The real trouble with the light water reactor is not the nuclear part but the steam turbine it is attached to.
Unfortunately people have a way of driving while looking in the rear view mirror and much of the discussion around nuclear energy revolves around issues of the 1970s.
In the 1970s coal burning power plants were the cost king of power plants. There was some concern about making them cleaner, but by the 1980s gas turbine power plants with 10 times the power density (e.g. 1/10 the capital cost) were becoming widespread and people quit building coal plants.
(A big literature got left behind about how to drive a gas turbine from coal, on paper it would be lower capital cost than a conventional coal plant, but the technology never got developed at full scale.)
Even if the heat was free it would be hard for a steam turbine based power plant to compete with gas turbines.
Now it should be possible to build a nuclear power plant based on the brayton cycle using helium or carbon dioxide or some similar gas as a working fluid. You then need to use helium or sodium or lead as a coolant because the pressure would be too high with water.
Fast reactors are the best developed option, followed by the prismatic HTGR, then the thorium reactors. Pebble-bed HTGR looked pretty good until an expose came out that a German pebble bed reactor had a difficult time... Turns out pebbles that slide past each other just fine in air will get stuck on each other and crack in helium.
When Bill Gates and others go around saying we have to get over the safety issue they are continuing the stigma. Nuclear power is not going to get out of it's funk unless it has a cost story that looks good when everything goes right -- which is not the case with the LWR.
> Even if the heat was free it would be hard for a steam turbine based power plant to compete with gas turbines.
This isn't true. People started attaching steam turbines to gas plants precisely because it made economic sense to tap into waste heat for co-generation.
Nobody expects nuclear to compete against fossil fuels. But fossil fuels release carbon. Nuclear is necessary because it's the only consistent form of carbon-free energy production save for geographically dependent solutions like hydroelectricity and geothermal power.
> Nuclear power is not going to get out of it's funk unless it has a cost story that looks good when everything goes right -- which is not the case with the LWR.
True. One solution is to attach a cost to account for the impact of climate change caused by burning fossil fuels. Then nuclear will be competitive with fossil fuels. And competitive against intermittent sources since those require fossil fuels as a backup, at least until some feasible form of grid-scale storage is developed.
The "steam turbine attached to the gas plant" as a system benefits from the high power density of the gas turbine. For nuclear to do the same it would need to run at high temps (e.g. sodium, sodium fluoride, ...) and be coupled to a combined cycle powerset and heat recovery system...
Still needs the high temps!
Nuclear competes not just with fossil fuels but with "burn the fossil fuels, capture the carbon, inject the CO2 back into the ground option", which might not be so bad if this gets perfected
I think you misunderstand what combined cycle means.
In a gas turbine - without cogeneration - the gas turbine is driven by heating air and the expanded air spins a turbine, which spins a dynamo (as well as the compressor blades). It's like a jet engine, but hooked up to a generator. The exhaust air is hot and we do nothing with that waste heat.
Starting a couple decades ago, people started putting boilers next to the gas turbine exhaust. This boiler is heated by the gas turbine exhaust, and the generated steam drives a turbine. It's combined cycle because there's two heat engines: the jet engine which is driven by hot air, and then the steam turbine driven by steam generated from the jet engine's exhaust. It's tapping into waste heat to generate steam, and that steam drives a turbine. There's two Carnot cycles happening. One in the gas turbine, one in the steam turbine.
There's no such thing as a combined cycle nuclear plant, no matter how much thermal energy it can put out. The plant heats water which drives a turbine. If you have a reactor that generates more heat, then you can generate more steam and drive a larger turbine or additional turbines. But there's still only one heat engine, one cycle.
I guess you could use the heat exchanger as a second steam generator to drive a second turbine. But in order for that to work, the first steam turbine would have to be very inefficient and deliver a lot of waste heat to the second turbine. It'd be better to just drive two turbines in parallel or a larger turbine.
In fossil fuel use the gas turbine works by internal combustion -- heat is added by a fire inside the device and the exhaust goes out the back.
There are closed cycle gas turbines that put heat in with a heat exchanger and some have been built for non nuclear use but they haven't been competitive with alternatives (e.g. open cycle gas turbine) since they quit using mercury as the working fluid.
Something like that could heat up steam for a bottoming cycle. It's not a matter if it is possible, its a matter if it is practical.
A nuclear reactor can operate at much higher temperatures using coolants other than water, and it has been done (see the british AGR and the American FFTF) but there are a huge number of details that must be perfected to make it routine.
I think the GGP post is trying to suggest building a nuclear plant with high temperature coolant that runs a combined cycle generator. I don’t know whether this is actually cost effective.
There is a good classroom demo where somebody melts a molten salt in a crucible with a bunsen burner and demonstrates that it becomes transparent, conducts electricity, etc.
A molten salt can be used as a coolant, competitive with sodium in fast reactors. It is not so chemically reactive and you can see through it (imaging repairing a reactor you cant see -- a bad problem in the 1970s, not so bad now with ultrasound). It is less heat conductive than sodium though, which hurts the econonics of fast reactors which need a large amount of nuclear fuel to form a critical mass and can get more value out of that critical mass by getting as much heat out as possible.
You can dissolve uranium, thorium and/or plutonium in that salt and that is proven (see MSRE) but needs development.
Most of the dangerous products of the reaction stay in the salt, it works a lot better than you think it would. (when a sodium reactor melted down in the late 50s they never detected radioactive iodine because it reacted with the sodium and the salt dissolved in the coolant, then it decayed in place.)
You still have some noble gases coming out and fine particles of platinum group metals coming out, but that's less of a problem than finding materiald that can survive 30+ years of that treatment.
There are many solutions for this. Corrosion is absolutely a problem you can find engineering solutions to. And Moltex has very elegant one. Other companions like Terrestrial are simply replacing the reactor core after 7 years.
The MSR experiment in the 60s proved it worked. They had some corrosion issues after quite a while in operation, but still operated if for quite a while, and that was in the 60s.
Unfortunately people have a way of driving while looking in the rear view mirror and much of the discussion around nuclear energy revolves around issues of the 1970s.
In the 1970s coal burning power plants were the cost king of power plants. There was some concern about making them cleaner, but by the 1980s gas turbine power plants with 10 times the power density (e.g. 1/10 the capital cost) were becoming widespread and people quit building coal plants.
(A big literature got left behind about how to drive a gas turbine from coal, on paper it would be lower capital cost than a conventional coal plant, but the technology never got developed at full scale.)
Even if the heat was free it would be hard for a steam turbine based power plant to compete with gas turbines.
Now it should be possible to build a nuclear power plant based on the brayton cycle using helium or carbon dioxide or some similar gas as a working fluid. You then need to use helium or sodium or lead as a coolant because the pressure would be too high with water.
Fast reactors are the best developed option, followed by the prismatic HTGR, then the thorium reactors. Pebble-bed HTGR looked pretty good until an expose came out that a German pebble bed reactor had a difficult time... Turns out pebbles that slide past each other just fine in air will get stuck on each other and crack in helium.
When Bill Gates and others go around saying we have to get over the safety issue they are continuing the stigma. Nuclear power is not going to get out of it's funk unless it has a cost story that looks good when everything goes right -- which is not the case with the LWR.