Bokov A.A.1,2, Pavlov S.V.2, Teplov V.G.1
1 Research Institute of Atomic Reactors, Dimitrovgrad, Russia
2 Dimitrovgrad Institute of Engineering and Technology – Branch of the Nuclear Research University “Moscow Institute of Engineering and Physics”, Dimitrovgrad, Russia
The results of the study of changes in the free volume of WWER-1000 fuel rods of various designs from the burnup of nuclear fuel are considered in the article. The free volume of fuel rods was determined experimentally in the process of post-reactor studies of irradiated fuel in JSC “SSC RIAR”. A total of 322 fuel rods from 26 fuel assemblies operated at various nuclear power plants were investigated. Seven different designs of WWER-1000 fuel rods were investigated, including fuel rods with a thin cladding and with fuel pellets without a central hole. The burnup of nuclear fuel in the studied fuel rods is in the range from 16 to 72 MW·day/kgU. There are three conditional stages of changing the free volume of fuel rods: before the first contact of the fuel with the cladding, from the first contact to the contact of most of the fuel column (up to 95 %) with the cladding, and after the contact of most of the fuel column with the cladding. Empirical dependences of the change in free volume on burnup for fuel rods with different design are obtained. The results obtained can be used to verify models and calculation codes describing the behavior of WWER-1000 fuel rods during operation, as well as during long-term storage after operation.
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