Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake(Daily Report as of 3:00 PM on July 6)

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

- As for the underground reservoir No.2 installed within the power station site, 10¹Bq/cm³ level of radiation was detected as a result of analyzing the water accumulated between the sheet on the outside (bentonite sheet) and the ground (the underground reservoir is made of three layers of impermeable sheets) on April 3. On April 5, radiation was detected in the water between the sheet on the outside (bentonite sheet) and the sheet on the inside (double-layered permeable sheet) as a result of analysis. The radioactivity density of all β detected was approx. 5.9×10³Bq/cm³. Considering that there is no drain ditch in the surrounding area, it is considered that there is no possibility of the leaked water flowing into the sea. At 5:10 AM on April 6, the incident was judged to be a leakage which is subject to the application of Article 19-17, Item 10 of the Rule for the Installation, Operation, etc. of Commercial Nuclear Power Reactors (Rule for Commercial Nuclear Power Reactors). The amount of leaked water is approx. 120m³, all γ radioactivity density is approx. 1.5×10⁰Bq/cm³ and all β radioactivity density is approx. 5.9×10³Bq/cm³, the γ ray radiation dose leaked is estimated to be approx. 1.8×10⁸Bq and the β radiation dose is estimated to be approx. 7.1×10¹¹Bq. Details are currently being investigated.
While enhancing the monitoring of the water level of the underground reservoir No.3, on April 7, sampling was performed on the water in the drain hole (southwest) and the leakage detection hole (southwest) of the underground reservoir No.3 for the purpose of investigating the leakage location.
Considering that all β nuclides were detected in the water in the leakage detection hole and the drain hole of the underground reservoir No.3 as a result of sampling, it was judged at 8:53 AM on the same day that there may be a small amount of leakage from the impermeable sheet on the outside (bentonite sheet) of the reservoir to the outside.
The samples collected in the morning of April 9 in the drain hole (at 2 locations) and the leakage detection hole (at 2 locations) of the underground reservoir No.1 have been analyzed. As a result, the chloride concentration of the water in the leakage detection hole (northeast) has increased from 4ppm (on the previous day) to 910ppm. At 12:47 PM, water transfer from the underground reservoir No.2 to No.1 utilizing temporary pumps was suspended. Considering that all β nuclides were detected as a result of sampling performed in the leakage detection hole of the underground reservoir No.1 for the purpose of investigating the leakage location, it was judged that there may be a small amount of leakage from the sheet on the inside (double -layer impermeable sheet) to the impermeable sheet on the outside (bentonite sheet) of the reservoir although the water level of the underground reservoir No.1 has not decreased and the analysis results of the drain hole water of the underground No.1 have not yet been confirmed.
On April 10, the soil covering the leakage detection hole (northeast) penetration of the underground reservoir No.2 was removed to perform a visual inspection of the penetration. The removal of the impermeable sheet, gravels, etc. will be continued. Furthermore, drilling work was started for the boring investigation to confirm the contamination condition of the surrounding area of the underground reservoirs and contamination expansion to the sea side. The work will be continued. Though water transfer from the underground reservoir No.3 to No.6 was started at 2:00 PM on the same day, the transfer pump was stopped at 2:03 PM as water leakage from the connection part (flange) of the transfer pump outlet pipe was found. The pipe flange was disassembled for cause investigation. As a result, the cause was identified to be the problem with the flange connection part (inhomogeneous amount of gap on the surfaces). The flange was recovered after replacing the gasket. Since no problem was found as a result of measuring the gaps on other flanges and checking the tightening condition of the flange bolts, the water transfer was started at 9:56 PM on April 12. As for the removal of the soil covering the upper part of the reservoir (embankment) where the leaked water is assumed to have been absorbed, further drilling was performed (a total of the drilling depth: 30-60cm) and the radioactivity density on the ground surface has been reduced down to 0.05mSv/h (β＋γ) (max.). At 3:06 PM on April 14, the water transfer from the underground reservoir No.3 to No.6 was suspended as the transfer of the planned water amount had completed.
On April 12, sampling was performed in the drain holes of the underground reservoirs No.1-7 (at 14 locations) and the leakage detection holes of the underground reservoirs No.1-4 and 6 (sample could not be collected at 2 out of 10 locations). As a result, the all β density in the drain hole (northeast) of the underground reservoir No.1 was found to have increased during the period from April 10 to 12. Thus, it was judged that there has been a small amount of leakage from the sheet on the outside (bentonite sheet) to the outside. Since there is no drainage in the surrounding area, there is no possibility that the leaked water has flowed out to the sea.
On April 19, the filtrate water tank No.1 was detached from the transfer line between the buffer tank and the filtrate water tanks No.1/No.2 in order to prepare for the water transfer from the underground reservoir No.1 to the filtrate water tank.

<Measures to prevent the expansion of contaminated water>
On July 5, leaked water in the leakage detection holes at the underground reservoirs No.1-No.3 was transferred to the notch tank, and leaked water in the drain holes at the underground reservoir No.2 was transferred into this underground reservoir.
Meanwhile, 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).
[Dilution operation records] The volumes of injected desalination-system (RO) treated water were approx. 24m³ on June 19 and approx. 16m³ on June 20. On June 21, approx. 40m³ of the water was transferred to a temporary tank. On June 26, approx. 40m³ of desalination-system (RO) treated water was injected. On June 27, approx. 33m³ of the water was transferred to the temporary tank. On June 28, approx. 40m³ of desalination-system (RO) treated water was injected. On July 1, approx. 40m³ of the water was transferred to the temporary tank. On July 2, approx. 40m³ of desalination-system (RO) treated water was injected. 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.
[Dilution operation records] On June 27, approx. 40m³ of filtered water was injected. On July 2, approx. 40m³ of the water was transferred to a temporary tank.

<Sampling>
On July 5, 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), and the observation holes of the underground reservoirs (22 locations). No significant change was found with the analysis results compared to the analysis results from the sampling performed previously (on July 4).

- 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, as follows:
- Tritium: 4.6-5.0×10⁵Bq/L (Sampling dates: May 24 and 31, and June 7)
- Strontium-90: 8.9×10²-1×10³Bq/L (Sampling dates: May 24 and 31)
We also announced that we would continue the sampling and analysis, and conduct intensified monitoring.
Analysis for tritium was conducted on water sampled on July 4 in the groundwater observation holes No.1-No.3. As a result of the analysis, no significant change was found compared to the previous results (from sampling on July 1 in No.1 and No.2, and on June 26 in No.3).
Analysis for tritium was conducted on seawater sampled on July 3 in the Unit 1-4 water intake north side and between the water intakes of Units 1 and 2 (near the surface and near the bottom). As a result of the analysis, tritium in seawater in the Unit 1-4 water intake north side was detected at 2,300Bq/L, which is higher than the past highest value (2,200Bq/L in the sample taken on July 1). No significant change was found with the other results compared to the previous results (from sampling on July 1).
Analyses for the γ nuclides and all-β were conducted on samples taken on July 5 from water in the groundwater observation hole No.1-1 and the groundwater observation hole No.1-2 and from seawater in the Unit 1-4 water intake north side and between the water intakes of Units 1 and 2 (near the surface and near the bottom). As a result of the analyses, high γ nuclide and all-β densities were detected in the sample taken from the groundwater observation hole No.1-2 compared to those in the groundwater observation holes No.1 and No.1-1. No significant change was found with the other results compared to the previous results (from sampling on July 3).

- 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 are continuing to keep the D/G (B) out of the standby state.

* Revised past progress

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