Comparison of subcriticality of the interim spent fuel storage before and after modification

Full text: After political and economical changes in the end of eighties, the utility operating the nuclear power plants in Slovakia decided to change original scheme of the back-end of the nuclear cycle; instead of reprocessing in the USSR/Russia spent fuel will be stored in an interim spent fuel storage facility until the time of the final decision. As the best solution, a modification of the existing interim storage has been realised. In existing interim storage is used new basket with new shape and with compact racks from boron steel. In Slovakia they are in operations 6 units WWER-440. The original capacity of the interim storage is 5040 assemblies, after modification is 14,112 assemblies. The original type of fuel (used in operation and stored in the interim storage) has maximal enrichment 3.6%. The current type of fuel (now used only in operation, not in storage) has radial profiled enrichment with maximum 4.0%. The advanced fuel (will be in operation after 2005) has maximal enrichment 4.4%. The subcriticality both baskets with different fuel by operational conditions: C-30 KZ-48 3.6% 0.85287 0.83384 4.4% 0.88489 0.87477. In article are compared criticality both baskets by abnormal conditions: mechanical destruction or loss of coolant. New basket make possible to increase 2,8 times the capacity of interim storage and is more safety than older one. (author)