Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM on August 7)

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

-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>
· Since the decreases of all-β radioactivity densities in the leakage detection holes (at the northeast side of the underground reservoir No.1, the northeast side of the underground reservoir No.2, and the southwest side of the underground reservoir No.3) have been slow, operations to dilute the underground reservoirs No.1-No.3 by transferring filtered water or desalination-system (RO) treated water (the all-β radioactivity density: approx. 1×10¹Bq/cm³) into these reservoirs have been conducted as appropriate.
[Recent dilution operations]
Underground reservoir No.1 (since June 19): On August 3, approx. 60m³ of filtered water was injected.
Underground reservoir No.2 (since June 27): On August 1, approx. 60m³ of filtered water was injected.
Underground reservoir No.3 (since July 24): On August 5, approx. 60m³ of filtered water was injected.

· On August 6, 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 August 6, 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 30 in the observation holes on the sea side (1)-(4), and on August 5 in the other locations). Further, analysis for tritium was performed on water sampled on July 29 and 30 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 July 22 in the observation holes on the sea side (5)-(8), and on July 23 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.

The γ nuclide and all-β densities in water sampled on August 6 from the groundwater observation holes No.1-5 (west of the groundwater observation holes No.1-3) were measured. All of these γ nuclide and all-β densities were almost as high as the previous densities (in the sample taken on August 5). In addition, antimony was detected this time. With regards to the other measured densities, no significant change was found compared to the previous densities.
<Groundwater observation hole No.1-5>
- Sampling on August 6:
Cesium-134 260Bq/L
Cesium-137 540Bq/L
Antimony-125 6.7Bq/L
All-β 47,000Bq/L
- Sampling on August 5 (previously announced):
Cesium-134 310Bq/L
Cesium-137 650Bq/L
Antimony-125 ND (detection limit value: 6.4Bq/L)
All-β 56,000Bq/L
<Other locations on which we obtained measurement results on August 6>
· Tritium in the groundwater observation holes No.1, No.1-2, No.1-3, No.1-4, No.2, No.2-1, No.3, and No.3-1 (samples taken on August 1 and 2)
· γ nuclides and all-β in the groundwater observation holes No.1, No.1-2, No.1-3, No.1-4, No.2, and No.2-1 (samples taken on August 5)
· γ nuclides and all-β in seawater inside the port (other than seawater in the Unit 1-4 water intake north side and seawater between the water intakes of Units 1 and 2 (near the surface and near the bottom)) (samples taken on August 5)
· γ nuclides in the groundwater observation hole No.1-2 after filtering (a sample taken on August 5)

-With regards to the steam found coming from the vicinity of the central part of the Unit 3 Reactor Building fifth floor (equipment storage pool side) at around 8:00 AM on August 6, we found at around 9:00 AM on August 7 that the steam had disappeared. The plant status, the monitoring post readings, etc. as at 9:00 AM showed no abnormality. (As at 8:00 AM, the air temperature and humidity were 27.6℃ and 78.7%.)

-On August 6, we conducted an internal inspection on the absorption tower (6A) of the multi-nuclide removal equipment system A with the absorber having been pulled out of the tower. As a result, we found out: crevice corrosion at the flange surface; and discoloration near a welding line inside the absorption tower, which seems attributable to corrosion. We will continue investigation to identify the cause and the extent of influence of the corrosion.

-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. 3m × 2m × 1mm (amounting to approx. 6L)^* 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. Then, the oil was continuing to leak at a rate of 1 drop per 3 seconds and being received by a drain pan. On July 23, oil was withdrawn from the actuation valve oil injection tank, so that the amount of the oil was adjusted to the appropriate level. On July 24, we confirmed that the oil leakage had stopped (the leaked oil amounts to approx. 25L). As a result of an on-site investigation conducted later, we found out that the actuation valve oil injection tank level was the overflow level, and that the oil supply valve was "one turn open". We consider that these conditions caused oil in the tank to leak through an overflow line to the floor surface. Additionally, a drain receiver installed to receive oil that overflows from the overflow line had been installed in a position slightly different from the correct one, so that the oil did not go into a container from the drain receiver and leaked onto the floor surface. Note that, since the actuation valve oil injection tank level was normal in the morning on July 22, the tank supply valve seems to have been set "open" thereafter. As to why the supply valve was set "open", we assumed reasons listed below. However, these reasons were found inapplicable based on interviews with related workers. Accordingly, we took measures below to prevent a recurrence of an incident of this kind.
<Reasons we assumed>
· The valve was set "open" by mistake during confirmation of conditions of machines and equipment when workers related to the operation and maintenance conducted an on-site confirmation.
· Some on-site worker set the valve "open" by mistake.
<Measures>
· Chain locking of the supply valve in issue and other similar valves (in the closed state).
· Attachment of a spring fixation device such as one attached to a similar valve (A spring fixation device such as one attached to a similar valve had not been attached to the valve in issue).
· A measure to immobilize the drain receiver (installation of a guide).
· Thorough control of door locking at the site.

* We announced on July 23 that the oil had spread across an area of approx. 5m × 5m × 1mm. As a result of the on-site investigation, the area was found out to be approx. 3m × 2m × 1mm (with the leaked oil amounting to approx. 6L).

-On August 7, sampling was performed at the charcoal filter and the particulate filter of the Unit 2 PCV gas control system.

-On August 7, dust sampling was performed at the ventilation facility in Unit 2 Reactor Building.

* Revised past progress

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