Senior Project Manager
The NAC LWT transport package Photo courtesy of NAC International
In September 2013, we talked about transportation of spent nuclear fuel and how we know it is safe. This month, we want to discuss the safety basis for transporting other types of radioactive material.
The NRC recently approved a package to transport high enriched uranyl nitrate. This material is left over from the production of medical isotopes used in millions of diagnostic procedures every year. This package is to be used to bring material currently stored in Canada, where the isotopes were made, to the Savannah River site in South Carolina. The shipments are part of a DOE program to take back high enriched uranium from countries to which the U.S. supplied it.
Our review did not address whether the shipment should be made. Nor is it specific to any route. It just looked at whether the proposed shipping package design meets our requirements for safe transport. We rigorously reviewed the information submitted by the cask designer, NAC International. We asked four sets of detailed questions and thoroughly reviewed the applicant’s responses. After two years of review and two face-to-face meetings, we have answers to all our questions and we’re satisfied that the package design meets all NRC requirements for safe transport.
The high enriched uranyl nitrate, which is a liquid, will be transported using special containers that were designed to prevent leakage. To ensure they do not leak, the containers are leak tested after fabrication and prior to transport, each time the container is filled. These containers must also be replaced once they have been in use for 15 months. Together, these requirements give the NRC confidence that the containers will not leak.
These leak-tight containers will be placed into specially-designed packages for transport. This package design has been used for 25 years to safely transport a wide variety of radioactive materials. The inner containers and the outer packaging together make up the transport package.
Our review of this transport package design gives us confidence that, even if there were to be a transport accident, radioactive material will not leak from the package; dose rates will not be high enough to cause harm to anyone; and a nuclear chain reaction will not occur. Packages are evaluated for conditions that mirror normal transportation as well as the forces the package may experience in a severe accident.
The conditions assessed for routine transport include rain, hot and cold temperatures, a drop that may occur during handling, and the vibration that we all feel in a car or riding on a train.
For accident conditions, the package must be shown to be able to withstand forces that are more severe than in a real-world accident. This is done by testing or evaluating the package in a sequence of stringent tests. We discussed these tests in detail in our September 2013 blog.
This package has been shown to be able to safely transport contents that are much heavier and more radioactive than the high enriched uranyl nitrate, including spent nuclear fuel. The dose rates from the package containing liquid uranyl nitrate will be much lower than when the package is loaded with spent fuel.
For all these reasons, the NRC Is confident the package design meets all our requirements for safe transport. We follow the same review process for every transport package design we receive. In every case, we make sure we thoroughly understand the design and all the analyses in the application. We ask questions, if necessary, and often perform our own analysis. In some cases, including this one, we impose special conditions to give added assurance of safety. Only when we are satisfied a design meets every NRC requirement will we issue an approval.