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Progressing towards the first lead-cooled SMR demonstration model

Small modular reactors (SMRs) of the future

SCK CEN is preparing the way for the commercialisation of small modular reactors with fast neutrons and lead as coolant. These SMRs have the potential to become an indispensable part of a sustainable Belgian energy system. SCK CEN wants to build a demonstration model by 2035 in cooperation with its international partners, in preparation for a commercial roll-out.


SCK CEN - Highlights 2022 (2023)

The capacity of small modular reactors can reach 300 MWe. Various SMRs can be linked to handle higher energy demands. The idea is to produce SMRs serially in factories, which will reduce the construction time on site, remove uncertainties, and feed through to lower installation costs.

SCK CEN - Highlights (2023)

Testing the technology

In 2022, the Belgian government gave SCK CEN the green light to extend the scope of its research path to include SMRs. “At the request of the federal government, we evaluated the technical aspects of all the SMR concepts currently under development worldwide,” says Marc Schyns, Director Innovative Nuclear System.


SCK CEN compared some 70 designs. “We assessed them in terms of eight criteria, including passive safety, reduction of long-lived waste, economic feasibility and, quite an important one, the time required for realization,” explains Marc Schyns. Based on this evaluation, and the situation in Belgium, SCK CEN proposes to further elaborate the SMR concept of lead-cooled reactors with fast neutrons. The ambition is to build a demonstration model in Belgium together with international partners by 2035.

“Small, modular lead-cooled reactors are a sustainable solution for Belgium to help fight climate change.”
Marc Schyns, Director Innovative Nuclear Systems

More efficient use of raw materials and less long-lived waste

The first wave of SMRs will be based on the mature technology for water-cooled reactors. However, by choosing lead as a coolant, SCK CEN will reap the advantages of the 'second wave' of small, modular reactors. Marc Schyns: “The big advantage of this technology is that the reactors use uranium more efficiently and generate less long-lived waste. Small, modular lead-cooled reactors are therefore a sustainable solution for Belgium to help fight climate change."

In addition, SMRs employ a passive cooling system. “When the reactor shuts down, the coolant automatically dissipates the heat through natural circulation. As a result, the power supply can be completely disconnected without compromising the cooling process.” In experiments for MYRRHA, SCK CEN has already shown that this works well.

MYRRHA preparatory project

MYRRHA will be the world's first research reactor powered by a particle accelerator. This research reactor will be cooled with liquid lead-bismuth. This metal alloy doesn’t differ that much from that used in a lead-cooled reactor. Marc Schyns: "We’ve been doing what’s necessary to obtain a permit for the MYRRHA research reactor for some time now. We can use the know-how acquired during MYRRHA for our SMR demonstration model. The step-by-step plan for obtaining a permit is also very useful here." In a nutshell: the development of the SMR demonstration model closely reflects the expertise acquired by SCK CEN for MYRRHA.

Global pioneer

Belgian Prime Minister Alexander De Croo expressed his pride at the academic session for the 70th anniversary of SCK CEN, where he gave a speech about the future of SMRs. “SCK CEN's unparalleled nuclear expertise is Belgium’s gateway to sustainable nuclear energy,” he said. “SCK CEN isn’t just an expert in nuclear technology that relies on lead-bismuth cooling, it’s actually a global leader. That puts Belgium in a privileged position for the challenge ahead."

New applications

Reactors that rely on innovative technologies have higher exhaust temperatures than their existing water-cooled counterparts. This opens up opportunities for new applications, such as the production of hydrogen or the supply of heat to industrial processes.

SCK CEN - 70 jaar SCK CEN (2022)
“SCK CEN doesn’t just possesses specific expertise in nuclear technology that relies on liquid-metal cooling, it’s actually a global leader.”
Alexander De Croo

Do you want to rewatch the academic session?

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