Japanese Earthquake, Tsunami, and Nuclear Reactors

[dorispulaski]

The NEI organization seems to have a few more details. This was posted 3 hours ago. Somehow, TEPCO is keeping the water level up in Units 1 & 2 today. No specific info on Unit 3 here.

UPDATE AS OF 9:00 P.M. EDT, TUESDAY, MARCH 15:
At 5:45 am, March 16, Japan Standard Time (4:45 pm EDT, March 15), a fire reignited at Tokyo Electric Power Co.'s Fukushima Daiichi 4 reactor. The fire was extinguished after about two hours, TEPCO said.

TEPCO was planning to battle the fire and provide additional water to cool used nuclear fuel with water dumped from helicopters, but abandoned the plan because a hole in the building's roof is not in close proximity of the used fuel pool.

The company may remove some panels from the top of the reactor containment buildings at reactors 5 and 6 in order to avert a possible buildup of hydrogen in the reactors. Hydrogen buildup caused explosions at reactors 1 and 3.

All of the fuel rods had been moved from reactor 4 to the spent fuel pool due to the maintenance work. About one-third of the fuel rods in reactors 5 and 6 had been removed as part of maintenance and refueling activities.

Seventy percent of the fuel rods Unit 1 and one-third in Unit 2 have been damaged, TEPCO said. The cooling water level in both units is being maintained.

Weather reports indicate that the wind at the Fukushima plant has shifted and is now blowing out to the Pacific.

An earthquake registering 6.1 on the Richter scale struck the Eastern Honshu region of Japan. Hamaoka nuclear plant, about 100 kilometers (62 miles) from the epicenter, continues to operate normally.

May the wind keep blowing over the Pacific.

[blue dog]

What I'm seeing after the Japanese disaster is that people are NATURALLY good. We are not born evil. There have been no cases of looting or price gouging in Japan. Also, China, long to have a history of not liking Japan after the occupation was one of the first nations to send aid and soldiers to help find survivors. The Chinese were impressed with how the Japanese were conducting themselves!

http://www.npr.org/2011/03/15/134567...ost-earthquake

And, of course, miracles like this:

http://news.yahoo.com/s/time/2011031...fullworldyahoo

[treeloving]

Thank you so much doris and everybody for info regarding to the incident. In this kind of situation, it delight to see good nature and kindness of the people. I hope with all my heart that the situation will get better.

For anyone who following the nuclear situation you can also follow at Aljazeera live blog

http://blogs.aljazeera.net/live/asia...ency-live-blog

It update the current situation, easy to understand and not use hyperbole language compare to other international news agency.

Best wish to those who are affected and Japanese people. You are not alone.

[dorispulaski]

So far no updates on TEPCO, IAEA, or NEI today, since the 9 PM EDT update yesterday, and nothing new on the relatively reliable Twitters I'm following or in facebook.

The Daina reports, which used to have radiation info from that site (10 km from Daiichi), only report that all 4 reactors are successfully in cold shutdown, and that outside power is present.

At some point today, there will be an IAEA Daily briefing. When I see it, I'll post it here.

[let`s talk]

All 6 reactors were designed by General Electric in the first place. They should clean this mess up.

[dorispulaski]

TEPCO now has a couple of releases, mostly ones that cover events for which press releases were not posted yesterday. On TV here in the US, it was stated that now 70 workers are on site.

The daily status for 2PM Mar 16th, Tokyo time, which is a rollup of the last four days occurrences. There is some more info about the Daini reactors. And info about the larger problem with simply getting electric power returned to customers. The two radiation events at the boundary of the Daini plant on the 14th and 15th were likely due to events at Daiichi. :

[Nuclear Power Station]
Fukushima Daiichi Nuclear Power Station:

Units 1 to 3: shutdown due to earthquake
Units 4 to 6: outage due to regular inspection at the occurrence of
earthquake

*The national government has instructed to evacuate for those local
residents within 20km radius of the site periphery and to remain
indoors for those local residents within 30km radius of the site
periphery.

*Since the value of radioactive materials (iodine, etc) at the site
(outside) measured by monitoring car exceeded the ordinary level,
it was determined that a specific incident stipulated in article 15,
clause 1 occurred (Extraordinary increase of radiation dose at site
boundary).
- 4:17 pm, March 15th at the main gate of the site
- 11:05 pm, March 15th at the main gate of the site

* Unit 1
The explosive sound and white smoke was confirmed near Unit 1 after
the big quake occurred at 3:36pm, March 12th. We have started sea
water injection at 8:20 pm and then boric acid into the reactor.

*Unit 2
At 1:25 pm, March 14th, since the Reactor Core Isolation Cooling System
has failed, it was determined that a specific incident stipulated in
article 15, clause 1 occurred (failure of reactor cooling function).
At 5:17 pm, while the water level in the reactor reached the top of the
fuel rod, we have restarted the water injection with the valve operation.
At approximately 6:14 am, March 15th, the extraordinary sound was
confirmed near the suppression chamber and the pressure inside the
chamber decreased afterwards. It was determined that there is a
possibility that something extraordinary happened in the suppression
chamber. While sea water injection to the reactor continued, TEPCO
employees and workers from other companies not in charge of injection
work started tentative evacuation to a safe location.
Sea water injection to the reactor is still under operation.

*Unit 3
At 6:50 am, March 14th, while water injection to the reactor was under
operation, the pressure in the reactor containment vessel increased to
530 kPa. As a result, at 7:44 am, it was determined that a specific
incident stipulated in article 15, clause 1 occurred (abnormal increase
of the pressure of reactor containment vessel). Afterwards, the pressure
has gradually decreased (as of 9:05 am, 450 kPa).

At approximately 11:01 am, March 14th, an explosion followed by white
smoke occurred near Unit 3. 4 TEPCO employees and 3 workers from other
companies (all of them are conscious) have sustained injuries and they
were already dispatched to the hospital by ambulances.

*Unit 4
At approximately 6:00 am, March 15th, an explosive sound occurred and
the damage in the 5th floor roof of Unit 4 reactor building was
confirmed. At 9:38 am, the fire near the north-west part of 4th floor
of Unit 4 reactor building was confirmed. At approximately 11:00 am,
TEPCO employee confirmed that the fire was off.

At approximately 5:45 am, a TEPCO employee discovered a fire at the
northwest corner of the Nuclear Reactor Building. TEPCO immediately
reported this incident to the fire department and the local government
and prepared to extinguish the fire. However, during an inspection at
approximately 6:15 am, TEPCO staff found no signs of fire.

Fukushima Daini Nuclear Power Station:
Units 1 to 4: shutdown due to earthquake
*The national government has instructed evacuation for those local
residents within 10km radius of the periphery.

*As the radiation dose at the site boundary exceeded the limitation,
it was determined that a specific incident stipulated in article 15,
clause 1 occurred (Extraordinary increase of radiation dose at site
boundary) at 9:58 pm, March 14th and at 0:00 am, March 15th.

*Reactor cooling function was restored and cooling of rectors was
conducted. As a result, all reactors achieved cold shutdown: Unit 1
at 5:00 pm, March 14th, Unit 2 at 6:00 pm, March 14th, Unit 3 at
0:15 pm, March 12th, Unit 4 at 7:15 am, March 15th.

* (Unit 1)
As it is confirmed that the temperature of the Emergency Equipment
Cooling Water System *1 has increased, at 3:20 pm, March 15th, we
stopped the Residual Heat Removal System (B) for the inspection.
Subsequently, failure was detected in the power supply facility
associated with the pumps of the Emergency Equipment Cooling Water
System. At 4:25 pm, March 15th, after replacing the power facility,
the pumps and the Residual Heat Removal System (B) have been
reactivated.

* (Unit 4)
As it is confirmed that the pressure at the outlet of the pumps of
the Emergency Equipment Cooling Water System*1 has been decreased,
at 8:05 pm, March 15th, we stopped the Residual Heat Removal System
(B) for the inspection. Subsequently, failure was detected in the
power supply facility associated with the pumps of the Emergency
Equipment Cooling Water System. At 9:25 pm, March 15th, after
replacing the relevant facility, the pumps and the Residual Heat
Removal System (B) have been reactivated.

*1:emergency water system in which cooling water (pure water) circulates
which exchanged the heat with sea water in order to cool down bearing
pumps and/or heat exchangers etc.

Kashiwazaki Kariwa Nuclear Power Station:
Units 1, 5, 6, 7: normal operation
Units 2 to 4: outage due to regular inspection

[Thermal Power Station]
Hirono Thermal Power Station Units 2 and 4: shutdown due to earthquake
Hitachinaka Thermal Power Station Unit 1: shutdown due to earthquake
Kashima Thermal Power Station Units 2, 3, 5, 6: shutdown due to earthquake
Ohi Thermal Power Station Unit 2: shutdown due to earthquake
Higashi-Ohgishima Thermal Power Station Unit 1: shutdown due to earthquake

[Hydro Power Station]
* All the stations have been restored.

[Transmission System, etc.]
All substation failed due to the earthquake have been restored.

[Blackout in TEPCO's Service Area]
Total of about 5,100 households are out of power.
Tokyo: 0
Kanagawa Pref.: 0
Tochigi Pref.: 0
Chiba Pref.: 0
Saitama Pref: 0
Gunma Pref.: 0
Ibaraki Pref:5,100
Yamanashi Pref: 0
Shizuoka Pref: 0 (east of Fuji River)

[Supply and Demand Status within TEPCO's Service Area to Secure Stable
Power Supply]
Backup supply from Shinshinano Conversion Station: 600MW
Backup supply from Sakuma Conversion Station: 300MW
Backup supply from Higashi Shimizu Conversion Station: 100MW
Backup supply from Kitahon Interconnection Facility: 600MW

Considering the critical balance of our power supply capacity and
expected power demand forward, in order to avoid unexpected blackout,
TEPCO has implemented rolling blackout (planned blackout alternates
from one area to another) since yesterday. We will make our utmost to
secure the stable power supply as early as possible.
For customers who will be subject to rolling blackout, please be
prepared for the announced blackout periods. Also for customers who
are not subject to blackouts, TEPCO appreciates your continuous
cooperation in reducing electricity usage by avoiding using unnecessary
lighting and electrical equipment.

[Others]
Please do NOT touch cut-off electric wires.
In order to prevent fire, please make sure to switch off the electric
appliances such as hair drier and to shut down the breaker of distribution
board when you leave your house.
For the customer who has in-house power generation, please secure fuel for
generator.

and more details about the fire at Unit 4:

At approximately 5:45 am, a TEPCO employee discovered a fire at
the northwest corner of the Nuclear Reactor Building while transporting
a battery to the central control room of Unit 4 of Fukushima Daiichi
Nuclear Power Station.
TEPCO immediately reported this incident to the fire department and
the local government. In addition, TEPCO also contacted related parties
about this incident and began immediate preparations to extinguish
the fire. (previously announced)

However, during an inspection at approximately 6:15 am, TEPCO staff found
no signs of fire. The area will be kept under strict surveillance.

And an older yet release on the incident that occurred at Unit 4, followed by the rise in radiation, followed by the evacuation of all but 50 workers:

At approximately 6:00 today, an abnormal noise began emanating from nearby
the pressure suppression chamber of Fukushima Dai-ichi Power Station.
Given that the pressure within this chamber had decreased, it was believed
that this was an indication that an abnormality had arisen. From this
point on, while water injection operations are still underway, the
temporary transfer to a safe place of TEPCO employees and workers from
other companies not directly involved with this work has begun. Currently,
at Fukushima Dai-ichi Power Station, the remaining workers are doing their
best to secure the safety and security of the site.

The parameters for Unit 2's nuclear containment vessel and the containment
vessel show no significant change.

We are aware of and sincerely apologize for the great distress and
inconvenience this incident has caused to not just those inhabitants
residing in the immediate vicinity but also society at large.

I missed this on youtube from yesterday:

IAEA Director General's Briefing from March 15th, discussing the fire in the spent fuel pool:
http://www.youtube.com/watch?v=yZB8Br3T2Sk

[janetfan]

All 6 reactors were designed by General Electric in the first place. They should clean this mess up.

So you are saying if I sell you a car and several years later you crash it into a house that I should come clean up your mess ?

[dorispulaski]

http://en.wikipedia.org/wiki/Fukushi...ar_Power_Plant

Fukushina Daiichi Units 1, 2 and 6 were supplied by GE.

Units 3 and 5 were supplied by Toshiba.

Unit 4 was supplied by Hitachi.

On site construction was done by Kajima for all units.

All the plants are managed by Tokyo Electric.

Daiichi Reactor 1 was built in 1967, and brought on line in 1971. Design by Ebasco.
Daiichi Reactor 2 was built in 1969, and brought on line in 1974. Design by Ebasco.
Daiichi Reactor 3 was built in 1970, and brought on line in 1976. Design by Toshiba.
Daiichi Reactor 4 was built in 1972, and brought on line in 1978. Design by Hitachi.
Daiichi Reactor 5 was built in 1973, and brought on line in 1978. Design by Toshiba.
Daiichi Reactor 6 was built in 1972, and brought on line in 1979. Design by Ebasco.

They were all relatively old, and had not been brought up to date as much as one would like, so the TV said.

[Olympia]

I read that the reactors were a kind called Mark 1, which has been criticized in recent years because in order to make a smaller and less expensive reactor, they used a smaller containment structure. The article I read (can't remember where) said that in all fairness, one can't know whether even a more massive containment structure could have withstood what happened on Friday. But there has been criticism of this style of reactor, and in the U.S., such reactors have received certain modifications and retro-fittings that may not have been performed on the ones in Japan.

Doris, please correct me if I've said anything inaccurate.

[dorispulaski]

Well, strictly speaking, the reactors, although not of current design and quite old, and not up to date in the way that US older reactors have been updated since Three Mile Island in 1979, did withstand the Level 9 earthquake and tsunami, including the containment structures.


What didn't withstand it was the diesel backup system, because it was planned for a tsunami height of 20 feet and experienced a wave height of 30 feet (peak to trough-I don't have the exact height for sure of the wave as it hit Daiichi-if anyone knows, I would like to know too).

In fact, this is an issue in some ways that the US has been dealing with since Sept. 11th-there used to be a great deal of checking, planning, regulation and so forth for the reactor part of nuclear plants, but not as much for the explicitly non-nuclear parts of the site (turbines, diesel generators, cooling structures, and such). Rules there were the same as they were for normal power plants. Since Sept. 11, these areas in the US have been upgraded, and subjected to much greater scrutiny, but perhaps not in Japan?

In any case, I wish the same scrutiny and regulation were done at normal power plants as well.

This letter was written today (not by me-a good friend forwarded it to me) Among other things it describes what went on in the US:

> Daniel E. O'Neill, Esq.
> Boeggeman George & Corde, P.C.
>
> 1 Water Street, Suite 425
>
> White Plains, New York 10601
>
>
>
> doneill@bgclawfirm.com <mailto:doneill@bgclawfirm.com>
>
> (914) 761-2252
>
> Fax (914) 761-5211
>
>
> ----------------------------Confidentiality
> Notice---------------------------
> This message is intended only for the individual or entity to which it
> is addressed and may contain information that is privileged,
> confidential and exempt from disclosure under applicable law. If you
> are not the intended recipient, or the agent responsible for delivering
> the message to the intended recipient, you are hereby notified that any
> dissemination, distribution or copying of this communication is strictly
> prohibited, and you are requested to please notify us by telephone,
> e-mail or fax, and return the original message to us at Boeggeman,
> George & Corde, P.C., with the above address. Although this message
> and any attachments are believed to be free of any virus or defect that
> might affect any computer system into which it is received and opened,
> it is the responsibility of the recipient to ensure that is virus free,
> and no responsibility is accepted by this firm for any loss or damage
> arising in any way.
>
>
>
>
>
>
>
> From: Arthur J. Kremer [mailto:kremer@area-alliance.org]
> Sent: Tuesday, March 15, 2011 8:22 PM
> To: NY A.R.E.A.
> Subject: Japan and New York's Nuclear Power Plants
>
>
>
> Dear New York AREA Member:
>
>
>
> As dramatic and relentless efforts continue to overcome the challenges
> facing three nuclear power plants in Japan, well-funded anti-nuclear
> activists are predictably using the disaster to again call for the
> closure of New York's nuclear energy facilities, notably Indian Point.
> This ill-advised action would be a serious mistake to New York's
> economy, environment, and even public health.
>
>
>
> The U.S. Nuclear Regulatory Commission has already thoroughly evaluated
> seismic issues at all U.S. nuclear power plants. In fact, every U.S.
> nuclear plant is designed to withstand the maximum projected earthquake
> in the geographic area of each site location.
>
>
>
> We should keep in mind that the Japanese earthquake, the fifth strongest
> in recorded history, is not what damaged the plant. Rather, it was the
> resulting tsunami, which swept away diesel fuel supplies for the back-up
> power generators and damaged water intake structures that were needed
> for the automatic plant shutdown relative to cooling systems. The
> Fukishima Daiichi plants were designed for a tidal wave up to a maximum
> of 22 feet high and not the 33 foot high wave that hit on Friday. The
> areas of New York where nuclear plants are situated do not, and in all
> likelihood cannot, experience similar tsunamis.
>
>
>
> In 2008, a panel of highly renowned, independent experts evaluated 64
> safety issues at Indian Point, including seismic design, and found the
> plant to be very safe. Under intense scrutiny, Indian Point continues to
> earn the highest safety ratings from the NRC.
>
>
>
> Furthermore, since 9-11, nuclear plants including Indian Point have been
> upgraded to factor for many scenarios, including a loss of back-up
> power. New practices, protocols and equipment have been employed since
> then to factor for the loss of back-up power at nuclear plants.
>
>
>
> To close New York's nuclear power plants, which provide 30 percent of
> the state's electricity, for even a few weeks would lead to serious
> degradation of electric system reliability and in fact create new
> dangers for the public. The resulting electricity price hikes, at a time
> when oil and gasoline prices are soaring, would be a one-two financial
> punch for hard working New Yorkers - including thousands of employees
> who work in the region. It would also lead to greater reliance on fossil
> fuels and higher pollution.
>
>
>
> Like you, our thoughts and prayers are with the people of Japan at this
> time of tragedy. There will be much to do to ensure the country recovers
> and that we learn many lessons from this disaster to better prepare and
> protect.
>
>
>
> As nuclear power issues will certainly now be prominently in the news
> for some time, we respectfully ask that you consider the facts and not
> be unduly influenced by rhetoric and the political opportunism of some
> anti-nuclear activists in the weeks and months ahead.
>
>
>
> Sincerely,
>
> Arthur J. Kremer
>
> Chairman
>
> New York AREA

[colleen o'neill]

Here's another excellent BBC story..and I agree with whoever recommended AlJazeera's coverage , as well.

http://www.bbc.co.uk/news/science-environment-12762608

[dorispulaski]

NEI update, date 3 hours ago. Perhaps there will be external power to the site in the next day. That would be a very good thing, because it expands the options the TEPCO people have to deal with the situation. This is particularly a good thing for reactors 5 & 6 where there have been no explosions, fire and so on. It will also be good for pumping efforts, I would think:

UPDATE AS OF 10:00 A.M. EDT, WEDNESDAY, MARCH 16:

News reports that high radiation levels led to the evacuation of all workers from the Fukushima Daiichi nuclear power station are not accurate. Workers were evacuated for about an hour but returned to the site to continue efforts to restore safe conditions at the plant.

Restoration of electrical power to the site was under way at the Daiichi plant as of 6:00 a.m. EDT Wednesday. A temporary cable was being connected between an off-site power line and Daiichi reactor 3. Off-site power has not been available at the site since the earthquake on March 11

Reactors 1, 2 and 3 at the plant are being cooled with seawater. There is some level of uranium fuel damage at all three units, and containment structure damage is suspected at reactor 2

Before the earthquake, reactor 4 had been in refueling and was completely defueled. Attempts to provide cooling water to the used fuel pool at reactor 4 by helicopter were not successful. Preparations are being made to inject water into the fuel storage pool using a high-capacity spray pump. There have been two fires inside the reactor containment building at reactor 4, but they have been extinguished. Although the reactor containment building at Unit 4 was damaged, the primary containment vessel remains intact

At the Fukushima Daini site, all four reactors are safely shut down and cooling functions are being maintained

IAEA update:

.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.



.

[dorispulaski]

3:35 PM. Nothing really new. Director General of the IAEA Amano is travelling to Japan tomorrow to view the site himself. This situation must be particularly heartbreaking for him, as Japan is his native country.

The Nuclear Energy Institute, the organization of nuclear plant operating companies and employees in the US published the following report:

NEI
Fact Sheet
Industry Taking Action to Ensure Continued Safety at U.S. Nuclear Energy Plants
(Last updated 3/16/11)

(Last updated 3/16/11)
The nuclear energy industry’s priority remains providing Japan with the support necessary to maintain safety at the Fukushima reactors.
Even though the full extent of damage to these reactors still is unknown, the events represent a significant challenge to the structural integrity and safety of the plant. As more is learned about the Japanese events, more long-term corrective actions will be developed.
Senior executives representing all U.S. nuclear power plants are taking the following actions at each of their sites:
1.
Verify each company’s capability to mitigate conditions that result from severe adverse events, including the loss of significant operational and safety systems due to natural events, fires, aircraft impact and explosions. Specific actions include testing and inspecting equipment required to mitigate these events and verifying that qualifications of operators and support staff required to implement them are current.
2.
Verify that the capability to mitigate a total loss of electric power to a nuclear power plant is proper and functional. This will require inspections verifying that all required materials are adequate and properly staged and that procedures are implemented.
3.
Verify the capability to mitigate flooding and the impact of floods on systems inside and outside the plant. Specific actions include verifying required materials and equipment are properly located to protect them from flood.
4.
Perform walk downs and inspection of important equipment needed to successfully respond to fire and flood events. Identify the potential that the equipment’s function could be lost during seismic events appropriate for the site and develop mitigating strategies for potential vulnerabilities.

[dorispulaski]

Today there have been concerns about the state of the Unit 3 & 4 spent fuel rod pools, both by Japanese officials and by the head of the US Nuclear Regulatory Commission.

Various plans for making sure water is in the pools have been described both by IAEA and TEPCO, including dropping it in by helicopter and spraying it in from the side. It's not clear if there is some water in either of the pools or not, or whether there was little or none at some point, but there is some now. If either of the pools are empty, there will be quite a bit of radiation around that area that will make it difficult to do work on them. Neither the IAEA nor TEPCO has given an exact statement on the state of the pools right now. IAEA never gives a statement until they can verify that it is true, so they are always a little late, but believable. I'll keep checking:

The NEI gave this description of the spent fuel rod pools at Daiichi:

Japanese authorities have reported concerns today about the condition of the used nuclear fuel pools at Fukushima Daiichi reactor 3 and reactor 4.

Officials also are preparing to spray water into reactor 4 from ground positions and possibly later into reactor 3. Some debris on the ground from the March 14 explosion at reactor 3 may need to be removed before the spraying can begin.

Most plants store used fuel in steel-lined, concrete vaults filled with water, which acts as a natural barrier for radiation from the used fuel. The water also keeps the fuel cool while the radiation decays-or becomes less radioactive. The water itself does not leave the used fuel pool.

Used nuclear fuel at the Fukushima-Daiichi plant is stored in seven pools (one at each reactor and a shared pool) and in a dry container storage facility (containing nine casks.)

The used fuel pools are designed so that the water in the pool cannot drain down as a result of damage to the piping or cooling systems. The pools do not have drains in the sides or the floor of the pool structure. The only way to rapidly drain down the pool is to have structural damage of the walls or the floor.

More info on what these pools are:

Fact Sheet
Used Nuclear Fuel Storage at the Fukushima Daiichi Nuclear Power Plant
(Last updated 3/16/11, 3:40 p.m.)
Key Facts
��
Used nuclear fuel at the Fukushima-Daiichi plant is stored in seven pools (one at each reactor and a shared pool) and in a dry container storage facility (containing nine casks).
��
Sixty percent of the used fuel on site is stored in the shared pool, in a building separated from the reactor buildings; 34 percent of the used fuel is distributed between the six reactor fuel storage pools, and the remaining 6 percent is stored in the nine dry storage containers.
��
Used fuel pools are robust concrete and steel structures designed to protect the fuel from even the most severe events. Pools are designed with systems to maintain the temperature and level of the water sufficient to provide cooling and radiation shielding.
��
The water level in a used fuel pool typically is 16 feet or more above the top of the fuel assemblies.
��
The used fuel pools at the Fukushima Daiichi reactors are located at the top of the reactor building for ease of handling during refueling operations.
��
The used fuel pools are designed so that the water in the pool cannot drain down as a result of damage to the piping or cooling systems. The pools do not have drains in the sides or the floor of the pool structure. The only way to rapidly drain down the pool is to have structural damage of the walls or the floor.
What Could Happen During an Accident?
��
The systems that cool and maintain water levels in the pools are designed to withstand severe events. If these systems are unable to function, the heat generated by the used fuel would result in a slow increase in the temperature of the spent fuel pool water. The operating temperature of the pools is typically around 40 degrees C or 100 degrees F (the boiling point for water is 100 C or 212 F). This slow increase in temperature will result in an increased evaporation rate. Rapid evaporation of the water will not occur.
��
Exact evaporation rates would depend on the amount of used fuel in the pool and how long it has cooled. The rate at which the pool water level would decrease (due to evaporation or mild boiling) in the absence of cooling system function would not be expected to lower water levels by more than a few percent per day. Given that there is approximately 16 feet of water above the used fuel assemblies, operators would have a few weeks to find another way to add water to the pools before the fuel would become exposed. For example, water could easily be added using a fire hose.
��
If the water level decreases below the top of the fuel assembly, oxidation of the zirconium cladding could occur. This oxidation could result in some hydrogen generation. The rate of hydrogen generation depends on the temperature of the fuel assembly, with hotter temperatures leading to higher gas generation rates. However, only the fuel assemblies with the least cooling time would be
1
2
susceptible to this oxidation and the temperature of the fuel assemblies decreases exponentially with cooling time.
��
Even if the water level in the pools was to decrease sufficiently so that the fuel were exposed to air, the same level of overheating that can occur in a reactor accident would not occur in the used fuel pool because the used fuel assemblies in the pool are cooler than the assemblies in the reactor. It is highly unlikely that used fuel temperatures could reach the point where melting could occur, although some damage to the cladding cannot be ruled out. The likelihood of cladding damage, as with hydrogen generation, decreases substantially with temperature and cooling time.
��
At the surface of the used fuel pool, the gamma dose rate from radiation emanating off the used fuel assemblies is typically less than 2 millirem per hour. If the water level decreases, the gamma radiation level would increase

[dorispulaski]

The IAEA just put this up. There is missing data, conspicuously so, for Unit 4 and Unit3, not to mention 1 & 2. I wish they could spray snow in there, as they do for ski slopes. You need a generator and a pump, as well as a snow machine though.

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



Unit 5

14 March, 10:08 UTC: 59.7 ˚C

15 March, 10:00 UTC: 60.4 ˚C

16 March, 05:00 UTC: 62.7 ˚C



Unit 6

14 March, 10:08 UTC: 58.0 ˚C

15 March, 10:00 UTC: 58.5 ˚C

16 March, 05:00 UTC: 60.0 ˚C



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.



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