Abstract: The intake air gamma radiation monitoring alarm threshold of nuclear plant main control room was studied for both normal and accidental conditions. For two different layout schemes, gamma radiationdose rates of measuring points was calculated with the MCNP code for three typical accidents including S3, DBA-LOCA and LOCA. The results show that it is proper to keep original value of the detector alarm threshold for the main control room after improvement, which could provide effective radiation protection for indoor staff.

Key words: Main control room, γ dose rate, Alarm threshold