Source item analysis method and system for reactor water loss accident

The invention relates to a source item analysis method and system for a reactor water loss accident, and the method comprises the steps: obtaining a decay constant and a settlement factor of radionuclide, obtaining the leakage rate of a containment vessel in real time, and calculating the concentration of radionuclide in the containment vessel in a transient process; calculating the current radionuclide concentration in the cabin according to the ventilation rate of the cabin, the current containment leakage rate, the radionuclide concentration in the containment at the previous moment and the radionuclide concentration in the cabin at the previous moment; obtaining the filtering efficiency of the ventilation system of the cabin to the radionuclide, and calculating the concentration of the radionuclide released to the environment at the current time period; and calculating the total release amount of radionuclides to the environment during the whole accident period. According to the technical scheme, when a r