»

G,

JAN 10 1968

 

 

OAK RIDGE NATIONAL LABORATQ‘
operated by

UNION CARBIDE CORPORATION %
NUCLEAR DIVISION
, for the

U.S. ATOMIC ENERGY COMMISSION

ORNL- TM- 2032
65

COPY NO. -
DATE - November 1, 1967

] _ o
Cf/_'v;'?/_l, .‘/4/‘/ £/ s

CLOSED-CIRCUIT TELEVISION VIEWING IN MAINTENANCE
OF RADIOACTIVE SYSTEMS AT ORNL*

R. L. Moore

ABSTRACT

Considerations affecting the use of closed-circult television
in radiocactive. systems are discussed.

Equipment used for closed-circuilt television viewing at the
Homogeneous Reactor Test and at the Molten-5alt Reactor Experiment
is described.

The results of a radiation test of a miniature, radiation-
resistant television camera are presented.

*Paper presented at the Winter Meeting of the American Nuclear
Society, Oct. 31-Nov. 3, 1966, Pittsburgh, Pa.

NOTICE This document contains information of a preliminary nature
and was prepared primarily for internal use at the Qak Ridge National
Laboratory. It is subject to revision or correction and therefore does
not represent a final report.

m}T"-" RPN . Sy
 

 

 

LEGAL NOTICE

This report was prepared as an account of Government sponsored work. Neither the United States,

nor the Commission, nor any person acting on behalf of tha Commission:

A. Makes any warranty or representation, expressed or implied, with respact to the accuracy,
completenass, or usefulness of the information contained in this report, or that the use of
any information, apparatus, method, or process disclosed in this report may not infrings
privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of
any infermation, apparatus, method, or process disclosed in this report.

As used in the above, "*person acting on behalf of the Commission'’ includes any employee or

contractor of the Commission, or employee of such contractor, to the extent that such employee

ot contractor of the Commission, or amployee of such contractor prepares, disseminates, or
provides access to, any information pursuant to his employment or contract with the Commission,

or his employment with such contractor.

 
 

CONTENTS

IntrOdUétion.a......f-..;.,.... ----- e s e 0

Underwvater Viewing in the Homogeneous
Reactor Test.".......-.....‘l....-..lflfifl!

.Core Inspection in the Homogeneous

ReactorTes‘t‘.‘...,......Il.."...........

Radiation Tests on a Miniature, Radiation-
RESiStantATV Camera....'....o.b-...}.-..

‘Remote Maintenance Viewing in the Molten-

Salt Reactor Experiment.cescecessecscccce

concluSiOnS‘O.l'..'l.....l....‘.‘....QO...

Pag
L

 

 

 
 

 

INTRODUCTION

- The ease with which maintenance of radicactive systems can be
performed is strongly dependent on the ability to view the operations. . .
In systems such as the Molten-Salt Reactor Experiment (MSRE), the v
radiation levels in portions of the system are very high and viewing '
must be accomplished directly through high-density windows or indirectly
by means of optical devices or closed-circuit television. At ORNL,
the use of windows or optical devices is the preferred method of viewing;
however, in some cases, supplementary viewing with closed-circuit o
television is either necessary or desirable. Radiation damage is the
most important consideration affecting the selection of television for
viewing of maintenance operations. Other considerations are the rugged-
ness and reliability of the equipment. The radistion levels encountered
in many of the ORNL: viewing operations are high in comparison with
permissible biological dose rates, but low in comparison to the dose that
conventional electronic circuitry can withstand. Commercial grade
equipment is used for these gpplications and 1little, if any, attempt is
made to make the equipment radiation resistant. In other cases the
radiation levels are much higher, and radiation resistant equipment is
required.

UNDERWATER VIEWING IN THE HOMOGENEOUS REACTOR TEST

Figure 1 shows a camera used for underwater viewing in Homogeneous

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. 1. HRT Underwater TV Camera Assembly.
 

o

Reactor Test (HRT) maintenance operatlons.' This'assembly consisted of
a standard Dage Model- 112 AR camera, a flanged tube, a Lucite face
plate, and a Tygon tube.  The Tygon tube enclosed the camera cable to

a point well above the pool level and prov1ded mechanical protectlon

as well as water-prooflng._ To keep the camera temperature within the
recommended limit, an air purge was supplied to the camera through a
small polyethylene tube and returned through the Tygon tube. The camera
was manipulated manually by means of a rigid pipe and a plastic line.

Because of the'shielding provided_by the water and the variety of
locations of the camera, no exact data were obtained on the dose which

. the camera accummulated. However, we estimate that the dose rate varied

from negligible to 10°r/hr and that the total dose was about 10* r.
Some lens browning occurred, and more than the usual amount of trouble
was encountered with the electronic circuits. However, most of the
trouble was routine or was caused by shock and vibration. The only
electronic trouble attributable to radiation damage was the failure of
several electrolytic condensers in the camera. Replacement of these
condensers restored the camera performance.

CORE INSPECTION IN THE HOMOGENEOUS REACTOR TEST

Figure 2 shows a camera assembly developed for use in locating and

‘inspecting a hole,1n'the,HBT core. The camers assembly, developed by

 

Fig. 2. HRT Miniature TV Camera and Preamplifier.

 

 
 

6

Dage Electronics D1v131on of Thampson Products to ORNL spec1f1cat10ns,
consists of a camera equipped with a non-browning lens, a camera
preamplifier, and a 10-ft interconnecting cable. A mirror and lighting
assembly, consisting of a polished Stellite, right-angle mirror and a
50-cp spotlight bulb, was added at ORNL. The outside diameter of the
camera is 2 in., and the length (exclusive of lens, mirror, and lamp)

is 7-3/4 in. The only electronic ccamponents in the camera head are a

~ type 6198A vidicon tube, a deflection coil assembly, one carbon resistor,
and one ceramic capacitor. All other electronics are located in the
preamplifier or in the camera comtrol unit. Separation of the camera
and the preamplifier resulted in a considerable reduction in size of the
assembly to be inserted in the reactor core and permitted the radiastion-
sensitive components of the preamplifier to be located in a region of
much lower activity, outside the reactor core. This camera was designed
to be interchangeable with the underwater camera previously described
and used the same camera control unit and monitors.

Figure 3 shows the camera assembly installed on an articulated-
manipulator in a remote maintenance mock-up of the HRT core and blanket
vessels. Hydraulic control of the three manipulator joints, together
with rotation of the camera by means of an electric motor, enabled the
operator to view any part of the exterior surface of the reactor core
vessel.

Figure 4 shows a manipulator and camera assembly constructed for
use in viewing the internal surface of the HRT core vessel. The
assembly shown here is foreshortened, as evidenced by the lines above
and below the preamplifier. The actual distance from the preamplifier
to the camera is 10 ft, and the overall length is approximately 20 ft.
The camera was required to pass through a 2 <in. diameter hole,. in a
reactor access flange, located 1h ft below the top of a portable
maintenance shield.

_ I , ,
In the manipulator shown in Fig. 3, a fixed-focus lens was used,
and focusing was accomplished by moving the camera. In the assembly
shown in Fig. 4, camera motion was restricted to vertical motion along
the centerline of the reactor, and remote focusing was required. This
was accomplished with a remotely operated spur-gear mechanism, shown
at right of the camera. To permit insertion into the reactor, the
mechanism was designed to retract and fold inside a 2-in. diameter
cylindrical surface which was concentric with and parallel to the outer:
surface of the camera. After the camera was inserted, the mechanism
was lowered and rotated to engage a spur gear on the camera-lens
focusing ring. S _
   

PHOTO 32498

   
   

~
€
- -

 

 

  

Fig. 4. HRT Miniature TV Camera and Linear Manipulated.
 

 

8

BADIA'I‘ION TESTS OF A MINIATURE, RADIATION-
- ' RESISTANT TV CAMERA :

Fort.unately for the project ('but unfortuna:tely for our TV camers,
program) the hole in the HRT core was found and inspected by semidirect
optical means, and these remotely man:l.pulated TV camera systems were not
needed. However, we did gain experience in developing and operating
these devices and we.did obtain some useful data. As part of the camersa
evaluation, we installed the camera in the waterproof container shown
in Fig. 5 and exposed it to intense gamma radiation produced 'by °Co
slugs in the canal at the Oak Ridge Graphite Reactor. During these
tests, the camera was focused on a miniaturized resolution chart, and
performance was observed during initial insertion and prolonged operation.
The gamma dose rate was monitored with Ce(SO4 )2 dosimeters.

In the first test, the camera was equipped with a standard lens
and lowered into a 1.5 x 10° r/hr gemma field. There was no observable
initiel effect as the camera was lowered into the field; however, the
picture faded rapidly and required maximum target voltage after 20 min
of operation. After 1 hr of additional exposure in a reduced field of
approximately 5 x 10° r/hour; the picture was not readable. An additional
18 hr of exposure was accumulated at this lower level before the camera
was removed from the radiation field. The total dose was 5 x 10° r.
Subsequent ‘examination showed no visual damage cther than glass-browning
of the lens and the vidicon tube. After replacement of the lens, the

 

PHOTO 33279

 

 

Fig. 5. HRT Miniature TV Camera Radiation Test Assembly.
 

 

o\

9
camera operated satisfactorily with only a slight lossof_sensitivity.

'In the second test, the camera was. eqpipped with a nonbrownlng
lens and lowered into a 3.9 x 10° r/hr ganmma field. The only effect
observed was a gradual loss of sensitivity, which was compensated by
adjustment of the target control. The duration of the test was
approx1mately 250 hr, and the total integrated dose received by the
camera was approx1mately 10® r. At the end of the test, the target
control had been advanced to its maximum position, and there was a
slight loss in picture resolution. Subsequent tests showed that
approximately 20% of the loss of sensitivity was due to browning of
the camera lens and the lamp bulbs. The remaining 80% was apparently
due to browning of the vidicon. faceplate. Replacement of the vidicon,
the lens, and the lamps restored the original sensitivity of the
equipment. Because of the time and expense involved, and because the
10® r dosage obtained exceeded the dose expected in the HRT viewing
operation, no attempt was made to determlne the ultimate life of the
camera. - o ‘

REMOTE MAINTENANCE VIEWING IN THE
- MOLTEN-SALT REACTOR EXFERIMENT

Figure 6 shows é-Kintel’, model 2511 -radia.tion-résistant,camera.
presently used in maintenance operations at the Molten-Salt Reactor
Experimbnt (MSRE). The use of television in MSRE maintenance operations

 

6. MSRE Remote Maintenance TV Camera and Preamplifier.

Ll
 

 

10

is presently limited to those operations associated with removal of
large components. For these operations large cell-access openings are
required, and the maintenance operations must be performed remotely from
a shielded maintenance control room. To supplement the direct view -
available through windows in the maintenance control room, indirect,
orthogonal viewing of these operations will be provided by two cameras
mounted on portable stands which can be moved by use of an overhead
crane., A third camera is also provided for use as an operating spare.
The cameras are radiation and shock resistant, and will withstand
continuous exposure to 1-Mev gamma radiation at a dose rate of about-
_'105 r/ hr for 100 hr without degradation of performance. Replacement -
of the vidicon tube and the lens will restore the camers gerformance
until the camera has accumulated a radiation dosage of 10° r. Each
camera is connected by 50 ft of radiation-resistant cable to a pre-
amplifier which, in turn, is connected by a 100-ft cable to a ‘camera
control unit. The preamplifier is not radiation resistant and must

be shielded from high-level radiation. The camersa control units for
the three cameras are mounted in a console in the maintenance control
room together with the monitors and associated camera controls.

Figure 7 shows the assembled console. Although three camera systems
are installed, only two monitors are used. A video switching system
permits the operator to display the signal fram any of the three cameras
on either or both monitors. The joy stick control mounted on the front
of the console table enables the operator to control pan, tilt, focus,
and zoom motions with wrist and finger actions. Other less frequently

PHOTO 85279

 

Fig. 7. MSRE Remote Maintenance TV Console Assembly.

:-’
 

4

11

used controls and adjfistméhts are located on the sloping panel in front

. -of the operator. Space was provided on the table for the addition of

crane controls. = it r:flfi -

" Except for the ViaicQfi tube and a sfidll?(nuvistor) vacuum tube in
the camera, the system uses solid-state components throughout .

The complete system produces hlgh-quality pictures, and performance
is stable over a wide range of variation of line voltage, line frequency,

- ambient temperature, and humidity. Except for a few minor failures which

occurred during the first few weeks of acceptance testing, the reliablllty
of the system has been excellent.

The design of this systemfiand the selection and procurement of
components was strongly influenced by prior experience at ORNL with
the use of closed-circuit television in maintenance operation at the
HRT and in the MSRE remote-maintenance demonstration facility.

~ CONCLUSIONS

. The HRT operations demonstrated that the use of television for
viewing in high-level radiation environments was practical. The tests
performed in the maintenance demonstration facility demonstrated that
orthogonal viewing was preferred to three-dimensional viewing for MSRE
maintenance operations. Both operations demonstrated that systems used

for remote maintenance must be rugged and easy to operate and must have

a high degree of performance and reliability. The conclusions drawn
from this experience have been supported and supplemented by the
experience gained by cthers in similar operations.

_ Since viewing eripment must be operable when needed maintenance
personnel have been understandably reluctant to use the- low-rellablllty

- equipment available in the past. This equipment used vacuum tube

circuitry throughout, was- sensitive to shock and vibration, and
reliability ranged from.marglnal to poor. It is my belief that the

“state of the art of closed=circuit television has now advanced to the 7

point where the performance and reliability of presently available

- . equipment are commensurate with the requirements for remote maintenance
- viewing and that the system installed at the MSRE w111'be a useful and
- vital tool in future maintenance operations. .

 
 

 
 
 
 
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