[ RadSafe ] Low temps and CF-252 sources

[Brian Rees]

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,
Brian Rees