Secondary containment system for a high tritium research cryostat

A 4.2- to 300-K liquid helium cryostat has been constructed for cryogenic samples of D--T containing up to 4 x 1014 dis/s (10,000 Ci) of tritium radioactivity. The cryostat is enclosed in a secondary box, which acts as the ultimate container in case of a tritium release. Dry argon is flushed through the box, and the box atmosphere is monitored for tritium, oxygen, and water vapor. A rupture disk and abort tank protect the box atmosphere in case the sample cell breaks. If tritium breaks into the box, a powdered uranium getter trap reduces the 4 x 1014 dis/s (10,000 Ci) to 4 x 109 dis/s (0.1 Ci) in 24 h. A backup palladium--zeolite getter system goes into operation if an overabundance of oxygen contaminates the uranium getter