Hacker News Reader

Comment by pjc50 | Hacker News Reader

"We could do it for $1 Trillion with liquid-fueled Molten Salt Reactors, on the same amount of land, but with no water cooling, no risk of meltdowns, and the ability to use our stockpiles of nuclear “waste” as a secondary fuel."

This is not a production-ready technology, though. I believe there are lingering problems with corrosion. And the claim that the MSR doesn't require secondary water cooling is odd: what's the turbine working fluid heat dump supposed to be?

I really object to phrasing energy policy as either/or. Build out renewables, now, because that's ready. Let's give the MSR a fair go at getting to production-ready, see if the problems can be worked out.

Let's not build a nuclear plant whose output is subsidized to twice the normal wholesale cost: http://www.bbc.co.uk/news/business-22772441

View on HN

Yeah, there are a lot of alternate nuclear reactor designs that look great on paper but have never had the full scale engineering done to see if it is practical. And they look cheap because you don't even know half of the stuff you have to do that makes it expensive.

It's like rocket design where you go "just put a bunch of explosives in a tube and go into space, this shouldn't be too expensive or difficult..."

True; many of these dream reactors probably won't work, because that is the nature of things. But the full-scale engineering never gets done because of anti-nuclear propaganda playing on mass public ignorance, so at the rate we're going now we'll never know.

Full scale engineering, free of the liberal treehugging you decry, happens in China, India, Russia, and elsewhere. You'd think we'd be seeing better results than we are.

Well, at least Kudankulam Nuclear Power Plant was being delayed due to protests by local people. Another reason why better results are not being obtained is because of the subsidy on CO2 emitting fuels by not taxing the externalities (which would make nuclear power significantly more profitable) and also difficulties in obtaining nuclear material (NSG, for example). Kudankulam power plant generates power at 4.29 rupees/kW.h which is barely profitable compared to other methods (mostly fossil fuels).

China literally just got started and betting pretty big too so hell yeah we're going to see results in the next 10 years.

If there's positive buzz about molten salt reactors, the most likely source of that buzz is people who want to get rich selling molten salt reactors.

Yup. Rocket science is dead easy. Tsiolkovsky, and... that's about it. Rocket engineering, on the other hand...

This is where John D Clark's book "Ignition!" really shines: it's the history of the science of rocket fuel as problem solving. Plenty of candidates on paper, need to be tested for detonation, hypergolicity, ease of ignition, handling, effect on plumbing etc. Red fuming nitric acid is a good example: great oxidiser, doesn't need cryogenics but is liquid even in arctic temperatures. Only problem is it eats through the tanks, until they discovered that adding a small quantity of HF made it OK to store in stainless steel.

I suspect that he would have taken one look at handling radioactive corrosive liquid at 600C and asked to go back to the nice safe rocket lab with only a few explosions.

I've seen Ignition! referenced quite a few times on this site. Is there a reasonable place to get a reprint?

Googling for [john clark ignition] yielded http://fringe.davesource.com/Fringe/Explosives/Ignition.An-I... (also on archive.org)

It's available online: http://library.sciencemadness.org/library/books/ignition.pdf

Thank you, went to save it to my dropbox and found a copy already there...

Corrosion is not a problem. But there is still a ton of work that needs to be done with molten salt reactors. But it's work we should do, I feel. I used to be skeptical of the idea but after doing a considerable amount of research I changed my opinion, the core design has a myriad of advantages and it's practically criminal we aren't dumping gobs of money into research for it.

As for water, the working fluid of the heat exchanger and generator can be water, though Helium or CO2 would make more sense.

Additionally, renewables are absolutely not ready to take over base load power generation. They are an incredibly flawed system in their current form, and incredibly expensive (in multiple ways). They can be improved but it'll be a long, long way before we can rely on solar and wind as the core (rather than periphery) of our power generation infrastructure.

Wait wait wait, you're going to have to provide a citation for this claim that corrosion is not a problem.

I was told by faculty with joint appointments in matsci and nuclear engineering that it is a major issue and that while they've developed some alloys that look reasonable in the recent past it's still academic research unproven in scale up.

Holding molten salts is really hard... they corrode the heck out of even high end commodity stainless steels (this I know from professional work). Protective coatings help for sure, but they crack over time, especially with any thermal cycling. Inconel and similar alloys maybe, but it's really not straightforward to block grain boundary corrosion! Add to that neutron embrittlement...

I've not kept super up to date, but it's hard to imagine that these alloys went from academically unproven to industrially certified in the last seven years.

Hastelloy-N, it's expensive stuff but it works. Corrosion is one of the difficulties of molten salt reactor designs, but it's manageable with the right materials. And the tradeoff is that you don't need an enormous high-strength containment vessel (because everything radiological is at 1 atm), you don't need to pump water into the thing constantly to avoid "really bad things" happening (Fukushima), etc, etc.

Exactly this.

Specifically you should read the findings of the MSRE (Molten Salt Reactor Experiment) at ORNL.

Wikipedia has a relatively laymans explanation of the state of the Hastelloy-N when the experiment concluded.[1]

It's worth mentioning Hastelloy-N isn't that expensive all things considered. It would probably come out to a small percentage of the reactors total cost factoring in R&D expenditure etc.

[1] https://en.wikipedia.org/wiki/Molten-Salt_Reactor_Experiment...

Additionally, while using a lot of Hastelloy-N would be expensive, in the context of a full reactor it's a modest expense. Especially when you compare it against the extremely enormous forgings and gigantic reinforced concrete structures that traditional lightwater reactors use. Overall you end up with a much smaller and much safer reactor. And one that can burn existing high-level transuranic waste as well. It's such a huge win it's criminal we're not spending billions in R&D right now.

Well, thanks for the citation. I'm now much more confused about why this is what I was told in class by an expert in the field. Maybe he meant specifically the difficulty of finding a steel up to the challenge, it was a decade ago so some fidelity may have been lost!

I know not much about material science, except for some very painful experiences in an industrial setting+. But I have a feeling people tend to think fluoride salts are going to be as docile when molten and exposed to a high radiation flux as they are as room temperature solids.

+ Ethylene-oxide gas + moisture + heat -> plying rough trade on supposedly compatible materials.

Not my problem but a customer I worked with had a gamma ray sterilization unit. There were some limit switches which they needed to replace after ten years. Replacements, same part number, manufacture swore up and down they were identical, would crack after three to six months.

Oak Ridge ran an MSR for four years without difficulty. One solution is to just do that, rather than trying to make a reactor last 60 years.

At least two startups are going that route. ThorCon's design is a plant with reactor cores as replaceable "cans," each lasting four years in production plus four years of cool-down before shipping to a reprocessing facility. Terrestrial Energy has sealed 7-year units.

china is betting big on liquid fluoride thorium reactors. http://blogs.telegraph.co.uk/finance/ambroseevans-pritchard/...

China’s thorium project was launched as a high priority by princeling Jiang Mianheng, son of former leader Jiang Zemin. He estimates that China has enough thorium to power its electricity needs for “20,000 years”. The project began with a start-up budget of $350m and the recruitment of 140 PhD scientists at the Shanghai Institute of Nuclear and Applied Physics. It then had plans to reach 750 staff by 2015, but this already looks far too conservative.

http://blogforarizona.net/could-thorium-reactors-provide-the...

Paradoxically, though, given thorium’s history, it is the difficulty of weaponising thorium which many see (as it were) as its killer app in civil power stations. One or two 233U bombs were tested in the Nevada desert during the 1950s and, perhaps ominously, another was detonated by India in the late 1990s. But if the American experience is anything to go by, such bombs are temperamental and susceptible to premature detonation because the intense gamma radiation 233U produces fries the triggering circuitry and makes handling the weapons hazardous. The American effort was abandoned after the Nevada tests.

https://illumin.usc.edu/assets/media/1067/thorium_reactor04....

I think the main idea behind thorium safety is that the radioactive material can be removed without shutting down the plant, which is not possible with Uranium rods.

Molten sodium was at the heart of the Santa Susana nuclear disaster in southern California, which was covered up for fifty years. Needless to say, I'm skeptical.

Vaporized sodium is at the heart of nearly every streetlight. They're not causing disasters. Just having the same material doesn't make the safety the same.

Yes, also it's been fifty years, so I'm sure tech has advanced. I didn't say I wouldn't consider it, just that skepticism is warranted, due to frequent lying about risk.

There's a big difference between sodium, which reacts vigorously with water and air, and salt, which you have on your dinner table.

Santa Susana was a sodium-cooled reactor, but a "molten salt reactor" uses salt. It's chemically inert and doesn't require pressurization.

Reply on news.ycombinator.com