Hot News Nuclear

Fukushima nuclear accident: Saturday 19 March summary

Last Saturday the the crisis level at the Fukushima Daiichi nuclear power station was rapidly on the rise. Hydrogen explosions, cracks in the wetwell torus and fires in a shutdown unit’s building — it seemed the sequence of new problems would never end. A week later, the situation remains troubling, but, over the last few days, it has not got any worse. Indeed, one could make a reasonable argument that it’s actually got better.

Yes, the IAEA has now formally listed the overall accident at an INES level 5 (see here for a description of the scales), up from the original estimate of 4. This is right and proper — but it doesn’t mean the situation has escalated further, as some have inferred. Here is a summary of the main site activities for today, followed by the latest JAIF and FEPC reports. You also might be interested in the following site map:

Another large cohort of 100 Tokyo fire fighters joined the spraying operation to cool down the reactors and keep the water in the spent fuel ponds. The ‘Hyper Rescue’ team have set up a special vehicle for firing a water cannon from 22 m high (in combination with a super pump truck), and today have been targeting the SNF pond in unit 3. About 60 tons of sea water successfully penetrated the building in the vicinity of the pool, at a flow rate of 3,000 litres per minute. Spraying with standard unmanned vehicles was also undertaken for 7 hours into other parts of the the unit 3 building (delivering more than 1,200 tons), to keep the general containment area cool. The temperature around the fuel rods is now reported by TEPCO (via NHK news) to be below 100C.

Conditions in unit 3 are stabilising but will need attention for many days to come. Promisingly, TEPCO has now connected AC cables to the unit 1 and 2 reactor buildings, with hopes that powered systems can be restored to these building by as early as tomorrow (including, it is hoped, the AC core cooling systems), once various safety and equipment condition checks are made.

Holes were made in the secondary containment buildings of Units 5 and 6 as a precautionary measure, to vent any hydrogen that might accumulate and so prevent explosions in these otherwise undamaged structures.  The residual heat removal system for these units has now been brought back on line and these pools maintain a tolerable steady temperature of 60C. More here. These buildings were operating on a single emergency diesel generator, but now have a second electricity supply via the external AC power cable.

Why are they concentrating on these activities? Let’s revisit a bit of the history of last week. The spent fuel pool still has decay heat (probably of the order of few MW in each pool) that requires active cooling. When power went out on Friday, the cooling stopped and the pool temperature has been rising slowly over the weekend, and probably started boiling off (and a large volume may have also been lost due to ‘sloshing’ during the seismic event). The pool is located on the 4th floor above the reactor vessel level. It remains unclear why they could not arrange fire trucks to deliver the sea water before the fuel rods got damaged and started releasing radioactivity. Now the effort is hampered by the high radiation level (primarily penetrating gamma rays). This is the inventory of those spent fuel ponds that have been causing so many headaches:

In order to remove the decay heat after the reactor shutdown, the cooling system should be operating. Following the loss of offsite power, the on-site diesel generators came on but the tsunami arrived an hour or so later and wiped out the diesel generators. Then the battery provided the power for 8 hours or so, during which time they brought in portable generators. However, the connectors were incompatible. As the steam pressure built up inside the pressure vessel, the relief valve was open and dumped the steam to the pressure suppression chamber, which in turn was filtered out to the confinement building and the hydrogen explosion took out the slabs.

The sea water was then pumped in by fire trucks and the reactor pressure vessels are now cooled down to near atmospheric pressure but the fuel assemblies are uncovered at the top quarter or third (the FEPC updates give the actual pressure and water levels). It appears that the pressure vessels and the reactor containment structures are intact, except the Unit 2, where the hydrogen explosion took place inside the containment and hence damaging the lower wetwell torus structure (but almost certainly not the reactor vessel, although the exact status is unclear). It appears that the radioactivity releases are mostly coming from the spent fuel storages than the reactor cores.

World Nuclear News has a really excellent extended article here entitled “Insight to Fukushima engineering challenges“. Read it! Further, you must watch this 8 minute reconstruction of the timeline of the accident done by NHK — brilliant, and really highlights the enormous stresses this poor station faced against a record-breaking force of nature. As I’d noted earlier, just about everything that could have went wrong, did. But valuable lessons must also be learned.

The IAEA and Japanese government has reported the potential contamination of food products from the local Fukushima area via radioactive iodine (mostly vented as part of the pressure relief operations of units 1 to 3). This is a short-term risk due to the 8-day half-life of radioactive iodine (and a small risk, given the trace amounts recorded), but precautions are warranted, as discussed here. What does this mean?

In the case of the milk samples, even if consumed for one year, the radiation dose would be equivalent to that a person would receive in a single CT scan. The levels found in the spinach were much lower, equivalent to one-fifth of a single CT scan.

… and to further put this in context:

The UK government’s chief independent scientific advisor has told the British Embassy in Tokyo that radiation fears from the stricken Fukushima nuclear power plant are a “sideshow” compared with the general devastation caused by the massive earthquake and tsunami that struck on 11 March. Speaking from London in a teleconference on 15 March to the embassy, chief scientific officer John Beddington said that the only people likely to receive doses of radiation that could damage their health are the on-site workers at the Fukushima Daiichi plant. He said that the general population outside of the 20 kilometre evacuation zone should not be concerned about contamination.

As to the possibility of a zirconium fire in the SNF ponds, this seems unlikely. Zr has a very high combustion point, as illustrated in video produced by UC Berkeley nuclear engineers. They applied a blowtorch to a zirconium rod and it did not catch on fire. The demonstration is shown about 50 seconds into this video. The temperature was said to reach 2000C [incidentally, I visited that lab last year!].

The the Japan Atomic Industrial Forum has provided their 12th reactor-by-reactor status update (16:00 March 19).

Here is the latest FEPC status report:


  • Radiation Levels
    • At 7:30PM on March 18, radiation level outside main office building (approximately 1,640 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 3,699 micro Sv/h.
    • Measurement results of ambient dose rate around Fukushima Nuclear Power Station at 4:00PM and 7:00PM on March 18 are shown in the attached two PDF files respectively.
    • At 1:00PM on March 18, MEXT decided to carry out thorough radiation monitoring nationwide.
    • For comparison, a human receives 2,400 micro Sv per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6,900 micro Sv per scan.
  • Fukushima Daiichi Unit 1 reactor
    • Since 10:30AM on March 14, the pressure within the primary containment vessel cannot be measured.
    • At 4:00PM on March 18, pressure inside the reactor core: 0.191MPa.
    • At 4:00PM on March 18, water level inside the reactor core: 1.7 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
    • Activities for connecting the commercial electricity grid are underway.
  • Fukushima Daiichi Unit 2 reactor
    • At 4:00PM on March 18, pressure inside the primary containment vessel: 0.139MPaabs.
    • At 4:00PM on March 18, pressure inside the reactor core: -0.002MPa.
    • At 4:00PM on March 18, water level inside the reactor core: 1.4 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
    • Activities for connecting the commercial electricity grid are underway.
  • Fukushima Daiichi Unit 3 reactor
    • At 2:00PM on March 18, six Self Defense emergency fire vehicles began to shoot water aimed at the spent fuel pool, until 2:38PM (39 tones of water in total).
    • At 2:42PM on March 18, TEPCO began to shoot water aimed at the spent fuel pool, until 2:45PM, by one US Army high pressure water cannon.
    • At 3:55PM on March 18, pressure inside the primary containment vessel: 0.160MPaabs.
    • At 3:55PM on March 18, pressure inside the reactor core: -0.016MPa.
    • At 3:55PM on March 18, water level inside the reactor core: 2.0 meters below the top of the fuel rods.
    • As of 3:00PM on March 18, the injection of seawater continues into the reactor core.
  • Fukushima Daiichi Unit 4 reactor
    • No official updates to the information in our March 18 update have been provided.
  • Fukushima Daiichi Unit 5 reactor
    • At 4:00PM on March 18, the temperature of the spent fuel pool was measured at 152.4 degrees Fahrenheit.
  • Fukushima Daiichi Unit 6 reactor
    • At 4:00PM on March 18, the temperature of the spent fuel pool was measured at 148.1 degrees Fahrenheit.
  • Fukushima Daiichi Common Spent Fuel Pool
    • At 10:00AM on March 18, it was confirmed that water level in the pool was secured.
  • Fukushima Daiichi Dry Cask Storage Building
    • At 10:00AM on March 18, it was confirmed that there was no damage by visual checking of external appearance.

At 5:50PM on March 18, Japanese Safety Authority (NISA: Nuclear and Industrial Safety Agency) announced provisional INES (International Nuclear and Radiological Event Scale) rating to the incidents due to the earthquake.

Fukushima Daiichi Unit 1, 2 and 3 Unit = 5 (Accident with wider consequences)

Fukushima Daiichi Unit 4 = 3 (Serious incident)

Fukushima Daini Unit 1, 2 and 4 Unit = 3 (Serious incident)

(No official provisional rating for Fukushima Daini Unit 3 has been provided.)


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.

344 replies on “Fukushima nuclear accident: Saturday 19 March summary”

Barry a quick correction,

the Tokyo Fire Department’s elite search and rescue team is called “Hyper Rescue.” They have special equipment and training to fight hazardous material fires as well as conduct rescue searches for tsunami and earth quake victims.

Here is an article on the from 2005:

Also a picture from of a Hyper Rescue team training:


“Chief Cabinet Secretary Yukio Edano said levels of radiation exceeding safety limits stipulated by Japanese law were found in some samples of spinach and milk from the Fukushima and Ibaraki prefectures but authorities said the radioactive iodine-contaminated food posed little risk.

Tainted milk was found 30 kilometers from the plant and spinach was collected as far as 100 kilometers (65 miles) to the south, almost half way to Tokyo.”



Weird, my original post didn’t show up. Anyways, Barry just a quick note.

The special vehicles don’t carry a title. Hyper Rescue is what the elite search and rescue teams from the Tokyo Fire Department are called.


Nikkei, I rescued your post from the spam queue – things with multiple links often get sent there automatically. Thanks for that info, I’ll update the post when not on my iPhone.

Ben, cover the hosting costs for me, so I only pay for yearly domain registrations etc. I prefer not to take any donations as I want people to always know that I undertake this work this because I think it is the right thing to do, not for any mercenary motivations (however small!)


“Samples of tap water taken yesterday in Tokyo and five nearby prefectures showed traces of radiation that were within acceptable levels, the Japanese government said.

Radiation was detected in water in Tokyo and the prefectures of Tochigi, Gunma, Saitama, Chiba and Niigata, Japan’s Ministry of Education, Culture, Sports, Science and Technology said today in a faxed statement.

Tochigi Prefecture’s reading of radioactive iodine-131 was 77 Becquerel per kilogram, the highest among the prefectures, while the level of iodine found in Tokyo’s Shinjuku district was 1.5. All the numbers were within the 300 Bq/kg limit, the ministry said. ”

So the level in Tochigi has reached 25% of the legal limit? Good thing the wind has been blowing out to see all week.



“Chief Cabinet Secretary Yukio Edano said levels of radiation exceeding safety limits stipulated by Japanese law were found in some samples of spinach and milk…”

Barry, any information on relative legal safety limits in various countries?
I believe that Japanese limits are among the strictest (lowest levels allowed) in the world, meaning much larger safety margins remain when “legal limits” are passed?


The fuel rods in the spent fuel pool are generating generating as much heat as a fluorescent light tube, about 120 watts for 3-4 meter rods so 30-40 watts per meter of rod. This really isn’t that much, and the sattelite images show clear vision into the fuel ponds, meaning they are open to ambient cooling. The rods are shaped like thermal radiators, a very efficient cooling mechanism.

In order for the steam-redux reaction to occur, over 900 degrees Celcius is required. If the top is open to ambient I’m having a hard time seeing how this could generate much hydrogen. Putting it in my thermo model with the relevant thermal conductivities and geometries I cannot get >900 degrees celcius from this, even with poor ventilation. The temperature readings are also well below boiling point of water and sattelite images show water in the ponds. So I’m still sceptical that a hydrogen explosion in the fuel ponds itself was the cause here. Theres lots of other stuff like motor pump oil that can support combustion quite well.

Does anyone has more info on this?


I’d be really interested to hear about the other nearby nuclear plants – Onagawa is far closer to the epicenter, I believe. Obviously there were no serious problems there (since there’s been no media circus!) but why not, what problems did they have, does this tell us anything about design features, age, etc?

(I realise that now perhaps there are more interesting things to think about, but if you get a moment.)

By the way, excellent site Barry, congratulations. I hope your hosting company isn’t charging you extra for all the traffic you’ve deservedly been getting in the last few days. I saw an earlier suggestion about a donate button, not such a bad idea methinks, especially if you post the site’s costs and income.


What’s the current situation in Japan on regards radiation leakage from the Fukushima Daiichi site?…

One source often quoted by news agencies is the frequent status (2-4x/day) updates by JAIF (Japan Atomic Industrial Forum) at and for very thorough coverage from a scientists POV with many references and much background s…


From an American certified health physicist without a nuclear power background, thank you Barry and other posters for your daily stream of credible information.


Would also like to express my appreciation for your work. This is the place I come to when I want to know what is going on over there.
Wonder how many hits you are getting. I think there is a lot of I told 5 people about your site and they each told 5 people and they in turn told 5 more people going on.


Barry, thank you for this update. It’s also very interesting to see the NHK timeline because it shows something that has been ignored by the media (in my country, the US)–and that is this: the safety features at Fukushima _worked_.

When the quake hit, the reactor was scrammed (I hope that’s the proper term), and the cooling system went into action. It was the effects of the tsunami that stopped the process.

Some here in the US have been claiming that the reactor designs were faulty and that the crisis was created by human error and greed. The NHK reconstruction blows those myths apart.

Thank you for your updates and for giving us information based on hard facts, not fear mongering.


So they have punched holes in the roofs of 5 & 6 to let hydrogen escape? Isn’t that the only contaiment for radioactive releases from the spent fuel pools?



There have been many discussions here to effect “Japan is known for Tsunamis… this is an expected event and should have been planned for..”.

IShortly after the Tsunami hit there were some suggestions from at least one scientist suggesting this was a once in a thousand year event, believed to be last duplicated in 869 A.D.:

If true (and I am not in a position to have an opinion) then all the criticisms of too low Tsunami barriers around the plant, etc., may be unrealistic. Taking once a millennium events into consideration in the engineering would then lead to other impossible scenarios such as a major volcanic event depositing meters of ash on the plant and all the surrounding infrastructure (such as the power grid). Or meteorite impacts, and on and on…

I too am impressed that, given the horrific natural events the plants are even in a condition that allows the operators to continue remediation efforts. Every day that the local radiation levels are such that even limited access is doable is a great day :-).

Much discussion here has been directed at the “zero tolerance” aspect of nuclear energy, resulting in things such as legal limits allegedly far, far below realistic levels of danger. In normal times that may be a good thing- err on the side of caution and little seems to be known as a fact regarding effects of low level radiation…

But these are not normal times for Japan. I hope babies in evacuation centers don’t go hungry while mildly tainted (and possibly perfectly safe) milk is
declared unfit. This is a trade-off of multiple and conflicting risks. Maybe. Although arguably the problem of feeding the evacuees may be more related to distribution problems than supply problems.


I understand the radiation levels are low here in the West Coast of CA, however I have 2 questions:
1 – what if the actual particals of cesium-137 and iodine are breathed or taken into the body? is this a 30 year dose?
2 – How does the rain affect levels? Is there any hope rainy weather will wash away our woes here and in Japan?


Regarding drinking water, here’s a link to the specific measurement figures in Tokyo:

(strange URL, but it worked for me)

And the WHO has a document, “WHO Guidelines for Drinking-water Quality (GDWQ)” which provides a reference point — section 9.3. PDF available at the WHO website.

I am a lay person, so I will omit my uneducated opinion and leave the rest for the experts…



I think the punching of holes in the roof was a precaution to prevent a explosion no matter how remote. They already have 3 severely damaged and one slightly damaged building from explosions. The spent fuel ponds in 5 & 6 now have temporary diesel power and may soon have outside power. Cooling is going on and these ponds never had any real containment. There may have been some filtering of air going out of the building, but if the spent fuel never heated up the amount of radioactive material being released is miniscule. With cooling there will not be a hydrogen explosion, but the situation is still dynamic and if they lose those diesel generators, there will be a problem, so cut a hole in the roof in case that happens. Unlikely, but we have seen lots of unlikely or unanticipated events.


Morgan, on 20 March 2011 at 3:07 AM said:

>>1 – what if the actual particals of cesium-137 and iodine are breathed or taken into the body?

The cesium will leave your body eventually in about 4 months, just as the radioactive potassium found in all bananas does.

Click to access Cesium.pdf

Iodine 131 has a half life of 8 days.


Barry, thank you so much for your outstanding information compilation effort. Please keep up the great job despite the insults and other personal attacks.

The French media are hysterical about this accident. It is great to read your daily post to balance their superficial and confusing reports.

From the ABC TV One Plus Interview, I understand you feel “ashamed” of mixing facts with opinions. Please don’t be ashamed! Opinions (and emotions) are what makes a difference between a great blog and a boring technical report.

Now one question: how can Cesium and Iodine be released in the atmosphere? Does this require a breach of the Zircalloy rods? or do those particles pass through the Zircalloy?


François, unless the clad on the spent fuel rods catches fire and produces smoke, which I think is highly implausible, then only way the Cs would disperse is via releases of volatile particulates that have accumulated over the years in the pond after being shed in minute quantities from the fuel rods. The I that remains will have virtually no radioactive isotopes.


“Meteorologists predict the wind direction will change today, taking dangerous emissions across Tokyo, 250 kilometres to the south.”

It will be very interesting, then, to look at the real-world data in Tokyo over the coming days.

The above is the dose rate in Tokyo, in uSv/h, updated regularly. The doses are absolutely negligible.

There is also a lot of very good data coming out of the KEK experimental physics centre in Tsukuba, just outside Tokyo.

Above is their real-time gamma dose monitor.

They also have some very high resolution gamma spectroscopy data, showing the levels of several different significant fission products.

These fission products are definitely from Fukushima, and they are there at detectable levels – but these instruments are incredibly sensitive, and these levels are absolutely harmless.

We’re talking about, for example, 2 nBq (yes, nanobecquerels) of Cs-137 per cubic centimeter of air at the moment.


Small detail that troubles me:

“Then the battery provided the power for 8 hours or so, during which time they brought in portable generators. However, the connectors were incompatible.”

I’m a truck-driver – not a scientist – but I restore antique electronics as a hobby. Incompatibility is what the hobby is all about, as one works to repair 70 year-old equipment. So… I keep wondering why incompatible plugs would stymie them. Can’t even big, fancy plugs be cut off and cable elements spliced together? Even allowing for several magnitudes of complexity beyond what I deal with, I still can’t see why some “snipping and twisting” couldn’t have been done.

(I realize I may be merely be demonstrating how ignorant of all this I am… but curious anyway))


Luke Weston

I believe the standard SI method of reporting would be to use Bq per cubic meter

So 2 millibecquerels per cubic meter or a decay of 1 atom every 500 secs in that volume of air. Indeed miniscule. They must be processing huge volumes of air to detect anything.


Morgan, levels are not merely low on the West Coast of CA, whether that’s California or Canada, they are completely and utterly negligible.

The essential thing to understand about radioactivity is that vanishingly low amounts can be detected. Many orders of magnitude lower than any possible health impact. So “X has been detected” is a statement that says absolutely nothing about health impact.

In the case of Fukushima, the low actual releases combined with the enormous distance across the Pacific mean that there is no chance – zero – that there will be any health impact on your coast.


François – My understanding is minor damage – much less than melting – of the zirconium cladding can release traces of caesium and iodine from the fuel rods into the coolant. If that coolant is vented, as happened at Fukushima, that would certainly be detectable, since ultra low levels of radioactivity are both detectable and identifiable.

Luke, I didn’t realise there was such a unit (of any use) as a nanobecquerel. That would be one atomic decay every billion seconds, ie. every 31 years.


Damen, I agree with you that I don’t think a little problem like “connectors” would have stopped an engineering crew desparate to feed power into a machine. However, voltage levels, max rated power or some other detail of generation characteristics could have. If the generators were simply too small to drive the pump, for example, that would do it.


Luke Weston

I wonder if you now agree that your assertion made in your

post, that they were not injecting seawater into “any part of the nuclear reactor or the Nuclear Steam Supply System itself. It is an injection of seawater into the containment structure surrounding the reactor pressure vessel” is incorrect? If so an amendment to that assertion is warranted, as it is still part of the main part of this website. Not everyone is going to read through all of these discussions. If you cannot insert a statement to that effect, I think Barry should do so.


Some may be interested (relieved?) to learn that on page A8 of today’s Washington Post is a one column article titled ‘Radiation risks low, according to science.’ How about that…one week later, 8 pages in, it was finally time to report something based on some real science! And the article did just that, dispelling a lot of the hysteria for the public. Better late than never, I suppose.


Thanks Joffan,

Exactly what I was wondering. I think your surmise about under-powering the pumps will turn out to be an approximation of the real problem. I know with my old equipment under-powering one part of a circuit (say, a resistor gone out of it’s original tolerances) can actually cause too much current flow in other parts (like output at the plate of a tube) and over-heating/burning. I bet under-powering those pumps is just as bad.



I note that the oil refinery fire at Cosmo Oil Co in Chiba, which started with the earthquake, is still burning as of this moment. It has been spewing tons of pollution into the air, no doubt the intense heat has been hampering efforts to put it out, and those downwind are in real danger of being effected should they breath the smoke.

Yet this event gets little coverage.


Cutting torch relies on the material being cut to begin oxidizing–this is what the Oxygen feed does.

I have a question about the wetwell torus thing. If the suppression pool is supposed to scrub steam discharge, then does the primary vessel vent into the “light bulb,” and steam conducts through those pipes and bubbles up inside the suppression pool water?
If so, that means the volume above the suppression pool is the low-pressure side. Does it vent to the atmosphere, and where?
Also, if the inside of the “light bulb” is an area that reactor steam would vent to, is it a place where one can enter and walk around, or is it forever off limits because of radiation from the core?


There must also be lots of natural gas pipeline and powerplant explosions. And coal plant fires maybe?

What about major oil terminals (storage)? Storing millions of liters of gasoline is dangerous even without a 9.0 Richter earthquake.

Wind turbines damaged? Killing anyone when falling over?

We hear virtually nothing about this.



Western Japan uses 60 Hz, while the eastern part uses 50 Hz. I heard the Fukushima systems use 50 Hz, but somehow the portable generators they brought in were the 60 Hz kind. I don’t know enough about electronics to say how hard it is to convert, but I’m as surprised as you that they weren’t able to jury rig something.


@Luke Weston:

Isn’t that demonstration ignoring the issue of the presence of water vapor? From “Safety and security of commercial spent nuclear fuel storage: public report” (National Academies Press, 2006)

The ability to remove decay heat from the spent fuel also would be reduced as the water level drops, especially when it drops below the tops of the fuel assemblies. This would cause temperatures in the fuel assemblies to rise, accelerating the oxidation of the zirconium alloy (zircaloy) cladding that encases the uranium oxide pellets. This oxidation reaction can occur in the presence of both air and steam and is strongly exothermic that is, the reaction releases large quantities of heat, which can further raise cladding temperatures. The steam reaction also generates large quantities of hydrogen….

[With a loss of coolant] These oxidation reactions can become locally self-sustaining … at high temperatures (i.e., about a factor of 10 higher than the boiling point of water) if a supply of oxygen and/or steam is available to sustain the reactions…. The result could be a runaway oxidation reaction referred to in this report as a zirconium cladding fire that proceeds as a burn front (e.g., as seen in a forest fire or a fireworks sparkler) along the axis of the fuel rod toward the source of oxidant (i.e., air or steam)….


“Holes were made in the secondary containment buildings of Units 5 and 6 as a precautionary measure, to vent any hydrogen that might accumulate and so prevent explosions in these otherwise undamaged structures.”

I’ve read comments to the effect that after Three Mile Island, the U.S. Nuclear Regulatory Commission required mandatory retrofit of “direct vent” devices to get accumulated hydrogen out of the reactor without risking explosions or overpressure from such accumulations.

(Even though at TMI, the “hydrogen bubble” risk inside the reactor turned out retroactively to have been negligible, due to inept calculations by NRC engineers.”

It appears that the Fukushima units lacked any such direct venting. So the operators vented free hydrogen from the reactors into the interior of the reactor buildings, where it explosively recombined with oxygen. And did the damage now easily visible in photographs.

I have also read comments which claim that the NRC require devices inside of the reactor vessel to attempt to mitigate hydrogen accumulation before having to vent it externally. There has been no mention of any such devices at Fukushima.

Is this a case in which Japanese regulatory authorities and utility management adopted a “not-invented-here” mindset and ignored nuclear best practices from abroad?

There is some precedent for this in an Asian cultural context. Back in the 1990s, the Korean airlines had an absolutely dismal safety record, racking up a string of serious accidents.

Outside audits revealed that those firms were culturally insular and nonstandardized in their practices, and failed to stress such key aviation safety principles as Crew Resource Management.

The Korean carriers listened to the auditors, and overhauled everything about how they trained, planned and flew. Their safety records are now comparable to other global airlines of similar size and reach.


On one of these threads you wanted citations for a poster alledging a 38m tsunami in the Medjii Earthquake. This is a paper I found.

Click to access HKpepi72c.pdf

It is such an outlier I do not see how it could rationally be used in criteria for design basis accidents though.


Hi everyone, sorry for intruding, and thanks for the marvellous work you’re doing with your blog.
I just have a question, related to the last comment from DV82XL (and the first tim I saw written an issue I thought about from the first day)

I saw many different places on fire just after the tsunami hit, as well as many tanks scattered about in the country after the withdrawal of the wave.
and also, from the NHK video, on the very front of Fukushima Daiichi one can see two huge tanks (several thousands mc, it looks) of presumed fuel for pumps, vanished after the wave.
My question is (i ask here because this is the more accurate and competent place I found to now): is there a measured assessment of the toxicity and radiation emission of fires from oil, gas and other flammable materials, and more there is a way to know the effects on the quality of exposed vegetables and water after five days of rain and snow who passed through several chemical product fires?

thanks to whom would answer, and a pray for all the dead and survived japanese


ah, sorry i was forgetting…
about the strange connection troubles of the emergency mobile equipment, I know that Japan has two big zones of electric power frequency, 60Hz in the west and south and 50 Hz in the east and north. hence the troubles also for providing power from the west region in the first days. it could have happened that the equipment had a different frequence ?


You need to get temperatures over 900 degrees Celcius for significant hydrogen redux reaction to occur. I’m not buying this at all for the spent fuel pond, as it is open at the top to ambient air. The fuel rods are shaped like radiators, basically very efficient space heating devices, and would convect loads of heat away. Remember that the heat per fuel rod per meter in 3 month old fuel is similar to a standard fluorescent tube office light. My thermo model doesn’t show anywhere near those temperatures would be reached, especially if part of the bottom of the fuel rods were still submerged in water. The sattelite images show a clear opening to the ponds.


> my thermo model
So either you’re wrong, or the industry is. Odds?

“In all American-designed reactors, spent fuel must be taken out of the top, but can never be exposed to the air. It must always remain under water.

How to do that? Flood the area over the reactor and move the fuel to a pool whose surface is at the top of the flooded area…..”


@ Stead: I will tell you what I know.

The lightbulb area is the drywell. It has steam pipes connecting the bottom of the light bulb to the torus, which is actually seperated by valves and might be called a secondary containment (the concrete superstructure might then be called ternary containment, but this is not common use).

Pressure relief valves vent the overpressure, with any hydrogen or volatile fission products that might be present under accident conditions such as at Fukushima Daiichi, via the steam pipes at the bottom to the torus. That is the wetwell, it has steam pipes ending under water so any steam that comes through will condense under water. This is quite effective as you can imagine, given the direct contact of water with steam. But this trick only works up until the normal atmospheric boiling point of water, after that it gets less effective and pressure also builds up. When that happens and you still have no active cooling, as was the case at Fukushima, you must relieve the pressure to a stack which has filters such as carbon filters or resin ion filters. This filters out any possible fission products that are not noble such as cesium, strontium and iodine. However it is of course not 100% efficient, a small fraction of those fission products are going through the filters, and that is why it is being detected in small quantities in the area and in agriproducts such as milk.

But this does vent the steam to the environment, relieving pressure. The steam that is used as coolant for some time has become activated and will quickly decay to stability, but of course this means a hard spike in radioactivity. Wait a few minutes and its gone.

People should not be going within the confines of the lightbulb. It is not good for your health. There is a biological axial shield around the reactor pressure vessel that should keep radiaton okay, but not a place you want to stay for long. Also if steam vents you are deader than a doornail.

Hope this helps. I was not too familiar with Mark I containment for BWRs, unfortunately I had to take a crash course over the last week, so some of my info may be incorrect.


Ian Lowe of the Australian Conservation Foundation, sticks it to the nuclear industry in The Age this morning. Obviously hadn’t been reading this site.


DV82XL said:

“I note that the oil refinery fire at Cosmo Oil Co in Chiba, which started with the earthquake, is still burning as of this moment. ”

Really! I’ve been wondering about that. I remember a report that it was still burning on Tuesday but then I read a single line article somewhere that claimed operations at Chiba had recommenced. This seemed very unlikely to me so if you have more info on the situation I’d appreciate the link.


a quote from that telegraph article I just linked to:

“One employee said TEPCO staff had attempted to jump start emergency cooling system using car batteries and small diesel generators after back up systems failed. “


By the way, if this was unclear, the Mark I design vents the overpressure to the top chamber where the crane is. This is done to make sure short lived radioactive material decays before entering the outside air, which is good practice in plants around the world. This is why there was a hydrogen explosion – there is normal air in that space and it does not take much to ignite hot hydrogen gas. Normally catalysts, called recombiners, would make the hydrogen bond with the oxygen to make water again. Unfortunately these require external power to work and this was not available. This is an important area to take lessons for older BWRs, I think. Make sure they have redundant battery power to work for a week.


@Marion Brook

“Researched by Industrial Info Resources (Sugar Land, Texas)–Cosmo Oil Company Limited’s (TYO:5007) (Tokyo) refinery in Ichihara, Chiba, remains offline due to a fire in the natural gas tank farm. The fire broke out following last Friday’s magnitude 9.0 earthquake. All units are currently offline and personnel remain unable to enter the complex due to the fire.

For details, view the entire article by subscribing to Industrial Info’s Premium Industry News


@Stead, on 20 March 2011 at 12:59 AM said:

“Looks like it washed away their diesel fuel tank farm”

That’s something I’ve been wondering about. Can anyone confirm that the tanks were above ground and that they were washed away? Or are they underground and intact perhaps.

Regarding the 50Hz/60Hz issue on the generators they bought in – TEPCO is a local power company it knows Japan uses 50Mz & 60Mz. Hard to believe they’d make such an error.

Map of Japan power grid


‘Here in Chiba, people are freely going outside, kids are playing in the park, we still walk our dog twice day. The tremblors are becoming less and less frequent (I finally got an extended nights sleep last night) and their strength seems to be decreasing (keeping our fingers crossed). There certainly are still reminders of this disaster with the constant news on TV, the huge lineups for gas stations (there is still a major shortage here due to the oil refinery fire in Chiba) resulting in lines of 50+ cars just to get into each gas station, and continuing shortages on the shelves of supermarkets especially for things like fish and mean, bread and yes instant noodles.’

I presume from that that the oil refinery fire is now out, but the article is not specific


@ Phil Daniels,

here’s a google map link to Cosmo Oil plants in Ichihara, Chiba, just half a mile NE,+Prefettura+di+Chiba,+Giappone&aq=0&sll=35.536806,140.062836&sspn=0.003064,0.005981&ie=UTF8&hq=&hnear=Ichihara,+Prefettura+di+Chiba,+Giappone&t=h&ll=35.540398,140.061479&spn=0.024514,0.047851&z=15

if those oil tanks are aflame, would I live in Tokyo, just cross the bay on the left, would be much more worried than by the danger from Fukushima (I assume the cancer threat is the most feared about this incident)


@Cyril R
According to MIT the total decay heat for the 548 fuel rod assemblies removed from Reactor 4 on 30th November 2010 is currently over 6 MW (somewhat over 0.2% of the operating thermal power) I had understood that the decay heat should be obtained as a fraction of the thermal power, not the electrical power, so if experts can confirm this,
the energy generated within each rod in nearly 12kW. Contradicting this number, I have just looked at the Wikipedia page, where the conditions of each reactor are tabulated, a total power level for the pool of reactor 4 given to be only 2 MW, from The pool actually contains 1479 rods in total. If Wikipedia is correct, does this mean the 548 fresh fuel rods were removed after only a short time in the reactor, and MIT are wrong, or is Wikipedia and its reference wrong?

Does anyone know the details?

Experts: in computer model simulations of loss of cooling to spent fuel ponds, is conduction to the surrounding concrete structure included?


Regarding power, this post comes from chavv in another thread:

“People will also ask, why did it take TEPCO so long to start running a new power line to the plant? That would seem like the first thing to be done the minute flood waters had receded.”

Because pumps does not work on regular 220V/110V electricity, they need higher-voltage – 6KV or even more. And high currents too – pumps are quite powerful devices – more than 100KW
Making such high-voltage lines is not so easy…
Due to this problem they also couldn’t use ship for giving electricity, usually military ships work with 400V
(all this is based on info from forums)


Thanks Barry for keeping the site going and not caving to the onslaught of personal attacks.

The situation is not getting worse it seems. This is a good thing, at least from my perspective.

I hope I helped you and others here in a technical sense understand what appeared to be the issues as we all sifted through the random media reports.


Thanks Hank. According to your reference the peak clad temperature remains below the rapid oxidation hydrogen redux reaction, the results are slightly more pessimistic than my iterative thermo model, but the conclusion appears the same: if the roof is opened the hydrogen explosion from spent fuel pool is not a plausible scenario.


Cyril, your pretty close.

The primary containment pressure boundary consists of the drywell and the torus in a technical sense.

What is confusing to laymen is there are two other boundarys for radiation release prior to reaching the primary containment.

The fuel pellet itself along with it’s cladding (zirconium fuel clad tubes), then the reactor pressure vessel and it’s associated system isolation valves. The fuel pellet contains most of the fission product gasses produced due to exposure quite well, until it fails. Most of the fission product gases that build up inside the zirconium tube are outer edge reactions….

As you said energy is then released via steam mixture to the Torus (suppression chamber) below water level to try and condense the steam. When the Torus water level reaches 100C or 212F it can no longer quench the energy of the steam mixture.

At that point, pressure rises due to essentially steam being dumped into a closed volume. Venting must occur to prevent overpressurizaton of the primary containment and permanent failure (complete breach and continued release).

The venting that was done appears to have been to what is technically called the secondary containment (reactor building). Without power there was no complete path with ventilation fan dilution to the stations vent stack. This was bad.

The hydrogen mixed in with the vented steam gas mixture collected at the upper elevations (refueling floors). Ultimately resulting in the explosive concentrations and reactor building damage seen in the photos….


To Phil Daniels:
I’ve seen a japanese clip that clearly shows two cylindrical objects they said were the tanks, placed in open air, almost directly at the waterside just north of the warf. Those were washed away.


Quick summary of news before Barry updates
Hyper rescue team trucks pumped water into number threes building for 13.5hours yesterday and levels of radiation 500m away dropped by about 500micro-sevs to 2906micro-sevs (at 9pm)
5 & 6’s spent fuel pools temperature has fallen steadily since the generators for have been working (5 started first with 6 coming online a little later) 5’s at 43.1c and 6’s at 52 (as of 3am this morning)
Difficulty in site access means that number four hasn’t been doused with water in awhile so the jsdf is going to Spray today… So time…
Also the reactors earthquake Proofing had not been finished so they actually hadn’t been proofed to withstand 600gals of energy… No. 3 was only proofed for 441gals but the energy was 507gals… Etc…


@ Clay

That’s my next hobby, learning to rewind electric motor armatures ;-) – so I haven’t self-educated myself, yet on how important 50 vs. 60 cycle AC is to a motor.


Hi, thanks for your detailed infomations.

Let me ask a question.
I and my family live in Tokyo, Japan atm. My father is arguing that “We should leave Tokyo and go west for our safety! The plants are in danger! We are in danger of death!”. I’m skeptical about that because the effect of the current (or “the worst” future) radiation on Tokyo seems to be minimal and Fukushima plants themselves seem to be getting better.
How do you think about this?


mostly physical rotational speed limitations :) unless you increase the frequency alot higher then insulation issues become more apparent due the corona effect of high frequency AC.


I’ve read that they actually inject hydrogen into the feedwater of BWRs to reduce corrosion. Maybe this was a contributing factor.


Changes in voltage have to be insulated against. The overall power equation will show that changes in voltage will also cause current changes, limitations in heat disipation. Lower the voltage, amperage rises, I squared R increases, heat increases and sometimes max smoke due to insulation failure….

Changes in frequency for rotational machines are more mechanically limited with in reasonable frequency bands of variance …..


Actually its not that simple because control systems may not work on frequencies other than what they were designed for, and as well as mixed frequencies, there are mixed line voltages in Japan (220/110) per phase.

Any rate the reason I mentioned this mixed system is because it causing problems getting power restored in the country. There are two independent grids, and no matter which way you look at it, this is not wise.


According to the ministry, traces of cesium have also been found in tap water in Tochigi and Gunma in addition to the radioactive iodine found in the two prefectures as well as in Niigata, Chiba and Saitama.
To put this report into perspective, which some previous commenters (including bks) failed to do. So don’t worry too much those of you in Japan.
“But the dose of the radioactive substances poses no threat to human health even if they are taken in.

The Nuclear Safety Commission of Japan limits an intake of iodine at 300 becquerels per kilogram of water and of cesium at 200 becquerels.”


Put a multitester on the line , sit at the engine and play the gas. I fought my way through a Einsturzende Neubauten concert on a mine sweeper that way once. The carvers cut out at less than 20V diff. It got quiet only once.


I suspect the two clindrical objects could be the emergency diesel fuel oil tanks that were rumoured to be above ground and washed away by the tsunami. Causing a big design issue for this event.


Agreed, just like most of the media reports/releases. Confusing information released because the spokes people have no clue what they are technically saying….


I got back to a posting I made days ago regarding press releases….

“It wasn’t a fire. It was a spontaneous exothermic reaction resulting in heat and smoke.”


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