Combination of four biasing techniques for gamma ray shielding calculations

Abstract

To enhance the efficiency the of Monte Carlo method for particles in deep penetration problems for complex geometry, we have used a method based on a combination of four techniques: the exponential transformation, the angular biasing, the imposed collision and the weight window. These four techniques allowed us to increase the probability of particles to scatter toward a finite detector. To test the effectiveness of this method we have applied it to a practical problem. We are interested in the evaluation of the gamma ray which can skirt a lead (Pb) shield within a graphite medium and contribute to a finite detector, placed behind this presupposed perfect shield. A punctual, isotropic and mono-energetic gamma source is placed at the other side of the shield. In order to qualify this method we have used the TRIPOLI-03 and MCNP-4B codes. The current obtained from our multi-group Monte Carlo program agrees with both codes for different locations of the detector with high Figure of Merit ( FOM = 1 σ 2T ). The used gamma ray cross-sections were collapsed to 75 groups from the ENDF/B-VI library. This method has also been used successfully to calculate the gamma ray spectra for different locations of the detector.