FAST BREEDERS | FUEL AND FUEL CYCLE


conventional pressurised water reactors have been cheap enough to run using once-through enriched fuel and then disposing of it. This is only a small part of the overall cost of building and running a reactor, they say, and with fresh uranium fuel extremely cheap in a historically oversupplied market, there has been little incentive to use fissionable materials more efficiently in fast reactors. However, this is now changing. With the ongoing


reconsideration of nuclear power, driven by the acknowledgement by most experts that net zero targets will not be achievable without it, uranium reserves are a consideration for the long term. Modular fast reactor designs have now been produced by reputable companies in numerous countries – varying from start-ups to older engineering companies – several of which are already close to prototype or first-of-a-kind deployment. There are other factors in which fast reactors are able


to support further growth in the nuclear sector. One of the main barriers to new nuclear development of conventional light water reactors is the political challenge of long-term waste management. This is among the most oft-cited reasons for continued opposition to nuclear power and while deep geological disposal strategies are entirely feasible technically and economically, they add to the sense that nuclear power is somehow inherently unsafe and will leave a toxic legacy for unborn generations many millennia into the future.


Using spent fuel in a new generation of fast-neutron


reactors would largely eliminate it as a long-term waste management concern. Fast reactors are able to use all the long half-life actinides left over in spent nuclear fuel. The radioactivity of the remaining waste – which will then be composed mostly of fission products with short half-lives – will decline to the original uranium ore levels within as little as 200–300 years. This makes surface storage feasible and reduces and simplifies if not removes altogether, the need for deep geological disposal with complex design considerations taking into account million-year timescales. Shortening the time frames of radioactive waste storage and disposal processes could make it easier to demonstrate their safety and communicate this to the general public, the authors contend. Given fast reactors are able to manage waste materials


such as spent fuel and materials currently intended for deep geological disposal, they may be diverted from the conventional waste stream. This would turn an economic and political burden into a useful part of a legitimate circular economic activity and also remove one of the key political sticking points for new build reactors. Repurposing and reducing this legacy using a waste-to-


energy approach would have wide political appeal and be environmentally beneficial as a fully efficient way to use uranium. IT is also likely to curb the need for additional uranium mining, to support the ongoing increase of nuclear needed to tackle the climate emergency.


Complementary energy Many of the new fast reactor designs also include a load- following component, such as via thermal storage in molten salts. This capability will allow them to rapidly respond to changing grid needs in order to balance intermittent power delivered by wind and solar, and provide peaking power in place of traditional natural gas plants, the report says, solving the intermittency problem that will otherwise make


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100% clean grids difficult to achieve, due to the lack of cost- effective large-scale electricity storage options. The authors argue that fast breeder reactors must


therefore be deployed in such a way as to reduce grid congestion and increase security of supply to enable the deployment of wind, solar and nuclear for the majority of electrical power generation and heat supply in a net zero Europe. The report concludes with a list of wants, primarily that


all stockpiles of nuclear material – including plutonium, depleted uranium, actinides and spent fuel – should be reconsidered as potential fuel for the future. Modular fast reactors, including the supply chain,


licensing and validation of their fuel cycle, should be accelerated to rapid mass deployment to support wind and solar in the achievement of a net zero economy. Meanwhile, resources should be allocated urgently to


regulators to more rapidly assess reactor designs using a fully closed fuel cycle which leave mostly short-lived fission products as waste, simplifying and reducing the scale of deep geological disposal systems. Regulators must also increase their capacity and fast-track new designs for build-outs beginning within five years, and regulatory approval should apply regionally or even internationally with safeguards. Priority should also be given to high-temperature


reactors which produce hydrogen most of the time but can switch to multi-gigawatt support of electricity grids during low wind and solar periods. Governments must also take a systems approach, considering steel-making, transport, electricity and social issues in siting and permitting reactors.


As the authors state though, the rapid deployment of


today’s modern, commercially available ‘once-through’ nuclear reactor technology should not be abandoned, even as we push for fast reactors to become available. Fast breeder reactors are able to work together with existing reactor designs, since breeders produce enough fuel to resupply not just themselves but also an additional conventional reactor of the same power. All forms of nuclear can thus also work together, in partnership with renewables. ■


Below: Russia is one of the few nations to pursue fast breeder reactor development with its BN series


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