Nuclear technology |
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 could 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 E in
Above: Figure 3. Life cycle energy consumption for a Dual Fluid 300 MWe modular power plant (DF300) vs LWR (estimates based on Vattenfall and Dual Fluid calculations)
be used, significantly increasing the amount of fissile material in the reactor core. The compactness of the core reduces the amount of structural materials required, which allows the use of expensive, high-temperature and corrosion-resistant materials.
Liquid lead as a coolant dissipates the heat without slowing down the neutrons in the reactor core.
High power density goes hand in hand with high efficiency: a small Dual Fluid core rated at 300 MWe is eight to ten times more efficient than current LWRs. With larger cores, power density and efficiency increase further. Because Dual Fluid, as a fast reactor, operates with a high neutron excess, the reactor – in combination with the Dual Fluid recycling plant – can fully utilise any fissile material, including thorium, natural uranium, and nuclear waste from current reactors.
Nuclear power redefined The principle of separate cycles for fuel and coolant “completely redefines nuclear power”, Dual Fluid believes. In combination with the Dual Fluid recycling plant, all the fuel loaded is used productively, without the need for a final repository.
Application of the Dual Fluid principle is not confined to SMRs, but the first realisation of the concept is expected to be a small modular reactor, rated at about 300 MWe, the DF300 (Figure 1).
In the DF300 modular power plant, the fuel is delivered to the power plant in a sealed cartridge. There it is heated and pumped in liquid form into the reactor core, where it produces heat for around 25 years. The spent fuel is then returned to the cartridge and transported for recycling.
Larger cores, such as in the DF1500 power plant, – 1500 MWe/3000 MWt – have a higher fuel throughput and can be combined directly
20 | April 2022|
www.modernpowersystems.com
Above: Figure 4. Estimated energy return on investment (EROI) for Dual Fluid compared to other power sources
with a Dual Fluid recycling system. This enables permanent fuel processing on site. The Dual Fluid recycling process differs fundamentally from ‘conventional’ fuel reprocessing based on PUREX wet chemistry. In the Dual Fluid recycling plant, the spent fuel is first converted into liquid salt form and then separated into its components using a distillation process that is already established outside the nuclear industry. All fissionable materials are then mixed with fresh fuel and returned to the reactor core. This recycling method, based on pyrochemical distillation, enables the complete utilisation of any fissionable material, achieving, for the first time, a truly circular economy in the nuclear fuel chain, says Dual Fluid.
In addition to electricity generation, the DF1500 power plant, with its 3000 MWt of heat, is particularly suitable for energy-intensive heat applications such as the 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
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 Fluid argues: energy will become more scarce and increasingly expensive, potentially leading to declining standards of living. Modern, people- and 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 “a high energy density fuel can achieve that.”
Today’s light-water reactors 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 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 around 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
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