Abstract: The trend of inert gas radioactivity level inside NPP containment was forecasted, using operating data in normal and abnormal working conditions (or accident). It was then validated with online monitoring data. This provides an important anticipation to the safe and stable operation of the nuclear power. When an abnormal event or accident happens, the response decision can be taken with the forecast data used. In this paper, combinedthe actual operation data of NPP, a prediction method of inert gas radioactivitylevel inside the containment is briefly summarized.

Key words: Containment, Radioactive inert gas, Emergency response