The construction of China Spallation Neutron Source (CSNS) has been initiated in Dongguan, Guangdong, China. Thus a detailed radiation transport analysis of the shutter neutron beam stop is of vital importance. The analyses are performed using the coupled Monte Carlo and multi-dimensional discrete ordinates method. The target of calculations is to optimize the neutron beamline shielding design to guarantee personal safety and minimize cost. Successful elimination of the primary ray effects via the two-dimensional uncollided flux and the first collision source methodology is also illustrated. Two-dimensional dose distribution is calculated. The dose at the end of the neutron beam line is less than 2.5 μSv/h. The models have ensured that the doses received by the hall staff members are below the standard limit required.
For the PWR power plant in service, the lifetime of RPV is mainly determined by fast neutron (E>0.1MeV and E>1.0MeV) fluence. A new Low-Leakage Core Loading (LLCL) pattern is considered to prolong the lifetime of RPV to 60 years for Daya Bay nuclear power plant. Fast neutron (E>0.1MeV and E>1.0MeV) flux inserted to Reactor Pressure Vessel (RPV) under LLCL pattern is calculate by MCNP and compared with that under Long-Short Alternating Core Loading (LSACL) pattern. The results show that fast neutron fluence over inner surface of RPV under LLCL pattern decrease 28.50% (E>1.0MeV) and 28.22% (E>0.1MeV) compared with LSACL pattern and it is feasible expand the life of LWR-RPV to 60 years by LLCL pattern.
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