Hot News Nuclear

Discussion Thread – Japanese nuclear reactors and the 11 March 2011 earthquake

Please use this Discussion Thread for the situation in Japan with respect to the Miyagiken-Oki earthquake (9.0 magnitude) and associated 10m tsunami, and its impact on the local nuclear reactors. Here is a précis of the situation as I understand it:

1. There is no credible risk of a serious accident. All reactors responded by insertion of control rods to shut down their nuclear reactions. Thus, power levels in all cases dropped quickly to about 5% of maximum output,  and the nuclear chain reaction ceased (i.e., all units are subcritical).

Note: I judge the situation would currently be rated INES Level 4: Accident with local consequences on the international nuclear event scale. Update: This level has been confirmed by WNN (5:50 GMT).

2. The concern is providing emergency cooling water to the reactor cores to remove decay heat from the fuel rods. This residual heat comes from the fission products, and will be persistent, but diminishes rapidly over time (i.e., most decay heat occurs over minutes and hours, with cold shutdown within a few days).

3. At one plant, the 40-year old Fukushima Daiichi (unit #1 opened in 1971), the backup diesel generators supply power to the core cooling system failed (apparently due to damage from the tsunami). This allowed pressure to build up in at least one of the reactors cores to about 50% higher than normal (unit 1), and requires venting of very mildly radioactive steam (contains trace levels of tritium). Some discussion here.

4. The nuclear reactor containments were undamaged by the tsunami or earthquake — these structures are sealed from flooding damage and are seismically isolated.

5. New generators and batteries have been transported to the Daiichi site in to provide power to the pumps. The emergency core cooling systems (ECCS) have been invoked, which follows the principle of defense in depth (however, see point #8, below, and TEPCO updates).

6. There are reports of partial exposure of the fuel at Daiichi unit #1, following coolant evaporation that, for a short time, exceeded inputs from the secondary cooling system. Such exposure can lead to some melting of the metal cladding (the ‘wrapping’ of the fuel rods), or the uranium rods themselves if the exposure is prolonged. This is what is technically referred to as a ‘meltdown’. I am still not clear if this exposure of the fuel assemblies actually happened (some evidence here), nor if any fuel underwent melt (due to decay heat, not a critical nuclear reaction).

7. The plant closest to the earthquake epicentre, Onagawa, stood up remarkably well, although there was a fire in a turbine building on site but not associated with the reactor operations, and therefore was not involved with any radioactive systems.

8. There has been an explosion at Fukushima Daiichi at 16:30 JST (7:30 GMT) on March 12. Note: There is no critical nuclear reaction occurring in any of these reactors, and it CANNOT reinitiate as all neutron-absorbing control rods are grounded. As such, any at a plant site fire would be chemical (e.g., hydrogen) or steam pressure during venting (see point #3).

Quote from WNN on the explosion:

Television cameras trained on the plant captured a dramatic explosion surrounding Fukushima Daiichi 1 at around 6pm. Amid a visible pressure release and a cloud of dust it was not possible to immediately know the extent of any damage. Later television shots showed a naked steel frame remaining at the top of the reactor building. The external building structure does not act as the containment, which is an airtight engineered boundary within.

Chief cabinet secretary Yukio Edano appeared on television to clarify that the explosion had damaged the walls and roof of the reactor building but had not compromised the containment.

Monitoring of Fukushima Daiichi 1 had previously shown an increase in radiation levels detected near to the unit emerging via routes such as the exhaust stack and the discharge canal. These included caesium-137 and iodine-131, Nisa said, noting that levels began to decrease after some time.

Nevertheless the amount of radiation detected at the site boundary reached 500 microSieverts per hour – exceeding a regulatory limit and triggering another set of emergency precautions. It also meant the incident has been rated at Level 4 on the International Nuclear Event Scale (INES) – an ‘accident with local consequences’.

Note: The seawater might be used for spraying within the containment, for additional cooling, rather than injection into the reactor core. That is what comes of too much uncertainty and too little hard information.

Japan Chief Cabinet Secretary Yukio Edano, via Reuters:

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…

Edano said due to the falling level of cooling water, hydrogen was generated and that leaked to the space between the building and the container and the explosion happened when the hydrogen mixed with oxygen there.

(I will edit the above section and provide further updates below, as more information comes to hand)

Some useful links for further information:

Battle to stabilise earthquake reactors (World Nuclear News)

Factbox – Experts comment on explosion at Japan nuclear plant (some excellent and informative quotes)

ANS Nuclear Cafe updates (useful news feed)

How to Cool a Nuclear Reactor (Scientific American interview with Scott Burnell from the NRC)

Nuclear Power Plants and Earthquakes (World Nuclear Association fact sheet)

Tokyo Electric Power Company updates here and here (the plant operators)

Capacity Factor: Some links on the Fukushima Daiichi #1 crisis (with updates)

This is a critical time for science, engineering and facts to trump hype, fear, uncertainty and doubt.


Updates Below
International Atomic Energy Agency: Japan nuclear plants nearest earthquake safely shut down

TEPCO updates for Fukushima Daiichi (Plant #1) and Daini (Plant #2): 8 am, 13 March

[Nuclear Power Station]
Fukushima Daiichi Nuclear Power Station:

Units 1 to 3: shutdown due to earthquake

Units 4 to 6: outage due to regular inspection

* The national government has instructed evacuation for those local residents within 20km radius of the site periphery.

* The value of radioactive material (iodine, etc) is increasing according to the monitoring car at the site (outside of the site). One of the monitoring posts is also indicating higher than normal level.

* Since the amount of radiation at the boundary of the site exceeds the limits, we decide at 4:17PM, Mar 12 and we have reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5PM, Mar 12.

* In addition, a vertical earthquake hit the site and big explosion has happened near the Unit 1 and smoke breaks out around 3:36PM, Mar 12th.

* We started injection of sea water into the reactor core of Unit 1 at 8:20PM, Mar 12 and then boric acid subsequently.

* High Pressure Coolant Injection System of Unit 3 automatically stopped. We endeavored to restart the Reactor Core Isolation Cooling System but failed. Also, we could not confirm the water inflow of Emergency Core Cooling System. As such, we decided at 5.10AM, Mar 12, and we reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5:58AM, Mar 13.

In order to fully secure safety, we operated the vent valve to reduce the pressure of the reactor containment vessels (partial release of air containing radioactive materials) and completed the procedure at 8:41AM, Mar 13,

* We continue endeavoring to secure the safety that all we can do and monitoring the periphery.

Fukushima Daini Nuclear Power Station:

Units 1 to 4: shutdown due to earthquake

* The national government has instructed evacuation for those local residents within 10km radius of the periphery.

* At present, we have decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) in order to fully secure safety. These measures are considered to be implemented in Units 1, 2 and 3 and accordingly, we have reported and/or noticed the government agencies concerned.

* Unit 3 has been stopped and being “nuclear reactor cooling hot stop” at 12:15PM.

* The operator trapped in the crane operating console of the exhaust stack was transferred to the ground at 5:13PM and confirmed the death at 5:17PM.

Kashiwazaki Kariwa Nuclear Power Station:
Units 1, 5, 6, 7: normal operation

Units 2 to 4: outage due to regular inspection

From Margaret Harding:

Heat from the nuclear fuel rods must be removed by water in a cooling system, but that requires power to run the pumps, align the valves in the pipes and run the instruments. The plant requires a continuous supply of electricity even after the reactor stops generating power.

With the steam-driven pump in operation, pressure valves on the reactor vessel would open automatically as pressure rose too high, or could be opened by operators. “It’s not like they have a breach; there’s no broken pipe venting steam,” said Margaret E. Harding, a nuclear safety consultant who managed a team at General Electric, the reactors’ designer, that analyzed pressure buildup in reactor containments.

You’re getting pops of release valves for minutes, not hours, that take pressure back down”

IAEA alert log:

Japanese authorities have informed the IAEA’s Incident and Emergency Centre (IEC) that today’s earthquake and tsunami have cut the supply of off-site power to the Fukushima Daiichi nuclear power plant. In addition, diesel generators intended to provide back-up electricity to the plant’s cooling system were disabled by tsunami flooding, and efforts to restore the diesel generators are continuing.

At Fukushima Daiichi, officials have declared a nuclear emergency situation, and at the nearby Fukushima Daini nuclear power plant, officials have declared a heightened alert condition.

Japanese authorities say there has so far been no release of radiation from any of the nuclear power plants affected by today’s earthquake and aftershocks.

Tsunamis and nuclear power plants:

Large undersea earthquakes often cause tsunamis – pressure waves which travel very rapidly across oceans and become massive waves over ten metres high when they reach shallow water, then washing well inland. The December 2004 tsunamis following a magnitude 9 earthquake in Indonesia reached the west coast of India and affected the Kalpakkam nuclear power plant near Madras/Chennai. When very abnormal water levels were detected in the cooling water intake, the plant shut down automatically. It was restarted six days later.

Even for a nuclear plant situated very close to sea level, the robust sealed containment structure around the reactor itself would prevent any damage to the nuclear part from a tsunami, though other parts of the plant might be damaged. No radiological hazard would be likely.

World Nuclear News updates (updated 11:44 pm GMT):

Attention is focused on the Fukushima Daiichi and Daini nuclear power plants as Japan struggles to cope in the aftermath of its worst earthquake in recorded history. An explosion on site did not damage containment. Sea water injection continues after a tsunami warning.

Three of Fukushima Daiichi’s six reactors were in operation when yesterday’s quake hit, at which point they shut down automatically and commenced removal of residual heat with the help of emergency diesel generators. These suddenly stopped about an hour later, and this has been put down to tsunami flooding by the International Atomic Energy Agency (IAEA).

The loss of the diesels led the plant owners Tokyo Electric Power Company (Tepco) to immediately notify the government of a technical emergency situation, which allows officials to take additional precautionary measures.

For many hours the primary focus of work at the site was to connect enough portable power modules to fully replace the diesels and enable the full operation of cooling systems.

Pressure and releases

Without enough power for cooling systems, decay heat from the reactor cores of units 1, 2 and 3 has gradually reduced coolant water levels through evaporation. The consequent increase in pressure in the coolant circuit can be managed via pressure release valves. However, this leads to an increase in pressure within the reactor building containment. Tepco has said that the pressure within the containment of Fukushima Daiichi 1 has reached around 840 kPa, compared to reference levels of 400 kPa.

The company has decided to manage this “for those units that cannot confirm certain levels of water injection” by means of a controlled release of air and water vapour to the atmosphere. Because this water has been through the reactor core, this would inevitably mean a certain release of radiation. The IAEA said this would be filtered to retain radiation within the containment. Tepco has confirmed it was in the process of relieving pressure at unit 1 while preparing to do the same for units 2 and 3.


Television cameras trained on the plant captured a dramatic explosion surrounding unit 1 at around 6pm. Amid a visible pressure release and a cloud of dust it was not possible to immediately know the extent of any damage. Later television shots showed a naked steel frame remaining at the top of the reactor building. The external building structure does not act as the containment, which is an airtight engineered boundary within.

Chief cabinet secretary Yukio Edano appeared on television to clarify that the explosion had damaged the walls and roof of the reactor building but had not compromised the containment.

Monitoring of Fukushima Daiichi 1 had previously shown an increase in radiation levels detected emerging from the plant via routes such as the exhaust stack and the discharge canal. Tepco have said that the amount of radioactive material such as iodine it is detecting have been increasing. The amount of radiation at the site boundary now exceeds a regulatory limit triggering another set of emergency precautions. It also meant the incident has been rated at Level 4 on the International Nuclear Event Scale (INES) – an ‘accident with local consequences’.

To protect the public from potential health effects of radioactive isotopes of iodine that could potentially be released, authorities are preparing to distribute tablets of non-radioactive potassium-iodide. This is quickly taken up by the body and its presence prevents the take-up of iodine should people be exposed to it.

Over the last several hours evacuation orders for local residents have been incrementally increased and now cover people living within 20 kilometres of the power plant.

Seawater injection

The injection of seawater into the building started at 8.20pm and this is planned to be followed by addition of boric acid, which is used to inhibit nuclear reactions. Tepco had to put the operation on hold for a time when another tsunami was predicted, but work recommenced after the all-clear.

Raised temperatures

Meanwhile at adjacent Fukushima Daini, where four reactors have been shut down safely since the earthquake hit, Tepco has notified government of another emergency status.

Unit 1’s reactor core isolation cooling system had been operating normally, and this was later supplemented by a separate make-up water condensate system. However, the latter was lost at 5.32am local time when its suppression chamber reached 100ºC. This led Tepco to notify government of another technical emergency situation.

Tepco has announced it has decided to prepare for controlled releases to ease pressure in the containments of all four units at Fukushima Daini.

A three kilometre evacuation is in progress, with residents in a zone out to ten kilometres given notice of potential expansion.


A seriously injured worker was trapped within Fukushima Daiichi unit 1 in the crane operating console of the exhaust stack and is now confirmed to have died. Four workers were injured by the explosion at the same reactor and have been taken to hospital. A contractor was found unconscious and taken to hospital.

Two workers of a ‘cooperative firm’ were injured, said Tepco; one with a broken bone.

At Fukushima Daiini unit 3 one worker received a radiation dose of 106 mSv. This is comparable to levels deemed acceptable in emergency situations by some national nuclear safety regulators.

The whereabout of two Tepco workers remains unknown.

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.

678 replies on “Discussion Thread – Japanese nuclear reactors and the 11 March 2011 earthquake”

Can someone please explain how the seawater is being injected? IANAE (I am not an engineer.) So pretend I’m a teenager …

I understand that a closed vent is preventing the process, but what IS the process? If there is no power, how is the water being injected?


Buckeye, look earlier in this long thread for pictures and sketches; there are quite a few pipes going into various parts of the reactor containment, and diesel pumps are being used. It’s not clear what particular pipes and valves are used or not used or failed, from what I’ve read.

(Japan Broadcasting Corporation)
updated at 13:40 UTC, Mar. 14

The utility firm said on Monday afternoon that fuel rods are exposed at the Number Two reactor of its Fukushima Number One plant after the level of coolant water dropped. At around 6:20pm, the power company began pumping in seawater.

Tokyo Electric says it had to halt the process due to fuel loss for the pumping system, possibly leaving the fuel rods in the reactor exposed. The firm says a core meltdown might have occurred.

The Nuclear and Industrial Safety Agency says that pumping seawater into the reactor is working now.

Earlier in the day, the firm told the government that the reactor had lost all cooling capability due to a failure of the emergency power system.

Since then, the company has tried to circulate the coolant by steam instead of electricity. But attempts to lower the temperature inside the reactor chamber have not worked well.

The company is also considering opening a hole in the reactor housing building to release hydrogen generated by the exposed fuel rods.

Accumulated hydrogen has caused blasts at two other reactors at the plant.

Monday, March 14, 2011 20:36 +0900 (JST)


“TEPCO says the water-drenched equipment and machinery short-circuited after the power plants were submerged in sea water on Friday.
Based on the government’s guidelines, the Fukushima No. 1 plant was designed to withstand tsunami waves of up to 5.7 meters and the No. 2 plant, up to 5.2 meters.

TEPCO says the tsunami waves that hit the plants were higher than 10 meters.

Monday, March 14, 2011 09:53 +0900 (JST)”


Could be a silly question here guys, so hold on…

Saw on the news last night footage from inside a reactor. It’s the news, so obviously they didn’t mention where it was.

This footage showed a ‘pool’ in a builbing, and something that looked like a reactor core at the bottom. Sort of hexagonal honeycomb of rods and things.

So, I’m just trying to marry up this image to how the plant works. The rods get hot and make steam. Is this bath the heat exchanger that provides steam, or the cooling water around the core? Is only the reactor pressurized?

Barry, have you done a ‘Nuclear plants for dummies, that know a little bit already’ post?



Hank, thank you. I did try to review those diagrams before asking. I see the descriptions and locations labeled where the seawater is being pumped in.

My question is about the basic physics of getting the water in. Is the water being pulled down into the containment via gravity, forced in by high pressure, or …? Please excuse my ignorance. (IANAE)


Hank, injection of fire water or sea water is standard protocol for accident mangement. What is really critical is did it get in… and what are the current radiation levels….

As you said there are many ways to inject if pressure is low enough, some more efficient than others… I hope you understand what you are reading on the internet as it must be filtered….


I’m not an engineer, just reading. From the quotes above, they do have some electric power and fuel, not enough fuel sometimes, to run ordinary electric or diesel pumps that they have been using.

I don’t know what “the company has tried to circulate the coolant by steam instead of electricity” means.

All the reporters are saying it’s hard to get reliable information. A lot of this won’t get clear until the crisis is over.



thanks to em1ss and please, critique and comment and point to better sources as much as you can. You’re among the very few commenters who actually know what they’re talking about here.

(I’m not, I’m just trying to filter what I read not to add opinion nor link to anything that doesn’t cite sources; it’s getting harder to sort out sense from crap as this goes on, tho’–I’m hoping we see some known reliable commenters take on a full time feed, but until the companies and government supply facts, that’s not likely).

Loss of coolant at Fukushima Daiichi 2
14 March 2011 FIRST PUBLISHED: 6.14pm
UPDATE 1: 8.04pm Information from Tepco television appearance

“A spokesman for Tokyo Electric Power Company has appeard on national broadcaster NHK to explain the company’s efforts to control unit 2’s reactor core after its isolation cooling system failed following an increase in containment pressure to some 700 kPa.

The company prepared to inject seawater into the reactor system, but this was only started “after the water level reached the top of the fuel.” Guages indicated that water levels continued to drop despite the injection process and after some time injection became impossible due to high pressure.

Opening the relief valve made injection possible again, but after a time pressure relief was again required. Injection has continued since that second venting operation but guages still do not indicate that water levels are rising.

The Japan Atomic Industry Forum reported back statements from the Nuclear and Industrial Safety Agency (NISA) saying that Tepco made a notification at 8.50pm that some fuel rods were presumed broken, based on radiation detected.”


evcricket, that sounds like a open-pool research reactor. While they generate some heat of course, it’s low quantities and there is no attempt to use the heat for power generation.

A power reactor is in an enclosed pressure vessel; the coolant carries the heat to turbines (possibly via heat exchangers).


I ask again, what are the radiation levels currently…. This is protocol response and may be working, but radiation levels determine effectiveness…

Some fuel rod leakage or fuel damage should be expected if as reported the fuel was uncovered for the reported amount of time. Key now for reactor 2 is covering the fuel and maintaining containment through flooding.


“Tuesday, March 15, 2011
…No. 2 reactor at the quake-hit Fukushima No. 1 nuclear power plant, as fuel rods became fully exposed again after workers recovered water levels to cover half of them in a bid to prevent overheating.

The plant operator, Tokyo Electric Power Co., said steam vents of the pressure container of the reactor that houses the rods were closed probably due to the battery problem, raising fears that its core will melt at a faster pace.

The firm said it will first lower the pressure of the reactor by releasing radioactive steam and open the vents with new batteries to resume the operation to inject seawater to cool down the reactor.

Earlier, cooling functions of the reactor failed, causing water levels to sharply fall and fully exposing the fuel rods for about 140 minutes. TEPCO said they could not pour water into the reactor soon as it took time for workers to release steam from the reactor to lower its pressure, the government’s nuclear safety agency said.

As TEPCO began pouring coolant water into the reactor, water levels went up at one point to cover more than half of the rods that measure about 4 meters.

Prior to the second full exposure of the rods around 11 p.m. Monday, radiation was detected at 9:37 p.m. at a level twice the maximum seen so far— 3,130 micro sievert per hour — near the main gate of the No. 1 plant, according to TEPCO.”


Tuesday, March 15, 2011

Reactor fuel rods fully exposed
Coolant failure now reported in No. 2 unit

Staff writer

The radioactive fuel rods at the No. 2 reactor of the Fukushima No. 1 power station were fully exposed at one point Monday, Tokyo Electric Power Co. said, raising the possibility that it suffered a partial core meltdown.

The utility operating the Fukushima plant later said the level of coolant water in the reactor’s container was raised 2 meters above the base of the rods — which are about 4 meters long.

However, it was not clear if Tepco was able to pump enough coolant into the containment vessel to cool it off. Nevertheless, Chief Cabinet Secretary Yukio Edano told a news conference Monday evening that the situation stabilized after cooling resumed.

Fears of the worst-case scenario — a total core meltdown — are increasing because the No. 2 reactor’s self-cooling system failed and sea water was being pumped in from outside.

Tepco said the water levels fell because the pump temporarily ran out of fuel and workers failed to notice it quickly enough.

It was not immediately clear how long the reactor’s core lay fully exposed or to what extent it heated up in that time….”


according to the http://www.nisa.meti.go. site’s latest press release:

→29.8 micro Sv/h(14:14 March 14)
MP5 (Monitoring at north-west Site Boundary for Unit 2)
6.1 micro Sv/h(14:02 March 14)
MP6 (Monitoring at the west –southwest Site Boundary for Unit 2)
3.70 micro Sv/h(16:10 March 14)
→4.2 micro Sv/h(12:34 March 14)
MP7 (Monitoring at the west –southwest Site Boundary for Unit 2)
6.1 micro Sv/h (12:16, March 14)
(3) Wind direction/wind speed (as of 14:14, March 14) at MP-4
Wind direction: North North West
Wind Speed: 2.6 m/s

can someone interprete? is the wind blowing back into Japan?


Hank, circulation by steam is a two fold explaination. One is by steam driven pumps, injecting coolant which is ideal…

Second is by steam driven cooling by convection, less than ideal but workable under proper conditions…. This last method relies on wetting the fuel and allowing the steam to rise… removing heat and preventing fuel melt. That’s as simple as I can make it.


I hope the Japs are able to get enough pumping power on site to flood the boilers. Is there any chance that the condensers can be restarted so it wont have to ventilate everything to athmosphere?


Sadly, we digress into agendas. Forgetting the mental anguish those affected are feeling locally. It may seem that I analyaze the reports positively with regards to the nuclear events. But I hold alot of skepticism for the news reports too and filter them. I don’t trust the media any more than the skeptics here. I am concerned about reactor 2 right now, but withold judgement for now.

Show me the data on significant release rates or radiation level increases on site. Then I will say a major nuclear accident impacting the populous now or long term has occurred. I live in the factual world.

Factually the real horror at the moment is the natural phenomenon that has destroyed an unbeliebable amount of Japan and killed thousands of innocent people. Those that survived are struggling , shelter, food, and fresh water supplies are dwindling…. Never mind the loved ones they may have lost.


Cripes my spelling is horrible in that due to typing… analyze… unbelievable… need a proof reader it seems and sorry.


Hank, my bad it’s getting late.. 0.650mpa is 6.5 bar. Does not sound very much at all to me then, a couple of sentrifugal pumps would be able to deliver above that without any problem. But i have only worked with oil boilers, never nuclear so there’s probably more to it than i know.

So 65 bar is normal operating pressure? Then it sounds to me that its some leeway still, as the denser steam also takes away more heat. but again i might be totally off.


Now what?
“Japan Earthquake: Third Reactor at Fukushima Nuclear Plant Explodes
Blast Came After IAEA Said Containment Vessels at Fukushima Nuclear Reactors Seem to Be Working
March 14, 2011
… a new explosion Tuesday morning at a reactor the Fukushima Daiichi nuclear plant, the Japanese nuclear safety agency reported.
The blast, which occurred at Unit 2, is the third at the plant since a powerful earthquake struck Japan on Friday….
The explosion, which occurred at 6:10 a.m., came shortly after the International Atomic Energy Agency had announced that the reactors at the Fukushima Daiichi plant had been shut down. ….”


New blast reported at damaged Japan nuclear plant

LOS ANGELES (MarketWatch) — Japanese media reported a new explosion heard at the No. 2 reactor of the earthquake-damaged Fukushima Daiichi nuclear power plant early Tuesday morning. Several reports cited government officials as confirming the blast at 6:10 a.m. local time (5:10 p.m. U.S. Eastern time). Officials with the Nuclear and Industrial Safety Agency said the incident may have damaged the reactor’s pressure-suppression system, according to the Kyodo news agency. The plant, operated by Tokyo Electric Power Co. /quotes/comstock/64e!9501 (JP:9501 1,621, 0.00, 0.00%) , has been the focus of widespread concern about a large-scale radiation leak.

Reportedly damaged the “pressure suppression system” shich apparently is the “inerted drywell (primary containment)” surrounding the reactor vessel proper and includes the “pressure suppression torus” at the base of the reactor.


“… Officials first became concerned about unit 2 at the plant after pressure began rising in the reactor. Officials from the Tokyo Electric Power Co. told NHK News that the explosion at unit 3 might have damaged unit 2’s cooling system.

“They’ve had trouble with getting the pumps working, with site power in general… They’ve shipped in extra diesel generators and they may have to do some extra retrofit plumbing,” Morse said.

… unit 3, which exploded early Monday morning in Japan, reportedly has a leak in its bottom.


The NYT is reporting radiation readings of 3130 microsievarts, which would be 313 REM, a very significant dose.


Thanks for catching that — it’s an order of magnitude error error, actually.

I’ve made some too. Let’s show our work or link to online calculators. We need sanity checks.

Sounds like it’s getting much worse at the site, if the “hole in the bottom” means the torus is leaking.

“normally you would just re-establish electricity supply, from the on-site diesel generator or a portable one.” Portable generators have been brought into Fukushima, he said.

Fukushima was designed by General Electric, as Oyster Creek was around the same time, and the two plants are similar. The problem, he said, was that the hookup is done through electric switching equipment that is in a basement room flooded by the tsunami, he said. “Even though you have generators on site, you have to get the water out of the basement,” he said.

Another nuclear engineer with long experience in reactors of this type, who now works for a government agency, was emphatic. “To completely stop venting, they’re going to have to put some sort of equipment back in service,” he said. He asked not to be named because his agency had not authorized him to speak.

The central problem arises from a series of failures…

Inside the plant, according to industry executives and American experts who received briefings over the weekend, there was deep concern that spent nuclear fuel that was kept in a “cooling pond” inside one of the plants had been exposed and begun letting off potentially deadly gamma radiation.

Then water levels inside the reactor cores began to fall. While estimates vary, several officials and industry experts said Sunday that the top four to nine feet of the nuclear fuel in the core and control rods appear to have been exposed to the air — a condition that that can quickly lead to melting, and ultimately to full meltdown.

At 8 p.m., just as Americans were waking up to news of the earthquake, the government declared an emergency, contradicting its earlier reassurances that there were no major problems. But the chief cabinet secretary, Yukio Edano, stressed that there had been no radiation leak.

But one was coming: Workers inside the reactors saw that levels of coolant water were dropping. They did not know how severely. “The gauges that measure the water level don’t appear to be giving accurate readings,” one American official said.

What the workers knew by Saturday morning was that cooling systems at a nearby power plant, Fukushima Daini, were also starting to fail, for many of the same reasons. And the pressure in the No. 1 reactor at Fukushima Daiichi was rising so fast that engineers knew they would have to relieve it by letting steam escape.

Shortly before 4 p.m., camera crews near the Daiichi plant captured what appears to have been an explosion at the No. 1 reactor — apparently caused by a buildup of hydrogen. It was dramatic television but not especially dangerous — except to the workers injured by the force of the blast.

The explosion was in the outer container, leaving the main reactor vessel unharmed, according to Tokyo Electric’s reports to the International Atomic Energy Agency. (The walls of the outer building blew apart, as they are designed to do, rather than allow a buildup of pressure that could damage the reactor vessel.)

But the dramatic blast was also a warning sign of what could happen inside the reactor vessel if the core was not cooled. The International Atomic Energy Agency said that “as a countermeasure to limit damage to the reactor core,” Tokyo Electric proposed injecting seawater mixed with boron — which can choke off a nuclear reaction — and it began to do that at 10:20 p.m. Saturday.

It was a desperation move: The corrosive seawater will essentially disable the 40-year-old plant; the decision to flood the core amounted to a decision to abandon the facility. But even that operation has not been easy.

To pump in the water, the Japanese have apparently tried used firefighting equipment — hardly the usual procedure. But forcing the seawater inside the containment vessel has been difficult because the pressure in the vessel has become so great.

One American official likened the process to “trying to pour water into an inflated balloon,” and said that on Sunday it was “not clear how much water they are getting in, or whether they are covering the cores.”

The problem was compounded because gauges in the reactor seemed to have been damaged in the earthquake or tsunami, making it impossible to know just how much water is in the core.

And workers at the pumping operation are presumed to be exposed to radiation; several workers, according to Japanese reports, have been treated for radiation poisoning. It is not clear how severe their exposure was….”


Can’t vouch for this but it’s interesting and seems credible thinking, doesn’t have any news in it:

“… my father works at a nuclear power plant. It’s in southern Georgia …. and is technically a project manager for the plant, not actually a nuclear engineer. Now, obviously, the power plant explosion in Japan is high on the topics of conversation around his workplace. Since he knows that I think his work is really cool and I like hearing about things, he forwarded me and all of his colleagues an email with two highly informative updates on what exactly happened at Fukushima-Daiichi. I’m sure some of y’all already know what’s going on, since y’all are more proactive in looking up what’s going on in the world than me, but if you’re interested in a long, informative update from people in the business, I’m copying it in here ….”

[excerpts from that (it was prematurely hopeful, written before the 3rd explosion and report of a leak below unit 2, however)-hr]

“There still is no heat rejection from the pressure suppression pools at any of the reactors so temperatures and pressures are rising and venting is needed. The tsunami destroyed the service water cooling systems. TEPCO is working hard to set up temporary RHR heat exchangers to cool the pools before they get too hot or the seawater levels in the basement areas rise to unacceptable levels.

At Units 1 and 3, I have confirmed that borated seawater is being injected into the depressurized cores with high pressure fire engine pumps. Both Unit 1 and Unit 3 primary coolant systems are now depressurized at 35-50 psig. Core cooling is with the relatively cold injected borated seawater, but the flooded wet and dry wells are filling and this mode cannot be sustained indefinitely without overflows. So within the next day, TEPCO will need to get some decay heat removal temporary heat exchangers operating to cool the wet well, Then they can go into a stable recirculation mode. Once closed recirculation can be achieved the addition of new flooding seawater can be minimized. But water injection/recirculation will likely continue somewhat like this for weeks.

It is actually very similar to how we cooled down the damaged/melted Three Mile Island Unit 2 core using the TMI main coolant pumps and steam generators. Of course Fukushima is a BWR and different, but the principle is the same. At TMI this mode continued for several months while core heat decayed. So much of this is like reliving Three Mile Island all over again.

From various sources I have gathered more information on what actually happened. As often happens, early information can be incorrect, but I think these are correct.

It seems that all the reactors withstood the earthquake ground motion OK. We do not have a comparison of actual versus design basis accelerations, but even though the motion was probably over the design basis, most safety systems seemed to be functional until the tsunami hit. The tsunami was the big problem.

It seems that Fukushima design basis tsunami was 6.5 meters, but the actual tsunami was in the 7-8 meter range. These waves washed the diesel fuel system away, submerged the switchyard and destroyed most of the switchgear. This massive damage to the electrical system prevented rapid hookup of auxiliary diesel generators that were relatively quickly brought on site. So only the turbine driven battery controlled RCIC was available to inject water into the reactor vessel until AC power was restored to the HPCI.

There is no information about the Unit 1 spent fuel pool situation. By now I am sure that TEPCO has the ability to pump water into the pool to maintain water levels. A small fire hose is all that is needed. There is no information available on debris from the explosion or anything else in the pool that is now completely exposed to the environment. Unless heavy debris fell into the pool and damaged spent fuel, this is not a big issue as long as they can keep pool water levels stable, which they should. Given the radiological releases from the primary containment pressure venting, the spent fuel pool releases are negligible.

Neither is there any information on the spent fuel dry storage cask modules that are at the Fukushima site. The Fukushima Independent Spent Fuel Storage Facility (ISFSF) is in the back of the plant site away from the ocean, so it is hard to tell if it was flooded or not. I suspect that wave water got there, but if it did it was a comparatively nothing event since these are passive cans. I believe there is ~100MTU of spent fuel in their ISFSI. But just being there is an issue in itself. Technically it is better there than in the Unit 1 pool without a roof….”


We are now almost four days on from the time the earthquake hit (that would be 4.46pm AEST this afternoon, I believe). The reactors were scrammed at the time of the quake, and the daughter product heat output will have been dropping exponentially since then.

Does anyone know how long external cooling needs to be maintained? I thought I heard something of the order of a week. If so, we should by this time be a fair way along the decay curve for heat output.


This is a probably credible source, just judging by the authors’ bios at the site. It is not a reassuring piece, it has more numbers and details on the spent fuel pool and the dry cask storage than I’ve seen elsewhere — although still far more questions than answers.

Barry, if you have a chance, I recommend a look at this and wonder if you can cite or debunk any of it.


Midnight GMT … just watched a live press conference hosted by Tokyo Electric on NHK news.

They said that the explosion at Daiichi No 2 (6:14 am Yokyo time) appeared to eminate from “low in the structure”, that they thought the supression pool casing had been breached (accounting for failure to be able to maintain water level ?), that the fuel rods were currently dry, and that measured levels at the plant gates were currently 8217 micro Sv/hr !

All personell non-essential to the recovery operation had been evacuated.


can someone on this site please explain the current situation and what it means? there was an explosion in the 2nd unit’s pressure chamber? where the suppression pool is. the pressure significantly dropped and they measured 8217 uSv.

does this mean that the 2nd containment has failed?

below is a link to Japan’s nhk broadcast in english.


Back in the late 60’s early 70’s, the USS Barb SSN-596, a nuclear-powered fast attack submarine, was tied up to the pier in Pearl Harbor for about 11 months while it was outfitted with a new crew. Why? Because the whole crew was busted for dope, Captain on down – nuclear-powered and probably nuclear-armed too. During Nam a lot of nuclear-powered vessels were operated by sailors higher on drugs in the engine room/reactor plant than students on campus at UC Berkely. We only came close to uncovering our Rx core once as a result of emergency and casualty drills gone wrong. Send some old nuke dope-head BTs, MMs, ETs, ICs, and EMs, over to Fukushima. They’d get that place under control – no problem.


> NHK broadcast in English
6:14 AM blast heard near suppression pool of No. 2 reactor and pressure began to fall…. from 3 atmospheres to 1 atmosphere.

Operators not directly engaged in the effort to cool the [No.2] reactor … are being evacuated to safer locations after “blast in the area of the suppression pool — the equipment that coordinates activities ….”

A senior correspondent is interviewed:
“this problem may spread and may become worse. The release of contaminated water to the outside is a very serious situation …. this could be a worst scenario … we do need very accurate information …

The cooling system for the spent fuel pool may have failed on one of the reactors that lost its roof; and mentions as breaking news — Tokyo Electric reports new smoke rising from the No. 3 reactor at around 7am Tuesday.


captaindallas2 said:

“When teenage dopers can operate it, its design is pretty forgiving! Thanks for the real story! Old Guy designs rule!”

Actually most of the guys in engineering that were nukes already had several years of college under their belts. Some even had four-year degrees. There were only a few of us young kids out of high school, and we were at least 20 by the time we came aboard. There are plenty of other stories I could tell all day long. We lifted a primary water relief right next to the pier adjacent the putt-putt golf course in Subic Bay. Hundreds of gallons of raw coolant warmed up the water there a little bit, in more ways than one. How do I know that? I was on the shutoff relief watch with headphones, and had to shut it to stop the discharge. That never hit the press either. But the one that shook up the ELTs on board the most was after they found out that backleakage from the primary to the charging pump head tank had been going on for a long time before someone noticed that the level in the tank was increasing without having any additional water added to it. The ELTs used to make their tea from that 200 degree water. Good thing we never had any clad melts in our cores. They probably only had to worry about Co60 in their tea. Ha! If it wasn’t 451 counts above background on the RM3 frisker, it technically wasn’t contaminated. When our clothes were at 450, we just threw them in the dirty clothes bin and took a shower. Only had 1.8 REM lifetime dose by the time I was discharged. 42 years later, still living from the radiation – if you call this living. Ha!


More from NHK World TV, this is a government minister speaking.

“1, 2 and 3 reactors water injection operation is continuing and so far for all 3 reactors water injection is continuing smoothly…. next problem will how to maintain this cooling … and how to deal with … fire in No. 4 reactor. As of 10:22 am according to the monitoring … (millisievert rather than microsievert, now we are talking about levels that can impact the human health. … these are readings taken near the area where we believe the release of radioactive substances is happening …. from 6am the 800 staff that remained in the power plant, all but 50 who are directly involved in injecting water have been evacuated … the situation that I am reporting is of very high concern to all of you and I regret that we are reporting this but in preparing for this scenario we have asked you to evacuate from a 20km radius from the plant …. from the 20-30km radius are we are asking you to remain indoors, do not go outside but remain indoors, and … please keep the windows shut. Do not use ventilation equipment ….”

This is a government minister speaking.


Correcion, captdallas2: It’s wasn’t raw coolant, as the volume of water discharged was out of the pressurizer, so relatively stagnant. Plus, it was most likely less than 100 gallons, plus or minus, 50. But the ELTs still glow in the dark today. Just kidding. I think the high pH water gave them the runs. Ha!


The above is my typing while listening to the NHK TV live stream, as close as I can come.

Questions now being asked:

Q: … pressure vessels being damaged? …
A: … No. 1, 2, 3 … injecting water … please contact Tokyo Electric … pressure has also been stabilized … utmost effort to maintain this level ..

Q: … fire in the No. 4 reactor … more serious?
A: … No. 4 incident occurred earlier than the No. 2, that’s why I talked about No. 4 first.

Q: … No. 2 pressure container?
A: …I have a report … high probability the compression vessel was damaged.

Q: … fire … is an ordinary fire?
A: … just like other reactors the No. 4 reactor is emitting heat … the fire that we are seeing at No. 4 reactor is not the type of fire that ignite some hazardous materials but the operators are now working to extinguish the fire in the No. 4 reactor as well….

Q: … evacuation radius?
A: … final decision was made by the Prime Minister … now asking the people living in 30 km radius from the plant to stay indoors… considering the current level of radiation reading …


Q: radiation reading quite high?
A: [could be the No. 4 reactor fire/

Q: if the No. 4 fire continues what could happen?
A: … we are making every effort possible to extinguish the fire…. the spent fuel is not going to catch fire in a general sense, the fire is being caused in the building really but … we don’t want the temperature to go up, if heat is created it may also cause radioactive material to be released.

Q: any possibility … release due to this fire? …
A: … a certain … may be released, but I would like the Tokyo Electric Power Company to give the actual figures. The current high readings are we believe from the Reactor No. 4 fire ….


That was an interview with the Chief Cabinet Secretary
Radiation levels at 10:20am
30 millisieverts at No. 1
Around No. 3 400 millisieverts
Around No. 4 100 millisieverts
“much higher than microsieverts”


If I heard right the Japanese prime minister corrected himself from 400 micro Sv/hr to 400 milli Sv/hr measured between no 3 & 4 reactors !

Thats 40 REM …. think you’d rather want to limit your exposure to that !


Hi there, long time reader of the site but this is my first post.
I need some reassurance here, from what i’ve read no matter how bad things get we WON’T actually see a meltdown of Chernobyl status, is that correct?
Reason i need to know is i have vouched my new dirtbike against this happening to a bloke that is snowboarding in Japan at the moment as per here:
I have faith in Barry’s take on the situation, i’m just hoping i haven’t put too much faith in him.


> It seems
Premature — rumor is not helpful.
Wait and see. That’s all we can do.

> Rodeo
No, Chernobyl design uses carbon blocks — like high quality coal/charcoal — instead of water, between the fuel elements; all of that carbon burned, along with the fuel, in that situation.

It’s still plenty bad, but not bad in that way.

TEPCO interview at 7:37, guy in a white coat with big diagrams and a pointer. Translator speaking, my typing as I listen:

“965.5 microsieverts”
“the level continued to go up”
“as of 8:31 near the front gate, 8,231 microsievert”
“9:38 am in the building of the No. 4 reactor a fire broke out but shortly before that after the explosion at the No. 1 reactor they found some damage at the building of No. 4 and … maximum level at 8:35 am … leakage could be gas or liquid …

7:05am this morning … unit No. 3 the pool which had spent fuel because of the hydrogen explosion … this pool … to store the nuclear spent fuels … usually they circulate the water … there is no cooling function right now … there is some steam above the building … No. 3 … they do not know the reason or the correlation between the steam and the explosion ….

It goes on and on.


@Rodeo – You won’t see precisely the same type of problems as at Chernobyl, but it is beginning to approach the point where the impact will be as bad.

The fire in the reactor 4 looks like it might causing radiation leakage somehow (judging by the jump in radiation measurements). I don’t think anyone can say how bad that will get (if spent fuel is exposed somehow then it’ll be pretty bad).

The containment pool damage is pretty serious but probably won’t cause as much radiation to escape as broadly as at Chernobyl in itself.

The worst case scenario is that the containment pool integrity is lost, spent fuel is exposed in reactor 4 and and aftershock causes another tsunami. That could be a lot worse than Chernobyl. That’s kind of a sci-fi scenario, but at this point everything else has gone wrong – why not that too?

If you have a choice, I’d get out of that bet. You might win, but at this point it is more likely than not that you will be winning on a technicality.


Hi, I’m glad you like my nhk link. the fire in the reactor #4 has been put out. the 400mSv, I am wondering does this mean the area around the plant will become uninhabitable? what are the effects on crops and lifestock? this area is heavily agricultural in Japan


Seems like 4 – 5 unprotected hours “on site” would give you LD50 exposure (as likely to die as medium term survive) …

Also seems like the fire in No4 is from the open spent fuel pool, rods that can go critical if they’ve been rolled together by the quake. Not a good local scenario given that the wind has now turned in a SW Tokyo direction !

Chernobyl as has been explained a hundered times before was a live core explosion and ensuing fire in the graphite moderator, which unlike dissipating and condensing steam in water moderation was carried high into the atmosphere to circle the globe … not going to happen here.

Thing is that these GE BWRs don’t have core catchers as the control rod servos are in a room at the bottom underneath the reactor vessel, so you’re putting trust in primary concrete containment which in the case of No2 seems already to have cracked …


> home counter readings
Can you read Japanese and tell what he’s counting? Gamma, beta, alpha?

I’d say he’s showing he’s detecting a change, but a very minor one compared to the natural background.

Look at the counts per minute he’s showing (from a baseline of maybe 15 or so, eyeballing the picture, with an increase then a spike to around 80, then decreasing).

Then compare:

Click on the page link for Black Cat, the company that makes the device; look at the counts per minute the same device used to test fresh lint from a clothes dryer immediately after drying your clothes:

That chart starts at around 4000 and drops off over a 3-hour period to around 33 counts/minute.

You can find charts made using the same device during a jet aircraft flight, and see how much radiation you get by being above most of the thickest part of the atmosphere.

It’s useful information; don’t panic; make comparisons.


Thanks for the excellent information being posted.

I should state I am a firm believer in science and the ingenuity of man, and that given our deep understanding of nuclear physics and materials that safe nuclear generation is totally feasible in principle.

The reason I am posting now is to follow up on my previous post where I raised concerns about the lack of, yet essential need for, a healthy respect for the dangers of nuclear power that was absent in these discussions. The accidents that have, and continue to impact, fukushima are I claim evidence of such a lack of a healthy fear (dare I say complacency) in the designers and operators of that plant.

It might be interesting for readers to know that strowger telephone

exchanges circa 1950s to 1980s also had a generator and battery backup for mains failure but that those battery lifetimes were well in excess of those for this nuclear power plant!

The diesel generators in this plant were exposed to tsunami water damage which amazes me in a plant located by the sea. I think we have been extremely lucky that the batteries were not also immediately damaged, especially when in many such back-up systems the generator and batteries are often in close proximity. Whether immediate shutdown could have occurred without batteries is not clear to me but one hopes gravity was properly employed.

There was then no external way to mechanically or electrically spin the fans to vent hydrogen from the containment building alllowing inevitable build up after venting which itself might be considered to be likely, or otherwise very possible, on a mains electrical failure.

We then have a vented hydrogen explosion in one building which was in range of the critical systems for another reactor, leading to a deck of cards scenario.

I won’t go on but this just all smacks of incredible design complacency, especially for a reactor by the sea in a major earthquake zone (given existance proofs from Indian ocean tsunami and chillian quake). And the Japanese where cited as being the safety experts earlier in this thread, and by the media commentators. Very concerning.

Now I have read and heard many times during this incident how this all has nothing to do with Chernobyl, nothing to do with the new designs on the drawing boards or those being installed. Well I beg to differ. The common elements are people, companies, profit, and politics. The science is rarely the issue in this area in my book…its just what else goes into the design, engineering and construction.

In the good old days, nuclear scientists worked for governments and the experts represented the people. Universities were funded by the people so controlled the debate and research agenda, and open and informed dissent could flow leading to open solid design evolution, operations and review.

The world is now very different. We have major companies sponsoring and directing the research agenda and pressuring governments towards another nuclear future. We have commercial based designs and operations for whom profit is the sole aim. We have company group dynamics, the pressures to succeed, meet expectations and unlock bonuses, as well as to save face. In parallel, we have a very real and hard cost/benefit competition with fossil fuels and other alternative energies.

I do not believe for a second that there is enough focus on safety in the industry, nor enough of a margin over other competing fuels to consider, justify and afford the investment in all necessary safety measures. The industry, just like all other industries, will do the minimum required by regulators to meet hurdles, and get through the remaining forums of open debate, to get the contract signed and the bottom line enhanced.

In my mind, Nuclear power is not safe now, nor in the near future, because of that current academic and commercial environment.

A few here commented how earlier this week how brilliantly the fukushima plants were doing given that they were never designed to withstand that size of an earthquake or tsunami. That to me says it all. We don’t care about flawed design requirements..we care about our health and that of our kids and our environment, and need the nuclear industry to behave, to engender trust and build for our design requirements, for the worst case, and not those requirements that enable big profits in the face of competition from fossil fuel and other alternatives.

I hope things get better because we all need a better option that coal!


///Now I have read and heard many times during this incident how this all has nothing to do with Chernobyl, nothing to do with the new designs on the drawing boards or those being installed. Well I beg to differ. The common elements are people, companies, profit, and politics. The science is rarely the issue in this area in my book…its just what else goes into the design, engineering and construction.////
You mean like ‘Neutron Leak’ in today’s fuel rods? The fuel rods get too hot, they expand. Neutrons leak out, shutting down the reaction and cooling down the core — even if Homer Simpson is asleep.


Why do nuclear plants depend on external power after a SCRAM? Couldn’t the energy generated by decay heat power a small generator to maintain coolant flow?


@ Righto….congratulations on being one of the first to jump in AFTER it appears that the shit has hit the fan, to denounce our most viable future energy source.
What is the option that YOU would promote to secure our base load power requirements?


I just wanted to throw in a bit of support for Barry who is a fellow Adeladian.

He has done an awful lot of work to provide this site, the threads and the good background and theoretical information for us all. He is an academic and is entitled to his opinions and his findings, and from what I have seen he is open and thorough in his academic processes. He clearly has a personal agenda from his very public pro-nuclear position, and these public academic positions are always capable of coming back and biting you in the bum.

At the end of the day, the guy works passionately to try to find ways to mitigate the growing effects of climate change – a noble cause for sure.

In all matters, academic theorising and positioning has to be married appropriately with solid scientific and engineering experience, a healthy respect for the unexpected in volatile situations, and practical savy of the dark worlds of industry and commerce.

But I personally thank him and his nuclear colleagues for the excellent work that has been done here to make us informed on the design of this reactor and its theoretical behaviours and limits.

I think we all have learnt much from this, will continue to learn and will hopefully come out of this with a better and more balanced views, and a healthier respect for nuclear risks, our reasonable fears and associated design requirements.


Vampires is derogatory? How quaint. What do you call the press reporting how to mitigate LD 50/30 precautions for the population around the affected power plant. I thought Vampire was a little understated compared to what I was thinking. My my my, people were less precious when I haunted Adelaide.


> addinall
Bogus claim about the BBC page; read the actual page; they’re giving standard advice, the same advice being given at the time on Japanese television for people inside the 30km radius, and consistent with the reported readings.

If you thought they were trying to scare you, you don’t understand the problem and if you advise people to ignore the directions you’re part of the problem. Please think harder and cite sources–then quote correctly rather than parodying them.

At 8 p.m. EDT March 15, a dose rate of 1,190 millirem per hour was observed. Six hours later, the dose rate was 60 millirem per hour, IAEA said.

About 150 residents near the Fukushima Daiichi site have been checked for radiation and 23 have been decontaminated.”

At the peak, it was a great concern; we’re fortunate that the peak was a short term high rate.



Why do nuclear plants depend on external power after a SCRAM? Couldn’t the energy generated by decay heat power a small generator to maintain coolant flow?

I believe that is what drove the coolant for eight hours after the tsunami – auxiliary pumps driven by the steam pressure from that decay heat process. But they need control power (from batteries in this case) and that’s what failed at that point. (Corrections welcome.)


I’d also like to laud the effort by the creator and moderator (Barry?) of this site, and those who’ve contributed to my understanding here. I truly appreciate the deletion of any drift into acrimony, name calling. Bad manners suck.

Having worked in tech pubs and video production for an oil and gas turbomachinery mfg, I know how difficult it is to get good info, let alone communicate both the big pic and boundary conditions, why great machinery and the best engineering is still valid, in use and marketable, in spite of individual installations demonstrating ‘rapid unscheduled dissassembly’ potential.

So it turns out that MOX (a Plutonium fuel blend) was in use in a now-scrap legacy reactor #2 at Fuku Daiichi. And the H2 blast-demolished penthouse structures probably covered some large spent-fuel cooling pools that can’t be taken for granted after ‘the big one’. That’s just how it is. My prayers go to the engineering workers, regular folks whose families, if they survived, are in a major disaster zone.

Now it’s time for this nuclear skeptic to go surf under the twin domes at San Onofre (SONGS). Really. I’ll be looking at the seawall there, wondering where the diesels and gravity-feed emergency cooling water is kept. I’ll be back here later, listening to this amazing group effort to know something about unfolding events in Japan, and trying to keep my opinions to myself.

Thanks again, for this site.


First, thanks for the details on the reactor situation. As I learn more about it I got few questions and was hoping that some experts can share their thoughts on it. Thanks.

As of now, the primary containment system in Unit 2 seems damaged.
1) With fuel rods partially uncovered and heat/steam formation continuing, can the build-up pressure cause the primary containment violently destroy with the release of uranium fuel into the air or would the ventilation system prevent it 100%.
2) In full meltdown scenario, the fuel pellets end up on the concrete core-catcher. Zircaloy cladding disintegrates around 1200 C while uranium oxide melts at 2800 C. If all water evaporates, would those temperatures melt thru the concrete (whose components start melting below 1000 C? That would lead to environment contamination.
3) What magnitude aftershocks (>7 on Richter?) cause the damaged primary containment disintegrate and result in fuel getting into the ground? I assume it would not go into the atmosphere as the reactor is underground.

4) The spent fuel problems in Unit 4: is it kept in a similar cement primary containment system under water? If it becomes exposed and heats up, its low radiation level would not allow a breach and environment contamination, true?

Thanks again


Is there any source on the web which monitors the actual radiation level around Fukushima in different distances?

Best wishes to this excellent web site!


Re the fire, apparently re-igniting today, in the #4 spent rod repository:

What component of the mix is likely to conflagrate first?

Any information on what might be going on there, besides a failure to keep a minimum cooling flow of H2O going?


the cooling pools that the spent fuel rods are stored in are open at the top. It is very likely (though I do not know for certain) that these cooling pools lost a great portion of their cooling water during the initial earthquake. This would be similar to videos from Japan showing swimming pools “sloshing about”…..


02:00 GMT – Japanese secretary of state holds a press conference to confirm that the “white smoke” billowing from the Daiichi plant for the past two hours is indeed from No 3 reactor and most likely is steam escaping through another primary containment breach.

We know that No 2 which looks “relatively intact” has a breached suppression well, but that never emitted smoke / steam like No 3 is now doing. Also its not clear if any water is currently being pumped into No 3 as it seems most workers have evacuated.

Also the minister said that although the fire in No 4 is seemingly out, despite the best part of a day they have not yet pumped any control coolant into the spent fuel pool which they believe to be at critically low level … that they have not been able to go near it because of the radiation levels !

Maybe I misheard but I thought a figure of 1000 milli Sev / hr was mentioned … but I’m now hearing that evacuation was caused by 6.8 mSv.

I’m a novice as regards the physics involved but could a meltdown of fuel create enough critical mass to restart sustained fission, or do you need moderators to be present to convert the fast neutrons to thermal neutrons ? Is fuel with a mix of heavier uranium isotopes or reprocessed MOX more susceptible to criticality without the requirement for neutron slowing ?

Also I’ve seen pictures on Japanese TV of how closely the spent fuel assemblies are stacked in the pool, almost reactor density, so again if the boric acid control depletes what happens ?

As a deep water oil production controls engineer our big enemy is water ingress at unimaginable pressures, and so its ironic that these problems all seem to stem from the tsunami causing just a few bar temporary but destructive flooding of the controls electronics and switching relays … surely IP66 or 67 should have been mandatory in that region ?

Not a failure of the structure or the hydraulics but as simple as electrics and water dont mix !


News rpt says they pulled 50 workers due to high levels of radiation. NYT stated that these were technicians at the plant. Does anyone know if firefighters are still trying to put out the blaze and are not counted as the 50 pulled from the site? Without anything being done, wouldn’t radiation levels keep increasing over time? Have they given’t up the fight by pulling remaining workers out?


Seems like the issue with the cooling pools in reactor 4 have more to do with the backup generators going down than it does with an earthquake.

I mean if the earthquake had caused that much water loss, then the radiation levels measured would gone sky high the day of not yesterday.


News rpt says they pulled 50 workers due to high levels of radiation. NYT stated that these were technicians at the plant. Does anyone know if firefighters are still trying to put out the blaze and are not counted as the 50 pulled from the site?

They’ve withdrawn … we’ll see what’s happening tomorrow.

Seems like the issue with the cooling pools in reactor 4 have more to do with the backup generators going down than it does with an earthquake.

Systems engineering is the issue … but why don’t you think the generators going down had nothing to do with the earthquake or tsunamis?

This ain’t a coincidence, sheesh!

The reality is that the earthquake and tsunami combined to fubar everything. To dismiss the importance of the earthquake and *inevitable tsunami (a Japanese word)” is idiocy.



“Cy the techs are pulled when levels get to high but once they go down they’ll go back in.”

Oh, yeah, it’s so normal like … this is the first time *all* workers have been withdrawn.

And I very much doubt that Nikkei is as advertised …


From the press conference today

At 10:00 am the levels measured at the front gate rose to 800 microsv

It peaked at 10:45 when it was at 6000 microsv

The last reading at 11:00 am japan time was
3000 micosv


Another rpt: Japanese officials talking to US military about possible help. Anyone know what can be expected from the US military that the Japanese have not been doing?


dhozga please stop acting like a child, it’s really not the time for it. This is a pretty serious matter and your immaturity really does no one good.

By the way, I was responding to a previous poster. If the earthquake had really caused the water loss in the pool at reactor 4 the radiation levels would have gone sky high that day.

The issue here is the same as the issues with the other reactors. It’s the lack of power to keep the pool cool. If it’s not not kept cool, the water temperature rises and water level goes down due to evaporation.

This was because of a 10meter tall Tsunami flooding the diesel generators cutting the power. That’s quite a bit different from saying that there was a loss of water because of the earthquake shaking which was what an earlier poster wrote.

Also the techs being removed when levels become too high has happened today and yesterday as well. Once levels decrease they are let back in.


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