salt in an evacuated vessel, and (c)
the characteristics of spray nozzles to disengage the salt. The possible
difficulties of the cyclic condensers involve (a) the effect of a noncon-
densable gas on the surface area needed for condensation, and (b) the
type of TF fléw in the condenser. TTheSe”considerations were examined

to evaluate the salt processing system.

Disengager Analysis

Figure 12 shows a detailed schematic of the propésed disengagers.
Each of the eight disengagérs is equipped with’spray nozzles near the top
and a salt discharge line at the bottém. Baffles near the top of the-ves-
sel prevent salt entrainment into fheivapors Which are vented at the top.

To avoid wall embrittlement, the maximum tolérabléuffitium'pféssgre
in the salt was estimated by Maroni (24) as 1072 torr ér i.3é x 10_5 atm.
The corresponding TF concentration in the entering éalt:w;sxdalcfiiafiéd;to
be 2.09 x lO_7 mole fraction. The‘exit'coficentraéion corresponding to a
TF pressure of lO“h atm is 1.29 X 10_8 mole fraction.

A simplified picture of the mass transfer mechanism in an individual
salt droplet is as follows: (a) TF diffuses from yithin the drop to the
surface of the drop, and (b) TF diffusééffofi thegd?op surface into the
ges phase. For the first step involving'liquid diffusion in a spherical

drop, with negligible drag effects, the rate equation is (29):

2 2 2 2
C _ 6 -1“Dt/r 41Dt /r
C_ = 3 (e +1/h e

2. 2
v 179 IOV, ),

eq. 17

 
 

 

 

L6

ORNL DWG. '25-—-8292

COOLED GASES @ 100°C, 0.204m/sec/ disengager
7.57gmole /hr TF |
1.6 gmole /hr He

 

 

SALT TRAP
COOLER —3 9.84 gmole /hr SALT
H,0
EXHAUST GAS@ 660°C, 0.20Im/sec /disengager
.Ox10%tm TF
1.53x I0%tm He
.3x10%atm SALT
1,08 x 108 gmote /hr

MOLTEN Li,Be F,
©€660°C —p
2.09x10" mole fract TF

DISENGAGER
(8 UNITS)

 

 

 

l

MOLTEN Li,Be F,
1.29x 16%mole fract TF

Figure 12. Schematic of the Salt Disengager and Salt Trap.
 

L7

where

Co = initial TF concentration, mole fraction,.

C = final average TF cqncentration, mole frgction,

;D = liquid diffusivity of TF in molten salt, cm2/sec,1

{r = radius of the droplet, cm, |

t = time, sec.
Using the values for the initial and final'average TF concenfrations in
the salt, C/C_ is calculated to be 6.17T x 1072, The corresponding Dt/re
value is 0.232 (Appendix C). The liquid diffusivity of TF in molten salt

> cm2/sec; therefore, t/r2 equals 2.32 x

suggested by Cantor (5) is 10
th sec/cm2. Figure 13 is a graph of time vs diemeter for this equation.
For the second step involving liquid diffusion in a spherical drop,

the diffusion rate equation for TF removal through the gas film resistance

is: ’
dN e '__.”
at = g a(p, - p), ~ eq. 18
where
N = moles of TF,
Ké = mass transfer coefficient, moles/cm sec torr,
a = surface area of drop, cm2,
pP. = vapor pressure of TF, torr,

i

é = partial pressure of TF in gas phaée, torr.
This step ié negligible since the Salt is sprayed into a vaq#um and the
gas film resistance is essentially zero. 4

Atomization of a fiuid usuglly invplvés the applicatidn of an exter-
nal force, such as a gas resistance. However, disintegration will occur

in a vacuum if the liquid Jet is turbulent throughout and its surface

 
 

 

 

L8

ORNL DWG. 75-8293R1l

 

 

 

 

 

. |
_|o I I
t _ 3 Ssec
+2°5.80x10% =5
lOz -l -—
QO
&
:
il
QO
=
w
Q L -
N
&
0’ -
] | | ) :
104 0% 102 i0

DROP DIAMETER, d(microns)

Figure 13. Residence Time vs Drop Diameter for Molten Salt Mass
Transfer. :
 

 

L9

tension is overcome (25). The effects of liquid properties and jet

velocity on the jet breakup have been studied for the case of atomiza-

tion without the influence of a surrounding medium. The mechanism can
be predicted to be dependent on jet diameter, jet velocity, liquid den-

sity, surface tension, and viscosity (Appendix D). From this correla-

tion, the jet velocity needed to achieve atomization must be greater than

488 fps to obtain a droplet size of 150 u. From Fig. 13, the;residence

time for mass transfer for a 150-u drop is found to be 1.31 sec; there-

fore, a column height of over 637 ft is necessary. A smallérfdroplgt
size would decrease the height of a disengager.

The selection of the type of spray nozzle has a considerable bgaring

on the dimension of the spray tower. The characteristics, operatifig

ranges, advantages, and disadvantages for hydraulic-firgssure fiozzle; and

spinning-disk atomizers are listed in Table VII. The maximum capacity

‘through a single nozzle or the feed rate from a spinning disk'is aBout-

10,000 1b/hr. The salt flow rate through each disengager is S.O-x__lo5

kg/hr or 1.1 x lO6

1b/hr; therefore, the minimum number of nozzles-per
disengagér would be about 110.

A preliminary study of a dropwise liqfiidLgas,contacting sysfiem:was

‘made by Gabor et al. (16). _Fused_NaF—Zth containing dissolved uranium

tetrafluoride was sprayed into a fluorine atmosphere to recover uranium

'hexafluoride. Experimental equipment was developed to testfhéat and mass

transfer rates. A Spraying Systems Company full-cone sprgy‘nbzzle

(1/8 G3001.L4) constructed of Monel was used for the heat tréfisfer tests.
This nozzle had a 0.026-in. orifice. The salt was heated to 650°C and
sprayed into air at 20°C. The average diameter for a droplet was deter-

mined to be 164 qu.

 
 

TABLE VII

CHARACTERISTICS, ADVANTAGES, AND DISADVANTAGES OF PRESSURE
NOZZLES AND SPINNING-DISK ATOMIZERS (25)

 

Hydraulic-Pressure Nozzles

Spinning-Disk Atomizers

 

.

Wi W p e

Characteristics

Pressure: up to 10,000 lb/in.2

pressure

1.

Disk speed: 500-30,000 rpm

Capacity: up to 10,000 1lb of feed per hour 2. Disk diameter: 2-10 in.
per nozzle 3. Feed rate: 0.05-15,000 1b per hour per disk
Feed viscosity: up to several hundred cen-
tipoises depending on pressures, capacity,
end orifice size
Advantages

- Suited for multiple atomizers 1. More flexible than nozzles; handle changes in

' di d and feed rate v
Used for countercurrent spray drying iiggpzzgzn:i;ce sk spee eed rate vary
Nozzles generally inexpensive 2. Multiple fluids can be easily handled and
Flexibility in designs and types mixed
Better for viscous fluids than are spinning 3. Liquid feed is under low pressure
disks, since feed can be preheated under 4, No small clearances or openings which may

plug or erode

Disadvantages

Inflexible due to pressure, capacity, and
orifice size variables being independent

Nozzle susceptible to erosion and plugging
High-pressure pumps are expensive

‘Limit to the fineness of atomization

Variations in feed rate not always feasible

l.
2.

Counterflow is difficult

Disks as well as the drive mechanisms are
expensive

Not readily adapted to horizontal spray
dryers

Not well suited to very viscous liquids

 

0S

 
 

 

»

51

Several problems were encountered in spraying the fluoride salt.
Difficulties associated with plugging of the spray nozzle were solved
by heating the neZZle for fully coqtrolled operation. In other fused-
salt process etfidies, aufioresistivelxlheated eait transfer lines have
proved successful. The nozzles uee65were removed and inspected after
20 batch sprayings. Ixamination revealed that the orifice had enlarged
from 26 to 32 mils, increasing the area about 50% and indicating frequent
nozzle replacement.

The prospect of a spray process for the recovefy of tritium from
molten fluoride salt appears discouraging. The veiecity qf the Jjet must

be high to overcome the surface ten51on of the salt for atomization to

occur with negllglble gas fllm resistance or. drag effects of a vacuum of
lO_h torr. The droplet diameter and residence time in the disengager
needed for mass transfer, coupled with the accelerafiionAofthe drope as
they fall, lead to a design of a tower of considerafile height; ;If fhe
minimum number of nozzles if 110, the column_diameter-must also be large

to decrease coalescence of the droplets. The corrosion within the spray

nozzles would make frequent replacement necessary for full‘efierafiofi;

Cyclic Condenser Analysis

A;schematic of the cyclic condensers is shown in Fig. lfi. The
cooled helium and TF leave the salt trap and are drefin through an on-
stream cyclie condenser. The gas 1is cooled.further to thelliquid nitrogen
temperature of T7.4°K, and the TF is condefised out. |

Ideally, the condenser walls mst be kept cold enough to freeze out
nearly all the TF to a negligibly low equilibrium pressure. This would

expose the condenser surface to gas bombardment, so that the pumping speed

 
 

 

 

52

ORNL DWG. 75-8295

COOLED GAS at 100°C, 0.204m7/sec
7.57 gmole/hr TF
1.6 gmole/hr He

 

 

CYCLIC
CONDENSERS

 

 

 

 

 

 

'
|
7.57gmole/hr TF L6 gmole/lr He

 

'RECEIVER

 

 

 

 

 

 

TF He

Figure 14, Schematic of the Cyclic Condensers.
 

 

23

would be limited only byrsurface area and the sticking probability of the
impinging molecules (31). ‘Noncondensables often influence the pumping
speed and the condenser surface area. The condensing gas is likely to
sweep the noncondensable gas against the condenser surface, creating a
blanket through which the condensing gas must diffuse to reach the cold
wall. However, gas blankets are not formed when the mean free paths are
long or when the proportion of uncondensable gas is sufficiently low (31).

Since an appreciable amount of helium, a noncondensable gas, is
drawn through the condenser, the mean free paths were calcfilated to déter—
mine whether a gaseous diffusion barrier would form. The mean free path
is the average distance traveled by a molecule between collisions. Mean
free paths can be determined from the colliéion frequencies of the inter-
acting molecules. The frequencies of collision of the possible pairs of
impacting molecules, the subsequent mean free paths, and the frequencies
of collision with the condenser walls are listed in Table VIII.

When collisions of molecules with each other are negligible in com-
parison with their impacts on the walls of the surrounding enclosure, the
gas is in Knudsen or "free molecular" flow. Knudsen flow uéfially;assumes

3 to 10™2 atm or a

very dilute gases with pressures in the region of 10
very narrow'capillary tube. Also, the mean free path is greater than
the tube diameter for Knudsen flow of a gas (23).

As stated in Johnson's process désign, the duct diameter must not be
less than 0.5 m to avoid large pressure losses. The mean free paths vary
from about 10~2 em to about 107 cm. The impacts of molecules with the

walls are in the same range as the intermolecular collisions; therefore,

it is difficult to determine whether the gas flowing through the

 
 

54

TABLE VIIT

‘MOLECULAR AND WALL COLLISION FREQUENCIES AND MEAN FREE PATHS
OF He and TF IN THE CYCLIC CONDENSERS

 

 

3

(1) Molecular Collision Frequencies, molecules cm sec™t (Appendix E)

He-He T.1lh2 x 102l
14

He-TF 2.013 x 10
TF-TF 6.782 x 10°

(2) Wall Impact Frequencies, molecules em 2 sec™t (Appendix F)

He 1.516 x 10°°
12
| TF 2.430 x 10
j (3) Mean Free Paths (1), cm (Appendix G)
| 2

AHe-He 8.49 x 10~
ATF-He L4.82 x 10~
AHe-TF 3.01 x 106
ATF-TF 1.43 x 107

2

 

condenser is in Knudsen flow. Consequently, the helium may interfere
with the condensation of TF. An alternate condenser design, such as
using multiple tubes with smaller-diameter ducts instead of one 0.5-nm

duct, may be a possible'solution.

 

As stated in the proposed design, the heat load of each condenser

consists basically of the periodic heating and cooling of the mass of

g- - metal (equi&alent to 500 kg of steel) constituting the condenser. The

heat flux to cool the TF gas from 373°K to T7.4°K can be approximated
by summing the latent and sensible heat changes (Appendix H). The total

enthalpy change was calculated to be ~ 132 kecal/hr; however, assuming
 

 

 

55

that the energy loss equals the decrease of the condenser temperature
itself from the melting point of TF ( 2o°c) to TT.4°K, the total heat
exchange duty per condenser is 1075 kcal/hr (Appendix H). Thus, the
freezing out of TF is a minor part of the heat load.

The cyclic condensers seem to be feasible as an integral part of
the tritifim recovery'system.' Helium may increase the surface area
required to freeze out the TF; thus the condenser design will have to
take.this into account. Since the cooling of the condenser itself,
rather than the heat flux of condensing the TF gas, is the maifi_compo—
nent of the heat exchange duty, the total power requirement is not

increased unless there is an increase in the condenser area itself.

Other Design Considerations

The salt traps above each spray tower and the vacuum pump‘system may
be areas of additional design Qonsideration. The molten salt entering
the spray disengagers at 660°C may be boiling, inasmuch as the uncer-
tainty is a factor of 10 for the:reported values of vapor pressure fof
molten LiBeF) (4). The vapor pressure at 660°C of the molten salt is
determined to be 1.3 x 10'h atm, and the total pressure of the vessel
is 3.83 x lO*h atm. An increase in the quantity of vapgrized_salt in the
gas effluenf wofild increase the,salt'trap size needed. The salt-captured
in the cold traps may have to be reprocessed due to redissolution of TF
into tfie salt.

Tritium loss from thé vacuum pump system'will bé inherent; there-
fore, a trapping system'should be a requirement td prevent the escape of

TF. JIn choosing the vacuum pumps, the compatibility of TF with the pump

components must be reviewed.

 
 

56

CHAPTER VIII

CONCLUSIONS AND RECOMMENDATIONS

Conclusions

From this study, the following conclusions can be drawn:

1. The solubility of tritium in molten Li-Bi (~ 15 at. % lithium) is
less than 0.1 ppb at temperatures ranging from 500 to TOO0°C.

2. Beeause of the low solubility of tritium in Li-Bi, the.extraction
process proposed to recover tritium from a Li2Bth blanket is not

attractive.

> 6

3. Tritium sorption in solid equiatomic Li-Al ranges from 10 ° to 10
atom fraction tritium, which is in agreement with estimates for the
blanket recovery system proposed by Powell (30).

4, The Sieverts' constants determined for the solubility of tritium in
Li-Al are smaller than those for aluminum, but larger than those for
lithium at 400 to 600°C.

5. The sorption of tritium in Li-Al appears to be controlled by surface
reaction, slow internal diffusion, or both.

6. The spray disengager process for the recovery of tritium from molten
LieBth does not look attractive for the following reasons:

(5) The velocity of the salt jet must be high for atomization
in a lO-h atm vacuum (> 488 fps for 150-u droplets).

(b) The drop dismeter and residence time fieeded in the disengager
for the mass transfer of TF leads to a tower of considerable
height (> 637 ft for 150-u droplets).

(¢) The minimum number of nozzles needed to atomize the amount

of LigBth to be processed per disengager is 110. Corrosion

within the nozzles would make frequent replacement necessary.
 

 

 

o7

Recommendations
For further study, the following recommendations are made:
1. Appropriate equipment design and sampling technique improve-
- ments are necessary to collect more accurate data for deter-
mining the physical chemistry of the fii-Bi-ftritium system,
2. Removal of tritium from irradiated Li-Al of low lithium content
| should be investigated to determine tritium-solubility and
release rates,

3. Alternative flowsheets for recovering tritium from Li

blankets should be investigated.

 
 

 

 

12.

13.

58

BIBLIOGRAPHY

. Abraham, B. M., "Tritium Production by Neutron-Irradiation of Aluminum-

Lithium Alloys," U.S. Patent 3,100,184 (August 6, 1963).

Ageev, N. V., ed., Handbook of Binary Metallic Systems: Structures
and Properties, Vol. 1, pp. 154-60, U.S. Dept. of Commerce and the
National Science Foundation, Israel Program for Scientific Transla-
tions, Washington, D.C. (1966).

Baes, C. F., Jr., "The Chemistry and Thermodynamics of Molten Salt
Reactor Fuels," AIME Nuclear Fuel Reprocessing Symposium, Nuclear
Metallurgy Symposium, Vol. 15, USAEC Division of Technical Information
Extension (1969).

 

Cantor, S., Physical Properties of Molten-Salt Reactor Fuel, Coolant,
and Flush Salts, ORNL-TM-2316 (August 1968).

 

Cantor, S., Private communication, Oak Ridge National Laboratory, Oak

Ridge, Tenn. (1975).

Cantor, S., and Grimes, W. R., "Fused-Salt Corrosion and Its Control
in Fusion Reactors," Nucl. Technol. 22, 120-26 (April 197k4).

Cember, Herman, Introduction to Health Physics, p. 85, Pergamon Press,
New York, 1969.

Daniels, F., and Alberty, R. A., Physical Chemistry, 2nd ed., pp. 286-
89, John Wiley and Sons, Inc., New York, 1961.

DeVan, J. H., Private communication, Oak Ridge Nationa] Laboratory,
Oak Ridge, Tenn. (1975).

Eggers, D. F., Jr., Gregory, N. W., Halsey, G. D., Jr., and
Rabinovitech, B. S., Physical Chemistry, p. 391, John Wiley and Sons,
Inc., New York, 196L.

Elliot, Rodney P., ed., Constitution of Binary Alloys, lst supplement,
p. 155, McGraw-Hill Book Co., New York, 1965.

Ferris, L. M., Mailen, J. C., Lawrance, J. J., Smith, F. J., and
Nogueira, E. D., "Equilibrium Distribution of Actinide and Lantha-
nide Elements Between Molten Fluoride Salts and Liquid Bismuth
Solutions," J. Inorg. Nucl. Chem. 32, 2019-35 (1970),

Fraas, A. P., Conceptional Design of the Blanket and Shield Region
and Related Systems for a Full Scale Toroidal Fusion Reactor, ORNL-
™-3096 (1973).
 

0

 

 

 

1k,

15.

16.
1T7.
18.

19.

20,

21.

22.
23.

2h.
25

26.
27.'

28.

29

Fraas, A. P., "Conceptual Design of a Fusion Power Plant to Meet. the
Total Energy Requirements of an Urban Complex," Nuclear Fusion
Reactor Conférence, Brltlsh Nuclear Energy Soc1ety (September

1969)

Frigerio, Norman A., and: LaVoy, Leo L. "The Preparatlenvand-Proper-
ties of LiPb, A Novel Material for Sh1elds and Collimators,fi Nuel.
Technol. 10, 322-24 (March 1971).. :

Gabor, dJ. D., et al., Spray Fluorlnatlon of Fused Salt as 8 Uranlum

Recovery Study, ANI~-613L (March 1960).

Glasstone, S., Textbook of Phy51ca1 Chemistry, Tth ed., pp. 262-T0,
D. Van Nostrand Co., New York, 1940.

Hansen, M., ed., Constitution of B1n__y Alloys, McGraw-Hlll Book
Co., New York, 1958,

Hickman, Robert G., "Tritium in Nuclear Fusion Power;" Seventy-
seventh National MEetlng of the American Instltute of Chemlcal
Engineers, Pittsburgh, Pennsylvania, 19Tk4.

Hitch, B. F., and Baes, C. F., Jr., Inorg. Chem. 8, 201 (1969).
Johnson, E. F., "Fuel Handling," A Fusion Power Plant, pp..362-410,
Plasma Physics Laboratory, Princeton University, Princeton, N. J.,

August 19TL.

Kirk-Othmer Encyclopedia of Chemical Technology, 2nd ed., 9, p. 611,
"Hydrogen Fluoride,”" Interscience Publishers, New York, 1972.

Knudsen, M. H. C., The Klnetlc Theory. of . Gases, Methuen and Co.,
London, 1950. , : D

Maroni, V. A,, "Tritium Distribution and'Leekage;"HA Fusion Power
Plant, pp. 411-31, Plasma Physics Laboratory, Princeton Uhlver51ty,
Princeton, N. J., August 19T4.

Marshall, W. R., Jr., "Atomization and Spray Drying,” Chem. Engr.

'Prog. Mono. Series, No. 2, Vol. 50, Amerlcan Instltute of Chemlcal

Englneers, New York, 195k.

Mills, R. G., ed., A Fusidn”PoWer”Plant,WPiasme Physies'Laberatbry,
Princeton UniVersity, Princeton, N. J., August 19Tk,

Mueller, W. M., Blackledge, J P., and L1bow1tz, G G., MEtal
Hydrides, p. Tl, Academic Press, New York, 1960.

Nelson, Howard G., and Stein, James E.,, Gas-Phase Hydrogen Permeation
Through Alpha Iron, 4130 Steel, and 304 Stainless Steel from Less
Than 100°C to Near 600°C, NASA—TN-D7265, Ames Research Center, Iowa,
April 1973.

 
 

 

29,

30.

31.

32,

33.

3k,
35,
36.
37.

38.

39.

Lo.

U],

Lo,

43,

60

Newman, A. B., Trans. Am. Inst. Chemn. Engrs.'gz_(l93l),
Powell, J. R., et al., Studies of Fusion Reactor Blénkets with
Minimum Radiocactive Inventory and with Tritium Breeding in Solid

Lithium'Compounds: A Preliminary Report,_BNL-18236 (June 1973).

Power, B. D., High Vacuum Pumping Equipment, Relnhold Publishing Co.,
New York, 1966,

Rose, D. J., On the Feasibility of Power by Nuclear Fusion, ORNL-TM-
2204 (May 1968).

Sieverts, A., "Absorption of Gases by Metals," Z. Metalkunde 21,
37-46 (1929).

Simons, J. H., ed., Fluorine Chemistry, p. 233, Academic Preés, New
York, 1950.

Smith, F. J., end Land, J. F., "Hydrogen Isotope-Lithium System,"

Trans. Am. Nucl. Soc. 21, 167 (1975).

Sokol'skaya, L. I., Gases in Light Metals, Pergamon Press, New York,
1961.

 

Steiner, D., "Fusion Reactor Design Problems," International Atomic
Energy Agency, Vienna, 19TL.

Steiner, D., and Fraas, A. P., "Preliminary Observation on the
Radiological Implications of Fusion Power," Nucl. Safety 13, 353

(1972),

U. S. Energy Research and Development Administration, (formerly
USAEC), Proposed Rule Msking, 10 CFR 50, Federal Register ;é,
No. 111 (June 1971).

Vetrano, J. B., "Hydrides as Neutron Moderator and Reflector Mate-
rials," Nuclear Engr. and Design 1k, 390-412 (1970).-

Watson, J. S., A Summary of Tritium Handling Problems in Fu51on
Reactors, ORNL-TM-L4022 (November 1972).

Weast, R. C., ed., Handbook of Chemistry and Physics, 50th ed., p.
F-44, The Chemical Rubber Co., Cleveland, Ohio (1970).

Wiswall, R. H., and Wirsing, E., The Removal of Tritium from Solid
CTR Blanket Materials: A Progress Report, BNL-19766 (February
1975). -

i€

 
 

 

 

 

11

61

APPENDIX A

THE COMPATIBILITY OF Li-Bi WITH LizBth

The equilibrium distribution studied can be repfesented by the

reaction:

BeF2(salt) + 2Ll(Bi) = Be(Bi‘) + 2L1F(sa.1t) . eq. 19

The equilibrium constant for reaction 19 can be written as:

 

2 2
YBe YBe X Lir Y LiF
K = . eq. 20
Xger Y Yo ¥ |
eF2 BeF2 Li Li
where

K = equilibrium constant,
Y = mole fraction of component in the Li-Bi phase,
X = mole fraction of compcnent in the salt phase,
vy = activity coefficient referred to the appropriate pure solid

or liquid.

The change of standard free energy for reaction 19 is:

£ f

AG. = -RT 1n K = 2 86" o - 4G Ber, *  eq. 2l
vwhere
AGO = change of standard free energy,rkcal/mole,
AGf = standard free energy of formation, kcal/mole,_
R = gas constant, 1.987 cal/g-mole °K,
T = temperature, °K.

From Equations 20 and 21, the following relation is obtained:

 
 

 

AG - 2AG

- BeF LiF

In K =
" RT

62

2 2
LiF | LiF
> 2
T Y4

YBe YBe X
= 1ln

Y
KBe_F2 BeF,

The experimental conditions are:

T

XLir

X
BeF2

Trs

The thermodynamic data

f

AG BeF. = -243.86
2
or
AGf = -217.66
BeF *
2
f _
AG LiF = -141.79
or
AGf = -127.32
LiF ’
1n Ypi = 0.4509
or

1n Y3 -9.5205

18 Yrip

600°C = 873°K,

0.667T,

0.333,

= 0.15.
needed are:

+ 30.01[J2§] kcal/mole, (Reference 3),
10

kcal/mole at 600°C,

+ 16.58 [—EL] kcal/mole, (Referénce 3),

103

kcal/mole at 600°C,

-~ E%%%%‘ s {(Reference 12),

at 600°C,

= -0.8913 at 600°C. (Reference 20)

From Equation 22, we obtain:

eq. 22

eq. 23

eqg. 24

eq. 25

eq. 26
 

 

4

 

63

 

 

f £
AG BeF,, 2hG 11w
in K = =T =21,318 , LT - eq. 27
log (ppm Be) = 6.85 - T?%;? , (Reference 11) - . _eq. 28
ppm Be = -0.1832 at 600°C,
or , _
- 102
YBe = 1.5207 x 10 .
The activity, a, of a pure EUbstance is unity. By'&efinition,
a, = Y5 Xi . | | o | eq. 29
Therefore,
YBi *B1 = YBe *Be T 1 > | - ea. 30
or |
Yo XB. ; -
B 1 L
Ype = = = 6.5759 x 10" .

1

Assuming YBeF2‘

1ln YBe

or

YBe

This value of YB

XBe . 1.5207 x 107

1, from Equations 22 and 27,

21.318 - 32.436 = -11.110,
1.4846 x 10"5,

e = 1.484 x 10~° is less than the solubility value of

1.5207 x 1077 at 600°C from Equation 28; thus Li-Bi (~ 15 at. % Li) is

compatible with LiéBth at 600°C. The proposéd extractor will operate
T

at 980°K and Y i = 0.01. » Wwhich

L
is less than the solubility value of 8.912 x 107,

At these conditions, Y, = 2.779 x 10~

B

 
 

64

APPENDIX B

SAMPLE CALCULATIONS FOR Li-Bi--TRITIUM SORPTION DATA
FOR SAMPLE NO. 2.7 AT 600°C

(I) For the Li-Bi metal-phase analysis, the

 

Li-Bi sample weight = 1.8375 g,
and
liquid scintillation result = 1.289 x th dpm/ml;
(}.289 X th 35%)(50 ml solution)( \ 0112 ) = 2,903 x 10~
2.22 x 10 dpm

The specific activity of tritium is calculated from the following equa-

tion:

Ci

13
1.13 x 10 —g-, (Reference T),

specific activity = —Fn7
(M)(t%)

 

where
M = molecular weight of T, 3.016 g/g-mole,
t% = half-life of T2, 12.3 years or 3.8815 x 108 sec;
therefore, the
1.13 x 1073 3 Ci
gspecific activity = : 5 = 9.653 x 10~ =—
(3.016)(3.8815 x 10°) &
or
1.036 x 10+ &L
Ci
Thus,
-7 1.036 x 10'h -11
(2.903 x 1077 01) (22X — g 1) = 2.996 x 107 g T,

T

T

eq.

Ci

T‘
 

 

 

L Y]

65

-11
2.996 x 10 g T = = 0.0163 ppb ,

1.8375 ¢ Li-Bi + 2.996 x 10t g T

or

ot. % T [3-016 g/g-mole / 3.016 g/g-mole & 208.1 g/g-mole) x 100

E (6.899 x 10

 

-11 |
v 8T 3y - 2.996 x 10 3
sample wt (6.899 x 107) )_

1.8375 g

1.125 x 10" '.

(II) For the gas-phase analysis for tritium,

the liquid scintillation result = 4.778 x.lO5 dpm/ml.,

 

 

and tritium monitor result = 4.9 x ;03 uCi/mB.
() For the liquid scintillation result: |
dpm 50-ml solution ] ” Ci
(F.TTB x 10° )( )(BOO-ml gas volume)( )
ml/\},.5-ml gas sample 5 on x 10%2 dpm

= 1.913 x 107> Ci
or .
' -1
(1.913 x 1073 Ci)GLfixfii%§%£L——5) = 1.982 x 1071 g T.

Using the ideal gas law,

p= LR | eq. 32

 
 

where
p =
n =
T =
. v =
, R_ _

tritium partial pre

66

ssure, torr,

moles of tritium, g-moles,

temperature, °K,

ges. volume, 800 cm3

62,400 torr cm3/°K

By substitution,

-

a3
]

(b)

(h.9 x 10

= 1.307 x 10

L

3

1.982 x 1077 & T) (6
3.016 g/g-mole T

ho9 x 10-3 torr.

3

g-mole.

2,400 torr cm3

°K g-mole

For the tritium monitor result:

m3 uCi

3 Ci.

uCi) (10"6 Ci)(l.s liters gas volumé)(;

in monitor

) (873.1°K)(———3=—7§)

0_3 m
liter

800 em

3) 800-m1 volume
4,5-ml sample

)
 

-

67

APPENDIX C
CALCULATION OF RESIDENCE TIME FOR MASS TRANSFER OF
TRITIUM FLUORIDE FROM A SALT DROPLET
A numerical solution of liquid diffusion in a sphere is expressed in
Fig. 15, whicfi relates C/CO, the ratio of the final average concentra-
tion to the initial concentration, to Dt/r2, where D is the liquid diffu-

sivity, t is the residence time, and r is the radius of the sphere (29).

| ORNL DWG. 75-8289R1
10 I T — 1 1

 

C/Co

 

 

 

0 I 1 ] i 1

 

- |
0o 0.05 0.10 0I5 0.20 025 @ 030 - 035
' Dt /r2 | - -

Figfire 15, Numerical Solution of Liquid Diffusion in a Sphere.

 
 

 

68

APPENDIX D
CALCULATION OF SPRAY DISENGAGER HEIGHT FOR SALT
DROPLETS OF VARIOUS SIZES (25)
For Tyler's mathematical predictions, drop diameter and wavelength

can be correlated by the equation

%;-= §. (E§)3 = .69 , eq. 33
where
A = wavelength, cm,
dO = jet diameter, cm,
X = drop diameter, cm;
therefore,

x =1.92 do .

If x = 150 p or 1.5 x 10 2 cm, d = T.8x 1073 cn.
The breakup mechanism of a jet as predicted by dimensional analysis

is a function of the jet Reynolds number, vdo pL/u, and a dimensionless

group, u//prdo

(cm/sec), o is the surface tension (dynes/cm) is the liquid density

’pL
(g/cm3), and y is the liquid viscosity (g/cm sec). Experimental data
are correlated in Fig. 16 to show this relationship.

From the physical properties of LieBth salt,

-3
7 = —teu = 20,6 P [(1.911 Egc-) (1—8—0—:]11&8—5-) (7.8 x 1073 cm)] = 0.137 .

Vpdeo

From Fig. 16, NRe > l03 for atomization of the jet. That is,

vdo pL

= ————=v (7.8 x 10-3 cm) (1.9’4 _g_)(_C_m__S_g_g_ = 6.696 x 10_2 v,

N
Re U ce’/N0.226 g

s referred to as the Z-number, where v is the jet velocity
 

 

69

ORNL DWG. 8296R1

 

      
  

 

 

 

 

| I i
o' -

= I I

': Rayleigh Breakup Zone Atomization Zone

Ly

"
N 0§ -

10 10t 103 10* 10% 0%

vdop,
=

Reynolds Number, NRe=

Figure 16. Ohnesorge's Chart (25) Showing Jet Breakup as a
Function of Reynolds Number and Liquid Properties. ‘

 
 

70

or

NRe 10-3

ft
= >
6.696 x 1072 6.696 x 10

b em _ _ft
=1.49 x 10 gg;‘— 488 sec

v >
From Fig. 13, t = 1.31 sec; thus, h > 637 ft.

If x 100 u or 10-2'cm, then

do 5.21 x 10-3 cm,

0.168,

_ 2
NRe >0 x 10,

659 —= ,

sec

d
v

0.58 sec, and

ct
]

h > 382 ft.

| If x 200 w or 2 x 10-2 cm, then

1.0k x 1072 cm,

Op‘
H

0.119,

N, > 105,

 

367 —=

sec

2.32 sec, and

<
v

ct
i

 

=
v

851 ft.

 
 

 

 

 

-

71

APPENDIX E

CALCULATION OF THE FREQUENCIES OF MOLECULAR COLLISIONS (10)

The total collision number for N' molecules of Type A perlunit volume

is:
. ' 1/2 .
L L'2 2 (27 kT) . 7 S L
= R
where
NA = number of Type A molecules‘fier”ufiit volufie, molecules/cm3,
o = molecular diameter, cm,
_ ' -16 2,...20
k = Boltzmann's constant, 1.38 x 10 g cm” /sec” °K,
n = reduced mass, g/molecule,
m = molecular mass, g/molecule,
T = temperature, °K,
P = pressure, g/cm sec2.

For collisions between unlike molecules,

1/2

vt 27 /2r kT n
FAB =2 [NA NB] [OAB ] (}%t;;—) ) eq. 35

where

o = _AB
AB m, + s

. o2
- =(°A °B) |

 
 

12

If A= TF and B = helium,

1/2

_ to 2 s2m kKT
(I)  Fpp= N0y ( n ) >

where

(3.76 x 10‘12

+d
n

atm) atm cm3 2

(76 em Hg(%B.GgHé)(%8O cm)

sec

 3.809 x 1070 g

2
cm sec

g

 

0 = _é__(?.809 x 107 g)( __sec> °K )( 1 )
d - O
A T em sec2 1.38 x 10_16 g cm2 7. 4K

_ 3.56 x 108
3

cm

n = %_(22.02 g g-mole ) = 1.83 x 10°°> g/molecule.

g-mole (6.02 x 1023 molecules
The molecular diameter of hydrogen fluoride (HF) is 9.k x 1077 cm (34).

Assuming the molecular diasmeter of TF to be approximately the same as for

HF,

o, = 9.4 x 1072 cm.

Then,

8 2

Fpp = (3.56 x 10 cmf3)2(9.h x 10~° cm)

 

[2“(1.3 x 10 "~ g cm ) (77.4°K) ( molecule - )]
, g

se02 °K 1.83 x 10'2
 

 

 

-

73

or
F = 6.782 x 10° Lolecules
AA : 3
cm sec
1/2
_ 2 2 f2nm kT
(I1) FBB = NB O’B ("——n "') >
B
where
P, = 107" atm = 101.3 —&—

 

.38 x 10

 

o - Py (101.3 g)( sec °K )( 1
- O
B T 2/\1 16 2 om? TT. 4 K.

_ 9.48 x 1077
3

cm sec cm
ng = %’(h'ggglg ( g—ggle ) = 3.32 x 11.0_2)+ g/molecule .
g1t 6.02 x 10> molecules | |

The molecular diameter is related to gas viscosity by the follqwing equa-

tion: |
2. gwm kT)l/2 | | |
Y [ 5 ‘(Reference 8) eq. 36
‘ o
or
1/2 ;[
ge = S |{rm kT)" " .
16 oy P
where

u = gas viscosity, g/cm sec.

For helium at TT.h°K,'u'equals 8.4 x 10~ g/cm seec (42) and o

calculated from Equation 36:

BlS

 
 

 

 

T4

 

 

 

 

 

1/2
-16 2
2 ] .
5.2 - = )[fl( hggo g ) (1 38 x 10" & on ) (TT.h°K)]
6.02 x 10~ molecules sec 9K
) ;_( cm sec )%
T \8.4 x 107 g
oB2 = 5.592 x 10‘l6 cm2, or
5 -8
oy = 2.365 x 10 ~ cm.
Fpp = (9.48 x 10%° cm"3)2 (2.365 x 10'8 cm)2
1.38 x 10_l6 g_cm2 molecule
o ( : 5 ) (77.4°K) (—'—"_'zfié) )
sec 9K 3.32 x 10
_ 21 molecules
Fpp = 7.142 x 10 e
\ cm sec
1/2
_ rot 27 (27 kT
(111) Fp =2 [, 5] [0,5°] (————-—n ) ,
AB
where
g = (4.003)(22.02) 55 &/molecule, or
(4,003 + 22.02)(6.02 x 107°)
n.. = 5.627 x 10'21‘ /molecule
AB . g .
-8 -9 2
s 2. [2.365 x 10~ em + 9.4 x 10 cm] or
AB 2 >
UABQ = 2,731 x :Lo"l6 em® .
 

 

 

 

B

or

|

75

2(9.48 x 10%° en™3) (3.56 x 105 em™3) (2.731 x 1070 cn?)
1/2
2n kT
nAB » Or

 

-16
1.843 x 109 cm_h [21r (1'38 X 10

2
sec” ©

14 molecules

3
cm”™ sec

2.013 x 10

 

2
g cm ) (77.4°K) ( moleculf
K 5.627 x 10

- \l/2
)
g

 
 

 

 

76

APPENDIX F

CALCULATION OF MOLECULAR COLLISIONS WITH CONDENSER WALLS

The mass of gas striking 1 cm? of wall surface per second is given

by:
.where
M =
1
N =
C =
m . =
If A=TF
then, MA
where
T
NA =
CA =
m, =
or
MA =
and
where
1
NB =

M=N C m/4, (Reference 1T) eq. 37

mass of gas colliding with the wall, g/cm2 sec,
nunber of molecules per unit volume, molecules/cmS,
average velocity of a molecule, cm/sec,

mass of a single molecule, g/molecule.

and B = He,

.
N, Cp mA/h .

3.56'x 108 molecules/cm2,

2.727 x th cm/sec,

-23

3.66 x 10 g/molecule,

8.88 x 10'11 —£g _ _ 5. 43 x l012 molgcules :
cm”ssec om® sec

N, Cp m. /4,

9.48 x :Lol5

molecules/cmB,

¥

“y
 

 

&

 

T7

6.395 x th cm/sec,

2
to
I

6.649 x lO*Eh g/molecule,

of’

or
M]3 1.008 x 10"3 __.2_5._ - '1’.516‘ x 1020 molecules

cm~ sec o _ cm- sec

The ratio, M is calculated,
A

20
-MME = 2:316 x 10 . _ ¢ 537 x 10

T
A 2.43 x 1012

 
 

78

APPENDIX G

CALCULATION OF MEAN FREE PATHS OF TF AND HELIUM COLLISIONS

The mean free.path is the average distance traveled by a molecule A

in a straight line before it collides with a molecule B. This value is

 

 

related to the frequency of collisions between molecules A and B as

follows:
— 1
C, N
A = A4 , (Reference 17), eq. 38
A,B F
AB
where
AA p = mean free path of molecule A colliding with molecule B, cm,
2
EA = mean velocity of molecule A, cm/sec,
. 1
NA = number of molecules of A in unit volume, EQ;SEE;EE-.
cm
The mean

velocity may be expressed by

CA = (8 kT/mm) /2 , (Reference 1T), eq. 39
where
- ' -16 2 2 o
k = Boltzmann's constant, 1.38 x 10 g em”/sec” °K,
T = temperature, °K,
m = mass of a single molecule, g/molecule.

Therefore, if A = TF and B = He,

 

—— '
C
(1) », , = A
wvhere
1 8 3
N, = 3.56 x 10 molecules/em™,

ot
 

 

79

 

 

 

 

 

 

)

1/2

1/2

w

EAA = 6.782 x 10° molecules/cm3 sec,
_ -16 2 23
C, = [-181'- (1'38 X 102 £ ) (77.4°K) (______‘_6.022}:020 . molecules)] .
sec” °K ve B
or )y
CA = 2,727 x 10 cm/secy
substituting,
4 8 =3
\ _{(2.727 x 10" cm/sec)(3.56 x 10 cm
AA T 5 =3 -1 ’
> (6.782 x 10”7 em ~ sec )
or
A = 1.43 x 10T cm
A,A . ®
- '
C. N
(I1) A g = ? -
? BB
where
? -
Np = 9.48 x 1015 molecules/cm 3,
FBB = T7.1h2 x lO21 m.olecules/cm3 sec,
- _18(1.38 x 10_16 g em” o 6.02 x 10°5 molecules
Cg = |7 5 (77.4°K) %.003 g
sec” °K : '
or
Efi = 6.395 x th cm/sec;
substituting,
_ -2
AB,B'_ 8.49 x 10 © cm.
— 1
' C. N
(111) A, o = ? A
’ AB
where
1k 3
FAB = 2,013 x 10”7 molecules/cm” sec;

thus

 
 

 

 

 

A,B

(IV) A ,

B,A

80

4.82 x 10-2 cm.

v
B | =

3.01 x lO6 cm.

 
 

 

-
+

 

 

81

APPENDIX H

CALCULATION OF CYCLIC CONDENSER HEAT LOAD

The heat exchange duty of the cyclic condenser, as expressed in the’
Princeton Reference Design (21), is the cooling duty of decreasing the
condenser temperature from the melting point of TF (20°C) to T78°K. Thus,

the total duty per condenser is calculated to be:

 

kecal (293-78) _ kcal
[60 c] [ 2L nr OC] 1075 S

 

where 60 kfial

G equals the total thermal capacity equivalent to 500 kg

of steel.

To estimate the heat change required to cool TF from 100°C to ‘T8°K,
the sensible and latent heats are summed as shown below. The hea£ Eépau
cities and enthalpy changes are HF physical properties (22,3k4).

(a) Sensible heat, 100°C to 20°C (melting point of TF)

\

 

 

Q = mC () AT (7 57 g'mole) g_igi‘ec%é) (100 - 20°C) = 8.66 x 10" %
(p) Latent heat of vaporization

Q, = (757 £521) (1697 =21) = 1.285 = 10" 2L
(c) Senéiblg heat, 20°C to -83°C (freezing point'of TF)

¢y = g 17y (157 S (BZSE) 2o 0 530 = 5,02 ¢ 207 8L

 
 

 

g2

(d) ZLatent heat of fusion

_ N g-mole\ ¢
q, = mi, = (7.57 E5=2)(

22.02 g
g-mole

(e) Sensible heat, -83°C to T8°%K

150°K
T78°K

4 cal

1.506 x 10 e

R

The total heat load is

>

Z Q =1.319 x 10° &2t

i=1l

Q. = mf' Cp 4T = (7.57

g-mole 12.2
hr ) [(g-mo

hr 1.319 x 10

) (46.93 Eg—l) = 7.823 x 10

—£227) (190°K) — (

2 kecal
hr °

3 cal
hr

4.2 cal

g-mole °K

)(78°%)]

w3

 
 

 

Wy

60.
61,
62,
63.
6l
65.

66.
67.

68.
69.

70.
Tl.
T2,
13-

74-100.

%

 

83

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