The Fires in Spent Fuel Pool Number 4, Fukushima-Diiachi

The Japan Atomic Industry Forum at provides links to its “Reactor Status and Major Events Update – NPPs in Fukushima (Estimated by JAIF) March 2011”. Earliest date provided being Update Number 2, Tuesday March 15 2011 at 10.30 hours.

This status update states that Reactor 4 is “safe”. This report notes the evacuation zone is 20 kms from the NPP.

Status update 3 of 13:00 hours 15 March 2011 states that the evacuation zone is “Evacuation Area 20km from NPS * People who live between 20km to 30km from the Fukushima #1NPS are to stay indoors.”

The update reports also notes that “Remarks: Fire broke (out) on the 4th floor of the Unit-4 Reactor Building around 6AM and the radiation monitor readings increased outside of the building:
30mSv between Unit-2 and Unit-3, 400mSv beside Unit-3, 100mSv beside Unit-4 at 10:22.
It is estimated that the spent fuels stored in the spent fuel pit heated and hydrogen was generated from these fuels, resulting in the explosion. TEPCO later announced the fire had been extinguished.
Other staff and workers than 50 TEPCO employees, who are engaged in water injection operation, have been evacuated.”

It can be seen that the order for people to stay indoors in the defined area occurred after the fire commenced. The view was that that overheating fuel in spent fuel pools generated hydrogen resulting in the explosions. Of interest here is the explosion in reactor 4. Prior to the explosion, Reactor 4 building was intact. After the explosion it was not. The fuel overheated in spent fuel pool 4 and this is sufficient cause to generate hydrogen. This of course means that hydrogen generated within the spent fuel pool occurred regardless of events at reactor 3. The fuel rods in these two fuel pools was overheating and radiation levels outside both reactor buildings was high. JAIF ascribes this to the condition and environment of the spent fuel in both pools. However, it was number 4’s spent fuel pool which experienced fire.

What was burning is not specified. However the fuel is implicated, though no attempt is made to clarify exactly what was burning. The further implication is that fuel rods in the spent fuel pool of Reactor 4 were venting into the air. It is a logical progression from overheat, to explosion, to damaged containment and to the order for people with a defined zone to stay indoors.

The JAIF accident update of 15 March 2011 states that for reactor 4 “SFP level low, Injecting Water SFP Temp. Increasing SFP Temp. Increasing” The text is red flagged by JAIF.

The JAIF accident update of 16 March 2011 08:00 hours states in relation to reactor 4 : “SFP Level Low” red flagged text. The update further states :”Remarks A fire broke on the 4th floor of the Unit-4 Reactor Building around 6AM, Mar. 15, and the radiation monitor readings increased outside of the building: 30mSv between Unit-2 and Unit-3, 400mSv beside Unit-3, 100mSv beside Unit-4 at 10:22, Mar. 15.
It is estimated that spent fuels stored in the spent fuel pit heated and hydrogen was generated from these fuels, resulting in explosion. TEPCO later announced the fire had been extinguished. Another fire was observed at 5:45, Mar. 16, and then disappeared later. Other staff and workers than fifty TEPCO employees who are engaged in water injection operation have been evacuated. ”

IN none of the reports is it concretely stated that fires were composed of burning of fuel rods. However, the clear conclusion gained from reading the reports is that regardless of what was burning, the fuel rods were overheating, measured radiation showed an increase and radically changed procedures for people in a defined area around the NPP ie people had to stay indoors. The conclusion reasonably drawn from this is that there was immediate danger off site to people within a defined area.

The biggest danger to nuclear industry comes when an event has an immediate effect on civilians in surrounding areas. Hence people were instructed to stay indoors. At this time, the possibility of severe consequences were being denied by world nuclear industry. However, the nature of the accident had obviously changed with the overheating of the fuel rods in the spent fuel pools. Further, while the first fire was claimed to be extinguished on the 15th March 2011 by TEPCO, another fire was reported as burning at 05:45 on March 16. It “disappeared later”.

On 16 March 2011, 7:16 PM, by Eli Kintisch, staff writer for Science Insider at wrote an article entitled “Contention Over Risk of Fire From Spent Fuel Pools”

In this article Kintisch states: ” Among the worst case scenarios at the Fukushima plant is that the spent nuclear fuel, which sits in essentially open cooling pools near the six nuclear reactors, could catch fire for a prolonged period and spew tons of radioactive dust in a radioactive plume. It appears some of the spent fuel has been on fire at reactor #4; fire occurs if the rods get hot enough to burn their cladding. Reports say that high levels of radioactivity have made it difficult to fight the fire, which appears to have continued to burn late Wednesday. Today, U.S. Nuclear Regulatory Commission (NRC) head Gregory Jaczko said that the pool at reactor #4 had run dry; Japanese authorities denied this. …”

If it were the fuel rod cladding which was burning then there may very well be grounds for considering that the overheating event in the fuel pool of reactor 4 had produced rapid oxidation (which may or may not produce what is normally considered to be a flame) in the fuel rod cladding. The salient point being the damage done to the integrity of the fuel rod cladding. For where the cladding fails, there is, in the absence of sufficient water in the spent fuel pool, a direct of radiation into the air, and where outer containment has failed, as occurred in reactor 4 resultant from the explosions there, the venting of fission and fuel products enters the outside air unimpeded.

It is easy to conclude therefore that people in a defined area around the NPP were ordered to stay indoors due to the emissions from the nuclear power plant’s number four spent fuel pool and the fresh spent fuel rods stored there.

It is my view that rapidly oxidizing metals such as zircalloy may rapidly oxidize either with or without flame. The relevant factor being the integrity of the cladding. There was a crisis in the spent fuel pool four which did not “go away” when the flames did. It was present throughout. Hence the amended procedure for people outside the plant in a defined area to stay indoors.

It may be that the cascade of disaster in spent fuel pool 4 would have occurred even if reactor number 3 had not exploded. It appears the hydrogen in the reactor building number 4 was resultant from overheating in the fuel which occurred after reactor had been destroyed. That is, there is a possibility that the hydrogen which caused the later explosion in reactor number 4 had not originated in reactor number 3 (as claimed by TEPCO) but had instead originated in spent fuel pool 4 due to overheating zirconium in that pool reacting with air and water to produce hydrogen indigenous to the circumstances in the fuel rods in that fuel pool. That is, the containment building of reactor 4 failed (was sufficiently destroyed to cripple its protective function) purely by a fuel pool overheat within that building.

On 16 March 2011 JAIF states that the spent fuel pool 4 has low water, and that spraying had commenced. The crisis had commenced with the explosion and fire of the 14 March 2011. The events reported on 15 and 16 March 2011 is in fact the same event – the overheating of fuel rods in spent fuel pool 4 and the major consequence was the unsealing of the sealed sources – the fuel within the rods – and the released was not confined to the building, due to damage. As a result people in an area around the power plant had to stay indoors. The nature of the disaster, in my view, thus changed greatly in nature. The escalation of the disaster was rapid and dire. People had to seal themselves in their homes, if they still had a home. If they were no on the road in the process evacuation. If the defined area was adequate.

But still, from these brief technical reports, it is impossible to concretely lift from them what was actually burning.

Turning to the Australian Broadcasting Commission (ABC) we find this report:

Tuesday March 15, 2011, 18:10 hours. Headline “Explosion at No 4 Fukushima Reactor” MARK COLVIN: The Fukushima nuclear disaster has moved up the ladder from the third-worst civilian nuclear accident in history to the second, now behind only Chernobyl. With explosions at three of the plant’s reactors, and now a fire in spent fuel at reactor number four; it’s now a good deal worse than the 1979 Three Mile Island disaster.

The International Atomic Energy Agency says radiation levels around the plant are now 400 millisieverts an hour. That means that every six minutes eight times as much radiation are spewing out as nuclear workers are normally supposed to absorb in a year.

And the authorities are getting no help from the elements. Instead of blowing east and out to sea, as on most days, the smoke from the burning nuclear fuel is drifting south. About halfway to Tokyo at Utsunomiya, radiation is registering 33 times normal, still not a serious threat to health if things get better soon.

In the capital itself the level is less, 23 times normal. Earlier, the prime minister Naoto Kan briefly addressed the nation on television pleading for calm. …”

The Japanese people were, to my eyes, calm. It was the nuclear industry which was in panic.

However the report from the ABC defines what was “on fire”. It was the fuel rods.

The significance of this is not the fire per se, it is the thermal damage which is evidenced by such rapid oxidation of zircalloy cladding. Compounded by the fact that the reactor building, the only thing between the fuel pool contents and the open air, was obviously not designed to withstand a fuel pool sourced release of hydrogen and subsequent explosion. The damaged fuel rods were now free to vent into the open air. Can we find any historical evidence to show that the reactor building in use at reactor 4 was sub standard? Yes we can. I will return to this later. But briefly, US regulators found the design to be inadequate, but superiors approved the design because, in the words of one, it would create too much hassle to change the design. The design was approved and exported to Japan.

The narrative that implies it took two reactor buildings worth of hydrogen to destroy containment at Reactor number is a phony one I think and believe, on the basis of the news reports, photograph and technical reports. Rationality is challenged by the industry. The energy of Reactor 3’s hydrogen yield was used in the destruction of reactor 3 prior to the destruction of reactor 4’s containment.

How does the New York Times handle the situation? In my opinion, it does not define the fire, but it highlights the personnel who reduced the level of disaster. It is correct to include such acknowledgement. It is wrong to fully explain what it was precisely the personnel faced, what precisely was the situation which led to the evacuation of all but 50 or so staff, and the sealing of the affected Japanese civilian population in their own homes because nuclear industry had failed to design adequate sealing of its radioactive sources.

For all its ability to feed the grid, to power the grid, the multi reactor plant at Fukushima failed to power itself. It thus could cool neither the reactors or the spent fuel pools. And they failed. And did the impossible and stated as that, from the dawn of the nuclear age. Arrogant design.

Here’s the New York Times of 16 March 2011. What does the piece define about the actual fuel pool venting and containment failure at reactor 4?

Last Defense at Troubled Reactors: 50 Japanese Workers
Published: March 15, 2011 New York Times.

“A small crew of technicians, braving radiation and fire, became the only people remaining at the Fukushima Daiichi Nuclear Power Station on Tuesday — and perhaps Japan’s last chance of preventing a broader nuclear catastrophe. …” The piece is about the people, not the fire. But it is the bravery demanded by the consequences of overheat which makes the story. The result of overheat in a fuel pool is radiation release where the containment building has failed. One can still appreciate the personnel while one seeks the technical details. Air crash investigations don’t stop work because the crew were brave on a doomed flight. Rather, the need to stop a repeat and further suffering and loss drives the quest for truth. The NYT in this article does not enlighten us at all as what caused the need for such bravery, whether on site or in the homes of those forced to sealed themselves up in their homes at that time.

In another article, the New York Times did provide information of great value. Information which few others, if any, provided at the same time.

On 5 April 2011, the New York Times published a piece which cited a confidential NRC report on the events at Fukushima Diiachi.

U.S. Sees Array of New Threats at Japan’s Nuclear Plant
Published: April 5, 2011 New York Times

“United States government engineers sent to help with the crisis in Japan are warning that the troubled nuclear plant there is facing a wide array of fresh threats that could persist indefinitely, and that in some cases are expected to increase as a result of the very measures being taken to keep the plant stable, according to a confidential assessment prepared by the Nuclear Regulatory Commission. ….The document also suggests that fragments or particles of nuclear fuel from spent fuel pools above the reactors were blown “up to one mile from the units,” and that pieces of highly radioactive material fell between two units and had to be “bulldozed over,” presumably to protect workers at the site. The ejection of nuclear material, which may have occurred during one of the earlier hydrogen explosions, may indicate more extensive damage to the extremely radioactive pools than previously disclosed.”

The rapid oxidation of zirconium in air and water releases amounts of hydrogen which explodes with terrible force. This process was ongoing in spent fuel pool 4 and there is no need to invoke hydrogen from reactor 3 in this regard. The spent fuel pool was over heating as admitted by JAIF. Thus, containing the entire fresh fuel from the recently emptied reactor 4, was producing and releasing hydrogen gas. And it exploded. Destroying containment.

IAEA ENAC Data – March 15th – Reactor 4 Spent Fuel Pool Fire – Pages from ML12037A104 – FOIA PA-2011-0118, FOIA PA-2011-0119 & FOIA PA 2011-0120 – Resp 41 – Partial – Group DDD Part 2 of 3. (138 page(s), 1 24 2012)-6 (source link)

There are a number of people who maintain that there was no fire or fires in any of the spent fuel pools. The NRC maintained at the time that the spent fuel pool at reactor 4 was empty. The Japanese authorities deny this. However, The Japan Atomic Industry Forum reports that the water level in that fuel pool was low and that the fuel rods in the pool were overheating. I bear in mind the basic process of “fire” in a reactive metal. It is rapid oxidation which may or may not be accompanied by a flame. What defines a “fire” in an ordinary sense – the flame – may be totally absent or sporadically present in the case of a reactive metal. In the case of fuel rods two things are relevant: the integrity of the zircalloy cladding and the temperature of the zircalloy. For it is the temperature that seems to determine the point at which hydrogen is liberated from water and air and the rate it is liberated. The fuel rods were overheating in fuel pool 4 and hydrogen was being generated.

That is all that really needs to be established and it is admitted by Japan. As a consequence, spraying of water by hose commenced. This was done from outside the building – and was possible to do only because the containment building had been destroyed by hydrogen explosion. The building was too weak to do its job. The trigger for this aspect of the disaster was loss of ability to cool the water in the pool. And that was caused by earthquake.

There is little way of independently knowing when re occurrence of fuel rod overheating happens at the crippled plant. The potential remains for re occurrence. The older the rods become, the less dangerous they become. In 2011 the situation was dire. The fuel pools are not the only source of risk. There are the ongoing emissions from the molten fuel.

What was the response of the Japanese governmental to the fires in the spent fuel pool 4 in March 2011?

To answer that question, I refer to “Stars and Stripes”, which provides a round of sources in relation the events.

“4:20 p.m. Tuesday local Tokyo time, source: Associated Press:
High levels of radiation leaked from a crippled nuclear plant in tsunami-ravaged northeastern Japan after a third reactor was rocked by an explosion Tuesday and a fourth caught fire in a dramatic escalation of the 4-day-old catastrophe. The government warned 140,000 people nearby to stay indoors to avoid exposure.

Tokyo also reported slightly elevated radiation levels, but officials said the increase was too small to threaten the 39 million people in and around the capital, about 170 miles away.

12:30 p.m. Stars and Stripes reporter – Tim Wightman

Power plant reactor fire extinguished
TOKYO – Japan’s nuclear safety agency says a fire in a reactor at the Fukushima nuclear power plant in tsunami-ravaged northeastern Japan has been extinguished, The Associated Press is reporting. The fire broke out Tuesday at the nuclear plant, located in one of the provinces hardest-hit by last week’s massive earthquake and tsunami.

11:45 a.m. Stars and Stripes Reporter – Tim Wrightman

TOKYO – Japan Prime Minister Naoto Kan has told people living within 19 miles (30 kilometers) of the Fukushima Dai-ichi complex to stay indoors or risk getting radiation sickness, The Associated Press is reporting.
Chief Cabinet Secretary Yukio Edano said Tuesday that a fourth reactor at the Fukushima Dai-ichi complex was on fire and that more radiation was released.
Kan also warned that more leaks could occur.

10:55 a.m. Tuesday Stars and Stripes Reporter Tim Wrightman

TOKYO – The early Tuesday explosion at the Fukushima Dai-ichi nuclear power plant may have damaged a reactor’s container, leading Japan’s nuclear safety agency to suspect a radiation leak, The Associated Press is reporting.
According to agency spokesman Shigekazu Omukai, the nuclear core of Unit 2 of the plant was not damaged “in the explosion. But the agency suspects damage to the bottom of the container that surrounds the generator’s nuclear core, which could’ve caused radiation to escape.”

end quote.

On March 15 2011 TEPCO issued a Press Release regarding the fire in the reactor 4 building as follows:

The report reads as follows:

“Press Release (Mar 15,2011)
Damage to the Unit 4 Nuclear Reactor Building at Fukushima Dai-ichi Nuclear Power Station

At approximately 6:00am, a loud explosion was heard from within the
power station. Afterwards, it was confirmed that the 4th floor rooftop
area of the Unit 4 Nuclear Reactor Building had sustained damage.

After usage, fuel is stored in a pool designated for spent fuel.

Plant conditions as well as potential outside radiation effects are
currently under investigation.

TEPCO, along with other involved organizations, is doing its best to
contain the situation. Simultaneously, the surrounding environment is
being kept under constant surveillance. “

The following link is to the IAEA Fukushima Nuclear Accident Update page for 15 March 2011 :

The report is a record of the findgins and reports of the IAEA and in relation to the fire, the IAEA states the following:

“A fire at Unit 4 occurred on 14 March 23:54 UTC and lasted two hours. The IAEA is seeking clarification on the nature and consequences of the fire.”

On the same day, in the midst of disagreement between the NRC and the Japanese authorities (in which NRC viewed with alarm the water level of the spent fuel pool 4), the IAEA issued its alert to member governments. The alert describes the fuel pool fire in spent fuel pool 4. This document is only known due to an FOIA release in the United States. The next day the IAEA Fukushima Nuclear Accident Update report for 16 March 2011 at

reported the following:

“Fukushima Nuclear Accident Update (16 March 2011, 22:00 UTC)

Temperature of Spent Fuel Pools at Fukushima Daiichi Nuclear Power Plant

Spent fuel that has been removed from a nuclear reactor generates intense heat and is typically stored in a water-filled spent fuel pool to cool it and provide protection from its radioactivity. Water in a spent fuel pool is continuously cooled to remove heat produced by spent fuel assemblies. According to IAEA experts, a typical spent fuel pool temperature is kept below 25 °C under normal operating conditions. The temperature of a spent fuel pool is maintained by constant cooling, which requires a constant power source.

Given the intense heat and radiation that spent fuel assemblies can generate, spent fuel pools must be constantly checked for water level and temperature. If fuel is no longer covered by water or temperatures reach a boiling point, fuel can become exposed and create a risk of radioactive release. The concern about the spent fuel pools at Fukushima Daiichi is that sources of power to cool the pools may have been compromised.

The IAEA can confirm the following information regarding the temperatures of the spent nuclear fuel pools at Units 4, 5 and 6 at Fukushima Daiichi nuclear power plant:
Unit 4
14 March, 10:08 UTC: 84 °C
15 March, 10:00 UTC: 84 °C
16 March, 05:00 UTC: no data”

The IAEA is continuing to seek further information about the water levels, temperature and condition of all spent fuel pool facilities at the Fukushima Daiichi nuclear power plant.
IAEA Director General to Travel to Japan (16 March 2011, 18:50 UTC)

Director General Yukiya Amano announced the following today in Vienna:

“I plan to fly to Japan as soon as possible, hopefully tomorrow, to see the situation for myself and learn from our Japanese counterparts how best the IAEA can help. I will request that the Board of Governors meet upon my return to discuss the situation. My intention is that the first IAEA experts should leave for Japan as soon as possible.”

On 15 March, Japan requested the IAEA for assistance in the areas of environmental monitoring and the effects of radiation on human health, asking for IAEA teams of experts to be sent to Japan to assist local experts.

Given the fast-changing situation in Japan, the Director General was unable to announce the itinerary for his trip. He expects to be in Japan for a short amount of time and then return to Vienna.

Fukushima Nuclear Accident Update (16 March 2011, 14:55 UTC)

Japanese authorities have reported concerns about the condition of the spent nuclear fuel pool at Fukushima Daiichi Unit 3 and Unit 4. Japanese Defense Minister Toshimi Kitazawa announced Wednesday that Special Defence Forces helicopters planned to drop water onto Unit 3, and officials are also preparing to spray water into Unit 4 from ground positions, and possibly later into Unit 3. Some debris on the ground from the 14 March explosion at Unit 3 may need to be removed before the spraying can begin.
Fukushima Nuclear Accident Update (16 March 2011, 03:55 UTC)

Japanese authorities have informed the IAEA that a fire in the reactor building of Unit 4 of the Fukushima Daiichi nuclear power plant was visually observed at 20:45 UTC of 15 March. As of 21:15 UTC of the same day, the fire could no longer be observed.

Fire of 14 March

As previously reported, at 23:54 UTC of 14 March a fire had occurred at Unit 4. The fire lasted around two hours and was confirmed to be extinguished at 02:00 UTC of 15 March.” end quote.

But we need to keep in mind, fire or not, the fuel rods were at that time still overheating. And what, in relation to a reactive metal, does the word ‘fire’ actually mean? Rate of oxidation is related to temperature. A more important question is how much of the fuel rod inventory in spent fuel pool 4 was damaged and venting? Has it stopped venting since?

A look at the nature of zirconium is relevant.

Autoignition Temperature: Solid metal will not ignite. High surface area material such as 10 micron powder may autoignite at room temperature. Fine chips, turnings, or grinding dust produced from this metal are flammable. Ignition point for powder varies from 200 oC to above 500 oC depending on particle size.

Minimum Explosible Concentration (g/m3): Less than 100. Varies with particle size.

Extinguishing Media: Dry table salt. Type D fire extinguisher. DO NOT USE water, carbon dioxide or halocarbon extinguishing agent.

Special Firefighting Procedures: If metal fines become ignited it is advisable to allow the material to burnout. Fire can be controlled by smothering with dry table salt or using Type D dry-powder fire extinguisher material. Wear reflective heat-resistant suit.

Unusual Fire & Explosion Hazard: Do not spray water on burning zirconium. Carbon dioxide is not effective in extinguishing burning zirconium.

If a fire starts in a mass of wet metal fines, the initial fire may be followed by an explosion. Therefore, when in doubt, personnel should retire and not attempt to extinguish the fire. The explosive characteristic of such material is caused by the steam and hydrogen generated within the burning mass.

Spontaneously combustible in dry powder form. Flammable and explosive as dust or powder, also in the form of borings and shavings. Zirconium metal is a very dangerous fire hazard in the form of dust when exposed to heat, flame or by chemical reaction with oxidizing agents. May be an explosion hazard in the form of dust by chemical reaction with air, alkali hydroxides, alkali metal chromates, dichromates, molybdates, sulfates, tungstates, borax, CCl4, copper oxide, lead, lead oxide, phosphorous, KClO3, KNO3, nitryl
fluoride. May be extremely sensitive to shock, and static electricity may cause spontaneous ignition.
Material Safety Data Sheet – Zirconium”

In relation to the behaviour of zircalloy in reactor applications, temperature determines its rate of reactivity, release of hydrogen and loss of structural integrity.

While zirconium can burn, the relevant outcome with overheat is release of fission product.

Reactor 4 and fuel pool containment after the events described above. The industry claimed for many months that the structure was sound. Steps are being attempted to shore it up.

A reader who wishes to remain unkown, has contributed the following information. He writes:

“I found this TV news report by Tim Maguire of Associated Press, which uses NHK footage with text superimposed in Japanese concerning Unit 4. The clip was uploaded to AP’s channel on YouTube, 15 March 2011,

“A new fire has broken out at the Fukushima Daiichi nuclear plant one day after the facility admitted a burst of radiation that left the government struggling to contain the spiralling crisis.

“The latest blaze happened early Wednesday morning, local time, in the number 4 unit.

“The plant’s operator says the fire occurred in the outer housing of that unit’s containment vessel – but it’s not clear what caused the fire.

“Tuesday, a fire broke out in the same reactor’s fuel storage pond – that’s an area where used nuclear fuel is kept cool – and radioactivity was released into the atmosphere.

Tokyo electric power said the new blaze erupted early Wednesday because the initial fire had not been fully extinguished, and firefighters were trying to put it out.” Associated Press.

And this last comment explains something which is pretty predictable given the nature of overheating zircalloy. Overheat means rapid oxidation. But it does not mean a flame is seen. The flame went out, the fuel rods continued over heating, and again a flame was seen. The period of no flame is not a period of safety. It is still a period of rapid oxidation,fuel rod damage and release of radioactive material.

This extended period of rod over heat in the fuel pool is described in Science Insider, as previously noted, here: The salient fact is rod overheat, resultant damage and release of radiological material. Putting out the flames is not the same as cooling the rods. The overheating became serious on 15 March 2011. When did rod over heat and contents release stop? Has it stopped? Absence of flame is not absence of overheat.

In all this I am aware that the industry culture is one which nuclear fission is the norm. Multi mega-watt reactors deliver grid power and nuclear material by the very process. The industry culture is thus such that it would not be normal for the observation of sporadic neutron beams to cause much reaction. Apart from perhaps, “Gee whizz, there’s life in the old girl yet.”

Wikipedia at,_5_and_6#Explosion states the following:

“At approximately 06:00 JST on 15 March, an explosion damaged the 4th floor rooftop area of the Unit 4 reactor as well as part of the adjacent Unit 3.[12][13] The explosion is thought to be caused by the ignition of hydrogen that had accumulated near the spent fuel pond, the hydrogen was initially thought to have come from the stored fuel rods, but later, TEPCO believed the hydrogen came from Unit 3.[14] Later reports from the US Nuclear Regulatory Commission speculated that fuel could have been ejected from the Unit 4 spent fuel pond during this explosion.[15] Later on the morning of 15 March, at 09:40, the Unit 4 spent fuel pool caught fire, likely releasing radioactive contamination from the fuel stored there.[16][17] TEPCO said workers extinguished the fire by 12:00.[18][19] As radiation levels rose, some of the employees still at the plant were evacuated.[20] On the morning of 15 March, Secretary Edano announced that according to the TEPCO, radiation dose equivalent rates measured from the Unit 4 reached 100 mSv/h.[21][22] Edano said there was no continued release of “high radiation”.[23]

Japan’s nuclear safety agency NISA reported two holes, each 8 meters square, or 64 m² (690 sq ft), in a wall of the outer building of Unit 4 after the explosion.[24] At 17:48 it was reported that water in the spent fuel pool might be boiling.[25][26] By 21:13 on 15 March, radiation inside the Unit 4 control room prevented workers from staying there permanently.[27] Seventy staff remained at the plant, while 800 had been evacuated.[28] By 22:30, TEPCO was reportedly unable to pour water into the spent fuel pool.[4] By 22:50, the company was considering using helicopters to drop water,[28][29] but this was postponed because of concerns over safety and effectiveness, and the use of high-pressure fire hoses was considered instead.[30]

A fire was discovered at 05:45 JST on 16 March in the northwest corner of the reactor building by a worker taking batteries to the central control room of Unit 4.[31][32] This was reported to the authorities, but on further inspection at 06:15 no fire was found. Other reports stated that the fire was under control.[33] At 11:57, TEPCO released a photograph showing “a large portion of the building’s outer wall has collapsed”.[34] Technicians considered spraying boric acid on the building from a helicopter.[35][36]” The source links to the piece are interesting.

12. World Nuclear News.
A major struggle took place today to maintain cooling of used nuclear fuel at Fukushima Daiichi 3 and 4. Helicopters made water drops and large fire trucks showered the buildings. Initial indications are that the effort was successful.

The explosion at unit 4 is thought to have been from a build-up of hydrogen in the area near the used nuclear fuel pond. It severely damaged the building, as well as that of adjacent unit 3, with which it shares a central control room.

Cooling pond temperatures
As reported by the International Atomic Energy Agency:
Unit 4
14 March, 10.08am GMT: 84 ˚C
15 March, 10.00am GMT: 84 ˚C
16 March, 05.00am GMT: no data
Unit 5
14 March, 10.08am GMT: 59.7 ˚C
15 March, 10.00am GMT: 60.4 ˚C
16 March, 05.00am GMT: 62.7 ˚C
Unit 6
14 March, 10.08am GMT: 58.0 ˚C
15 March, 10.00am GMT: 58.5 ˚C
16 March, 05.00am GMT: 60.0 ˚C
Neither the IAEA nor the Japan Atomic Industry Forum have data for units 1, 2 and 3.
Today the situation of the cooling ponds was the priority of authorities. Containing highly radioactive heat-generating nuclear fuel, they require an adequate level of water to be maintained as well as pumped circulation to control water temperature.

In the previous two days the temperature of unit 4’s pond had been 84ºC but no more recent data is available. At these temperatures cooling by natural convection begins to be markedly less effective. Normal operating levels are about 25ºC. There was no information on the temperature of the pond at unit 3.

However, the high levels of radiation and presence of hydrogen at unit 4 strongly indicate that fuel is uncovered and suffering damage in the pond, although it was not clear that the pond actually emptied. Officials were reassured the pond contained at least some water, based on helicopter observations.

13. ^ “Press Release: Damage to the Unit 4 Nuclear Reactor Building at Fukushima Dai-ichi Nuclear Power Station”. TEPCO. Retrieved 15 March 2011. ”
Press Release (Mar 15,2011)
Damage to the Unit 4 Nuclear Reactor Building at Fukushima Dai-ichi Nuclear Power Station

At approximately 6:00am, a loud explosion was heard from within the
power station. Afterwards, it was confirmed that the 4th floor rooftop
area of the Unit 4 Nuclear Reactor Building had sustained damage.

After usage, fuel is stored in a pool designated for spent fuel.

Plant conditions as well as potential outside radiation effects are
currently under investigation.

TEPCO, along with other involved organizations, is doing its best to
contain the situation. Simultaneously, the surrounding environment is
being kept under constant surveillance. ”

14. “TEPCO: Unit No.4 blast due to hydrogen from Unit No.3”. NHK. 16 May 2011. Retrieved 2 June 2011.[dead link]

(It can be seen that the date TEPCO’s change to its story was 16 May 2011. Prior to that change, Hydrogen generated by fuel rod cladding in the number 4 spent fuel pool had been the acknowledged source of the hydrogen.)

15. “Levels of radioactive iodine had reached 7.5 million times permissible levels directly behind the plant Saturday, but by Tuesday new measurements showed that the amount of radioiodine was only 4% of that amount. That was still nearly 300,000 times the permissible limit, but levels were continuing to decline as the outflow from the plant was being diluted by the ocean.

At a point about 12.5 miles from the plant, iodine levels were down to 1.5 times the limit.”,0,6240900.story Los Angeles Times
y Thomas H. Maugh II, Los Angeles Times April 6, 2011, 11:57 a.m.


“IAEA Briefing on Fukushima Nuclear Accident (2 June 2011, 18:30 UTC)

Overall, the situation at the Fukushima Daiichi nuclear power plant remains very serious.

Fresh water is being injected as necessary into the spent fuel pools of Units 1 – 4. Water supply from concrete pump trucks is being gradually replaced by the Fuel Pool Cooling and Clean-up system in Units 1 to 3. However, closed loop cooling has not been yet established.

17. Reuters Japan spent fuel pond on fire,radioactivity out-IAEA
VIENNA, March 15 | Tue Mar 15, 2011 2:44am EDT

(Reuters) – Japan has told the U.N. nuclear watchdog a spent fuel storage pond was on fire at an earthquake-stricken reactor and radioactivity was being released “directly” into the atmosphere, the Vienna-based agency said.

The International Atomic Energy Agency (IAEA), citing information it had received from Japanese authorities, said dose rates of up to 400 millisievert per hour have been reported at the Fukushima power plant site.

“The Japanese authorities are saying that there is a possibility that the fire was caused by a hydrogen explosion,” it said in a statement.

(Reporting by Fredrik Dahl; editing by Michael Roddy)

19 “World Nuclear News Update”. 15 March 2011.World Nuclear News
Fire at unit 4, concern for fuel ponds
Prime minister Naoto Kan confirmed a fire burning at unit 4, which, according to all official sources, had never been a safety concern since the earthquake. This reactor was closed for periodic inspections when the earthquake and tsunami hit, therefore did not undergo a rapid and sudden shutdown. It was of course violently shaken and subject to the tsunami.
Kan’s spokesman Noriyuki Shikata said that there had been “a sign of leakage” while firefighters were at work, “but we have found out the fuel is not causing the fire.” The fire is now reported extinguished.

The International Atomic Energy Agency did confirm that the fire had taken place in the used fuel storage pool. The Japan Atomic Industry Forum’s status report said the water was being supplied to make up for low levels.
Similar to the need to cool fuel in the reactor core, used fuel assemblies in cooling ponds require a covering of water to remove decay heat. The main differences being the amount of decay heat to be removed decreases exponentially with time and that fuel ponds are much less of an enclosed space than a reactor vessel. At the same time, ponds may contain several years of fuel.
JAIF reported that temperatures in the cooling ponds at units 5 and 6 are increasing, but the reason for this is not yet available.”
Researched and written
by World Nuclear News end quote.

Line Wolf Noriyuki Shikata might be correct, probably not, however, even if he is, how does he explain the overheating of the fuel and consequent Hydrogen release and radioactivity release from the damaged rods? That is the salient point. The released of sealed radiological material which must NEVER be unsealed and scattered over the nation and world. There is much political pap in the Fukushima story.
Apparently aimed at stilling public fear, but which of course have another purpose. Staving off stock price falls on the Japanese exchange.

20. ^ “Radiation levels could damage health”. Canadian Broadcasting Corporation. 14 March 2011. Retrieved 15 March 2011.

^ “放射線、福島原発で400ミリシーベルト=「人体に影響及ぼす可能性」-官房長官”. jiji press (in Japanese). 15 March 2011. Retrieved 15 March 2011.More than one of |work= and |newspaper= specified

22. Radiation levels spike at Japanese nuclear plant
By the CNN Wire Staff
March 15, 2011 — Updated 0316 GMT (1116 HKT) Tokyo (CNN) — Japanese authorities trying to stave off meltdowns at an earthquake-damaged nuclear power plant reported more grim news Tuesday as radiation levels soared following another explosion at an overheating reactor.

The risk of further releases of radioactive material from the Fukushima Daiichi nuclear power plant remains “very high,” Japanese Prime Minister Naoto Kan said Tuesday. In addition to an explosion at the No. 2 reactor, the building housing the No. 4 unit — which had been shut down before Friday’s earthquake — was burning Tuesday morning, Chief Cabinet Secretary Yukio Edano announced.

The plant’s owners, the Tokyo Electric Power Company, evacuated all but about 50 of their workers from the plant following Tuesday’s explosion at the No. 2 reactor. Radiation levels at the plant have increased to “levels that can impact human health,” Edano said — between 100 and 400 millisieverts, or as much as 160 times higher than the average dose of radiation a typical person receives from natural sources in a year.

Evacuations have already been ordered for anyone living within 20 kilometers (12.5 miles) of the plant, and Edano said anyone between 20 and 30 kilometers (between 12.5-18.6 miles) should remain indoors. At least 500 residents were believed to have remained within the 20-kilometer radius Monday evening, Edano said.


Asia-Pacific News
Government spokesman: No continued radiation from reactor 4

Mar 15, 2011, 8:07 GMT
Tokyo – Japanese government spokesman Yukio Edano said Tuesday there was no continued release of high radiation from reactor number 4 of the Fukushima nuclear power plant, where an explosion occurred earlier in the day. end quote. But the fuel rods in 4 continued to overheat and this statement came at the same time as the stay indoors with windows and doors shut order was in place, at the same time as IAEA was alerting member states.

24 Asia-Pacific News Government spokesman: No continued radiation from reactor 4 Mar 15, 2011, 8:07 GMT
TOKYO, March 15 | Tue Mar 15, 2011 5:30am EDT
(Reuters) – Japan’s nuclear safety agency said on Tuesday there were two holes of 8-metres square in a wall of the outer building of the quake-hit Fukushima Daiichi No.4 reactor after a blast in the morning. (Reporting by Taro Fuse; Edited by Edwina Gibbs) end quote. Severe loss of containment for fuel pool radiological emissions.

25. dead BBC link

26 “Fukushima No. 4 reactor spent fuel pool may be boiling -Kyodo”. Reuters. 15 March 2011.

27 Fujioka, Chisa (11 March 2011). “Radiation hits dangerous levels at Japan plant control room”. Reuters. Retrieved 15 March 2011.

28 Yuasa, Shino (15 March 2011). “Japan to spray water and boric acid on stricken nuke plant”. Retrieved 7 April 2011.

29 “Nuclear officials may spray Japanese power plant with water by helicopter”. Fox News. Associated Press. 7 April 2010. Retrieved 15 March 2011.

30 “Workers evacuated from Japanese nuclear reactor”. North Country Public Radio. Retrieved 18 March 2011.

31 “Press release: Fire occurrence at Fukushima Daiichi nuclear power station Unit 4 (2nd release)”. TEPCO. Retrieved 18 March 2011.

32 “Fire breaks out again at Fukushima’s No. 4 reactor”. Kyodo News. 16 March 2011. Retrieved 15 March 2011. dead link

37 ^ JAIF (26 June 2012) Earthequake report 452: Tilted walls found at Fukushima No.4 reactor
Tokyo Electric Power Company has announced the No. 4 reactor at Fukushima
Daiichi nuclear plant has tilted walls caused by a hydrogen explosion in March
last year.
The building still contains large stockpiles of nuclear fuel. But the plant operator
TEPCO says its quake resistance is not affected.
TEPCO first found the tilted walls last month. A further investigation found the
damage in various parts of the structure’s west and south side.
The most extreme tilt was on the 3rd floor, where the wall was found to be
leaning 4.6 centimeters.
Spokesmen said the tilts are all within legal limits, and the walls’ strength
satisfies standards, too.
The building’s spent fuel pool stores more than 1,500 nuclear fuel rods, the
largest number among the Fukushima plant’s reactors.
But TEPCO stresses that building is safe, as the tilts were found in outer walls.
The pool itself is supported by pillars and other structures.
Jun. 25, 2012 – Updated 21:28 UTC (06:28 JST)

end quote. Though many nuclear experts poo poo’d the idea of strucutural instability, when I asked one engineer, who runs a nuclear industry blog, whether he thought the spent fuel pool was in good nick he said no it was not. I wouldnt licence it for continued use. What lunatic would?

38 “No water in spent fuel pool at Japanese plant: U.S.”. CTV News. 16 March 2011.
Earlier, a U.S. official said all of the water is gone from one of the spent fuel rod pools at the plant, meaning there is nothing to stop the fuel rods from getting hotter and eventually melting down, but Japan denied the claim.

“There is no water in the spent fuel pool and we believe that radiation levels are extremely high, which could possibly impact the ability to take corrective measures,” chief of the U.S. Nuclear Regulatory Commission Gregory Jaczko said at a House Energy and Commerce subcommittee hearing Wednesday.

The outer shell of the rods could also explode with enough force to propel radioactive fuel over a wide area, if Jaczko is correct.

He said the problem is at the complex’s Unit 4 reactor.

Jaczko did not say how the information was obtained but the organization and the U.S. Department of Energy have experts on the site.

The U.S. is also calling on Americans in Japan to stay at least 80 kilometres away from the plant. Japan’s official evacuation zone is only about 20 km.

Japanese nuclear officials and Tokyo Electric Power Co., which operates the facility, have denied water is gone from the pool.

Read more:

39 “Japan nuclear crisis: Meltdown at Fukushima Daiichi plant may now be inevitable”. New York Daily News. 17 March 2011.

40 Sanger, David E.; Wald, Matthew L.; Tabuchi, Hiroko (17 March 2011). “U.S. calls radiation ‘extremely high,’ sees Japan nuclear crisis worsening”. The New York Times.

45 Ralph Vartabedian; Barbara Demick; Laura King (18 March 2011). “U.S. nuclear officials suspect Japanese plant has a dire breach”. Los Angeles Times. Retrieved 18 March 2011.,0,2262753.story

By Ralph Vartabedian, Barbara Demick and Laura King, Los Angeles Times

March 18, 2011, 1:50 a.m.
Reporting from Los Angeles, Kesennuma and Tokyo—
U.S. government nuclear experts believe a spent fuel pool at Japan’s crippled Fukushima reactor complex has a breach in the wall or floor, a situation that creates a major obstacle to refilling the pool with cooling water and keeping dangerous levels of radiation from escaping.

That assessment by U.S. Nuclear Regulatory Commission officials is based on the sequence of events since the earthquake and information provided by key American contractors who were in the plant at the time, said government officials familiar with the evaluation. It was compelling evidence, they said, that the wall of the No. 4 reactor pool has a significant hole or crack.

46 Hiroko Tabuchi; Keith Bradsher (18 March 2011). “Frantic repairs go on at plant as Japan raises severity of crisis”. The New York Times. Retrieved 18 March 2011.

end quotes. Something happened in the spent fuel pool number 4. It resulted in a massive release of nuclear material as particulates from over heated and damaged fuel rods. Visible fires intermittently burst forth, to be put out. The lack of flame did not mean no overheat. Water was low or absent totally. The situation became very severe as a result. TEPCO evacuated all staff bar 50 or so and ordinary people were ordered to stay indoors. Meanwhile, nuclear “experts” claimed the situation was fine, that no material would fall out side the TEPCO site. Japanese government comments were very overly optimistic at times. The situation lent itself to confused reports. There is no argument though that the Japanese government was shattered to the extent that all trust in the nuclear industry to preserve Japan was lost. The Prime Minister visited the plant and the IAEA head shortly followed, saying all is well. At the time a Frenchman wearing a hazmat suit was arrested in Tokyo. The same city which had in fact been rained upon by radionuclides from the fuel pool stock.

reactivity of cesium

reactive metals


The Element Cesium

[Click for Isotope Data]





Atomic Number: 55

Atomic Weight: 132.9054519

Melting Point: 301.59 K (28.44°C or 83.19°F)

Boiling Point: 944 K (671°C or 1240°F)

Density: 1.93 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Zircalloy is not the only reactive metal present in nuclear fuel rods. At least one of the fission products is a highly reactive metal also.

2 Responses to “The Fires in Spent Fuel Pool Number 4, Fukushima-Diiachi”

  1. puameliaclinic Says:

    Reblogged this on The Pua Melia Clinic and commented:
    Apparently there WERE fires at the SFPs. So it seems likely that the radiation may already be up in the atmosphere!

  2. CaptD Says:

    Great article – Salute

    I believe that time will show the Tsunami did far more damage than the Nuclear Industry has talked about, especially since TEPCO has had so long to fiddle with all the data in order to cover their tracks!

Comments are closed.