Under severe accident conditions, safety-related equipment must still be able to perform their functions during the accident. To ensure that it can perform its functions, it needs to withstand the working environment under severe accident conditions. To ensure the equipment can operate normally in a specific radiation environment and to prevent unacceptable degradation of performance due to radiation-induced changes, it is necessary to qualify the equipment for the radiation environment. This article analyzes and studies the radiation dose assessment methods for reactor buildings after accidents. The paper also analyzes the key nuclides affecting the identification of equipment after the severe accident. Through the analysis, it is known that in the early and middle stages after a severe accident, it is necessary to consider gamma radiation shielding against noble gases Xe-133 and I-133, in the late stages after a severe accident, it is necessary to focus on gamma radiation shielding against alkali metals Cs-134 and Cs-137. For beta-sensitive equipment, it is necessary to focus on beta radiation shielding against Xe-133, Kr-85 and I-133 in the early and middle stages after a severe accident and Cs-134、Cs-137 in the late stages after a severe accident. The analysis results can be used as a reference for optimizing the cumulative radiation dose of equipment after severe accidents.