Transportation casks for shipping used nuclear fuel are robustly designed to protect the public from releases of radioactive material in the unlikely event of an accident. The NRC regulates the design and construction of these casks by requiring that the candidate cask must demonstrate that it can survive four successive accident conditions involving free drop, puncture, fire and submersion in water events before it is considered fit for transportation. Casks, such as Holtec’s HI-STAR 190, HI-STAR 100 and HI-STAR 100MB are designed and fabricated with multiple layers of steel, lead and other materials to safely confine the fuel, shield workers and the public from radiation associated with the fuel. Inside the cask, the used nuclear fuel, in solid form, is confined inside a strength-welded canister, allowing no pathway for the radiological matter to escape to the environment. Hence multiple layers of protection stand between the cask’s contents and the environment. Fully loaded casks weigh 125 tons or more for rail shipments. Typically, for every ton of used fuel, a cask has about 4 tons of robust shielding material.
