New study: small nuclear reactors will generate more waste

Small modular reactors (SMRs), long touted as the future of nuclear energy, will actually generate more radioactive waste than conventional nuclear power plants, according to new research from Stanford University and the University of British Columbia. 

Experts have claimed that these advanced modular designs will be cheaper and produce fewer radioactive by-products than conventional large-scale reactors.

However, a 30 May paper in Proceedings of the National Academy of Sciences has reached the opposite conclusion.

“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,” said study lead author Lindsay Krall, a former MacArthur postdoctoral fellow at Stanford University’s Center for International Security and Cooperation.

For this study, Krall analysed the nuclear waste streams from three types of small modular reactors being developed by Toshiba, NuScale, and Terrestrial Energy. Each company uses a different design. 

The study found that, because of their smaller size, small modular reactors will experience more neutron leakage than conventional reactors. This increased leakage affects the amount and composition of their waste streams.

The study also found that the spent nuclear fuel from small modular reactors will be discharged in greater volumes per unit energy extracted and can be far more complex than the spent fuel discharged from existing power plants.

“Some small modular reactor designs call for chemically exotic fuels and coolants that can produce difficult-to-manage wastes for disposal,” said co-author Allison Macfarlane, professor and director of the School of Public Policy and Global Affairs at the University of British Columbia. “Those exotic fuels and coolants may require costly chemical treatment prior to disposal.”

“The takeaway message for the industry and investors is that the back end of the fuel cycle may include hidden costs that must be addressed,” Macfarlane said. “It’s in the best interest of the reactor designer and the regulator to understand the waste implications of these reactors.”

The study concluded that, overall, small modular designs are inferior to conventional reactors with respect to radioactive waste generation, management requirements, and disposal options.

One problem, it suggests, is long-term radiation from spent nuclear fuel. The research team estimated that after 10,000 years, the radiotoxicity of plutonium in spent fuels discharged from the three study modules would be at least 50 percent higher than the plutonium in conventional spent fuel per unit energy extracted.

Because of this high level of radiotoxicity, geologic repositories for small modular reactor wastes should be carefully chosen through a thorough siting process, the authors said. 

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