Due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake which occurred on March 11, 2011, TEPCO's facilities including our nuclear power stations have been severely damaged. We deeply apologize for the anxiety and inconvenience caused.
With regard to the accident at Fukushima Daiichi Nuclear Power Station, on April 17, 2011, we have compiled the roadmap towards restoration from the accident and on July 19 we accomplished the Step1 target "Radiation dose is in steady decline". Then on December 16 we confirmed the accomplishment of the Step 2 target "Release of radioactive materials is under control and radiation doses are being significantly held down".
In addition, on December 21, 2011, we have compiled the "Mid-to-long-Term Roadmap toward the Decommissioning of Fukushima Daiichi Nuclear Power Units 1-4, TEPCO".
In addition to the maintenance of the plant's stable condition, we will implement Mid-to-Long Term countermeasures towards the decommissioning of Fukushima Daiichi Nuclear Power Units 1-4 to enable evacuees to return to their homes as soon as possible and reduce the anxiety of the people in Fukushima and the whole nation as soon as possible.
Below is the status of TEPCO's nuclear power stations (Fukushima Daiichi and Fukushima Daini).
* The updates are underlined.
[Fukushima Daiichi Nuclear Power Station]
·Unit 1 to 4: Abolishment (April 19, 2012)
·Unit 5 to 6: Outage due to regular inspections before the earthquake
-A worker of TEPCO confirmed that the fluctuation in the amount of water injection for Unit 1 - 3 reactor at 3:00 PM on August 30 at the regular data confirmation.
Unit 1: The amount of water injection from 4.9m3/h (at 2:00 PM) to 4.0m3/h.
(The required amount of water injection was 4.3m3/h.)
Unit 2: The amount of water injection from 7.0m3/h (at 2:00 PM) to 5.5m3/h.
(The required amount of water injection was 6.1m3/h.)
Unit 3: The amount of water injection from 7.0m3/h (at 2:00 PM) to 5.6m3/h.
(The required amount of water injection was 6.1m3/h.)
The shift supervisor judged that the condition did not satisfy the "Operational Requirements"*1 defined by the Technical Specification*2 for Unit 2 at 3:00 PM, for Unit 3 at 3:05 PM and for Unit 1 at 3:07 on the same day. Though we attempted to increase the water injection amounts at the site, the amounts kept decreasing. The water injection amounts were continuously monitored and have been adjusted as below. As a result of site investigation, no water leakage from the reactor injection system was found.
We checked the air intrusion into regular reactor injection water pump on the hill (B) and (C) which were in operation when the injection amounts started decreasing, and no air intrusion was found. Since there was a possibility that any dust and foreign material etc. attached to the flow control valve, we conducted a flushing work on August 31. We continuously monitored the amount of water injection after the flushing work, and we confirmed the fluctuation continuously.
(The required amounts of water injection for each unit were adjusted on September 1 as follows:
Unit 1: 3.8m3/h, Unit 2: 5.4m3/h, Unit 2: 5.4 m3/h )
From 2:30 PM to 3:35 PM on September 2, we opened the flow control valve of each unit more widely as part of the cause investigation of the fluctuation, and we prevented an adhesion of foreign material. For this work, the amounts of water injection of each unit are kept at constant amount due to the retransferring a part of the water which is injected to the reactor to buffer tank. We adjusted the amount of water injection of each unit with this work as follows.
At 3:35 PM on September 2
[Unit 1] Feed-water system: Increased from 2.6m3/h to 3.0m3/h, Reactor core spray system: Increased from 1.8m3/h to 2.0m3/h (In total, the amount was increased from 4.4m3/h to 5.0m3/h.)
[Unit 2] Feed-water system: Increased from 1.9m3/h to 2.0m3/h, Reactor core spray system: No change (5.0m3/h) (In total, the amount was increased from 6.9m3/h to 7.0m3/h.)
[Unit 3] Feed-water system: Increased from 2.0m3/h to 2.5m3/h, Reactor core spray system: No change (4.5m3/h) (In total, the amount was increased from 6.5m3/h to 7.0m3/h.)
We continuously monitored the amount of water injection. Since we confirmed the fluctuation continuously, we adjusted the amount of water injection as follows.
At 6:56 AM on September 3
[Unit 1] Feed-water system: Increased from 2.9m3/h to 3.0m3/h, Reactor core spray system: Increased from 1.6m3/h to 2.0m3/h (In total, the amount was increased from 4.5m3/h to 5.0m3/h.)
[Unit 2] Feed-water system: Increased from 1.5m3/h to 2.0m3/h, Reactor core spray system: Decreased from 5.1m3/h to 5.0m3/h (In total, the amount was increased from 6.6m3/h to 7.0m3/h.)
[Unit 3] Feed-water system: Increased from 2.0m3/h to 2.5m3/h, Reactor core spray system: Decreased from 4.9m3/h to 4.5m3/h (In total, the amount was increased from 6.9m3/h to 7.0m3/h.)
The cause of this matter will be investigated and the water injection amounts will be continuously monitored. No change has been seen with the bottom of RSV of each unit, and no significant change is found in the monitoring post data.
-At 10:02 AM on September 1, we started transferring the accumulated water from Unit 2 Turbine Building basement to Unit 3 Turbine Building basement. At 8:23 AM on September 3, we stopped transferring.
-At 10:00 AM on September 3, we started transferring the accumulated water in Unit 6 Turbine Building basement to the temporary tank. At 3:00 PM on the same day, we stopped transferring.
[ Fukushima Daini Nuclear Power Station ]
·Unit 1 to 4: Shutdown due to the earthquake.
Appendix:
Past Progress (As of 3:00 pm, on September 3, 2012) (PDF 511KB)
Appendix:
Past Progress (From March 11, 2011 to December 31, 2011) (PDF 523KB)
*
Revised past progress
The aforementioned attachments are only available in Japanese.
We apologize for any inconvenience this may cause.
