Re: Radium Ice? -Reply

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

Paul's post on melting ice with the decayenergy from radium first
struck me as a straight forward calculation.  I think about it for a while
and realize that it is a lot more complicated.  It takes 333 joules
to melt 1 g of ice (2.1e15 MeV).  I did not add it up accurately, but
say there is 25 MeV of alphas and betas from radium and its daughters.
It then takes 8.3E13 Ra-226 decays to melt the ice. 8.3e13/3.7E10
(there goes the mantissa:)  gives 2250 seconds to melt its weight in
ice.  This assumes thermal isolation and a 0 C temperature.  It will then
under these conditions continue to rise in temperature at about 2 C/minute.

If you want to keep the ice melted under differing temperature and
isolation conditions you have to know a lot more including the
temperature differential, conductivity of the conducting medium,
thickness of the conducting medium, heat capacity of the conducting
medium, radiant power load, and probably a lot more stuff that
doesn't come immediately to mind.

Thanks guys, for the mental exercise.  After all you can't write
reports during lunch! 8)

The originator of the radium ice still has not replied to my request for 
more info.  I'll keep you posted.

Dale
dale@radpro.uchicago.edu