Scattering direction biasing for Monte Carlo transport calculation

There is no straightforward way to calculate neutron transport of a system by Monte Carlo having complicated structures like a penetration in a shield wall. The reason is that the transport code never knows an appropriate route for neutrons to go through a shield wall beforehand. In the present study, estimating the contribution distribution to the detector during the transport calculation and the scattering direction biasing is simultaneously applied with the distribution, so that the neutron is guided to the detector efficiently. Test calculations with the proposed biasing procedure were carried out with some simple models, and the basic performance of the procedure was confirmed. The present procedure can be a strong biasing tool to be utilized for calculations of thick and complicated structures like streaming, shyshine and so on.