Effect of Surface Oxidation, alpha Radiolysis, and Salt Brine Composition on Spent Fuel and UO sub 2 Leaching Performance: Salt Repository Project.

摘要

This report describes the results of three different series of leach tests on spent fuel and unirradiated UO sub 2 designed to aid in the safety evaluation. Also described are the results of associated tests that involved (1) the surface characterization of spent fuel specimens and (2) the determination of alpha and beta/gamma dose rates associated with spent fuel leach tests. One leach test series was designed to compare the leach performance of spent fuel in different brine compositions; one brine consisted primarily of NaCl, and the other contained large amounts of MgCl sub 2 as well as NaCl and other salts. The other two leach test series were designed to investigate a difference between spent fuel and unirradiated UO sub 2 that was reported previously (Barner et al. 1986). In one of the latter series, leach tests were performed on UO sub 2 that had been doped with Pu to simulate the alpha activity of spent fuel specimens. In the final series, leach tests were conducted on spent fuel specimens that originated in the same reactor assembly as those used in previous tests but were handled differently following discharge from the reactor. The spent fuel leach tests in different brines led to similar results except for higher Pu concentrations in the high-Mg brine. Alpha radiolysis was found to have little effect on the mass loss of U from UO sub 2 in the air-saturated brines used in these tests. Most of the difference between spent fuel and UO sub 2 observed in previous tests appears to be attributable to alteration of the surfaces of the spent fuel specimens during storage after they were discharged from the reactor. 18 refs., 21 figs., 8 tabs. (ERA citation 13:056313)