At the end of this year, the last three German nuclear reactors – Isar 2, Emsland and Neckarwestheim 2 – will be taken off the grid and the era of nuclear power generation in Germany will end. Some other countries, on the other hand, are sticking to nuclear power plants. And research on new reactor types is also showing lively international dynamics with a few dozen different concepts.
Smaller reactors with an electrical output of up to 300 megawatts in particular – small modular reactors (SMR) – are being worked on in mostly very early development phases. You strive for safe operation at the lowest possible cost. However, according to a new analysis, the problem of nuclear waste disposal, which is still unsolved worldwide, could even increase with these modular small reactors compared to the light water reactors in operation today.
Small Reactors vs. Conventional Light Water Reactor
“SMRs will exacerbate the challenges of nuclear waste management and disposal,” report Lindsay M. Krall of the Swedish Nuclear Fuel and Waste Management Company in Solna and her colleagues at Stanford University’s Center for International Security and Cooperation. In their analysis, the researchers focus on three different reactor types – an integrated pressurized water reactor, a sodium-cooled fast breeder reactor and a molten salt reactor.
On the basis of available patents and scientific publications, they determined the amounts of radioactive waste generated in relation to heat generation. This heat forms the basis for the actual generation of electricity via generators. They then compared their results with the waste quantities of a conventional light water reactor with an electrical output of 1100 megawatts.
In the operation of nuclear reactors, fast neutrons keep the necessary chain reaction going. At the same time, however, they must also be shielded from the environment. According to the researchers, the cost of this shielding increases with smaller nuclear reactors. At the same time, the amount of radioactive waste is also growing. An integrated pressurized water reactor causes two and a half times the amount of waste compared to current, large nuclear power plants. The examined concept for a molten salt reactor even resulted in a fivefold increase.
And with a small fast breeder reactor, 30 times the amount of waste must be expected, since relatively large amounts of the coolant sodium are used here. In addition, more radioactive isotopes are concentrated in the spent fuel than in large light water reactors. This requires more effort in transport and safe interim storage of the nuclear waste.
Further analyzes for further reactor types
With only three types of small nuclear reactors examined so far, this study provides initial indications of the amounts of nuclear waste to be expected. In order to be able to evaluate all types under development, further analyzes would have to follow. However, Lindsay and colleagues point to many similarities in power plant design, fuel cycle and neutron leak rate of many SMRs. “Therefore, most SMRs show a significant disadvantage for the disposal of nuclear waste,” say the researchers.
Despite this setback, work on new, smaller reactor types will continue with great certainty. However, most approaches have not yet progressed beyond a draft phase on paper. The first prototypes can therefore hardly be expected before the 2030s. Whether SMRs could still make a significant contribution to completely climate-neutral power generation by the middle of the century should be critically questioned before major investments are made in these technologies. It also remains questionable whether the partly optimistic announcements of lower electricity production costs of 2 to 3 cents per kilowatt hour will be kept. Solar power plants in sunny locations are already reaching this price level today.
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