Abstract: The limits of radioactivity concentration in primary coolant during the time of the pressure vessel head opening for shutdown are the important design parameters of PWR, which lack the design methodology in a long time. In this paper, the evaluation methods of radioactive concentration control value in the primary coolant during the time of RPV opening are established for PWR,based on the analysis of the sources of radiation risks after pressure vessel head opening,. This methodology has been verified by comparing with original ERP design results.

Key words: RPV head opening in shutdown, coolant, concentration limit, PWR, radiation risk