This is assured either by limiting the amount of spent fuel shipped or by controlling the spent fuel configuration during the shipment and using neutron poisons such as boron in the structural materials of the cask. For more than 40 years, spent fuel has been safely carried by truck and rail in the United States and abroad, although countries involved in reprocessing obviously transport more. Every year, about 1,000 metric tons of LWR spent fuel move from French and foreign utilities to La Hague reprocessing plant. Air and sea shipments of non-U.S. obligated and foreign fuel have been made for years. Also, in a joint venture, Britain and France operate a small fleet of purpose-built ships designed to transport spent fuel from overseas reactors.
Special features minimize damage in case of collision.