ORNL-4191 - the Molten Salt Energy Technologies Web Site

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Table 2.1. Radiation Levels Following Steps in Decontamination of an MSRE Sampler-Enricher Manipulator Hand
_____I____
Cleaning Radiation Level
Cleaning Treatment Time Ntri Treatment
None (as received)
Detergent (Duz) jet Spray
Rinse (water)
Detergent (Duz) jet spray
Formula 50
Dilute HNO,
Bolt freeing solvent with acetone tinse
Concentrated HNO,
Scrub with scouring powder (&IB-O)~
Scrub with scouring powder (BaB-0)
Formula 50
Concentrated HNO,
Scrub with scouring powder (Ran-0)
Clean with concentrated HNO,
Acetone rinse
smears '
aRemoved to laboratory hood.
bZirconium and rutlienium.
CIn disintegrations per minute.
system and in planning for maintenance of the
components. On the basis of these needs, a study
of possibly useful devices was started.
The concept of the pinhole camera using radiation
shielding and gamma-ray-sensitive film was
evaluated dong with a system using a portable
collimator and a small gamma-sensitive dosimeter.
It was determined that while the camera method
was feasible, the results to date did not provide
very good resolution of position, intensity, and
size. The problem of calibration of the film for
use in radiation fields of unknown energy appeared
difficult. However, the time required to survey an
area would be short, approximately Equal to the
required exposure time for the film. The use of
the collimator method would take longer to complete
a survey, but possibly could yield better
resolution. This method also offered the potential
of giving information on the gamma-ray energy
spectrum of the source. A series of experiments
with the collimator was conducted to evaluate the
method, with the results described below.
(min) (r/hr)
5
5
10
10
5
10
5
5
5
5
5
5
5
300
100
75
25
7.5
5.0
3.0
0..5--1.0
0.2-1 .o
No reduction
No reduction
No reduction
0.2-0.3
No reduction
800-13, O0OC
Experiment with a 5-curie 137@s Gamma Source
A collimator was constructed by casting lead in
a 4-im-diam steel pipe 48 in. long and providing a
1-in.-diam hole the length of thc tube. The collimator
tube was placed in a suitable hole in the
portable shield which was positioned over a pit
containing a S-curie I3'cs source.
Radiation measurements were made with the
equipment and source arranged as shown in Fig.
2.3. The radiation source could be raised and
lowered, and the collimator tube could be moved
horizontally over the source. Weasurcments were
made with the source 13 ft and 15 ft 6 in. below
the top of the portable shield. The source was
about f/4 in. in diameter and 2 in. long and was
enclosed in a 1-in.-diam tube 5 in. deep in the
carrier.
The results of the radiation measurements are
shown in Fig. 2.4. It will be noted that as the
collimated ion chamber was moved horizontally
over the source, the radiation readings changed