REACTOR TECHNOLOGY | DUAL FLUID


800-5000 (Depending on size) 2000 Right, figure 4: Estimated energy


return on investment (EROI) for Dual Fluid compared to other power sources


1000 500 4-9 0 Wind Coal Hydro Nuclear Dual Fluid 30 35 100 1500


EROI = E out E in


V production of hydrogen and synthetic fuels. “Green” hydrogen production today involves high energy losses, whereas a strong nuclear heat source opens up the possibility of high temperature steam electrolysis (HTE), which is more efficient than current processes. Hydrogen production via HTE could undercut the current cost of green hydrogen from wind power many times over and is estimated to be cost-competitive with methane steam reforming, Dual Fluid estimates.


Energy return on investment The energy return on investment (EROI) for a power plant is the ratio of the energy gained to the total amount of energy expended over the complete life cycle (including construction, operation, fuel, decommissioning): EROI = E out {over} E in


Below, figure 5: Sketch of the fuse plug


Liquid fuel


Fossil-fuelled power plants achieve an energy return of around 30. Solar and wind, including storage, achieve single-digit numbers. While an energy return of 30 made the industrial revolution possible and is still sufficient to supply an industrial country today, a return to less efficient technologies could amount to a step backwards, Dual Fuel argues: energy will become more scarce and increasingly expensive, potentially leading to declining standards of living. Modern, people- and


Cooling Melting plug


nature-friendly societies must aim to provide reliable energy in large quantities for little money and with a small ecological footprint, Dual Fluid believes, and that “a high energy density fuel


can achieve that.” Today’s light-water reactors


Drain tank


have an energy return of around 100, which means that they


outperform fossil-fuelled power plants by a factor of three. But what sounds good


38 | July 2022 | www.neimagazine.com


actually indicates underperformance – because nuclear fission releases not three times, but millions of times more energy than a fossil combustion process, Dual Fluid points out. Why does today’s nuclear power fall so far short of its


potential? A look at the energy expenditure involved in a typical


LWR (Figure 2) shows that 80% of it is accounted for by the provision and disposal of the fuel – ie, mining and refining of the uranium as well as the production, recycling and disposal of the fuel elements. This is high because today’s reactors can only turn a negligible proportion of the mined uranium (around 1%) into useful energy. The rest of it, mostly mixed with fission products, must be disposed of as nuclear waste. Power generation with today’s LWRs is, therefore, not


a high-yield or profitable system. High investment costs and regulatory requirements completely offset the energy advantage over fossil-fired power plants. On the whole, the potential of nuclear fission remains mostly unused, Dual Fluid argues. A new generation of reactors (“Generation IV”) may achieve gradual but not fundamental increases in efficiency. This is because either the concept of fuel rods is maintained, or the concepts build on older molten salt reactor designs. In the latter, the same liquid both carries the fuel and provides heat removal, leading to suboptimal results for both functions. Moltex Energy’s design is an exception to this. It opts for liquid fuel contained in solid fuel rods. The Dual Fluid reactor design – which its developers describe as “Generation V” – with concentrated liquid fuel and lead cooling, combined with the recycling of the fuel, reduces the energy expenditures related to the fuel to a fraction, as shown by the blue areas in Figure 3. Further efficiency gains result, as already noted, from the relative compactness of the system, due to the high power density (shown as the green areas, Figure 3). Overall, the energy expenditure for a DF300 power


plant drops to a tenth of that for a typical LWR, and this inevitably lowers costs. Indeed, the energy return increases, depending on the size of the reactor, to 800-1000 for the DF300 and around 2000 for the DF1500. Figure 4 compares


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