Containment of $sup 90$SrF$sub 2$ at 800 to 1100$sup 0$C preliminary results

A program is currently underway at PNL to develop the data needed to license $sup 90$SrF$sub 2$ for heat source applications. A major portion of the program involves determining the compatibility of $sup 90$SrF$sub 2$ with containment materials at elevated temperatures. The compatibility studies are divided into two phases: an initial series of short-term scouting tests lasting up to 4400 h in which a number of containment materials were evaluated, and a subsequent series of long-term tests in which the three best containment materials identified in the short-term tests will be tested for up to 30,000 h with WESF-produced $sup 90$SrF$sub 2$. The results of the first phase tests are summarized. The short-term tests were carried-out at temperatures of 800, 1000, and 1100$sup 0$C for 1500 and 4400 h using both radioactive and nonradioactive strontium fluoride. Nine potential containment materials were evaluated in the tests: two refractory metals (tungsten and TZM); two cobalt base alloys (Haynes Alloy 25 and Haynes Alloy 188); and five nickel base alloys (Hastelloy C-276, Hastelloy X, Hastelloy N, Inconel 600 and Inconel 625). Test results show that both of the refractory metals are very resistant to fluoride attack, and tungsten and TZM specimens exposed to $sup 90$SrF$sub 2$ exhibited little or no attack. Haynes Alloy 25 was the best of the Ni- and Co-base alloys, but attack up to a depth of 0.004 in. was observed in some Haynes Alloy 25 specimens exposed to $sup 90$SrF$sub 2$. Based on the results of the short-term compatibility tests and several other factors, TZM, Haynes Alloy 25 and Hastelloy C-276, the present WESF capsule material, were selected for long-term testing with $sup 90$SrF$sub 2$. (auth)