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.
(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 )
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. We continuously monitor the amount of water injection after this work, and adjust it arbitrarily.
From 11:55 AM to 1:00 PM on September 4, we removed the spool installed on the pump inlet side of stand-by regular reactor injection water pump on the hill (C), and conducted the inside inspection. From 12:00 PM to 12:50 PM, we confirmed some foreign materials attached to the strainers installed at the entrance of the refrigerators for buffer tank water cooling (2 out of 6 refrigerators). Though no foreign material etc. was found inside the inlet pipe of regular reactor injection water pump on the hill (C), some (brown and white) were found at the strainers installed at the entrance of refrigerators for buffer tank water cooling.
We continuously monitored the amount of water injection. Since the amount kept decreasing, we adjusted the amount of water injection as follows.
At 10:30 AM on September 5
[Unit 2] Feed-water system: Increased from 1.2m3/h to 2.0m3/h, Reactor core spray system: No change (5.0m3/h) (In total, the amount was increased from 6.2m3/h to 7.0m3/h.)
[Unit 3] Feed-water system: Increased from 4.3m3/h to 4.5m3/h, Reactor core spray system: Increased from 2.0m3/h to 2.5m3/h (In total, the amount was increased from 6.3m3/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 10:30 AM on September 4, in order to examine the case of the intermittent increase in hydrogen density and noble gas (Krypton-85) density measured by Unit 1 RCV gas control system, we injected the nitrogen to the upper part of the pressure suppression chamber in which hydrogen is supposed to be accumulated from the nitrogen injection line laid on the 1st floor of reactor building, and pushed out the accumulating hydrogen and the Krypton-85. We accordingly started confirming the presence of hydrogen and Krypton-85 at the upper part of the pressure suppression chamber utilizing the gas control system. At 4:37 PM on the same day, we stopped the nitrogen injection to the upper part of the pressure suppression chamber. The hydrogen density of Unit 1 RCV was 0.54% as a result of this work (as of 11:00 AM on September 5). Since it is below the flammability limit (4%), there is no problem.
- At 4:15 PM on August 30, we started transferring the accumulated water from Unit 4 Turbine Building basement to the Central Radioactive Waste Treatment Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building [High Temperature Incinerator Building]). At 5:18 PM on September 4, we stopped transferring. At 5:31 PM, we restarted transferring.
- On September 4, dust sampling was conducted at Unit 2 Reactor Building opening (blow-out panel).
- On September 4, sampling was conducted at the charcoal filter and the particulate filter of Unit 2 PCV gas control system.
- At 4:25 AM on September 5, the alarm which indicated an overload trip at the station power source went off at the Main Anti-Earthquake Building, and we confirmed that the power sources for the main gate, west gate and corporate welfare building were turned off. Since we could not use the continuous dust monitor at the main gate due to this, the operations of omission of full face mask wearing was temporarily suspended. We switched to an alternate power source, and the continuous dust monitor was recovered. We restarted the omission of full face mask wearing at 6:15 AM. For reference, there was no impact on Unit 1 - 6 plants, and there was no effect on the values of each parameter and monitoring post.
- At 10:00 AM on September 5, 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.
Past Progress (As of 3:00 pm, on September 5, 2012) (PDF 516KB)
Past Progress (From March 11, 2011 to December 31, 2011)
* Revised past progress
The aforementioned attachments are only available in Japanese.
We apologize for any inconvenience this may cause.