High-Pressure Seawater Corrosion Test of a Multihundred-Watt Fuel Sphere Assembly, MHF-259

摘要

A Multihundred-Watt (MHW) fuel sphere assembly (FSA), MHF-259, was tested in the Los Alamos Scientific Laboratory's Hydrostatic Test Facility in 5 l of simulated seawater at 15 exp 0 C and 69 MPa (10,000 psi) for 300 days. This test was made to determine the effects of such exposure (seawater at 69 MPa) on the exp 238 PuO sub 2 fuel containment capability of an FSA and to compare the test results with those from an iridium-clad MHW sphere (MHFT-13), which was severely corroded during its 1-yr exposure to aerated seawater at atmospheric pressure (77.4 kPa). A plutonium release rate of < 0.1 pCi/m exp 2 -s was calculated from the plutonium concentrations in the seawater for both MHF-259 and MHFT-13 under equilibrium test conditions. When the pressure in MHF-259 was released after the initial 31-day exposure period, larger amounts of plutonium were washed through the vents in its iridium shell as the water that had been forced through the vents by the pressure came back out. The comparable release rate for bare exp 238 PuO sub 2 fuels is approx. 10 nCi/m exp 2- s. MHF-259 showed only minimal seawater corrosion damage and, we believe, would have been intact after its 300-day exposure to high-pressure seawater if its postimpact containment shell (PICS) had not been dented at the start of the long-term exposure. In contrast, MHFT-13 was severely corroded. Its PICS was corroded through in five locations adjacent to the closure welds after its 1-yr exposure at atmospheric pressure. The rresults indicate that exposure to high-pressure seawater does not seriously degrade the exp 238 PuO sub 2 fuel containment capability of the MHW-FSA. (ERA citation 04:056153)