On the other hand, some other reactor designs can produce smaller amounts of spent fuel, but this is not necessarily a minor problem. For example, fast reactors burn more by consuming more fissile material and extracting more energy from their fuel. This means that the fuel from these reactors usually has a higher concentration of fission products and emits more heat. And that heat can be a lethal factor in designing waste solutions.
Spent fuel must be kept relatively cool, so that it does not melt and release dangerous byproducts. Too much heat in the reservoir can also damage the surrounding rock. “Heat really determines how much you can put inside the reserves,” says Paul Dickman, a former Energy Department and NRC official.
Some spent fuel may require chemical processing before disposal, says Alison MacFarlane, director of the School of Public Policy and Global Affairs at the University of British Columbia and former chair of the NRC. This may increase complexity and cost.
For example, in fast reactors cooled by sodium metal, coolant can enter the fuel and fuse into its casing. Separation can be difficult, and sodium is highly reactive with water, so the spent fuel will require special treatment.
TerraPower’s Natrium reactor, a sodium fast reactor that received a construction permit from the NRC in early March, is designed to safely manage this challenge, says Jeffrey Miller, TerraPower’s senior vice president of business development. The company plans to remove the sodium and blow out nitrogen before dumping the material into a wet storage pool.
location, location, location
Regardless of what materials are used, even changing the size of reactors and where they are located can create complications for waste management.
Some new reactors are essentially smaller versions of the larger reactors in use today. These small modular reactors and microreactors can generate waste that can be handled in the same way as waste from today’s conventional reactors. But for places like the US, where waste is stored onsite, it would be impractical to have lots of small sites, each storing its own waste.
Some companies are considering sending their microreactors and the waste material they produce to a single location, possibly to the same location where the reactors are built.
UBC’s MacFarlane says companies should be required to think carefully about waste and design in management protocols, and they should be held accountable for the waste they produce.
She also notes that until now, waste planning has depended on research and modeling, and the reality will only become clear once the reactor is actually operational. As she says: “These reactors don’t exist yet, so we don’t really know in too much detail about the waste they produce.”
