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Belgian demonstrator of the first lead-cooled Small Modular Reactor

Lead-cooled, fast SMR in Belgium

By 2035-2040, SCK CEN wantsto build a Belgian demonstration model of the first lead-cooled Small Modular Reactor (Lead Fast Reactor or LFR).
We are thus betting on a design for an innovative, more advanced SMR.

2023_SCK CEN_LoodBismut_SMR

What is a fast reactor?

Fast reactors work with "fast neutrons". To keep the neutrons fast, the reactor core cannot be cooled with water. Indeed, light molecules, such as water, inhibit neutrons. Heavy molecules such as sodium and lead-bismuth are eligible coolants, however.

Why do we want to build a fast reactor?

SCK CEN can benefit from MYRRHA's development process for the construction of the demonstrator of the first Belgian SMR.

MYRRHA is not an SMR, but it shares some principles, such as compactness, the coolant, and thus fast neutrons. SCK CEN has built up specific expertise in nuclear technologies cooled with lead-bismuth and is a global leader in this field. The knowledge gained for MYRRHA can thus be transferred to the development project of the SMR demonstrator.

💡 Learn more about MYRRHA or discover more about SMR's!


Advantages LFR-SMR

A fast reactor has considerable advantages over a water-cooled reactor:

✔️ less high-level waste

✔️ increased fuel resource utilization

Fast reactors produce less high-level radioactive waste. In fact, reactors with fast neutrons can split any type of uranium, including, for example, uranium 238 and plutonium 240. So we will produce less of this long-lived radioactive material, AND we could reuse spent nuclear fuel from current reactors as fuel. Thus, the volume and radio-toxicity of the radioactive waste can be reduced.

Also, energy efficiency is much higher because much more uranium-238 is consumed than uranium-235

What happens after the demonstrator has been built?

SCK CEN has done a preliminary study on Small Modular Reactors and will now focus on building a technology demonstrator.

However, in addition to the technology that needs to be proven, there are some important requirements for successfully implementing Small Modular Reactors in our future energy supply.


Small Modular Reactor may eventually be cheaper, provided that the market is sufficiently large and therefore mass production is possible. We would argue that Small Modular Reactors are economically advantageous because we can standardise and mass-produce them. However, each country has its own nuclear safety authority. Close collaboration or some kind of homologation as in the automotive industry could encourage everyone to think in terms of larger "market solutions".


SCK CEN will build a technology demonstrator at its site in Mol. The final location of several Small Modular Reactors in Belgium has not yet been decided and will also require a great deal of study in the follow-up process.

Nuclear Exit Law

Although the Belgian government may have commissioned the study of Small Modular Reactors for Belgium, this is still at odds with the Nuclear Exit Law. To achieve a successful succession project, this will require further adjustments.

Collaboration with partners

For a successful SMR story in Belgium, cooperation with industrial partners from home & abroad is indispensable. These partners and collaboration form a separate track linked to building a technology demonstrator.

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