COG11.1 Code Features for Shielding and Criticality Safety Analyses

The performance of a shipping package in satisfying the regulatory requirements of the Code of Federal Regulations (CFR) is normally documented in the Safety Analysis Report for Packaging (SARP). In Chapter 5, shielding evaluations for Normal Conditions of Transport (NCT) and Hypothetical Accident Conditions (HAC) are documented to meet 10 CFR 71 requirements. In Chapter 6, nuclear criticality safety evaluations for NCT and HAC are documented to show that the package is subcritical. The COG code developed by LLNL, is a Monte Carlo radiation transportation code, which has been heavily used in the areas of radiation detection and nuclear criticality safety. Unique features of COG include specifications for rotational surfaces, use of the perspective 3-D graphics, input of multiple cross section libraries, and repeated structure modeling capability. Furthermore, the time dependent gamma ray source term can be automatically generated for direct radiation dose calculations. This paper presents some of these COG code features for solving shielding and criticality safety problems for the 9975 shipping container. Comparison of COG results against SARP and MCNP results indicates that COG can be a powerful tool for preparation of the Chapters 5 and 6. COG is distributed through the Radiation Safety Information Computational Center (RSICC) of ORNL.