Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 5:00 PM, April 5)

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 around 5:23 AM on April 4, the multi-nuclide removal equipment (ALPS) for which hot testing using waste liquid treated by the contaminated water treatment facility was being performed has been suspended due to incorrect operation. Since no abnormality was found as a result of site investigation performed after the incident, the treatment of water remaining in the system was started at 6:33 AM on the same day. No problem has been found with its operation after starting the treatment of the remaining water. At 6:54 PM on the same day, the treatment of water remaining in the system was completed.

-At 10:29 AM on April 5, we started transferring the accumulated water in Unit 2 Turbine Building basement to the Central Radioactive Waste Treatment Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building [High Temperature Incinerator Building]).

-At around 12:55 PM on April 5, a TEPCO employee inspecting No.1 heater of the Standby Liquid Control System Tank A found cable discoloration and a burn on the terminal block of No.2 heater. At 1:05 PM on the same day, the incident was reported to Futaba Fire Department. In response to the cable discoloration and a burn found on the terminal block of No.2 heater of the Standby Liquid Control System Tank A, the heater was switched to No.1 heater and the temperature control of the boric acid solution in the Standby Liquid Control System Tank A was restarted at 1:45 PM on the same day. No problem was found with No.1 heater operation. Though the temperature of boric acid solution has increased from approx. 15℃ (before temperature control was suspended) to approx. 18℃ as a result of performing an operation check of No.1 heater (energization check), there is a sufficient margin to the maximum allowed value of approx. 4℃ (boric acid solution temperature relative to the solubility of boric acid solution). At 3:30 PM on the same day, Tomioka Fire Department has judged that the incident was not a fire.
*Standby Liquid Control System: Boric acid is capable of absorbing neutrons. The Standby Liquid Control System is used for injecting boric acid in the case of (possible) recriticality of the fuel debris in the RPV or the PCV in order to ensure subcriticality or prevent recriticality. The boric acid solution is kept warm to prevent the dissolved boric acid from being precipitated. The system is in standby for emergency use and is not normally used for reactor cooling. There are two Standby Liquid Control System tanks next to the reactor water injection pump on the hill.

-At around 2:27 PM on April 5, an alarm indicating a power board failure related to power supply went off and Unit 3 spent fuel pool alternative cooling system was confirmed to be suspended. As a result of insulation resistance test performed on the power supply facilities affected by the suspension from 3:50 PM to 4:00 PM, no abnormality was found. From 4:16 PM, operation to restart the system was started. Considering that a countermeasure against small animals (installation of entry prevention net) was being implemented on the power board of the concerned system, there is a high possibility that a ground fault had occurred during the work. The temperature of Unit 3 spent fuel pool as of 2:00 PM on the same day was 15.1℃ and the temperature increase rate as of April 5 is approx. 0.145℃/h. The amount of time to reach the maximum allowed temperature stipulated by the technical specification (65℃) is estimated to be approx. 2 weeks. No fluctuation of monitoring post data has been found at the moment.

-As for the hole drilled on the ceiling of Unit 5 Reactor Building on March 18, 2011 for the purpose of preventing hydrogen explosion, considering that cold shutdown is being maintained and the plant condition has been stable at Unit 5, work to close the hole has been started on March 16 in order to maintain the air tightness of the building. At 1:00 PM on March 19, the work has been completed. As a result of air tightness check performed from 3:03 PM to 3:37 PM on April 5, no problem was found.

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

* Revised past progress

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