Application of MCNP Code in Shielding Calculation of Minitype Fast Reactor

An accurate shielding calculation model has been set up for the minitype sodium-cooled fast reactor （MFR） based on MCNP code and particular calculation of its primary shielding parameters has been carried out. The results indicate that the photon and neutron flux density of MFR has rapidly fallen to a low-level. The material for the shielding layer outside of main container is primarily of carbon steel, which can be design as a shielding structure satisfing the safety code. The sodium activation in primary circuit is extremely limited and it is simple to shield from. Both the output of helium in reflecter and burn up of boron-10 in control rod are very small. These materials can be used for several cycle lives.