The Fires in Spent Fuel Pool Number 4, Fukushima-Diiachi
The Japan Atomic Industry Forum at http://www.jaif.or.jp/english/fukushima/plantstatus201103.html 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.
[b]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.”[/b]...
...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....
(of course you can trust TEPCO now can't you)
[b][i][u]As of 4 p.m. today, when fire had been seen in the pool at reactor #4, [/u][/i][/b] a fact sheet dated yesterday from the Nuclear Energy Institute (NEI), which represents the nuclear industry, commented that:
There has been some speculation that, if the used fuel pool were completely drained, the zirconium cladding might ignite and a "zirconium fire" might occur. Studies performed by the Department of Energy indicate that it is virtually impossible to ignite zirconium tubing.
Since zirconium is presumably what was burning in the pools, ScienceInsider asked NEI for a reference to those studies. Spokesperson Steve Kerekes wrote in an e-mail response:
Just today we were made aware of additional analysis that leads us to amend that view. Without getting into the details of how or when, we acknowledge the potential in certain circumstances and should by now have changed the fact sheet you reference.
[b][i]Apologies[/i][/b] for not properly reflecting the latest scientific research in this area.
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, [b][i][u]and now a fire in spent fuel at reactor number four[/u][/i][/b]; 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.
[b][i][u]However the report from the ABC defines what was “on fire”. It was the fuel rods.[/u][/i][/b]
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
By JAMES GLANZ and WILLIAM J. BROAD
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.
…[b][i][u].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.”[/u][/i][/b]
[b][i][u]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.[/u][/i][/b]
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
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.
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. http://www.stripes.com/news/up-to-the-minute-1.137684
“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 [b][i][u]and a fourth caught fire in a dramatic escalation of the 4-day-old catastrophe.[/u][/i][/b] 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
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 : http://www.iaea.org/newscenter/news/2011/fukushima150311.html
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. [b][i][u]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.[/u][/i][/b] The next day the IAEA Fukushima Nuclear Accident Update report for 16 March 2011 at http://www.iaea.org/newscenter/news/2011/fukushima160311.html
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, http://www.youtube.com/watch?v=zWVEhjl53I8:
“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.
[b][i][u]“The latest blaze happened early Wednesday morning, local time, in the number 4 unit.[/u][/i][/b]
“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.
[b][i][u]“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.[/u][/i][/b]
“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.
Wikipedia at http://en.wikipedia.org/wiki/Fukushima_Daiichi_units_4,_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. 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. 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. 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. TEPCO said workers extinguished the fire by 12:00. As radiation levels rose, some of the employees still at the plant were evacuated. 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. Edano said there was no continued release of “high radiation”.
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. At 17:48 it was reported that water in the spent fuel pool might be boiling. By 21:13 on 15 March, radiation inside the Unit 4 control room prevented workers from staying there permanently. Seventy staff remained at the plant, while 800 had been evacuated. By 22:30, TEPCO was reportedly unable to pour water into the spent fuel pool. By 22:50, the company was considering using helicopters to drop water, but this was postponed because of concerns over safety and effectiveness, and the use of high-pressure fire hoses was considered instead.
[b][i][u]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.[/u][/i][/b] 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. At 11:57, TEPCO released a photograph showing “a large portion of the building’s outer wall has collapsed”. Technicians considered spraying boric acid on the building from a helicopter.” The source links to the piece are interesting.
[b][i][u]The International Atomic Energy Agency did confirm that the fire had taken place in the used fuel storage pool. [/u][/i][/b]
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.
(link at source)
http://edition.cnn.com/2011/WORLD/asiapcf/03/14/japan.nuclear.reactors/index.html?hpt=T1 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, [b][i][u]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.[/u][/i][/b]
The Fires in Spent Fuel Pool Number 4, Fukushima-Diiachi
Posted on April 18, 2013 by puameliaclinic
Reblogged from Paul Langley's Nuclear History Blog:
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The Japan Atomic Industry Forum at http://www.jaif.or.jp/english/fukushima/plantstatus201103.html 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.