Nuclear Plant Accidents: Sodium Reactor Experiment
allthingsnuclear.org
allthingsnuclear.org
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...
"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.
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?
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.
Sounds interesting. Got a reference?
Wow! Thanks for the link.
> Erst nach einer weiteren Abklingzeit von mindestens 60 Jahren soll der AVR-Behälter schließlich von Robotern zerlegt werden und in ein Endlager überführt werden.
https://de.wikipedia.org/wiki/AVR_(J%C3%BClich)#R.C3.BCckbau...
'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.
It still sounds like a very extreme situation.
Apparently until that reactor no one realized the radiation can reflect off the air and reach the surroundings.
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.
irresponsible
Helium-cooled reactors leak helium
Most of the problems with Fort St. Vrain, the US's only helium-cooled reactor, were due to moisture infiltration: https://en.wikipedia.org/wiki/Fort_St._Vrain_Generating_Stat...
How's your design work without coolent? Or when something other than helium becomes coolent? Or ... ?
It's that "... ?" question that's the crucial one. The unknown unknowns.
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.
1: http://www.ucsusa.org/sites/default/files/legacy/assets/docu...
The pipes with coolant will rupture, and from there Polonium-210 will be released into environment.
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.
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.
https://en.wikipedia.org/wiki/Santa_Susana_Field_Laboratory#... http://www.latimes.com/business/hiltzik/la-fi-hiltzik-201406...
Inviting Disaster: Lessons From the Edge of Technology: https://www.amazon.com/gp/product/0066620821
https://www.amazon.com/Atomic-Accidents-Meltdowns-Disasters-...
On a lower scale it's like (repeatedly) rebooting the PC when it's misbehaving.
Oops."
I'll lead myself out.
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 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.
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.
But yeah, dam away!
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.
Second dredging actually works and is vastly cheaper.
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.
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.