The 'mini' nuclear power plants will actually be super polluting

For the same amount of energy generated, small and modular nuclear power plants would produce a greater quantity and complexity of radioactive waste than traditional ones. The reason is in their low efficiency. To tell it on the pages of PNAS is a study by researchers from Stanford University and the University of British Columbia, who analyzed the so-called Small modular reactors (Smr), small modular reactors defined as "fourth generation" and proposed by their developers as a way cheaper and faster to produce nuclear energy.

As we told you, these are small reactors, capable of generating a power ranging from about 5 to 300 megawatts, and whose construction times and costs are much faster. To the detriment of the wording "fourth generation", which should mean an improvement in terms of efficiency and safety, and advertised as the future of nuclear energy, to date, however, there have been very few independent researches that have compared radioactive waste, that is the residues of nuclear fission, produced by Smr with those of traditional large-scale reactors.

In the new study, the researchers thus evaluated three different Smr technologies, not yet in operation and designed by Toshiba, NuScale Power and Terrestrial Energy, reviewing the data shared publicly with the US authorities by the companies. Comparing them to those of a conventional nuclear reactor, the researchers found that mini nuclear power plants could increase the volume of short-term decay waste up to 35 times compared to a conventional reactor, for long-term ones up to 30 times more. , and finally for spent nuclear fuel up to 5 times more. "SMRs performed worse on almost all of our parameters (such as radioactive decay heat and spent fuel radiochemistry) than standard reactors," says author Lindsay Krall. “Our results show that most SMR projects will actually increase the volume of nuclear waste that needs management and disposal. This is in stark contrast to the cost and waste reduction benefits advocates have claimed for their technologies. "

But why do SMRs produce higher volumes and greater waste complexity? Because, the researchers explain, they are naturally less efficient. The production of nuclear energy, in fact, involves a chain reaction, in which a single reaction in the reactor core generates neutrons that trigger one or more subsequent nuclear reactions. However, according to the research team, SMRs lose more neutrons from their nucleus (in a process that's called neutron scattering) than a larger reactor, meaning they can't keep the reaction self-sufficient for long. Even a small difference in neutron loss, therefore, results in a substantial impact on the composition of the waste. "We shouldn't be doing this kind of study," commented co-author Rodney Ewing. "The suppliers, those who are proposing and receiving funding for the development of these advanced reactors, should be concerned about the waste and conduct research that can be examined in the literature."

And companies' response to these results is not long in coming: as reported by the New Scientist, NuScale Power spokesperson Diane Hughes said the study is based on outdated information. "We disagree with the conclusion that the NuScale project creates more spent fuel used per unit of energy than currently operating reactors," she said. Rolls-Royce Smr, a UK-funded company to develop its own version of the technology (which was not considered in the study), also said it will present waste volume estimates in the UK's nuclear regulatory approval process. . The project, said the company spokesperson, "includes some technical innovations that reduce waste production".