DETERMINATION OF THE NUMBER OF EVALUATION TESTS FOR FUEL ASSEMBLIES

摘要

When substantial changes are made in the design of fuel assemblies (the structural material, fuel type, and so on are changed) or in their lifetime characteristics, in situ (reactor) evaluation tests must be performed in order to assess the degree to which such changes affect reliability. This raises the question of the number of tests that must be performed. The normative documents do not answer this question. In practice, experts make the evaluations. In the present article, a variant of an analytical estimate of the number of evaluation tests that must be performed on fuel assemblies is proposed. The main indicator determining fuel-assembly operability is the seal of the fuel elements over the entire period of irradiation in a reactor. It is necessary to determine the number of fuel assemblies that must be irradiated in order to conclude with confidence probability α that they satisfy the established reliability requirements.