Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM, April 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 nuclear power stations (Fukushima Daiichi and Fukushima Daini).

* 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). At 5:43 AM on April 6, we started transferring the water stored in the underground reservoir No.2 to the underground reservoir No.1 utilizing a permanent pump. Considering that 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 γray radiation dose leaked is estimated to be approx. 1.8×10⁸Bq and the β radiation dose leaked is estimated to be approx. 7.1×10¹1Bq. Details are currently being investigated.
As three temporary pumps were added and no problem was found with the temporary water transfer line, we started transferring the water from the underground reservoir No.2 to No.1 at 9:38 AM on the same day. In order to add another temporary pump, the pumps other than the permanent pump (3 temporary pumps) were temporarily suspended at 12:27 PM on the same day. Since no problem was found with the temporary pipeline of the newly added temporary pump, the water transfer from the underground reservoir No.2 to No.1 was started at 12:52 PM. The three temporary pumps suspended were restarted at 12:57 PM for water transfer from the underground reservoir No.2 to No.1.
In order to use the permanent facility for water transfer to the underground reservoir No.6, the water transfer to the underground reservoir No.1 was suspended at 3:33 PM on the same day. At 4:10 PM, water transfer from the underground reservoir No.2 to No.6 was started. Water transfer from the underground reservoir No.2 to No.1 utilizing temporary pumps is continued. On April 6, sampling was performed in the underground reservoirs (No.1 drain hole, No.2 leakage detection hole (northeast/southwest) and drain hole (northeast/southwest), No.3 drain hole and No.4 drain hole) as well as in the leakage detection hole (northeast/southwest) of the underground reservoir No.3.
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 and that the incident may be 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). On the same day, sampling was performed in the drain hole (northeast) and leakage detection hole (southwest: by vacuuming method*) of the underground reservoir No.3.
On April 7, sampling was performed in the drain holes (at 14 locations) and in the leakage detection holes (sampling could not be performed at 3 out of 10 locations) of the underground reservoirs No.1-No.7. At 6:25 AM on April 8, water transfer from the underground reservoir No.2 to No.1 utilizing temporary pumps was suspended since the water level of the underground reservoir No.1 had increased.
On April 8, sampling was performed in the drain holes (at 14 locations) and in the leakage detection holes (sampling could not be performed at 2 out of 10 locations) of the underground reservoirs No.1-No.7. At 10:00 AM on April 9, water transfer from the underground reservoir No.2 to No.1 utilizing 4 temporary pumps was restarted. 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 βnuclides 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 at 4:34 PM on the same day 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 and that the incident may be 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) 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.
The analysis results of samples collected in the drain hole and the leakage detection hole (southwest) of the underground reservoir No.1 in the morning of April 9 are as follows.
[Drain hole (northeast) of the underground reservoir No.1] All β radioactivity density: Below the detection limit
[Drain hole (southwest) of the underground reservoir No.1] All β radioactivity density: Below the detection limit
[Leakage detection hole (southwest) of the underground reservoir No.1] All β radioactivity density: 5.3×10^-2Bq/cm³
The analysis results of samples collected in the drain hole and the leakage detection hole (southwest) of the underground reservoir No.1 in the afternoon of April 9 are as follows.
[Leakage detection hole (northeast) of the underground reservoir No.1] Cs134, Cs137, I131: Below the detection limit, Sb125: 2.1×10¹Bq/cm³, Ru106: 1.5×10⁰Bq/cm³, All β: 1.5×10⁴Bq/cm³
[Leakage detection hole (southwest) of the underground reservoir No.1] Cs134, Cs137, I131: Below the detection limit, All β: 6.8×10^-2Bq/cm³
[Drain hole (northeast) of the underground reservoir No.1] Chloride concentration: 7ppm, Cs134, Cs137, I131: Below the detection limit, All β: 1.1×10^-1Bq/cm³
[Drain hole (southwest) of the underground reservoir No.1] Chloride concentration: 14ppm, Cs134, Cs137, I131: Below the detection limit, All β: 6.1×10^-2Bq/cm³
As a result of sampling performed in the drain holes of the underground reservoirs No.2-7 (at 12 locations) and the leakage detection holes of the underground reservoirs No.2-4 and 6 (sample could not be collected at 2 out of 8 locations) on April 9, no significant change was found compared to the results obtained on April 8.
In order to prevent the water leaked into the leakage detection holes of the underground reservoirs No.1 and No.2 from leaking into the ground in the surrounding area, temporary pumps have been installed on April 10. The leaked water in the leakage detection holes will be pumped up and returned to the underground reservoirs. The work will be performed until the transfer of the contaminated water stored in the underground reservoirs No.1 and No.2 to the tank installed above ground is complete.
Also, since contaminated water of a comparatively high radioactivity density was found in the leakage detection hole (northeast) of the underground reservoir No.2, the soil covering the leakage detection hole penetration, the impermeable sheet and the gravels will be removed for a visual inspection of the leakage detection hole penetration (northeast) once the preparation is complete.
In addition, boring investigation (the ground around the underground reservoirs and in the sea side will be drilled to collect water contained in the soil for radioactivity density analysis) will be performed as soon as preparation is complete for the purpose of confirming the contamination condition near the underground reservoirs and contamination expansion into the area in the sea side.
*Vacuuming method: A method to collect samples by utilizing a suction machine and a hose.

- At around 7:36 PM on February 16, a cooperative company worker found water overflowing from the water intake tank between the temporary tank storing accumulated water installed outside of Units 5-6 and the desalination system (reverse osmosis membrane). The leaked stopped after stopping the water intake pump on the upstream side of the water intake tank. The amount of leaked water is evaluated to be approx. 19.8m³ and the leaked water has been absorbed into the ground. We have judged that the leaked water has not flowed to the outside considering that there is no side ditch, etc. in the surrounding area. The cause of the leakage is currently under investigation. The radioactivity density analysis results of the leaked water are as follows.
Cesium 134: 6.8×10^-2Bq/cm³
Cesium 137: 1.3×10^-1Bq/cm³
All γ: 2.0×10^-1Bq/cm³
As a result of investigation, the cause has been assumed to be the abnormality of the part (substrate) which controls the intake chamber water level which caused the continuous operation of the water intake pump and the overflow of the intake chamber as a result. The following recurrence prevention measures have been implemented.
- Replacement of the substrate
- Web camera installation to allow for swift abnormality detection
- Installation of sandbags around the intake chamber and the filtrate water tank to prepare for unexpected leakage
At 2:30 PM on April 10, the desalination system (reverse osmosis membrane) on Units 5-6 side was restarted since the preparation had completed.

- At around 10:10 AM on April 8, a cooperative company employee found that the silt fence installed near Units 5-6 water intake canal and the silt fence installed near the shallow draft quay to prevent fish from moving out of the port had been cut off. Since the wave height is currently high in the area due to strong wind, the repair will be performed after the weather condition gets better. No significant change has been found with the monitoring post readings. On April 10, the repair of the silt fence installed near the shallow draft quay to prevent fish from moving out of the port has been completed. The repair work for the silt fence installed near Units 5-6 water intake canal is planned to start this weekend.

[Fukushima Daini Nuclear Power Station]
·Unit 1 to 4: Shutdown due to the earthquake.

* Revised past progress

The aforementioned attachments are only available in Japanese.
We apologize for any inconvenience this may cause.