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Molten Salt Reactors

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Re: Molten Salt Reactors

#91
post #70

Earlier quoted context omitted.

"as long as the average price is above average cost" And that's the killer. Add enough solar and wind and the average price craters, even if solar and wind cannot handle everything (without help from dispatchable sources and/or storage).

The problem with that argument is that it proves too much. It applies to everything, because solar and wind are the same as nuclear, their incremental generation cost is effectively zero once the capital is paid, so you take whatever the market price is. Which means you have a problem. It's physically possible to build enough solar and wind and storage to even handle extended periods of low sun and low wind. But if y…

Solar and wind will build out until it is no longer profitable to do so. That means: when they have driven the price of electricity when they are operating, averaged over time, down to the point they can't get a return on investment. This price point is far below where new nuclear needs it to be for nuclear to earn back its construction and operating costs.

What drives all this is that the levelized cost of energy from solar and wind is much less (a factor of 3 or 4) than the levelized cost of energy from new nuclear plants.

Nuclear, or at least many existing nuclear plants, has an additional disadvantage: it cannot cut output rapidly. If power from renewables suddenly floods the market, prices can go negative. Renewables can just stop selling in that situation, but nuclear is forced to continued to run and eat the negative revenue. The low power density of the renewables sources, usually depicted as a negative, is the source of this advantage: sunlight absorbed in PV modules can just be allowed to dissipate as heat there with no negative effects.

(In fairness, I should also mention that there are subsidies in the US that encourage renewables to keep generating even at negative prices. These subsidies will have to go at some point, and perhaps that point is now.)

What will be the final death knell for nuclear will be when short term storage gets cheap enough that the times when that's discharging will also be economic death zones for nuclear plants. I expect few of the existing operating nuclear power plants to survive after that.

Re: Molten Salt Reactors

#92
post #22

Earlier quoted context omitted.

Nuclear is a great compliment to photovoltaic. One of the reasons Japan was able to go large on PV (and cause prices to come down for the rest of us) was their huge pumped water infrastructure that had been built for nuclear. One problem with nuclear was all the excess power created at night, so they would pump water uphill at night and then run it down to generate power at the daytime peaks. Of course with PV the ti…

Nuclear is not a great complement to PV, if the PV is cheap. Cheap PV expands until there is no residual baseload demand left. At that point, nuclear power plants cannot maintain high capacity factor and their economics go all to hell.

PV for baseload? How does that work?

Everyone will use candles at night?

Re: Molten Salt Reactors

#93
post #65

Earlier quoted context omitted.

There's no likelihood of batteries scaling to certain uses, such as large long-distance air transport, or marine shipping. Most trucking as well. We either stop using those transport modes, or revert to prior forms (wind), or wire-based electrical systems (rail, canals, trucks).

Or make fuel. There are all sorts of ways to make carbon neutral diesel and jet fuel. They just aren't economic compared to pumping it out of the ground unless the externalities of burning virgin fuels are priced in with regulation.

Good point. I've been excited by fuel synthesis technologies, though they've proved difficult to develop at scale.

A Google X Project tried and failed.

Re: Molten Salt Reactors

#94

There's a lot of references to "plate out" in the article and most of the results I find on Google are paywalled by Elsevier - can some explain what the term means or point me to a resource?

When fuel nuclei split apart in a nuclear reactor, their split fragments form a variety of lighter elements. Some of these elements are so-called "noble" metals -- metals that tend toward remaining chemically stable as metals, rather than as chemical compounds with other elements. Silver, ruthenium, and palladium are some examples of noble metals. More typical metallic elements like potassium and iron, by contrast, tend to be found on Earth as oxidized chemical compounds rather than as metals.

In a molten salt reactor, most fission products either stay dissolved in the salt mix or are lost from the mix as stable gases. The noble metals are different. Their tendency is to reform as solid metal. They tend to accumulate as a metallic layer or plate of metal over other solid surfaces they come into contact with. That's what is meant by plating out.

Here is a document that specifically addresses noble metal plate-out in molten salt reactors:

http://www.skyscrubber.com/Molten-Salt-Reactor%20Technology%...

See section III.C.

Re: Molten Salt Reactors

#95
post #22

Earlier quoted context omitted.

Nuclear is not a great complement to PV, if the PV is cheap. Cheap PV expands until there is no residual baseload demand left. At that point, nuclear power plants cannot maintain high capacity factor and their economics go all to hell.

PV for baseload? How does that work? Everyone will use candles at night?

> PV for baseload?

It's remarkable you were able to read that into what I wrote, when that wasn't at all what I wrote.

The point I was making was that intermittent renewables can screw up the market for nuclear, even if the renewables themselves do not supply baseload.

You may be under the misapprehension that if there is a base level of demand on the grid, then that base level of demand can only be supplied by baseload power sources like nuclear or coal. This is not the case. It was in the case in the past that baseload sources were the cheapest way to satisfy that demand, but there's no law of physics or economics that requires that to always be true. And increasingly it's NOT true.

Re: Molten Salt Reactors

#96
post #16

Earlier quoted context omitted.

> Efficiency really matters when we have >1000 GW of installed nuclear capacity. If all energy is obtained from nuclear, (12000-16000 GW) even seawater uranium get used up in 40-60 years with inefficient solid-fuel reactors. That can't be right. About 200 tonnes of natural uranium is needed to produce 1 GWe per year in conventional reactors [1]. That's 3,200,000 tonnes per year if you mean 16000 GW in the form of ele…

Firstly heat from inefficient low temperature solid-fuel reactors can't be used directly for many applications. So consider electricity. Cars/planes/kitchen-stoves cant use uranium or nuclear heat!! All 4.5 billion tons can't be extratcted. More we extract, concentration decreases and harder it gets. I keep asking this question: If seawater extraction of metals is practical, why aren't we extracting other costly meta…

The most optimistic cost projection I can easily find for seawater uranium extraction goes as low as $360 per kilogram of uranium.

https://inis.iaea.org/collection/NCLCollectionStore/_Public/...

If extracting gold is only 300 times harder, that puts the lower bound cost at $108,000 per kilogram of gold. That's significantly more expensive than the market price of gold.

Indeed, extracting uranium itself from seawater is not cost competitive with conventional terrestrial mining at present. But the process has been demonstrated on a technical level. Either terrestrial uranium deposits will have to get closer to exhaustion or seawater extraction will have to be much more cost optimized (or both) before seawater extraction of uranium is economically competitive. I was only addressing your technical claims about the exhaustion of seawater uranium, not making economic claims.

Re: Molten Salt Reactors

#97
post #90

The elephant in the room with any kind of fission reactor is that they are going to need a lot of security. Even when the fuel and waste product is not weapons grade uranium, it's still highly radioactive and a great source of material for a dirty bomb. Basically anything that goes boom combined with small amounts of radioactive material and a bit of wind is a great way to depopulate e.g. large cities. So, having lot…

(Molten salt reactor is a fluid fuel reactor. Fluid: liquid, gas and plasma.) Molten salt reactor is a stepping stone for fusion reactors. We need to master liquid and gaseous reactors before going plasma. Our civilization should aim for larger goals. We need some form of nuclear power to terraform other planets and spread earth's precious life and conciousness everywhere.

We do not need nuclear for any of that.

Re: Molten Salt Reactors

#98
post #81

Earlier quoted context omitted.

Up here the yearly sunshine is pretty good, close to Germany or so. The problem is that almost all of it comes during the summer. In the winter months when demand peaks, solar produces practically nothing. So without seasonal storage becoming economical, it's not a solution to decarbonizing. Closer to the equator where seasonal variation is less and demand is driven more by air conditioning than heating solar is an e…

Closer than 51 North? you mean like all of the continental US?

95% of the global population lives at latitude less than 50 degrees.

Re: Molten Salt Reactors

#99
post #91

Earlier quoted context omitted.

The problem with that argument is that it proves too much. It applies to everything, because solar and wind are the same as nuclear, their incremental generation cost is effectively zero once the capital is paid, so you take whatever the market price is. Which means you have a problem. It's physically possible to build enough solar and wind and storage to even handle extended periods of low sun and low wind. But if y…

Solar and wind will build out until it is no longer profitable to do so. That means: when they have driven the price of electricity when they are operating, averaged over time, down to the point they can't get a return on investment. This price point is far below where new nuclear needs it to be for nuclear to earn back its construction and operating costs. What drives all this is that the levelized cost of energy fr…

> Solar and wind will build out until it is no longer profitable to do so. That means: when they have driven the price of electricity when they are operating, averaged over time, down to the point they can't get a return on investment.

It seems like you're expecting this to be a slope rather than a cliff.

The problem with generation methods with no incremental generation cost is that absent some coordination/collusion, you go straight from a price somewhere above breakeven to basically zero as soon as you have any significant amount of oversupply, because everybody would rather get something than nothing.

So even if the average wholesale price is currently above 2c/kWh and you can bring capacity online that generates at 2c/kWh, you won't, because the act of doing it would create oversupply, cause the average market price to fall to below 2c, and you and everybody else would lose their shirts.

It's basically a market that bankrupts everybody without some coordination, but part of the value of that coordination includes preferring some amount of stable generation capacity to avoid the high cost of supply emergencies when low supply from the unstable generation methods coincide with each other.

> What drives all this is that the levelized cost of energy from solar and wind is much less (a factor of 3 or 4) less than the levelized cost of energy from new nuclear plants.

This isn't accounting for variable supply and demand. The price it costs to generate in the summer sun isn't the real price when the unmet demand is in the winter night, and it isn't going to be economical to shift the demand by six months using energy storage. But if you had enough solar to provide heat in cold climates in winter you would have so much oversupply the rest of the year that you wouldn't make a cent for nine months out of twelve.

> Nuclear has an additional disadvantage: it cannot cut output rapidly. If renewables suddenly flood the market, prices can go negative. Renewables can just stop selling in that situation, but nuclear is forced to continued to run and eat the negative revenue.

If that actually started happening on a regular basis there would be obvious solutions like resistive heaters or on-site energy storage which can be charged during those periods and then sold for a profit when prices are higher. (Thermal storage could work really well considering the reactor generates heat to begin with and they already have existing heat-to-electricity systems on site.)

And that's assuming all of this "smart grid" stuff doesn't ultimately succeed in preventing that from happening by increasing consumption as prices fall so that they don't actually go negative to begin with.

> What will be the final death knell for nuclear will be when short term storage gets cheap enough that the times when that's discharging will also be economic death zones for nuclear plants.

It's only speculation that this will actually happen. And even now people like to use overly optimistic numbers. Storage costs a certain amount if you charge it up every day and then discharge it again every night, but if you want the storage to be able to handle generation undersupply over a period of a week or more, you need a lot more of it which will generally go idle, which requires you to charge higher average prices per kWh.

> I expect few of the existing operating nuclear power plants to survive after that.

The existing nuclear power plants will keep going as long as the market price is above the operating cost. The capital costs are sunk.

Re: Molten Salt Reactors

#100
post #69

Earlier quoted context omitted.

What's hydrogen supposed to add? It's just a type of storage, and probably not even the cheapest one.

Hydrogen has low capital cost. The capital cost/energy of storing hydrogen underground will be much less than the cost of storing that energy in a battery. If you have a storage scenario where the energy is stored for very long times, there will be few cycles of that system over its economic lifespan, so minimizing capital cost (even if that means much lower round trip efficiency) is very important. One would still u…

> In particular, simple cycle gas turbine power plants with efficiency of 40% cost maybe $400/kW. Compare this to $8-10K/kW for a new nuclear power plant.

The problem being that it only operates ~2% of the time compared to ~100%, and has a shorter operating lifetime in practice, and that isn't counting the cost of storing the hydrogen nor the energy cost to produce it.

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