An approach for evaluating fuel system applied in innovative nuclear energy system

One of the important issues in the study of Innovative Nuclear Energy Systems (INES) is the integrity of the fuel system applied. An approach of evaluating fuel system integrity is discussed here based on the procedure currently used in the integrity evaluation of fast reactor fuel. The fuel failure modes controlling fuel life were reviewed and fuel integrity was analyzed and compared with the failure criteria. Metal and nitride fuels with austenitic and ferritic cladding tubes were examined in this study. For the purpose of representative irradiation behavior analyses of the fuel for INES, the correlations of the cladding characteristics were modeled based on well-known characteristics of austenitic modified 316 SS (PNC316), ferritic-martensitic steel (PNC-FMS) and oxide dispersion strengthen steel (PNC-ODS). The analytical result showed that fuel lifetime is limited by channel fracture which is a nonductile type (brittle) failure associated with a high level of irradiation-induced swelling in the case of austenitic steel cladding. In the case of ferritic steel, on the other hand, the fuel life is controlled by cladding creep rupture. The lifetime evaluated here is no more than 200 GWd/t, which is still lower than the target value 400 GWd/t burnup. Possible measures to extend metal fuel lifetime may be reducing fuel smear density and ventilating fission gas in the plenum. ► The integrity of fuel having ultra high burnup of about 40 at.% was evaluated by use of the cladding characteristics which are newly determined based on well known information with for example PNC316 and PNCODS. ► Metal, oxide and nitride are considered as fuel material and austenitic stainless steel and ferrite stainless steel are considered as cladding material. The integrity of fuel system composed of the combination of these materials was evaluated. ► It might be probable that the integrity is maintained if ferrite stainless steel is used as cladding material due to its very low swelling. However, the improvement of creep rupture strength is desired.