Jeremy L. Dillon
RW Monitor
2/21/2014

A Nuclear Regulatory Commission risk assessment report has found that the transportation of spent nuclear fuel would cause low radiological impact to the environment or public, even in the case of an accident. The report, commissioned by the NRC to analyze the effects advancements in transportation technology have had on shipment risks, concluded that “if there were an accident during a spent fuel shipment, there is only a one-in-a-billion chance that the accident would result in a release of radioactive material.” The NRC analyzed shipping containers and routes to understand the impact radiation would have on the public traveling near the containers, workers handling the shipment casks, and the public’s homes that line the shipping routes. “Based on these findings, this study reconfirms that radiological impacts from spent fuel transportation conducted in compliance with NRC regulations are low,” the report said. “In fact, they are generally less than previous, already low, estimates. Accordingly, this study also reconfirms the NRC’s previous conclusion that regulations for transportation of radioactive material are adequate to protect the public against unreasonable risk.”

The report looked at the current NRC-certified casks and how they behave in routine transportation and in transportation accidents. Two of the three cask designs, including one with steel gamma shielding and an inner welded canister for the spent fuel and one with lead gamma shielding that can transport spent fuel within an inner welded canister, are meant for train transportation, while the third cask design with depleted uranium gamma shielding is meant for highway transportation. The NRC concluded that during normal shipment “the dose of radiation to members of the public during routine transportation is a small fraction of the naturally occurring background radiation that individuals experience.” The report characterized the threat level in this situation as small.

In cases where the cask shipments may suffer an accident, the NRC concluded that only in “severe” accidents would the public be at risk to radiation leaks. “Radioactive material would not be released in an accident if the fuel is contained in an inner welded canister inside the cask,” the report said. “Only rail casks without inner welded canisters would release radioactive material, and only then in exceptionally severe accidents.” In cases of fire, the report determined the casks’ risk of gamma shielding loss was negligible while none of the fire accidents resulted in the release of radioactive material. The study used current truck and rail accident statistics to determine the probability of an accident and the severity of that accident, the report said.