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
* On May 8, gas sampling was conducted at Unit 2 PCV gas control system. Upon analysis, xenon 135 measured at the system entrance was below the detection limit (1.0x10-1Bq/cm3) and the re-criticality criteria (1 Bq/cm3).
* At 11:13 AM on April 29, the spent fuel pool desalting facility was stopped automatically because of an alert notifying an abnormality found with the electrodialyzer. The interlock arrangement closed all the isolation valves in the system, and the alternative cooling system for the spent fuel pool continues its operation. Therefore, there is no impact on the cooling. As a result of site investigation, there was no water leak from this system. As the clogging occurring in the electrodialyzer seemed to be causing the alert to go off, the electrodialyzer was isolated from the system. At 5:39 PM on the same day, the operation was restarted by RO unit independently. Upon investigation, it was found that during the operation after replacing the electrodialyzer filter (on April 28), the balance between the dilution water reprocessing the wastewater of the electrodialyzer (RO treatment water) and the concentrated water was lost. This caused the calcium component dissolved in the pool water to go over the solubility limit, creating the situation in which the deposition such as calcium carbonate is easily precipitated on the ion-exchange membrane. As a result of this, the amount of water in the electrodialyzer fluctuated causing the pump to stop operating. Cleaning operation (cycle operation in the electrodialyzer utilizing dilute hydrochloric acid) was conducted In order to remove the precipitated deposition. On May 8, test operation was conducted and no problem was found. At 3:30 PM on May 9, operation was restarted accordingly.
* At 10:00 AM on May 9, we started transferring the accumulated water from Unit 6 Turbine Building basement to the temporary tank. At 4:00 PM on the same day, we stopped transferring.
* At 8:02 AM on May 9, the operation was temporarily stopped at the 2nd Cesium Adsorption Apparatus in order to backwash the filter. After that, the water supply for the apparatus was switched from the Centralized Radiation Waste Treatment Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building [High Temperature Incinerator Building]) to the Centralized Radiation Waste Treatment Facility (Process Main Building). At 5:29 PM on the same day, the apparatus was restarted. At 5:50 PM on the same day, steady flow level (Approx. 40.0m3/h) was achieved.
* Around 12:45 PM on May 9, a monitoring camera caught water squirting near the filtrate water transfer pump room located in front of the former Administration Office Building. At 1:00 PM, the pump was stopped and at 1:07 PM, the filtrate water supply valve was closed. At 1:03 PM, it was confirmed that the water leak had stopped through the monitoring camera. The surface dose rate of the leaked water was approximately 300-400μSv/h, which was equivalent to the atmosphere dose rate. Upon investigation, we found that a crack on the hose connected to the pump (for filtrate water) was causing the water leak. As the leaked water was filtrate water and it did not flow downstream of the gutter or near the water leak spot, it has been concluded that there was no water leak outside the site. At 4:00 PM on the same day, the hose was replaced and there was no more water leak.
* At 1:30 PM on May 10, hydrazine injection (utilizing the circulating cooling equipment) into Unit 3 spent fuel pool was started.
[Fukushima Daini Nuclear Power Station]
●Unit 1 to 4: Shutdown due to the earthquake
Appendix::
Past Progress (As of 3:00 pm, on May 10, 2012) (PDF 311KB)
Appendix::
Past Progress (From March 11, 2011 to December 31, 2011) (PDF 460KB)
*
Revised past progress
