Small nuclear reactors, should they become a major contributor to electricity production, will add to the problem of what to do about nuclear waste. According to a new study, scheduled to be published in the Proceedings of the National Academy of Science’s May 31 issue, SMRs will produce from twice to 30 times as much nuclear waste as conventional large reactors.
First highlighted in a Stanford University press release, the report is based on analytical work going back several years. It undercuts some of the claims of advocates of SMRs and casts doubts on cost estimates of the still untried advanced nuclear technology.
Lead author Lindsay Krall, a former MacArthur fellow post doc at Stanford’s Center for International Security and Cooperation, said, “Our results show that most small modular reactor designs will actually increase the volume of nuclear waste in need of management and disposal, by factors of 2 to 30 for the reactors in our case study. These findings stand in sharp contrast to the cost and waste reduction benefits that advocates have claimed for advanced nuclear technologies.”
Krall detailed the results of her research in a Chemistry World interview. The conventional way of looking at spent fuel is simply mass. But that’s misleading, says Krall. “We need to know a lot more about the material, we need to know how much decay heat is being emitted. What is the radionuclide composition of the waste? What is the chemical matrix that those radionuclides are bound in? How much low and intermediate-level waste is being produced? And this is especially important: what is the concentration of fissile nuclides in the spent fuel?”
Because the SMR reactor core will be smaller than in current commercial reactors, the result for the SMRs will be “neutron leakage,” she says. The way to manage this is to add graphite or steel reflectors. The reflectors absorb neutrons and become radioactive, meaning more low and intermediate nuclear wastes, says Krall. “And that waste needs to go to a geologic repository as it consists of a long-lived nuclide, as well as short lived nuclides that can complicate decommissioning of a reactor.”
Another SMR complication: the smaller reactors, Krall says, likely will need fuel that is more highly enriched than conventional uranium fuel. “Ultimately, the combination of the higher enrichment and lower burn up leaves you with a higher concentration of fissile radionuclides in your spent fuel. And that’s something that I think is going to be very expensive to deal with once you get into the design of a spent fuel management system, because you need to put these spent fuels in canisters – and the canisters can be expensive because they’re supposed to last at least 10,000 years.”
Krall is now a scientist at the Swedish Nuclear Fuel and Waste Management Company. Co-authors of the study are Rodney Ewing, the Frank Stanton Professor in Nuclear Security at Stanford and co-director of CISAC, and Allison Macfarlane, professor and director of the School of Public Policy and Global Affairs at the University of British Columbia and former chairman of the U.S. Nuclear Regulatory Commission, where she took a particular interest in waste management.
In a tweet, Paul Dorfman, who chairs the Nuclear Consulting Group and is a member of the Sussex Energy Group at the University of Sussex, UK, commented, “This is important … very significant practical and policy implications.”
–Kennedy Maize
Twitter (kennedymaize)