Thermal Analysis of a Spent Fuel Cask as if it Were Involved in a Realistic Transportation Accident that Resulted in a Severe Fire

The hypothetical thermal accident condition in 10CFR71.73 [1] requires the exposure of a Type B package to a 30-minute, fully engulfing fire. This thermal environment is intended to envelop the severity of the vast majority of possible real accidents. Radioactive material packages are required to withstand this hypothetical accident condition without releasing their contents. While the thermal insult to a package from this environment is well defined, real world accidents (actual or postulated) are difficult to quantify. A recent paper by Ammerman et al. [2] investigated a set of actual transportation accidents and compared them to the hypothetical accident conditions that spent fuel casks are designed to survive. The types of accidents that were investigated included a propane tanker truck explosion, a train derailment with subsequent hazardous material fire, and military munitions explosions. Another recent paper by Lopez et al. [3] looked at the heat transfer response of a thermally massive spent nuclear fuel (SNF) cask to some of these historic accidents and concluded that the fires studied would not have failed the cask had it been involved in such or similar types of accidents. This paper presents the results from calculations performed with the CAFE fire code to determine the heat transfer response of an SNF rail cask to a realistic accident scenario and four possible variations of this scenario. The most severe of all the cases studied was one where a pool fire was set next to the cask and wind blew the hot flames onto the cask. However, results showed that the robust nature of the SNF rail cask provided enough thermal resistance to withstand such fire and thus protect the environment from any release.