Tritium In-Bed Accountability for a Passively Cooled, Electrically Heated Hydride (PACE) Bed

A PAssively Cooled, Electrically heated hydride (PACE) Bed has been deployed into tritium service in the Savannah River Site (SRS) Tritium Facilities. The bed design, absorption and desorption performance, and cold (non-radioactive) in-bed accountability (IBA) results have been reported previously. Six PACE Beds were fitted with instrumentation to perform the steady-state, flowing gas calorimetric inventory method. An IBA inventory calibration curve, flowing gas temperature rise (T) versus simulated or actual tritium loading, was generated for each bed. Results for non-radioactive (“cold”) tests using the internal electric heaters and tritium calibration results are presented.

Changes in vacuum jacket pressure significantly impact measured IBA T values. Higher jacket pressures produce lower IBA T values which underestimate bed tritium inventories. The exhaust pressure of the IBA gas flow through the bed's U-tube has little influence on measured IBA T values, but larger gas flows reduce the time to reach steady-state conditions and produce smaller tritium measurement uncertainties.