Long article, but the best one I've run across explaining the inputs used to choose design tolerances, the advances in those methods over the years, and where the Fukushima design and later maintenance was and wasn't in accordance with best practices.
The overall conclusion is that it was known by the early 2000s that the plant's worst-case tsunami estimate, used as its design basis, was no longer sufficient, given improved understanding of tsunamis. At that time, a significant upgrade should have been initiated, since the original design-basis tsunami of 3.1 meters was no longer believed to be a good estimate of the worst case. But those reports basically got buried and nothing was acted on.
Side note: I was wary of submitting, because we've just had a big round of Fukushima and nuclear discussion/debate, and rehashing the same debate in another thread doesn't seem productive. But imo this article is quite informative and worth a read.
I don't know Japan's geography, so, maybe it is possible for it to have tsunamis everywere. However, if there is some part of Japan's territory that is safe from tsunamis, wouldn't it be easier to just build those reactors there, and not in a place that is known to have tsunamis since, at least, the year 684 AD?
I haven't read the OP article, yet, but as I vaguely recall from past media reporting on the topic, I believe one of the reasons such sites were chosen is that the were economically fairly poor. The jobs were welcome and outweighed residents' safety concerns. (Perhaps safety concerns were also somewhat diminished by said residents having on average a lower degree of independent information and/or education.)
This is from memory; feel free to correct me if and as I'm wrong.
Such approaches can also be spun positively as "economic development packages/projects". Whenever such is said, the observer should look critically at who is really benefiting -- as often as not, I think, the project owners' interests come ahead of, and sometimes at the cost of, those of local residents.
Ideally, all parties gain. But to do so, amongst other things someone has to keep those in power from cutting too many corners.
I believe due to the need for cooling water nuclear reactors are almost always built on a large body of water, either a lake or the ocean. I believe the only reactor in the world that isn't built in such a location is the Palo Verde station in Arizona, which uses (partially treated) municipal sewage for its cooling needs: http://en.wikipedia.org/wiki/Palo_Verde_Nuclear_Generating_S...
I don't think it's really relevant. The point is not that there is a way to have safe nuclear energy, the point is that the worst case scenario is catastrophic, and that I don't trust any company or government to do what's necessary, especially if they're strapped for cash.
You can dramatically slow reactors down, but you can't actually 'shut down' because simply decay produces significant amounts of heat. So the real problem at Fukushima was the need to be able to passively cool a reactor indefinitely in that 'slow' state without human interaction and that's where they failed. Sure, if they had power and none of the connectors had failed it would have also been ok, but without long term passive safety nuclear power is not safe.
I should have been more clear, a lot of designs passively cool the reactor / primary loop, but they don't have long term 100% passive cooling on the secondary loop. Though a counter example would be welcome.
Claims 72 hours of passive heat dissipation -- the heat sinks are [giant] tanks of water inside the containment building.
The HN article mentions a passive cooling system in Fukushima Daiichi #1: a gravity-driven steam condenser (footnote #5). It failed when electric batteries failed, because it needed DC electricity to open valves. (I think this isn't the case in ESBWR).
The systems with limited functionality in the absence of power were an isolation condenser (in unit 1) and a reactor core isolation cooling (RCIC) system (in units 2 and 3). An isolation condenser takes steam from the reactor core, passes it through a tank of water to cool and condense it, and then feeds it back as water into the reactor pressure vessel. The flow is gravity driven (i.e., no pumps are needed). The system in unit 1 had a thermal capacity of about eight hours.
The worst case scenario of a natural disaster is also catastrophic, and they don't even have significant benefits. Nuclear power does, as it doesn't produce greenhouse gasses, and reduces dependence on fossil fuels. And like the other comment said, new types of reactors are completely different and we shouldn't have an irrational fear of nuclear power in general because of accidents like this.
I think the key is that they already had the hindsight years before the accident occurred. They knew, from incidents at other plants and from tsunamis in other areas that the assumtions made when the plant was designed were wrong and the plant was vulnerable. They chose not to act on that knowledge.
oh boy. can we just please deal with the reality of now? I can't stand these glum little articles ala how xyz could have been prevented, or, what steve jobs would have done different. all these futile/meaningless intellectually masturbatory what-ifs that contribute zero to the tragedy over there as we fiddle around about it from our privileged vantage point. move on!
My jaundiced view of civilian nuclear power is still colored by one of my most vivid experiences in the Navy nuclear reactor program. It came in the course of prepping for the [chief] engineer's exam, after two years of sea duty running reactor plants aboard an aircraft carrier. That in turn had followed a year of intensive academic and practical nuclear propulsion training.
Our "coaches," all senior nuke officers, had us work through the details of some what-if scenarios. Funny thing, we didn't seem to have covered those particular scenarios in our initial training.
It was pretty scary; to this day I'm not convinced that conventional-design civilian nuclear reactors belong anywhere near population centers.
What worried me wasn't the technology itself, but the human fallibility. In the Navy nuclear program, we had the occasional [foul]-up even though we were ferocious about doing things right. We used checklists for everything, even though we were required to have memorized practically every procedure, especially emergency procedures. (In an emergency, the first thing you did was to take the "immediate actions" to put the plant in a safe condition. The second thing you did was to get out the appropriate checklist and start working through it with your watch team.) We second-checked each other's work, and both the worker and the second-checker had to sign off on the work. Noncompliance with the prescribed safety procedures (and with the prescribed serious attitude) was guaranteed to get you in big trouble. The Navy systematically collected and disseminated lessons learned from throughout the nuclear fleet, and every nuclear ship's nuke operators routinely trained on those lessons. All this derived from the tone at the top, set early on by Admiral Rickover.
Both Three Mile Island and Chernobyl were caused (so far as is publicly known) by cascading human errors; apparently the same was true at Fukushima. I have no experience whatsoever in the civilian nuclear industry, but these accidents have reinforced my doubts about whether a civilian work force, even one heavily populated by ex-Navy types, can achieve the kind of zero-defect culture we strove for in the Navy.
The American nuclear navy is one of the classic examples of what process safety experts call a High Reliability Organisation. HROs are organisations that run dangerous systems susceptible to so-called "Normal Accidents" while having fewer such accidents than their competitors.
The main things that have been found to contribute to HROs are: A chronic sense of unease even in the face of normal operations - always be thinking of ways to improve safety. A separate engineering standards organisation that is not responsible for operations - i.e. they can order shutdowns without affecting their own job objectives in a way that a plant manager cannot. They do not tolerate the so-called "normalisation of deviance" (which is when out-of-range behaviour becomes accepted as people get used to it.).
Nuclear power has been in widespread civilian use in the West for over 50 years without a single nuclear-related fatality to a member of the general public (Chernobyl was a crap design that was never approved in the West). Plant workers have been killed and injured, yes, but even if you take them into account, the safety record for nuclear is still much better than any other source (coal mining isn't the safest job in the world, nor is working in oil and gas fields).
You know what worries me? The 75 million people who live downstream of the Three Gorges Dam.
"We don't understand the world as well as we think we do and tend to be fooled by false patterns. We mistake luck for skills (the fooled by randomness effect), overestimate knowledge about rare events (Black Swans), as well as human understanding, something that has been getting worse with the increase in complexity." Nassim Taleb
27 comments
[ 3.4 ms ] story [ 63.4 ms ] threadThe overall conclusion is that it was known by the early 2000s that the plant's worst-case tsunami estimate, used as its design basis, was no longer sufficient, given improved understanding of tsunamis. At that time, a significant upgrade should have been initiated, since the original design-basis tsunami of 3.1 meters was no longer believed to be a good estimate of the worst case. But those reports basically got buried and nothing was acted on.
Side note: I was wary of submitting, because we've just had a big round of Fukushima and nuclear discussion/debate, and rehashing the same debate in another thread doesn't seem productive. But imo this article is quite informative and worth a read.
This is from memory; feel free to correct me if and as I'm wrong.
Such approaches can also be spun positively as "economic development packages/projects". Whenever such is said, the observer should look critically at who is really benefiting -- as often as not, I think, the project owners' interests come ahead of, and sometimes at the cost of, those of local residents.
Ideally, all parties gain. But to do so, amongst other things someone has to keep those in power from cutting too many corners.
Also, molten salt reactors and fusion reactors won't be able to have catastrophic failure modes either.
I think you missed everything in my previous post. All new designs passively cool. You can have safe (comparative to coal and gas) nuclear power.
That's true of some new BWR designs as well:
http://www.ne.doe.gov/np2010/pdfs/esbwrOverview.pdf
Claims 72 hours of passive heat dissipation -- the heat sinks are [giant] tanks of water inside the containment building.
The HN article mentions a passive cooling system in Fukushima Daiichi #1: a gravity-driven steam condenser (footnote #5). It failed when electric batteries failed, because it needed DC electricity to open valves. (I think this isn't the case in ESBWR).
The systems with limited functionality in the absence of power were an isolation condenser (in unit 1) and a reactor core isolation cooling (RCIC) system (in units 2 and 3). An isolation condenser takes steam from the reactor core, passes it through a tank of water to cool and condense it, and then feeds it back as water into the reactor pressure vessel. The flow is gravity driven (i.e., no pumps are needed). The system in unit 1 had a thermal capacity of about eight hours.
I, too, am opposed to natural disasters. (?)
1) Massive earthquake 2) Tsunami 3) Fire 4) Total loss of all power to control systems
Result: no one died from radiation exposure (a couple of guys died from heat stroke while fighting the fire).
Just what do you consider a "worst-case scenario"?
Our "coaches," all senior nuke officers, had us work through the details of some what-if scenarios. Funny thing, we didn't seem to have covered those particular scenarios in our initial training.
It was pretty scary; to this day I'm not convinced that conventional-design civilian nuclear reactors belong anywhere near population centers.
What worried me wasn't the technology itself, but the human fallibility. In the Navy nuclear program, we had the occasional [foul]-up even though we were ferocious about doing things right. We used checklists for everything, even though we were required to have memorized practically every procedure, especially emergency procedures. (In an emergency, the first thing you did was to take the "immediate actions" to put the plant in a safe condition. The second thing you did was to get out the appropriate checklist and start working through it with your watch team.) We second-checked each other's work, and both the worker and the second-checker had to sign off on the work. Noncompliance with the prescribed safety procedures (and with the prescribed serious attitude) was guaranteed to get you in big trouble. The Navy systematically collected and disseminated lessons learned from throughout the nuclear fleet, and every nuclear ship's nuke operators routinely trained on those lessons. All this derived from the tone at the top, set early on by Admiral Rickover.
Both Three Mile Island and Chernobyl were caused (so far as is publicly known) by cascading human errors; apparently the same was true at Fukushima. I have no experience whatsoever in the civilian nuclear industry, but these accidents have reinforced my doubts about whether a civilian work force, even one heavily populated by ex-Navy types, can achieve the kind of zero-defect culture we strove for in the Navy.
The main things that have been found to contribute to HROs are: A chronic sense of unease even in the face of normal operations - always be thinking of ways to improve safety. A separate engineering standards organisation that is not responsible for operations - i.e. they can order shutdowns without affecting their own job objectives in a way that a plant manager cannot. They do not tolerate the so-called "normalisation of deviance" (which is when out-of-range behaviour becomes accepted as people get used to it.).
You know what worries me? The 75 million people who live downstream of the Three Gorges Dam.
"We don't understand the world as well as we think we do and tend to be fooled by false patterns. We mistake luck for skills (the fooled by randomness effect), overestimate knowledge about rare events (Black Swans), as well as human understanding, something that has been getting worse with the increase in complexity." Nassim Taleb
http://www.cbsnews.com/8301-505125_162-40143642/black-swan-l...