[roenxi]

I mean, ok. So say they build the plant 35m higher up, then get hit by a tsunami that is 36 meters higher [0] than the one that caused the Fukushima disaster? If we're going to start worrying about events outside the design spec we may as well talk about that one. If they're designing to tolerate an event, we can pretty reliably imagine a much worse event that will happen sooner or later and take the plant out. That is the nature of engineering. Eventually everything fails; time is generally against a design engineer.

Caveating that I'm not really sure it was even an out-of-design event, but if it was then it is case closed and the swiss cheese model is an inappropriate choice of model to understand the failure. If you hit a design with things it wasn't designed to handle then it may reasonably fail because of that.

[0] https://en.wikipedia.org/wiki/Megatsunami homework for the interested, it is cool stuff. Japan has seen some quite large waves, 57 meters seems to be the record in recent history.

[drtgh]

In Japan they have the "Tsunami Stones" [0] across the coast, memorials to remind future generations of the highest point the water reached.

It was negligent to construct a nuclear plant at sea level, it was just a plant waiting to be flooded, and for such case they had ten years to design protections after being requested to reinforce measures (along with the other Japanese plants), but I can imagine the ones that should put the money was not very collaborative (I even doubt if such responsible learnt the lesson).

[0] https://www.smithsonianmag.com/smart-news/century-old-warnin...

If it was a cheese model or not I do not enter (notice that parent of parent and me are different users), their negligence breaks all the possible logic we could apply without introducing the corruption's variable behind such decades of bad decisions.

[roenxi]

> It was negligent to construct a nuclear plant at sea level, it was just a plant waiting to be flooded,

So why did they build it there? It isn't a gentleman in a clown hat hitting himself on the head with a rubber mallet, they had a reason. These things are always trade-offs.

Maybe if they'd built it up on the hill there'd have been an earthquake, a landslide then the plant slides into the sea and gets waterlogged. I dunno. If we're talking about things without a clearly defined bounds of risk tolerance that is the sort of scenario that can be bought up. You're talking about negligence, but you aren't saying what tolerances this plant was built with, what you want it to be built to or what the trade-offs you want made are going to be. Once you start getting in to those details it becomes a lot less obvious that Fukushima is even a bad thing (probably is, the tech is pretty old and we wouldn't build a plant that way any more is my understanding). It isn't possible to just demand that engineers prevent all bad outcomes, reality is too messy. It isn't negligent if there are reasonable design constraints, then something outside the design considerations happens and causes a failure, is the theoretical point I'm bringing up. It is just bad luck.

The whole affair seems pretty responsible from where I sit a long way away. Fukushima is possibly the gentlest engineering disaster to ever enter the canon. It is much better than a major dam or bridge failure for example, and again assuming the event that caused the whole thing was unexpected not even evidence of bad management. Most engineering failures involve a chain of horrific choices the leave the reader with tears in their eyes, not just a fairly mild "well we were hit with a wild tsunami and doubled the nominal price tag of the cleanup with no obvious loss of life or limb". And bear in mind we're scouring the world for the worst nuclear disaster in the 21st century.

And besides, they did build it above sea level.

[cpgxiii]

> "well we were hit with a wild tsunami and doubled the nominal price tag of the cleanup with no obvious loss of life or limb"

This is a bit of a wild understatement. (1) the tsunami was by no means wild, as multiple posts here have referenced, and (2) the incident resulted in a number of significant injuries, not including for deaths involved in the evacuation. And those deaths very much count - you can't hand-wave away the consequences of the evacuation on the basis of hindsight that the evacuation was larger than the final outcome necessitated.

[roenxi]

> And those deaths very much count - you can't hand-wave away the consequences

I don't. If it is what it looks like, the government officials that ordered/organised the evacuations should be harshly censured and the next time evacuation orders should be more risk-based and executed in a safer way. What little I've gleaned suggests an appalling situation where a bunch of presumably old people were forced from their homes to their deaths. The main thing keeping me quiet on the topic is I don't speak Japanese and I don't really know what happened in detail there.

[drtgh]

Did you read the report I put? the pdf,

    << The Fukushima Daiichi Nuclear Power Plant construction was based on the seismological knowledge of more than 40 years ago. As research continued over the years, researchers repeatedly pointed out the high possibility of tsunami levels reaching beyond the assumptions made at the time of construction, as well as the possibility of reactor core damage in the case of such a tsunami. However, TEPCO downplayed this danger. Their countermeasures were insufficient, with no safety margin.>>

    << By 2006, NISA and TEPCO shared information on the possibility of a station blackout occurring at the Fukushima Daiichi plant should tsunami levels reach the site. They also shared an awareness of the risk of potential reactor core damage from a breakdown of sea water pumps if the magnitude of a tsunami striking the plant turned out to be greater than the assessment made by the Japan Society of Civil Engineers.>>

Even leaving aside they ignored the original placement in order to reduce costs by using biased seismological reports of their convenience, TEPCO knew the plant was at risk, they was warned successively it was at risk. And the supposed regulator NISA [0] closed the eyes conveniently (conveniently for someones).

    << TEPCO was clearly aware of the danger of an accident. It was pointed out to them many times since 2002 that there was a high possibility that a tsunami would be larger than had been postulated, and that such a tsunami would easily cause core damage.>>

From the other url I put (I updated it with a cached url, I didn't noticed the article was deleted),

    << there appear to have been deficiencies in tsunami modeling procedures, resulting in an insufficient margin of safety at Fukushima Daiichi. A nuclear power plant built on a slope by the sea must be designed so that it is not damaged as a tsunami runs up the slope.>>

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

> the gentlest engineering disaster

EU raised the maximum permitted levels of radioactive contamination for imported food following Fukushima, this is not a gentlest gesture to the Europeans. Japanese citizens also received their dose, at time the more vulnerable ones was recruited by the Yakuza to clean up the zone.

[roenxi]

> Did you read the report I put?

No, I'm just trusting that you'll be honest about what it is saying. I don't need to read a report to persuade myself that a 40 year old plant was designed based on the best available knowledge of 40 years ago. That seems like something of a given. I'm just not sure where you are going with that, it doesn't obviously suggest negligence to me.

You're not saying what tolerances you want them to design to. We both agree that there are scenarios that can and might happen. Obviously is is possible for a tsunami to take out buildings built near the shore in Japan so it doesn't surprise me that people raised it as a risk. A lot of buildings got taken out that day. That doesn't obviously suggest negligence to me; obviously a lot of people were happy living with the risk.

> EU raised the maximum permitted levels of radioactive contamination for imported food following Fukushima

Oh well then. I had no idea. I thought the consequences were minor and now I have learned ... there you go, I suppose. I'm not really sure what to do with this new information.

[drtgh]

> I'm just not sure where you are going with that, it doesn't obviously suggest negligence to me.

You didn't read the report or search for information about the matter, but I have not problem to repeat it for you,

The General Electric's design was originally designed to be placed 30-35 meters above the ocean, instead of this TEPCO modified such design and constructed at sea level (almost) recurring to studies convenient to their purpose, cheaper, this in one of the more tsunami-prone countries, with an history of ones reaching 20-30 meters. When those -for them- convenient studies was not longer justifiable, as deeper studies did finally refute them, they decided to just keep ignoring all the warnings and requests to reinforce the safety. They knew the nuclear plant was in danger, they always knew it, General Electric didn't designed at 30-35 meters above the ocean by coincidence, and this happened with a supposed regulator always closing the eyes to this, conveniently, across those years, ignoring even pipes with fissures.

Well, this obviously suggest negligence to me. Decades of bad decisions with a strong smell to corruption.

> You're not saying what tolerances you want them to design to.

What about tolerance to avoid a meltdown of the core, specially under two events, an earthquake and a tsunami, exactly what happened after ignoring the warnings and requests to reinforce the safety.

> Oh well then. I had no idea. I thought the consequences were minor and now I have learned ... there you go, I suppose. I'm not really sure what to do with this new information.

Keep the sarcasm for other places, if you don't mind. It is not a mere gentlest engineering disaster as it reached the whole planet, with ate TEPCO's cesium-137, specially the Japanese. And it is not a mere gentlest engineering disaster when you have to force vulnerable people to go to ground zero to move contaminated land and water.

[roenxi]

> What about tolerance to avoid a meltdown of the core, specially under two events, an earthquake and a tsunami, exactly what happened after ignoring the warnings and requests to reinforce the safety.

I wasn't going to reply but that seems like it moves the conversation forward; so why not?

It seems to me your design goal is fundamentally incompatible with a lot of the specific complaints of negligence. If you want a design that doesn't melt down when there is an earthquake and a tsunami, then moving the reactor to higher ground isn't helpful because it won't achieve the design goal. The design is still fundamentally vulnerable. Moving the reactor up 35m still leaves it vulnerable to a large enough tsunami and a big enough earthquake.

If your solution is moving the site uphill, then your design goal should be talking in terms of a 1 in X year event. If you want the risk completely mitigated then in this case it isn't relevant where the site is since the obvious way to achieve that design goal is just build something that doesn't fail when flooded. Coincidentally that seems to be the approach that the newer generation designs use - change how the cooling works so that it can't melt down in any reasonable circumstances, tsunami or otherwise.

I will note that there is a reading of your comment where you want the design to be able to tolerate this specific event. I'm ignoring that reading as unreasonable since it requires hindsight, but in the unlikely event that is what you meant then just pretend I didn't reply.

> Keep the sarcasm for other places, if you don't mind. It is not a mere gentlest engineering disaster as it reached the whole planet, with ate TEPCO's cesium-137, specially the Japanese. And it is not a mere gentlest engineering disaster when you have to force vulnerable people to go to ground zero to move contaminated land and water.

Which one do you think was gentler and a story of similar popularity as Fukushima? It is pretty usual to have multiple people actually die and it be the engineer's responsibility once something becomes international news. Even something as basic as a port explosion usually has a number of missing people in addition to a chunk of city being taken out. To anchor this in reality, Fukushima at a class 7 meltdown might have done less damage than a coal plant in normal operation. Coal plants aren't pretty places and air pollution is nasty, nasty stuff.

[cpgxiii]

> Caveating that I'm not really sure it was even an out-of-design event but if it was then it is case closed and the swiss cheese model is an inappropriate choice of model to understand the failure.

This is not how safe systems are designed and operated. Safety is not a one-time item, it is a process. All safety-critical systems receive attention throughout their operating lives to identify and mitigate potential safety risks. Throughout history, many safety-critical systems have received significant changes during their operating lives as a result of newly-discovered threats or recognition that threats identified during the initial design were not adequately addressed. Many (if not most) commercial aircraft have required significant modifications to address problems that were not understood at the time they were initially built and certified. Likewise, nuclear power plants in many countries have received major modifications over the years to address potential safety issues that were not understood or properly modeled at the time of their design. Sometimes, this process determines that there is no safe way to continue operation - usually that there is no economically viable way to mitigate the potential failure mode - and the system is simply shut down. This has happened to a few aircraft over the years, as well as several nuclear power plants (in many cases justified, in others not so much).

Fukushima existed in just such a system, and that the disaster occurred was the result of failures throughout the system, not a one-off failure at the design stage.

> I mean, ok. So say they build the plant 35m higher up, then get hit by a tsunami that is 36 meters higher [0] than the one that caused the Fukushima disaster? If we're going to start worrying about events outside the design spec we may as well talk about that one. If they're designing to tolerate an event, we can pretty reliably imagine a much worse event that will happen sooner or later and take the plant out. That is the nature of engineering.

I think you are missing the point. Obviously it is possible that a tsunami higher than any possible design threshold could occur (it is, after all, possible that an asteroid will strike in the pacific and kick up a wave of debris that wipes everything off the home islands). However, the tsunami that struct Fukushima Daiichi was no higher than a number of tsunamis that were recorded in Japan within the last century. The choice of DBA tsunami height was clearly an underestimate, and underestimates were identified for Fukushima and other plants prior to the accident but not acted upon. This was not a cases of "a bigger wave is always possible", it was a case where the design, operation, and supervision were wrong, and known (by some) to be so prior to the accident.

[roenxi]

> The choice of DBA tsunami height was clearly an underestimate, and underestimates were identified for Fukushima and other plants prior to the accident but not acted upon.

Not much of a swiss cheese failure then though. The failure is just that they committed hard to an assumption that was wrong.

My point is that unless it is actually an example of multiple failures lining up then this is a bad example of a swiss-cheese model. Seems to be an example of a tsunami hitting a plant that wasn't designed to cope with it. And a plant with owners who were committed to not designing against that tsunami despite being told that it could happen. It is a one-hole cheese if the plant was performing as it was designed to. The stance was that if a certain scenario eventuated then the plant was expected to fail and that is what happened.

Swiss cheese failures are there are supposed to be a number of independent or semi-independent controls in different systems that all fail leading to an outcome. This is just that they explicitly chose not to prepare for a certain outcome. Not a lot of systems failing; it even seems like a pretty reasonable place to draw the line for failure if we look at the outcomes. Expensive, unlikely, not much actual harm done to people and likely to be forgotten in a few decades.

[icehawk]

I don't think you understand how a swiss cheese failure happens. They're not independent or semi-independent. Latent failures, expose active failures, like:

"Committed hard to an assumption that was wrong"

Then causes damage to the seawater pumps along the shoreline, and flooded emergency diesel generators.

That causes total loss of AC and DC power.

Loss of AC and DC power causes the reactor to overheat.