Variance Reduction Techniques Using Adjoint Monte Carlo Method in Shielding Problem

The event value Wg ([rbar], Ω) has been derived in a form which can be obtained directly from existing adjoint Monte Carlo computer codes. It is demonstrated that the event value and the point value functions obtained from the adjoint Monte Carlo calculation can be used as the path-length biasing and the angular biasing in the forward Monte Carlo calculation, respectively. The iterative forward-adjoint Monte Carlo method using the source biasings is employed to reduce the standard deviation in the shielding problem. In addition, the effectiveness of the source biasing schemes is investigated in the same problem. The results indicate a significant reduction in the standard deviation and a substantial improvement in the efficiency of the Monte Carlo shielding calculations.