Japanese Earthquake, Tsunami, and Nuclear Reactors

[mot]

Website collating misinformed, misleading and sensationalising journalism regarding the Great Tohoku Earthquake and the situation regarding Fukushima Nuclear Power Plant.
http://jpquake.wikispaces.com/Journalist+Wall+of+Shame

We're so lucky and thus grateful to have doris with us here in GS!

ETA: Olympia, I saw the press conference by some fire fighters from Tokyo on TV, after their first operation at the plant - one of them said when he'd text his wife to tell her that he'd volunteered, she had simply replied 'be a saviour of Japan'.

[dorispulaski]

mot, thank you,

And more thanks to the firefighters and the TEPCO employees who are working so many hard hours in such difficult, difficult conditions.

It really boggles the mind that people would go to tertiary news sources to compile something when the primary sources (TEPCO) and secondary sources (IAEA, NEI, JAIF) are on line.

[let`s talk]

http://www.npr.org/blogs/health/2011...?ps=sh_topprev
http://metropolis.co.jp/quake/quake-...iation-levels/

[dorispulaski]

The IAEA details what is being done to help & organize activities.

Working Together to Support Japan and the Global Communityby International Atomic Energy Agency (IAEA) on Wednesday, March 23, 2011 at 10:00am
Rome, Vienna, Geneva, 23 March 2011



The Food and Agriculture Organization (FAO), the International Atomic Energy Agency (IAEA) and the World Health Organization (WHO) are working closely in support of the Japanese government's on-going efforts to address food safety issues stemming from the events of 11 March 2011.



FAO Director General Jacques Diouf, IAEA Director General Yukiya Amano and WHO Director General Margaret Chan jointly issued the following statement:



Joint FAO-IAEA-WHO Statement on

Food Safety Issues following the Fukushima Daiichi Nuclear Emergency

FAO, IAEA and WHO are committed to mobilizing their knowledge and expertise in support of the Japanese government's on-going efforts to address food safety issues stemming from the events of 11 March.

Additional information on the food safety dimension of events in Japan is contained in a set of questions and answered developed jointly by FAO, IAEA and WHO. (http://www.who.int/hac/crises/jpn/faqs/en/index7.html)



Since the events of 11 March, thousands of lives have been lost, and many homes and buildings have been damaged or destroyed by the earthquake and tsunami. Japan's transportation infrastructure has also suffered, and cropland and aquaculture installations have been degraded or wiped out.

In this situation, damage to the reactors of a nuclear power plant, the resulting risk of direct human exposure to radiation, and efforts to bring the involved installations under control have also received priority attention.

Food safety issues are an additional dimension of the emergency. Some food products sampled at sites both within the Fukushima Prefecture and in adjacent areas have been contaminated by radioactive materials.

Japan has regulations in place relating to provisional regulatory limits of radioactivity in food. Food monitoring is being implemented, measurements of radionuclide concentrations in food are taking place, and the results are being communicated publicly. Japanese authorities are also giving advice to consumers and producers regarding safety measures.

[dorispulaski]

http://www.npr.org/blogs/health/2011...?ps=sh_topprev
http://metropolis.co.jp/quake/quake-...iation-levels/

Yes, Radioactive milk only being a danger after 58,000 glasses makes a very clear, anti-alarmist point.

[dorispulaski]

Nei

update as of 11:00 a.m. Edt, march 23:
Workers continued efforts on wednesday to restore offsite power to six reactors at the fukushima daiichi nuclear power plant. External power was available wednesday at reactors 2, 3, 5 and 6, the japan atomic industrial forum said, but has not yet been re-established to reactor safety systems.

The next step before fully connecting external power is to test and repair the equipment that it will power. Cooling pumps for reactors 1 and 2 were covered by seawater and will require maintenance to bring them online. Tokyo electric power co. Is testing the cooling water pumps for reactor 3. External power was connected to the main control room at reactor 3 on tuesday.

Reactors 5 and 6, which were shut down for maintenance at the time of the earthquake, are in safe shutdown.

"the earthquake and tsunami may have inflicted considerable damage in addition to knocking out electricity supplies," the international atomic energy agency said. "since the extent of this damage (and therefore the extent of necessary repair) is unknown, it is not possible to accurately estimate a work schedule."

japanese authorities have detected high levels of radioactive cesium 137 in soil about 40 kilometers northwest of the fukushima plant. Surveys of radioactive substances in soil at six locations found levels of cesium 137 that are 1,600 times typical for that area. Japan's government is expanding offshore monitoring for radioactive nuclides to 30 kilometers.

Japanese authorities have advised tokyo residents not to provide municipal drinking water to infants or use it in mixing powdered milk for infants because of abnormal levels of radioactive iodine (i-131) detected in the drinking water. One water sample (5,700 picocuries per liter) indicated approximately twice the japanese government guideline and prompted the restriction for infants. In an emergency in the united states, state and local officials would closely monitor food and drinking water supplies and quarantine any contaminated supplies as needed to prevent public exposure. U.s. Officials use pre-established guidelines for safe consumption of food and water set by the u.s. Food and drug administration.

The u.s. Department of energy has released the first radiation data from its aerial monitoring system and ground detectors in japan. The department will update the data regularly. For the latest information, click here.

[Olympia]

Website collating misinformed, misleading and sensationalising journalism regarding the Great Tohoku Earthquake and the situation regarding Fukushima Nuclear Power Plant.
http://jpquake.wikispaces.com/Journalist+Wall+of+Shame

We're so lucky and thus grateful to have doris with us here in GS!

ETA: Olympia, I saw the press conference by some fire fighters from Tokyo on TV, after their first operation at the plant - one of them said when he'd text his wife to tell her that he'd volunteered, she had simply replied 'be a saviour of Japan'.

I sure agree with you about Doris! She's been a great resource in the past few weeks.

That's an amazing quote about the firefighter's wife. And that's what those folks are doing--no less than saving their country.

[dorispulaski]

TEPCO has their status for March 24th at 7 AM and an earlier status from March 23rd at 11 PM:

Changes are that

Unit 3

At around 4:20 pm on March 23rd, our staff confirmed light black smoke belching from the Unit 3 building. At approximately 11:30 pm on March 23rd and 4:50 am on March 24th, our employee found no signs of smoke.

And at the Unit 3 spent fuel pool

Today's work for cooling the spent fuel pools -At approximately 10:00 am on March 23rd, we started spraying water to Unit 4 using the concrete pumping vehicle and completed at around 1:00 pm. And at around 11:00 am, sea water injection to fuel spent pool of
unit 3 was started by using Fuel Pool Cooling and Filtering(clean up) system (FPC) and finished at around 1:20 pm.

Then later on March 24th, following seeing the smoke

-At approximately 5:35 am , we started injecting seawater into the fuel spent pool of Unit 3, using Fuel Pool Cooling and Filtering(clean up) system (FPC). -We are considering further spraying at other units and others subject
to the conditions of spent fuel pools.

Unit 5

At around 5:24 pm on March 23rd, when we switched the temporary Residual Heat Removal System Seawater Pump, it automatically stopped. We will repair the pump and maintain the reactor water level and the temperature in the reactor properly.

http://www.tepco.co.jp/en/press/corp...s/110323e6.pdf

There's a graph of TEPCO's measurements of seawater (above)

They took measurements at the plant's north discharge canal, south discharge canal, and at the Iwasawa Coast.

They checked for and found Iodine 131, Iodine 132, Cesium 134, Cesium 136, Cesium 137 and Cobalt 58 at the south discharge canal.

They checked for and found Iodine 131 (1.158 becquerel/cubic centimater), Cesium 134 (0.0463 becquerel/cubic centimeter), Cesium 137 (0.03962 becquerel/cubic centimeter) and Cobalt 58 at the north discharge canal. Iodine 132 and Cesium 136 were below the level of detection.

At the Iwasawa coast, they checked for and found Iodine 131 (0.66 becquerel/cubic centimeter), Cesium 134 (0.0393 becquerel / cubic centimeter), and Cesium 137 (0.046 becquerel /cubic centimeter). Iodine 132, Cesium 136, and Cobalt 58 were below the level of detection.

They also have information about radionuclides in the air around the Daini plant 10 km. from Daiichi for March 22:
In the most recent measurement they found Iodine 131 (0.00239 becquerels/cubic centimeter), Cesium 134 (0.0000151 becquerels / cubic centimeter) , Cesium 137 (0.0000189 becquerels /cubic centimeter), and tellurium 132 0.0000668 becquerels/cubic centimeter)

They report they found Cesium 134, Iodine 131, and Tellurium at Daiichi in the air, but I don't have the dose numbers.

[dorispulaski]

JAIF has their NHK report

Status of Fukushima Daiichi nuclear power station as of 12:00, March 24, 2011
Here is information regarding the status of Fukushima Daiichi nuclear power station from the news reports aired by NHK in this morning of March 24.

�� Water is being injected to the reactor vessel at Unit-1, given the situation that the pressure is high inside the reactor pressure vessel. TEPCO decided to decrease injection volume based on its analysis that pressure inside the containment vessel increased as a result of increasing injection volume to the reactor vessel. Core cooling function has been enhanced at Unit-1 since March 23 after the core temperature exceeded design value of 302℃ and reached almost 400℃. (11:30, March 24)

�� All works at Unit-1, 2, 3 and 4 were suspended after black smoke rose from unit-3. TEPCO resumed water injection to the spent fuel pool of Unit-3 after 05:30 on March 24 after calming down the situation. (10:06, March 24)

�� Steam like substance rose from all unit-1, 2, 3 and 4 were observed from NHK’s helicopter. This is the first time that steam like substance rose from Unit-1. (09:30, March 24)
End

JAIF's status says the following:

The Main Gate: 212.8 μSv/h at 06:00, Mar. 24

They comment on the seawater measurements

Monitoring results of seawater sampled at coasts in the surrounding area of the station within about 16km from the Fukushima Dai-ichi NPS in Mar. 22nd showed that radioactive Iodine, I-131, exceeding the regulatory limit and Cesium, Cs-134, 137, less than the regulatory limit were detected.

Something like steam was seen rising from the reactor building of Unit 1through 4 (as of 7:00, Mar. 24). High-dose rate was measured in Unit 2 turbine building.

Work to recover external AC power is in progress.
External AC power has reached to Unit 2.
External AC power is to be recovered on 24th in Unit 2 and by 26th in Unit 1, which is to receive the power from Unit 2. Integrity check of electric equipment is going on in both units.

The NEI reports that at 7:00 PM EDT on March 23rd

Fukushima Daiichi
Smoke seen coming from the reactor building at reactor 3 at 4:20 p.m. on Wednesday (Japan time) "decreased significantly," the International Atomic Energy Agency said. On Wednesday, smoke from reactor 3 caused the temporary evacuation of workers from reactors 3 and 4.

Efforts are continuing to restore off-site electricity at reactors 1, 2, 3 and 4.

As reported earlier here, seawater injection continues to cool reactors 1, 2 and 3. Seawater is being sprayed into the reactor 3 spent fuel pool. Crews continued to use a truck to deliver high volumes of water into the spent fuel pool at reactor 4, IAEA said.

They also report the the US's Nuclear Regulatory Commission is going through exercises to review lessons learned from Daiichi and the Japanese Tsunami & Earthquake in general.

[dorispulaski]

And the IAEA says about the same things as TEPCO and JAIF and NEI.

Fukushima Daiichi Nuclear Accident Update (23 March, 20:00 UTC)
Brief update on state of Fukushima Daiichi reactors

Japanese authorities today announced a number of developments at Fukushima Daiichi nuclear power plant, where reactor cooling systems were disabled following the massive earthquake and tsunami on 11 March.

At Units 1, 2, 3, and 4, workers have advanced the restoration of off-site electricity, and the lights are working in Unit 3's main control room.

Black smoke was seen emerging from the Unit 3 reactor building, spurring the temporary evacuation of workers from Units 3 and 4. The emission of smoke has now decreased significantly.

Crews continued today to use a concrete pump truck to deliver high volumes of water into the Unit 4 spent fuel pool, where there are concerns of inadequate water coverage over the fuel assemblies.

At Units 5 and 6, workers have successfully restored off-site power to the reactor, which had previously reached a safe, cold shutdown status.

Going through today's radiation readings at the Main gate at Daiichi and at Daina, the incident with the black smoke did not cause any jump in radioactivity, as did the event on the previous day.

Another earlier NHK report that I didn't post, translated by JAIF confirms that:

Status of Fukushima Daiichi nuclear power station as of 21:00, March 23,
2011
Here is information regarding the status of Fukushima Daiichi nuclear power
station from the news reports aired by NHK in this afternoon and evening of
March 23.

 Persons who were working to carry out test run of pumps, which are to inject
water into the reactor at Unit-3, were evacuated after black smoke rose and
the test run was suspended around 16:00. (19:05, March 23)

 TEPCO Fukushima office announced at the press briefing held at 17:30 that
black smoke rose from unit-3 around 16:20, and then it was gradually calmed
down as of 17:10. Radiation detected surrounding the power plant has not
changed. (18:05, March 23)

 Tokyo Fire Department was going to spray water to unit-3 from 16:30.
However, this operation was suspended concerning safety after black smoke
rose. (17:50, March 23)

 The operation of water injection to the spent fuel pool of Unit-4 with special
vehicle was finished around 13:00 after 3 hour operation. (14:15, March 23)
End

[dorispulaski]

JAIF has come out with their morning status, but in reformatting the chart, some things have become less clear-like whch wording goes with which Reactor or Spent Fuel pool. Here's what I get out of it

JAIF status, March 24th

Latest Major Incidents and actions

<March 23rd>
02:33 Feed Water Line was added to the Fire Extinguish Line to inject water into the Reactor Pressure Vessel in Unit 1.
also *Temperature in the reactor pressure vessel has been gradually dropping since March 23rd. (225 C at 9:00 am March 24th).

16:20 Black smoke erupted from Unit 3 (smoke settle around 23:30)
* from TEPCO monitoring data, no jumps in radiation measurements occurred this time)

17:24 Residual Heat Removal pump stopped automatically as the primary power supply [and was] replaced with the temporary power source.
Backup pump is to become in service on 24th.

<March 24th>
05:35 Water injection to Spent Fuel Pool via reactor water clean up system started
*it's not clear which pool from the chart.

Radiation at the Daiichi Main Gate: 209.4 μSv/h at 12:00, Mar. 24. Radiation at Daini is down to 10.0 μSv/h

Unit 1
Lighting has been recovered in the Unit 1 main control room.

*I think Unit 2 & 3 also have lights in the main control room now, but it's not clear from the chart.

[dorispulaski]

TEPCO has issued a number of status reports.

Contract workers are back on the job, and it sounds like there might be a lot more people on site. There have been some new injuries. It must be remembered that Daiichi now looks like a war zone of wreckage. It is obviously very difficult working conditions.

Two workers were transferred to the hospital, after stepping in radioactive water in the turbine building. The actual dose they received from doing this will determine how serious injuries to them are. The file linked by let's talk listed the figure for radiation burns as 400mS/hour. TEPCO says more than 170 mS/hour. I hope the best for the injured workers.

Injuries:

-At approximately 10 pm on March 22nd, 1 worker who had been working on
setting up a temporary power panel in the common pool was injured and
transported to Fukushima Daini Nuclear Power Station where the industrial
doctor is.
-At approximately 1 am on March 23rd, 1 worker who had been working on
transporting a temporary power panel in the common pool was injured and
transported to Fukushima Daini Nuclear Power Station where the industrial
doctor is.
-On March 24th, it was confirmed that 3 workers from other companies who
were in charge of cable laying work in the 1st floor and the underground
floor of turbine building were exposed to the radiation dose of more than
170 mSv. 2 out of 3 are being transferred to the hospital as it was
confirmed that their leg skin were contaminated. They were transferred to
FUKUSHIMA Medical University Hospital.

Unit 5

Yesterday, the pump broke, today it's fixed.

At around 4:14 pm, March 14th, we started replaced pump and at around 4:35 pm, cooling of reactor has restarted

Additonally
Spent Fuel Pool Activities
(for some time JAIF has considered the spent fuel pools at Daiichi to be the most criticial items on site at Daiichi.

Today's work for cooling the spent fuel pools
-At approximately 5:35 am, we started injecting seawater into the fuel
spent pool of Unit 3, using Fuel Pool Cooling and Filtering(clean up)
system (FPC) and finished at 4:05 pm.
-At around 2:35 pm, spraying to unit 4 by concrete pump track and finished
at around 5:30 pm.
-We are considering further spraying at other units and others subject to
the conditions of spent fuel pools.

-At 3:37 pm, March 24th, electricity supply to common spent fuel pool has started from external power.

And TEPCO reminds us that they have other power issues than Daiichi

We are announcing the status of major inspections and restoration works and nonconformances at TEPCO's Kashiwazaki-Kariwa Nuclear Power Station after the Niigata-Chuetsu-Oki Earthquake.

[dorispulaski]

JAIF and TEPCO have issued their usual late night updates for March 24th (Japanese time)

We learn that the upper bound of the radiation dose received by the injured workmen transferred to Fukushima Hospital was 180 milleSievert/hour.

Tokyo has a shortage of bottled water, due to the announcement that babies should not be given tap water. However, today, the concentrations of radionuclides in Tokyo tap water returned to normal.

Meanwhile, people in China have bought up all the iodized salt to be had, as ad hoc Iodine pills. Chinese customers of a US manufacturer who is a friend of mine have been requesting salt to be sent in orders.

And in Groton, CT, my home, people are still going to the Town Clerk to stock up on Iodine pills (You can get them at town hall for free, since Groton is within 5 miles of Millstone Point, and the US Submarine Base)

TEPCO

Radiation at Daiichi Main Gate continues to drop slowly

March 24, 11:50 PM 199.6 microSievert/Hour

Radiation at Daina Measuring Point four continues to drop slowly

March 24, 11:50 PM 9.3 microSievert/Hour

JAIF UPDATE as of 11:00 PM March 24

<March 24th>
05:35 Water injection to SFP via reactor water clean up system started in Unit 3.
Around 11:30 Lighting has been recovered at Unit 1 Main Control Room.
16:14 Residual Heat Removal pump of Unit 5, which had stopped automatically, was restarted and then the system was put into shutdown cooling mode.

JAIF translation of NHK report of March 24, 2011at 21:00

Status of Fukushima Daiichi nuclear power station as of 21:00, March 24,
2011
Here is information regarding the status of Fukushima Daiichi nuclear power
station from the news reports aired by NHK in this afternoon and evening of
March 24.
l The 2 workers sent to the hospital are suspected to get burned by beta-ray. 3
workers were working to lay electrical cables at the first basement level
when they were exposed. To secure safety of workers under high radiation
environment becomes an issue. (19:25, March 24)
l Nuclear and Industrial Safety Agency announced that 3 persons who were
exposed to radiation. These were working in the turbine building of unit-3 at
that time. The amount of radiation that they were exposed is from 170mSv/hr
to 180mSv/hr. It is found that radionuclide adheres to foot skin of 2 workers
and these 2 workers were sent to the hospital for cure. (15:50, March 24)
l The work to recover external AC power for units-1, 2, 3 and 4 is in progress.
External AC power to the main control room of unit-1 became available at
11:30 of today. Now the lights are working in the main control room at unit1
and 3. (13:20, March 24)
End

[dorispulaski]

NEI has its afternoon updates:

Things that JAIF, NHK and TEPCO haven't mentioned are in bold.

UPDATE AS OF 1:30 P.M. EDT, MARCH 24
In a sign of progress, Tokyo Electric Power Co. (TEPCO) is working to switch from seawater to borated freshwater to cool uranium fuel at three reactors at the Fukushima Daiichi nuclear power plant.

All reactors now have access to off-site power, and work is under way to inspect, repair and connect equipment needed to cool the reactors. Testing by TEPCO indicates that many pumps are inoperable because of flood damage.

Restoring regular cooling to the used fuel pools at Fukushima Daiichi remains a high priority. The used fuel pools at reactors 5 and 6 are being cooled using heat removal systems with electric power. Workers continue to spray seawater on the reactor buildings and spent fuel pools at reactors 1, 3 and 4. Cooling water to the spent fuel pool at reactor 2 is being supplied by a fire hose connection.

Overnight, steam was rising from the secondary containment buildings that house reactors 1 through 4.

Radiation dose rates at the site boundary range from 1 to 3 millirem per hour.

NEI has updated the brochure "Understanding Radiation: Its Effects and Benefits," which includes facts about monitoring and protection against radiation.


UPDATE AS OF 9:30 A.M. EDT, MARCH 24:
Two workers were hospitalized for radiation exposure Thursday, even as Tokyo Electric Power continued to make progress in stabilizing reactors at the Fukushima Daiichi nuclear power plant.

Three workers received radiation exposure of 17 to 18 rem from standing in contaminated water while laying cable in the reactor 3 turbine building, TEPCO said. One of the workers did not require hospitalization. The exposures were less than the 25 rem emergency dose limit established by the Japanese government.

External electric power was restored to reactor 1 and lights were on in the control room. Lighting was restored to the reactor 3 control room Wednesday. Electric power also has been connected to some of the instruments in all reactors except unit 3. While external electricity is available at all six units, it is not in wide use as workers inspect and repair cooling equipment before it can be energized. Reactors 5 and 6 have been safely shut down with cooling systems running on offsite power.

Seawater is being injected to cool the cores of reactors 1, 2 and 3. Workers continue to spray water into the spent fuel pools of reactors 3 and 4.

In Tokyo, the level of radioactive iodine in tap water has dropped to within safety limits Thursday. Yesterday, the Japanese government had advised against giving tap water to infants under one year old.

You will notice that guidelines for an emergency for those workers were not exceeded. You would have thought from the way this was reported on TV that these guys were going to die immediately of radiation poisoning.

I suppose this is why NEI has updated its brochure on Understanding Radiation & given a link to it.

http://www.nei.org/filefolder/Unders...adiation_1.pdf

Page 7 on putting Radiation dose in context is useful:

ACTIVITY ANNUAL DOSE

Smoke detector in the home 0.008 millirem

Living within 50 miles of a nuclear power plant 0.009 millirem

Living within 50 miles of a coalfired power plant* 0.03 millirem

Roundtrip flight from New York City to Los Angeles 5.0 millirem

Medical X-ray 10.0 millirem

Food and water consumed throughout the course of one year 30 millirem

Mammogram 100 millirem

Average annual exposure for a nuclear power plant worker 120 millirem

Average annual exposure from natural radiation 300 millirem

CT scan 1000 millirem

NRC’s annual limit for occupational exposure 5000 millirem

Cardiac catheterization or coronary angiogram 5,000 millirem

For more context, fall of 2009, Mr. Ski was very, very sick.

He had 7 catherizations (35,000 millirem) in interventional radiology and 1 CT (1,000 millirem) scan. He had a chest x ray (10 millirem) on being admitted to the hospital.

1 rem is 1000 millirem, so Mr. Ski had more exposure to radiation (36 rem, in addition to his annual exposure) than the guys in the hospital. He had no radiation burns, and is alive and well.

[dorispulaski]

On the other hand, the IAEA report contradicts this, and says they may have burns on their feet. IAEA is seeking more information. I hope we actually hear how they are doing.:

Fukushima Daiichi Nuclear Accident Update (24 March 17:25 UTC)
Japanese Workers Treated for Radiation Exposure

Japanese authorities today reported that three workers at the Fukushima Daiichi nuclear power plant were exposed to elevated levels of radiation. The three were working in the turbine building of reactor Unit 3 and have received a radiation dose in the range of 170-180 millisieverts.

Two of the workers have been hospitalized for treatment of severely contaminated feet, which may have suffered radiation burns. The workers had been working for about three hours in contact with contaminated water.

The IAEA is seeking additional information.

IAEA got the saltwater data we saw yesterday.

Fukushima Daiichi Nuclear Accident Update (24 March, 17:30 UTC)
Japanese Seawater Samples Show Signs of Radioactive Materials

Japanese authorities today provided the IAEA with data on seawater samples they collected on 22 and 23 March, after detecting iodine and cesium in the water near the Fukushima Daiichi nuclear power plant. (See earlier update.)

A vessel from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) collected water samples at several points 30 kilometres from the coastline and found measurable concentrations of iodine-131 and cesium-137. The iodine concentrations were at or above Japanese regulatory limits, and the cesium levels were well below those limits.

The IAEA's Marine Environmental Laboratory in Monaco has received the data for review.

And has more information on the very interesting (to me) subject of Japanese Spent Fuel pools:

Fukushima Daiichi Nuclear Accident Update (24 March 14:00 UTC)
Spent Fuel Pools at Fukushima Daiichi Nuclear Power Plant - Updated

Spent fuel removed from a nuclear reactor is highly radioactive and generates heat. This irradiated fuel needs to be stored for one to three years in pools that cool the fuel, shield the radioactivity, and keep the fuel in the proper position to avoid fission reactions. If the cooling is lost, the water can boil and fuel rods can be exposed to the air, possibly leading to severe damage and a large release of radioactive materials.

Nuclear power plants must replace fuel every one to two years, and the Fukushima Daiichi reactors typically remove about 25 percent of the reactor's fuel -- to be replaced with fresh, or unirradiated, fuel -- during each refuelling outage. The spent fuel, which is hottest immediately after it is removed from the reactor, is placed in the spent fuel pool until it is cool enough to be moved to longer-term storage.

The concern about the spent fuel pools at Fukushima Daiichi is that the capability to cool the pools has been compromised. See diagram below for location of the pool in each reactor building.

http://www.iaea.org/newscenter/image...l-pool-820.jpg

(Hint: the spent fuel pool is on the upper story)

A Running Status of the Spent Fuel pools & their problems, according to IAEA:

Unit 1

Unit 1 experienced an explosion on 12 March that destroyed the outer shell of the building's upper floors. No precise information has been available on the status of the spent fuel pool.

Unit 2

Precise information on the status of the spent fuel pool was unavailable in the days following the earthquake, but Japan's Nuclear and Industrial Safety Agency began to release temperature data on 20 March:
20 March, 23:00 UTC: 49 °C
21 March, 05:25 UTC: 50 °C
21 March, 21:20 UTC: 51 °C
22 March, 02:20 UTC: 53 °C
22 March, 06:30 UTC: 50 °C
22 March, 19:20 UTC: 51 °C
23 March, 00:00 UTC: 51 °C
23 March, 06:00 UTC: 51 °C
23 March, 16:00 UTC: 52 °C
24 March, 00:00 UTC: 47 °C

Workers conducted an operation to spray 40 tonnes of seawater to the spent fuel pool on 20 March, and they added another 18 tonnes on 22 March.

Unit 3

Unit 3 experienced an explosion on 14 March that destroyed the outer shell of the building's upper floors. The blast may have damaged the primary containment vessel and the spent fuel pool. To address these concerns, authorities began spraying water into the building, first by helicopter on 17 March and then by fire trucks and other vehicles through 22 March. Starting 23 March, seawater was injected into the spent fuel using the cooling and purification line. By midday 24 March, 4-5 tonnes of seawater had been injected through this line.

Unit 4

This reactor was shut down 30 November 2010 for routine maintenance, and all the fuel assemblies were transferred from the reactor to the spent fuel pool, before the 11 March earthquake. The heat load in this pool is therefore larger than the others.

On 14 March, the building's upper floors were severely damaged, possibly causing a reduction of cooling capability in the spent fuel pool. Emergency workers began spraying water into the building on 20 March, and have continued daily since then. On 22 March, workers began using a concrete pump truck that can deliver water more effectively, placing 150 tonnes of water on 22 March and 130 tonnes on 23 March.

Units 5 and 6

Instrumentation at these reactors began to indicate rising temperatures at their spent fuel pools starting on 14 March. Three days later, Japanese technicians successfully started an emergency diesel generator at Unit 6, which they used to provide power to basic cooling and fresh-water replenishment systems. Workers created holes in the rooftops of both buildings to prevent any hydrogen accumulation, which is suspected of causing earlier explosions at Units 1 and 3.

A second diesel generator came online on 18 March, and the next day, the higher-capability Residual Heat Removal (RHR) system recovered full function. External power was restored to Units 5 and 6 on 22 March. Temperatures in the spent fuel pools of Units 5 and 6 have gradually returned to significantly lower temperatures, although the Unit 5 pool temperature increased somewhat on 23 March after pumps for the RHR system were stopped when the diesel generators were removed from service.

Common Use Spent Fuel Pool

In addition to pools in each of the plant's reactor buildings, there is another facility -- the Common Use Spent Fuel Pool -- where spent fuel is stored after cooling at least 18 months in the reactor buildings. This fuel is much cooler than the assemblies stored in the reactor buildings. Japanese authorities confirmed as of 18 March that fuel assemblies there were fully covered by water, and the temperature was 57 °C as of 20 March, 00:00 UTC. Workers sprayed water over the pool on 21 March for nearly five hours, and the temperature on 23 March was reported to be 57 °C.

IAEA also has replicated a version of the JAIF block diagram status of the Daiichi reactors:

http://www.slideshare.net/iaea/table...-march0600-utc

And other slide shows at

http://www.slideshare.net/iaea/techn...-23-march-2011

Including modelling of the path the contamination from the plant took. It shows most everything on the 17th and 18th went out to sea.. The modelling was done by a group in Montreal.