Design of a Second Generation Secondary Enclosure clean-Up System

An upgraded version of a metal hydride based clean-up system^a for tritium gloveboxes has been recently designed. An earlier version of a prototypical, recirculating system has been under evaluation in tritium service at OHT for nearly 2 years. A metal getter alloy, Zr₂Fe, is used to remove tritium and trace impurities from inert and nitrogen glovebox cover gas. The second generation SEC system features several notable improvements over its predecessor in areas of gas conductance, process instrumentation for tritium and moisture detection, and operator interface. A second bed has been added to enhance the removal of tritium and impurities. The system is controlled by computer programmed to automatically maintain the glovebox pressure, temperature and the impurity level of the glovebox cover gas, and to respond effectively to upset conditions by corrective action and to alarm the off-normal condition. The lifetime of the metal alloy getter is affected by the presence of impurities, notably moisture, which dictates the need to ensure system leak tightness. For example, the tritium concentration at the bed outlet will rise by approximately one order of magnitude as a result of introducing a continuous moisture load of 5 ppmv for 6 months while maintaining a flow rate of 2 L/s. The second generation system will be commissioned with tritium during 1995. a Metal hydride based clean-up systems utilize a metal getter. A metal hydride is a binary metallic compound or mixture produced when hydrogen is brought into contact with a metal.