Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM on July 11)

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.
Later, we replaced the pilot seat section with a new one in the startup electromagnetic valve of D/G (B), and conducted a verification run, which showed no abnormality. At 5:13 on July 10, D/G (B) was switched to the standby state from the out-of-standby state.

- At around 9:02 AM on July 11, the right-side filter of a full-face mask being worn by a worker, who was working on construction of the main structure of the cesium absorption tower temporary storage facility (fourth facility), was found missing from the mask. A contamination survey was conducted on the facial surface of the worker, and no contamination was found. Thereafter, the worker underwent whole body counting and was found to have no abnormality. The filter missing from the full-face mask was found in a Tyvek protective suit that the worker took off at a changing room in Welfare Building.

- At 6:47 AM on July 8, operation of the Unit 3 spent fuel pool alternative cooling system was suspended due to inspection on instruments of the cooling system (the pool water temperature was 26.6℃ at the start of the suspension). At 10:44 AM on July 11, the cooling system was started up (the pool water temperature was 32.6℃ at the startup). No abnormality has been found regarding the operation status of the spent fuel pool alternative cooling system.

- As for Units 5 and 6 where the buildings and the outdoor trenches were flooded due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake, we have been transferring the accumulated water in the buildings in order to prevent water level increases in the buildings. On January 28, for the purpose of further enhancing safety, we started transferring the accumulated water in the outdoor trench of the emergency gas treatment system* to the temporary tank. Thereafter, since the water levels did not stop increasing, we stopped the work to remove accumulated water and started investigation. The investigation made it clear that there may be inflow of water from nearby sub-drains. Therefore, on July 10, we started work to shut off the inflow from the sub-drains after removing water again from both of the trenches and sub-drains (the water shutoff work itself is expected to take approximately 2 months). In the meantime, water removal from the outdoor trench of the emergency gas treatment system of Units 5 and 6 was completed by transferring water to the temporary tank from 8:05 AM on July 10 to 0:10 PM on July 11. After the completion of the transfer, we checked the site and found no abnormality such as leakage. With regards the emergency gas treatment system exhaust line located inside the outdoor trench of the emergency gas treatment system, we will conduct an inspection of the piping as soon as we complete the preparation.
* System comprised of two lines (A) and (B), which purifies the air in the Reactor Building utilizing high performance filter and discharges it from the exhaust stack.

- At around 1:20 PM on July 11, in the upper part of Unit 3 Reactor Building, a worker found hydraulic oil leaking from unmanned heavy equipment used for debris removal. At around 1:43 PM, this incident was reported to the fire department. This heavy equipment was lifted down to the ground from the upper part of Unit 3 Reactor Building. Then, at 1:55 PM, oil leakage was confirmed to have stopped. Further, the heavy equipment was placed on a drain pan temporarily just in case. Later, we checked the heavy equipment, and found out that oil leaked from the hydraulic hose joint above the hydraulic cutter. Through a camera, no trace of leakage was found in the operation floor. We consider that there was no inflow of the oil into the spent fuel pool, since the unmanned heavy equipment and the spent fuel pool were distant from each other.

- 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 10, approx. 54m³ of water was transferred to the temporary tank.
On July 10, 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 10, 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). In 4 observation holes (A13, A 14, A16 and A19) around the underground reservoir No.1, all-β was detected at densities about twice to five times of the detection limit value (approx. 3.2×10^-2Bq/L). No significant change was found with the other analysis results compared to the analysis results from the previous sampling (on July 9). Further, analysis for tritium was performed on water sampled on July 3 in the drain holes and leakage detection holes of the underground reservoirs No.1-No.4 and No.6 (the analysis is performed once a week). As a result, no significant change was found compared to the previous analysis results (from the sampling on June 26).

- 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)).
It seemed that water sampled on July 8 and 9 may contain suspended solids (such as a very small amount of dirt), we removed the suspended solids and conducted reanalysis on July 10, which resulted in values at the same levels as those detected from the samples taken on July 5.
Analysis for tritium was conducted on samples taken on July 8 in the groundwater observation hole No.1-2, the newly installed groundwater observation hole No.1-4 (north of the groundwater observation hole No.1), and the groundwater observation hole No.2. As a result, the tritium density in the groundwater observation hole No.1-4 was 69,000Bq/L, which was lower than those in the groundwater observation holes No.1, No.1-1, and No. 1-2.

* 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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