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....
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 .
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 , 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 . 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 .
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).
Love the "sink and don't leak" requirement.
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.
This isn't hypothetical. This list may interest you: https://en.wikipedia.org/wiki/List_of_sunken_nuclear_submari...
>... the ocean is full of salt, how many half-lives until corrosion prevents containment?
>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...
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)
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)
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...
With that much "no problem", it seems like something may have been overlooked in your summary above.
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.
Here is a master's dissertation from MIT on the topic that goes into lots of good analysis: https://dspace.mit.edu/handle/1721.1/103707
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.
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.
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.
Seems like even in the worst and extremely unlikely scenario of full detonation, we'd still be fine.
Some Marshall Islanders would like a word
The explosions which happened in deep water (Wigwam in 1955 for instance) had practically zero lasting effects beyond radioactive steam entering the atmosphere.
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.
(for those looking, it's to the movie The Hunt for Red October)
School shootings in the USA and ISIS beheadings don't affect my daily life, either.
Typical powerplant reactors operate in the TWs.
Yes, it's 1-2 orders of magnitude.
I think it is extremely irresonsible to build military equipment with nuclear reactors. They are destroyed in conflict, polluting everything.
If anything, it proves that identifying all failure modes is challenging, and theoretically safe is not the same as practically safe.
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:
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.
There were updates suggested to modernize the facility, but for cost cutting purposes they were ignored:
It always comes down to cost cutting when the accidents are rare enough.
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 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.
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
Pros and cons of a democratic government I guess.
Anyway, you have it backwards. The S Korean government is not against anti-nuclear, it is anti-nuclear. But I suspect that was a typo.
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.
Is static/dynamic friction even a semi-accurate model for plate tectonics?
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!)" …
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!
No, they managed to fracture enough rock to destablize the system and allow the fault to slip and release the energy it had built up over decades.
In effect, this pulled the trigger. The energy was in the action, which was cocked by the earth.
Good for softish sci-fi, though!
It was probably hanging in a balance. Then boom!
Atoms scare uniformed voters.
Similarly, a low-energy scream in the montain can trigger a high-energy avalanche.
While this is a popular myth, it's actually entirely false. You can shout and scream all you want - there's not enough energy transmitted to the snowpack to actually trigger an avalanche (by at least two orders of magnitude). This has been debunked by multiple studies, one example here: http://www.gblanc.fr/IMG/pdf/reuter2009.pdf
It is like heating a pot of water to 100c. It is about to boil. Shout at it and it will start to boil a picosecond faster than if you didnt shout at it. Be really careful with the temperature and maybe your shouting makes it boil when otherwise it never would.
Back country snowboarding is a great example where small avalanches are much more common even if most of them don’t become significant. But, because the many small avalanches happen close together they are much more likely to grow. This is also why sound is more effective than you would expect, getting a huge number of tiny avalanches to happen at the same time makes it significantly more likely to form a large one.
Sources: personal experience in AIARE training  and Utah Avalanche Center via Myth Busters 
Then how do they happen naturally?
The goal of the bomb is to thump the snow hard enough that if any weak layers of snow exist below a hard slab of solid snow, the slab will crack, slamming air through the weak layer, breaking the support of the rest of the slab and causing a slide.
Naturally occurring avalanches usually need some obvious change of force on the snowpack, or some reason why a weak layer becomes weaker. I'd guess that a sonic boom, or definitely a scream, couldn't do enough in almost any situation to tip the balance.
That's why the efficiency of the power plant (if this energy would have been captured) would have been a sight to see on paper. The energy they put into the fracking would have been tiny compared to this.
He did imply it would likely not be possible. He said that if it could be captured, it would be an absolutely mind-boggling ROI in terms of energy in vs energy out.
However, think of the sheer amount of potential energy cause by plate tectonics... we're talking about continents... moving.
Also, just like after that scream, there is no avalanche risk, since all the snow slid down the valley, there should now be no quake risk for quite a while at that site.
I read occasionally that fracking causes earthquakes, too. While there is controversy around fracking, I see the systematic de-stressing of the earth's surface as a benefit.
Apparently the rest of them are mostly caused by a similar process of injecting wastewater deep under ground. Of course, fracking is a major producer of wastewater, so it is therefore an indirect cause of many more than 1-2% of induced quakes.
Those of us in geological fields totally disagree with you. If you start a small earthquake in San Andreas, say up in the northwestern section, you can trigger a full-length chain reaction that culminates in unleashing the big one which will rip all the way through Mexico. What is worse is that the earthquake will get stronger as it propagates along the fault line. What you call the big one in the northwest section where it all began is thousands of times weaker than what gets felt further down the fault.
It might not ever hit. Crustal rocks can permanently store tremendous amounts of energy as stress; if the stress is changing, the fault might only move enough to release some small delta of the total stored stress. But: grease the system and you might release a lot more, and all at once.
It's very hard to predict what will happen, either naturally or human-triggered. IMO this is a good argument to not rush it. Every day that passes gives us more time to understand and prepare.
There is also the question of what happens now that it has been released. Rocks are all connected, so a release of stress in one place might result in movement somewhere else eventually.
BTW it is difficult to measure stress in crustal rocks remotely, without releasing some of it. So all of this is hard to know, and therefore hard to account as risk in new hydraulic injection projects.
It was a strange story. It started out with ideas for
super-high-temperature mobile reactors that could melt
a shaft ten miles down to tap geothermal energy. In
the early 1970s the enthusiasm for that kind of thing declined, so they got an idea to tap geothermal energy
using "fracking" technology which existed back then but wasn't anywhere near as capable as it is today.
One thing I remember about their work is that they didn't observe any fracking-related seismic activity at all: when you frack sedimentary rock you get the rapid formation of large cracks with obvious seismic activity. At least in that experiment they found that fracking would open up micro cracks in bedrock slowly and that there was no obvious activity from it.
In my area, Pittsburgh Tristate area (WV,OH,PA) fracking is big business. Seems we are fortunate to not have a major fault line running through the area.
edit - clarifying that I am talking about fracking for fossil fuels
If we can cause them, I wonder, will we be able to prevent the natural ones as our knowledge increases?
There's big quakes and there's little quakes. But energy is still linear. The fact that a quake releasing 1/3 of the energy of a 6.0 is not denoted as 2.0 quake, does not mean that it isn't releasing 1/3 of the energy.
I'm not a quakologist. Am I wrong?
There's been a great deal of ridicule placed on opponents of geothermal energy, saying that geothermal could never contribute to an earthquake. I'm hopeful the ridicule will start to go away now.
The closest I've seen is sources saying that fracking itself only explains a minority of the increase in earthquakes in places like Oklahoma, and that the majority are more properly attributed to other things, particularly the wastewater injection wells that fracking operations use to dispose of all the wastewater that fracking produces.
Which is such an amazingly damn hair-splitty distinction to most of us, but I can see where a spin doctor could have lots of fun with it.
South Korea, like most other developed nations, is trying to increase the use of renewable energy. There are many hot springs in Korea, especially around active faults. Geothermal is an obvious candidate in those areas. Of course they're also doing wind and solar where feasible.
Fracking is happening all over the US (Appalachians, the Dakotas, Texas), but for some reason Oklahoma only gets the quakes. I think it's because only Oklahoma has these bad wastewater wells. Apologies, can't find the sources I found a few years ago that convinced me of this.
The keyword is induced seismicity. I hadn't heard of that before.
A 5.4 is a quake where Californians finally start paying attention, but generally doesn't cause a lot of grief unless something very unlucky happens.
What is the conspiracy theory here?
So, the "drink your milkshake" level access isn't crazy.
A tunnel is useful; you can get past the landmines and other defenses. Causing an earthquake a few miles across the DMZ is far less useful.
Hence the tunnels.
North Korean government's long standing, highest priority goal is conquest of South Korea through any means, including military invasion.
I'm disputing "earthquakes as offensive weapon" being useful. Not tunnels.
The entirety of Himalayas is earthquake Zone-4|5 and with many such borders.
The current government, which ousted the former goverment with absurd scandals, is under a huge bribery and corruption scandal which includes kpop stars, police and prosecutors alike.
The current government always tried to shift the media’s attention when they were in trouble with former government’s incidents and this is one of them.
The government is actually trying to indict former government’s staff and let them take all the media’s blame, while they clean up their own bribery scandal.
The moment magnitude (Mw) 5.5 earthquake that struck South Korea in November 2017 was one of the largest and most damaging events in that country over the past century. Its proximity to an enhanced geothermal system site, where high-pressure hydraulic injection had been performed during the previous 2 years, raises the possibility that this earthquake was anthropogenic. We have combined seismological and geodetic analyses to characterize the mainshock and its largest aftershocks, constrain the geometry of this seismic sequence, and shed light on its causal factors. According to our analysis, it seems plausible that the occurrence of this earthquake was influenced by the aforementioned industrial activities. Finally, we found that the earthquake transferred static stress to larger nearby faults, potentially increasing the seismic hazard in the area.
The moment magnitude (Mw) 5.4 Pohang earthquake, the most damaging event in South Korea since instrumental seismic observation began in 1905, occurred beneath the Pohang geothermal power plant in 2017. Geological and geophysical data suggest that the Pohang earthquake was induced by fluid from an enhanced geothermal system (EGS) site, which was injected directly into a near-critically stressed subsurface fault zone. The magnitude of the mainshock makes it the largest known induced earthquake at an EGS site.
"Earthquakes have been linked to geothermal power plant in other parts of the world. But the Pohang quake is by far the strongest ever tied to this kind of plant — 1,000 times mightier than a magnitude-3.4 quake triggered by a plant in Basel, Switzerland, in 2006."
If you take the word `purely` out of your statement, it is a political decision. Seems to be based on science though. Everything else becomes irrelevant. This also reminded me about the `fracking` debated in US. If I am understanding this link  correctly, it's not the fracturing of the rocks but the high pressure liquids that induces earthquake? I am still unclear on the detailed mechanism.
What are you talking about. The bribery/corruption scandal of the "Burning Sun" nightclub is linked to Gangnam police office, which is not exactly known for being Moon's supporters. We're talking about old boys with old corruption that dates back years. Today there was another revelation (although still unconfirmed, it seems) that the guy who started it all by beating up a nightclub patron was none other than the nephew of Choi Soon-sil, the crazy shaman friend of former president Park whose friendship basically brought down the previous government.
The other two sex scandals are even worse: they involve a high-ranking government officer of PGH government, and someone in the owner family of the ultra-conservative newspaper Chosun Ilbo, respectively.
So there's no reason why Moon would want to manufacture an earthquake controversy to turn people's eyes from these sex scandals. If anything, it should be the other way.
Get your conspiracy theories straight, geez.