THERMAL ASSESSMENT OF NEW IGNALINA NPP CASKS FOR SPENT NUCLEAR FUEL STORAGE AT SOME ABNORMAL CONDITIONS

Abstract

Thermal assessment of new design casks CONSTOR^® RBMK-1500/M2 for interim storage of spent nuclear fuel in the new storage facility at the Ignalina Nuclear Power Plant has been performed for a some even thought very unlikely, but hypothetically possible abnormal conditions – when the cask becomes leaky and looses helium filler, when the cask is erroneously loaded with inner basket containing spent nuclear fuel of highest decay heat power, and when the ventilation regulation system of the storage hall fails to open shutter grids for a long time under extremely hot weather conditions. The ALGOR numerical calculation code (USA) was used for modeling of temperature fields in the cask located in the storage facility and loaded with spent nuclear fuel cooled in water pools for 5–7 years.

The calculations showed, that in the cases of cask leakage and cask erroneous loading, the maximum temperatures in the inner basket zone will exceed the maximum allowed fuel rod cladding temperature for long-term storage (normal) conditions (300°C), but not exceed the maximum allowed short-term temperature in case of an accident conditions (570°C). Temperatures in the ring basket zone practically will not exceed the maximum allowed temperature for normal conditions in both investigated cases. Failure of the ventilation regulation system of the storage hall will not lead to significant consequences. Maximum temperatures in the inner and ring basket zones practically will not exceed maximum allowed fuel rod cladding temperature for normal conditions. Temperatures of the cask body concrete filler in all investigated cases will never exceed the maximum allowed temperature for concrete in case of an accident conditions (177°C).

DOI: http://dx.doi.org/10.5755/j01.mech.19.2.4153