The Research Of The Unstable Fission Gas Release Under The Condition Of Fuel Clad Breached

During the process of operating PWR,the fuel clad can't avoid breach.Once the fuel clad breached,the fission product accumulated in the fuel rod will release into primary coolant.Fission produced radiated gas is an important kind of radiation source.The process that the fission produced gas releases into primary coolant can be divided into 2 steps: The first is from pellet to the pellet-clad gap;the second is from pellet-clad gap to the primary coolant.So far,the research of the first step is quite mature and many kinds of relative programs were developed while few the research of 2nd step is done and the research is still immature;While the 2nd step is token into account,the release rate of fission products is considered to be linear to the number of the atoms in pellet-clad gap,and the two-phase flow is ignored,which lead large error in calculation.Due to the low solution of fission produced gas Kr,Xe,the process of release of fission produced gas can be considered as the process of two-phase flow.The micro-Channel composed of the breachedhole and the pellet-clad gap is formed.Until now,none of the computational correlation to calculate pressure drop and the distribute of two phases and components on this condition is established,so further research is necessary.