Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM, March 14)

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

-At 10:00 AM on March 14, we started transferring the accumulated water in Unit 6 Turbine Building basement to the temporary tank. At 3:00 PM on the same day, the transfer was stopped.

-At 4:09 AM on January 30, 2013, a cooperative company worker reported to a TEPCO employee that water leakage was found in the temporary warehouse where desalination system No.2 (reverse osmosis membrane) is installed at Fukushima Daiichi Nuclear Power Station. Since the pressure of the system was high, a cooperative company worker performed flushing. When flushing was completed at 4:00 AM, the worker found water leakage around the system while he was preparing to start the system. At 5:00 AM, a TEPCO employee confirmed that the leakage had stopped. The area affected by the leakage was approx. 1.5mx20mx1mm. The leaked water remains in the system dam and has not flowed outside of the temporary warehouse. The amount of leaked water was approx. 30L. As a result of atmosphere dose rate measurement, γ+β was 0.1mSv/h and γ was 0.035mSv/h. The radioactivity density measurement results were as follows. Cesium 134: 7.0×10^-1Bq/cm³, cesium 137: 1.3×10⁰Bq/cm³, stibium 125: 9.4×10⁰Bq/cm³, which are equivalent with those of water sampled at the entrance of the desalination system. Upon site investigation, the leakage location was identified to be the outlet of the safety valve installed on the discharge side of the high pressure pump of the desalination system. The leakage has no impact on reactor water injection considering that there is a sufficient amount of desalinated water and other desalination systems are available for operation. As a result of cause investigation, it was found that when the inlet pressure of the RO membrane increases, the high pressure pump is stopped and the RO membrane inlet pressure switch which activates an alarm operates at 6.1-6.3 MPa (as it is set to operate). Also, it was confirmed that there are cases where the high pressure pump outlet safety valve of the desalination system No.2 (reverse membrane) operates at 6.2MPa though it is set to operate at 6.6MPa. Since the leakage occurred near the timing of RO membrane replacement and the high pressure pump outlet pressure then was close to 6.2MPa (which may activate the safety valve), the RO membrane inlet pressure switch got activated and the outlet safety valve started operating before the pump was suspended, which in turn is assumed to have led to the leakage. As countermeasure, the RO membrane inlet pressure switch has been set to operate at 5.5MPa and setting was done to suspend the high pressure pump and activate an alarm at an early timing. Also, the high pressure pump outlet safety valve was recalibrated to operate at 6.6MPa. Furthermore, a drain line has been installed on the exhaust side of the high pressure pump outlet safety valve for the purpose of preventing contaminated water to spread onto the floor surface in the case that the high pressure pump outlet safety valve operates. As the implementation of the above countermeasures has been completed, trial operation was carried out on March 14. After confirming no problem with its operation, the system was put in standby state.

[Fukushima Daini Nuclear Power Station]
·Unit 1 to 4: Shutdown due to the earthquake.

* Revised past progress

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