During the operation of the reactor, the large break of the fuel rod will cause the release of fuel core materials and the obvious rise of the source term in primary coolant circuit, which will affect the safe operation of the reactor. In this paper, the fuel damage status is evaluated based on the measured value of the source term of a nuclear power plant. The analysis shows that there is a large break in the core fuel rod and the release of fuel, which is basically consistent with the damage inspection results after shutdown. Research shows that in the case of a large break in the fuel rod, the source term of the primary coolant circuit has the following characteristics: there is the continuous rise of 134I source term in coolant; the activity spectra of typical fission products are similar to those of contaminated uranium; and there is no obvious iodine peak during power transient; and 239Np source term in coolant could be detected. These laws can be used to analyze the fuel damage of the reactor and help to identify the large fuel rod break in the reactor core. Copyright ©2021 Nuclear Power Engineering. All rights reserved.
