Irradiation Performance of Fort St. Vrain High-Temperature Gas-Cooled Reactor Fuel in Capsule F-30

Abstract

Representative production fuel fabricated for the Fort St. Vrain (FSV) high-temperature gas-cooled reactor (HTGR) was tested in capsule F-30. The irradiation conditions experienced by the fuel encompassed the FSV service conditions designed for a 6-yr fuel cycle. Fuel specimens were irradiated at temperatures ranging from 825 to 1250/sup 0/C (1098 to 1523 K) and to a peak fast-neutron exposure of 9.4 x 10/sup 25/ n/m/sup 2/ (E greater than 29 fJ)/sub HTGR/, which is 18 percent beyond the design FSV peak fast-neutron exposure. In-pile fission gas release measurements and postirradiation examination indicated good irradiation stability of the fuel specimens. The 13 bonded fuel rods were intact, and their irradiation-induced dimensional changes were in good agreement with dimensional change curves used in the FSV core design. Total fuel particle failure fractions determined by visual examination, metallography, and fission gas release measurements were consistent with the criterion of less than 1 percent failure at peak exposure conditions assumed in FSV design and licensing evaluations. Fuel performance in the FSV reactor was evaluated using the capsule F-30 irradiation results. The good irradiation behavior of production fuel in this test gives a high degree of confidence in the performance of the FSV core throughoutmore » its lifetime and demonstrates the conservative nature of the FSV fuel particle design.« less