Fuel: Performance Envelope of Modern HTR TRISO Fuel Report

The reference fuel design for PBMR fuel is the fuel manufactured in Germany during 1988 for HTR-Modul Proof Tests. This design is underpinned by an extensive experimental database consisting of irradiation tests on individual fuel samples under controlled conditions as well as bulk irradiation tests involving several thousands of fuel spheres under reactor operating conditions in the AVR. Fuel samples from both types of irradiation test were subjected to heating tests, simulating loss of forced cooling temperature transients that could be expected to occur in operating HTR cores, with excellent results. German fuel types that are relevant to the PBMR fuel design and operating conditions are discussed in terms of their basic characteristics, differences, and similarities. Although most of the experimental results have been reported previously in IAEA Tecdoc 978 [2], results from some recent tests as well as revised results for tests already reported in the Tecdoc are presented. Irradiation and heating test results from the German database are described and used to establish a performance envelope for modern HTR TRISO fuel. (author)