Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM on July 23)

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 8:20 AM on July 18, an associated company worker, investigating the site using a camera ahead of debris removal work, encountered a steam-like gas wafting through the air near the central part of the fifth floor (equipment storage pool side) of Unit 3 Reactor Building. No significant change was found in the main parameters related to the plant (temperature, pressure and xenon density of PCV/RPV). Neither was any significant fluctuation found in the monitoring post readings or the continuous dust monitor amounts. At 9:20 AM on the same day, the subcritical state was found being maintained. With regards the measurement result of ambient dose on the upper part of the spent fuel pool protection at Unit 3 Reactor Building, no remarkable change was found compared to the measurement result so far obtained every day before work.
All of the values obtained from dust sampling conducted on the same day in the north side (where the sampling was performed twice) and the northeast side of a space over the reactor at Unit 3 Reactor Building fell within the fluctuation ranges observed during the past half year.
Given the dust sampling results and the status of the plant, we consider that the steam was generated due to rainwater having leaked through gaps near the well cover and having been heated at the head of the primary containment vessel.
At 7:55 AM on July 19, no steam-like gas was found when we investigated through a camera the site where a steam-like gas was wafting.
On the same day, the temperatures near the site were measured and found to be in the range of 20.8-22.3℃ (between 1:44 and 2:54 PM). The outside air temperatures were 21.4℃ (as at 1:40 PM) and 20.1℃ (as at 3:00 PM).
On July 20, the third and fourth rounds of dust sampling were conducted in the north side of the space over the reactor at Unit 3 Reactor Building, and dust sampling was also conducted in the northeast side of the space over the reactor (where the sampling is regularly conducted). As a result, we found that all of the thus obtained values were at levels equivalent to or lower than the levels in the previous measurement (on July 18) and fell within the fluctuation ranges observed during the past half year. Additionally, between 0:39 and 2:40 PM on the same day, an area around the site was measured using infrared thermography. As a result, we found that the temperature of the site where a steam-like gas was wafting was approx. 18-25℃ and at about the same level as the air temperature of the same day (Reference: the air temperature and humidity as at 2:00 PM on July 20 were 21.4℃ and 76%).
At around 9:05 AM on July 23, steam wafting at the site was again observed through a camera. As at 9:30 AM on the same day, no abnormality was found in the plant status, the monitoring post readings, etc. Later, the steam was observed intermittently, but not observed between 1:30 and 2:30 PM. We determined that the steam had disappeared.

-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) or filtered water 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 20, approx. 60m³ 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 or desalination-system (RO) treated water (the all-β radioactivity density: approx. 1×10¹Bq/cm³) into the reservoir was started.
[Recent dilution operation] On July 22, approx. 60m³ of water was transferred to a temporary tank.

On July 22, 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 22, 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), and the observation holes on the sea side (5)-(8). As a result of the analysis, no significant change was found compared to the analysis results from the sampling performed previously (on July 15 in the observation holes on the sea side (5)-(8) and on July 21 in the other locations).

-At around 5:00 AM on July 22, an associated company worker found oil leaking near a high-pressure pump of the desalination system 3 (reverse osmosis membrane). The high-pressure pump was suspended, and the oil leakage was confirmed to have been stopped. The leaked oil is lubricating oil, and amounts to approx. 1.5 liters (approx.1.5m × approx. 1m × approx. 1mm). The oil has not flowed out of a concrete floor provided with a dike. At 5:45 AM on the same day, the incident was reported to Tomioka fire station. Then, at around 11:30 AM on the same day, the leaked oil was completely wiped out. Later, we conducted an on-site cause investigation, based on which the oil leakage is considered to have occurred due to deformation of the oil filler cap and the oil gauge, which is attributable to heat up of a pump drive section due to such reasons as degradation of the high-pressure pump lubricating oil. We will replace the pump with a new one. Additionally, with regards the other 3 high-pressure pumps of the same type as the impaired pump, we will replace the lubricating oil and then conduct test operation to verify that these pumps can operate in a normal manner. Further, we will conduct inspection and replacement of high-pressure pump lubricating oil at the right times. The amount of the leaked oil was reconfirmed in the on-site investigation, and was found to be approx. 8 liters (approx.2.5m × approx. 1m × approx. 3mm).

At around 6:40 AM on July 23, a TEPCO employee on patrol found oil leaking in a trench under the actuation valve oil injection tank of the Unit 6 emergency diesel generator (B) main body. As a result of an on-site confirmation, it was found that the leaked oil had spread across an area of approx. 5m × 5m × 1mm and that the oil supply valve was slightly open. The oil supply valve was closed immediately. At 7:05 AM on the same day, we reported the incident to Tomioka fire station. Tomioka fire station conducted an on-site confirmation, and determined the incident to fall in the category of hazardous material leakage. Later, the leaked oil on the floor was completely wiped out. At present, the oil is continuing to leak at a rate of 1 drop per 3 seconds and being received by a drain pan.

-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.

* Revised past progress

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