World Is Ignoring Most Important Lesson From Fukushima 328
mdsolar writes "Kenichi Ohmae, an MIT-trained nuclear engineer also widely regarded as Japan's top management guru, is dean of Business Breakthrough University. In the CSM he writes: 'Fukushima's most important lesson is this: Probability theory (that disaster is unlikely) failed us. If you have made assumptions, you are not prepared. Nuclear power plants should have multiple, reliable ways to cool reactors. Any nuclear plant that doesn't heed this lesson is inviting disaster.'"
Or use a different type of reactor.... (Score:5, Informative)
The Black Swan (Score:4, Informative)
Re:The Black Swan (Score:5, Informative)
That has nothing to do with probability theory. It turns out that you can predict how much wealth people have from one to the next very neatly. Failure comes in when you assume that the distribution is Gaussian. It's not; it's log-normal. The billionaire is no more an outlier in that distribution than a pauper.
Re:Correct (Score:5, Informative)
For those who don't follow reactor tech and don't know whats being talked about, liquid sodium reactors use literally a vat of salts and radioactive material in a magma-like sludge. There is a plug at the bottom of the vat with a melting point that is well above operating spec, but well within reach if the reactor lost cooling. If all other failsafes are disabled, the plug melts and all the molten sludge runs into 2-3 smaller tanks. The reaction then stops being self sustaining, and you just have to recover the containment units and repair the reactor. Its literally idiot proof barring a fault line opening a chasm beneath the plant or a direct asteroid impact.
There are also gravity-fed means of cooling conventional reactors, but I wouldn't call any of them fool proof. Liquid sodium seems like the best bet to me from a safety standpoint, at least as far as using up existing nuclear material. Thorium reactors show promise as well, but since we have a ton of reusable nuclear material liquid sodium would be my choice from a practicality standpoint.
Re:Correct (Score:5, Informative)
One MIT Engineer to Another (Score:5, Informative)
I am an MIT trained nuclear engineer than specializes in Probabilistic Risk Assessment. The first thing we should note is the PRA has had many benefits for the nuclear industry. Once you calculate the risk, and understand the contributors, you understand how to make things safer.
http://mydocs.epri.com/docs/CorporateDocuments/SectorPages/Portfolio/Nuclear/Safety_and_Operational_Benefits_1016308.pdf
The thesis of this article has a few problems, though the conclusion isn't horribly off base. The first problem is that he believe probability theory was applied to ignore the risk of the tsunami. The opposite is true. In fact, probabilistic hazard assessment of the tsunami showed the site to be horribly under prepared in 2006 (10% chance of exceeding the design basis in 50 years or about 1 in 500 per year [which is high for nuclear reactors]). There were even more studies in later years before the tsunami hit. This was just plain bad management and shows what may happen when you ignore updated risk information.
http://enformable.com/2011/10/new-exposed-scandal-shows-tepco-calculations-in-2006-showed-probability-of-worst-case-tsunami-dramatically-increased-10-over-50-years-utility-took-no-countermeasures/
The main point though, that no matter how unlikely a single event is (in this case a tsunami), you ought to have some countermeasures, is not bad. That is why PRA is used in combination with deterministic defense-in-depth measures at well designed, operated, and managed nuclear reactors. Mobile emergency diesels should be available to all reactors and are in the United States. This is a feature that Fukushima did not have. At the end of the day though, ceoyoyo is right. Even with multiple methods of cooling a reactor, you can not eliminate the possibility of core melt and release of radionuclides to the public. You can only ensure the release is acceptably infrequent. This brings us full circle to the fact that using probability theory to focus on the high risk stuff is good and that Fukushima failed to do this.
That being said, even in the case of passively cooled reactors such as fast reactors, massive earthquakes (1 in 1,000,000 per year or less), could destroy the water tank or piping required for passive cooling to take place. I would argue that while one should not ignore earthquakes and other rare external events below a certain probability. The burden would be onerous to use events below 1 in 100,000 per year as a design basis. This is in line with previous regulatory safety goal and can be seen in use in debate over the transition break size rule. A plug for my journal article is below. If you are wondering which author I am, the hint is that I am not the NRC commissioner.
http://www.sciencedirect.com/science/article/pii/S0029549311008284
Re:Correct (Score:3, Informative)
They US authorities on '60s started trying gravity on various types of reactors for many years (passive cooling) and it failed miserably all times. Download the excellent BBC's 1992 documentary on the subject A is for Atom [archive.org], or watch it on YouTube [youtube.com].
It was after they had confirmed the problem that they started installing diesel generators to operate the cooling pumps. The problem was discovered also in USSR. Chernobyl erupted during an experiment to test the cooling apparatus while disconnecting the plant from grid.
The root cause of all this was that they designed the commercial Nuclear Plants by scaling the 60cm diameter Submarine Reactors into 3 meter or even more. That way, the multiplied the fuel mass x1000, and disregarded that fact they were no longer 100 meters deep below the ocean surface, something that would guarantee passive cooling simply by hydrostatic pressure.
Re:Reckless! (Score:5, Informative)
From what I understand pebble-bed reactors don't even count on gravity-fed cooling. The reaction simply stops if it gets too hot, effectively setting a maximum temp that won't burn through concrete.
Of course, pebble-bed was more about demonstrating idiot-proof safety than practical power generation, but it would actually work just fine (if not as cheaply as more sophisticated designs).
Re:Too many protective measures (Score:2, Informative)
Re:Correct (Score:4, Informative)
"Idiot proof" - right there you just lost a couple points. Build a better nuclear reactor and the world builds a better idiot. Not that I'm against nuclear reactors, I just agree with the original premise - failures *will* happen with any system. Multiple independent fail-safes and dead-man systems are necessary for a system like this.
Theres some truth to that, but i meant it in the sense that human interaction isn't needed in the slightest, nor is any real mechanical action other than liquid flowing downward. Its not like "modern" (as in what operates now) reactors, where there is a time limit on the response within which some human being has to respond. Every human being could vanish from the earth in an instant, and a liquid sodium reactor would turn itself off 100% of the time. You take the human out of the equation.
Re:Correct (Score:5, Informative)
You are correct however in that if, for any reason, external cooling of this "freeze plug" is stopped, the plug melts and the reactor content drains to split storage tanks stopping the reaction.
The stopping of external cooling may be due to all power generation is lost (no power to cooling), external system is destroied or ruined (natural disaster) or everybody on the plant has already left and the plant is left to fend for itself and fails (zombie invasion).
As you say however, it seems to me too, to be the best solution so far.
A benefit of Fukushima (if we look hard) is that the research on other types of reactors are now starting again, even though they can't produce nuclear weapons.
Re:Correct (Score:5, Informative)
Molten salt reactors introduce a new problem though: the material is highly corrosive, and there are few materials that have even been tested that could provide a proper lifespan to the reactor. Furthermore, maintenance on the entire primary loop is like maintenance on the containment vessel for water cooled reactors: you just don't do it. This means that while the system is safer from a human fuck-up perspective, it presents brand-new engineering, construction and maintenance challenges.
Re:Correct (Score:4, Informative)
The CSM is a very weird entity. It produces some really excellent journalism, however, the religious group behind it has some truly wacky beliefs regarding medicine resulting in denying their children access to medical care until it's too late. I don't really know what to make of it; maybe it's a good illustration that everyone is crazy in one way or another.
Common cause failure+just 2 generators per reactor (Score:4, Informative)
Fukushima had nothing to do with probability theory being wrong. Ask google scholar for "common cause failure nuclear" and the oldest citation on the very first page is from 1976. This is age old stuff.
Now look at the greenish boxes on this picture:
http://www.tepco.co.jp/en/news/110311/images/110519_2_2.jpg [tepco.co.jp]
Those are 7 of the 13 diesel generators about to be flooded. Besides those, there was just one generator in the basement of each turbine building. Only one generator survived (in reactor building #5 - providing power for decay heat removal there and for reactor #6) and this is not surprising. Put all your eggs in one basket and you're in trouble when the basket drops.
The problem was a simple matter of not having enough generators and not putting enough distance between them. Following the most stupid and simple-minded rule imaginable - that of having a distance of 50m or 100m between each emergency generator and having at least 3 generators per reactor (in Germany there are at least 4 for each reactor), you would have ended up with generators on the hills behind the reactors, because there is no room for them anywhere else.
I have no problem with having emergency generators next to the coast or in a basement. Both are potentially sheltered positions from some sort of accident - just not from a tsunami. That's why you should have a diverse set of several emergency generators, if possible based on different designs. (What if you run out of diesel or your most recent diesel delivery was spoiled?)
All the better if you have a modern reactor, like the Russian AES-92 or AES-2006 designs (from 1992 and 2006 respectively) that can remove decay heat without any active systems. (That's right, the Russians a ahead of the game, thanks to not treating research in nuclear power as a waste of money, as it is in the US and EU.)
Re:Reckless! (Score:4, Informative)
The "only" problem with pebble bed reactors is that if the pebbles are exposed to air, such as if the coolant is lost, they violently burst into flames and spew forth high radioactive and toxic smoke. Not exactly idiot proof if you ask me.
Re:Reckless! (Score:5, Informative)
Re:Reckless! (Score:5, Informative)
Re:Reckless! (Score:5, Informative)
Then it did not work very well, considering that one of the two pebble-bed reactor ever built and operated [wikipedia.org] is classified as the highest beta-contaminated site worldwide. In the other one [wikipedia.org], the pebble design caused a number of issued with feeding, as pebbles would get lodged (maybe only 0.0001% of the time) and required, well, someone to open the tube and shovel'em. Letting out lots of radioactivity in the process.
That, and pebble-bed reactors are the only ones using compressors (as opposed to liquid pumps) in the primary circuit. Compressors are mean beasts and are not unknown to surge and explode, plus the most efficient type (the axial) has its highest efficiency at the closest point to the stall line [wikipedia.org].
Re:Error in translation? (Score:4, Informative)
The amount for the cleanup I saw (glanced on Wikipedia) was around $13 billion USD (that might not include the cost of safely decommissioning the reactor, I couldn't find a good number for that, so that figure might just be radiation cleanup). The total economic cost of the earthquake was (by the World's Bank estimate) $235 billion. Obviously, until all is said and done and the reactor is completely decommissioned and the land cleared up, we won't know for certain, but chances are there is at least one order of magnitude difference in the costs. Granted, the nuclear cleanup is still an appreciable fraction of the total cost (and a lot of money no matter how you look at it... well, unless you're a US legislator), but again, the earthquake/tsunami caused far more damage and cost far more money than the nuclear meltdown.
Again, that reactor should have been replaced by something else a decade ago at least, and even then, it still shouldn't have failed if they'd done it properly, but the catastrophe that caused the failure was sufficiently powerful to dwarf the damage caused by the failure itself, which in the end is the only real standard you can establish for the safety of any power system. Contrast that with coal, which doesn't require any catastrophe to spew harmful emissions, or hydroelectric, which in one failure kill over 170,000 people (Banqiao Dam).