Year
1986
Abstract
Inventory differences (ID) in tritium material balance accounts (MBA) can occur with unmeasured transfers from the process or uniueasured holdup in the system. Small but cumulatively significant quantities cf tritium can leave the MBA by normal capillary sampling of process gas operation. A predictor model for estimating the quantity of tritium leaving the MBA resampling has been developed and implemented. The model calculates the gas transferred per sample; using the tritium concentration in the process and the number of samples, a quantity of tritium transferred i.s predicted. Verification of the model is made by PVT measurement of process transfer from multiple samplings. Comparison of predicted sample transfers with IDs from several MBAs reveals that sampling typically represents 50% of unmeasured transfers i'or regularly sampled processes. Another source of ID is unmeasured holdup of tritium in U-getter pumps. A method of measuring !,, holdup by D^ dilution has been developed ana1 applied to three different U-getter pumps at Mound. Replicate dilution experiments on the same pumps spread over a nine-month period indicates that getter pumps have holdup quantities related to regeneration performance.