SMRs & ADVANCED REACTORS | USING FERTILE FUEL
Using fertile not fissile reactor fuel
Electricity at $20 per MWh is not just a vision, it’s the likely result in 2035 of the ongoing development by Copenhagen Atomics that is expected to result in the most cost efficient and scalable energy source in the world. Key to success is refuelling only with fertile fuel.
By Jesper Glahn, Copenhagen Atomics
ALL NUCLEAR REACTORS BUILT UP to now have required refuelling with fissile fuel periodically and looking to Generation 1 fusion reactors, they will need topping up with both deuterium and tritium. They may have a blanket where tritium is produced but not enough to sustain operation without injecting additional tritium from a 3rd party. Figure 1 shows various reactor technologies grouped by
refuelling concept: fissile fuelled with repeated refuelling vs fertile fuelled with just an initial load of ‘kickstarter’ fuel. These are further subdivided according to fuel type. The number of sides of the geometric figures (circle,
triangle, etc) denote level of difficulty. Only reactors at the circle and triangle level have ever been built. All fission reactors requiring refuelling with enriched fuel or plutonium are in the triangle category. There have been very significant investments in
Generation 1 fusion and solid fuel fast reactors hoping to leap across the chasm to the realm of reactors that only require refuelling with fertile fuel (right hand side of Figure 1).
The fuel cost of fissile fuel is typically several orders of
magnitude larger than fertile fuel. The inherent technical challenges to be solved to achieve
fertile fuelled reactors are: ● Achievement of excellent neutron economy with minimum leakage of neutrons;
● Minimisation of counterproductive neutron absorption inside the core; and
● Reduction of losses in reprocessing or when moving fissile material from blanket to centre.
The Copenhagen Atomics reactor design Copenhagen Atomics has developed a new thorium reactor design that is refuelled with fertile fuel (Th232) only. This is fuel that is not itself fissile to start with, but which can be converted to fissile materials via irradiation in the reactor. Figure 2 shows the concept, a triple fluid molten salt reactor core operating in the thermal spectrum, having a molten thorium salt as blanket, heavy water as moderator and a molten uranium salt as fuel salt. Ideally, fission only
Above: Copenhagen Atomics plans to have installed units in the early 2030s and the first gigafactory will be able to install 15–50 GW of capacity per year
24 | June 2025 |
www.neimagazine.com
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