Part 2 of 2 Parts (Please read Part 1 first)
     Dozens of SMR designs have been proposed. For this study, Krall analyzed the nuclear waste streams generated by three types of SMRs being developed by Toshiba, NuScale, and Terrestrial Energy. Each company chose a different design. Results from these case studies were corroborated by theoretical calculations and a broader design survey. This three-pronged approach allowed the authors to draw powerful conclusions.
     Rodney Ewing is the Frank Stanton Professor in Nuclear Security at Stanford and co-director of Stanford University’s Center for International Security and Cooperation (CISAC). CISAC is part of the Freeman Spogli Institute for International Studies at Stanford. Ewing is also a professor in the Department of Geological Sciences in the Stanford School of Earth, Energy and Environmental Sciences and a co-author of the Stanford study. He said, “The analysis was difficult because none of these reactors are in operation yet. Also, the designs of some of the reactors are proprietary, adding additional hurdles to the research.”
     Energy is produced in a nuclear reactor when a neutron splits a uranium atom in the reactor core. This generates additional neutrons that go on to split other uranium atoms, creating a chain reaction. However, some neutrons escape from the core which is called neutron leakage. The escaping neutrons strike surrounding structural materials, such as steel and concrete. These materials become radioactive when impacted by neutrons lost from the core.
     The new study found that SMRs will experience more neutron leakage than conventional reactors because of their smaller size. This increased leakage has an impact on the amount and composition of their waste streams.
     Ewing said, “The more neutrons that are leaked, the greater the amount of radioactivity created by the activation process of neutrons. We found that small modular reactors will generate at least nine times more neutron-activated steel than conventional power plants. These radioactive materials have to be carefully managed prior to disposal, which will be expensive.”
     The Stanford study also found that the spent nuclear fuel from SMRs will be discharged in greater volumes per unit energy extracted. The SMR waste can be far more complex than the spent nuclear fuel discharged from existing power plants.
     Allison Macfarlane is a professor and director of the School of Public Policy and Global Affairs at the University of British Columbia and a co-author of the study. She said, “Some small modular reactor designs call for chemically exotic fuels and coolants that can produce difficult-to-manage wastes for disposal. Those exotic fuels and coolants may require costly chemical treatment prior to disposal. The takeaway message for the nuclear industry and investors is that the back end of the fuel cycle may include hidden costs that must be addressed. It’s in the best interest of the reactor designer and the regulator to understand the waste implications of these reactors.”
     The Stanford study concludes that SMR designs are inferior to conventional nuclear power reactors with respect to radioactive waste generation, management requirements, and disposal options.
    One major problem is long-term radiation from spent nuclear fuel. The research team estimated that after ten thousand years, the radiotoxicity of plutonium in spent nuclear fuels discharged from the three study modules would be at least fifty percent higher than the plutonium in conventional spent nuclear fuel per unit energy extracted. Because of this high level of radiotoxicity, geologic repositories for SMR wastes need to be carefully chosen through a thorough siting process, the authors said.
     Ewing said, “We shouldn’t be the ones doing this kind of study. The vendors, those who are proposing and receiving federal support to develop advanced reactors, should be concerned about the waste and conducting research that can be reviewed in the open literature.”

Part 1 of 2 Parts
     Small modular reactors (SMR) have long been touted as the future of nuclear energy. However, they will actually generate more radioactive waste than conventional nuclear power plants. This was found during research at Stanford and the University of British Columbia.
     Nuclear reactors generate electricity with limited greenhouse gas emissions. A nuclear power plant that generates one gigawatt of electricity also produces radioactive waste that must be isolated from the environment for hundreds of thousands of years. In addition, the cost of constructing a large nuclear power plant can be tens of billions of dollars.
     To address these challenges, the nuclear industry is developing SMRs that generate less than three hundred megawatts of electric power. SMRs are about one tenth to one quarter the size of a traditional nuclear energy plant due to compact, simplified designs.  They can be assembled in factories. Industry analysts say that these advanced modular designs will be cheaper and produce less radioactive waste than conventional large-scale reactors. However, a study published on May 31 of this year in Proceedings of the National Academy of Sciences has reached the opposite conclusion.

    Lindsay Krall is a scientist at the Swedish Nuclear Fuel and Waste Management Company and lead author of the study. She 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.”
     About four hundred and forty commercial nuclear reactors currently operate globally. They provide approximately ten percent of the world’s electricity. In the U.S., ninety-three nuclear reactors generate about a fifth of the country’s electricity supply.
     Unlike power plants that run on coal or natural gas, nuclear plants emit little carbon dioxide which is a major cause of global warming. Nuclear advocates say that as global demand for clean energy increases, more nuclear power will be needed to minimize the effects of climate change.
     However, nuclear energy is not risk free. In the U.S., commercial nuclear power plants have produced more than eighty-eight metric tons of spent nuclear fuel, as well as substantial volumes of intermediate and low-level radioactive waste. The most highly radioactive waste is mainly spent fuel. It will have to be isolated in deep-mined geologic repositories for hundreds of thousands of years. Currently, the U.S. has no program to develop a geologic repository, after spending decades and billions of dollars on the Yucca Mountain site in Nevada. Spent nuclear fuel is currently stored in pools or in dry casks at reactor sites. It is accumulating at a rate of about 2,000 metric tons per year.
     Some nuclear analysts claim that SMRs will significantly reduce the mass of spent nuclear fuel generated compared to much larger, conventional nuclear reactors. Other analysts say that conclusion is overly optimistic, including Krall and her colleagues.
     Krall said, “Simple metrics, such as estimates of the mass of spent fuel, offer little insight into the resources that will be required to store, package, and dispose of the spent fuel and other radioactive. In fact, remarkably few studies have analyzed the management and disposal of nuclear waste streams from SMR.”
Please read Part 2 next