Monte Carlo Method In The Monochromator Shielding Body Design

Radiation protection is very important during the construction of experimental establishment. The designed shield should assure the radiate dose below vocational annual dose equivalent limit (20 mSv/y); meanwhile, it'd better take less space in order to place experiment facilities. The material of shield is concrete with much iron powder, and an inappropriate designing will increase the cost. Here the Monte Carlo method was used to the shield designing of monochromator in CARR in CIAE (China Institute of Atom Energy). The neutron andγray leakage and dose equivalent rate in four different models were calculated using MCNP software package. During the calculation, the geometry is simplified and the calculating efficiency is improved by using a reflecting surface. The shield is so thick that the result has an large relative-error if using analog simulation. Geometry splitting with Russian roulette is used to reduce variance. Good result was obtained with an acceptable relative error. According to the calculated result above, the shielding effect is predicted .It help to decide whether to add other shielding or not when the revolving door is closed, and the geometry and thickness of monochromator shield can be adjusted to optimize thestructure.