A South Korean government panel has concluded that a magnitude-5.4 earthquake that struck the city of Pohang on 15 November 2017 was probably caused by an experimental geothermal power plant....
Unlike conventional geothermal plants, which extract energy directly from hot underground water or rock, the Pohang power plant injected fluid at high pressure into the ground to fracture the rock and release heat — a technology known as an enhanced geothermal system....
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This is both horrifying and incredible. They managed to fracture enough rock to generate energy contained in a mag-5.4 earthquake.
That's around 200 KT of TNT [0].
That's a lot of useful energy if contained. I wonder what the efficiency of the plant would be then.
South Korea already has 23 nuclear plants though [1], I wonder why they decided to go this route, perhaps easier setup and lower associated costs ?
> South Korea already has 23 nuclear plants though [1], I wonder why they decided to go this route, perhaps easier setup and lower associated costs ?
Despite South Korea being among the only countries that can currently do successful large nuclear builds, South Korea's government is fairly anti-nuclear, reflecting fear of the public post-Fukushima [1]. This is really sad because the skilled workers and construction management expertise required to accomplish this are very rare, and this team could be instrumental in very rapidly decarbonizing the world if deployed strategically. S. Korea also has some of the best shipyards. Turning them into assembly lines for GW-scale nuclear plants (floating or embanked) is one of the more interesting ways to rapidly and cheaply build out terawatts of clean, safe energy [2].
A floating nuclear plant sounds like of one the most dangerous things a society can do. One of the problematic aspects of atomic fission energy plants are their failure behaviour. One of the most important aspects there is the containment of the pollution (in Fukushima they literally freeze the ground water under the plant so it is contained from below, too). If you are free floating in water, possibly even an ocean, you are about as uncontained as you can possibly get.
That's a common reaction, but it doesn't stand to much scrutiny. Before radiation gets to the public, about 4 or 5 different barriers have to fail. The first is the fuel pin, then the cladding metal, then the coolant itself (which can often absorb problematic fission products), then the reactor vessel, then the containment, and then dispersal. You're focusing on containment/dispersal.
But how do the first ones fail? The answer is that lack of decay heat removal allows the earlier barriers to heat up, melt, and fail. Well, if you have an intimate connection to an infinite heat sink (the sea), you don't ever lose decay heat cooling. You can't! So your fuel and clad stay intact in almost all scenarios.
Earthquakes? No problem, the sea buffers you.
Tsunamis? No problem, stay in moderately deep water and the wavelengths are so long that you'll barely notice them.
Heavy weather? The world's largest ship (Prelude) is designed to stay operating (it's a LNG facility) during Cat 5 cyclones.
Military attack? Sink and cool passively until a designed recovery operation can occur
Ship collision? Stay out of shipping lanes; worse case, sink and don't leak.
Also, keep people out of your exclusion zone by being a few km offshore.
Honestly it's a pretty slick low-carbon rapid deployment scenario that improves construction cost and safety. Operation will likely be more expensive, but maintenance maybe not (since you can go home to the shipyard and be relieved by a spare).
Better stated: sink and don't leak because you are intimately linked to a near-infinite heat sink, and heating up/melting are a prerequisite to leaking.
The ocean would take a while to corrode through a couple dozen cm of steel, especially in cold water. But you're right that eventual leakage is a concern. A viable design of this kind of system would have to come with a sink-safely-and-cool design fully engineered as well as a designed recovery process. In other words, it should be expected that a recovery and disposal operation will be required (even though it's unlikely to be needed). This system should be designed so the salvage/recovery operation is easy.
Nuclear accidents generally worry about something called Large Early Release Frequency. Some of the most bioactive/dangerous fission products decay away in a few days. This kind of scenario completely eliminates those FPs from concern, though we do still have to worry about the longer-lived ones.
is that assuming steel at the same temperature as the surrounding salt still water, or assuming steel that is hotter than the constantly convecting stream of fresh salty water?
The way the heat transfer would work in this scenario would have small temperature gradients on the outermost layer of heat transfer because steel and water are good heat transfer mechanisms.
They are scuttled floating nuclear reactors at the bottom of the sea. These are real-life examples very similar to the scenario you are inquiring about. They have not corroded away and released wholesale nuclear waste after many decades. If that's not relevant to your line of inquiry then I must be totally misunderstanding you.
>... the ocean is full of salt, how many half-lives until corrosion prevents containment?
quoting you:
>They have not corroded away and released wholesale nuclear waste after many decades. If that's not relevant to your line of inquiry then I must be totally misunderstanding you.
You don't misunderstand me, you purpousely misinterpret my questions so you can give easy answers...
Ah, I see what's going on here. Please review the HN guidelines.
I-131 has an 8-day half-life and is the primary threat to populations in large early releases. The direct answer to your question for I-131 is at least 2,000 half-lives. Sr-90 and Cs-137 have 30-year half lives, so for them it's at least 2. As you surely know, the longer half-life nuclides release energy more slowly and are therefore less dangerous to biological systems. At the extreme, U-238 has a few billion year half-life and can be handled safely without shielding.
In the scenario I'm painting, the reactor would be recovered from the sea within ~5 years so none of this matters. The corrosion will not fail the system within those 5 years. I do not propose to just leave any failed reactor down there indefinitely.
>Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith.
Which is exactly what I was accusing you of before you reflected the accusation. Please note there are 2 components in this rule:
1. Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize.
2. Assume good faith.
I will discuss part 1 in the context of our discussion, but first point out that 2: does not mandate to keep and maintain the a priori assumption of good faith, it only mandates to assume good faith.
Now for part 1, lets personally dissociate and review the discussion as being held by Alice and Bob:
After Bob states,
>Better stated: sink and don't leak because you are intimately linked to a near-infinite heat sink, and heating up/melting are a prerequisite to leaking.
Alice asks a concise question:
>that doesn't discuss corrosion though, the ocean is full of salt, how many half-lives until corrosion prevents containment?
and later Alice adds the question:
>is that assuming steel at the same temperature as the surrounding salt still water, or assuming steel that is hotter than the constantly convecting stream of fresh salty water?
All the while Alice is a priori assuming good faith on behalf of Bob.
Now Bob can give multiple interpretations to Alice's question, and he is required to please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize.
Bob can use interpretation 1 interpreting Alice as Alice1 implying all of the following:
* 1A) Alice is worried about shortlived isotopes
* 1B) moreover she seems to believe steel corrodes in a matter of days in the salty sea, Alice probably never heard of the Titanic recovery, Alice believes that ships can't be reused because after every trip they are decommisioned and a new ship is built for every trip.
* 1C) Also Alice seems to be unaware that Iodine is the most easily mitigated isotope since we can bulk manufacture Iodine tablets containing non-radioactive isotopes.
* 1D) Alice seems to be uninformed about all the above topics despite referencing concepts like nuclear half lives, the corrosion of metal in salty water, convection of hot water in cold water, and the concentration and saturation of metal ions in aquaous solutions...
This interpretation of Alice is easy to criticize, for obvious reasons
or Bob can use interpretation 2 interpreting Alice as Alice2:
* 2A) Alice is worried about longlived isotopes
* 2B) Alice is worried about the influence of energy release in the long tail of nuclear decay: consider a simple system of N identical unstable isotopes decaying to a stable isotope (thats ignoring the worse long decay chains), after one half life, half the number of remaining radioactive particles has halved, but half of the energy that will eventually be released as heat (not temperature!) is still contained in that long tail. Alice wonders if that energy can speed up the corrosion process on long time scales. When salty water dissolves metal, theres a thin layer of water that is saturated by dissolved metal which acts in a self-limiting way. But if the heat causes convection, that thin layer of saturated water will be constantly replenished with fresh unsaturated salty water. Similarily evaporation is much enhanced if convection or wind carries away the saturated air, which is why we like to hang our clothes to dry outside...
If Bob chooses interpretation 1 (which is easier to criticize) over interpretation 2, then it is Bob who is acting in violation of part 1 of the rule from the guidelines...
If Bob then at some point replies "They have not corroded away and released wholesale nuclear waste after many decades." Then Alice can only conclude that Bob has chosen the weaker interpretation Alice1 over Alice2. At that point she simply corrects her a priori assumption that Bob is acting in good faith, and she explicitly points it out.
Then Bob escalates by reflecting the identical accusation in a vague reference to the guidelines, simply because Alice is open about her founded conclusion on Bob's behaviour, while Bob never explicitly states he chooses interpretation Alice1 over Alice2 even though it is evident to any reader... Alice did assume good faith on behalf of Bob, but Bob's replies imply he chose the weaker interpretation Alice1. That is unless Bob genuinely believes people like Alice think ships are one-time-use items, that Iodine tablets do not exist, ...
I hope someone (dang?) who can prove their association with the platform can clear this up, perhaps in your favour perhaps in mine (don't care really, I would just like clarity / precedent, so that we maintain equality before the guidelines)
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Also you keep changing attention to a lesser problem of containment, the short-lived nuclides, for example you state:
>Nuclear accidents generally worry about something called Large Early Release Frequency.
Why are you personifying the accident events? Surely you mean nuclear experts instead of accidents? Let me explain why they focus on the short-lived nuclides: because they can be affordibly mitigated with measures like Iodine tablets. abstaining from eating produce from the affected area for a few days, etc...
The longer lived ones are not necessarily safer, they are simply not affordibly mitigatable over longer timespans! (In case of consumption, the shortlived ones have a higher activity of course, but the longer-lived ones with a lower activity would be consumed for long timespans, such that DNA damage can integrate over time)
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Regardless of these issues, would you consider it prudent for mankind to explicitly define an absolute reference background energy-spectrum of radio-activity? i.e. for each gamma energy bin some typical but from then on fixed reference background activity? Because the only references to background I find are currently comparing with whatever local background is found away from a target of investigation, which is good enough on short timescales, but how will future generations be able to compare their background with ours? It seems we keep assuming that the natural background can not be influenced by human activity, which seems dangerously close to the original fallacy that human activity can not influence atmospheric CO2 concentration...
It's the breeziness and imprecision of "almost all" and "no problem" that gives a bad impression about how far these words can be trusted. What does such a claim actually mean?
Ah, I see. Well I'm definitely trying to whip up excitement to the public here. If I tell you that the LERF goes from 1e-3/year to 1e-8/year, a lot of people wouldn't understand the implication, which is, effectively, "no problem". Nuclear engineers tend to speak in acronyms and numbers, I try to distill it down. There is weight behind these kinds of estimates though.
On the other hand, one would not want to oscillate between breezy "no problem" claims, and engineering jargon. Because jargon is likewise not convincing. It might be helpful to just link to the reliability assessment. The document linked from the MIT website is just a conference publication (I looked it up) which is pretty vague and is really just a concept overview.
Note: I acknowledge that you have much more expertise here than I do, but it's not translating well. OTOH, I'm receptive to actual analysis - I have a PhD and work in a model-intensive engineering field.
Fair. Finding the balance for a wide audience between believable and exciting is tough. I'm usually good at it but in this case, it's my favorite concept in my field of expertise so I get a little too enthusiastic.
Huh. In this entire conversation you've come across as a person way-overstating their case, and as a result being totally unbelievable and unconvincing. And in a thread which is off-topic for the posting, which is a poor choice of a place to engage at all.
I said one thing, people continued the conversation, I continued it with them. There's a collapse thread button for a reason. Yet here we are talking.
What part is least believable for you? Shipyard construction being cheap? Floating nukes being safe? Nukes being safe in the first place? Nukes being low-carbon? Many of these thing sound surprising because they go against pop culture but they're interesting in that the scientific consensus is fairly opposite of pop culture on this topic.
That risk assessment assumes only the technical aspects. But there are still institutional, management and other 'people' issues that could render any engineering guarantee fruitless. Otherwise, the delivery of nuclear plants would have no way to off schedule.
I have no objection to the development of nuclear technology. But as I understand, what concerns people is not entirely the 'likelihood' of the disasters but rather the 'severity' of them. After all, People make mistakes and organizations corrupt. So, I think any tech progresses on the scale-down of the worst case where all safety is off would be far more helpful in convincing the public.
In order for the sea to act as a heat sink, many of the initial barriers will have failed. Only then can sea water touch overheating fuel. How does being in the sea stop the fuel rods from melting (or whatever they do when they're going bad)?
Natural circulation heat exchangers. The AP1000 has this huge tank of water on the roof that can cool things for 72 hours. Then it runs out of water. At sea with some displacement you use this system but never run out of water.
And as far as I can tell, none if those nuclear reactors have been leaking radioactive material. The fact that close to a dozen nuclear power plants have been sent to the bottom of the ocean and have maintained their integrity is testament to just how safe nuclear power is when implemented correctly.
These subs are continuously monitored. Articles on the internet say Kursk had a minor leak that was quickly repaired, without coming close to any health concerns.
Remember nuclear pressure vessels are subject to some of the most harsh conditions when in operation. They're built to withstand contact with extremely hot water under pressure. Will salt water eventually corrode through it? Maybe. But remember energy through fossil fuels and organic matter kill 3 and 4 million people per year respectively. Those concerned with nuclear safety often fall into the fallacy of letting perfect be the enemy of good. The best solution is the least-bad solution.
Keep in mind we've also blown up 500+ nuclear bombs including almost 10 underwater. Not a great idea in hindsight, but overall we didn't experience any major problems as a result.
Seems like even in the worst and extremely unlikely scenario of full detonation, we'd still be fine.
The difference is that those tests were done on or near land, the fallout settled either on land or in shallow water, close to marine life.
The explosions which happened in deep water (Wigwam in 1955 for instance) had practically zero lasting effects beyond radioactive steam entering the atmosphere.
The scale is a little different though. Say a 300MW submarine reactor runs for 10 years, the energy produced is about 20 megatons. The energy in a bomb might be 400 kt, half of it from fission, so the reactor will contain a hundred times more spent fuel.
Of the nine sinkings, two were caused by fires, two by explosions of their weapons systems, two by flooding, one by bad weather, and one by scuttling due to a damaged nuclear reactor.
Your scale is off a bit. The Fukishima reactors were 484 MW to 1.1GW. Diablo Canyon, a fairly "new" (and now unused) Nuclear reactor setup in California were both units under 1.2GW. The reactors on the "Ford" class aircraft carriers are reported to produce about 700MW each.
*Typical power plants reactors operate in the GW, not TW. So there's about an order of magnitude difference between subs and power plants, not 4 orders of magnitude.
Ah, the classic "this old power plant design had this failure mode, therefore all nuclear does this" argument. Do you know when Fukushima was built and what year the designs were drafted for it?
I don't know enough here to comment on who's right, but when the magnitude of catastrophic failure is large enough, model error is appreciably important. So in those cases past experience is a very important input into the decision, even if not perfectly correlated.
If anything, it proves that identifying all failure modes is challenging, and theoretically safe is not the same as practically safe.
"So in those cases past experience is a very important input into the decision, even if not perfectly correlated."
Of course it is, which is why modern reactor designs have incorporated safety features based on these accidents and older designs have been retrofitted (with some exceptions that are legitimately concerning). It's entirely true that it is impossible to predict every mode of catastrophic failure, but that does not mean it's impossible to create designs that are resilient to unplanned disasters. No type of power plant can be perfectly safe, but
for assessing practical safety records, in terms of deaths / TWh generated, even estimating conservatively nuclear power is safer than any other source of power (including wind and solar). Some references for this:
Hydroelectic as well technically. A set of hydroelectric dam failures in China in 1975 killed more people directly from the event (171,000) than is estimated for the direct and future deaths caused from Chernobyl and Fukushima combined.
The Boing accidents showed that technological progress doesn't help in minimizing errors, as there's always a higher incentive of minimizing costs in the implementation, even if the plan is safe. A very important thing we can do is to limit the possible worst case scenario.
It probably can, but there's a fundamental difference between a nuclear reactor and an airplane.
There's a handful of nuclear reactors compared to planes, and new nuclear reactor designs, where there's an opportunity to cut corners, are not being introduced at the same rate as new plane designs.
A reactor is a large, heavy, stationary thing. Economic concerns exist, but they're not going to make engineering decisions based on weight like you would in a plane where every kilogram of material costs a fortune in fuel over the lifetime of the plane. An extra chunk of concrete in a nuclear plant costs nothing, operationally speaking.
We're just lucky that the planes aren't nuclear despite many wildly ill-advised attempts to make this a reality.
If you look at Fukushima disaster, it was not a design problem either, but maintainence problem. It was probably running more without modifications than it was designed for.
There were updates suggested to modernize the facility, but for cost cutting purposes they were ignored:
It was a design problem and a maintenance problem. A lot of the design decisions made in that era later proved to be Very Bad Ideas, like how there was no proper hydrogen containment above the reactor vessel.
Newer designs have suffered more major faults and managed to contain virtually all of the radiation. American designs, in particular, place great emphasis on having an extremely resilient containment structure above the reactor. A lot of things can go horribly wrong but so long as the extremely radioactive gas is contained it can later be cleaned up. These radioactive elements are extremely toxic, but also very short lived. You just need to buy time.
The Fukushima design may as well have had a tin roof, it exploded almost immediately and exposed the reactor to the elements. If that's not a design flaw, I don't know what is.
That and a number of the systems necessary to keep the reactor under control depended on poorly positioned generators that weren't flood-proofed. This seems like a major oversight on a building located in a tsunami and typhoon zone.
I agree, Fukishima was designed about 15 years after nuclear power was first invented, it isn't that far off from complaining about how unsafe cars are in crashes using Model-Ts as an example. Fukushima should have been decommissioned before it was even 'completed' but because of the political barriers in building a new nuclear plant(s) they just stuck with it since it had already got over the regulation hurdles.
I think our problems with nuclear power are 95% political and maybe 5% or less technological. Canada for example has nuclear plants that use a neutron moderating coolant. If they lose coolant, the reaction stops. Unlike earlier designs where a loss of coolant lead to overheating and potential explosions. Not to mention new nuclear plants need 6-7 completely independent shutdown/safety features which is unheard of for earlier plants that have at best 1 or 2 emergency shutdown procedures that interfere with each other.
Water is a great radiation barrier. The "nuclear" failure option for a floating plant, sinking it, is reasonable. There are already a few reactors on the ocean floor (subs). That is far safer than having them in the atmosphere.
Floating nuclear power plants are already quite common and have a spotless track record in the past century. That's wht most of America's aircraft carriers and modern submarines are.
This neglects the failure modes of nuclear power. The biggest danger, by far, is overheating, fire, and melting.
Paradoxically, a nuclear plant could be made extremely safe if it just dumped all the fuel into the ocean at the first sign of trouble.
With ulimited cooling the fuel can't melt so it will be safely contained within the rods/pellets.
Yes the radiation near to the fuel would be insane, but water is so dense it would be safe to swim around maybe 50 feet away.
There's never been a bad accident in spent fuel pools even though they contain orders of magnitude more fuel than operating reactors. This is just because it's really hard to melt something sitting in thousands of tons of water
South Korean government is not against anti-nuclear. It's CURRENT administration of South Korean govt is. Once the president and his cabinet members leave in due time, anything can change.
> This is both horrifying and incredible. They managed to fracture enough rock to generate energy contained in a mag-5.4 earthquake.
Or they fractured enough rock to cause what would have been an earthquake of magnitude >= 5.4 at a future date to happen at that time, which I think is more likely.
As I understand it, earthquake's are opposing forces of tectonic plates that finally overcome their coefficient of friction. Affecting that coefficient of friction slightly could cause it to happen sooner or later.
Alternative alternative explanation: they caused what would have been 4096 magnitude 3 earth quakes (0.2 magnitude difference corresponds to 2x energy per wikipedia) to merge together into a single magnitude 5.4 earthquake. Since they reduced the coefficient of friction enough to allow all that energy out at once instead of in small steps.
I had a physics professor whose day job was geophysics. We were discussing earthquakes, and he said he really wanted to investigate the possibility of eliminating the threat from the San Andreas fault by intentionally triggering it at some regular interval, before the opposing forces built up to dangerous levels. He was onto something!
Yes, precisely. The problem is what to do with all the currently built up energy. We know that a big one is coming, we don't know when. Before we can implement the program for slow steady release of energy, we will have to suffer through one big one.
Fukushima is in a better place today in that it's past the big one, and could try to release energy slowly.
Regardless, it'll never happen in the USA, given the anti-science political climate. Remember when they were about to launch the CERN LHC and everyone freaked out about "they're going to create black holes and kill us all!?" Now imagine California soccer moms and their Facebook groups spreading misinformation about "they're triggering earthquakes and will kill us all (and also vaccines cause autism!)" …
Heh, yeah. Same as the backlash to proposals for geoengineering our planet’s temperature and atmospheric composition. The way I see it, if we expect to inhabit this place for the next several hundred thousand years, we’ll either 100% have to have that ability, or instead be satisfied riding our Hobbyhorse of Environmental Virtuousness right into extinction or evacuation as whatever meager efforts we make are swamped by natural variations. Might as well start doing the science now.
Back to earthquakes though. Somewhere in HN there’s a comment on a story about the Cascadia subduction zone suggesting that we publicly select a date some many years in the future on which we’ll get everyone to a safe place, then pop that fault with a bunch of buried nukes. Would make some great TV!
While true, it's mostly pedantic. OP is talking about a potential earthquake harvesting power plant. So generating in this sense means releasing the trigger, in the same way that burning coal is generating energy. It's just releasing the stored chemical energy of the coal, but we still say that coal powerplants generate energy.
I was thinking about the same question and came at it from the other side, which is "How big a plant and how far away do you have to situate it to destroy a city?" Which is to say, what would someone need to do to weaponize geothermal fracking? Urban warfare is siege warfare and being able to knock down the castle without having to expose yourself to enemy fire would seem to be an advantage. The fault lines would need to co-operate too of course.
Distance and size of plant would also be heavily dependent on the fault lines. Could be a very useful military tool for attacking particularly vulnerable places (if you can fortify a nearby position against enemy attack for long enough to build such a thing). Seems overly-situational without some extremely rapid assembly.
The energy stored in the fault was already there pent up. They just released it.
Which if you actually look at it from a damage perspective. Might be sensible.
Not allow those mega-nukes like the san andreas fault to build up tons of energy. Instead frack vibrate the fault loose in lots of micro quakes.
A South Korean government panel has concluded that a magnitude-5.4 earthquake that struck the city of Pohang on 15 November 2017 was probably caused by an experimental geothermal power plant....
Unlike conventional geothermal plants, which extract energy directly from hot underground water or rock, the Pohang power plant injected fluid at high pressure into the ground to fracture the rock and release heat — a technology known as an enhanced geothermal system....
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This is both horrifying and incredible. They managed to fracture enough rock to generate energy contained in a mag-5.4 earthquake.
That's around 200 KT of TNT [0]. That's a lot of useful energy if contained. I wonder what the efficiency of the plant would be then.
South Korea already has 23 nuclear plants though [1], I wonder why they decided to go this route, perhaps easier setup and lower associated costs ?
[0] https://science.howstuffworks.com/environmental/energy/energ...
[1] http://www.world-nuclear.org/information-library/country-pro...