Abstract
The safe storage of spent fuel assemblies in the spent fuel pools is very important. These facilities are not covered by leaktight containment; thus, the consequences of overheating and melting of fuel in the spent fuel pools can be very severe. On the other hand, due to low decay heat of fuel assemblies, the processes in pools are slow in comparison with processes in reactor core during LOCA accident. Thus, the accident management measures play a very important role in case of some accidents in spent fuel pools. This paper presents the analysis of possible consequences of fuel overheating due to leakage of water from spent fuel pool. Also, the accident mitigation measure, the late injection of water was evaluated. The analysis was performed for the Ignalina NPP Unit 2 spent fuel pool, using system thermal hydraulic code for severe accident analysis ATHLET-CD. The phenomena, taking place during such accident, are discussed. Also, benchmarking of results of the same accident calculation using ASTEC and RELAP/SCDAPSIM codes is presented here.
Highlights
The Tsunami that followed the earthquake at the FukushimaDaiici nuclear plants in Japan [1] showed that a loss of coolant can occur with the resultant effect on the spent fuel in the spent fuel pools
The consequences of such an event can be very serious creating a possibility of significant amount of radioactive material release to the environment. The consequences of such an accident can possibly be equivalent to the Chernobyl accident, which has been rated at 7 on the International Nuclear Event Scale (INES), because spent fuel pools are in general not housed in a containment with the same integrity as the containment around the reactor core and primary pressure boundary
The possible consequences of water loss due to the leakage and water injection to the spent fuel pool after fuel heat up are evaluated in this paper. The evaluation of this accident was performed for Ignalina NPP Unit 2 spent fuel pool, but it can be applied for spent fuel pools (SFP) of other reactor types
Summary
Daiici nuclear plants in Japan [1] showed that a loss of coolant can occur with the resultant effect on the spent fuel in the spent fuel pools The consequences of such an event can be very serious creating a possibility of significant amount of radioactive material release to the environment. The consequences of such an accident can possibly be equivalent to the Chernobyl accident, which has been rated at 7 on the International Nuclear Event Scale (INES), because spent fuel pools are in general not housed in a containment with the same integrity as the containment around the reactor core and primary pressure boundary As it is noted in the Operating Experience Feedback Report “Assessment of Spent Fuel Cooling” [2], during the operation time two losses of spent fuel pool coolant inventory events occurred and a decrease of water level by 1.5 m was registered. In order to apply it to other reactor type SFP, real characteristics of SFP, such as water volume, possible leakage rate and decay heat of fuel assemblies groups in SFP, etc. should be evaluated
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