SMRs, miniature reactors to better distribute the distribution of electricity?

While new EPRs should see the light of day in France by 2040 to replace aging reactors, Futura went to find out about other reactor technologies. On the program of this second article, recent small modular reactors which would make it possible to decarbonize energy in many countries: SMRs.

They were announced by President Emmanuel Macron in February 2022: between 6 and 14 EPR (European Pressurized Reactor Where Evolutionary Power Reactor) will be built by 2040, in order to maintain nuclear power as the main source of electricity in France. These reactors are based on the same principle as the reactors currently used: heat is created in the tank by nuclear reactions, then extracted by water kept liquid under high pressure. This water circulates in a closed loop in the primary circuit, itself in indirect contact with a secondary circuit. It cools on contact with this secondary circuit, by transmitting its heat to the water circulating there. The latter then vaporizes and spins a turbine which triggers an alternator: electricity is generated!

Reduce construction costs by producing modular reactors

Other types of reactors are beginning to emerge, or are coming back into fashion. Thus, fast neutron reactors could well come back into the debate in a few years. And other reactors, much smaller, are appearing: the SMR, or Small Modular Reactors. To find out more, Futura met Jean-Michel Ruggieri, head of the SMR program at the CEA (Atomic Energy and Alternative Energies Commission), and Karine Herviou, deputy director general in charge of the nuclear safety division at IRSN ( Institute for Radiation Protection and Nuclear Safety). Strongly resembling our current reactors, the SMRs are however, as their name suggests, much smaller. “To give an idea, an EPR produces between 4,500 and 5,000 thermal megawatts, while an SMR is more around 500 thermal megawatts”explains J.-M. Ruggieri. “The IAEA (International Atomic Energy Agency) already lists 70 projects available on its site”, says K. Herviou. Several are already in advanced stages, notably in Russia, where the first floating SMRs saw the light of day in 2020, or in the United States where the reactor Nuscale received design approval.

Among them, one in particular catches our attention: Nuward, for ” Nuclear Forward”. Officially announced in 2019 by EDF, its principle is the same as a conventional reactor, but smaller! “An SMR, like any nuclear reactor, consists first of all of a boiler block which produces heat, explains J.-M. Ruggieri. Except that it is 5 to 10 times smaller, therefore creates even less energy than a conventional reactor. » And Nuward will work just like PWRs (Pressurized Water Reactor) currently used in France, with pressurized water to slow down and moderate the neutrons emitted in the vessel. A project that should see the light of day in ten years. “The goal for Nuward is to lay the first concrete in 2030, but the precise site has not yet been determined. Then, other SMRs will follow, potentially in France but not only”, explains J.-M. Ruggieri.

Because the term “modular” means that these small reactors could be assemblies of spare parts, themselves built in the factory. These reactors could therefore eventually be “serial products”, explains K. Herviou, although design questions remain, particularly with regard to the steam generators. “The technical particularity of the design is often found at the level of the reactor boiler: the goal for Nuward is to integrate all the elements of the primary circuit in the vessel. We are talking about an integrated concept. This therefore includes the steam generators (GV), which are, in the case of power PWRs, larger than the vessel itself. The challenge is therefore to miniaturize them: for Nuward, we started with plate steam generators which required dedicated technological development”, explains J.-M. Ruggieri.

Decarbonizing energy in countries still using coal-fired power plants

In the future, these reactors could potentially be perfectly integrated, without replacing those that already exist. “The primary goal of such reactors is to decarbonize energy production, and in particular for industry. Eventually, it will be necessary to replace coal and gas with other carbon-free energy sources: solar, wind, biomass, and nuclear.”, explains J.-M. Ruggieri. They would thus be added to the energy mix, but not exclusively. “SMRs would not only be used to generate electricity from nuclear energy, they could also contribute directly to producing heat for district heating, or even hydrogen, using electrolyzers. »

These small reactors would also be implantable in sites that cannot accommodate large power plants, or old coal-fired power plant sites, whose power is often around 300 MWe, equivalent to that of SMRs. Due to their small size, the costs will also be lower, allowing “to countries that cannot have a large power plant to have access to carbon-free energy”, explains J.-M. Ruggieri. “In total, more than 3,000 coal-fired power stations need to be replaced in nuclear-prone countries. The ideal would be to replace them by 2040, so that gives us good market depth. » There are still questions of safety, in addition to those of design, as Karine Herviou explains. “Many consider that low power is equivalent to lower risks, therefore lower safety requirements. At IRSN, on the contrary, we demand safety equivalent to that of power reactors. »

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