Optimization of NO/sub x/ and iodine removal in nuclear fuel reprocessing

Removal of nitrogen oxides and fission product iodine from the offgas generated by dissolution is essential in the reprocessing of spent nuclear reactor fuel. The species NO, NO2, N2O3, and N2O4 can account for as much as ten percent or the offgas generated by the dissolution of mixed oxide (Pu-O) fuels in nitric acid. While the radioisotopes of iodine are present in much smaller concentrations (only 15 grams are evolved in the dissolution of 500 Kg of 180-day cooled spent fuel), the radiological hazards it posses make the containment, partitioning, and disposal of iodine of paramount importance. A computer simulation which combines NO/sub x/ scrubbing with iodine liquidvapor partitioning and hydrolysis has been developed and used to evaluate a number of possible offgas system flowsheets. The conclusions reached using this simulation agree closely with experimentally obtained data. A generalized conclusion drawn from this study is that flowsheets which provide optimal processing of either NO/sub x/ or iodine do not provide optimal removal or both components. Therefore, compromises in flowsheet design must be made based on the operating parameters and offgas characteristics of each individual facility