Interim Evaluation of the Thermal Stability of Cu-y-(85)Kr Sputter Deposits and Plans for Eventual Disposal.

摘要

A pilot process was developed and demonstrated for trapping and storing (85)Kr from the dissolver off-gas stream of a nuclear fuel reprocessing plant. Ions produced in a low-pressure krypton discharge are implanted on the inner wall of a krypton trapping storage device (KTSD). Objectives were to measure the release of (85)Kr implanted in a copper--yttrium alloy, outline the characterization work to be performed on the Cu(endash)Y(endash)(85)Kr waste form, and identify the options available for disposing of the remaining (85)Kr. Release rates were obtained from periodic measurements of the krypton released from both radioactive and nonradioactive krypton-loaded KTSDs. Sampling is expected to continue as long as the extrapolated release rates remain acceptable for a period not to exceed one half-life ((approximately)10 y). Seven tests were performed on a nonradioactive KTSD at 180 to 450C. Three KTSDs loaded with 80 to 150 Ci of (85)Kr stored at 150, 250, and 350C were sampled four times each. Proposed post-elevated-temperature storage characterization of the Cu(endash)Y(endash)(85)Kr waste form is outlined. Both radioactive and nonradioactive test specimens stored below 350C showed release rates less than 0.1%y. Release rates for the radioactive specimens were obtained for storage periods of 1.6, 1.1, and 0.4 y at 150, 250 and 350C. The nonradioactive specimen has been held at temperatures between 180 and 450C, but mainly at 350C for a total storage time of 2.1 y. Tests should continue for a period not exceeding 10 y, and then the remaining Cu(endash)Y(endash)(85)Kr waste form should be evaluated to better predict the overall stability. Three options for the disposal of the remaining ( 5)Kr. 3 refs., 2 figs., 2 tabs. (ERA citation 13:035849)