Nuclide Emission Law Under Typical Severe Accident

Nuclear power is the most important tool in China,and it is an important embodiment of China’s comprehensive national strength and international influence.As an important clean energy,nuclear power has integrated into human production and life to a great extent,but the development of nuclear power still has limitations,especially after the Fukushima nuclear accident,the safe operation of nuclear power station has become the most concerned problem.The study of radionuclide emission law under typical severe accident conditions of nuclear power plant,especially under the condition of containment bypass or failure,can help nuclear power plant improve the emergency plan for severe accidents,and ensure the living environment and personal safety of people around nuclear power plant to the greatest extent.Based on the data of reactor parameters,I establish the calculation model of radioactive source term and calculate the initial value of radionuclide core.Selecting three typical severe accidents of nuclear power plant:Large Break Serious Accident,Steam Generator Heat Transfer Tube Fracture Serious Accident and ADS Valve Mistakenly Opened Serious Accident.I establish the relevant accident analysis model,and compile the program input card for simulation calculation.Through the relevant accident assumptions,I calculate the specific accident process,and analyze the thermal hydraulic response of the accident,select three kinds of representative radionuclides under serious accidents for calculation and analysis.Studying the emission of radionuclides from three typical serious accidents,and the results of radionuclide emission of the containment under the conditions of failure,I compare early failure and bypass.It can be seen that noble gas radionuclides mainly release in the core,with the largest proportion,and all exist in the form of steam and aerosol,with high diffusion intensity.Almost all of them migrate to the containment space after the accident,and finally release to the environment;Volatile radionuclides mainly release in the core,and their chemical properties are active.They mainly deposit on the thermal components and dissolved in water.The proportion of volatile radionuclides release to the environment is small,and almost all of them remain in the containment;The non-volatile radionuclides mainly exist in the form of deposition on the thermal components,and their release into the environment is the least,less than 1%.Based on the three types of nuclear reactor severe accidents,the results of radionuclide emissions under three conditions of containment failure,it compare early failure and bypass.In the case of containment failure,the proportion of the three radionuclides discharge into the environment is very small.However,when the containment failure or bypass occurs,almost all the noble gas radionuclides migrate to the environment,and the proportion of volatile and non-volatile radionuclides will also increase.The results show that the integrity of containment is binding on inert gas and volatile radionuclides,and can effectively prevent the emission of radionuclides to the environment.According to the calculated results,it select the proportion of three kinds of radionuclides discharged into the environment and compare with the relevant accident results calculated by other programs,and the comparison error of the results is within the acceptable range.