Optimization design with Monte Carlo code for shield of residual stress neutron diffractometer

The shielding is a key way to lower the measuring background and keep workers safe for residual stress neutron diffractometer (RSND) building on reactor. The shield plan was optimized with Monte Carlo codes. In view of its complexity, two programs, McStas and MCNP5, were used, with some good techniques to improve the computation efficiency. The calculation of radiating field in RSND was accomplished with three parts: the transmission of thermal neutron in guide was simulated with McStas, the radiating leakage was estimated with MCNP due to slits between shield blocks, and the whole shield plan for RSND was modeled in MCNP. Corrected with influencing factors, the simulated results were compared with data measured by dosimeter, and it was found that they fitted well and was within the permitted error.