SMR: small modular nuclear reactors


If the environmental fight against greenhouse gases were to intensify significantly and combine with the rapidly growing demand for carbon-free electricity, SMRs could provide tailored and competitive responses to the emerging energy situation:

  • as a producer of electricity for isolated consumers, supplied by limited networks and intermittent sources requiring load monitoring;
  • as a producer of high-temperature heat for desalination in dehydration areas, for the propulsion of large ships, for the supply of hydrogen to industry, refining, methanationetc.

Certain challenges need to be met for future industrial use.

Safety

Most SMRs are integrated into vertical cylindrical casings (typically 20 m high and 5 m in diameter), at the base of which a combustible core is placed, which makes it possible to use the convection rise of their heat-carrying fluids to ensure a total passive circulation, independent of active pumping devices, which in case accidents carry risks. During downtime, this design enables passive dissipation of residual power (by natural convection).

The modularity of SMRs presupposes their factory production and their certification after careful quality control before being allowed to operate by government security authorities. This process offers greater guarantees than can be provided by the current “on-site” implementation of power generation reactors.

Note, however, that the potential progress made by SMR in terms of overall safety can only be realized in industries that are thoroughly controlled across all the technologies they implement, especially in materials. This is the case with SMR in the PWR sector, which benefits from 60 years of experience and can therefore immediately provide innovative safety solutions.

Proliferation

The economic success of SMRs means that they are industrially produced in large quantities for different users and implemented by small staffs.

The very concept of SMR is therefore associated with a strong geographical dispersion accompanied by a structural risk of diversion of SMR fuels towards hostile purposes.

Technologically, SMRs could be equipped with deterrent anti-proliferation fuel cores, either filled with low-enriched uranium for a lifetime of several years (already irradiated and therefore containing radiotoxic actinides, making handling dangerous), or conversely filled with highly enriched uranium for a lifetime equal to that of the SMR , the core is inseparable from its metallic structure, but at the end of its life it contains a large amount of plutonium.

Safety

Thanks to their reduced size, autonomy and resilience, integrated SMRs can be protected from human attacks and natural disasters that could affect their operation:

  • be buried in the deep graves of the earth;
  • either by immersion in “pools”, lakes or seas (abandoned Flexblue concept), which thus ensure their safety in the event of a nuclear accident.



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