Research On Core Damage Assessment And Source Term

The experience of the Three Mile Island accident shows that emergency response organizations in severe accidents need timely and accurate judgment of the reactor core state for reliable emergency decision-making action.Core damage assessment method can effectively determine the core state and fission products released to the environment,can reduce the consequences of accidents to ensure public safety.Therefore,the core damage assessment method is of great significance to the accident management and emergency response of nuclear power plants.In this paper,the core damage assessment method of PWR at home and abroad is studied and the common points and differences of various methods are analyzed.On this basis,the characteristics of core damage assessment method of heavy water reactor are analyzed.Aiming at the characteristics of the release of fission products under severe accident,the steady state debugging and verification of the correctness of the model are carried out firstly.Then the typical accident category is chosen,and the behavior of noble gas and volatile fission products under big and small loss of coolant accident sequences are analyzed.Finally,the process of fission products migration in the containment and the fraction released to the environment are obtained.The results show that nearly all of the noble gas released from the reactor core is released to the environment,while less than 1% of the volatile fission products are released to the environment.Based on fully understanding the core damage assessment method and the fission products release of heavy water reactor,the core damage assessment interface system was developed by using C ++ language in Qinshan Phase III NPP.The system has the condition of unit state evaluation,core state evaluation and source term estimation.It can be used as a tool for power plant personnel training and core damage assessment under severe accident.The preliminary research of this paper can provide basic support for emergency response decision of power plant.