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requiring new water to be added to keep the reactor cores covered. Damage has occurred to fuel rods in

the cores where water levels have dropped leaving them uncovered and overheated.

A decay heat output of 7 MW (typical of a Fukushima reactor a few days after shutdown) has

the capacity to boil off about 200-300 tonnes of water per day, which puts the requirement for cooling

water in context.

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Releasing gases from the reactor is necessary if pressure becomes too high and has the benefit

of cooling the reactor as water boils off, but this also means cooling water is being lost and must be

replaced. Assuming no damage to the fuel elements, water inside the reactor should be only very

slightly radioactive.

In a press release at 07:00 JST 12 March, TEPCO stated, "Measurement of radioactive material(iodine, etc.) by monitoring car indicates increasing value compared to normal level. One of the

monitoring posts is also indicating higher than normal level." Dose rates recorded on the main gate rose

from 69 nGy/h (for gamma radiation, equivalent to 69 nSv/h) at 04:00 JST, 12 March, to 866 nGy/h

(equivalent to 0.866 µSv/h) 40 minutes later, before hitting a peak of 385.5 Sv/h at 10:30 JST. At 13:30

JST, workers detected radioactive caesium-137 and iodine-131 near reactor 1,

which indicated some of

the core's fuel had been damaged.[91]

Cooling water levels had fallen so much that parts of the nuclear

fuel rods were exposed and partial melting might have occurred. Radiation levels at the site boundary

exceeded the regulatory limits.[94]

On 14 March 2011, radiation levels had continued to increase on the premises, measuring at

02:20 an intensity of 751 Sv/hour on one location and at 02:40 an intensity of 650 Sv/hour at another

location on the premises. On 16 March the maximum readings peaked at 10850 Sv/hour.

Explosion of reactor 1 building

At 15:36 JST on 12 March 2011 there was an explosion at Unit 1. Four workers were injured, and

the upper shell of the reactor building was blown away leaving in place its steel frame. The outer

building is designed to provide ordinary weather protection for the areas inside, but not to withstand

the high pressure of an explosion or to act as containment for the reactor. In the Fukushima I reactors

the primary containment consists of "drywell" and "wetwell" concrete structures immediately

surrounding the reactor pressure vessel.

Experts soon agreed the cause was a hydrogen explosion. Almost certainly the hydrogen was

formed inside the reactor vessel because of falling water levels, and this hydrogen then leaked into the

containment building. Exposed Zircaloy cladded fuel rods became very hot and reacted with steam,

oxidising the alloy, and releasing hydrogen. Safety devices normally burn the generated hydrogen when

it is vented before explosive concentrations are reached but these systems failed, possibly due to the

shortage of electrical power.

Officials indicated the container of the reactor had remained intact and there had been no large

leaks of radioactive material, although an increase in radiation levels was confirmed following the

explosion. ABC News (Australia) reported that according to the Fukushima prefectural government,

radiation dose rates at the plant reached 1015 microsievert per hour (1015 µSv/h). Two independent

nuclear experts cited design differences between theChernobyl Nuclear Power Plant and the Fukushima

I Nuclear Power Plant, one of them saying he did not believe that a Chernobyl-style disaster will occur.

The IAEA stated on 13 March that four workers had been injured by the explosion at the Unit 1 reactor,

and that three injuries were reported in other incidents at the site. They also reported one worker was

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exposed to higher-than-normal radiation levels but that fell below their guidance for emergency

situations.

Seawater used for cooling

At 20:05 on 12 March 2011, under the terms of the Nuclear Regulation Act, paragraph 3, article

64 and a directive issued by the Prime Minister, the Japanese government ordered seawater to be

injected into Unit 1 in an ultimate effort to cool the degraded reactor core. At 21:00 JST TEPCO

announced they planned to cool the reactor with seawater (started at 20:20 JST), adding boric acid to

act as a neutron absorber to prevent a criticality accident. The water was to take five to ten hours to fill

the reactor core, after which the reactor would cool down in around ten days. At 23:00 JST TEPCO

announced due to the quake at 22:15, workers had temporarily suspended filling of the reactor but

filling resumed after a short while. The last resort decision to use seawater as coolant in the reactor

implied the reactor would have to be decommissioned because of contamination by salt and other

impurities.

NISA reported that injection of seawater into the Reactor Pressure Vessel through the fire

extinguisher system commenced at 11:55 on 13 March, though this was corrected to state 12 March in

later press releases. Some reports refer to injection into the Primary Containment Vessel and exact

details are confused. At 01:10 on 14 March injection of seawater was halted because all available water

in the plant pools had run out (similarly, feed to unit 3 was halted). Water supply was restored at 03:20.

NISA stated 70% of the fuel rods were damaged in news reports the morning of 16 March.

On 18 March work was proceeding to install a new electrical distribution panel in an office

adjacent to unit 1 which was to supply power from a transmission grid transformer at unit 2. It was

anticipated power would be restored to units 1 and 2 by the following Saturday (19 March). Power

became available at unit 2 on 20 March As of 21 March injection of sea water for cooling was continuing

but the unit seemed to be in a stable conditon. Repairs to restore control instrumentation were

proceeding. On 23 March it became possible to inject water into the reactor using the feed water system

rather than the fire extinguisher line, raising the rate of adding seawater from 2m3/hr to18m

3/hr, later

lowered to 11m3/hr.

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REACTOR UNIT 2

Unit two was operating at the time of the earthquake and experienced the same controlled

initial shutdown as the other units. Diesel generators and other systems failed when the tsunami

overran the plant. Reactor core isolation cooling system (RCIC) initially operated to cool the core but by

midnight the status of the reactor was unclear although some monitoring equipment was still operatingon temporary power. Coolant level was stable, but preparations were underway to reduce pressure in

the reactor containment vessel should this become necessary, though TEPCO did not state in press

releases what these were, and the government had been advised that this might happen. RCIC was

reported by TEPCO shut down around 19:00 JST on 12 March, but again reported to be operating as of

09:00 JST 13 March. Pressure reduction of the reactor containment vessel commenced before midnight

on 12 March though IAEA reported as of 13:15 JST 14 March that according to information supplied to

them, no venting had taken place at the plant. A report in the New York Times suggested that plant

officials initially concentrated efforts on a damaged fuel storage pool at unit 2, distracting attention

from problems arising at the other reactors, but this incident is not reported in official press

releases. IAEA report that on 14 March at 09:30 RCIC was still operating and that power was beingprovided by mobile generator.

Cooling problems at unit 2

On 14 Mar TEPCO reported the failure of the RCIC system. Fuel rods had been fully exposed for

140 minutes and there was a risk of a core meltdown. Reactor water level indicators were reported to

be showing minimum values at 19:30 JST 14 March.

At 22:29 JST, workers had succeeded in refilling half the reactor with water but parts of the rods

were still exposed, and technicians could not rule out the possibility that some had melted. Holes blown

in the walls of reactor building 2 by the earlier blast from unit 3 would allow the escape of hydrogenvented from the reactor and hopefully prevent a similar explosion. At 21:37 JST the measured dose

rates at the gate of the plant reached a maximum of 3.13 millisievert per hour, which was enough to

reach the annual limit for non-nuclear workers in twenty minutes,[122]

but had fallen back to 0.326

millisieverts per hour by 22:35.

It was believed that around 23:00 JST the 4 m long fuel rods in the reactor were fully exposed

for the second time. At 00:30 JST of 15 March, NHK ran a live press conference with TEPCO stating that

the water level had sunk under the rods once again and pressure in the vessel was raised. The utility said

that the hydrogen explosion at unit 3 might have caused a glitch in the cooling system of unit 2: Four out

of five water pumps being used to cool unit 2 reactor had failed after the explosion at unit 3. In addition,

the last pump had briefly stopped working when fuel ran out. To replenish the water, the contained

pressure would have to be lowered first by opening a valve of the vessel. The unit's air flow gauge was

accidentally turned off and, with the gauge turned off, flow of water into the reactor was blocked

leading to full exposure of the rods.

As of 04:11 JST, 15 March, water was being pumped into the reactor of unit 2 again. At 10:38

JST, 15 March, water level was reported to be at 1.20 meters and rising.

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Explosion in reactor 2 building

An explosion was heard after 06:14 JST on 15 March in unit 2, possibly damaging the pressure-

suppression system, which is at the bottom part of the containment vessel.[131][132] The radiation level

was reported to exceed the legal limit and the plant's operator started to evacuate all non-essential

workers from the plant. Only a minimum crew of 50 men, also referred to as the Fukushima 50, was leftat the site. Soon after, radiation equivalent dose rates had risen to 8.2 mSv/h around two hours after

the explosion and again down to 2.4 mSv/h, shortly after. Three hours after the explosion, the rates had

risen to 11.9 mSv/h.

While admitting that the suppression pool at the bottom of the containment vessel had been

damaged in the explosion, causing a drop of pressure there, Japanese nuclear authorities emphasized

that the containment had not been breached as a result of the explosion and contained no obvious

holes.

In a news conference on 15 March the director general of the IAEA, Yukiya Amano, said that

there was a "possibility of core damage" at the No. 2 unit of the damaged Fukushima power plant. He

went on to add that the damage was estimated as being "less than five percent".[139] The Nuclear and

Industrial Safety Agency stated 33% of the fuel rods were damaged, in news reports the morning of 16

March.

Work

Work was to continue through the night aimed at reconnecting mains power to the reactor from

the transmission grid once water spraying of unit 3 ceased at 20:09 on 17 March. By midday on 19

March grid power had been connected to the existing transformer at unit 2 but work continued to

connect the transformer to the new distribution panel installed in a nearby building. Mains electricity

became available at unit 2 at 15:46 JST on 20 March but equipment still had to be repaired and

reconnected.

Spent fuel pool

40 tonnes of sea water was added to the spent fuel pool on 20 March. The temperature in the

spent fuel pool was 53 °C as of 22 March 11:00 JST.[57]

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REACTOR UNIT 3

Unlike the other five reactor units, reactor 3 runs on mixed uranium and plutonium oxide,

or MOX fuel, making it potentially more dangerous in an incident due to the neutronic effects of

plutonium on the reactor, the very long half-life of plutonium's radioactivity, and

the carcinogenic effects

in the event of release to the environment. Units 3 and 4 have a shared controlroom.

Cooling problems at unit 3

Early on 13 March 2011, an official of the Japan Nuclear and Industrial Safety Agency told a

news conference that the emergency cooling system of Unit 3 had failed, spurring an urgent search for a

means to supply cooling water to the reactor vessel in order to prevent a meltdown of its reactor

core. At 05:38 there was no means of adding coolant to the reactor due to loss of power. Work to

restore power and vent pressure continued. At one point, the top three meters of mixed oxide (MOX)

fuel rods were not covered by coolant.

At 07:30 JST, TEPCO prepared to release radioactive steam, indicating that "the amount of

radiation to be released would be small and not of a level that would affect human health"[149]

and

manual venting took place at 08:41 and 09:20. At 09:25 JST on 13 March 2011, operators began injecting

water containing boric acid into the primary containment vessel (PCV) via a fire pump. When water

levels continued to fall and pressure to rise, the injected water was switched to sea water at 13:12. By

15:00 it was noted that despite adding water the level in the reactor did not rise and radiation had

increased. A rise was eventually recorded but the level stuck at 2 m below the top of reactor core. Other

readings suggested that this could not be the case and the gauge was malfunctioning.

Injection of sea water into the PCV was discontinued at 01:10 on 14 March because all the water

in the reserve pool had been used up. Supplies were restored by 03:20 and injection of water

resumed.[152] On the morning of 15 March 2011 (JST), Secretary Edano announced that according to the

TEPCO, at one location near reactor units 3 and 4, radiation at an equivalent dose rate of 400 mSv/h was

detected. This might have been due to debris from the explosion in unit 4.


At 12:33 JST on 13 March 2011, the chief spokesman of the Japanese government, Yukio Edano

said hydrogen was building up inside the outer building of Unit 3 just as had occurred in Unit 1,

threatening the same kind of explosion. At 11:15 JST on 14 March 2011, the envisaged explosion of the

building surrounding reactor 3 of Fukushima 1 occurred, due to the ignition of built up hydrogengas. The Nuclear and Industrial Safety Agency of Japan reported, as with Unit 1, the top section of the

reactor building was blown apart, but the inner containment vessel was not breached. The explosion

was larger than that in Unit 1 and felt 40 kilometers away. Pressure readings within the reactor

remained steady at around 380 kPa at 11:13 and 360 kPa at 11:55 compared to nominal levels of

400 kPa and a maximum recorded of 840 kPa. Water injection continued. Dose rates of 0.05 mSv//h

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were recorded in the service hall and of 0.02 mSv/h at the plant entrance. Eleven people were reported

injured in the blast.

Spent fuel pool

Around 10:00 JST, 16 March, NHK helicopters flying 30 km away videotaped white fumes rising

from the Fukushima I facility. Officials suggested that the reactor 3 building was the most likely source,

and said that its containment systems may have been breached. The control room for reactors 3 and 4

was evacuated at 10:45 JST but staff were cleared to return and resume water injection into the reactor

at 11:30 JST. At 16:12 JST Self Defence Force (SDF) Chinook helicopters were preparing to pour water on

unit 3, where white fumes rising from the building was believed to be water boiling away from the fuel

rod cooling pond on the top floor of the reactor building, and on unit 4 where the cooling pool was also

short of water. The mission was cancelled when helicopter measurements reported radiation levels of

50 mSv. At 21:06 pm JST government reported that major damage to reactor 3 was unlikely but that it

nonetheless remained their highest priority.

Early on 17 March, TEPCO requested another attempt by the military to put water on the

reactor using a helicopter and four helicopter drops of seawater took place around 10:00 JST. The riot

police used a water cannon to spray water onto the top of the reactor building and then were replaced

by members of the SDF with spray vehicles. On 18 March a crew of firemen took over the task with six

fire engines each spraying 6 tons of water in 40 minutes. 30 further hyper rescue vehicles were involved

in spraying operations. Spraying continued each day to 23 March because of concerns the explosion in

unit 3 may have damaged the pool (total 3,742 tonnes of water sprayed up to 22 March) with changing

crews to minimise radiation exposure. Lighting in the control room was restored on 22 March after a

connection was made to a new grid power supply and by 24 March it was possible to add 35 tonnes of

seawater to the spent fuel pool using the cooling and purification system.

Ongoing Emissions

Grey smoke was reported to be rising from the southeast corner of reactor 3 on Monday

afternoon, 21 March 2011. The spent fuel pool is located at this part of the building. Workers were

evacuated from the area. Later measurements showed no significant change in radiation levels and the

smoke subsided later on the same day.

Per AP reports on Wed, 23 March, black smoke billowed from Unit 3, prompting another

evacuation of workers from the plant Wednesday afternoon, Tokyo Electric Power Co. officials said, but

they said there had been no corresponding spike in radiation at the plant. "We don't know the reason

for the smoke", Hidehiko Nishiyama of the Nuclear Safety Agency said.

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REACTOR UNIT 4

At the time of the earthquake unit 4 had been shut down for a scheduled periodic inspection

since 30 November 2010. All 548 fuel rods had been transferred in December 2010 from the reactor to

thespent fuel pool on an upper floor of the reactor building where they were held in racks containing

boron to damp down any nuclear reaction. The pool is used to store rods for some time after removalfrom the reactor and now contains 1,479 rods. Recently active fuel rods produce more decay heat than

older ones. At 04:00 JST on Monday 14 March, water in the pool had reached a temperature of 84 °C

compared to a normal value of 4050 °C. IAEA was advised that the temperature value remained 84 °C

at 19:00 JST on 15 March, but as of 18 March, no further information was reported.


At approximately 06:00 JST on 15 March, an explosionthought to have been caused by

hydrogen accumulating near the spent fuel ponddamaged the 4th floor rooftop area of the Unit 4

reactor as well as part of the adjacent Unit 3. At 09:40 JST, 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 2011 (JST), Secretary Edano announced that according to the Tokyo

Electric Power Company, radiation dose equivalent rates measured from the reactor unit 4 reached 100

mSv per hour. Government speaker Edano has stated that there was no continued release of "high

radiation".

Japan's nuclear safety agency reported two holes, each 8 meters square (64 m2 or 689 sq. feet)

in a wall of the outer building of the number 4 reactor after an explosion there. Further, at 17:48 JST it

was reported that water in the spent fuel pool might be boiling.

As of 15 March 2011 21:13 JST, radiation inside unit 4 had increased so much inside the control

room that employees could not stay there permanently any more. Seventy staff remained on site but

800 had been evacuated. By 22:30 JST, TEPCO was reported to be unable to pour water into No. 4

reactor's storage pool for spent fuel. At around 22:50 JST, it was reported that the company was

considering the use of helicopters to drop water on the spent fuel storage pool but this was postponed

because of concerns over safety and effectiveness. and the use of high-pressure fire hoses was

considered instead.

A fire was discovered at 05:45 JST on 16 March in the north west corner of the reactor building

by a worker taking batteries to the central control room of unit 4. 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 JST, TEPCO released a photograph of No.4 reactor showing that "a large portion of the

building's outer wall has collapsed." Technicians reportedly considered spraying boric acid on the

building from a helicopter.

On 18 March, it was reported that water sprayed into the spent fuel pool was disappearing

faster than evaporation could explain, suggesting leakage.

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SDF trucks sprayed water onto the building to try to replenish the pool on 20 March.

On 22 March, the Australian military flew in Bechtel-owned robotic equipment for remote

spraying and viewing of the pool. The Australian reported this would give the first clear view of the pool

in the "most dangerous" of the reactor buildings.

Possibility of criticality in the spent fuel pool

At approximately 14:30 on 16 March, TEPCO announced that the storage pool, located outside

the containment area, might be boiling, and if so the exposed rods could reach criticality. The BBC

commented that criticality would not mean a nuclear bomb-like explosion, but could cause a sustained

release of radioactive materials. Around 20:00 JST it was planned to use a police water cannon to spray

water on unit 4.

On 16 March the chairman of United States Nuclear Regulatory Commission (NRC), Gregory

Jaczko, said in Congressional testimony that the NRC believed all of the water in the spent fuel pool had

boiled dry. Japanese nuclear authorities and TEPCO contradicted this report, but later in the day Jaczkostood by his claim saying it had been confirmed by sources in Japan. At 13:00 TEPCO claimed that

helicopter observation indicated that the pool had not boiled off. The French Institut de radioprotection

et de sûreté nucléaire agreed, stating that helicopter crews diverted planned water dumps to unit 3 on

the basis of their visual inspection of unit 4.

On 18 March, Japan was reportedly planning to import about 150 tons of boric acid, a neutron

poison, from South Korea and France to counter the threat of criticality.

On 23 March it was reported that low level Neutron radiation (reported as "neutron beam") was

observed several times, which may indicate damaged fuel reaching criticality somewhere at the plant.

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REACTOR UNIT 5 AND 6

Both reactors were off line at the time the earthquake struck (reactor 5 had been shut down on

3 January 2011 and reactor 6 on 14 August 2010), although they were still fueled, unlike reactor 4 where

the fuel rods had been removed prior to the earthquake.

Government spokesman Edano stated on 15 March that reactors 5 and 6 were being closely

monitored, as cooling processes were not functioning well. At 09:16 JST the removal of roof panels from

reactor buildings 5 and 6 was being considered in order to allow any hydrogen build-up to escape. At

21:00 on 15 March, water levels in unit 5 were reported to be 2 m above fuel rods, but were falling at a

rate of 8 cm per hour.

On 17 March, Unit 6 was reported to have operational diesel-generated power and this was to

be used to power pumps in unit 5 to run the Makeup Water Condensate System (MUWC) to supply

more water. Preparations were made to inject water into the reactor pressure vessel once mains power

could be restored to the plant, as water levels in the reactors were said to be declining. It was estimated

that grid power might be restored on 20 March through cables laid from a new temporary supply being

constructed at units 1 and 2.

Information provided to the IAEA indicated that storage pool temperatures at both units 5 and 6

remained steady around 6068 °C between 19:00 JST 14 March and 21:00 JST 18 March, though rising

slowly. On 18 March reactor water levels remained around 2m above the top of fuel rods. It was

confirmed that panels had been removed from the roofs of units 5 and 6 to allow any hydrogen gas to

escape. At 04:22 on 19 March the second unit of emergency generator A for unit 6 was restarted which

allowed operation of pump C of the residual heat removal system (RHR) in unit 5 to cool the spent fuel

storage pool. Later in the day pump B in unit 6 was also restarted to allow cooling of the spent fuel pool

there. Temperature at unit 5 pool decreased to 48 °C on 19 March 18:00 JST, and 37 °C on 20 Marchwhen unit 6 pool temperature had fallen to 41 °C. On 20 March NISA announced that both reactors had

been returned to a condition of cold shutdown. External power was partially restored to unit 5 via

transformers at unit 6 connected to the Yonoromi power transmission line on 21 March.

On 23rd March, it was reported that the cooling pump at reactor No 5 stopped working when it

was transferred from backup power to the grid supply.

Used fuel assemblies taken from reactors are initially stored for at least 18 months in the pools adjacent

to their reactors. They can then be transferred to the central fuel storage pond. This contains 6375 fuel

assemblies and was reported 'secured' with a temperature of 55 °C. After further cooling, fuel can be

transferred to dry cask storage, which has shown no signs of abnormalities. On 21 March temperatures

in the fuel pond had risen a little to 61 °C and water was sprayed over the pool.

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REACTOR STATUS SUMMARY

The Japan Atomic Industrial Forum (JAIF) has developed a status summary table for the Fukushima

nuclear power plants and is publishing updates twice each day.

Legend

No immediate concern Concern Severe Condition

Status of

Fukushima I at

23 March 21:00

JST (23 March

12:00 UTC)[226]

Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6

Power output(MWe)

460 784 784 784 784 1,100

Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5

Core fuel

assemblies[228] 400 548 548 0

[170]548 764

Spent fuel

assemblies[170]

292 587 514 1,331 946 876

Spent fuel

residual decay

heat[229][230]

60 kW 400 kW 200 kW 2,000 kW 700 kW 600 kW

Fuel typeLow-enriched

uranium

Low-enriched

uranium

Mixed-oxide

(MOX) and

low-enriched

uranium

Low-enriched

uranium

Low-

enriched

uranium

Low-

enriched

uranium

Status at

earthquakeIn service In service In service

Outage

(scheduled)

Outage(scheduled

)

Outage(schedule

d)

Fuel integrity Damaged Damaged DamagedSpent fuel

damaged

Not

damaged

Not

damaged

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Reactor

pressure

vesselintegrity

Unknown Unknown UnknownNot damaged

(defueled)

Not

damaged

Not

damaged

Containment

integrity Not damaged

Damage

suspected Not Damaged Not damaged

Not

damaged

Not

damaged

Core cooling

system 1

(ECCS/RHR)

Not functional Not functional Not functionalNot necessary

(defueled)Functional

Functiona

l

Core cooling

system 2

(RCIC/MUWC)

Not functional Not functional Not functionalNot necessary

(defueled)

Functional

(in cold

shutdown)

Functiona

l (in cold

shutdown

)

Building

integrity

Severely

damaged

Slightly

damaged, also

panel removed

to prevent

hydrogen

explosion

Severely

damaged

Severely

damaged

Panel

removed

to prevent

hydrogen

explosion

Panel

removed

to

prevent

hydrogen

explosion

Pressure

vessel, water

level

Fuel exposed

partially or

fully

Fuel exposed

partially or

fully

Fuel exposed

partially or

fully

Safe (defueled)

Safe (in

cold

shutdown)

Safe (in

coldshutdown

)

Pressure

vessel,

pressure

Stable Unknown Unknown Safe (defueled)

Safe (in

cold

shutdown)

Safe (in

cold

shutdown

)

Containment

pressure

Stable Stable Decreasing Safe Safe Safe

Seawater

injection into

core

Continuing Continuing ContinuingNot necessary

(defueled)

Not

necessary

Not

necessary

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Seawater

injection into

containment

vessel

ContinuingPerformed 19

March[231]

Continuing Not necessary

Not

necessary

Not

necessary

Containment

venting

Temporarily

stopped

Temporarily

stopped

Temporarily

stoppedNot necessary

Not

necessary

Not

necessary

INES Level 5 Level 5 Level 5 Level 3

Environmental

effect

Main Gate: 265.4 Sv/hour at 23 March 15:00; North of Service Building:

2015.0 Sv/hour at 21 March 16:30. Radionuclides were detected in milk produced in

Fukushima and Ibaraki prefectures and spinach and other vegetables from Fukushima,

Ibaraki, and other prefectures.[232] Radioactive Iodine-131 has been found in tap water

in Fukushima prefecture, and radioactive Iodine-131, Caesium-134, and Caesium-137 have been detected in seawater samples in the vicinity of the station.

Evacuation radi

us

20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km

from the Fukushima I Nuclear Power Station are to stay indoors.

General status

from all

sources

regardingreactor cores

Stabilized by

injecting sea

water and

boron[233]

Stabilized by

injecting sea

water and

boron[233]

Stabilized by

injecting sea

water and

boron;

pressureelevated on 20

March[233]

Defueled

Cold

shutdown

on 20

March

14:30

JST[51][233]

Cold

shutdown

on 20

March

19:27

JST[51][233]

General status

from all

sources

regarding Spen

t Fuel

Pools (SFP)

Water

injection

considered, 60

°C on 20

March byinfrared

helicopter

measurement[

234]

Water

injection

concluded on

20

March,[51]

40

°C on 20March by

infrared

helicopter

measurement[

234]

Water level

low, sprayed

water injection

continues, 60

°C on 20

March by

infrared

helicopter

measurement[

234]

Water level

low, sprayed

water injection

continues after

hydrogen

explosion from

pool, 40 °C on

20 March by

infrared

helicopter

measurement[

234]

Cooling

system

restored,

39.0 °C on

23 March

12:00

JST[235]

Cooling

system

restored,

20.0 °C on

23 March

12:00

JST[235]

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As of 18 March 2011, the French nuclear authorityand as of 15 March 2011, the Finnish nuclear

authorityestimate the unfolding crisis at Fukushima to be a Level 6 on the INES.

USA, Australia and Sweden have instructed their citizens to evacuate a radius of minimum 80 km. Spain

has advised their citizens to leave an area of 120 km, Germany has advised their citizens to leave even

the metropolitan area of Tokyo, and South Korea advises to leave farther than 80 km and to have plansto evacuate by all possible means. Travel to Japan is very low, but additional flights have been chartered

by some countries to assist those who wish to leave. Official evacuation of Japan have been started by

several nations.

SOLUTIONS CONSIDERED OR ATTEMPTED

Legend

Effective Partiallyeffective

Noteffective

Not applicable or unknown

Solution General effectiveness

Specific effectiveness

Reactor

cores

Spent fuel

pools

1 2 3 4 5 6 1 2 3 4 5 6

Backup diesel generators:

The backup diesel generators

operated initially.

All generators disabled by the

tsunami. One generator repaired 17

March at units 5 and 6 to cool spent

fuel pools. A second on 19 March

powered reactor cooling and

reactors 5 and 6 were brought back

to cold shutdown.

Backup batteries:

The backup batteries maintained

some control functions and limited

cooling for 8 hours after the

Effective but only designed to work

for 8 hours. The operators were

unable to connect portable

generators before the 8 hours ran

out. However limited cooling was

not designed to stabilise reactors

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generators failed. indefinitely even if batteries were

recharged.

Mobile power units:

After the power loss due to the

earthquake and tsunami, mobile

power units were sent to the plant.

Flooding of plant prevented mobile

generators being connected andsufficiently large units were not

available

Some central monitoring

systems

Repair power lines to provide

electricity:

1 km of new grid cable and

replacement switchgear wasinstalled to provide power to plant.

Power was connected to the

distribution panels of Units 2 and 5

on Sunday 20 March and power is

now available to Units 1, 2, 5 and

6 but only equipment in units 5 and

6 is sufficiently repaired to function.

Units 3 and 4 are scheduled to have

electricity connected to their

distribution panels on 22 March.

Central control room

Emergency cooling systems:

The Emergency Core Cooling System

(ECCS) includes: High Pressure

Coolant Injection System (HPCI),

Reactor Core Isolation Cooling

System (RCIC), Automatic

Depressurization System (ADS), Low

Pressure Core Spray System (LPCS),

Low Pressure Coolant Injection

System (LPCI), Depressurization

Valve System (DPVS), Passive

Containment Cooling System (PCCS),

and Gravity Driven Cooling System

(GDCS).

The RCIC operated initially and the

HPCI worked until the toruses

overheated. Cooling systems were

restored to Units 5 and 6 on 20

March. BBC news reported on 17

March, that some of the original

water pumps might be inoperable

due to damage from injected sea

water, the earthquake, tsunami or

explosions.

Cooling core containment areas by

adding sea water:

Sea water with neutron absorbing

boric acid is being manually injected

into the Reactor Pressure Vessel of

Sea water cooling has been partially

effective for the cooling reactor

core but fuel damage has taken

place. At one point available water

in site pools ran out. White smoke

or steam was reported rising from

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units 1, 2 and 3 via fire extinguisher

system line.

Unit 3.

Spraying water into spent fuel pools

with water cannon and fire engines:

Police, military and firemen working

in shifts to reduce radiation exposure

used water cannons and fire engines

to spray water onto the roofs and

into the spent fuel pools of reactor

unit Number 3 although it is unclearif any water reached the spent fuel

pool. Unit 4 was sprayed also.

SFP 1: As of Saturday 19 March, SFP

1's decrease in water level suggests

it may have a leak and spraying may

be attempted. SFP was 60 °C on 20

March according to an infrared

helicopter measurement.

SFP 2: On 20 March, 40 tons of sea

water was sprayed into unit 2. SFP

was 40 °C on 20 March according to

an infrared helicopter

measurement. Spraying appeared

to have been effective even though

the building is nearly intact and

there were few holes to spray water

into.

SFP 3: On Thursday 17 March,

steam emanated from the roof of

unit 3 after spraying which

suggested that spraying was at least

partially successful in reaching

overheated spent fuelrods. Radiation levels dropped

slightly after the steam had

dissipated suggesting the cooling

may have been successful. SFP 3

may have a leak and reduced water

holding capacity due to a previous

explosion. SFP 3 was sprayed for 13

hours on 20 March using unmanned

vehicles and spraying is continuing.

SFP was 60 °C on 20 March

according to an infrared helicopter

measurement.

Water in SFP 4 was disappearing

faster than evaporation could

explain and some suspected that a

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hole was leaking water from that

pool.

However, inspection during

helicopter water drops indicated

there was water in the pool of Unit

4; so, spraying on Friday 18 March

focused on Unit 3. SFP 4 stopped

boiling although it is releasing a

large amount of heat due to the

large amount of fuel stored there.

On Sunday 20 March, SFP 4 was

sprayed with 100 tons of water

using unmanned vehicles. SFP was

40 °C on 20 March according to an

infrared helicopter measurement.

Helicopter dumping of sea water into

spent fuel pools:

Helicopters used for forest fire

suppression dumped sea water onto

the reactors.

Strong winds prevented effective

targeting of the dumped water since

high radiation levels prevented the

helicopters from flying low. Video

appeared to show much of the

water dispersing in mid-air

weakening the intensity of the

water to cool the overheating

reactor.

Boron:

Officials have considered insertion or

targeted aerial dropping of boric

acid, boronated plastic beads or

boron carbide pellets into the spent

fuel pools to absorb neutrons.

France is flying 95 tonnes of boron

to Japan on Thursday, 17 March

2011. Neutron absorbing boric acid

is being injected into the reactor

cores with the sea water but it is

unclear if boric acid is included with

the spraying of SFPs. Effectiveness

unknown.

Liquid metal cooling:

On 17 March, KyivPost reported that

a Ukrainian group of specialists who

were involved in the aftermath of

the Chernobyl nuclear

disaster proposed low-melting and

This solution has similarities withthe 2400 metric tonnes of lead (see

alsoLead-cooled fast reactor ) used

to successfully cool and cover

the Chernobyl nuclear plant but

avoids the toxic lead. Liquid metal

cooled reactors were used in

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chemically neutral metal, such as tin,

to cool the fuel rods even if molten

or damaged. [267]

Chopped tin can be injected in the

reactor through the existing cooling

water pipes with compressed inert

gas, helium or argon. Melted tin

creates a crust (low vapor pressure),

cools the reactor and delays

the decay productsrecovery. Liquid

metal cooled reactors need no pump

and due to no pressure and a wider

temperature-range are less likely to

a Loss-of-coolant accident.

several Soviet submarines which

shows additional basic feasibility.

It also avoids the danger of

additional explosions caused by

water breaking down to hydrogen

and oxygen starting at temperatures

around 800 °C due toThermolysis.

A team of Ukrainian nuclear

specialists is ready to fly out for

realizing this in practice. The

Japanese Embassy was informed.

"Sarcophagus":

On 18 March, Reuters reportedthat

Hidehiko Nishiyama, Japan's nuclear

agency spokesman when asked

about burying the reactors in sand

and concrete, said: "That solution is

in the back of our minds, but we are

focused on cooling the reactors

down."

1800 metric tonnes of sand and clay

used after the Chernobyl disaster

were counter-productive, acting

as thermal insulators and

accumulating heat.

So first a non-evaporating coolant

like liquid (and minimum surface-

frozen) metal has to be applied, and

after temperature has decreased,a sarcophagus.

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NEW ERA UNIVERSITYCOLLEGE OF ENGINEERING AND TECHMOLOGY

MECHANICAL ENGINEERING DEPARTMENT

Fukushima Nuclear Power Plant(FINAL EXAM ± ME481)

Kenneth D. Pacada

BSME / 4th Year

0710375

Engr. Nelio S. Gesmundo Jr.Instructor

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