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A Thorium-Salt Reactor Has Fired Up for the First Time in Four Decades (thoriumenergyworld.com)
475 points by jseliger on Aug 23, 2017 | hide | past | favorite | 161 comments

Better explanation here (linked from Technology Review): http://www.thoriumenergyworld.com/news/finally-worlds-first-...

More details on the experiment sequence: https://public.ornl.gov/conferences/MSR2016/docs/Presentatio...

This is not actually a reactor test because the thorium-bearing salt does not attain criticality. It's a sequence of materials tests using thorium-containing salt mixtures in small crucibles inside the conventionally fueled High Flux Reactor (https://ec.europa.eu/jrc/en/research-facility/high-flux-reac...).

The experiments rely on neutrons from the High Flux Reactor to induce nuclear reactions in the thorium-bearing salt mixtures. However, the experiments will be useful in validating materials behavior for possible future molten salt reactors because it combines realistic thermal, chemical, and radiation stresses.

Comments like this are why I don't bother getting my tech & science news from anywhere but HN.

I've seen an increase in the number of NLP bots that give snippets, but they're far from consistently being accurate. Are there any services that can give you summations like this, kind of like the WSJ's What's News section?

Sometimes, the best summary is "this article is bunk". You won't get that from a bot. The fatal flaws in bad journalism are too often subtle and require careful parsing or outside knowledge to identify.

I think it's easily quantifiable what's a good article. Clear statement at the top that refers to big things, not a storytelling bullshit opening, then the body of the article provides support for that top statement, and later portions are basically just more of the same gradually unfolding sub-articles.

If this structure is lacking, it'll be obvious to sentiment analysis, that there are too much free floating statement, and the article either requires too much outside knowledge (in field expertise), or it's just gossip.

And of course it can be "easily" estimated how novel the statement is, what quality the sources and support are, and so on.

The most important change we could make would be to consistently upvote comments that are explicitly abstracts/tldr's, rather than downvoting them based on the mistaken thinking that this will force people to read the entire article and improve discussion. There is latent desire to supply this service for free if it isn't penalized.

Or people could read the articles. For most topics don't want to bother to have a discussion with someone that only knows what was in the TLDR comment. Maybe it's a little too Aristotelian for your tastes but I think taking the time to read the article is a decent barometer for genuine interest in discussion. If I wanted to read lulzy drive by comments on articles based of what was in a TLDR I would not frequent HN.

See this subthread for some arguments against that.


Why don't you summarize the arguments for me? Too many words for me on that page.

Not worth my time, but I'd upvote someone who did ;)

Coverage isn't great, but these two have managed to get in to my bookmarks:



I seem to recall a similar weekly service for HN but I can't recall the name of it.

http://n-gate.com/ - just kidding!

Maybe http://www.hackernewsletter.com/ but that's an email.

From the n-gate page:

> Pasting n-gate content or generally talking about n-gate on "Hacker" "News" is a violation of the Prime Directive.

In other words, they want to publish their rants, but are unwilling to discuss their views with anyone, not even the very people they are criticizing. This may be a valid (although insane) approach for a blog, but somewhat contradicts their stated goal:

> The purpose of n-gate is to be a remote island of contemptuous sanity in a sea of ridiculous webshit.

Is ngate some kind of let's rain shit on hacker news kind of site? Because it looked like that.

This description is unfair and not correct. They also rant about FOSDEM.

There's one on reddit that does a great job.

Autotldr on Reddit does a very good job

It's not perfect but does the trick 9 out of 10 times, it just uses tfidf irrc.

Ok, we'll change the url to that first link, instead of https://www.technologyreview.com/the-download/608712/a-thori.... Thanks!

Thanks Dang!

I think we're making a serious PR mistake calling these "Thorium Reactors" even though the term is accurate.

"Reactor" evokes "Nuclear Reactor". For many people, "nuclear reactor" is a deeply loaded term. Likewise "Thorium" (and other words that end in "-ium") sounds dangerously like "plutonium" and "uranium".

It doesn't matter how much better/safer this technology is. Don't expect the public to respond positively when we use those words. There's too much knee jerk, "no nukes!" baggage.

We should start calling these "salt power stations" or something else accurate, yet non-threatening. Otherwise, IMHO, it will be a steep uphill battle getting public and legislative support for building these things, regardless of their many benefits.

A bunch of people have tried to rebrand our most energy-dense fuels (uranium and thorium). "Terrestrial Energy" comes to mind. And the unofficial Thorium PR lead, Kirk Sorensen, rebranded the Thorium-Molten Salt Reactor (T-MSR) as the LFTR (Liquid Fluoride Thorium Reactor) because "lifter" sounds better. As an engineer I'm a stickler on accurate naming so this suggestion bothers me, and I think the opposing forces will easily be able to point out that it's just a rebranding of advanced nuclear reactors and hurt proponents' credibility. I wish we could just teach people to weigh risks of things like nuclear reactors versus their real benefits (clean air that has saved 1.8 million people already, 24/7 reliability, tiny land/fuel/waste/transportation footprints, etc.) but on the other hand people are more emotional than not. I'm sure you're right that a sweet new name on a nuclear reactor would be a help.

Honestly I consider focus on Thorium fuel itself to be an attempt to rebrand the much broader but equally capable advanced nuclear industry.

One of the major problems is we were told our current reactors would provide safe and environmentally fuel. The trouble is it's not as clean as most people think.

Mining Uranium ore does have a significant environmental impact. There have been leaks at plants; trace amounts of tritium has been found around breeder reactors like Watts Bar (and TVA has bought up more and more of the land around the area).

The waste, currently held on site at most plants, is another big issue. Engineers will tell you it's depleted and encased in half a meter of concrete that won't break down for tens of thousands of years. Some of these containers are already leaking. There have been several recent controversies recently on the Yukka Mountain facility.

While newer reactors may not have these problems, the fact is there are problems we weren't aware up that cropped up from our traditional Boiling/Pressurized Water Reactors that companies will not fess up to. That's why people are apprehensive.

I don't think that will go away unless someone discovered how to make Low Energy Nuclear Reactions (LENRs) viable .. which would also involve understanding how/why they world, and getting them to work consistently (which no one has).

I'm going to start off saying we NEED Yucca Mountain, BUT you seem to think this stuff is more dangerous than it is. Myself and many others that work with these technologies aren't actually happy about the new John Oliver episode.

> Mining Uranium ore does have a significant environmental impact.

I'm glad you bring that up. To actually understand how much of an impact we need to compare it to things. The human mind isn't good at putting into perspective raw numbers when they are that large, it's just "a lot". When you include the mining of both solar and uranium plants, you actually get around the same total environmental impact. I make this comparison because I've never heard anyone complain about the switch to solar. When we compare to coal mining, fracking, or oil drilling, uranium is tiny. Or even comparing to computers and cell phones.

> The waste, currently held on site at most plants, is another big issue.

I carry a vial of tritium around in my pocket? Why? Because it glows and is a fun conversation. I have no worry about it irradiating my junk because it is a beta emitter that has low penetrating power (~6mm of air). The danger of tritium is soft tissue. So just don't drink it or rub it in your eyes. Granted a leak is more worrisome, but its danger is nowhere near that of the heavy elements. There will always be some waste, but nuclear has done a pretty good job compared to other energy sources because of the fear. Some fear is healthy, especially with this tech. But, again, we NEED Yucca Mountain. There's not much waste, but we should put it in the proper place.

> While newer reactors may not have these problems, the fact is there are problems we weren't aware up that cropped up...

You're discussing concerns about decades old technologies. Remember, that was the same era we were arguing over lead in gasoline, asbestos, and aerosols. Sure, we have problems today, but it isn't the same magnitude. No one in their right mind would shoot a nuclear waste container, or even put it in that small of a container anymore. Things have really changed in the last 50 years, and nuclear tech has been progressing in that time too.

>I don't think that will go away unless someone discovered how to make Low Energy Nuclear Reactions (LENRs) viable

Call it what it is, cold fusion. I'm not going to hold my breath on that one. But ITER and other fusion facilities are showing promising results. But fusion is not just a different ballpark from fission, it is a completely different game (energy and safety).

> concerns about decades old technologies. Remember [...] Things have really changed in the last 50 years

A cautionary tale about this flavor of argument.

I saw a panel of Boston city planners. They complained about still getting grief for the "original sin" (their phrase) of some really bad decision making (like Boston City Hall) in the 1960's and 70's. It was half a century ago they said. We're not like that anymore they said. They seemed quite miffed about it.

Then they later mentioned Boston's recent Big Dig, and some of its impacts. And the description was surprisingly distorted. Not even a defensive "none of the failure was our fault!", though that was implicit. But more, almost an obliviousness towards causality. And certainly no recognition that their brief description of their field's "no longer relevant" 1960's flaws, seemed to overlap quite a bit with failure postmortems of the Big Dig.

This combination of arguments was remarkably effective in trashing their perceived credibility.

The problem is they need huge subsides to cover the risks, and even then it costs more than other clean alternatives. How much solar/wind + pumped hydro can you buy just from the costs associated with Fukushima Daiichi cleanup / evacuation etc?

Even coal which has long been the cheapest but dirty option is having trouble competing.

> Even coal which has long been the cheapest but dirty option is having trouble competing.

*with $2 Natural Gas

The solar/wind $23/MWh production tax credit is not really something that's easy for anyone to compete with, except natural gas. [1]

You're right that nuclear needs to get its costs down, especially to play in the west. We know it can be done because the French electrified nearly their entire grid with nukes in 10 years for reasonable costs, and the Koreans, bless their hearts, have been building Gen III plants at very reasonable prices. (Alas! their new president is riding an anti-nuclear platform.) With the recent Toshiba/Westinghouse issues regarding the US AP1000 plants, it's pretty unlikely to see any big new nukes anytime soon. But the world moves on and China is building lots of nukes.

Fukushima will be really expensive. Building tornado-hardened designs in tsunami zones does not pay off, so we should not do that. But building appropriately hardened designs is a pretty solid non-emitting solution. Nukes produce 65% of the carbon-free electricity in the USA right now; they're already our climate champions.

[1] https://energy.gov/savings/renewable-electricity-production-...

> Building tornado-hardened designs in tsunami zones does not pay off

The big issues are keeping our construction, engineering, and regulatory agencies active with the subject material and with industry, and allowing saner reactor technologies into commercial use.

Fukishima was not far off from surviving that catastrophe as was. More robust training for emergency response would have avoided them pumping the water the wrong way, and something as simple as raising their backup generator a few meters off the ground would have done the trick.

More vitally, pushing techs into commercial production like thorium-salt reactors (among many others!), would provide failure modes that are INSANELY better than what we get from light water reactors. It's just about the most insane thing to do with radioactive power sources... surround them with something under pressure that violently expands and tries to go right to the atmosphere...

I think the tsunami zones should be fine for reactors, we just need to start with reactor designs that will thrive in failure. Your molten salts turning into rock and keeping themselves contained during a breach or flood, for example, is something that's highly amenable to disaster planning.

All that needed to be done was house the emergency generators in a tsunami-proof building.

Even then, there was time to bring in backup generators, and they were brought - but idiotically the connectors were wrong and they couldn't be connected in time.

I think it is important to understand why Westinghouse went bankrupt though. And that's because they didn't (couldn't) use of the biggest breakthroughs of the 20th century: mass production.

> Nukes produce 65% of the carbon-free electricity in the USA right now; they're already our climate champions.

And this is the reason I fight tooth and nail for it. If we're to meet our emission goals for 2050, we have to build more nuclear. A diversified portfolio of energy sources is key.

Unfortunately regardless of what you wish, people do not weigh the risks. They have knee jerk reactions to terms like 'nuclear reactor'. It's human nature and shouldn't be ignored. Is it more important that it have an accurate name or that it's accepted by the public?

You're not really proposing "acceptance by the public". You're proposing to spin the euphemism treadmill to gain some temporary ignorance by the uninformed. Until some negative event hits the news again and everyone will once again associate them with that.

I think honesty will get you much further. Instead of making bold promises that everyone has heard before ("these are fail-safe", "unsinkable" etc.) just point at the radioactive dust emitted by coal plants instead. Or open pit mining for coal. Or CO2 emissions. Don't claim to be perfect, just better than the competition.

Definitely the latter. I just hope to find other ways to influence people's feelings about things like nuclear reactors. If some epic rebranding is what it takes, then that's great. I feel that it will take more than that.

Any such rebranding would probably last about as long as it takes people to learn that the facilities are built by nuclear contractors, regulated by the NRC, and employing nuclear operators.

More importantly: any such rebranding would ignore how we got into the current predicament to begin with...

Oil, gas, and coal companies have known about climate change for decades, and it represents a threat to untold megabillions worth of profits and business. It is no coincidence they have been pushing anti-nuclear FUD, sponsoring hack research, pushing "green" blogs, NIMBY campaigns, and such for decades. Coordinated, professional, smear campaigns masquerading as environmental issues.

Leaked presentations and marketing materials have shown those companies have triangulated the issue quite simply: They cannot win on facts. They cannot convince everyone to keep fossil fueling it up on the merits of their argument. They can, however, cause enough confusion and knee-jerking to keep the "debate" about climate change open to paralyze political action. They have also pushed pie-in-the-sky green solutions which are superficially satisfying but fundamentally entrench their interests until we're past the point of no return. Push the starting line so far forward that we just have to give up.

That the "environmentalists" on the left have spent 20+ years pushing the strategic interests of Big Coal and Big Oil using their resources and bad science is the result of willful manipulation. That manipulation is a response to the threat of atomic energy and climate change legislation in light of our global infrastructure cycles.

That is to say: if you call fission "grandmas apple pie" it will be a very short time before we're all convinced that grandmas apple pie is dangerous, impractical, too expensive, poorly thought out, not scalable, not feasible, and impossible to do right. Forget what the stats say. Do not look at Ontario. Pretend France is not real. There will be blogs. There will be glossy signs. There will be "grassroots activism", tweet campaigns, and coordinated messaging about Big Grandma and the cancerous properties of Pie. The anti-GMO people will now be anti-grandma, too.

We are playing a game against well-connected oligopolists... We only get to win if we win. They get to win if they win, or if the clock runs out. So guess what the strategy is?

It's all quite baffling, because they could instead of invested some of those megabillions in extending their reach into low-carbon energy sources, embracing the new world and continuing to exist.

The thing is, the reason they have those megabillions and continue to make money is the institutional knowledge they have of how to run a mature business in the industry they're in. Parts of that will translate over to nuclear power or whatever comes next, but for a very significant chunk of it, they're competing with every other business in the new industry, many of which will have a lot less baggage - which is incredibly risky.

Reactor -> plant

It was widely considered a good move to rename "nuclear magnetic resonance" to "magnetic resonance imaging (MRI)" to avoid patient fears. That said, the "nuclear" in that case really was being misinterpreted by the public to refer to fission/fusion, unlike molten salt reactors where the name is being interpreted accurately, at least in a formal sense.

Unfortunately Thorium reactors were/would be full on nuclear reactors with the usual problems that come with those regardless of what you call them. Although the one that was built only operated from 1965-1969, "Sampling in 1994 revealed concentrations of uranium that created a potential for a nuclear criticality accident" and they had to spend many millions sorting that out.

Can you describe what problems these Thorium-burning MSRs have that plague current commercial reactors?

There's kind of a list here https://whatisnuclear.com/reactors/msr.html

"Green coal power systems" keep everyone happy.

The OECD periodically studies trends in public opinion regarding the use of nuclear power. Their most recent study is from 2010, and its conclusions largely refute any cynicism you may hold regarding public understanding of nuclear energy.

From the executive summary:

"In 6 out of 7 of the countries considered, public opinion has been growing more supportive of nuclear energy in the energy mix. The data show that countries where nuclear energy is already present have populations that are generally much more supportive of its use. They also show that these publics are generally better informed and more knowledgeable on nuclear issues and there is a clear positive correlation between knowledge and support."


That was pre Fukushima

Are you suggesting that thorium molten salt reactors get their energy from a source other than nuclear fission?

No. I'm saying that how you name things matters.

One of the ways it matters is that giving something an overly euphemistic name leads people to wonder exactly what it is that you're hiding.

I think nuclear power could follow other products like Nuclear Magnetic Resonance Imaging (NMRI) and just drop the word Nuclear (MRI). How about fission power or fusion power, depending on the source?

Since we're talking about rocks, and heat, I kinda wonder if "geothermal" might be a viable misnomer.

Fusion is fine for now, but "fission" has already been chicken-littled :/

In the earth sciences the term radioactive dating has been replaced with radioisotopic dating. Maybe isotopic power? Or just wait till the generation that grew up with "duck and cover" drills at school to be out of power. Not very long now.

At least this way you convince the educated public that you are credible.

We should avoid names inspired by what amounts to political correctness, because people who see through the names may distrust us further.

However, I do appreciate your point, and I agree that it is a problem. I think the attitude, at least from young white collar professionals, is warming up to nuclear.

Nuclear Magnetic Resonance was the original name for the imaging technique we call MRI. Patients were scared so they changed the name.

For years I've been confused by the two different names. That was an insightful comment.

It's also important to note nuclear refers to the atomic nucleus and not a nuclear reaction.

Nucleus fission/fusion is what constitutes a nuclear reaction, so they in fact refer to exactly same thing involved in entirely different processes. But yeah you'd have to explain it every time it is mentioned.

You might be swayed by facts. But that makes you one of the minority.

A LOT of people make decisions based on emotion. Then they cherry pick the facts (if any) that support the choice, and disregard the facts that oppose.

This is true. However, I think logical people as a group hold a disproportionate amount of power in society. I'm not sure, though, and I'm only arguing out of, well, logic.

What I mean to say is if I were a politician, I would be more concerned with aligning myself with other politicians, scientists, and policy makers, than my constituents in the initial term. Those who are non-technical may be won over later and with other means.

This is why you won't make it as a politician, sadly.

You need initial popular buy-in to be elected, which is why populist policies will always do well.

A couple of comments;

First it is really awesome to see actual research experiments being done on the materials. This is a critical first step in understanding the underlying complexity of the problems and as the article points out it is really helpful to have a regulatory agency that is open to trying new things.

The second is this isn't a 'Thorium-Salt Reactor' it is 'parts that would go into parts that would make up such a reactor if the experiments indicate they will work.' A much less clickbaitey headline but such is 21st century journalism.

The second is very important, there is still a lot of research and engineering to have:

* a (ideally several) functioning research reactor

* an industrial prototype

* and finally a fully functional commercial plant

It's a step in the right direction, but the road is very long.

I am surprised they are using stainless steel instead of Hastelloy-N


The Hastelloy family of super alloys is basically stainless steel without the steel and was proven in the Oak Ridge MSR experiment.

Oak Ridge MSRE found unexpected cracking throughout the reactor anywhere Hastelloy came into contact with the salt fuel. Experiments produced various means of reducing the cracking, but it is not exactly true to characterize this system as "proven."

In 1977 Oak Ridge concluded [1]:

    Controlling the oxidation potential of the salt coupled with the
    presence of chromium ions in the salt appears to be an effective means
    of limiting tellurium embrittlement of Hastelloy N. However, further
    studies are needed to assess the effects of longer exposure times and
    to measure the interaction parameters for chromium and tellurium under
    varying salt oxidation potentials.
We know that without very precise control of the salt fuel chemistry Hastalloy N. will become brittle. It's an open question what happens with longer exposure. And that is where it was left by MSRE.

[1] http://moltensalt.org.s3-website-us-east-1.amazonaws.com/ref...

To be fair, the same is true of the LWR.

They address that right?

> The idea is to stick to standard materials wherever possible and therefore the tubes are made of ordinary stainless steel. The suitability of steel remains to be determined. Corrosion may be a problem, and it is not yet know if it can be controlled by managing the salt chemistry. The high temperatures in MSRs might also be problematic, even if the pressure inside the system is low.


> For SALIENT-02, a different material mixture will be used that contains beryllium, forming a mixture also known as FliBe. Further experiments will focus more on the interaction between the salt and the containment materials. Corrosion resistance is very important for those materials: they should be mechanically strong, and able to resist chemical corrosion and intense radiation. This corrosion resistance will be the next focus of the experiments with tests for 316 stainless steel, Hastelloy, the nickel alloy that ORNL used in the 1960s, and TZM – a titanium/zirconium/molybdenum alloy. Molybdenum has the potential to neutronically be much more attractive but there is no history of testing it at these temperatures.

I suspect it would be comparatively more expensive to build it out of proprietary nickel alloy; especially considering this reactor will not be in service long enough for embrittlement to matter.

Maybe because of the short duration of the tests? Longer term they may use more exotic compounds?

This technology, if viable, could help solve our current nuclear waste problem. Valuable materials could be recycled (by separation) for additional use.



I wasn't expecting to see George Lucas on that video, I kinda got distracted because of him.

This was apparently at the High Flux Reactor in Petten, Netherlands.


India has the most thorium reserves, according to USGS: https://en.wikipedia.org/wiki/Occurrence_of_thorium

And they have had the plans and motivation to build domestic reactors for the past two decades: https://en.wikipedia.org/wiki/India%27s_three-stage_nuclear_...

NSG membership keeps getting held up by someone or the other and would provide more energy security for India.


India's Thorium rich sands are being mined and exported. Not many people are aware though. Hope it isn't too late. Scandals have throttled many efforts to grow indigenous techs. The ridiculous ISRO spy case is one such example. Cui bono?

Cui bono indeed. Corruption benefits. I don't think the spy case affected much of anything.

It did affect our Cryogenic initiatives. Nambi Narayanan was the main brain behind it. It was a setback from scientific point of view for ISRO.


Looking at the wiki, it seems likely that outside forces might've been involved in the scandal.

Thorium is so common that it would be profitable to mine Thorium at nearly any place on earth.

> charged particles traveling faster than the speed of light in water

What did I just read?

Cherenkov Radiation [1]. It's not because the particles are going faster than 300M m/s, but because light in the medium is going less than 300M m/s. The unbreakable "speed of light" is actually, the "speed of light (in a vacuum)". Outside of a vacuum, the light is slowed by the materials it travels through (see prisms, angles of refraction, Snell's Law [2] etc.). But it's still a very special condition when the medium slows light to some large fraction of C, while particles are going faster than that (but still less than C).

[1] https://en.wikipedia.org/wiki/Cherenkov_radiation

[2] https://en.wikipedia.org/wiki/Snell%27s_law

Yup. Whenever you see that blue glow surrounding a reactor core submerged in water, that's the Cherenkov radiation.

If the blue glow happens in your own eyeballs, you've probably just witnessed your own death sentence.

It is dangerous? Nuclear subs have cherenkov radiation outside the hull which implies they have it inside the hull as well, but you don't hear about sailors getting radiation poisoning all the time.

Precedence problem. Read it like this:

(charged particles traveling faster than) (the speed of light in water)

not this:

(charged particles traveling faster than the speed of light) (in water)


The particles are still moving slower than Relativity's limit, the speed of light in a vacuum.

Speed of light in water is slower than speed of light in vacuum

I would have phrased it, "charged particles traveling faster than light through water" or some way that did not include "the speed of light" which people quickly assume to be 1c, rather than .75c (the speed that light travels through water).

That phrase can be parsed in two ways

To the downvoters: This is technically correct.

#1: (charged particles traveling faster than the speed of light) in water

#2: charged particles traveling faster than (the speed of light in water)

Technically, it is technically incorrect. There is no "speed of light", there is only "speed of light in [medium]".*

Therefore, interpretation #1 doesn't make sense.

Maybe colloquially people refer to the speed of light in vacuum as "the speed of light", but again, that is technically incorrect.

*And more technically there's group and phase velocity which may or may not be equal.

This is BS.

Go to 10 physicists and say, "Is c the speed of light?" Odds are that most will say, "Yes." And while some may suggest more exact terminology, not one will fail to understand what you meant.

Furthermore at the subatomic level, light always goes at c. Even if you're in water. It has no other actual speed. Thanks to interactions between light and a medium it looks like photons go slower through the medium. But that's no different than the fact that current traveling through metal acts approximately like it is being carried by electrons of some other mass and velocity. (Or even, in some cases, like the absence of an election. This fact is critical to the operation of a transistor.) But "acts approximately like" and "is" are two different things.

It is technically correct in that there are two parsings (syntax). One of them clearly isn't true (semantics)

But only one of them makes typical sense. Anyone trying to convey the other parsing is expected to clearly disambiguate it.

Agreed, I was just trying to point out what the sentence meant while being friendly :)

So there was a meltdown at a liquid sodium cooled reactor due to a materials problem:


I don't see a pump seal test in this experiment... does anyone know if a solution to the SRE meltdown problem is known at this point? Perhaps the LFT chemistry would not have the issue.

This isn't a sodium cooled reactor, in this case the molten salt is the fuel itself, not the coolant. Plus there is probably no sodium involved but instead a fluoridated nuclear fuel such as thorium or uranium. Also this is a sub-critical experiment so pretty much all they have to do is turn it off if it overheats.

The best part of a molten salt fueled reactor is that in case of heat runaway the fuel would melt plugs and drain into separate containers. Essentially a meltdown would only require replacement of the plugs and refueling of the reactor to make it operational again.

Really happy to finally see some movement with Thorium. It might not be the magic silver bullet that some people hype it up to be, but it needs to be explored.

Glad to see some thorium-bearing salt being irradiated in a conventionally-fueled test reactor. That's a big step to getting back on the road to fluid-fueled reactors.

Here are some reminders for everyone on the technical info about Thorium. First of all, Thorium is found in nature as a single isotope, Th-232, which is fertile like Uranium-238 (not fissile like U-235 or Plutonium-239). This means that you have to irradiate it first (using conventional fuel). Th-232 absorbs a neutron and becomes Protactinium-233, which naturally decays to Uranium-233, a fissile nuclide and good nuclear fuel. This is called breeding. Thorium is unique in that it can breed more fuel than it consumes using slow neutrons, whereas the Uranium-Plutonium breeder cycles require fast neutrons (which in turn require highly radiation-resistant materials, higher fissile inventory, and moderately exotic coolants like sodium metal or high-pressure gas). Any kind of breeder reactor (Th-U or U-Pu) can provide world-scale energy for hundreds of thousands of years using known resources and billions of years using uranium dissolved in seawater (not yet economical).

Great, so Thorium can do thermal breeding, so what? Well to actually breed in slow neutrons, you have to continuously remove neutron-absorbing fission products as they're created (lest they spoil the chain reaction), so you really can only do this with fluid fuel. This leads to an interesting reactor design called the Molten Salt Reactor (MSR). Fun facts about this kind of reactor are that it can run at high temperatures (for process heat/thermal efficiency), can run continuously (high capacity factor), is passively safe (can shut down and cool itself without external power or human intervention in accident scenarios), and doesn't require precision fuel fabrication. Downsides are that the radionuclides (including radioactive volatiles) are not contained in little pins and cans like in solid fueled reactors so you get radiation all over your pumps, your heat exchangers, and your reactor vessel. This is a solvable radiological containment issue (use good seals and double-walled vessels) but is a challenge (the MSRE in the 1960s lost almost half of its iodine; no one knows where it went!!)

U-Pu fuel can work in MSRs as well, getting those nice safety benefits, but it can't breed unless you have fast neutrons.

People on the internet may tell you that Thorium can't be used to make bombs and that it's extremely cheap, etc. These are not necessarily true. You can make bombs with a Th-U fuel cycle (just separate the Pa-233 before it decays), and nuclear system costs are unknown until you build and operate a few. There are reasons to hope it could be cheaper due to simplicity, but there are major additional complexities over traditional plants or other advanced reactors in the chemistry department that add a lot of uncertainty. Fluid fueled reactors are probably ~100x or more safer than traditional water-cooled reactors, on par with sodium-cooled fast reactors and other Gen-IV concepts with passive decay heat removal capabilities.

I was under the impression that thorium-salt reactors have been tried in the past and not deemed "worth" from security and profitability point of view.

What has changed about that ?

They have different problems that pressured water reactors and are not as applicable to applications that the military would like to use them for. So the government sponsored research labs that were running and experimenting with them stopped doing so when research funds ran out.

Add to the insane risk of investing in anything 'nuclear' and you don't have a lot of available capital. That said, the Chinese who invest in research for other reasons seem to have been working on a number of MSRs which could conceivably advance the state of the art significantly.

Oddly enough, as an American, I am looking forward to the first thing that China builds that "we" American's cannot because we lack expertise and/or technology to do so.

>> Oddly enough, as an American, I am looking forward to the first thing that China builds that "we" American's cannot because we lack expertise and/or technology to do so.

Or too much regulation or politics to allow.

Exactly right. The one that came in conversation waiting for the eclipse was genetic editing of fetuses to eliminate inherited disease. Setting aside the whole 'designer babies' as a distraction imagine a company that give free genetic treatment for couples seeking to avoid passing on known bad genes. When you walk that forward and look at the cost associated with treating, diagnosing, and supporting people that later get the disease, you begin to see a huge economic 'win' by giving them free genetic help early.

Why would you expect that treatment to be free?

If the cost of editing is not exorbitant (i.e. is lower than the average per-capita cost of paying for the condition being edited away), healthcare providers would be incentivized to pay for the editing to reduce their costs.

The incentives are obviously stronger in single-payer countries, but even in the US you could imagine an insurance company that competed on lower premiums conditional upon certain gene edits being applied to covered children.

> in the US you could imagine an insurance company that competed on lower premiums conditional upon certain gene edits being applied to covered children.

On one hand, this sounds entirely economically reasonable (and even humanitarian).

On the other hand, I fear this would inevitably produce unintended consequences that would shape our society in distopian, sci-fi/horror-flavored ways.

I have no idea how it would actually shake out. Maybe I'm just being anti-intellectual here.

Given the economics, I feel pretty confident predicting that these edits will be mandatory before most people on this site die.

At least you'd probably have to pay a lot more of the bills if you chose not to have genetic problems corrected before birth.

Expect is perhaps too strong a word, the calculus would be the cost burden of providing services and treating the diseases in the uninsured to the cost of providing the genetic services at the start.

The thing is... Abortion is so much cheaper than gene editing, and it gets all the cells at once. More likely is insurance companies try to deny coverage for people with genetic conditions diagnosed before they were born. While this would not fly in todays environment, it is where the economic incentives point.

> Or too much regulation or politics to allow.

Or, as a German, too much regulation/politics to Get Shit Done.

Just look what happened to Transrapid (maglev rail). All tech and IP went off to China, and we're stuck in 1980-and-earlier carriages for anything not an ICE or regio trains.

> and we're stuck in 1980-and-earlier carriages for anything not an ICE or regio trains.

Actually, the InterCity and EuroCity fleet was just entirely replaced.

This means the entire fleet – S, Region, InterCity, EuroCity, InterCityExpress – is now replaced, or being replaced, with modern stock.

Offtopic but this means I am totally heading back to ride the new trains :-)

Here the new stock:

InterCity/EuroCity: https://www.bahn.de/p/view/service/zug/fahrzeuge/ic_2.shtml

InterCityExpress 4 (to replace major InterCity routes, and minor InterCityExpress routes): http://www.deutschebahn.com/de/bahnwelt/start_ice4/das_proje...

I thought it was the other way around in fact. That they don't produce nuke-weapon-ready material meant that this avenue was not profitable from a security perspective. I may be recalling this incorrectly and I haven't re-checked but I think that's correct?

No, that is incorrect, though it has often been repeated by less technically informed advocates of the thorium fuel cycle. The vast majority of the world's commercial nuclear reactors are light-water-moderated pressurized water reactors or boiling water reactors (PWR and BWR respectively). The actual military origins of these light water reactors is that they were originally researched for submarine and ship propulsion for the US Navy:




The United States and other nuclear weapons states never produced their weapons plutonium from light water reactors. Weapons grade plutonium has typically been produced from uranium in dedicated plutonium-production reactors moderated with heavy water or graphite. (The United States once had a single reactor that also produced commercial electricity along with weapons plutonium, https://en.wikipedia.org/wiki/N-Reactor, but it wasn't a light water reactor either.)

Since uranium fueled light water reactors weren't used to make plutonium for weapons in the first place, the thorium-myth claim that commercial power reactors stuck with uranium so as to make weapons material is ridiculous. The military's early sponsorship of light water reactors for naval propulsion did give uranium-fueled LWRs a significant historical path dependency advantage. I speculate that thorium advocates who continue to repeat the myth about how uranium LWRs became dominant do so because it makes the dominant technology's dominance sound more sinister, hence thorium sound more attractive by contrast.

Oh my god thank you for understanding this and explaining it so well. I spend a lot of time trying to suppress the sinister-LWR myth.

Real reasons MSRs declined include [1]:

* The existing major industrial and utility commitments to the LWR, HTGR, and LMFBR.

* The lack of incentive for industrial investment in supplying fuel cycle services, such as those required for solid fuel reactors.

* The overwhelming manufacturing and operating experience with solid fuel reactors in contrast with the very limited involvement with fluid fueled reactors.

* The less advanced state of MSBR technology and the lack of demonstrated solutions to the major technical problems associated with the MSBR concept.

[1] http://www.energyfromthorium.com/pdf/WASH-1222.pdf

The issue wasn't "light water reactors" it was "uranium fuel cycle". Cheap uranium definitely benefited the US government.

And going back one step Recurecur, isn't a very large part of the the issue "fissionable plutonium" (because bombs) which motivates the "uranium fuel cycle" which means the "thorium fuel cycle" isn't half so interesting.

I'm already a Thorium Patron, proud to be part of this!

"The inside of the Petten test reactor where the thorium salt is being tested is shining due to charged particles traveling faster than the speed of light in water."

What I thought that wasn't possible? Or is this just the speed of light in water, so the particles are still moving slower than the speed of light in a vacuum?

> What I thought that wasn't possible? Or is this just the speed of light in water, so the particles are still moving slower than the speed of light in a vacuum?

Good question! It's the latter - the shining is due to Cherenkov radiation [0], "electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity of light in that medium."

[0] https://en.wikipedia.org/wiki/Cherenkov_radiation

Glad to see they are resuming research even though there remain problems with it as a commercial technology.

even though there remain problems with it as a commercial technology

Such as...?

There are quite a few issues which this site goes into quite well https://whatisnuclear.com/articles/thorium.html

Basically you can make reactors using it but it would probably work out more expensive than conventional ones.

What's up with this image caption?

"The inside of the Petten test reactor where the thorium salt is being tested is shining due to charged particles traveling faster than the speed of light in water."

As I understand it, nothing travels faster than the speed of light. The author is mistaken, right?

Nothing travels faster than the speed of light through vacuum.

But the index of refraction of water is 1.33 . So the speed of light through water is much slower than through vacuum. And electrons can travel through water faster than light through water.

The effect is similar to a massive object traveling faster than the speed of sound through air.


Edit: I love that HN is so smart that a dogpile can form from all the people rushing in to explain Cherenkov radiation.

No, it's correct. The key is the "... in water" part.

Nothing travels faster than the speed of light in vacuum. Light is slower in other media, such as water, where its speed is only 3/4 of its speed in vacuum. This difference in speed is responsible for the light refraction, for example.

Cherenkov radiation: https://en.wikipedia.org/wiki/Cherenkov_radiation

"Speed of light" seems simple, but is a bit more complicated than that.

Great that they are mentioning ThorCon's project in Indonesia. Too bad that they had to leave the US after trying really hard to find a way to build it here.

As far as I know the Chinese are also putting much effort into this type of reactor.

Thats what I heard too a couple of years ago - they were putting huge amounts of money into Thorium research - does anyone know how far they are away from something similar?

very excited about this tech, but i think it will be regulated to death.

You are aware of the current U.S. President and the current EPA Administrator, right?

Not so sure about that. Might risk these billions of coal jobs he created...

“We will begin to revive and expand our nuclear energy sector, which I’m so happy about, which produces clean, renewable and emissions-free energy,” Trump said.


“We’ve already eliminated a devastating, anti-coal regulation, but that was just the beginning,” he said. “My administration is putting an end to the war on coal, going to have clean coal, really clean coal.”

“We will produce American coal to power American industry.”

In the speech now known as the "energy dominance" speech, Trump promoted fracking, nuclear, offshore drilling, and coal (including exporting coal).

ah yes the renewable nuclear

Backstory on the debate: https://en.wikipedia.org/wiki/Nuclear_power_proposed_as_rene...

Regardless, renewable is a less important concept than clean (how do you renew the sun which is a big nuclear reaction?).

The sun will burn out at a fixed time regardless of how much or little energy we harvest from it.

Assuming energy demand growth of 5% per year, we have enough land-based actinates for less than a century of energy usage in fast breeder reactors (if you prefer 2% annual demand growth, it's enough for about 2 centuries).

Seawater uranium buys you more time, depending on how you extract it, but hundreds of years and the sun burning out are two very different timelines.

Seawater uranium goes well beyond "hundreds of years." The oceans hold four billion tons of uranium, which in fast breeders would last many millions of years. On top of that, it's in equilibrium; as more is removed, more will dissolve from rocks. It really is at a timescale similar to the sun burning out.

A hundred years would give us plenty of time to develop alternative energy sources (fusion?). The fossil fuel age also last(s/ed) for about that long.

And how long will it take us to boil of the oceans (as in fusion) assuming 5% year over year increase?

How has energy consumption behaved before around the time of paradigm shifts and plentiful "free" energy?

Currently energy use is about 0.01% of energy that the sun sends us (if my googling is right). If energy use increases 5% per year, it doubles every 15 years or so, so after a hundred years we still use so little energy that it doesn't matter compared to solar heating. I think the oceans are safe.

And I'm all in favor of fission as a bridge-fuel to something more sustainable, but many people act as though it will last indefinitely, when it seems clear to me that it won't.

At current energy consumption, Thorium on earth is so able to power the whole planet for 100'000+ years.

Solar panels do also need resources to produce...

Also those two do not believe in global warming. (One thing nuclear does not cause)

It make take a long time for thorium reactors to come online but it is hard to believe anybody is going to fund the construction of a new large LWR anywhere outside China.

> (One thing nuclear does not cause)

However, two problems remain:

1) where to get the raw material? African mines are not exactly known for adhering to human or environmental rights, also African mines, by nature of being in Africa, don't create American jobs. Same is valid for the other major sources of nuclear fuel, all of which aren't the USA.

2) where to dump all the nuclear waste? I mean, people have debated to put in the most long-living and nasty stuff into special reactors to get it split up to less harmful stuff, but to my knowledge this has never been realized - and NIMBYs are highly afraid of a rad-waste dump near their houses, across the world. Also, no one has shown how to build something that can last over ten thousands of years while still protecting the rad waste.

The use of thorium in the MSR is perhaps 30x more fuel efficient than the current light water reactor. Large amounts of thorium have been buried in the desert by the U.S. government. Also, sufficient deposits exist in the U.S. to support centuries of use.

As for nuclear waste, the real reason why the problem appears intractable is that nuclear waste is not waste.

The LWR gets only 2% or so of the energy in uranium, the same fuel could be reprocessed and used in fast breeder reactors to release the other 98%. In fact, it is the presence of plutonium and other actinides in spent fuel that requires environmental isolation beyond 500 years or so. If we use those actinides as fuel, they do not need to be buried, and if we do that, the volume of waste is vastly reduced along with the half-life.

The fast breeder/reprocessing route has not been commercialized as of yet for a number of reasons. Probably the most discussed is that plutonium, neptunium and other actinides useful for nuclear weaponry could be nicked from the reprocessing plant.

The thorium MSR is an alternate path to a breeder, aka a "thermal breeder". In the case of the MSR, the reprocessing is done online or nearline to the reactor. It is also possible to do thermal breeding with thorium with a modified version of the light water reactor. Reprocessing that is a bitch though...

The most immediate problem facing the industry is an inability to say "it is going to take X years and Y dollars to build a reactor" and then finish it somewhere near on schedule and on budget. Being over 10% would be no scandal, but it is still looking more like 10x than 10%.

Doesn't reprocessing produce a lot of high level waste as a byproduct, thereby worsening the waste problem?

And I understand the Japanese had an experimental breeder reactor for a long time and never achieved actually producing any commercially viable electricity. They did get lots of plutonium, though, which may be turned into bombs any moment.

Early on the fission products were stored in acid solutions in tanks. Circa 1980 the technology was developed to evaporate the solution and trap the fission products inside glass.

Plutonium from either a LWR or FBR fuel cycle is heavily contaminated with isotopes that will cause a bomb to predetonate or get really hot. Somebody with advanced technology (say Japan's government) could probably use electromagnetic separation to remove the unwanted isotopes, but you wouldn't expect ISIS to be able to do it.

The real thing terrorists would want to nick from a reprocessing plant is Neptunium 237; it has a large critical mass compared to plutonium, but it can be separated by chemical means and will not predetonate.

In the 1970s people wrote hang-wringing papers wondering if inventory control could be made good enough to detect diversion, a 2000s accident at Sellafield's THORP plant showed that it probably can't. They lost an Olymptic size swimming pool worth of fluid containing upwards of 50kg of Pu and around 1000kg of U and did not notice for months.

To be fair, it drained into a containment area and did not threaten anyone. They were able to clean it up. But obviously the inventory control was nonexistent.

THORP has been successful at producing plutonium oxide powder but the UK was unable to fabricate it into fuel elements and had to ship it to France.

Reprocessing separates rapidly decaying fission products from slowly decaying transuranics. The transuranics go back in to be burned, the fission products decay comparatively rapidly.

Great that thorium is progressing. I predict the debate about global warming will disappear once we have new power sources in place. Those who denied global warming will suddenly acknowledge it; those who berated the deniers will move on to other issues.

You have way too much hope for the internet to not shit post.

Hinkley C

How'd you like to be the guy pressing the button for 40 years?

I have a better idea: horsecarts and sailships.

Anyone with insight on this I read years ago: http://www.popularmechanics.com/science/energy/a11907/is-the...

I worry that that if Thorium reactors become very very common because they are thought to be very safe (e.g. behind your house common, as some have bragged), but they turn out to be dangerous...we will have a real problem.

I'm not sure if this is a real possibility given our current understanding of nuclear physics and reactor design. We have enough knowledge to fully understand how a reactor like this would function. Past incidents have been caused by design flaws that were known at the time. It's not a matter of lack of knowledge so much as a lack of good management and regulations.

To be clear the worry was not about a meltdown, but that Thorium can be used to create Plutonium 233, per the article I cited.

Right. A Thorium-232 atom that absorbs a neutron becomes Protactinium-233 which decays to Uranium-233, a fissile nuclide like U-235 and Plutonium-239. This is how the controlled chain reactor works but like any fissile material it also has potential weapons uses. Thus, Thorium reactors require safeguards and monitoring just like any other peaceful nuclear reactor.

I think it's unlikely that we'll want to have people playing with radio active waste in their backyard..

We have decent electricity grids, if reactors become financially viable, first goal will be to power the grid.

I don't see any profit margin in decentralizing the grid.

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