Hot News Nuclear

Fukushima Nuclear Accident – 15 March summary of situation

The situation surrounding the Fukushima Nuclear Accident, triggered by Japan’s largest recorded earthquake and the resulting 10 m high tsunami, continues to develop rapidly. This post is intended to be a concise update of the situation as of 12pm Japan Standard Time, 15 March 2011. For a summary of the situation prior to today, read these posts:

Japanese nuclear reactors and the 11 March 2011 earthquake

Fukushima Nuclear Accident – a simple and accurate explanation (with further updates at MIT here:

Japan Nuclear Situation – 14 March updates

Further technical information on Fukushima reactors

TEPCO reactor by reactor status report at Fukushima

This is also a useful summary, from William Tucker (published in the Wall Street Journal): Japan Does Not Face Another Chernobyl. See also:  Nuclear Overreactions: Modern life requires learning from disasters, not fleeing all risk.


Attention has centred on units #1, 2 and 3 of the Fukushima Daiichi plant (all Boiling Water Reactors built in the 1970s). Current concern is focused on unit #2 (more below). Units 4, 5 and 6 at the site were not in service at the time of the earthquake and their situation is stable.

At a nearby plant, Fukushima Daiini, the situation is now under control, and units are in, or approaching, cold shutdown. I do not expect any further significant developments at that site. To quote WNN:

In the last 48 hours, Tepco (Tokyo Electric Power Company) has carried out repairs to the emergency core coolant systems of units 1, 2 and 4 and one by one these have come back into action. Unit 1 announced cold shutdown at 1.24 am today and unit 2 followed at 3.52 am. Repairs at unit 4 are now complete and Tepco said that gradual temperature reduction started at 3.42pm. An evacuation zone extends to ten kilometres around the plant, but this is expected to be rescinded when all four units are verified as stable in cold shutdown conditions.

Fukushima Daini Unit 1 reactor

o As of 1:24AM on March 14, TEPCO commenced the cooling process after the pumping system was restored.

o At 10:15AM on March 14, TEPCO confirmed that the average water temperature held constant below 212 degrees Fahrenheit.

Fukushima Daini Unit 2 reactor

o At 7:13AM on March 14, TEPCO commenced the cooling process.

o As of 3:52PM on March 14, the cooling function was restored and the core temperature was stabilized below 212 degrees Fahrenheit.

• Fukushima Daini Unit 3 reactor

o As of 12:15PM on March 13, reactor has been cooled down and stabilized.

• Fukushima Daini Unit 4 reactor

o At 3:42PM on March 14, cooling of the reactor commenced, with TEPCO engineers working to achieve cold shutdown.

The rest of this post will focus on the ongoing crisis situation at Fukushim Daiichi. Let me underscore the fact that accurate information is sparse, uncertain and rapidly changing.

During March 12 and 13, there were serious issues with providing sufficient cooling to units 1 and 3 after the tsunami had caused damage to the diesel backup generators and compromised the emergency cooling water supply. This resulted in a decision to use sea water injection to keep the reactors cool — a process that is ongoing. Steam was regularly vented as part of the effort to relieve steam pressure within the reactor vessels, but this also led to an accumulation of hydrogen gas within the secondary buildings that house the reactor units. Possible sources for the hydrogen are discussed here. Unfortunately, this hydrogen could not be vented sufficiently quickly, resulting in chemical explosions (hydrogen-oxygen interactions) within the two reactor housing buildings of both unit 1 and unit 2 during March 12-13.

The roof and part of the side walls of both buildings were severely damaged as a result. After the first hydrogen explosion there is no longer a roof on the building, so there is little chance of any large buildup of hydrogen or further explosions at these units. [In restrospect, the designers (40 years ago) perhaps should have more carefully considered the implications of the decision to vent the pressure suppression torus to the reactor building space]. Although hydrogen recombiners are a standard feature of that design, they unfortunately lost all AC power, and then the batteries were run down. Containment (the robust concrete shell and 18 inch thick steel reactor vessel within it), however, remained intact. This was verified by monitoring levels of radiation surrounding the units — if there had been any containment breach, levels would have jumped.

This cutaway diagram shows the central reactor vessel, thick concrete containment and lower torus structure in a typical boiling water reactor of the same era as Fukushima Daiichi 2

This is an overview of the current status of units 1 to 3:

Radiation Levels

o At 9:37AM (JST) on March 14, a radiation level of 3130 micro sievert was recorded at the Fukushima Daiichi Nuclear Power Station.

o At 10:35AM on March 14, a radiation level of 326 micro sievert was recorded at the Fukushima Daiichi Nuclear Power Station.

o Most recently, at 2:30PM on March 15, a radiation level of 231 micro sievert was recorded at Fukushima Daiichi Nuclear Power Station.

Fukushima Daiichi Unit 1 reactor

o As of 12:00AM on March 15, the injection of seawater continues into the primary containment vessel.

Fukushima Daiichi Unit 2 reactor

o At 12:00PM on March 14, in response to lower water levels, TEPCO began preparations for injecting seawater into the reactor core.

o At 5:16PM on March 14, the water level in the reactor core covered the top of the fuel rods.

o At 6:20PM on March 14, TEPCO began to inject seawater into the reactor core.

o For a short time around 6:22PM on March 14, the water level inside the reactor core fell below the lower measuring range of the gauge. As a result, TEPCO believes that the fuel rods in the reactor core might have been fully exposed.

o At 7:54PM on March 14, engineers confirmed that the gauge recorded the injection of seawater into the reactor core.

o At 8:37PM on March 14, in order to alleviate the buildup of pressure, slightly radioactive vapor, that posed no health threat, was passed through a filtration system and emitted outside via a ventilation stack from Fukushima Daiichi Unit 2 reactor vessel.

Fukushima Daiichi Unit 3 reactor

o At 11:01AM on March 14, an explosion occurred at Fukushima Daiichi Unit 3 reactor damaging the roof of the secondary containment building. Caused by the interaction of hydrogen and oxygen vapor, in a fashion to Unit 1 reactor, the explosion did not damage the primary containment vessel or the reactor core.

o As of 12:38AM (JST) on March 15, the injection of seawater has been suspended.

What is of most current concern?

Units 1 and 3: the situation now seems fairly stable. There is some concern that holding pools for spent nuclear fuel (SNF) may have been damaged by the hydrogen explosions, but nothing is confirmed. Provided the pool walls remain unbreached and the SNF is covered with water, the situation should not escalate. Note: Although still ‘hot’, the SNF decay heat is many orders of magnitude lower than the fuel assemblies within reactors 1 to 3.

Unit 4: A fire has started at the building of Unit #4. Note that the reactor of this unit is stable and was not operating at the time of the earthquake.

Kan also confirmed a fire burning at unit 4, which, according to all official sources, had never been a safety concern since the earthquake. This reactor was closed for periodic inspections when the earthquake and tsunami hit, therefore did not undergo a rapid and sudden shutdown. It was of course violently shaken and subject to the tsunami.

Shikata said that there had been “a sign of leakage” while firefighters were at work, “but we have found out the fuel is not causing the fire.” The fire is now reported extinguished.

Unit 2: This is now of most concern, and the situation continues to change quickly. Here is the key information to hand (I will update as new data emerges).

Loud noises were heard at Fukushima Daiichi 2 at 6.10am this morning. A major component beneath the reactor is confirmed to be damaged. Evacuation to 20 kilometres is being completed, while a fire on site has now been put out.

Confirmation of loud sounds at unit 2 this morning came from the Nuclear and Industrial Safety Agency (NISA). It noted that “the suppression chamber may be damaged.” It is not clear that the sounds were explosions.

The pressure in the pool was seen to decrease from three atmospheres to one atmosphere after the noise, suggesting possible damage. Radiation levels on the edge of the plant compound briefly spiked at 8217 microsieverts per hour but later fell to about a third that.

A close watch is being kept on the radiation levels to ascertain the status of containment. As a precaution Tokyo Electric Power Company has evacuated all non-essential personnel from the unit. The company’s engineers continue to pump seawater into the reactor pressure vessel in an effort to cool it.

Evacuation ordered

Prime minister Naoto Kan has requested that evacuation from 20 kilometer radius is completed and those between 20-30 kilometers should stay indoors. He said his advice related to the overall picture of safety developments at Fukushima Daiichi, rather than those at any individual reactor unit.

Shortly afterwards Noriyuki Shikata said radiation levels near the reactors had reached levels that would affect human health. It is thought that the fire had been the major source of radiation.

Prime minister Naoto Kan has requested that everyone withdraw from a 30 kilometer evacuation zone around the nuclear power plant and that people that stay within remain indoors. He said his advice related to the overall picture of safety developments at Fukushima Daiichi, rather than those at any individual reactor unit.

Regarding radiation levels: It is very important to distinguish between doses from the venting of noble-gas fission products, which rapidly dissipate and cause no long-term contamination or ingestion hazard, and aerosols of other fission products including cesium and iodine.

From NEI:

Yukio Edano, Japan’s Chief Cabinet Secretary, during a live press conference at 10 p.m. EDT, said there is a fire at Fukushima Daiichi 4 that is accompanied by high levels of radiation between Units 3 and 4 at the site. The fire began burning at Unit 4 at around 6 a.m. Japan time on March 14 and is still burning. Fire fighters are responding to the fire. The reactor does not have fuel in the reactor, but there is spent fuel in the reactor (pool) and Edano said that he assumes radioactive substances are being released. “The substances are coming out from the No. 4 reactor and we are making the utmost effort to put out the first and also cool down the No. 4 reactor (pool).”

Edano said that a blast was heard this morning at Unit 2 at about 6:30 a.m. A hole was observed in the number 2 reactor and he said there is very little possibility that an explosion will occur at Unit 2.

“The part of the suppression chamber seems to have caused the blast,” Edano said. A small amount of radioactive substance seems to have been released to the outside.

TEPCO workers continue to pump sea water at 1, 2 and 3 reactors. “The biggest problem is how to maintain the cooling and how to contain the fire at No. 4.” At 10:22 a.m. Japan time, the radiation level between units 2 and 3 were as high as 40 rem per hour. “We are talking about levels that can impact human health.” Edano said.

Of the 800 staff that remained at the power plant, all but 50 who are directly involved in pumping water into the reactor have been evacuated.

More updates to the above as the fog of uncertainty begins to clear…


Finally, a telling comment from a friend of mine in the US nuclear research community:

The lesson so far: Japan suffered an earthquake and tsunami of unprecedented proportion that has caused unbelievable damage to every part of their infrastructure, and death of very large numbers of people. The media have chosen to report the damage to a nuclear plant which was, and still is, unlikely to harm anyone. We won’t know for sure, of course, until the last measure to assure cooling is put in place, but that’s the likely outcome. You’d never know it from the parade of interested anti-nuclear activists identified as “nuclear experts” on TV.

From the early morning Saturday nuclear activists were on TV labelling this ‘the third worst nuclear accident ever’. This was no accident, this was damage caused by truly one of the worst of earthquakes and tsunamis ever. (The reported sweeping away of four entire trains, including a bullet train which apparently disappeared without a trace, was not labelled “the third worst train accident ever.”) An example of the reporting: A fellow from one of the universities, and I didn’t note which one, obviously an engineer and a knowlegable one, was asked a question and began to explain quite sensibly what was likely. He was cut off after about a minute, maybe less, and an anti-nuke, very glib, and very poorly informed, was brought on. With ponderous solemnity, he then made one outrageous and incorrect statement after another. He was so good at it they held him over for another segment

The second lesson is to the engineers: We all know that the water reactor has one principal characteristic when it shuts down that has to be looked after. It must have water to flow around the fuel rods and be able to inject it into the reactor if some is lost by a sticking relief valve or from any other cause – for this, it must have backup power to power the pumps and injection systems.

The designers apparently could not imagine a tsunami of these proportions and the backup power — remember, the plants themselves produce power, power is brought in by multiple outside power lines, there are banks of diesels to produce backup power, and finally, banks of batteries to back that up, all were disabled. There’s still a lot the operators can do, did and are doing. But reactors were damaged and may not have needed to be even by this unthinkable earthquake if they had designed the backup power systems to be impregnable, not an impossible thing for an engineer to do. So we have damage that probably could have been avoided, and reporting of almost stunning inaccuracy and ignorance.Still, the odds are that no one will be hurt from radioactivity — a few workers from falling or in the hydrogen explosions, but tiny on the scale of the damage and killing around it.

It seems pathetic that Russia should be the only reported adult in this — they’re quoted as saying “Of course our nuclear program is not going to be affected by an earthquake in Japan.” Japan has earthquakes. But perhaps it will be, if the noise is loud enough.

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

378 replies on “Fukushima Nuclear Accident – 15 March summary of situation”

As an engineer – I disagree with your assessment of this situation. This is clearly an engineering/operational failure that should never happen. I will wait to see the damage and loss of life – but if you go back and look at the loss of life assessments by the World Health Organisation following Chernobyl – they were wildly low – on the order of a few hundred. More recent studies have shown that number to be orders of magnitude low.

Nuclear Engineers and Operators are paid to deal with exactly these situations. A failure to foresee this scenario is a systemic error. (Who could have foreseen people flying planes into buildings?)


Clarifying as NHK replays:

783 nuclear fuel rods stored in the pool
Tokyo Electric says it appears a lack of cooling caused the fuel rods to be exposed
Operators … not directly involved in cooling … are being ordered to be relocated

New York Times has much more detail now:

“By late Tuesday, the water meant to cool spent fuel rods in the No. 4 reactor was boiling, Japan’s nuclear watchdog said. If the water evaporates and the rods run dry, they could overheat and catch fire, potentially spreading radioactive materials in dangerous clouds.

Shigekatsu Oomukai, a spokesman for the Nuclear and Industrial Safety Agency, said the substantial capacity of the pool meant that the water in it was unlikely to evaporate soon. But he said workers were having difficulty reaching the pool to cool it, because of the high temperature of the water.

Temperatures appeared to be rising in the spent fuel pools at two other reactors at the plant, No. 5 and No. 6, said Yukio Edano, the chief cabinet secretary.”

I wish they’d put timestamps on their quotes.


While I frequently disagree with you, I can’t thank you enough for this web site and the classy way that you run it.

It must be very discouraging to have your integrity attacked even though most of the attackers come across as dishonest or deranged.

Please hang in there! That Rudyard Kipling quote is appropriate when people are playing the blame game.

Steve Gardner,
Thanks for that excellent “SomethingAwful” link but finding another good site is no reason to disparage this one.


As I have been browsing around this appears to be the best place to get accurate and complete information, including some healthy debate about how safe the situation is. I must admit that firsthand Pr Brook’s comments seemed optimistic.
However as the situation unfolds, he seems to be correct and his explanations are consistent with the facts as we discover them (radioactivity around the plant rising, then dropping rapidly, suggesting quick decaying isotopes). Only problem is that reality has many ways of surprizing us and the worst sin is to be too self confident.


Academic paper on heat transfer from a partially exposed fuel rod:
©2009 American Society of Mechanical Engineers
“A portion of the rod is immersed in a coolant reservoir that is maintained at constant temperature, and the exposed portion of the rod is cooled by convective heat transfer. Because thermal conductivity of the rod is temperature dependent, the governing partial differential equation is nonlinear. The analytical techniques utilized in solving the problem could be applied to analyzing the cooling of spent nuclear fuel rods.”


Len P said:
“The cause of the accident has been sited above, basically lack of backup Quenchers.
3 mile suffered from NRC fears of rapid shutdown and went into a controlled meltdown.”

I am sure that the NRC would be surprised to know that 1) they designed the defect into the TMI plant that caused a valve to remain stuck open, and 2) that the NRC was operating and responsible for operating TMI when the accident happened.

I enjoyed your revisionist history quite a bit.


Something pretty significant happened to cause the boundary monitor at the Daiichi facility to reverse its slow decline and shoot up to 489.8 micro-Sieverts/hour.

The Daini boundary monitors are no longer showing background (13.7 micro-Sv/hour).

Did the fire at the #4 reactor cause either or both of these spikes?


International Journal of Nuclear Governance, Economy and Ecology
Issue: Volume 1, Number 3 / 2007
This is a “what if, worst case” study:

Environmental impact resulting from a fire at a spent nuclear fuel storage facility
(full text PDF available at the linked page)


“Nuclear power reactors have created a significant quantity of used or spent nuclear fuel elements that contain some remaining nuclear fuel and by products of the fission process that are highly radioactive. Lack of a secure central repository or other permanent disposal process for spent nuclear fuel elements has resulted in long term storage of these elements in spent fuel pools at operating nuclear power plants. A recent review of the safety and security of commercial spent nuclear fuel expressed concern that terrorist activity at a spent nuclear fuel storage pool could result in a zirconium cladding fire that could create widespread radioactive contamination with dramatic impact on both the public and the environment. A scenario based on such an event is presented to demonstrate the potential impact resulting from the release and dispersion of spent fuel products.”

Again – that’s a worst case study, but it suggests why this is being taken seriously.


Quoting from the study I just linked above, details:

“The fission products in the spent fuel create very high radiation levels in the area surrounding the fuel. This is particularly true during the first year after the fuel is removed from a reactor, but even ten years after removal of spent fuel from a reactor, the radiation dose 1 metre away from a typical spent fuel assembly exceeds 200 Sv per hour (US Nuclear Regulatory Commission, 2002). Energy produced by the radioactive decay within the fuel elements results in heat. If heat is not removed, the assemblies can reach temperatures that can result in the rupture of the zirconium alloy cladding or even a zirconium cladding fire that can release very high concentrations of the radioactive contents. For this reason, spent fuel elements are typically stored under water in spent fuel pools. Water in the pools serves as a shield to reduce radiation to acceptable levels and as a heat transfer medium to cool the fuel (World Nuclear Association).”


Updated NYT:

“Tokyo Electric Power Company officials announced on Tuesday evening that they would consider using helicopters in an attempt to douse with cold water a boiling rooftop storage pond for spent uranium fuel rods. The rods are still radioactive and potentially as hot and dangerous as the fuel rods inside the reactors if not kept submerged in water.

“The only ideas we have right now are using a helicopter to spray water from above, or inject water from below,” a power company official said at a news conference. “We believe action must be taken by tomorrow or the day after.”

With hydrogen gas bubbling up from chemical reactions set off by the hot fuel rods, the storage pond produced a fire and powerful explosion on Tuesday morning that blew a 26-foot-wide hole in the side of reactor No. 4 at the Fukushima Daiichi nuclear power plant. There were also concerns about the storage ponds at reactors 5 and 6.”

[that “26-foot-wide” hole might be the “8 square meters” hole mentioned above for fire hoses to use. And I’d bet it’s in that sheet metal top level — hr]
[has anyone seen recent pictures of Unit 4?]


hmm, may i ask where this puts spent fuel pool at reactor 3? from the photos/videos it should be up in the air? or they had no spent fuel there?


Those new to the site should look back at earlier topics–Barry Brook started this to discuss Generation 4 nuclear plant designs, which don’t build up large piles of dangerous used fuel and which can actually reprocess used fuel onsite. He was urging the industry (which was reluctant to listen) to switch immediately to finishing the design and testing and start building the best available Generation 4 designs — rather than continuing to build new copies of antique and less safe designs.

Maybe they’ll listen now.
UPDATE 6: 1.52pm GMT Radiation data from IAEA, status of fuel ponds

Fire at unit 4, concern for fuel ponds

Kan’s spokesman Noriyuki Shikata said that there had been “a sign of leakage” while firefighters were at work, “but we have found out the fuel is not causing the fire.” The fire is now reported extinguished.

The International Atomic Energy Agency did confirm that the fire had taken place in the used fuel storage pool. The Japan Atomic Industry Forum’s status report said the water was being supplied to make up for low levels.

Similar to the need to cool fuel in the reactor core, used fuel assemblies in cooling ponds require a covering of water to remove decay heat. The main differences being the amount of decay heat to be removed decreases exponentially with time and that fuel ponds are much less of an enclosed space than a reactor vessel. At the same time, ponds may contain several years of fuel.

JAIF reported that temperatures in the cooling ponds at units 5 and 6 are increasing, but the reason for this is not yet available.”

Researched and written by World Nuclear News

Eric Talmadge and Shino Yuasa

“Japanese officials told the International Atomic Energy Agency that the reactor fire was in a fuel storage pond — an area where used nuclear fuel is kept cool — and that “radioactivity is being released directly into the atmosphere.” Long after the fire was extinguished, a Japanese official said the pool might still be boiling, though the reported levels of radiation had dropped dramatically by the end of the day.

Late Tuesday, officials at the plant said they were considering asking for help from the U.S. and Japanese militaries to spray water from helicopters into the pool.

That reactor, Unit 4, had been shut down before the quake for maintenance.

If the water boils, it could evaporate, exposing the rods. The fuel rods are encased in safety containers meant to prevent them from resuming nuclear reactions, nuclear officials said. But they acknowledged that there could have been damage to the containers. They also confirmed that the walls of the storage pool building were damaged….”


Thanks to Hank Roberts for the additional info.

As for energy, I disagree with DR Lunsford–natural gas has shown to be a safer, more efficient and more inexpensive form than coal or nuclear. We have a surfeit of it and could/should export. The main impediments to its widespread adoption are the powerful coal lobby, the weak natural gas lobby, and the current Administration’s lack of sophistication and education regarding the subject.


Apparently, this type of reactor has been criticized for precisely this type of potential problem for more than 40 years:

“The warnings were stark and issued repeatedly as far back as 1972: If the cooling systems ever failed at a Mark 1 nuclear reactor, the primary containment vessel surrounding the reactor would probably burst as the fuel rods inside overheated. Dangerous radiation would spew into the environment.”

This design is in place in 23 US reactors (16 different plants).


Let me be clear about explosion dynamics. Things don’t just crack and go hiss. A steam explosion is inevitably an enormously violent affair for the same reason in any bursting pressure vessel, the fluid hammer effect. That is why a small hole in a pressurized airplane can lead to its destruction – it’s not the air escaping, its the traffic jam behind the hole. So there have been no pressure vessel ruptures or we’d know about it with large clouds of radioactivity and spectacular steam clouds.

I see that the cable news channels are spouting the same hysteria as yesterday, without any regard for facts. They search for some random nellie to give them a “we’re all gonna die!” sound bite. I’ve come to despise the very sight of any of the countless female news bimbos that pollute the airwaves!!!



BTW my hypothesis about the “loud noises” heard was simply the sound of the hydrogen over the spent fuel pond igniting with a large WOOF, like a gas grill x10^6.



Another idea regarding the noise is – when water vapor cools enough to condense to steam droplets it does it very rapidly. Condensing gas can for example crush a rail tanker car like a soda can. If there were a sudden decrease in water vapor pressure in the torus due to condensation, it would make a very loud groaning noise that would be nothing like an explosion but would be very alarming I’m sure. That would also explain the sudden pressure drop.


Barry has to sleep sometime. It’s early morning there.

I’m grateful for the time he spends throwing out the trash that accumulates here in his absence. I’ll be grateful if he deletes anything I posted that he knows is mistaken or has become outdated, to keep these threads useful for new readers — so new readers can go to the top, read the whole thread, and get good info and see the answers to frequently repeated questions.


Mike P – is that the same natural gas that killed a couple of dozen people in the US last year? Like at Kleen Energy? That’s what you’re calling the safer alternative?

Don’t get me wrong here – methane is a very useful substance, but it requires cultivated ignorance to call it safe.


Is there any reliable curent information about sustained dose levels at the site boudary. I have seen peak dose information, but I am not sure where the dose is measured and how good of a daily average it is. Thanks


Natural gas is a fossil fuel like any other – burning it produces CO2, and widespread production would leak pure methane into the atmosphere, which is 20 times worse than CO2 as a greenhouse gas. The only chance of halting global warming in the next 50 years is to get off carbon fuels now, now, and now.


“The only chance of halting global warming in the next 50 years is to get off carbon fuels now, now, and now.”

Solar. :)

[begin soapbox] Fossil fuels and nuclear have received over hundreds of years (in the case of oil, and 70 years in the case of nuclear) HUGE support from world governments in R&D (just the military budget alone), subsidies, land use breaks, tax breaks, political help, and on and on. Oil and nuclear cost a lot more than the upfront ledger because of this (and the health and environmental costs/prevention). Solar has received a tiny fraction of the support of these technologies. Yet the sun literally bathes the earth in radiation every day. We can put people on the moon and make nuclear power plants but can’t harness solar power effectively? That’s just hogwash. The WILL to do so has not been there. Solar should be able to provide all our energy needs.[/end soapbox]


Thanks Barry for keeping patience. I will weigh in after I finish poking around for information.

Hank, I want to take you back to the fact that keeping the water level in the Spent Fuel Pool is all you have to do. Boiling isn’t good of course when you lose active cooling systems, but uncovering the fuel due to loss of makeup is far worse due to loss of radioactive shielding. Making access to the refuel floor dangerous to add makeup water.

Also refer back to the dry fuel storage post, after about 5 years bundles can be safely stored dry. The decay heat is such that natural convection is more than enough. Bundles are put in a sealed inerted shielded canister and then stored in concrete vaults that allow natural convective air flow around the canisters. Temperature rise is surveilled and monitored for airflow blockages.


So here is an interesting piece of information that appeared in Japanese bulletin boards. Not sure about the veracity of it but this one at least seems plausible to me. Apparently one of the workers at the Daiichi plant posted that the reason they were hesitant to cool off the plant with sea water is that their monitoring instrumentation would fail if exposed to sea water. So now they actually have to physically go into the damaged plant to take measurements and observe. Furthermore the person who claims to be a worker at the plant said that the valve that got stuck did so due to salt accumulation from the seawater. He went on to say that workers go in now in 20 second rotations to minimize radiation exposure. A fact that makes this post more credible is that he posted that they were able to open the valve a short time before they actually announced it officially. He also commented on the fact that many of the workers left behind do not know the fate of their families who live in the immediate vicinity of the plant but given the circumstances they need to keep managing the situation at the plant. Anyone care to comment?


That NYTimes report Hank linked to, i.e.

also reports that “a separate explosion ruptured the inner containment building at reactor No. 2 “.

Does this seem to be a valid description of what is known?

The report appears to define what is labelled in the containment building diagram as the “reactor building” to be an “outer containment” which would allow a description of a rupture in the concrete “light bulb torus” or the pressure suppression chamber to be defined as an “inner containment”.

The NYTImes is running another story that appears to say the GE Mark 1 containment would fail in a light breeze of some kind. Well, not quite that bad, but if I was to take what it says as gospel, along with what they’ve reported has happened to some of the reactors, all the containments must have failed by now. Its probably like Wile E Coyote running off a cliff but not falling until he realizes he isn’t standing on the ground anymore. The containments have failed and the consequences won’t happen until we realize that they’ve failed.

Eg: “Harold Denton, an official with the N.R.C., asserted that Mark 1 reactors had a 90 percent probability of bursting should the fuel rods overheat and melt in an accident. A follow-up report from a study group convened by the commission concluded that “Mark 1 failure within the first few hours following core melt would appear rather likely.” In an extreme accident, that analysis held, the containment could fail in as little as 40 minutes.”

Read all about it:


“What is likely to happen if there is a crack in the containment structure and there is no roof on the concrete reactor building? The concrete building for the unit 2 is still intact, but given that the concrete buildings for the units 1 and 3 blew up, I’m concerned about its future durability.”

The reactor building roof did not blow up at Unit 1 or Unit 3. The thin steel shed which is built over the top of the concrete walls and concrete roof of the reactor building proper, where the refueling crane is kept, on top of the reactor building, is where the hydrogen accumulated and blew up.


Heres is some facts I believe to be true and looking for someone to dispute or confirm.

Unit 1 is a BWR 3, Unit 2 and 3 are BWR 4’s.

All 3 Units of concern have Mark 1 Contaiments with a Torus as the “Suppression Chamber”.

All three units have experienced challenges with Hydrogen generation and venting of the primary containments.

Units 1 and 3 have had hydrogen explosions inside the secondary containment (Reactor Building). There seems to be some existing concern for hydrogen buildup in Unit 2 too.

Barring someone proving these believed facts as reported wrong, I have to conclude that the vent path for the Torus at least units 1 & 3 resulted in hydrogen buildup in the secondary containment (reactor building).

Possibly the hard piped modification for torus venting to the stack was not implemented or implemented to the existing reactor building ventilation system. Without power for fan dilution, this would collect on the refuel floor and result in the explosions seen on units 1 & 3.

This Mark 1 Containment modification was designed due to the limited volume size and heat removal capability. I am not sure the effects of a complete station blackout, loss of ventilation were considered if not done directly to the stack.

Only now we are seeing the effects of minor fuel damage on Units 1 & 3 generation of hydrogen and inability to direct vent it to save both containments. I say minor as in I believe the reported doses associated with venting from unit 1 & 3 only indicate clad damage, not significant fuel damage.

Unit 2 fuel damage is more significant due to extended dryout conditions. I have seen a reputable estimate of 5 % damage. That damage is fuel and beyond clad damage leakage.

There is no real win scenario at this point and people need to understand that. It’s all about limiting the fuel damage and releases. All 3 of these Units are now defunct.

I commend those that are there battling this right now. Remember even if they leave they likely lived in the immediate area which is wiped out by the tsunami. They may not even know the status of their loved ones. Going home is not an option. Pray for them to have strength to continue on.


Thanks em1ss. Do you have any references on how clean the water around the wet fuel storage should be, do they clean it? I saw a reference to a “crud removal” accident somewhere else, and some speculation that salt water would increase corrosion problems. Same would apply to the common spent fuel pool that’s somewhere else on the site at ground level, and to the warehouse for the dry canister storage — is sea water from the tsunami going to be a problem? I’d think it likely the temperature sensors are out throughout the area, and I haven’t seen anyone report on the longer-term fuel storage locations yet.


“… fuel assemblies that have been removed from the reactor are stored under water in the Spent Fuel Pool. Good water quality is important to prevent degradation and to help maintain the integrity of the spent fuel assemblies.
A key function of Fuel Pool Cleanup is removal of soluble and insoluble radioactive species. This is important for controlling dose rates on the refuel floor and work areas/platforms during a refueling outage. For BWRs, a RWCU system outage is normally required for system maintenance. Fuel Pool Cleanup is relied upon to remove impurities from the refuleing cavity water….”

That’s about routine operation, but I’d expect there are studies done on corrosion rates and impurity levels (and that the results of flooding with ocean water will be, eventually, well documented).


I rambled a bit there to clarify, I am not sure the hydrogen generation element was fully known or that units 1, 2 and 3 actually implemented a direct vent to the stack which would have prevented a secondary containment hydrogen buildup like we are seeing play out.


Hank, cleanup is the least of your worries at this point. All 3 Units are done. Corrosion is long term, cooling and shielding is paramount…..


PS, for reference (I posted this long ago in one of the older topics, I’ve seen it cited by others)

November 2010 status survey of the wet and dry spent fuel storage at the site. Lots of detail here:

Integrity Inspection of Dry Storage Casks and Spent Fuels at Fukushima Daiichi. Nuclear Power Station. Yumiko Kumano. Tokyo Electric Power Company. ISSF 2010: Session 6. 16 November 2010

Click to access 6-1_powerpoint.pdf


Here’s a different link to that powerpoint:

Click to access 6-1_abstract.pdf

Related (found by searching on the title of the ‘Integrity Inspection’ powerpoint, when I realized the above link is to a copy at a second-hand source — it’s been copied around, but we ought to aim for primary sources at original sites I think).

Operating Experience in an On-Site Interim Storage Facility ….Storage Status of Spent Fuel at Fukushima-Daiichi NPS. …. Modified the license in 1994 / dry cask storage since 1995 … Outline of Integrity Inspections. Time Series.


Gerald, I would tend to believe your post to be entirely true. Once you get beyond injecting pure water sources, things go wrong. I also recognize the efforts and personal conflicts that have to be going on for those that are combating the issue. This is likely the least played media story in my opinion. The human aspect of those that remain to fight the fight against decay heat.


Hank, you are saturating the post with stuff people can’t understand beyond dry fuel storage is safe… relax. We need to know the status of Radiation levels and reflooding reactor 2. I am not ready to make a call based on my poking around the reports yet.


em1ss, yes, agreed, cleanup is longterm (and I realize the whole area of the disaster is in need of clean drinking water supply, so usihg sea water for the power plant and fuel storage basins is the right shortterm answer). I’m curious whether anyone has seen info on the condition of the longterm common fuel storage pool and dry cask storage building — which presumably got the same impact from the tsunami (remembering that the diesel storage tanks were reported to have washed away). I don’t know the location of either storage site on the site map so the pictures don’t tell me anything and I haven’t seen it discussed anywhere.

According to the “Operating Experience in an On-Site Interim Storage Facility ….Storage Status of Spent Fuel” (10-b Powerpoint), at June 2010, the storage for Daiichi was at 84 percent of capacity, and for Daini at 78 percent. Quantities are given for the spent fuel pools (one at each reactor), a common fuel pool for the whole plant site, and a dry cask storage for each plant site.


> em1ss
> stuff folks can’t understand

It’s being written about many places (major newspapers/websites, a lot of “anti” websites and political websites, radio broadcasts) — most of that so far elsewhere fails to cite any sources and much of it is just scared-and-ignorant.

That’s why I brought it up here — the info available that I’ve found is mostly _very_reassuring_ and I think worth pointing to, in hopes knowledgeable people like you will help people understand it.

Yes, it’s hard. But there are people contributing to misunderstanding out there many places. Push back where you can, at least point to good info if you know where to look at it.


Last measurement of pool temperature: 84 deg C.

Now unable to measure pool temperature due to non-functioning instrumentation.

Water delivery by helicopter (through the roof) deemed impractical for a several reasons (small amount of water able to be delivered, distance between hole in roof and pool itself).

“High” levels (numbers not documented) of radiation in the pool area are preventing closer access to the pool. They are considering other options, such as delivering water by fire truck.


This for example, I hope the worst part of it is wrong. They don’t cite sources for the bad news statements:
so I won’t repeat them.

The more reassuring info in that story–a paragraph dropped in between alarming claims–is cited to the usually cautionary U.C.S.:
“All they need to do with the spent fuel pools is make up for the amount of water evaporating or boiling away,” said David Lochbaum, director of the nuclear safety project at the Union of Concerned Scientists, said at a press conference Tuesday. “They should be able to do that, which should give them time to get cooling restored.”


Ok, it’s playing out much like I had conjectured. Read this IAEA report.

They are considering pulling panels off the reactor building on units 5 and 6 and contribute the torus issue/leak on unit 2 to a hydrogen buildup or possible pressure spike.

Weak link, direct path vent from the torus for units 1,2 and 3 to the stack in my opinion.

For the shutdown units 4, 5 & 6 a direct vent path from the refuel foor.

This could be a concern that will sweep the entire BWR industry.


[…] Fukushima Nuclear Accident ? 15 March summary of situation …: The situation surrounding the Fukushima Nuclear Accident, triggered by Japan’s largest recorded earthquake and the resulting 10 m high tsunami, continues to develop rapidly. This post is intended to be a concise update of the situation as of 12pm Japan Standard Time, 15 March 2011. For a summary of the situation prior to today, read … – Readmore […]


Hank, don’t confuse ground water cleanup with site cleanup. Until we have proof the ground water has been affected it only raises concerns that are not yet proven. Facts, just the facts. If you want to post conjecture, preface it.

The situation is not good or stable, but the facts are most of the area is likely desolate post tsunami, there is nothing left there. Total destruction due to the tsunami and we should respect those that have already died first.


I had not mentioned anything about groundwater or even thought about it. Why do you bring that up?
If you saw any mention of that, please cite a source.

I’ve asked about the condition of the common spent fuel storage pool and the dry cask storage building.

Those are both described in the Powerpoint files.

I ask here _because_ there is a lot of speculation elsewhere. Saying not to ask is not helpful.

So I’ll quit asking, because arguing about it is worse.
Someone will know and we’ll hear when we hear.



This document from TEPCO’s site contains lots of facts and figures about their nuclear facilities and specifically details the spent fuel storage at Fukushima Daiichi and Daini. (Amount of spent fuel storage, storage capacity, specific dimensions, types of equipment and accessories.)

Click to access nuclear-e.pdf

This one describes their safety procedures.

This one describes the specific structures in use at TEPCO’s plants.



I was just listening to the news, and heard both Donald Trump and Rudy Guliani give their thoughts on this matter. Rudy actually said that not only do they not know what’s happening at these reactors, but that nonone really knows what happens in nuclear reactions, and that they are not 100% predictable in reactors… Why are these uninformed pundits given the opportunity to spread misinformation, especially with such profoundly incorrect opinions; and moreover, why are the news channels not correcting them or challenging their opinions? Sadly, truth and prudence do not sell advertising dollars, but future presidential candidates who spout nonsense do.

Thanks for keeping this updated. Everyone out there should seek all sources of information on the subject and make their own informed decisions based on all available information. The link above from cnbc further drives this point home in their concluding comment about the Japanese government “throwing in the towel” as if it were just evacuating everyone and letting these reactors melt completely and giving up. Such conjecture is absurd, and blatantly spreading fear with little foundation. The media is shameful.


Hank, i am not trying to shut you off with your comments. Maybe I misunderstood your post. Conflict is good and spurs enagaged thinking.


the roof of reactor 4 has collapse, is reported by some german media. possibly another explosion. 2 workers are missing.

the all of this is only a delay action.


Sorry, my above post referred to reactor #4 at the Daiichi plant.

Also, on the link I posted above I just noticed the associated NHK TV news story showing a cartoonish map of the building interior (around 01:22).

On the lower left, one can see the destroyed portion of the building. In the middle is the reactor (circle), and directly next to that (square) is the fuel storage pool. The distance between the pool and the hole in the building is reported as “several tens of meters”.


BBC radio just said the company has now said there have been four explosions when earlier they had only said three — no detail, followed by a comment that contradictory information was being given and the situation is confused.


Hat tip on that 1982 article, I read about it here:

“The problem of containment over-pressurization and the potential need to vent has been a long-term issue in the nuclear reactor safety community. In 1977, a group of nuclear engineers at the University of California suggested that a robust filtration system be installed in reactors to remove the radioactivity from the vented gases. Some countries picked up the idea. Sweden installed a filtered vent system at the Barseback reactors (subsequently shutdown) across the strait from Copenhagen and France installed filtered vent systems at all of its reactors, which interested both Germany and Japan.

In 1982, after the accident at Three Mile Island, Jan Beyea and I wrote an article on filtered vents in the Bulletin of the Atomic Scientists in 1982 (page 52). As we reported in that article, the US Nuclear Regulatory Commission (NRC) was negative about the idea. They had a number of arguments but none of them seemed very strong to us. Those interested can read our summary of the arguments pro and con in the 1982 article….”


3 units with Mark 1 Containments suffer beyond design basis accidents concurrently, at least with in one hour as the tsunami happened.

Units 1 and 3 seem to be stable based on operator action as prescribed.

Unit 2 has suffered real fuel damage due to uncovery of the fuel, estimated to be IEA at 5% and is recovering cooling. I have to believe that estimate as it requires certain values of measured exposure and airborne release.

Primary containment remains questionable based on rapid pressure change and points to a Torus loss of containment. This doesn’t imply a complete loss of the suppression fuction, just the containment function.

Success, keep flooding unit 2…. enough said.


A closer to “worst case” would be a full SCRAM failure or equivalent – terrorism a potential cause. A run-away fission reaction is a nightmare scenario, much more “worst case” and something that rolls around in most peoples minds. Fear almost never correlates with probabilities.


sod, the 2 missing workers were missing from the earthquake/tsunami, not from subsequent events(source: BBC live page)


might be that the press got that one mixed up, though one of the reports said, that they were last seen close to reactor 4.

BBC is also reporting the new fire.

the simple truth is: reactors 1 to 3 are lost. and reactors 5 and 6 will follow reactor 4.

this is not good news.


Questions re: core fuel rods melting – If the rods melt (ceramic?) what are the thoughts of both control and fuel rods – which melt first and likely outcome visa vi effect on negative absorption of neutrons? I expect there has been lots of modeling done but this could be the first event involving this type of core/cooling design?


This is from before the recent explosion and roof collapse at Unit 4, after the first fire there was put out:

“Initial reports attributed the fire to hydrogen gas generated by reaction of the zirconium sheathing on the fuel rods with water, which would suggest a fairly high degree of danger. On Tuesday morning, however, Anthony R. Pietrangelo, chief nuclear officer of the U.S. Nuclear Energy Institute, said the fire was actually a lubricating oil fire, which would be much less serious.

Reports from the scene indicate the water in the cooling pond is boiling vigorously and engineers fear it will soon boil away, exposing the fuel rods, which would allow them to melt. That could have even more disastrous consequences than a meltdown inside the reactor because the fuel rods in the pond are not enclosed in a reactor containment vessel.”


And from NPR:

“New Fire Hits Japan Nuclear Plant
A new fire broke out Wednesday in an already fire-damaged reactor at a crippled nuclear power plant in Fukushima, Japan. Concerns are growing about the state of overheated spent fuel rods in the reactor. Radiation levels are far too high to permit workers to bring hoses anywhere near the pool’s edge to re-flood it manually.”



“… According to NHK television, officials at Tokyo Electric Power Co. decided a hole in the roof of the reactor was “dozens of meters” from the swimming-pool-like chamber where the spent fuel rods are overheating. So a helicopter dump, similar to putting out a forest fire, probably wouldn’t reach the pool.

Moreover, officials say helicopters can’t carry enough water to do the job. And Japanese defense ministry officials are worried about the safety of military personnel on the helicopters, according to Kyodo News.

TEPCO, which operates the Fukushima power plant, is still considering the use of high-pressure fire hoses to spray cooling water into the spent-fuel pool.

Radiation levels are far too high to permit workers to bring hoses anywhere near the pool’s edge to re-flood it manually.

U.S. nuclear safety experts agreed. David Lochbaum, director of the nuclear safety program at the Union of Concerned Scientists, says a study done for Connecticut nuclear power plants concluded that in a situation such as this one, radiation would be so intense that a worker at the pool’s edge “would receive a lethal dose in something like 16 seconds.”

The spent-fuel problem is a new wild card in the potentially catastrophic failure of the Fukushima power plant. Since last Friday’s 9.0 earthquake, the plant has been wracked by repeated explosions in three different reactors.

Some experts are now concerned that spent fuel rods may overheat in two other reactors, even though they were not in service at the time of the earthquake. Those two units, Nos. 5 and 6, have not yet reported problems.

“There are accounts that they’re having difficulties cooling those three spent fuel pools and they need to regain control of that,” says Lochbaum, a nuclear engineer by training. “Or as a minimum, need to be able to replace the water that may be evaporating or boiling away to prevent the water from dropping below the level of irradiated fuel in the bottom of those spent fuel pools to prevent their damage from overheating as well.”

Radiation Concerns From Spent Fuel Rods

The problem at reactor No. 4 was apparently brewing for some time before Tuesday’s fire. The company says the temperature of the spent fuel pool reached 183 degrees Fahrenheit on Monday – twice the normal level. It apparently went higher, but a “technical failure” prevented later readings…..”


the spent fuel pools can be seen on the structure graph of the reactor, which Barry has posted a couple of times.

it is an open pool, just protected by the roofs, whioch got blown away by now.

Debris falling back after the explosion could have fallen into the pool, removing water, throwing rods out, blocking circulation systems.

people here are taking those explosions not serious enough.


The radiation levels on site determine if the spent fuel is uncovered… Reliable indications of those levels, not airborne radiation levels which could be affected by release rates from the various reactor containments right now determine if the pool level has gone below shielding levels…. That is worst case for any spent fuel pool on site….


Is there a source to explain the news story about Unit 4 roof pool quoted above? that said

“Radiation levels are far too high to permit workers to bring hoses anywhere near the pool’s edge to re-flood it manually.”

It seems the information is not made public — that’s what the news reporters all seem to be saying. Then they give statements but not sources for them.


Hank, this doesn t take any more than common sense. the roof pool contains fuel rods. it is open and burning.

the only thing i would move close to it, is a fireengine tank combination. and such a vehicle would need to bring a water (or whatever) pipe AND cross the debris of 4 big explosions.

i expect them to have good firefighting equipment on site, but i am having doubts against this one.

and reactor 5 and 6 will follow. and that is something that the owners are worrying about!


Much earlier I wrote regarding my (entirely lay) perception that there seemed to be a plethora of comments on this site saying essentially that everything is really okay and the Japanese have things in hand, with such comments then seeming to be made not just wrong but indeed perhaps even foolish within hours given new developments.

For what it’s worth then it seems to me that with one prominent exception what I am seeing now is people smartly not being so sanguine given that with each new bit of information that has emerged it seems that all is just worse and worse and worse.

I see now for instance that there’s a new fire at #4. That it’s felt that helicopters probably can’t be used to dump water. That high levels of radioactivity are seriously degrading the ability for workers to do their thing at the plant.

Just my lay opinion, but it seems to me that the people to be most respected on this issue right now are saying that they just simply flat don’t know what the real fundamental situation is, nor know all of what might further happen, nor how (further) bad it might get, period. And that any confident forecast, regardless of same being either optimistic or pessimistic, is just smoke, pure and simple.


Although I am not pro-nuclear I have to thank you for the clear and precise information you have posted during these days.
Please keep doing it since people like me, not very familiar with the matter, are very scared watching the news, especially those blinking “breaking news” announcing something catastrophic. I am not saying that this is not, but I notice the big difference on my reaction in reading your posted information and those given by CNN with such a stir.
Thank you


Without being alarmist:

1) what guarantees can be made about the continued integrity of the Fukushima plants if all workers were forced to evacuate the plant in its current state?

2) what guarantees can be made that all workers will not need to be evacuated from the plant?


> sod
> this doesn t take any more than common sense.

Speculation isn’t helpful. Common sense isn’t enough to know what’s going on. NHK television right now, typing as I listen:

“the workers could not enter the building … after half an hour the fire extinguished on its own … there is an urgent need for water … a storage pool … temperature was 84 degrees C on Monday … more recent temperatures are not available due to a technical failure .. it appears a lack of coolant caused the fire … [not clear but suggesting] fuel rods exposed … could melt down … urgent measures should be taken … using the generator of the No. 6 reactor”

Not clear — “generator of the No. 6 reactor” –?


“The Japanese government is now saying the fire in reactor 4 is “under control”, according to the AFP news agency.”… BBC live page


It’s slightly academic, because the Fukushima Daiichi evacuation zone overlaps, but has the Fukushima Daini evacuation advisory been lifted?


TEPCO say that they are considering dispersing boric acid on reactor 4.

Did they try to manage the big radiation level with that ?


If humans can’t lay hose to the spent fuel pools, can a remote?
This is a great opportunity to make a sales video for iRobot’s packbot.
Are remotes too delicate to handle the radiation environment too?


Barry on the 12th you wrote: “1. There is no credible risk of a serious accident.” Currently all experts rate the event as a INES 6 event, that is “a serious accident” by official definition.

How could this happen, if there was “no credible risk” of this happening? I was intrigued by your seemingly well informed blog and I’m not a fan of fear mongering. On the other hand I’m not a fan of downplaying risks either and it seems to me that you downplayed the risks.


NHK has shown Tokyo Electric interviews with scrolling text below in English more or less matching what the translators are saying, and has pictures from overhead showing what appears to be the same two white steam plumes from the No. 3 reactor that have been present for a day or more, and smoke apparently from the No. 4 building

ACTUAL measurement given:

NISA interview being shown on NHK with a closeup of a very large wall size drawing of the cooling pool showing the location of the fuel rods in the racks.

Then they switch to a NHK reporter showing a cross-section, pointing to the cooling pool and talking about the hole in the roof and need to get water into the cooling pool

My typing, as I hear the translation:

“the radiation was very high and the area was inaccessible … since yesterday … 300 to 400 millisieverts, that is very radioactive and if people are exposed to this level … workers cannot access the area.

Q: how are they going to extinguish the fire?
[ I think meaning when the hydrogen builds up again]
A: TEPCO is saying … yesterday’s fire went out naturally, and I guess they are trying to observe what will happen …

Q: what is the danger level?
A: … could be helicopters … could be fire engine … hole on the wall, water could be injected from the side but it is not decided for sure because of the difficulties …

But NHK is now back to something they played yesterday — it is very hard to tell what’s new and what’s old here.


It seems to me the reactors are in hand, but this approach of “we’ll just pop those spent fuel rods in a pool in the attic” clearly has some serious flaws.


@mattb – you could have the pool at ground level… (in fact Fukushima Daiichi plant does have such a pool) … and then you get a tsunami…

I believe that the in-building spent fuel pool is level with the top of the reactor vessel to facilitate underwater fuel rod transfers, but I could be mixing it up with another design.


“ISIS assesses that the situation at the Fukushima Daiichi nuclear plant has worsened considerably. The explosion in the Unit 2 reactor, the third so far, and the fire in the spent fuel pond in the reactor building for Unit 41 means that this accident can no longer be viewed as a level 4 on the International Nuclear and Radiological Events (INES) scale that ranks events from 1 to 7. A level 4 incident involves only local radiological consequences. This event is now closer to a level 6, and it may unfortunately reach a level 7.”


“The emergency at the Fukushima Daiichi Nuclear Station, 150 miles north of Tokyo, could now be classed as a six on an international scale of one to seven, the head of France’s Nuclear Safety Authority said at a news conference in Paris on Tuesday.”


“Victor Gilinsky, who was the senior commissioner on duty at the US Nuclear Regulatory Commission during the Three Mile Island disaster, told Channel 4 News the situation in each unit at Fukushima is more serious than the whole of the Three Mile Island incident.

He said: “At Three Mile Island, there wasn’t any loss of power and the equipment functioned. The mistake was that people turned off the emergency cooling, thinking that that was the right thing to do, and fortunately two hours later there was a change in shift and and the operators turned the cooling back on. And that pretty much ended the accident. … As it is, in the first two hours, half the fuel melted.

“If it (Fukushima) does get worse, you can have all the fuel melting. I expect a substantial fraction of the fuel melted in each of these reactors and slumped down.

“As far as they know, the water level is about halfway up. If it gets worse than that and they lose all the water, then the melted fuel – and there are tens of tons, nearly a hundred tons of fuel in a large reactor – that could melt right through the bottom of the pressure vessel.

“The surrounding building … is not designed to hold that. And it’s just unclear what happens at that point. And it becomes much more accessible to the environment.”

“Two workers are missing after Tuesday’s explosion at one of the reactors at a crippled Japanese nuclear plant, the country’s nuclear safety agency said.”



> Mike Jones

The PDF you cited does not say that. It has a revision date 3/15/11.

It describes cooling failure causing a slow boiling away of water, which matches the course of events so far.

If one of the pools had cracked open someone would have noticed a huge flood of mildly radioactive water pouring down through the building. That hasn’t been mentioned.

It does look like their estimate of how long it would take to boil the water off, and how easily a cooling system failure could be coped with, was far too optimistic. Is there more or hotter fuel stored in the pools than planned for in the design spec? That’s a guess — all such plants have been for years storing used fuel in what was meant to be a brief temporary holding tank.

” The rate at which the pool water level would decrease (due to evaporation or mild boiling) in the absence of cooling system function would not be expected to lower water levels by more than a few percent per day. Given that there is approximately 16 feet or more of water above the used fuel assemblies, operators would have ample time (days to weeks) to find another way to add water to the pools before the fuel would become exposed. For example, water could easily be added using a fire hose.”

Well, no, that didn’t work. And they in that document neglected to consider that radiation levels above the pools would be high even before fuel rods were actually exposed, as 16 feet of water makes pretty good shielding but less water, less shielding.



This is the latest kyodo report
Fire broke out in the number 4 reactor building this morning at 5:45. It is in the same location as yesterday, the forth floor north west corner. There has been no reports of any explosion. The fire was discovered by a worker returning a battery

Sorry if my translation isn’t so good

It doesn’t say anything about radiation or the status of the spent fuel… If anyone has some real info, I’d like to know so I can get my arse out of japan if need be


Dr. Brook…add me to your list of appreciative readers. Your blog is one of a select few I’m checking for factual(as is possible) info. Keep fighting the good fight for information instead of histrionics.


Alvarez calculated in 2003 that the dose rate from half exposed rods in a typical spent fuel pool would be 140 Sv/h at the pool edge, or in other words a fatal dose in about 2 minutes.

That kind of explains why it will be difficult to get a fire hose in there to refill the pool. Even at 400 mSv/h measured outside the reactor buildings, you couldn’t work for more than two hours without risking radiation sickness (and only a few minutes if wanting to respect maximum regulatory dose rates that give ample protection against cancer risk increases).


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