An important caveat: This is a developing situation. We are operating on limited information and we run the very strong risk of getting something wrong here. For those of you living in Japan, this is a very serious incident deserving your close attention. For those living in the Americas, this is not yet a source of serious worry, because even in a worst-case scenario, a lot of distance separates the two countries. Dilution, distance, and time all serve to mitigate the effects of accidental radiation release. The latest information from officials is that radiation levels are declining and that a meltdown is not imminent.
There has been a horrible turn of events in Japan with the violent explosion of the building in which reactor 1 of the Fukushima Daiichi nuclear power plant was housed. The design of these particular plants includes an inner, very solid steel containment dome. We do not yet have any reliable information about the status of that vessel, but the evidence suggests that the event is not yet contained.
These three still images from the video show that the reactor housing disappeared in an instant, speaking to an enormously violent explosion.
By appearances, that’s pulverized concrete dust, indicating that a violent explosion occurred. We can be certain that the outer containment structure is completely missing.
This is a horrible event.
Right now I am deeply concerned by the lack of information and official stories that simply do not add up. Here’s the latest on CNN.com:
(CNN) — An explosion at an earthquake-struck nuclear plant was not caused by damage to the nuclear reactor but by a pumping system that failed as crews tried to bring the reactor’s temperature down, Chief Cabinet Secretary Yukio Edano said Saturday.
Workers at the Fukushima Daiichi plant have begun flooding the reactor containment structure with sea water to bring the reactor’s temperature down to safe levels, he said. The effort is expected to take two days.
Radiation levels have fallen since the explosion and there is no immediate danger, Edano said. But authorities were nevertheless expanding the evacuation to include a radius of 20 kilometers (about 12.5 miles) around the plant. The evacuation previously reached out to 10 kilometers.
“A pumping system that failed?” Sorry, that one does not pass the logic test.
Point number one, the building utterly vaporized with a visible shock wave. That’s no “pumping accident;” that’s a massive, high-energy explosion. Point number two, there are only two viable candidates to create that kind of explosive force in this situation: (1) a hydrogen/oxygen explosion and (2) a sudden water-into-steam ‘flash boiling’ event.
Both point to extremely high temperatures being present. In the first case, the thermal decomposition of water into hydrogen (and oxygen) requires extremely high temperatures, preferably well over 1000 degrees Celsius:
Thermal decomposition, also called thermolysis, is defined as a chemical reaction whereby a chemical substance breaks up into at least two chemical substances when heated. At elevated temperatures water molecules split into their atomic components hydrogenand oxygen.
For example at 2200 °C about three percent of all H2O molecules are dissociated into various combinations of hydrogen and oxygen atoms, mostly H, H2, O, O2, and OH. Other reaction products like H2O2 or HO2 remain minor.
At the very high temperature of 3000 °C more than half of the water molecules are decomposed, but at ambient temperatures only one molecule in 100 trillion dissociates by the effect of heat. However, catalysts can accelerate the dissociation of the water molecules at lower temperatures.
This is my favored explanation because of the very brief flash of light seen at the beginning of the explosions sequence (see images below). Hydrogen only very weakly emits light when it burns/explodes, and this is consistent with what was seen. We cannot yet rule anything out, but hydrogen is the most likely culprit in my mind.
On the second possibility, we also see strong evidence for extremely high temperatures:
A steam explosion is a violent boiling or flashing of water into steam, occurring when water is either superheated, rapidly heated by fine hot debris produced within it, or the interaction of molten metals (e.g., Fuel-Coolant Interaction of molten nuclear-reactor fuel rods with water in a nuclear reactor core following a core-meltdown).
Pressure vessels (e.g., Pressurized-Water (nuclear) Reactors) that operate at above atmospheric pressure can also provide the conditions for a rapid boiling event which can be characterized as a steam explosion. The water changes from a liquid to a gas with extreme speed, increasing dramatically in volume. A steam explosion sprays steam and boiling-hot water and the hot medium that heated it in all directions (if not otherwise confined, e.g. by the walls of a container), creating a danger of scalding and burning.
Neither of these possibilities square up with the official story that the temperatures are being brought down and that engineers will have things under control in a couple of days. Let us hope and pray that they will, but the shredding of the outer containment building speaks of a situation that is anything but under control.
Again, I rather seriously doubt that flooding the inner steel containment vessel with water will be an easy task, due to physical damage of the pipes, pumps, valves, and other assemblies, which will probably have to be repaired before flooding can commence. Our evidence is the fact that the outer containment building was rather violently destroyed.
Here’s a few stills of the shockwave, but I invite you to watch the video, as it is difficult to capture the essence in these stills:
There have been reports from Japan’s nuclear agency that radioactive cesium and iodine were detected outside of the facility, which can only happen if the core has been exposed somehow. Perhaps that’s all under control now, but the evidence for very high temperatures, the explosion of the containment building, a 12-mile evacuation zone, and the presence of cesium and iodine all indicate that perhaps the complete situation is not being shared with the public.
If you live in Japan, you should be heading well upwind of this facility and have potassium iodide pills on hand. I would personally be reading the wind forecasts and assuring that I was upwind.
If you live on the west coast of the US, you should know exactly where your potassium iodide pills are and have a multi-week supply of them on hand, but this is always true.
There’s no word yet on the other three reactors, but let us hope they can be fully and safely shut down and contained.
What we do around here is to prepare ourselves prudently and responsibly for an uncertain future. Nobody could have foreseen the timing and severity of the Japan earthquake, because that’s the nature of complex systems, but we can choose to either become minimally prepared or not.
Most choose ‘not.’
March 11, 2011
All technology can do in the face of such force is to minimize damage to communities and infrastructure, he said, and “on both of those fronts, we’re never going to be perfect.”
Given the limits of steel and concrete to resist the forces of nature, much depends on people’s own preparedness to face up to disaster — but that mental infrastructure is in even poorer shape than the nation’s roads and bridges. People in the Midwest might have storm cellars to shield them from tornadoes, and those in coastal cities like New Orleans might keep a hatchet in the attic in case they have to chop their way onto their roof after a hurricane. But in most of the country, simple plans that include having a quick-grab case of supplies, medications and important family papers, as well as a plan for reuniting family members who have been separated in a disaster, are distressingly rare, Dr. Redlener said.
Dr. Redlener, the author of “Americans at Risk,” about why the United States is not prepared for megadisasters and what we be done about it, said the biggest problem is a failure to go so far as even Japan has to protect its citizens from natural disasters.
“We seem to not have the ability or the willingness to do that right now,” he said. “At a time when states are facing $175 billion in deficits and the federal government is trying to deal with very compelling issues of long-term debt and deficits, the likelihood of our being able to mobilize the resources to significantly improve disaster readiness is limited.”
And yet there are few issues as important. In a telephone press conference on Friday, W. Craig Fugate, the administrator of the Federal Emergency Management Service, said, “The lesson that you learn from this is that earthquakes don’t come with a warning. And that’s why being prepared is so critical.”
The bottom line here is that it’s always good to be prepared in advance, but that it’s just not something that people tend to do, no matter which culture they come from. Our prior interview with Dan Ariely went a long way towards explaining why that is.
You can be certain at this stage that there are tens of thousands of families in Japan who are wondering right now why they did not lay in a few minimal supplies like some food, batteries, and stored water that could really ease their current circumstances.
This will also be true for American families when the next big earthquake strikes the US. As we explore in the Crash Course seminar, people change their ways via either insight or pain. Insight would be looking at Japan’s current woes and using that information to spur your own preparations. Pain involves waking up in the midst of a crisis wondering why you didn’t do anything to prepare.
Update: This just in from the NYTimes:
TOKYO — An explosion at a nuclear power plant in northern Japan on Saturday blew the roof off one building and destroyed the exterior walls of a crippled reactor, but officials said radiation leaks from the plant were receding and that a major meltdown was not imminent.
Government officials and executives of Tokyo Electric Power, which runs the plant, gave confusing accounts of the causes of the explosion and the damage it caused. Late Saturday night, officials said that the explosion occurred in a structure housing turbines near the No. 1 reactor at the plant rather than inside the reactor itself.
The blast, apparently caused by a sharp build-up of pressure after the reactor’s cooling system failed, destroyed the concrete structure surrounding the reactor but did not collapse the critical steel container inside, they said. They said that raised the chances they could prevent the release of large amounts of radioactive material and could avoid a core meltdown at the plant.
“We’ve confirmed that the reactor container was not damaged. The explosion didn’t occur inside the reactor container. As such there was no large amount of radiation leakage outside,” Japan’s Chief Cabinet Secretary Yukio Edano said in a news conference Saturday evening. “At this point, there has been no major change to the level of radiation leakage outside, so we’d like everyone to respond calmly.”
Despite the apparent official confusion, I’m still going to go with the explanation of a hydrogen explosion, which still speaks of very high temperatures and the likelihood that the temperatures in the steel core are not as well-controlled as is being revealed. This is, of course, raw speculation on my part and should be treated as such.
I found this article helpful:
Ron Chesser, director for the Center of Environmental Radiation Studies at Texas Tech University, was the first American scientist allowed inside the exclusion zone in 1992 following the Chernobyl disaster. He can discuss issues that Fukushima workers may be facing in light of the cooling system troubles.
Chesser said that though reports have stated the reactors were shut down safely, the reactors still must be cooled constantly to avoid a meltdown of the core.
All four reactors have been shut down at Fukushima Daini.
“The fact they’re having trouble cooling the reactors is going to trigger an emergency,” Chesser said. “There are certain trigger points for declaring an emergency at nuclear reactors. Reduction in cooling capacity would be one of those. Release of radiation would be another. Reactors are not like your car that you can turn off and walk away. They’re going to continue generating a great amount of heat until the core is disassembled. Without cooling water, then you stand a real chance of a meltdown of core that could result in a large release of radiation, potentially.”
However, Chesser, who has toured a smaller Japanese nuclear power plant in Chiba, said Japanese designers put many precautionary measures and contingency plans in place to ensure reactor safety in the event of an earthquake.
“I was very much impressed with the amount of attention to safety, especially regarding potential of earthquakes,” he said. “I was a little bit surprised when I saw they had a looming crisis at the Fukushima power plant just because of all the great attention the Japanese pay to earthquake safety.”
Also, the Fukushima reactors appear to have containment vessels over them unlike Chernobyl, he said. Though there is cause for concern, Chesser said he thought workers at the plant must have some cooling capacity available, since the evacuation radius from the plant was only 1.9 miles and affected 3,000 people.
“I think that sounds like that’s a low-level alert,” he said. “It didn’t sound like there were that many people being evacuated. At Chernobyl, when it went, they eventually were evacuating people 18 miles away from the reactor. It doesn’t sound like there’s an imminent issue, but it is serious. Any time you have a nuclear facility that size that is not meeting requirements for cooling, you have a real emergency on your hands.” According to the Tokyo Electric Power Company’s (TEPCO) website, the Fukus
The reactor in question is quite well designed but the latest plan to pump in seawater and boric acid says that all of the planned ‘fail safes’ have failed.
This is a last ditch effort. Should this fail, the next step would be entombment. Through all of this, the most likely scenario is that very little radioactivity will be released but that’s a small comfort to those potentially living in its shadow.
Even a very low chance of a full breach of the containment system is too much of a risk.
I guess the good news here is that there’s something they can do.
The diagram below gives us a better sense of what’s in those funny cubic buildings:
The blue arrow points to the concrete containment vessel and the red points to the reactor vessel itself.
The explosion at Fukushima has apparently disintegrated the upper third of the reactor building. The video and pictures currently available indicate that the “blow out panels” of the reactor building and roof cover were blown away by an energetic explosion likely due to a hydrogen gas detonation. The reactor core refuelling deck and the surface of the elevated irradiated nuclear fuel pool are now exposed to the atmosphere. Essentially, the photos show the remaining steel I-beam structure for the weather cover that was over the refueling deck and the top of the “spent fuel” pool. These panels are designed to “blow out” at overpressure.
The actual “pressure suppression system” structures credited for containment sit below this structure inside the concrete reactor building, namely the drywell and wetwell or “torus.” The drywell is the large inverted lightbulb steel structure which is 100 feet tall and a nominal wall thickness of 1.5 inches. The reactor vessel sits inside this structure. In the event of a coremelt accident involving high pressure and high temperature, the highly radioactive steam and pressure would be vented into the drywell and then routed through the large diameter pipes to the “wet well” or “torus” which is the large 18 foot diameter hollow doughnut-shaped structure that surrounds the drywell. The torus contains approximately 1 million gallons of water and designed to receive the pressurized radioactive steam where it is supposed to be quenched and contained.
The status of the reactor containment in the reactor building remains unclear, but apparently remains intact. Fuel damage has apparently occurred because elevated levels of radioactive iodine and cesium are being monitored outside of reactor containment.
What is additionally unclear is how much cooling water is left in the fuel storage pools and whether or not there has been damage to irradiated fuel stored in that pool. There are reports of sea water being brought in to cool this facility.
We’ll be posting more as we learn more.
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