VALIDATION OF THE SCALE 4.4A SOURCE TERM AND SHIELDING SOFTWARE BASED ON MEASUREMENTS AT A CASTOR IIA CASK

In Germany, the Federal Office for Radiation Protection (BfS) as the competent authority for package design approval has to evaluate whether a new package design meets all applicable dose rate limits of the transport regulations. For demonstration by calculation the SCALE code system (SCALE = Standardized Computer Analyses for Licensing Evaluation) developed by Oak Ridge National Laboratory (ORNL) is used. This paper presents the validation of the SCALE 4.4a source term and shielding software for use with spent fuel transportation casks of the CASTOR family by comparing model calculations with measurements in the neutron and gamma field caused by a CASTOR IIa cask. The measurements were carried out in 1995 at various distances above the lid and in the cask midplane and have been presented partly at PATRAM 1998 [1]. For the calculations the SAS4 sequence of SCALE 4.4a has been used. The fuel elements as well as the basket and the cask body have been modelled in detail by MARS geometry. To cover all detector locations, the model is based on the upper half of the cask. The source description has been taken from SAS2 calculations. Results have been obtained for different fluence-to-dose conversion factors.