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Molten Salt Reactors

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Re: Molten Salt Reactors

#111

Post by wolfram74 »

pfdietz wrote: post #97
achalhp wrote: post #90

Earlier quoted context omitted.

(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.

Well, given how solar has an inverse square relation between watts/area and distance from the sun, by the time you get to mars, solar is getting pretty piddly, the asteroid belts and jovian moons its downright comical.

Re: Molten Salt Reactors

#112

Post by jillesvangurp »

Mirioron wrote: post #107
jillesvangurp wrote: post #62

Earlier quoted context omitted.

> Aren't roof solar panels very inefficient? They are good enough. Low efficiency just means we have to buy more of them. Obviously we'd need solar plants (and maybe wind parks and other clean sources) to also power those with limited access to roof surface. Of course, bad weather doesn't mean solar stops working; it just reduces the output. The effect is typically very local as well. So, all that means is that you n…

Bad weather in northern Europe means that everything is covered in snow for a long time. I think that's slightly more than just reduced output. The snow also tends to cover am area that's hundreds of kilometers in every direction too.

I've lived in Sweden and Finland. It's actually the lack of sunlight that is causing issues with solar. The snow is much less of a concern. E.g. Helsinki only gets a few hours of daylight and the sun does not get much above the horizon in the winter months. The reverse is true as well; you get insane amounts of sunlight in the summer months. Luckily there's wind, hydro, wood pellets, and a few other alternatives.

Further south in Germany, Netherlands, etc. Solar is usable throughout the year and quite common. Obviously output in the summer is going to be much better than during the winter.

Re: Molten Salt Reactors

#113

Post by jillesvangurp »

javier2 wrote: post #88
jillesvangurp wrote: post #32

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…

You can't run an electrical grid on wind and solar alone and expect it to be stable enough. - The prospect of every household having a battery backup big enough to smooth over spikes and dips is ludicrously wasteful. We are already struggling just mining enough to make batteries for cars and phones. - the sheer scale of the wind and solar farms will leave major environmental impact to wildlife. Look at how massive ar…

Nope, simply untrue. Cars use lithium ion batteries mainly for their energy density. For grid storage, other batteries and ways of storing energy are feasible and probably a lot cheaper as well. Wikipedia has a nice overview: https://en.wikipedia.org/wiki/Grid_energy_storage#Grid-orien...

The wild life impact of solar is relatively minor compared to burning coal, intensive farming, and all the other things we do. We'd need to only cover a relatively small amount of land with solar to produce what we need. And ironically some of the most suitable land for this would be deserts that have relatively little wild life to begin with. Of course the impact of wiping out coal, gas, and petrol usage would be enormously positive.

Windmills do indeed kill some birds. Yet, these things seem to have barely any impact on e.g. the seagull populations in places like Denmark that have a ridiculous amount of wind mills.

Re: Molten Salt Reactors

#114

Post by achalhp »

philipkglass wrote: post #96
achalhp wrote: post #16

Earlier quoted context omitted.

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…

You included my sentence: "Efficiency really matters when we have >1000 GW of installed nuclear capacity." I wanted to address that: efficiency matters.

Inefficient technologies will hit some constraints if not others.

We may run out of time: A pressure vessel production cycle is over one year[1]. By the time we reach >1000GW someone may make fusion practical or China's competent nuclear industry may start selling MSRs to everyone.

We may run out of highly skilled people required to build and operate these complex machines. The safety is highly dependent on operations and management throughout the life cycle of complex machines. From manufacturing to operations there is tiny margins for error. (Not a physical constraint.)

LWR technology is associated with military ships and submarines, no one shares it. Few countries control the technology and there are only a few places in the world to make pressure vessels. (Not a physical constraint.)

We may run out of waste disposal sites. A geological repository needs special rock formations away from earthquake zones.

The article is written by a nuclear industry professional who tells that routine things done by the nuclear industry today when applied to MSR is a "disadvantage". They open the lid of an LWR every 18 months and replace/shuffle highly radioactive fuel assemblies and say that it is a disadvantage for them to replace graphite. That is totally unfair.

[1] VVER pressure vessel production cycle needs 3 years. https://www.youtube.com/watch?v=91yVhrSZ5jQ

NuScale pressure vessel R&D: https://www.energy.gov/sites/prod/files/2016/10/f34/02%20-%2...

TL;DR Even small pressure vessels (used by nuscale) have lead times of about a year. A megafactory can build like 1 or 2 vessel per month. At 1.5GW/year/factory, we need like 22 factories to keep up with the production schedule if we need to reach 1000 GW of small-LWR capacity within, say 2050.

Re: Molten Salt Reactors

#115

Post by pfdietz »

Mirioron wrote: post #108
pfdietz wrote: post #98

Earlier quoted context omitted.

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

A large chunk of Europe sits north of that though.

I have a strong suspicion that a good chunk of the opposition to solar is good old fashioned white racism. Can't have an energy source win that benefits the brown skinned parts of the world, this thinking goes.

Re: Molten Salt Reactors

#116

Post by pfdietz »

wolfram74 wrote: post #111
pfdietz wrote: post #97

Earlier quoted context omitted.

We do not need nuclear for any of that.

Well, given how solar has an inverse square relation between watts/area and distance from the sun, by the time you get to mars, solar is getting pretty piddly, the asteroid belts and jovian moons its downright comical.

Actually, solar still has huge advantages at the distance of Mars.

In space (actual space, not a planetary surface), it's difficult for nuclear to dissipate its prodigious amounts of waste heat. Solar, in contrast, can be made much lighter than on Earth, as there isn't wind and rain to deal with. And of course in general the Sun is available 100% of the time in space, further improving the economics.

But in any case, the argument wasn't that solar was necessarily better, it was that nuclear wasn't necessary. Solar can provide energy basically anywhere, with power beaming, even out into interstellar space.

Re: Molten Salt Reactors

#117

Post by pfdietz »

AnthonyMouse wrote: post #103
pfdietz wrote: post #101

Earlier quoted context omitted.

Yes, the power will be expensive during that 2%. But it will not contribute all that much to the total cost of operating the grid. In particular, it would be cheaper than forcing the consumers to pay for nuclear the other 98% of the time, just so it would be available during that 2%.

If it's dozens of times more expensive during that 2% because it has to recover 100% of its cost in 2% of the time then it does contribute quite a bit to the total cost of operating the grid, whereas nuclear only has to make up the difference in that time between the market price the rest of the time and its overall average cost. Storage also has the further disadvantage that you have to over-spec it. It has to be bu…

Simple cycle gas turbines are 20 times cheaper than nuclear power plants of equal power output. So, no, your argument doesn't hold up when the actual numbers are examined.

Re: Molten Salt Reactors

#118

Post by pfdietz »

paulsutter wrote: post #102
pfdietz wrote: post #95

Earlier quoted context omitted.

> 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 basel…

Right but only because you’re ignoring storage which is the only way to make PV really work (duck curve is an absurdity caused by lack of storage). Sorry I missed your point, but your still misunderstanding what’s needed.

Renewables can ruin the market for nuclear even without storage. Adding economical short term storage (we're close with batteries, and almost certainly will have it before any nuclear plant whose construction was green-lit today could be completed) and nuclear is not just in trouble, it is dead.

Re: Molten Salt Reactors

#119

Post by achalhp »

pfdietz wrote: post #116
wolfram74 wrote: post #111

Earlier quoted context omitted.

Well, given how solar has an inverse square relation between watts/area and distance from the sun, by the time you get to mars, solar is getting pretty piddly, the asteroid belts and jovian moons its downright comical.

Actually, solar still has huge advantages at the distance of Mars. In space (actual space, not a planetary surface), it's difficult for nuclear to dissipate its prodigious amounts of waste heat. Solar, in contrast, can be made much lighter than on Earth, as there isn't wind and rain to deal with. And of course in general the Sun is available 100% of the time in space, further improving the economics. But in any case,…

Planets rotate so backup power is needed during nights. Spacecraft has to avoid obstracles and has to move, so backup is needed. During interstallar journey there is time delay in communication, so it may take hours to adjust the power beam when spacecraft moves a little bit. Fusion is like solar energy just near to us and MSR will be eventually replaced by fusion reactors.

MSR and many other fluid-fuel reactors run hot and it makes radiators small: https://www.flickr.com/photos/oakridgelab/31537153147/

Stefan–Boltzmann law: Radiation heat transfer is proportional to 4th power of temperature.

Re: Molten Salt Reactors

#120

Post by pfdietz »

achalhp wrote: post #119
pfdietz wrote: post #116

Earlier quoted context omitted.

Actually, solar still has huge advantages at the distance of Mars. In space (actual space, not a planetary surface), it's difficult for nuclear to dissipate its prodigious amounts of waste heat. Solar, in contrast, can be made much lighter than on Earth, as there isn't wind and rain to deal with. And of course in general the Sun is available 100% of the time in space, further improving the economics. But in any case,…

Planets rotate so backup power is needed during nights. Spacecraft has to avoid obstracles and has to move, so backup is needed. During interstallar journey there is time delay in communication, so it may take hours to adjust the power beam when spacecraft moves a little bit. Fusion is like solar energy just near to us and MSR will be eventually replaced by fusion reactors. MSR and many other fluid-fuel reactors run…

> Planets rotate so backup power is needed during nights.

This does not rule out use of solar energy.

> During interstallar journey there is time delay in communication, so it may take hours to adjust the power beam when spacecraft moves a little bit

The vehicle tracks the beam, not vice versa.

> Fusion is like solar energy just near to us and MSR will be eventually replaced by fusion reactors.

Fusion is ridiculous when examined closely. It's like fission, only far worse from an engineering and cost perspective.

> Stefan–Boltzmann law: Radiation heat transfer is proportional to 4th power of temperature.

Which means waste heat from a reactor in space has to be radiated at higher temperature than for a reactor here on Earth, which means nuclear is worse off there than here. In contrast, solar works better in space, as I argued upthread.

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