As Next Big Future reports:
China has completed the basic technology research and published a development roadmap for a Generation IV demonstration SuperCritical-Water-cooled Reactor that could be commissioned in 2022.
This reactor could achieve costs that are up to half the cost of current reactors and have higher efficiency.
They could be low cost enough to displace all future coal plant construction in China starting in 2025-2030.
$900 per kilowatt is over three times cheaper than the estimated overnight cost of advanced nuclear reactors ($3100 per kilowatt) estimated by the US department of energy
In China, water-cooled reactors are and will be the main reactor concept for the generation of nuclear power. China’s experience and the technology developed in the design, manufacture, construction, and operation of nuclear power plants are mainly concentrated on water-cooled reactors. Thus, the development of SCWRs is a smooth extension of the existing nuclear power generation park in China. From a technological point of view, an SCWR is a combination of the water-cooled reactor technology and the supercritical fossil-fired power generation technology. Hence, SCWRs ensure the technological availability.
The Nuclear Power Institute of China said the SCR-1000 reactor block will have a capacity of about 1,000 megawatts.
The Super Critical Water Reactor (see wiki) is all about very high pressure water that is ‘super-critical’, which to a lay person such as myself means it’s under so much pressure that the water cannot just boil away to vapour: but gets stuck somewhere between the two phases. It’s ‘supercritical’ liquid, not normal water, and not gas. My least favourite thing about this is the high-pressure. In my poor layman’s understanding of such things, that means there is slightly more risk than the liquid metal cooled reactors that don’t have high pressure. (There’s less pressure to ‘burst’ and leak).
To explain why they did this I’m going to quote directly from the wiki. Ready?
Above the critical point, steam and liquid become the same density and are indistinguishable, eliminating the need for pressurizers and steam generators (PWR), or jet/recirculation pumps, steam separators and dryers (BWR). Also by avoiding boiling, SCWR does not generate chaotic voids (bubbles) with less density and moderating effect.
Pause for a moment. The water is acting as the moderator, which means:
“neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235.”
So this is a ‘slow’ neutron reactor compared to my favourite, the Integral ‘Fast’ Reactor, which uses fast neutrons to breed up the fuel and run the reaction.
Back to why I think they chose a Super-Critical Water Reactor: and remember, the wiki was just talking about ‘voids’ (bubbles) that can interrupt water moderation of the neutrons:
In a LWR this can affect heat transfer and water flow, and the feedback can make the reactor power harder to predict and control. SCWR’s simplification should reduce construction costs and improve reliability and safety. The neutron spectrum will be only partly moderated, perhaps to the point of being a fast neutron reactor. This is because the supercritical water has a lower density and moderating effect than liquid water, but is better at heat transfer, so less is needed. In some designs with a faster neutron spectrum the water is a reflector outside the core, or else only part of the core is moderated. A fast neutron spectrum has three main advantages:
In other words, it’s a higher-pressure but cheaper version of an IFR, but without the safety advantages of normal pressures. But nevertheless, they’ll still have the latest safety features as part of their standard designs.
As nucnet says:
Some 100 experts evaluated 130 reactor concepts before GIF chose the final six. Some 100 experts evaluated 130 reactor concepts before GIF chose the final six. They are the gas-cooled fast reactor (GFR), the lead-cooled fast reactor (LFR), the molten salt reactor (MSR), the sodium-cooled fast reactor (SFR), the very high temperature reactor (VHTR) and the supercritical-water-cooled reactor (SCWR). They are the gas-cooled fast reactor (GFR), the lead-cooled fast reactor (LFR), the molten salt reactor (MSR), the sodium-cooled fast reactor (SFR), the very high temperature reactor (VHTR) and the supercritical-water-cooled reactor (SCWR).
SCWRs are high temperature, high-pressure, light-water-cooled reactors that operate above the thermodynamic critical point of water. SCWRs are high temperature, high-pressure, light-water-cooled reactors that operate above the thermodynamic critical point of water. They have the potential of lower capital costs for a given electric power of the plant and of better fuel utilisation, GIF said. They have the potential of lower capital costs for a given electric power of the plant and of better fuel utilisation, GIF said.