Pick a number, and that reactor is described as being near a meltdown. The news coverage coming out of Japan is even more confused when American media deciphers it. Hopefully hard facts come in soon…
Meltdown occurred according to Nuclear and Industrial Safety Agency
URGENT: March 12 00:00 PST: Explosion at Nuclear Facility
VIDEO of explosion at nuke plant.
Reuters Live Earthquake News Feed
Several people appear to be injured at Fukushima nuclear plant – NHK
Walls and roof of a building at site destroyed by blast – NHK via Sky News
UPDATE: 22:50 PST: BREAKING NEWS: Pressure successfully released from Fukushima No. 1 reactor: agency
UPDATE: 21:47 PST: Meltdown underway at Reactor #1? http://twitter.com/#!/dicklp
Fukushima fuel cores are melting at 2000C and dropping onto steel floor. Steel melts at 1500C. Could still be brought under control, but Four other Fukushima nuke reactors are struggling with similar problem. If multiple meltdown begins, it will be uncontrollable.
Nuclear reactor coolant systems are running on batteries, and the coolant has reached the boiling point. Extremely critical situation currently at several earthquake affected nuclear reactors. Officials are concerned that a Three Mile Island 1979 meltdown could happen here. Reuters Link
From the LA Times:
Conditions appear to be worsening at a nuclear power plant in Fukushima Prefecture in northeastern Japan, according to local media.
The Kyodo news agency reported that the cooling system has failed at three reactors of Fukushima No. 2 nuclear power plant. The coolant water’s temperature had reached boiling temperature, the agency reported, citing the power plant’s operator, Tokyo Electric Power.
The cooling system failure at the No. 2 power plant came after officials were already troubled by the failure of the emergency cooling system at the Fukushima No. 1 plant, which officials feared could cause a meltdown.
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Irrespective of whether the cooling system is functioning as designed or not, the shutdown plants still have to get rid of a certain amount of heat. I wonder if plants generally have large enough radiators for this, or is venting of steam the normal way of dealing with this.
@Jimmy Haigh
This is why I’m not a big fan of magnitude 9 earthquakes.
One thing I haven’t seen discussed here are these promising new electricity generators, based on co2 no less.
Once these become available, especially for coal-fired plants, a large decrease in co2 emissions would become possible.
Meltdown underway: http://twitter.com/#!/dicklp
Once the crisis is over, I assume the utilities will back up their backup diesel generators with something more reliable…like wind turbines.
Yes, I’m kidding.
From: http://www.nisa.meti.go.jp/english/files/en20110312-3.pdf
Ryan Maue says:
March 11, 2011 at 9:47 pm
Meltdown underway:
exaggeration.
In this situation you should just seal the reactor.
However, the cost is very expensive. (moral, stock exchange and many others factors)
Unless the structure of containment is compromised by the earthquake.
Apparently I put my neck at a premium.
Re: ggm says:
March 11, 2011 at 7:31 pm
“melt downs” and “dirty bomb exposions” are a myth with these sort of reactors.”
If it were a myth, billions of dollars would have been wasted on the design and construction of redundant safety systems for both PWR and BWR reactor systems. “Melt down” refers to a condition in which the cladding of the fuel rods is melted by excessive heat and the fuel is no longer contained in the physical configuration that assured control of its nuclear reaction. In theory, at least, that could result in a runaway situation that could result in a breach of the containment vessel (a thermal explosion) which would, in turn, contaminate a wide geographical area.
In the U.S., Three Mile Island did suffer a partial meltdown of its fuel rods. We probably came closer to the ultimate calamity, however, at Browns Ferry Nuclear Plant (BWR reactors, incidentally) in the 1970’s when a fire shut the plant down and rendered both redundant emergency cooling systems inoperable. Had the plant lost off-site power over the next several days, the result could well have been catastrophic.
I am certainly not anti-nuclear and there are several new designs out there that purport to be impervious to a “loss of coolant” accident. However, the generation of both BWR and PWR designs currently in commercial power plant service in the U.S. and Japan are NOT impervious to a loss of cooling accident.
Here are some very initial thoughts from an old nuclear guy, without much information other than my memories of yore.
First, calm down. This is a technical problem to be resolved, just that.
All the nuclear units at the both the Fukushima Daiichi site and Daini sites are Boiling Water Reactors (BWRs).
During power operation the fuel in the cores of BWRs are designed to perform in a controlled boiling environment during full power operation. The nuclear plant of concern is fully shutdown with all control rods inserted. The shutdown plant’s decay heat rate across the fuel cladding is very tiny compared to power operation heat rate across the fuel cladding.
Boiling in the BWR fuel core is not itself a concern wrt to fuel cladding failure or melting, it was designed for that environment. What is of concern is that there needs to be water in the RPV (reactor pressure vessel) that contains the fuel core. The water level needs to be (if my oldish memory serves me correctly but don’t quote me on this after so many years) more than ~2/3 of the fuel core height in some BWRs. As the water in the concerned RPV boils off more water will, over time, need to be added to the RPV to keep the core sufficiently covered within design limits. So they need electric power restored to add the water; whether by batteries, DGs or from the grid (solar and wind power if it is daytime or the wind is blowing). That is a context for what is meant when talking about time factors.
Another time factor revolves around a different concern. That is the concern that steam produced by the boiling in the core (without cooling), will find its way into the secondary containment. Steam, in the existing emergency shutdown condition will normally find its way out of the RPV into the primary containment (a steel shell and large water pool with some areas having concrete structural support) because that is what it was designed for. But the concern is that without electricity to provide cooling systems to the primary containment, after a period of time, the design pressure of the primary containment might be theoretically be reached. If this happens then leakage to the secondary containment (basically the reactor building) will occur, that is the last barrier to the potential for radioactive gases being released into the environment.
I can only assume (because it is what I would do) the strategy by the Japanese utility and government would be to prevent primary containment damage (leaks), so that you still have an unchallenged secondary containment as some sort of a backup. Prevention of primary containment damage (leaks) could theoretically be achieved by periodically venting the primary containment through some HEPA filters into the environment to prevent damage to the primary containment. It is a possibility (high or low) to do that without electrical power depending on many different circumstances which are unknown to us (the public). I would consider this a good strategy (while trying to restore electric power for water addition to the RPV and cooling systems for the primary containment) because controlled release is better than the potential for uncontrolled release if the primary containment is eventually damaged by not venting it.
Some really good minds with thousands of total experience years are addressing the problems at the Fukushima nuclear plants.
John
First, in both cases, the core cooling (more strictly, decay heat removal system) appears to be working as planned. In a BWR, decay heat removal works by allowing a controlled boil of coolant water, and venting that via a supression pool into the containment. Normally, there’s a secondary heat exchanger system that removes that heat to atmosphere. It’s not clear whether that’s happening.
So far as I can see, all the direct reports of high pressures and temperatures pertain to the containments, not the main reactor vessels. If anything, primary circuit pressures are likely to be low, given the rate of heat generation and removal.
At Fukushima Daiichi, the issue is the loss of back up generation. I’d expect that to be readily resolved, and once that’s running, the HVAC systems will be able to bring containment temperatures back to normal faily quickly.
At the second plant, the problem’s a bit different. The back-up generation has run as planned, but the make-up system for the suppression pool seems to have failed some hours after the shutdown.
That’s caused elevated temperatures in the containment. Again, nothing not readily manageable by controlled (and filtered) venting.
In either case, I’m not aware of any concrete reason to assume that fuel has been exposed, or undergone any substantive damage. Even traces of caesium do no more than suggest that there may be a damaged element or two.
It is dangerous that the CANDU reactor design is not used more for nuclear power. It was specifically designed to avoid the risk of meltdown by making the coolant as the moderator. The coolant is heavy water, adding more heavy water to the CANDU reactor increases the reaction leading to heat (superheated steam) that is then run through the standard heat exchanger and off to drive the turbine generators. If there was a disaster where the station was knocked out of commission and all the safety systems shut off the worst possible case is the coolant (moderator) overheats and boils off – leading to the nuclear reactor shutting down. Note the reactor has not come anywhere close to the melting point of anything, and the reaction is not self sustaining.
Also CANDU reactors have been strongly considered for the safe destruction of the Russian and US stockpile of weapons grade plutonium.
@Andy Dawson
I’d have expected it to be readily resolved, too. But, nearly a day into this, I haven’t seen any report of power to emergency systems being restored. The latest report I’ve seen is from 10:00 am local time today on the tepco site. That’s 5 hours ago!
@L. Sheehan: Re Chernobyl. ” flawed Soviet reactor design coupled with serious mistakes, complete meltdown ”
I was about to object to the term “meltdown”, but then remembered more of the story. The initial accident was a steam explosion, followed by a burning graphite around the core. Only later did they discover that the core melted (maybe helped by the graphite fire) and dripped into the under stories of the building creating stalagmites of resolidified core metal.
Chernobyl was a steam explosion caused by a badly flawed, unstable design. It was a graphite moderated, water cooled core. The stupid part of its design was that the water quenched the neutron flux. Water & graphite was stable. Steam and Graphite was a known run-away situation to be avoided. It would create a hot spot, creating more steam, faster reaction, making a bigger hot spot, more steam, quickly to a Steam Explosion.
The coup-de-gras in the poor design was putting 12″ of graphite on the ENDS of the control rods. That’s kind of like filling a fire hose up with gasoline before hooking it up to the hydrant. The first squirt from the hose adds fuel to the fire.
Andy Dawson says:
March 11, 2011 at 10:29 pm
– – – – – –
Andy,
We cross posted similar thoughts.
I am glad to see others (you included) who are not exclaiming catastrophy. You would think this is a revivalist CAGWist meeting or something.
Thanks for your post.
John
Looks like they got the valves open:
“Japan’s nuclear authorities said on Saturday that radioactive pressure was successfully relieved at the No.1 reactor at Tokyo Electric Power’s Fukushima Daiichi plant by opening valves. “
Latest from the IAEA at 0730 Central Europe Time:
http://www.iaea.org/press/
“Japanese authorities have informed the IAEA’s Incident and Emergency Centre (IEC) that, starting at 9:00AM local time, they have started the preparation for the venting of the containment of the Unit 1 reactor at the Fukushima Daiichi plant through a controlled release of vapour. The operation is intended to lower pressure inside the reactor containment.”
The containment pressure is high so they want to depressurize it to keep within the design pressures. There is apparently no uncovering of the core.
If you wander over to the leftist precincts on the web (you know where), it is quite ghoulish to see their zeal in cheering for a catastrophe. Absolutely disgusting.
MikeG: “If water isn’t put in the core, the core will melt and eventually melt its way through the vessel and into the bottom level of containment. ”
No, Mike, it won’t. That’s one of the interesting results of TMI2. Examination of its pressure vessel was done in the early 1990s and the flow of corium down the vessel. What was determined by the examination was that as the fuel melted its surface area expanded. In short, it cooled down too rapidly to melt through the pressure vessel even if all of the fuel melted, which was not the case at TMI.
John Whitman is right. Everyone needs to calm down a lot. Just watching the TV tonight someone supposed to be a nuclear expert was making references to Chernobyl. That’s so off the wall it’s not even worth discussing.
John,
indeed. I was about to say, your word
“First, calm down. This is a technical problem to be resolved, just that.”
are a succinct expression of the thought processes of engineers the across the world.
All in all, the only thing that’s surprised me in this is the failure of the supression pool make up system. The best source of technical data at the moment seems to be World Nuclear News.
http://en.wikipedia.org/wiki/BWR
http://en.wikipedia.org/wiki/Scram
Not to worry. Far more pain and suffering from the quake and tsunami. I used to work with real radiation. We once had a guy walk by a radiation detector we called a hand an shoe counter, and he set it off, just by walking by. (Really; short version: he had been to the doc for a radio-CAT scan, and he was full of medical isotopes. Those detectors we had to step on and put our hands in to be cleared were so sensitive, he could not walk past without setting them off. I’m not exaggerating. That is how low the “normal” levels are. So, 100 or 1000 times higher is no big concern.) I used to do tests that required me to work off hours so no one else was on the floor above my basement lab. Others worked with materials even hotter than that.
Too many people go bananas over radiation. We live in it. We cannot be without it. It is just not possible.
BWRs are relatively intrinsically safe. TMI was a tragedy ONLY because tragedy sells. TMI was never a significant threat, no matter what the MSN says.
I’ve never looked hard at thorium reactors, but I trust they are good designs, and thorium is even more abundant than uranium. Regardless, many passive and intrinsically safe features go in to newer designs. EBR-II (http://en.wikipedia.org/wiki/Experimental_Breeder_Reactor_II ) was about as safe as could be imagined. It would safely shut down under any expectable circumstance, even if all the backups failed.
Nuclear power will eventually rule. We may be out of coal and natural gas before anything besides nuclear fission becomes overall viable. Fusion is inevitable, but it could still be two centuries away. Sooner or later, we will simply design nuclear plants well enough to satisfy the most paranoid, and we will need them enough to overcome any resistance.
Can someone comment on the credentials of the Union of Concerned Scientists commentary at this stage.
They seem to be drawing conclusions despite being 10,000km away?
[ryanm: lemme intercept that softball question: they have zero, zilch, nada credibility]
NHK World broadcast mentions a leak of several elements indicating a possible partial meltdown. http://www3.nhk.or.jp/daily/english/12_45.html
“The government’s Nuclear and Industrial Safety Agency says 2 radioactive substances, cesium and radioactive iodine, have been detected near the Number One reactor at the Fukushima Number One nuclear power station.
The agency says this indicates that some of the metal containers of uranium fuel may have started melting.
The substances are produced by fuel fission.
University of Tokyo Professor Naoto Sekimura says only a small part of the fuel may have melted and leaked outside.”
From: http://online.wsj.com/article/SB10001424052748703555404576195700301455480.html
Notice the qualifiers. In addition, others have reported that they are using a fire engine to add water. So far, it sounds like the system is working. Let’s hope it all turns out well. In any event, it looks like they are going to be short of generating capacity for a time after everything is brought under control. After such a strong earthquake, everything would need to be checked and rechecked. The lack of generating capacity for some time may well be the real catastrophe in this case.
…as a guy who’s been in and around these things a few times, my thoughts and prayers are with the reactor emergency response teams, engineers, management and other emergency personnel. They are wrestling with the devil with this one, I sure hope we don’t have another quake that makes their situation even worse.
Thanks to Andy D, John W and other industry guys for your contributions to this thread!
http://www.tepco.co.jp/en/press/corp-com/release/11031220-e.html
Current status of Fukushima Daini
http://www.tepco.co.jp/en/press/corp-com/release/11031219-e.html
Fukushima Daiichi