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).
*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
* On May 16, sampling was done at Unit 2 PCV gas control system. As a result, xenon 135 detected at the entrance of the system was below the detection limit (1.0x10-1Bq/cm3) and the re-criticality criteria (1Bq/cm3).
* At 1:30 PM on May 16, we found that data was missing in the portable monitoring post at the main entrance of the power station. Upon investigation, it was assumed that the issue is caused by abnormality of the transmission system between the Main Anti-Earthquake Building and the monitoring post, as the reading was confirmed. At 3:00 PM on the same day, the monitoring panel was reset for recovery and the monitoring post started working properly. The missing data (at 2:00 PM and 2:30 PM) was acquired by dose rate measurement, and the result showed the same level of dose rate as that of before the issue arose (Approx. 22μSv/h). At around 4:30 PM on the same day, data reading was failing on the Main Anti-Earthquake Building monitoring panel of the portable monitoring posts at the main entrance and west entrance. At 6:00 PM on the same day, the transmission of the portable monitoring post at the main gate was recovered. As for the monitoring post at the west entrance, alternative measurement was done by a worker, and monitoring was continued utilizing a wireless monitoring post system during the night. At 11:35 AM on May 17, the monitoring post at the west entrance was recovered after a worker wiped off the water on the cable connection part and removed and inserted the cable. At 12:30 PM on the same day, the data reading on the Main Anti-Earthquake Building monitoring panel failed again. At 12:55 PM, the issue was resolved by resetting the monitoring panel. As the data acquired at 12:30 PM and later was confirmed on the wireless monitoring post system, there was no missing data. The cause of the issue on the monitoring post at the main entrance is considered to be a temporary transmission system issue. The issue on the monitoring post at the west entrance seems to be caused by a bad cable connection and a temporary transmission system issue. All data except for that of 1:30 PM on May 16 was acquired by an alternative measurement (at both the main entrance and west entrance). We will continue to monitor these equipments by checking the data updates every 30 minutes. At 9:20 PM on May 17, the data of the portable monitoring post at the west entrance could not be confirmed on the Main Anti-Earthquake Building monitoring panel. Though the receiving terminal panel was reset, transmission did not recover. Data acquired at 9:30 PM on May 17 and later is being monitored by a wireless monitoring system. The cause of this issue is currently under investigation.
* At 2:20 PM on May 15, as to the exhaust inside the Unit 6 Primary Containment Vessel (PCV) which had been conducted by opening the equipment hatch before, in order to do it directly from PCV, we started up PCV fan which had been stopped after the earthquake. Until 2:46 PM on May 16, PCV fan continued operating for a short period of time. Upon our analysis of γ nuclides measurement result (at the main exhaust stack), it was confirmed that the fan operation did not negatively affect the detection level. At 2:12 PM on May 18, the fan was restarted for a continuous run.
* At 2:23 PM on May 18, we found that the water injection amount to Unit 2 reactor was decreasing. The amounts of water injected from the water supply system (from 2.9m3/h to 3.0m3/h) and the reactor core spray system (from 5.5 m3/h to 6.0 m3/h) were increased accordingly.
[Fukushima Daini Nuclear Power Station]
·Unit 1 to 4: Shutdown due to the earthquake
Appendix:
Past Progress (As of 3:00 pm, on May 18, 2012) (PDF 319KB)
Appendix:
Past Progress (From March 11, 2011 to December 31, 2011) (PDF 460KB)
*
Revised past progress
