SMRs & ADVANCED REACTORS | USING FERTILE FUEL
Above, figure 3: Cross section view of the Copenhagen Atomics fertile fuelled molten salt reactor. Hot section, left of the insulation wall, is typically 600°C and the cold region, to the right, is typically 30°C
the reactor is planned at Paul Scherrer Institute (PSI),
Switzerland, in 2027. This first demonstration of criticality seeks to avoid delays by minimising complexity. Therefore, it does not have transfer of uranium from blanket to fuel salt. It does not have the SiC/SiC core envisaged for the commercial offering, and only some of the fission products are removed. For subsequent tests additional features will be added. However, with the first test at PSI, we will be able to validate the accuracy of the simulations to a point where
uncertainties related to the postponed features become negligible. Already today the simulations carry substantial certainty that the Copenhagen Atomics Onion Core®
thorium molten
salt reactors can in fact cross the chasm to fertile fuelled reactors. But the test in 2027 will be the single event where most uncertainty is removed, between today and the point in time at which the first reactor attains 25 years of operation. The uncertainties around the Copenhagen Atomics
Neutron economy of CA thorium reactor (first 20 years)
reactor concept mainly revolve around the use of SiC/ SiC materials for core components, Li7 enrichment, online fission product removal and transfer of uranium from blanket to fuel salt. All these concepts are at a low TRL at time of writing, but are all expected to mature to commercial reactor deployment by 2030. The limitation on the lifetime of the reactor is a
combination of corrosion, salt compatibility, temperatures, stress/strain and radiation. It is currently the belief that the reactor core will be the limiting factor and that a life of 5 years can be achieved after a few iterations. A large percentage of the remaining work revolves around testing and approval of the materials used in critical components, such as reactor core, pump, pipes, heat exchangers and dump tanks.
Years
A new era Prototype (non-nuclear) reactors are already running in Copenhagen, Denmark, and the next big milestone will be to achieve criticality in a reactor test expected in 2027 in Switzerland. The Copenhagen Atomics reactor concept ushers in a new era of fertile fuelled reactors, promising orders of magnitude lower fuel cost and smaller fuel volume, smaller reactor core size and, overall, radically less expensive reactors. These reactors create less waste, can easily be mass
Above, figure 4: 25 year burnup simulation for the Copenhagen Atomics 100 MWt Onion Core®
reactor. All core materials, blanket, fuel salt,
structural materials and heavy water are part of this burnup simulation. Lanthanides fission products are not removed for the first 10 years
26 | June 2025 |
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manufactured on assembly lines and transported on regular lorries and can even use transuranics from spent LWR fuel as kick starter fuel. It is likely that electricity prices of around $20/MWh can be reached from 2035. ■
Neutron absorption distribution per fission
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