Monday, March 14, 2011

Update on Fukushima Daiichi Unit 2

Update from TEPCO:

Unit 2 (shut down at 2:48pm on March 11th)
- 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 5:32am, Mar 12th, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at 5:32am, Mar 12th, 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 10:33am, Mar 12th and finished at 10:58pm, Mar 12th.
- Restoration work in reactor cooling function is in progress to achieve reactor cold shutdown.
- 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 am, Mar 14th.
At approximately 11:01am, an explosion followed by white smoke occurred at the reactor building of Unit 3. It was believed to be a hydrogen explosion.

According to the parameter, it is believed that the reactor containment vessel remains intact. However, the status of the plant and the impact of radioactive materials to the outside environment are presently under investigation. (previously announced)

As of 1:30 pm, 4 TEPCO employees and 3 workers from other companies have sustained injuries (all of them are conscious). 3 ambulances are in operation to care for them and 2 have already dispatched the casualties to the hospital.

As of 0:30 pm, the measured value of radiation dose near MP6 was 4╬╝Sv/h. The increase of the radiation dose cannot be confirmed at this time.

As of 0:30 pm, the measured value of radiation dose at the monitoring post in Fukushima Daini Power Station located approximately 10 km south of Fukushima Daiichi Power Station remains at the same level.

In light of the incidents that have occurred at Units 1 and 3, we are considering applying prevention measures to the wall of the reactor building to ventilate the hydrogen gas contained in Unit 2.

TEPCO continues to take all measures to restore the safety and security of the site and are monitoring the site's immediate surroundings.

So unit 2 has had cooling restored. Also, they are discussing modifying the secondary containment structure of unit 2's reactor building so that there cannot be any buildup of hydrogen gas from the venting process of primary containment.

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