Comparison of silver sorbents for application to radioiodine control at the PUREX process facility modification. [Iodine 129]

In continued support of the design of the gaseous radioiodine control system for the PUREX Process Facility Modification (PFM), the Pacific Northwest Laboratory (PNL) conducted laboratory-scale measurements of the performance of four state-of-the-art sorbents for radioiodine in the dissolver offgas (DOG) of a nuclear reprocessing plant. The PFM is a new head-end treatment plant being designed by Westinghouse Hanford Company (WHC) for the PUREX Plant at the Hanford Site. The experiments performed measured the iodine effluent concentration from Norton silver mordenite (NAgZ), Linde silver mordenite (LAgZ), Linde silver faujasite (AgX), and silver nitrate-impregnated silicic acid (AgNO/sub 3/Si) during simulated normal operating conditions in the PFM after three shutdown/startup cycles, and during standby. At normal operating conditions the input gas is expected to have a dew point of 35/degree/C to 40/degree/C and contain 0.1 ..mu..mol I/L, 1 vol% NO, and 1 vol% NO /sub 2/. The sorbent bed would be at 150/degree/C. A shutdown/startup cycle consisted of eliminating iodine and NO/sub x/ from the input gas, cooling the bed to room temperature, stopping gas flow, and restarting the system. During standby conditions the input gas contained no iodine or NO/sub x/, the dew point was at 30/degree/C to 35/degree/C, and themore » bed temperature remained at 150/degree/C. This experimental study showed that 20 cm beds of NAgZ, LAgZ, and 18 wt% silver AgX could load up to 0.25 mmol I/g sorbent and routinely reduce the iodine concentration in a simulated PFM DOG from 0.1 ..mu..mol I/L to less than the target level of 10/sup /minus/5/ ..mu..mol I/L. In contrast, the AgNO/sub 3/Si unexpectedly failed to achieve this required level of performance, reducing the concentration on a routine basis only to 10/sup /minus/4/ to 10/sup /minus/2/ ..mu..mol I/L. 5 refs., 14 figs., 6 tabs.« less