Small modular reactor (SMR) and their fuels

Aiming particularly at the market for direct energy supply to industrial customers, the new reactor designers are breaking away from the historical model by developing reactors that are 10 to 400 times less powerful than the EPR reactor in Flamanville, hence their designation as ‘small’ reactors.

The thermal power of the SMRs currently monitored by the ASNR is between 10 and 540 MWth.

This significant reduction in power also implies a radical adaptation of the economic model for the development of these reactors, on the one hand by seeking to reduce construction times, and on the other hand by relying on standardization and mass production.

It is this new industrial model of mass production with a large proportion of factory prefabrication that gives these reactors the name ‘modular’ small reactors.

Replacement of fossil-fuel power plants

In addition to the existing nuclear supply, and depending on the target markets, smaller reactors could replace existing coal, gas or oil-fired power plants.

Local supply of electricity or heat

The production of energy for sectors that are difficult to decarbonize (industrial or district heating), the desalination of seawater, the production of green hydrogen, or even providing heat and electricity to energy-intensive industries, all support the emergence of new energy production devices such as SMRs.

Development of systems for isolated sites

Transportable by truck, train, ship or plane, SMRs also open up possibilities for supplying electricity or heat to isolated sites not connected to the electricity grid.

In this context, in March 2022 the Government launched a programme calling for projects for innovative nuclear reactors aimed at fostering the emergence of an ecosystem of nuclear start-ups.

As part of the France 2030 plan to decarbonize the economy, this call for projects aims in particular to develop new nuclear reactor concepts.

This has led to the recent emergence of around ten new companies that are now carrying SMR projects. Their economic model is based on three pillars:

The SMR projects currently being studied in France involve four types of technology:

Water reactors • Solid fuel: Uranium • Moderator: Water • Coolant: Water

Liquid metal reactors • Solid fuel: Mixed uranium and plutonium oxide (MOX-RNR) • No moderator • Coolant: Liquid metal (sodium, lead)

High temperature reactors • Solid fuel: Uranium (‘TRISO’ particles) • Moderator: Graphite or heavy water • Coolant: Helium or sodium gas

Molten salt reactors • Liquid fuel: Plutonium in salt form • No moderator • Coolant: Molten salt

Water reactors make up the vast majority of reactors currently in operation worldwide, while other SMR technologies, already known and developed for many years, have so far only led to the achievement of a few experimental or prototype reactors, with no industrial-scale operation.

Development programs may vary depending on the sector and the project. They may involve progressing through different stages of development, including the following types:

• Experimental reactor: conducting experiments to acquire the theoretical knowledge needed to finalize the design of the industrial reactor (demonstrator/first-of-a-kind unit) and demonstrate its safety
• Demonstrator / industrial prototype: a reactor designed to demonstrate to investors or customers that a level of industrial maturity has been achieved, and, if necessary, to conduct tests to validate the technological choices required to finalize the design of the industrial reactor and demonstrate its safety
• Pioneer: the first full-scale industrial reactor

Connected to the development of these modular reactor projects is the inevitable issue of the need for the fuel required for their operation. This need is not only in terms of fuel availability but also in terms of production and industrialization capacity. Also, the development challenges vary greatly depending on the reactor technology:

	Technological sector	Associated fuel	Potential technological challenges?	Industrialization capacity of current tools
	Light water reactor	Uranium enriched between 3 and 5% (LEU)	-	Existing
	Liquid metal reactor	Mixed uranium and plutonium oxide (MOX-RNR)	-	To be developed
	High-temperature reactor	‘TRISO’ particle of uranium enriched between 5 and 20% (HALEU)	TRISOs Manufacture	To be developed
	Molten salt reactor	Mixed uranium and plutonium oxide embedded in salt	Salt Manufacture	To be developed