The problem with molten salt based reactors is that the high temperature radioactive molten salts destroy their containment vessels. I've yet to see a system design where the salt facing components are expected to last more that 7-10 years, which really hurts profitability.

There are two problems.

One is corrosion/radiation damage to the reactor vessel which is probably made with something like

http://www.haynesintl.com/alloys/alloy-portfolio_/Corrosion-...

The other is that most of these designs have a graphite moderator, and the graphite gets damaged in the reactor environment.

I would consider graphite moderators under the umbrella of salt facing components.

High Ni alloys such as Hast-N have their own issues - mainly radiation induced Ni -> He embrittlement and tellurium embrittlement. That being said, they are very promising.

Yes, the reactor cores would have to be replaced every 12-15 years. But if the reactors are mass produced and designed to swap out the cores, it doesn't have to be too expensive.

Still not "sustainable".

And not really cheap either.

It is actually quite sustainable. The reactor core is not a large cost for a GW over 15 years.

The US navy swaps out reactor cores for 100-200 million dollars, and those are in submarines and ships. There is basically no maintenance outside of those.

For comparison, a GW of wind capacity is 1.6 billion every 20 years. For solar panels for 1GW of average generation you'll be paying 10 billion dollars or so every 25-30 years.

> For solar panels for 1GW of average generation you'll be paying 10 billion dollars or so every 25-30 years.

Where do you live that panels cost you $1.5+/Wp?

Furthermore, where do you live that panels will cost you $1.5+/Wp even thirty years from now?

You have to multiply the cost by three for average power to account for clouds, angle, night time, and then you need to pay extra for storage. That will cost you...

I think GP meant environmentally sustainable, rather than fiscally sustainable, you need to do something with the old reactor cores.

That's sustainable long past the point we run out of radioactives. Just how much space do you think buried reactor cores take up and how big do you think the earth's crust is?

You could literally throw it in the deep ocean and it'd still do less damage than a single day of Brazilian deforestation for biofuel production or a month of operation of a coal plant (partially because water is actually quite good at blocking radiation and not becoming radioactive, you can safely swim in a spent fuel rod storage pool).

I’m not fundamentally against the idea of nuclear power. I just remain unconvinced that we’ve “solved” the problem of nuclear waste.

Nuclear waste remains dangerous and harmful on a timescale that can almost be described as tectonic. The earths crust isn’t static or stationary, if you throw waste into the bottom of the ocean its not clear what will happen to that waste in 10 millions years time, or even 300 years time.

I agree that our current climate situation demands drastic actions, and theres a strong argument that solving the real harms today of climate change are worth taking the risk on the theoretical harms of nuclear power. But I don’t agree that nuclear power is currently “sustainable”, it’s almost certainly the best energy source we have today, but that doesn’t necessarily mean it will stay that way for long.

I would advise checking the decay curves for nuclear waste and checking what levels of radiation cause harm.

The tldr is that waste that decays slowly is doing so because its releasing less radiation. There's no radioactive stuff that we'd need to worry about on the million year timescale. The 10000 year timescale is the most where human health due to radioactivity might be a concern. And on those timescales your waste at the bottom of the ocean or 100ft below ground is almost certainly going to be still there and unaffected unless we or our successors decide otherwise.

Heck I'd say worrying about anything more than the 500 year timescale is absurd as I'd be very surprised if humans were still around in human form by then. We'll either have been genetically engineered, wiped out by those who have, wiped out by rogue AI or something else or been "uploaded" in some fashion.

What does a coal plant do with the emitted radiation, CO2, coal ash, and other waste products? Current spent fuel rods from nuclear reactors sit in concrete casks located on site usually. At least I don't need to breath spent nuclear fuel or have to deal with it's CO2. Not saying we should do nothing about it, but at least the impact to my life today is substantially less.

The reactor core will probably be drained of molten salts and then treated as low level radioactive waste.

Yes it is waste, but I don't see anyone making the argument with wind turbines or solar panels, which will create more waste in total.

> you need to do something with the old reactor cores.

You burry it deep in a geologically stable ground [1]. Was that not counted in the price?

[1] https://en.m.wikipedia.org/wiki/Deep_geological_repository

The core will be radioactive for hundreds of thousands of years will it not?

Which is nowhere near as big a deal as it sounds. The damage it will do (on average) if glassed and buried 100ft under ground is absolutely negligible at the scale we are talking about (global climate change and energy in general).

Yes, there's a 1 in 10000000 chance that 2000 years from now industrial age humans recovering from the apocalypse might dig a well in exactly that location and thousands will get sick with hundreds of deaths. You could multiply that by a hundred thousand cores and it would still be negligible compared to the hundreds of millions likely to die due to climate change in the next century

I really liked how you framed the danger.

But what about if we had a Reactor Dump storing 100's of these reactors, and then something happened to that dump, either it was hit by a meter or it was intentionally attacked in some way. Could that result in an apocalyptical type event?

No, it couldn't.

It would basically be a few Chernobyls in the worst case (a 1 in 1000 year asteroid impact winning the 1 in 100 million lottery and hitting the dump) and that mostly means extra birth defects and cancer (you wouldn't want to live somewhere that gave you a 10% chance if dying due to cancer age 40, but you could still have a civilization in such a location). It doesn't end life in the impacted area.

For intentional attacks there are much much easier ways of killing a lot of people.

So you have a large dump that must remain secure for 200k years.

You cannot do that. There is no place on Earth that we can be sure is geologically stable over that time period.

What a selfish thing to do: Make future generations pay for our current consumption for millennia.

Molten salt reactor waste should have a dramatically shorter half-life than waste from a light water reactor. MSR waste only needs a few hundred years of containment, not hundreds of thousands of years.

Explain that.

Makes no sense to me, but my physics education was decades ago

Well I'm not a physicist, so take everything I say with a grain of (molten) salt, but it has to do with the kind of fuel used, which produces different waste products.

The half life of most of the waste product from a gen-3 uranium reactor is measured in millions of years (235U's half life is ~700 million years, for example).

In some gen-4 molten salt reactor designs, most of the waste product would have a half life measured in hours, so they wouldn't need to be put into long-term containment at all. And the rest of the waste products would only require a few hundred years before they are emitting only background level radiation.

Hopefully someone with actual education on this can give a more complete answer, but that's my Reader's Digest understanding.

The molten salt will be quite radioactive, yes. It is part of the radioactive waste generated by a molten salt reactor. Some types of molten salt reactors do not have this problem, but I don't think they are the most practical.

The metal containing the molten salts might become somewhat radioactive too.

All in all, this is still comparable in amount of waste to water cooled reactors.

What happens to the used cores?

They have to be disposed of. That creates waste. This is the same as with any other power generation method that exceeds it's lifespan. 15 years is not that different from 20 years for a wind turbine or 30 years for a solar panel.

Solar panels are lasting about 10-15 years in practice. About half of what was expected.

I call BS on that. This was the performance of ancient modules (early 1980s) after 25 years of operation: https://energiforskmedia.blob.core.windows.net/media/19320/p...

And this was for modules manufactured in a period with 5-10 year warranties for the product. Today you get 25 year warranties. So you're basically claiming that QA massively worsened in the meantime.

Thorium reactors produce isotopes that can be converted into U238, which is less desirable than U235 for weapons purposes, but can be converted into a usable if annoying and expensive to manage bomb due to its high gamma production.

https://www.foe.org.au/anti-nuclear/issues/nfc/power-weapons...