Parametric study of shielding codes used for packaging

It is very important to be able to predict the dose rates external to a flask package. Currently in Japan several shielding calculation codes are used to evaluate the dose rate around a package. It is, however, generally appreciated that there are differences between results obtained when using different calculation codes for the same shielding calculation problems. The differences appear to be particularly important for gamma ray shielding calculations when using the point-kernel method on a package with a multi-layer wall because of the build-up factor. In this paper the calculation accuracy of some codes for gamma ray shielding calculations using the codes QAD and MARMER (a point-kernel method), the ANISN code (discrete ordinate (Sn) method) and the MCNP code (a Monte Carlo method) are examined and compared using the benchmark problems. The calculation results are then compared with the results from a simulated actual flask package body wall. The results presented here show that the calculation results using MARNER and MCNP (which have recently been introduced into Japan) agree with the experimental measurements. These codes can therefore be used for future gamma shielding calculations and the calculation conditions of those codes in Japan. (author)