Every year, an estimated two thousand six hundred tons of spent nuclear fuel is generated by nuclear power reactors in the U.S. Roughly fifty thousand tons of spent nuclear fuel are currently stored in cooling pools at reactor sites around the U.S. Many cooling pools are reaching their limit. Another fifteen thousand tons of spent nuclear fuel is currently stored in dry casks onsite and at interim storage facilities. Without a permanent geological repository for spent nuclear fuel in the U.S., a great deal more of the spent nuclear fuel in the cooling pools will have to be moved to dry cask storage. While some of these casks will be stored onsite, many more will be moved to interim facilities. This will require the transport of thousands of metric tons of spent nuclear fuel from reactor sites to interim storage facilities.
Sandia National Laboratories recently completed with they are calling a nuclear “triathlon” to improve the safety of spent nuclear fuel transport. This exercise consisted of moving a simulated cargo of spent nuclear fuel rods over fourteen thousand miles. The purpose of the “triathlon” was to monitor the stresses and jolts that such a fuel experiences while being transported. Transportation of spent nuclear fuel involves packaging the fuel rods with strict adherence to regulations of the International Atomic Energy Agency (IAEA). In addition to regulatory satisfaction, the public must be confident that every precaution has been taken in transporting spent nuclear fuel.
For over thirty years, spent nuclear fuel has been stored in what are referred to as Type B casks. Each of these casks weights about one hundred and twenty-five tons. Each can carry twenty-four tons of spent nuclear fuel. The spent nuclear fuel is in the form of rectangular bundles (called assemblies) of long, thin zirconium rods. The rods contain pellets of either enriched uranium or plutonium. The casks are forged from solid steel and have steel hatches with gaskets. The special reinforced pins that attach the hatches can survive one hundred tons of force. When the casks are loaded and sealed, they are so strong that they could survive the impact of a one-thousand-ton diesel locomotive going one hundred miles an hour.
The fuel rods themselves are very fragile. After being in a hot, high radiation environment for a few years, the zirconium shells, called cladding, are very brittle. If extreme care is not use when handling the fuel rod assemblies, they may shatter.
SNL partnered with Spanish and South Korean partners. They also worked with Pacific Northwest and Argonne national laboratories. A new dry cask was loaded with three dummy fuel rod assemblies. The rods were made of lead and contained lead pellets. The casks are designed to carry up to thirty-two complete fuel rod assemblies but the test cast only had three fuel rod assemblies. Additional space was take up by accelerometers and strain gauges to measure everything that each of the fuel rod assemblies experienced during their trip. A custom monitoring system tracked shocks and vibrations that the cask and the fuel rod assemblies were subjected to during the trip.
SNL has conducted other tests in the past including simulating the transport of fuel rod assemblies over city streets and rough roads. They also simulated a journey by rail of fuel rod assemblies.
The new test or triathlon used a Spanish dry cask which traveled by heavy truck over highways in Spain two hundred and fifty miles to a seaport. The cask was then transferred to a barge where it traveled a thousand miles along the coast to Belgium. Next it was placed on a cargo ship and spent two weeks traveling four thousand miles to Baltimore in the U.S. After arriving in the U.S., the cask was put on flatbed railway car. It then traveled over two thousand miles through twelve states before it arrived in at the Transportation Technology Center Inc facility near Pueblo, Colorado. At the Center, the cask engaged in some experiments on a fifty-mile test track. Finally, the cask reversed its route back to Spain. Over eight terabytes of data were acquired which will require at least a year to analyze.
