[ RadSafe ] Low temps and CF-252 sources
Baumbaugh, Joel SPAWAR
joel.baumbaugh at navy.mil
Sat Feb 16 13:20:56 CST 2008
Below (in larger font) is a similar question that I asked/posed on RADSAFE "quite" a few years ago...(1995). What type of sources are YOUR researchers using? The sources in my question below were ICN-375's and they were/are pretty rugged sources. The sources are still in use to this day and (knock on wood) have had no leakage problems (they just don't make them like they used to.. LOL).
When I last asked my question to RADSAFE, no one had had a similar experience with extreme cold and sources - in my case using dry-ice (-109.3 F) to initially cool the sources, and then into liquid nitrogen (-321 F) and then into liquid helium (-452 F). I think that the greatest potential for damage is the thermal shock - especially w/the welds - which we tried to minimize w/the cooling routine above.
Here was my initial question:
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 as to 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.
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..
So, Brian, in my case, so far so good.... I hope that your researchers are VERY careful w/the sources at these temperatures - don't knock/hit them against anything as the metal DOES become quite brittle... I always swiped them before after use (when they were warmed back up to room temperature of course)...
Hope this has helped...
Joel Baumbaugh - SSC-SD...
From: radsafe-bounces at radlab.nl on behalf of Brian Rees
Sent: Fri 2/15/2008 2:34 PM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Low temps and CF-252 sources
We have a researcher that in interested in taking a Cf-252 source to 77k
(-196C) - Liquid N2 as part of an experiment. I assume the encapsulation
is not tested to that low a temp, and I would have concerns about brittle
fracture and/or thermal expansion/contraction induced cracking of the
encapsulation - not something I would want to deal with! Other than
speculation (which we are also quite capable of) does anyone have any
information or experience in this realm?
Thanks in advance,
More information about the RadSafe