Results from post-reactor examination of two WWER-440 fuel assemblies spent at the Kola NPP Unit 3 during 4 and 5 fuel cycles are presented. The fuel assembly states and their serviceability allowance are estimated experimentally at the RIAR hot laboratory and studied by non-destructive and destructive methods. The following parameters are examined: fuel assembly overall dimensions change; fuel element diameter change; fuel element cladding corrosion and hydriding; fuel element cladding mechanical properties; fission gas release from fuel and gas pressure; fuel macro- and microstructure. it has been found that the maximum fuel burnup of fuel assemblies No. 1 and No.2 achieved is 58.3 and 64.0 MWd/kg, respectively. The mechanical fuel pellets-cladding interaction has been observed at the average fuel burnup above 45 MWd/kg that occurred with increasing the local cladding diameter at the areas of pellets end arrangement (bamboo stick). The gas release linearly increases at the range 2.7% per 10 MWd/kg within burnup of 43-60 MWd/kg. 9 figs., 3 refs.
Smirnov, A; Ivanov, V; Pnyushkin, A;  Tzibulya, V;  Kolosovsky, V; Bibilashvili, Yu;  Dubrovin, K 
- Nauchno-Issledovatel`skij Inst. Atomnykh Reaktorov, Dimitrovgrad (Russian Federation)
- AO Mashinostroitelnij Zavod Electrostal (Russian Federation)
- Vsesoyuznyj Nauchno-Issledovatel`skij Inst. Neorganicheskikh Materialov, Moscow (Russian Federation)
- Russian Research Centre Kurchatov Inst., Moscow (Russian Federation)