Finite Element Thermal Analysis of a P-48 UF6 Overpack to Support Transport Re-certification

This paper provides an overview of the thermal evaluation performed as part of the safety analysis validation of the P-48 overpack Certificate of Compliance to support various projects requiring transport of 48-inch diameter UF6 cylinders. The P-48 is an insulated transport overpack designed to protect various types of UF6 cylinders previously deployed at the Portsmouth and Paducah former enrichment facilities in the U.S. Revalidation of the P-48 certificate required supportive safety analysis including a detailed thermal evaluation to meet existing transport regulations. In particular, a detailed finite element thermal analysis (FEA) of the P-48 package is performed to confirm these overpacks, when loaded with UF6 cylinders, meets the requirements of U.S. 49 CFR 173.420 (3) (iii). The controlling thermal condition in these requirements is the fire accident condition defined in U.S. 10 CFR 71.73 (c) (4). A description of the three dimensional detailed thermal FEA model and the application of the initial conditions are covered. The package internal structure is also evaluated for the additional heat generation produced during the fire condition. Due to the large thermal mass of the package and the limited conductivity of the insulation and internal structure, maximum cylinder temperatures are achieved at a time significantly beyond the end of the fire condition. Sensitivity studies are included to confirm the stability of the thermal transient solution. The evaluation demonstrates that the maximum temperature of the UF6 cylinder is achieved and the stability of the package and its confinement barrier is maintained.