What is Happening at the Japanese Nuclear Plants
This is the most helpful article I have found yet on the problems at earthquake-damaged nuclear plants. As one can imagine, it is a lot more sensible than some of the garbage in the general media.
It cleared up one point of confusion I had - I was not sure why there was still heat generation after the control rods slammed down, killing the fission process. But apparently there are a number of intermediate fission products created that continue to decay for several days, producing about 3% of the heat of the full fission process. This heat is what boiled away the water in the reactor vessel once flow of cooling water stopped. It is this boiling that led to the necessity to release steam (to reduce pressure in the reactor vessel). It was this steam that was partially disassociated into hydrogen and oxygen, which led to the explosion.
One fact that has been lost in all the hype, and may continue to be lost, is that the earthquake alone (which was 7 times larger than the plant was designed for) was necessary but not sufficient to lead to the current problems. Everything probably would have been fine had it not been for the tsunami knocking off all the diesel generators the plant used in an emergency to keep the colling pumps running. Apparently the generators they rushed to the site later could not be used due to various incompatibilities, the type of real-world frustrating problem that will be immediately recognizable to any engineer who has a troubleshooting background.
Update: Unfortunately, the author may have been overly optimistic. The author implied the pile would stop producing new heat after a few days, but that does not seem to be the case, particularly since spent fuel rods apparently have to be kept in water to keep them cool months or years after they were in service. With the apparent rupture of the main presure vessel around the core, all bets would seem to be off in terms of containing the most harmful radioactive elements.
I did troubleshooting at a refinery for years, and almost every time the worst disasters were from improbable event and/or screwup after improbable event. The human mind seems to be unable to really grasp just how screwed up things can get. The novel Jurassic Park was as much about this problem as it was about dinosaurs.
Update #2: This is the piece that was missing from the earlier linked report:
The sharp deterioration came after a frantic day and night of rescue efforts focused largely on the No. 2 reactor. There, a malfunctioning valve prevented workers from manually venting the containment vessel to release pressure and allow fresh seawater to be injected into it. That meant that the extraordinary remedy emergency workers had jury-rigged to keep the nuclear fuel from overheating no longer worked.
As a result, the nuclear fuel in that reactor was exposed for many hours, increasing the risk of a breach of the container vessel and more dangerous emissions of radioactive particles.
By Tuesday morning, Tokyo Electric Power said that it had fixed the valve and resumed seawater injections, but that it had detected possible leaks in the containment vessel that prevented water from fully covering the fuel rods.
Update #3: Things are slightly better.
mike goad:
Google the term "zirc water reaction" for an explanation of the chemical reaction that resulted in hydrogen generation.
March 14, 2011, 9:50 amanon:
The link's description about where the hydrogen came from and Chernobyl is a little misleading. Author probably understands, but oversimplified a bit.
mike goad is right. At high temps in the presence of water, the zircaloy or zirconium cladding reacts with water (steam) to produce lots of H2 and 02.
I don't think that was what caused the Chernobyl reactor to come apart. I've always thought that it was the formation of steam voids, combined with a positive void coefficient of reactivity (i.e., a steam void causes local power goes up) caused the Chernobyl reactor to become prompt critical (i.e, maintaining chain reaction on prompt neutrons only). Local power thus spiked by many orders of magnitude, and water in vicinity became steam instantly causing a steam "explosion."
March 14, 2011, 10:11 amanon:
Yes, Coyote, that would be a very short-lived positive feedback loop in the Chernobyl reactor.
March 14, 2011, 10:14 amDaublin:
"I have read a 3 page report on CNN where every single paragraph contained an error."
Yikes. I haven't looked myself. Does that sound accurate?
March 14, 2011, 10:55 amDan:
It's sickening how quickly Congress and the media are doing a 180 on nuclear power based on this incident. As your post points out, the earthquake was not to blame for the problems Japan is having; poor planning and organization seem to be more responsible. But that won't stop the anti-nuclear power groups and the politicians from using this as an excuse to further stall the development of much-needed nuclear power here in the U.S.; just as last year's BP accident led to the overly-broad restrictions on under-sea oil drilling in general when BP alone should have suffered consequences for its irresponsible actions.
Producing energy is not a clean, safety-guaranteed process. Accidents happen, and they are devastating (just ask the fishermen on the Gulf Coast). But unless we want to really make huge changes in the way we live and the way our economy operates, we have to continue to aggressively push for more and better energy, and both nuclear power and undersea drilling have important places.
I continue to hope nuclear fusion can be the ultimate answer, but it is discouraging how little progress has been made in 60 years of research. I wonder how an earthquake would affect a fusion reactor.
March 14, 2011, 12:35 pmFred Z:
Let's all ask the anti-nukes what they think will happen if there's a Richter 9.0 quake anywhere near a big hydro dam. Inland tsunami is what.
I'm Canadian and I've always wondered why we and you don't get together and build lots of nukes up on our tundra and ship nuclear generated power down to you.
Oh wait, I forgot, when global warming happens, it will be prime farmland and wildlife habitat, just like ANWR.
March 14, 2011, 1:07 pmblokeinfrance:
So 20,000 people die in an earthquake and 2 nuclear workers die in an explosion. So we must concentrate on the nuclear explosion.
Meanwhile 3 out of dozens of reactors which were exposed to an earthquake 7 times more powerful than their design strength are having some serious but not long lasting problems and are fixing themselves as they were designed to, despite being already 40 years old.
And as a consequence some EU politicians are now proposing to shut down 30% of our generating capacity on safety grounds despite the absence of seismic activity in Europe.
Remind me, what's the seismic rating of those bird choppers again?
March 14, 2011, 5:15 pmDaveK:
From what little I've read about this, the response plan for the Japanese Nuke Plants was reasonably good and would have prevented the current problems. The backup power generators worked just fine... up until the fuel supply, contaminated with seawater and muck from the tsunami, caused the engines powering the generators to fail. Like all good plans, they work until you get bitten by reality and the little detail you thought would never happen.
March 14, 2011, 5:54 pmjoe:
What I find most sad about all this is that the ultimate cause of failure is the reliance on active cooling, a problem which has been eliminated in the newer designs (SBWR/ESBWR Gen 3 and 3.5).
If the anti-nukes hadn't thrown up so many barriers to building new nukes, we'd probably have much safer nukes by now.
We know how to make them safe. But this one was so old it was actually scheduled for decommissioning this year.
March 14, 2011, 5:54 pmJohn Moore:
As far as I can tell, the boiling water reactors do not use an active cooling system - they need no pumps to circulate coolant - the steam does it. They only need power to operate the valves, etc. Thus I don't understand why these reactors overheated to this degree - one wonders if there isn't other damage involved. Another odd thing is they are pouring in the neutron poison in (Boron) when the control rods by themselves almost totally quench the fission (feedback goes way down). They may be dumping in the Boron to deal with the case of an actual meltdown, where the fuel would no longer be riddled with control rods.
Most recently, something more serious has happened at Reactor #4, which was not even in service (and reportedly not even fueled). It had an explosion a few hours ago, and is still on fire. Radiation levels around the plant are way up - reporting 80 mSvt (8 REM/hr) which significant.
I am also listening to NHK (in English) at http://www3.nhk.or.jp/nhkworld/index.html . They are advising people within 20km to evacuate, and more ominously, telling those out to 30km to stay inside, sealing off their quarters (no open windows, no use of heaters). They are saying that those outside should clean off their close before going (and staying) inside. All of this sounds like they fear radioactive particulates, which is qualitatively different from the gases released in the earlier, minor events at #1 and #3.
The Japanese also have a poor record with revealing the facts about nuclear accidents. In the past they have underplayed the seriousness of accidents and concealed information.
Not only that... a low pressure system is moving up the coast, and the winds have shifted so that Tokyo is directly downwind of the plant.
Time to stay tuned.
March 14, 2011, 8:41 pmIgotBupkis, President, United Anarchist Society:
> Like all good plans, they work until you get bitten by reality and the little detail you thought would never happen.
Indeed --
1) These events will lead to a flurry of activity designed to make even these reasonably improbable events not have any affect on nukes
2) Example in point above, unrelated to nukes, but file this as exemplary of "the universe will bite you in the ass when, where, and how it chooses, and there's not one single damned thing you can do to outsmart it":
I was told many, many years ago the story of a Navy department that religiously backed up its hard drive onto floppies (this would be in the ancient days of 20-50mb HDs). They did so daily, then took the floppies into a large, walk-in, fireproof safe for protection. They had a rotational scheme that gave them backups for years backwards sitting in that vault. Along comes the fateful day, and the HD crashes. So they replace the HD, bring out the most recent backup... The dreaded "I/O Error" on the first floppy in the set. No probs, go back to the previous one... "I/O Error". Back again. "I/O Error"... and so on. All the backups were useless, nothing retrievable.
Now, this being the Navy, a head must roll. Clearly, someone screwed up the process. In the subsequent investigation, it became clear that the process was being done properly, the floppies were capable of doing the job in question... no one had any idea about what had happened.
Until...
Someone realized that the main power conduit for the entire building ran right past the walk-in safe.
Now: What is a big hunk of steel with a current-bearing wire wrapped around it?
Right. An electromagnet....
The vault was basically a gigantic bulk eraser.
They supposedly did a study... the vault would apparently erase any media placed inside it to unreadability within 24 hours.
Now, you can certainly criticize the people in question for not verifying the functionality of their backups, but still... a giant bulk eraser? Really?
I repeat: "the universe will bite you in the ass when, where, and how it chooses, and there's not one single damned thing you can do to outsmart it."
March 15, 2011, 1:23 amrxc:
It appears that the Fukishima plants suffered a "Station Blackout" (SBO) event, which is actually considered to be part of their design basis, and for which they are supposed to have procedures and equipment available to deal with. The equipment may not have to be pre-installed, but it should be located somewhere under the control of the plant operator, and available to be brought in as needed. The information that has come out so far is not very comprehensive, but the bravenewclimate web site does a pretty good job of explaining the systems to the layman.
I am suprised (1) that the diesel generators were overwhelmed by the tsunami, and (2) after nearly 4 days, the Japanese are still unable to provide the needed equipment at the plant to restore the cooling. The buildings that hold the important piping and other system components seem to be intact, and therefore they should be able to hook up temporary pumps and electric power supplies to make those portions inside the buildings operate. There appears to be considerable damage on the seaward side of the complex, outside the buildings at the intake structure (where seawater cooling comes into the plant) but even the turbine building seems to still be intact.
This is quite surprising, but the progression of events is consistent with an unmitigated SBO. The spent fuel pools on top of the buildings may have been damaged by the explosions, and they will need to have someone go up there with a fire hose to keep them full.
BWRs are generally pretty robust, in terms of being able to deal with this sort of situation. The limiting factor is suppression pool temperature and containment pressure. Even there, if necesary, you can vent the containment, and the releases of radiactive material should not be large because they are filtered thru the water in the suppression pool. Unfortunately, opening the vents is really considered a political act, determined by a government official, because they have to decide when it is time to release radioactive material onto their constituents. It will be really interesting to see the final timeline of decisions for this event.
About 20 years ago, I made my first visit to some Japanese nuclear facilities, and I think one of them was one of the Fukushima sites (don't remember which). I also visited one site on the Sea of Japan, where we took the tour thru the plan on the approved tour route. Everything was spotless, the control room was immaculate, the people were articulate, and everyone was impressed. Until, that is, we were side-tracked off the official tour route by some maintenance activities, and we saw the part of the plant that was NOT on the tour route. It included steam leaks, rust, damaged insulation, etc. Just like you would see at other similar industrial facilities. It made me think that all of the vaunted Japanese expertise and comittment to detail was just a thin veneer to save face. I told my boss at the time that I thought that the Japanese would have the next "interesting" accident, and indeed they did. ABout 10 years later they had a criticality accident at a fuel fabrication plant, and now 20 years later, they have this event. Hopefully they will learn from this event that they cannot apply a thin glossy veneer to their management of nuclear energy.
March 15, 2011, 2:04 amTed Rado:
Everyone should cool it until a thorough study of what went wrong has been done. It may be that there is an easy fix to the problem, such as gravity cooling water backup, another secondary diesel generator, or whatever. Charging off in a panic and screwing everything up before we have analyzed the situation is a huge mistake.
March 15, 2011, 6:59 amHLF:
John the steam goes to the turbine then is condensed in the condenser. This is located below the turbine in the turbine building. Then it is pumped back into the reactor. The steam cannot push it back into the reactor against the pressurethat is in the reactor. The boron is injected because of the changing fuel geometry,from long and thin to a blob. From what i have heard their equipment for releasing gas in this type of event is only rated for 7 psi and the containment is rated for 65 psi. They did not release until approximately 120 psi. This blew their 7 psi ductwork up and released hydrogen into the reactor bldg. That’s why the explosion. US reactors will release at a much lower pressure and in the US that system is designed for a much higher pressure. We use piping not ductwork. Why they did not release. I don't know. Equipment failure (It can be manually operated) or they could not release without government approval.
March 15, 2011, 6:52 pmlease agreement:
There are rumors about the effect on the exposure of radioactive materials to people in Japan. Future damages to nuclear power plants should also be avoided through concerted efforts by the government and the civilians.
March 16, 2011, 12:39 pm