TECHNIQUE TO CALCULATE SURFACE DOSE-RATE PROFILES BY MONTE-CARLO METHOD

A technique for Monte Carlo codes to obtain surface dose rate profiles of cask surfaces within a reasonable CPU time is presented in this pa per. This technique does not use a huge number of actual small detecto rs defined by additional geometry input data, but uses imaginary detec tors. To demonstrate this technique, SAS4 in the SCALE code system is chosen. The estimator is a surface crossing estimator (SXE). The techn ique is very simple and easy. In the Monte Carlo calculation, the cont ribution to the dose by a particle across the surface estimator is sto red separately according to the coordinate of the surface crossing poi nt of the particle as if there were a series of small surface estimato rs. After the Monte Carlo calculation has been done, the post processi ng procedure is made to produce dose rate profiles at the cask surface using the data from a series of small surface estimators. The additio nal CPU time required for introducing the new technique to the origina l CPU time is very small. The proposed technique using SXE is confirme d to be a very efficient and cost-saving method for getting dose rate profiles around a cask.