Re: Pressure Buildup in PuBe Sources

[dsimpson@unlnotes01.unl.edu]

In reply to the concern about pressure buildup in PuBe sources, the concern
probably stems from RaBe sources which primarily predated the PuBe sources.
RaBe sources were well known for pressure buildup due to helium from alpha
decay, (not from Rn-222 as most people first guess - the Rn quickly reaches
equilibrium due to its short half-life).  Another problem with early
sources was that not enough gap was allowed inside the source to accomodate
the small amount of gas production, so pressures tended to rise more
quickly.  My guess is that PuBe sources would not show much of a pressure
buildup because they are more likely to have some allowance in their design
for He production and probably even more significant,  the immediate Pu-239
decay product (U-235)has a much longer half-life than the Ra-226 decay
products, so less helium gas is produced.


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