How cold can I go...

["Randy Ross" <RNROSS@BCSC02.GOV.BC.CA>]

rnross@bcsc02.gov.bc.ca

"check equipment at very low temperatures"- so is the source always at the
cold temperature or do they have to cool it down every time they bring it in?
You say the source has been exposed to these temps for 6 yrs +or- Does that
mean its always somewhere around liquid He of N temps? This is
  important since as you can see from all the respondents the second most
frequent comment is with regard to cycling through the temp scale. The most
freq comment is "go see the metals people" Ha! The singularly most intelligent
comment so far is "if it ain't broke don't fix it" WHY? Why is that so
important in this potential radiation leakage situation? BECAUSE IT IS
EXPERIMENTAL EVIDENCE! Get another source from the manufacturer without the
radioactive cobalt and
  dunk the thing in and out or cryogenics 50 million times then ask a weld guy
to tell you if it is coming apart.

Finally what form is the cobalt in? Can it leak through a crack? Is its
physical state such that if it falls out of the sealed source it is in fact a
contamination problem?
What are all the other parts of the experiment made of?  Are there any welds
 in the steel - are the inspectors worried about that?  Follow up on that
 Co 60  form. Perhaps this is a non issue

The opinions and material above are solely those of the author.
This is a disclaimer for postings to bulletin boards, news
groups, etc., on the internet.
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X-Comment:  Radiation Safety Distribution List

     A  research  lab, where I work has to, upon occasion,  check
equipment  operation  at very cold temperatures i.e.  77  degrees
kelvin  (-195  C) or colder (4.2 K).  I'm sorry that I  can't  go
into specific details of why (and where).

     My  researchers  are currently using a 6 year old ICN  model
375  sealed  source  (Co-60) which for all of its life  has  been
exposed  to  these  extreme  temperatures.   Understandably,  the
manufacture  (which  no  longer manufactures these  sources)  was
surprised  at  the temperature at which their sources were  being
subjected  to  and is somewhat reluctant to guarantee that  their
sources are going to hold up to this treatment in the future.

     My  immediate  thoughts were along the path of "If it  ain't
broke,  then don't fix it", but, of course, it took an inspection
by  a  group  of bored inspectors to insist on  documentation  to
"guarantee" that it is a safe process.


     Questions:

     1.    Has anyone else had a similar experience?  Please tell
me about it.

     2.    Does  anyone have any concrete data on  whether  these
double-walled   stainless  steel  capsules  can  withstand  these
thermal  stresses  indefinitely - or until the source becomes  so
old as to be impractical...Inquiring minds want to know..


     Thank you all a head of time,

     Joel Baumbaugh  ( baumbaug@nosc.mil )