Biasing techniques for gamma rays going around efficient shields

This paper describes a method based on a combination of the exponential transformation, the angular biasing and the region of imposed collision. This combination can be employed in Multigroup Monte Carlo radiation transport calculations particularly in deep penetration problems for complex geometry. To test the effectiveness of this method, we have applied it to a practical case concerning the evaluation of gamma rays, which skirt a region of perfect shield within a graphite medium and contribute to a finite detector, place behind the perfect shield. An isotropic punctual and mono-energetic gamma source is placed at the other side of the shield. The current obtained for our multigroup Monte Carlo program agrees with MCNP4B code with a high figure of Merit. The gamma ray cross section used was collapsed to 75 groups from ENDF/B-VI library. (author)