Dissolution Of Irradiated MURR Fuel Assemblies Effect Of Increased Purge Rate And Catalyst Concentration On The Batch Size

Flowsheets for the dissolution of aluminum-clad spent nuclear fuel have been proposed using 0.002 M mercuric nitrate catalyst in 5 to 6 M nitric acid. Previous calculations for flammable gas control during the dissolution of spent nuclear fuel have been extended to cover a range of dissolver purge rates from 40 to 55 scfm. A range of dissolver solution volumes from 12000 to 15000 liters were considered for the large H-Canyon dissolver (6.4D). Depending on the purge rate, anywhere from four to six bundles of MURR fuel can be initially charged to the dissolver (6.4D). For successive charges where the dissolver solution already contains 0.002 M mercury catalyst and the dissolved aluminum from five bundles of MURR fuel, five to nine bundles of additional fuel can be charged depending on the purge rate and the dissolver solution volume. Similar calculations have been performed for the small H-Canyon dissolver (6.1D) for solution volumes that ranged from 6000 to 7500 liters and purge rates from 40 to 55 scfm. The limitations on the initial charge are four to six bundles depending on the purge rate. The aluminum from four bundles of fuel in an initial charge will allow nine to ten bundles in the second charge to 6.1D depending on the purge rate and dissolver solution volume. Solubility or criticality limitations will restrict the second charge on the small dissolver. The concentration of aluminum from previous charges will slow the dissolution rate to extend the cycle time of repeated charges of fuel. Calculations have been performed to allow a second catalyst addition (up to 0.004 M total catalyst) to reduce the cycle time (as necessary) based on the aluminum concentration and the purge rate.