Re: Pressure buildup in radium sources-Correction

[GELSG@aol.com]

The calculation of pressure build-up due to the three sources mentioned (radon
gas production, helium build-up, and dissociation of hydrogen and oxygen from
water of hydration left in the radium salts) is controlled by the assumed
"free volume" of space left in the radium needle or ampoule.  The larger the
volume of unoccupied space within the needle, the lower the pressure build-up.
The relative importance of the three potential sources would remain constant:
radon build-up will be of negligible importance compared to helium, and if any
water molecules are present within the encapsulated volume, both of the
previous potential sources of pressure would pale into insignificance compared
to the pressure increase caused by dissociation of the water into hydrogen and
oxygen.  If the radium salts were completely dry, and if the encapsulation
were perfectly gas tight, the pressure due to helium would continue to
increase in approximately a linear manner, with incremental increases
following the decay half-life of radium.  After enough time, quite high
pressures could be achieved from helium accumulation alone.

Gerald Gels
gelsg@aol.com