Radiological Assessment of the Dose Distribution Around Reactor Pressure Vessel

Abstract

For a reasonable design of a decommissioning scenario, the dose distribution around the reactor pressure vessel of a commercial nuclear power plant (NPP) was assessed preferentially using an MCNP code based on the concentration of ⁶⁰Co. The regions of the dose calculation were composed of two parts; one is between the reactor pressure vessel and the biological shield of a cylindrical-type and the other is at the reactor pressure vessel pool of a rectangular-type. The highest dose value was 22.9 Sv/h at 4.35 m from the bottom of the reactor pressure vessel and the lowest dose value was 10.8 mSv/h at the top of the biological shield. It was shown that the dose is so high that workers could not work around the reactor pressure vessel without radiation protective actions based on the domestic criteria (100 mSv/5 yrs and 50 mSv/yr).