In small jars, the best ointments? The nuclear industry is aggressively developing a new line of small-format nuclear reactors in hopes of disintegrating the cost and safety issues of conventional reactors: small modular reactors (SMRs).
By definition, SMRs have a maximum capacity of 300 megawatts, compared to about 1000 for conventional reactors. Such a reactor can therefore be sufficient to supply electricity to a few villages or a large factory in a remote region. SMRs are also “modular”: their designers suggest that it will be possible to install them in groups in order to generate electrical power similar to that of today’s large power stations.
The nuclear industry does not think that, in terms of electricity production, it also envisages that SMRs can supply water heating networks, desalinate seawater, or provide steam for applications industrial.
Currently, traditional reactors must be built where they will be used, depending on local specificities. PRMs can be manufactured in the factory, in a standardized manner, before being shipped by truck, train or ship.
The “chain” production of SMRs could reduce costs, but the operation of each reactor will suffer from losses of economies of scale compared to large-format reactors. Analysts do not yet know which of the two phenomena will weigh more heavily in the balance.
Another theoretical advantage of PRMs is in terms of safety. First, the smaller amount of nuclear fuel sitting in each reactor lessens the potential damage in the event of an accident.
Second, some designs allow for “passive cooling” in the event of an accident: no electrical power is required to activate fans or pumps to evacuate excess heat from the reactor. Natural ventilation or convection take care of this.
Security
According to Guy Marleau, professor of physical engineering specializing in nuclear reactors at Polytechnique Montréal, this “intrinsic safety” advantage could play a determining role in favor of the adoption of SMRs.
Many PRM concepts are based on proven technology principles. Many are “pressurized water reactors”, which is the most common type of conventional reactor in the world.
In these reactors, the combustion of uranium-235 heats water in a high-pressure circuit. The thermal energy of this water is transferred to a secondary circuit, where steam is heated, turning a turbine.
Other designers of small reactors rely on new technologies, such as “fast neutron” or “molten salt” reactors. These reactors produce steam at extremely high temperatures, which has advantages.
“You get more efficiency when it comes to converting energy into electricity. But also, you can use it for other industrial applications, such as resource extraction,” explains Julianne den Decker, vice-president of Candu Energy, a subsidiary of SNC-Lavalin specializing in nuclear.
Fast neutron reactors also make it possible to consume uranium “much more efficiently”, remarks Mr. Marleau. “So less fuel to produce a lot more energy, and a lot less waste at the end,” he summarizes.
Because of the high efficiency of fast neutron reactors, SMR designers claim that their reactor will be able to operate for years without refueling — which, in remote areas, is an added advantage.
In Russia, a floating nuclear power plant has been producing electricity since May 2020 thanks to two 35 megawatt PRMs. According to the International Atomic Energy Agency, more than 70 commercial PRM designs are currently in development worldwide, some of which have reached the construction stage.
With Ulysses Bergeron