Shielding Analysis of the Model 9602 Type B Packaging Design for Disused Radiological Sources

A new compact Type B transportation packaging, designated as Model 9602, is being designed by Argonne National Laboratory researchers for storage, transport and disposal of disused radiological sources. This paper describes the shielding analysis of the Model 9602 packaging design performed as part of the preparation of a Safety Analysis Report for Packaging, which is to be submitted to the regulatory authority as part of an application for a Certificate of Compliance for the packaging design. The shielding performance of Model 9602 under normal conditions of transport and hypothetical accidents, described in Title 10 of the U.S. Code of Federal Regulations (10 CFR 71), Packaging and Transportation of Radioactive Material, was evaluated by using the Oak Ridge Isotope Generation code for the source terms and the Monte Carlo N-Particle Transport Code (MCNP), version 6.2, for calculating the gamma dose rates based on the ANSI/ANS-6.1.1-1977 dose conversion factors. The 10 CFR 71 regulatory limits on dose rates at the external package surfaces (top/side/bottom) for the Model 9602 packaging design are 2 mSv/h (0.2 rem/h) and 10 mSv/h (1 rem/h), respectively, for non-exclusive and exclusive-use shipment. The results obtained from the MCNP shielding analyses showed that the calculated radiation dose rates satisfy the 10 CFR 71 requirements for transporting disused CsCl sealed capsules in Model 9602 off-site by exclusive-use shipment for direct disposal. For interim storage on-site or off-site after transport, the radiation dose rates at the external package surface of Model 9602 will decrease over time because of the continuing isotope decay. Moreover, the all-stainless-steel packaging design of Model 9602 provides excellent performance with respect to general corrosion resistance during long-term storage, thus enabling subsequent transportation, without repackaging of the disused radiological sources, to a geological repository or deep borehole for final disposal.