A person standing three feet from unshielded irradiated fuel would receive a lethal radiation dose in 10 seconds. Current cask fire standards do not reflect the possibility of a tanker fuel fire. A fire associated with a truck or rail accident increases the probability that radioactivity will be released. But rail fires could burn for hours, sometimes for days, at temperatures considerably higher. Diesel fuel burns at 1850 Fahrenheit.
Some materials burn twice as hot.
The heat could vaporize some radioactive materials and sweep them up into the air. Persons downwind could inhale radioactive particulates and later develop cancer or genetic effects. New cask designs are more than twice as large as any cask used before, and they will be tested only by computer models, not under actual accident conditions. Shipping containers are designed to withstand a crash into an immovable object at 30 miles per hour. Obviously Interstate trucks travel much faster than 30 m.p.h.