Implications for the Cryogenic Fielding of Leaking Beryllium Capsules

In this paper we show that the ambient temperature measured leakage time constant, _RT, is related to the leakage at cryogenic temperature, R_C, by

R_C = 0.23_DTV_sh/_RT

where _DT is the density of cryogenic DT vapor, and V_sh is the internal volume of the shell. We then calculate the size of voids that may result from leakage at the Be/DT interface, depending upon the number of leakage sites and _RT. Even for the slowest leakers the potential void growth is excessive. Reasons that voids have not been seen in DT layering experiments to date include the lack of a technique to see isolated micronish bubbles, however possible mechanisms preventing void formation are also discussed.