Analysis of Spent Fuel Transportation Cask Response to a Tunnel Fire Exposure

The U.S. Nuclear Regulatory Commission’s Spent Fuel Project Office is responsible for enforcing regulations that ensure that transportation of radioactive materials within the United States is conducted in a safe manner. Included in this responsibility is the assessment of the impacts of transportation events on radioactive material shipments, including the shipment of spent nuclear fuel. On July 18, 2001, a freight train carrying hazardous (non-nuclear) materials derailed and caught fire in the Howard Street tunnel in Baltimore, Maryland. The staff of the Spent Fuel Project Office (SFPO) was tasked with assessing the consequences of this event on the transportation of spent nuclear fuel. This paper details the staff’s actions related to the investigation and analysis of the Baltimore tunnel fire event. This paper describes the staff’s coordination with the National Transportation Safety Board (NTSB) to determine the details of the train derailment and fire, and includes details of the staff’s technical analysis, which was completed with assistance from the National Institute of Standards and Technology (NIST), Pacific Northwest National Laboratory (PNNL), and the Center for Nuclear Waste Regulatory Analysis (CNWRA). A fire model of the Howard Street tunnel fire was created by NIST, based on details of the fire event provided by NTSB. The CNWRA provided analyses of materials removed from the tunnel after the fire to confirm the temperature results of the NIST fire model. SFPO staff, with the assistance of PNNL, created a finite element model of a spent fuel transportation cask, and applied boundary conditions derived from temperature and flow results of the NIST fire model to analyze the spent fuel cask under the Howard Street tunnel fire conditions. This work provides a demonstration of the robust design of a rail cask used to ship spent nuclear fuel. This paper presents the results of the staff’s analysis and the staff’s conclusions on the ramifications of the Baltimore tunnel fire event on the transportation of spent nuclear fuel.