At least they didn't have a sodium fire. Monju (Japan) and Clinch River (US) both had sodium fires.
The U.S. Navy tried sodium reactors in the early days. In addition to Nautilus, the first nuclear submarine, they also built USS Seawolf, with a sodium-cooled reactor. Seawolf worked, but was enough of a headache that its reactor was replaced with a Nautilus-type pressurized water reactor. The US Navy didn't try sodium-cooled reactors again. Rickover on sodium-cooled reactors: "expensive to build, complex to operate, susceptible to prolonged shutdown as a result of even minor malfunctions, and difficult and time-consuming to repair."
The USSR tried sodium-cooled reactors, with moderate success.[1] They had leaks and fires too. One big reactor had 39 leaks over the years, none catastrophic. In the last 15 years of operation, none. Eventually they found all the construction defects.
Basic truth: complexity in the radioactive parts of a nuclear reactor causes trouble. Sodium reactors have fires. Pebble-bed reactors have pebble jams. (There's one in Germany that can't be unjammed or decommissioned.) Helium-cooled reactors leak helium. The nice thing about water-cooled reactors is that the complexity is on the outside, where repairs are possible. This is why new fancy reactor designs are viewed sceptically in the industry. You can't have any problems inside the reactor vessel, because you can't fix them.
More info: [1] Most of the pebbles were removed through the fueling system, but broken pebbles and dust remain, all highly radioactive. Bits of broken pebbles are jammed into crevices in broken graphite. "The reflector bottom of the core cavity is funnel shaped, with an inclination of 30°, ending in the 0.5 m wide vertical fuel discharge tube. In that geometrical setting it could simply be assumed that all pebbles must have rolled into the discharge tube and that there was no need for an inspection. The reflector bottom, however, contains many slits for coolant penetration, 3.4 cm wide and in radial orientation. A piece of broken pebble could have stuck in such a slit, and, standing out, one or more pebbles might lay behind it guided by the slit like by a rail."
"An upper limit of 197 fuel pebbles, respectively fuel pebble equivalent in form of broken pieces, has been evaluated to be residual in the reactor vessels containing an upper limit amount of 98g of fissile material."
"AVR has most probably the strongest β-contamination, and in the worst form, of all nuclear installations world wide".
This is why complexity in the radioactive portion of the system is strongly undesirable. If anything goes wrong, dealing with it is extremely expensive, difficult, and dangerous.
It is often exhausting arguing with overly enthusiastic people claiming certain reactor designs aren't just safer but "inherently safe". All operations with massive energy releases are inherently unsafe. That's just thermodynamics at work, and the reason we still have fire brigades after millennia of using fire. What makes a difference with nuclear is the energy concentrations and the material hazard involved. The problem from your citation is a subtle and arguably minor engineering oversight which wouldn't be much of an issue to handle on say a coal plant. Nuclear however multiplies the consequences of any design defect.
I believe thats why certain molten salt reactors do away with any complexity in the reaction chambers - some designs are planned to operate with fuel dissolved in the salt. Criticality comes from the shape of the reaction chamber vessel. Worst kind of failure mode - fuel cell rupture/core meltdown are not really possible - simply because those are the normal operating procedure. Should anything go really wrong the molten salt/fuel mix should melt emergency reliefs and drain into non-criticality vessel.
I do not remember the nitty-gritty details and can't find it now, sorry.
Now imagine the emergency drain failure, due to a quake seismic shift, massive explosion nearby or a construction worker forgetting his helmet in. What's the plan B?
Rely on gravity and put the non-critical tank underneath the critical tank. Make sure to make the critical tank a much lower melting point than the non-critical tank. Burst diaphragms (well, low melting point plugs, like steam boilers have used for a few centuries now).
Possibly you're confusing "inherently safe" with "it can't break or become uneconomical". Also talking about inherently safe plants, usually they're talking physics, an inattentive enough electrician could probably find a way to put his hand across the output of an alternator, there's just nothing "nuclear" about those kind of accidents other than the worksite happening to be a plant.
Inherently safe just means you can't have a Chernobyl because water doesn't burn as well as charcoal. Its inherently very difficult to set PWR moderator on fire (water) compared to the Chernobyl experience (graphite, more or less purified coal). Although its against the spirit of the linked article, the PWR "near" my house inherently can't have a sodium leak because it doesn't use sodium as a coolant.
All heat engines lose coolant, no seal is perfect. Even if your primary coolant loop is perfect, you still have to evaporate a heck of a lot of water in the secondary loop just to get rid of the heat. This pdf[1] quotes 600-800 US gallons per MWh. Even shut down the core is producing megawatts of heat.
If an operating helium-cooled reactor loses all its coolant, you're going to have a bad day, but the same thing can be said about a water-cooled reactor.
Do I understand that correctly from that page that the reactor was completely unshielded at the top, and they just relied on the fact that people wouldn't be there? That seems completely mad. The past is a weird place.
I was chatting with an industrial radiographer who used to image tanks, looking for stress fractures in the armour plate. They could only do thiamin clear days at the bottom of a quarry as the radiation dose in a nearby town was notably higher if it was cloudy. All hearsay, by possibly relevant.
That one has always amazed me. A nuclear reactor just sitting in open air! Moderated by a flammable material! And then everyone is shocked, shocked! when it catches fire.
But at least Windscale and the others had the excuse of being military projects. I'd have hoped a civilian reactor would be at least marginally sane.
> There exists currently no dismantling method for the AVR vessel, but it is planned to develop some procedure during the next 60 years and to start with vessel dismantling at the end of the century.
I had also not heard of this. The English article makes it sound like it's going to take 60 years to invent a way to decommission the reactor, but the more detailed German article on the same topic says
> Erst nach einer weiteren Abklingzeit von mindestens 60 Jahren soll der AVR-Behälter schließlich von Robotern zerlegt werden und in ein Endlager überführt werden.
'not until after a further decay period of at least 60 years will the AVR vessel finally be taken apart by robots and transported to a final disposal location'
So it seems that the 60 year period isn't specifically to allow for the invention of a decommissioning technique for this site, but primarily to allow the radiation levels inside to diminish.
I have a bit of a connection with this incident, I grew up in Simi Valley, not far from Los Angeles; it is not an academic subject to me. In short, they built a defective reactor in a warehouse a few miles away from several cities and covered it up when it exploded.
A number of workers and their spouses (known by my parents) died early in their 40s from cancer ostensibly due to contamination. There is a belief in increased birth defects in the area, but I can't find anything to cite right now.
The shame is that we used to be proud of having rocketdyne nearby, testing rocket engines and such, which we could hear from our school yards. Little did we know how reckless they were, and had had a meltdown a few years prior.
I find various accounts of nuclear accidents fascinating because, as the intro of the article alludes to, they often involve complex systems undergoing complex failure scenarios.
Then there's SL-1 (https://en.wikipedia.org/wiki/SL-1). That was a really stupidly simple failure, but of all the accidents I've read about I find it the most poignant reminder of why nuclear reactors are such complex systems in the first place.
But it was well documented that you shouldn't lift that one rod above point X. Maybe the message didn't sink into the guy, maybe he screwed up, they even wonder if he committed suicide. Its big message was to eliminate all possible single points of failure, especially ones controlled by fallible humans, even at the cost of increased complexity.
It should be noted that reactivity control in military and commercial PWRs is fundamentally different. That said it's hard to understand how the SL1 operator managed to yank the rod so far out of the core. The procedure was to withdraw each rod 4 inches and attach it to the crdm, which in itself is a little mind blowing to me. The rod was withdrawn 26 inches and prompt criticality was achieved at 23 inches or so. The rod weighed 86 pounds. Even if it was stuck it's hard to imagine yanking something that heavy that far to unstick it.
Santa Susana is notorious for a dangerously cavalier attitude about chemical safety. For years they burned toxic chemical waste in open pits. They filled barrels and shot them with rifles until they exploded. One person was killed in 1994. They disposed of sodium coated parts by letting them burn in the same open-air pits.
I'm always surprised that the CANDU[1] reactor isn't more popular, as you don't require uranium enrichment, can use a mix of fuels, and has a number of fail-safes that work without power -- such as gravity-dropped control rods into the low pressure chamber, and requiring the moderator (deuterium in the original models) to be present to maintain a reaction.
Kind of weirdly disingenuous that the article says "the workers" did this and "the workers" did that. What, was management completely absent for a period of months, and a bunch of yokels were just randomly flipping switches?
If "a worker" was overriding a failsafe, it's because right behind him a supervisor was telling him they had to get the plant back online, or else he'd be fired.
I think you are being just as disingenuous. Without knowing the processes, we have absolutely no idea what the decision chain looks like. I can think of many emergency situations where I would want workers who are close to the problem to make judgement calls. Even if they make the wrong call, at least the chance of success was optimised.
I often notice a bias amongst some people that they think management is more susceptible to caving in to pressure for "success" (success being measured by getting a job done quickly/cheaply, etc). In reality, I think it's just a human condition.
Imagine working in a shop where every move you make is scrutinised. If you get something done fast, everyone assumes that you cheated somehow or that you did an exceptionally poor job. People always doubt you and assume that you are on the take somehow. This would be pretty dysfunctional.
Now imagine working in a situation where when you do work everyone assumes that it is of high quality. They don't have to check it because they know you are capable, hard working and reliable. If you get it done more quickly than expected, it's because you are a genius and should be promoted.
People often try to build companies like the latter. The problem is that it's very easy to let your standards slide. If you do poor work very quickly you get congratulated and rewarded. If you do good work very slowly, nobody looks at it, nobody understands the quality and everyone complains that you took a long time.
If you are in management, it's even worse. If you check up on the quality of work of your workers: 1. They are upset that you don't trust them. 2. If you find problems, it only causes you headaches and makes you look bad because nobody understands quality at all. They just think everything is wonderful and if you bring up a problem, then it's because you are the worst manager on the team! It's really easy to close your eyes and reward poor work.
What I find really interesting is that on teams where there is absolutely no pressure to deliver, conversely programmers often imagine pressure from management to deliver quickly. Again, it's because nobody sees the quality of their work and the only thing they see being evaluated is the speed with which they deliver.
In the end, management must take responsibility when workers make mistakes. Maybe the wrong people were hired. Maybe there was a lack of training. Maybe the social dynamics were poor. It doesn't matter.
However, it is also possible that workers made the wrong choice, but that the system still allowed the choice with the highest chance of success to be made (given the information that they had). You are never guaranteed to have success. Even when workers and management do an excellent job, sometimes you fail because of something you didn't realise at the time. In that vein, I wouldn't assume that "the workers did X" is an indication that they were incompetent. Nor would I assume that management pressured them into doing something stupid.
Nuclear electric power production carries risks, which are outweighed by the expectations of lives saved by reducing air pollution and greenhouse gas production.
Clearly it's better to spew the radioactive waste randomly into the air, like our existing coal plants do. The solution to pollution is dilution, right?
> Clearly it's better to spew the radioactive waste randomly into the air, like our existing coal plants do.
While coal plants do emit more radioactivity through the chimney than nuclear plants, that radioactivity pales in comparison to that emitted by both the nuclear waste and accidents of the latter. See http://skeptics.stackexchange.com/questions/1018/do-coal-pla... for sources.
Also, nobody said coal and nuclear are the only possible technologies for creating electricity.
What matters isn't how much pollution is released. What matters is the harm and suffering it causes. Nuclear has a long, long way to go to catch up with carbon-based fuels in that regard.
I disagree that nuclear waste is a problem. To the extent that it is a problem, the solution is stupidly simple: store it in Antarctica where no technologically-illiterate humans can possibly come into contact with it, and where we can reclaim it later if/when we need it.
Also, nobody said coal and nuclear are the only possible technologies for creating electricity.
They're what we have to work with. Renewable sources should be aggressively explored and developed, but they are currently not sufficient by themselves.
Presumably you mean the risks are outweighed if better options aren't available. For example hydro is a good option if your power needs aren't too high and population quite small.
...and you don't care about destroying the habitat of anything upriver, or anything that needs to get downriver/upriver (spawning fish), or anyone that relies on those critters.
And you don't mind that it's not a long-term solution, as silt builds up behind the dam until your dam is worthless.
> And you don't mind that it's not a long-term solution, as silt builds up behind the dam until your dam is worthless.
You can let some of the water flow take silt away, at least the silt anywhere near the dam. That might mean you don't have a huge reservoir, but you can generate a lot of power without a reservoir at all.
Nuclear power warms water which is then usually dumped into rivers at a temperature higher than it started at. The waste issue is problematic and the cost (especially when factoring in cleanup and waste) is prohibitive to a small country with no existing nuclear program. Our dams gave been in a while here in New Zealand and the trade offs they require are vastly more acceptable to New Zealanders than the nuclear option.
The U.S. Navy tried sodium reactors in the early days. In addition to Nautilus, the first nuclear submarine, they also built USS Seawolf, with a sodium-cooled reactor. Seawolf worked, but was enough of a headache that its reactor was replaced with a Nautilus-type pressurized water reactor. The US Navy didn't try sodium-cooled reactors again. Rickover on sodium-cooled reactors: "expensive to build, complex to operate, susceptible to prolonged shutdown as a result of even minor malfunctions, and difficult and time-consuming to repair."
The USSR tried sodium-cooled reactors, with moderate success.[1] They had leaks and fires too. One big reactor had 39 leaks over the years, none catastrophic. In the last 15 years of operation, none. Eventually they found all the construction defects.
Basic truth: complexity in the radioactive parts of a nuclear reactor causes trouble. Sodium reactors have fires. Pebble-bed reactors have pebble jams. (There's one in Germany that can't be unjammed or decommissioned.) Helium-cooled reactors leak helium. The nice thing about water-cooled reactors is that the complexity is on the outside, where repairs are possible. This is why new fancy reactor designs are viewed sceptically in the industry. You can't have any problems inside the reactor vessel, because you can't fix them.
[1] http://www-pub.iaea.org/mtcd/meetings/PDFplus/2009/cn176/cn1...