Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake(Daily Report as of 3:00 PM on July 10)

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 Fukushima Daiichi Nuclear Power Station.

* 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 3:45 AM on July 5, in the central operation room (hereinafter, COR) of Unit 5, a night-shift worker (a TEPCO employee) who was on a patrol inside the COR found that the standby failure indicator of the generator (B) of the two emergency diesel power generators (hereinafter, D/Gs) was on. (The standby failure indicator is a lamp that indicates that D/G is not in the standby state). The other generator (A) of these D/Gs was found to be in the standby state. A detailed investigation was conducted later, and we found out that the fuel handle of D/G (B) had been displaced from the normal position while the fuel handle of D/G (A) had not. Based on this result, we considered that this incident was caused in the following manner: due to the displacement of the D/G (B) fuel handle, pressing of the fuel handle against the position detection circuit (a limit switch) became insufficient (indicated the off state); and the standby failure indicator was turned on as a result. We will implement the following measures to prevent a recurrence of this incident:
·Near a D/G fuel handle, place a sign that indicates the normal position where the handle should be secured.
·In the operational procedure manual by facility, add a clear description of the normal position where a D/G fuel handle should be secured.
·Provide information on this incident to the operators.
Since the cause was made clear, we returned the fuel handle to the normal position, and confirmed that the standby failure indicator was turned off. At 4:23 PM on the same day, a verification run was started. Then, during a halt operation, we noticed that the air pressure of the air reservoir was low. In order to later investigate the cause of the reduced air pressure of the air reservoir, we have been continuing to keep D/G (B) out of the standby state.
On July 9, the startup electromagnetic valve was opened and checked for the purpose of investigating the cause of the reduced air pressure of the air reservoir with respect to D/G (B) of D/Gs for Unit 5. We found out that hardening and deformation of the pilot seat section (an expendable item) of the electromagnetic valve caused an air leak. It seems that this air leak made it impossible to completely close the electromagnetic valve, and caused the reduction in air pressure. We will make replacement of parts, and conduct a verification run of D/G (B) to verify its soundness.

-At around 1:20 PM on July 10, hydraulic oil was found leaking from a hydraulic cutter of unmanned heavy equipment used for debris removal in the upper part of Unit 3 Reactor Building. Upon being informed of this incident, we inspected the heavy equipment. We found hydraulic oil oozing at the hydraulic hose joint. We covered this part with a protective material against oil, and no oil has been found that dropped to the floor surface of Unit 3 Reactor Building from this covered part.

-Contaminated water transfer from the underground reservoirs was all completed as of July 1. However, we are continuing to take measures to prevent the expansion of contaminated water, and to conduct sampling activities.

<Measures to prevent the expansion of contaminated water>
On June 19, since the decrease of all-β radioactivity density in the leakage detection hole (northeast) at the underground reservoirs No.1 has been slow, an operation to dilute the underground reservoir No.1 by transferring desalination-system (RO) treated water (the all-β radioactivity density: approx. 1×10¹Bq/cm³) into the reservoir was started (the all-β radioactivity density of residual water in the underground reservoir No.1: 6.6×10⁴Bq/cm³).
[Recent dilution operation] On July 5, approx. 40m³ of filtered water was injected.
On June 27, since the decrease of all-β radioactivity density in the leakage detection hole (northeast) at the underground reservoirs No.2 has been slow, an operation to dilute the underground reservoir No.2 by transferring filtered water into the reservoir was started.
[Recent dilution operation] On July 8, approx. 40m³ of desalination-system (RO) treated water was injected.
On July 9, leaked water in the leakage detection holes at the underground reservoirs No.1-No.3 was transferred to the temporary aboveground tank, and leaked water in the drain holes at the underground reservoirs No.1 and No.2 was transferred into these underground reservoirs^*.

<Sampling>
On July 9, sampling was performed in the drain holes of the underground reservoirs No.1-No.7 (14 locations), the leakage detection holes of the underground reservoirs No.1-No.4 and No.6 (sample could not be collected at 2 out of 10 locations), the observation holes of the underground reservoirs (22 locations), the groundwater bypass investigation holes a-c (sample could not be collected at 1 out of 3 locations), the groundwater bypass pump wells No.1-No.4, and the observation holes on the sea side (1)-(4). No significant change was found with the analysis results compared to the analysis results from the sampling performed previously (on July 2 in the groundwater bypass investigation holes a-c, the groundwater bypass pump wells No.1-No.4, and the observation holes on the sea side (1)-(4), and on July 8 in the other locations). Further, analysis for tritium was performed on water sampled on July 1 and 2 in the groundwater bypass (investigation holes a-c and pump wells No.1-No.4; sample could not be collected at 1 investigation hole out of 3 investigation holes) and the observation holes on the sea side (1)-(8). As a result, no significant change was found compared to the previous analysis results (from the sampling on June 24 in the observation holes on the sea side (5)-(8), and on June 25 in the other locations).

-We installed observation holes east of the Unit 1-4 Turbine Buildings, and have been conducting sampling and analysis of groundwater from the observation holes. On June 19, we announced that tritium and strontium were detected at high densities in the observation hole located between Units 1 and 2. Therefore, we have been conducting intensified monitoring.
On July 9, analyses for the γ nuclides and all-β were conducted on water in the newly installed groundwater observation hole No.1-4 (north of the groundwater observation hole No.1) and the groundwater observation holes No.1-2 and No.2. As a result, cesium-134, cesium-137, and all-β in the groundwater observation hole No.1-4 water were detected at 1.5Bq/L, 3.6Bq/L, and 330Bq/L, respectively, which are not high values compared to the other groundwater observation holes. In the groundwater observation hole No.1-2 water, cesium-134 and cesium-137 were detected at 11,000Bq/L and 22,000Bq/L (9,000Bq/L and 18,000Bq/L in the previous analysis (on the sample taken on July 8)), respectively. All-β in the groundwater observation hole No.2 was detected at 910Bq/L (1,700Bq/L in the previous analysis (on the sample taken on July 8)).

* There has been a mistranslation in the part starting with "leaked water in the drain holes". This part has been corrected from "leaked water in the drain holes at the underground reservoir No.2 was transferred into this underground reservoir" (corrected on July 16). We apologize for the mistranslation.

* Revised past progress

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