Application Of The Passive Safety System To Fusion-fission Hybrid Reactor And Safety Analysis

The insufficience of235U and how to dispose the spent fuel and nuclear waste arethe two key problems in the development of nuclear fission energy. Although it still along way to the comprehensive business application, nuclear fusion energy is cleanerand more safe. The fusion-fission hybrid reactor may be a feasible way to takeadvantage of fusion energy before the comprehensive business application is achieved.The fusion-fission hybrid energy reactor and its blanket cooling system are inconceptual design stage at recent time.The passive safety system is applied tofusion-fission hybrid reactor in this paper. The main object of this paper is to verify thatthe passive safety system can meet the safe requirements of hybrid energy reactor.ARELAP5model for the fusion-fission hybrid energy reactor had been developed torepresent the subcritical energy blanket, main cooling system and the passive safetysystem.Several categories of typical accidents, including stuck pump accident, small breakLOCA on cold leg andlarge break LOCA on cold leg, were selected to analyze. Thechange of the key transient parameters and the behavior of the passive safety syytemwere observed and analyzed. During thestuck pump accident, the pressure of theprimary system and the maximum temperature of fuel were in the safety margin. CHFdid not occure on the surface of the fuel. The decay heat of the subcritical energyblanket can not be exported by the PRHRs after the isolation of main feedwater.Theheat exchange amount of the PRHRs had great increase so that the decay heat canbe exported effectivelywhile the flow area of the heat exchanger of the PRHRs wasoptimized. During the2inch,4inch and10inch small break LOCA on cold leg, the fuelzone of the subcritical energy blanket was alway covered by water and the maximumtemperature of the fuel was belowthe limit all the time due to the response and action ofthe passive safety system. In order to increase the minimum value of collapsed liquidlevel, increasing the volume of ACC and increasing the volume of CMT were conductedin this paper. The results indicated that the minimum collapsed liquid level greatlyincreased if doubling the volume of CMT,but the result of doubling the volume of ACCis of significance.During the large break LOCA, the fuel of the subcritical energyblanket was exposed immediately and the temperature of the fuel increased rapidly. There are two peak fuel temperatures which are under the melting point of fuel, U-10Zrin the outer blanket in the process. The first peak fuel temperature is938.2K at about11s and the second is608.7K at about50s.The mitigation capability of the passive safety system to the accidents was studiedin the mentioned safety accidents. The optimization of the passive special safetyfacilities was pointed out. It is feasible to apply the passive safety system concept tofusion-fission hybrid enregy reactor.