Main Results of Post-Irradiation Examinations of Vibropac Oxide Fuel Pins

By the moment SSC RF RIAR has carried out a comprehensive scope of R&D activities to validate vibropac oxide fuel pins serviceability in fast and thermal reactors. In fulfilling the activities physical-mechanical and technologic characteristics of granulated fuel have been studied, in-pile tests and material examinations have been carried out for mock-up, experimental and pilot fuel pins of the BN-type (in the BOR-60, BN-350 and BN-600 reactors) and the VVER type (in the SM-2 and MIR). More than 30 000 fuel pins have been tested up to nowr. The BOR-60 standard fuel assemblies and experimental fuel pins in dismantled FA have achieved peak burnups of 30%h.a. and 32.3%h.a., respectively. UPuO₂ vibropac fuel pins have been tested up to the peak burnup of 10.8%h.a. in the BN-600 and up to 43000 MWday/t in the MIR. Besides, experimental fuel pins, using (UO₂+Np) fuel composition, have been tested. Burnup of 16.4% has been achieved. Tests are under way.

According to MINATOM Concept on the disposition of plutonium to be released as a result of nuclear weapon dismantling State Scientific Center of Russian Federation Research Institute of Atomic Reactors started practical implementation of the MINATOM Concept on converting weapon grade plutonium into MOX-fuel using pyroelectrochemical processing and vibropacking technology. To date 32 fuel assemblies have been fabricated for the BOR-60 and 3 FA for the BN-600.

The report presents main results of postirradiation examinations for vibropac oxide fuel pins. It is shown, that problems of thermal-mechanical and chemical interactions in fuel pins, using vibropac (UPuO₂ + U) fuel, have already been solved and serviceability of fast reactor fuel pins depends on cladding material selection.