Explosions, radiation release at Japan nuclear power plants following earthquake

Tokyo, Japan, March 14, 2011 — Since Japan's deadly earthquake, the Fukushima Daini and Fukushima Daiichi nuclear power plants on Honshu island have suffered fires, explosions and a level of radiation leakage that officials are calling "small."

Units 1, 2, 3 and 4 of the 4,400 MW Fukushima Daini nuclear power plant (also known as Fukushima No. 2) have been deactivated since March 11. During the earthquakes, the water pumps for Daini's reactors were damaged, causing an early failure of the cooling systems and an accompanying increase in pressure. Preparations were made to relieve the pressure by venting vapors, but those precautions reportedly proved unnecessary.

At units 1 and 3 of the 4.7 GW Fukushima Daiichi plant, also known as Fukushima No. 1, hydrogen explosions and white smoke were reported by the plant's operator, Tokyo Electric Power Co. A 20-kilometer area around the facility was ordered evacuated due to possible radioactive contamination.

The walls around reactors 1 and 3 at Daiichi were damaged during the earthquake, but the reactor containment vessels remain intact, according to reports.

Vapor containing low-level radiation was vented to cool the reactors and to prevent over-pressurization. Workers at Daiichi have flooded the reactors with water and boric acid to cool them and quench nuclear reactions.

The confirmed death toll of the 8.9 magnitude earthquake that hit Japan is more than 1,600 dead, with about 1,720 missing and nearly 2,000 injured — although some estimates the number of casualties at about 10,000 people.

TEPCO is releasing regular updates of the situation at the Fukushima plants here at their website.

Here are the most up-to-date reports available as of press time from TEPCO:

Update from TEPCO on Fukushima Daini

Unit 1 (shut down at 2:48 p.m. on March 11)

Reactor is shut down and reactor water level is stable. Offsite power is available.

At 8:19 a.m., March 12, there was an alarm indicating that one of the control rods was not properly inserted. However, at 10:43 a.m., March 12, the alarm was spontaneously called off. Other control rods have been confirmed as fully inserted. Reactor is in subcritical status.

Status of main steam isolation valve: closed. Injection of water into the reactor is done by Make-up Water Condensate System.

We do not believe there is leakage of reactor coolant in the containment vessel at this moment.

At 5:22 a.m., March 12, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at 5:22 a.m., March 12, it was determined that a specific incident stipulated in article 15, clause 1 has occurred.

We decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) in order to fully secure safety. This preparation work started at around 9:43 a.m., March 12 and finished at 6:30 p.m., March 12. Restoration work in reactor cooling function is in progress to achieve reactor cold shutdown.

Unit 2 (shut down at 2:48 p.m. on March 11)

Reactor is shut down and reactor water level is stable. Offsite power is available. Control rods are fully inserted. Reactor is in subcritical status.

Status of main steam isolation valve: closed. Injection of water into the reactor is done by Make-up Water Condensate System.

We do not believe there is leakage of reactor coolant in the containment vessel.

At 5:32 a.m., March 12, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at 5:32 a.m., March 12, it was determined that a specific incident stipulated in article 15, clause 1 has occurred.

We decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) to fully secure safety.

This preparation work started at around 10:33 a.m., March 12 and finished at 10:58 p.m., March 12. Restoration work in reactor cooling function that was conducted to achieve reactor cold shutdown has been completed and cooling of the reactor has been commenced at 7:13 a.m., March 14.

Unit 3 (shut down at 2:48 p.m. on March 11)

Reactor is shut down and reactor water level is stable. Offsite power is available. Control rods are fully inserted. Reactor is in subcritical status.

Status of main steam isolation valve: closed. We do not believe there is leakage of reactor coolant in the containment vessel.

We decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) to fully secure safety.

The preparation started at around 12:08 p.m., March 12 and finished at 12:13 p.m., March 12. Reactor cold shutdown occurred at 12:15 p.m., March 12.

Unit 4 (shut down at 2:48 p.m. on March 11)

Reactor is shut down and reactor water level is stable. Offsite power is available.

At 1:43 p.m., there was a signal indicating that one of the control rods may have not properly inserted. However, we confirmed that it was inserted completely by another signal. We will inspect the reason for this.

Status of main steam isolation valve: closed. Injection of water into the reactor is done by Make-up Water Condensate System.

We do not believe there is leakage of reactor coolant in the containment vessel.

To cool down the reactor, injection of water into the reactor had been done by the Reactor Core Isolation Cooling System, however, at 6:07 a.m., March 12, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at 6:07 a.m., March 12, it was determined that a specific incident stipulated in article 15, clause 1 had occurred.

We decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) to fully secure safety. The preparation started at around 11:44 a.m., March 12 and finished at around 11:52 a.m., March 12.

Restoration work in reactor cooling function is in progress to achieve reactor cold shutdown. Indication from monitoring posts installed at the site boundary did not show any difference from ordinary level.

No radiation impact to the external environment has been confirmed. We will continue to monitor in detail the possibility of radioactive material being discharged from exhaust stack or discharge canal.

Update from TEPCO on Fukushima Daiichi

All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.

Unit 1 (Shut down)

Reactor has been shut down. However, the unit is under inspection due to the explosive sound and white smoke that was confirmed after the big quake occurred at 3:36 p.m.

We have been injecting seawater and boric acid, which absorbs neutron into the reactor pressure vessel.

Unit 2 (Shut down)

Reactor has been shut down and Reactor Core Isolation Cooling System has been injecting water to the reactor. Current reactor water level is lower than normal level, but the water level is steady. After fully securing safety, measures to lower the pressure of reactor containment vessel have been taken, under the instruction of the national government.

Unit 3 (Shut down)

Reactor has been shut down. However, as High Pressure Core Injection System has been automatically shut down and water injection to the reactor was interrupted, following the instructions of the government and to fully secure safety, steps to lower the pressure of reactor containment vessel have been taken. Spraying to lower pressure level within the reactor containment vessel has been canceled.

After that, safety relief valve has been opened manually, lowering the pressure level of the reactor, which was immediately followed by injection of boric acid water, which absorbs neutron, into the reactor pressure vessel.

Unit 4 (shut down before time of earthquake due to regular inspection)

Reactor has been shut down and sufficient level of reactor coolant to ensure safety is being maintained. Currently, we do not believe there is any reactor coolant leakage inside the reactor containment vessel.

Unit 5 (shut down before time of earthquake due to regular inspection)

Reactor has been shut down and sufficient level of reactor coolant to ensure safety is being maintained. Currently, we do not believe there is any reactor coolant leakage inside the reactor containment vessel.

Unit 6 (shut down before time of earthquake due to regular inspection)

Reactor has been shut down and sufficient level of reactor coolant to ensure safety is maintained. Currently, we do not believe there is any reactor coolant leakage inside the reactor containment vessel.

Casualties

Two workers of cooperative firm were injured at the occurrence of the earthquake, and were transported to the hospital.

One TEPCO employee who was not able to stand on his own was transported to the hospital by an ambulance.

One subcontract worker at earthquake-proof building was unconscious and transported to the hospital by an ambulance.

The radiation exposure of one TEPCO employee, who was working inside the reactor building, exceeded 100 mSv and was transported to the hospital.

Two TEPCO employees felt bad during their operation in the central control rooms of Unit 1 and 2 while wearing full masks, and were transferred to Fukushima Daini Power Station for consultation with a medical advisor.

Four workers were injured and transported to the hospital after explosive sound and white smoke were confirmed around the Unit 1.

Presence of two TEPCO employees at the site are not confirmed

Other updates

We are currently coordinating with the relevant authorities and departments as to how to secure the cooling water to cool down the water in the spent nuclear fuel pool.

We measured radioactive materials inside of the nuclear power station area (outdoor) by monitoring car and confirmed that radioactive materials level is higher than ordinary level. Also, the level at monitoring post is higher than ordinary level.

We will continue to monitor in detail the possibility of radioactive material being discharged from exhaust stack or discharge canal. The national government has instructed evacuation for those local residents within 20 kilometer radius of the periphery because it's possible that radioactive materials are discharged.

We will continue to take all measures to restore the security of the site and to monitor the environment of the site periphery.

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