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Comment by newacct583 | Hacker News Reader

Or an attack, of course. Or some other event (social unreset, invasion, coup, etc...) causes an evacuation of staff and it boils off during the resulting excursion.

People tend to have poor mental models for the long tail of external failures that happen in real life. It's easy to imagine that things that have never happened in the last century would Never Happen. But... they will, somewhere.

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Nuclear sites are designed to withstand a strike from a commercial airliner (747). Like you, the designers imagined many of the events you mentioned and more. A good rule of thumb is that if you, a non-expert, can think of a scenario within 10 minutes, an expert has probably already thought of this scenario. Nuclear power plants and weapons sites have always been considered targets and thus considered extra scrutiny in their design.

Wow. How do they design them to withstand a strike from a 747? That seems really difficult.

A whole lot of concrete, mostly.

They shot an F4 target drone at a block of "reactor grade" concrete wall back in the 80s and they took measurements and did science on the resulting lack of damage and concluded that a reactor can shrug off one of anything. They didn't change containment buildings to be plane proof. It's just a side effect of the design required to contain a melting down reactor with a sufficient safety factor.

video of the test https://www.youtube.com/watch?v=F4CX-9lkRMQ

Yes. A NRC requirement for utility scale reactors after 9/11. One wonders why nuclear reactors are so expensive.

It's a good reason to design reactors to be as small as possible, with a small containment building. Much easier to build.

You'd hope so. Reactors yes, but not spent fuel pools. Everyone misses things. I've found 3 design flaws myself in the industry. Not too big of a deal as actions can be taken to mitigate some of the flaws. The other flaws are less probable of causing an issue due to redundant and diverse systems but there's always the off chance...

>but not spent fuel pools. Everyone misses things

Everyone who remembers the post 9/11 "but what if the terrorists attack X" pandemonium knows that spent fuel pools are outside the containment building. That was one of the scenarios that got paraded around to maximize FUD.

I was involved in closing of case, when terrorists wanted to create dirty bomb and throw it at Ukraine. S*it happens.

Wanted to is very different than doing. As far as I'm aware there has never been a dirty bomb attack. You could effectively create a dirty bomb with less radiation with more easily obtainable materials (still pretty expensive and labor intensive). The threat would be similar to a more radioactive substance because the biggest damage is the fear (that's what terrorism is about. They could do MUCH more _damage_ if they weren't as concerned about striking fear). The reason it hasn't been done is because it is impractical and difficult to do without killing yourself. There's better and far easier ways to strike fear into people's hearts. Killing a single person is more effective for them than increasing the chance of getting cancer in one's lifetime by 10% for a dozen people. The much bigger threat is a briefcase nuke but that is several more orders of magnitude difficult/expensive to obtain.

There is plenty of people which want to kill themselves for few, but common reasons, like cancer. It's not a stopper for terrorists.

NuScale claims "The reactor building is able to withstand aircraft impact". The reactors and spent fuel pool are in the same room:

https://www.researchgate.net/figure/Cut-away-view-of-reactor...

https://interestingengineering.com/crashed-jet-nuclear-react...

> the designers imagined many of the events you mentioned and more

Designers are awesome. Sadly they were also unable to find some time in 50 years to raise a wall a few m so it can stand a Tsunami. It seems that the extra scrutiny, was not so extra in the real life when the company will need to allocate real money.

The event you are referring to was also a freak event. The Tohoku earthquake was the 4th largest _ever_ recorded and the largest ever recorded in Japan (by 0.2M, it is a log scale btw). The closest earthquake to that, in the region, in the previous 100 years was 0.7M lower (and the 6th largest ever recorded, in the area). The Tohoku earthquake also resulted in one of the largest tsunamis ever recorded.

We should note that a lot of rare things happened all at once, more than just the freak earthquake and freak tsunami. There is no such thing as perfect. But consider that there were no lives lost due to the reactor accident. Yes, there is economic damage, but that is the worst. Lives were not lost and the environment was not irreparably damaged. Nature has actually started to take back the region and it more looks like a scene out of I Am Legend rather than The Road or The Book of Eli. I do not intend to dismiss the event, as it is concerning (and we've learned a lot since then), but however you measure it coal or oil or gas have had far greater environmental (or human/health) impacts than nuclear. The difference is that it is more in our mind. Despite the Fukushima cleanup estimate (2x Chernobyl's) costing about 9x Deep Water Horizon (2010) I'll let you decide what costs more[0], even if we ignore all the costs to health and atmosphere. There simply is no free lunch.

[0] https://ourworldindata.org/oil-spills

There’s no free lunch but wind and solar are a hell of a lot cheaper than this.

Economically cheaper, but that isn't the only factor that we're discussing. We're also talking health and environmental.

> consider that there were no lives lost due to the reactor accident.

Repeating this again is infuriating. No lives lost? seriously?

> "The event you are referring to was also a freak event. The Tohoku earthquake was the 4th largest _ever_ recorded and the largest ever recorded in Japan"

There is no doubt that the 2011 earthquake was an extreme event, but it's incorrect to say that it was not foreseeable or that the plant's safety systems could not have prevented the disaster.

Further up Japan's coast, the Onagawa nuclear plant was much closer to the earthquake's epicentre. It was subjected to extreme shaking, far more than any other nuclear plant in history, and like Fukushima was also flooded by the tsunami.

Yet it was able to shut down safely as designed in the hours that followed, and its structure was "remarkably undamaged" considering the extreme magnitude and duration of the shaking. 2 of its 3 reactors are expected to be restarted soon following structural repairs and seismic upgrades.

I am not trying to say that things couldn't be designed better. They could (that is never _not_ true). But it is also important to remember that this was a crazy accident as well and several uncommon things had to go wrong at once. The reactor was designed to withstand 100 year earthquake and tsunamis (that's equivalent to flipping almost 7 heads in a row) (we're also not accounting for the odds of the tsunami). But what I am suggesting is that there is a limit. Sure, we could foresee 100 heads landing in a row, it is certainly possible, but at the end of the day you have that end up with an acceptable amount of risk. I do not think 100 year events (1:99 probability) is correct as climate change is changing those odds, but it isn't like this was engineers being lazy and dumb. You are using post hoc analysis to justify actions made without that knowledge. As they say, hindsight is 2020. I do want to remind you that this was the largest earthquake to EVER hit Japan. That's much harder to predict and extremely reasonable to believe such an event is unlikely during the expected lifetime of the reactor.

You don't even need a tsunami, as a plain immaterial "cascade" can wreak havoc: https://en.wikipedia.org/wiki/Forsmark_Nuclear_Power_Plant#J...

> an evacuation of staff and it boils off during the resulting excursion.

It is trivial to design a system that powers off when unstaffed. Without power, this reactor will SCRAM and passively switch to air cooling over the course of a month.

Presumably, a skilled attacker could compromise the passive safety systems and force a meltdown, but wouldn't it be easier to steal some spent fuel and disperse it?

Once an attacker is inside the plant, with just some Wiki knowledge, any plant is as good as melted down. It's a much better plan to simply drain the spent fuel pool.

I think it takes a bit more than Wiki knowledge to drain an in-ground pool... you would need to keep a large pump running for hours, under duress.

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