Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM on May 30)

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). 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 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 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 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.

<Transfer of water stored in the underground reservoirs>
From April 6 to April 9, contaminated water was transferred from the underground reservoir No.2 to No.1.
From April 6 to April 11, contaminated water was transferred from the underground reservoir No.2 to No.6.
From April 11 to April 14, contaminated water was transferred from the underground reservoir No.3 to No.6.
From April 16 to April 22, contaminated water was transferred from the underground reservoir No.2 to H2 area tank. The amount of water transferred during the period is approx. 1,070m³.
At 12:24 PM on April 23, contaminated water transfer from the underground reservoir No.1 to H2 area tank was started. The transfer will be temporarily suspended after the transfer performed on April 26.
At 10:58 AM on April 25, contaminated water transfer from the underground reservoir No.1 to the filtrate water tank No.1 was started. At 5:12 AM on April 29, the transfer was suspended. The amount of water transferred during the period from April 25 to 29 is approx. 4,600m³.
At 9:23 AM on April 29, the contaminated water transfer from the underground reservoir No.1 to H2 area tank was restarted. The water transfer was stopped at 12:19 PM on May 6. The total amount of transferred water during the period from April 23 to 26 and from April 29 to May 6 is approx. 2,250m³.
At 11:03 AM on May 18, contaminated water transfer from the underground reservoir No.3 to G6 area tank was started. At 9:00 AM on May 21, the transfer was temporarily suspended.
At 10:19 AM on May 21, contaminated water transfer from the underground reservoir No.6 to G6 area tank was started. At 4:02 PM on May 23, the transfer was temporarily suspended.
At 10:25 AM on May 25, contaminated water transfer from the underground reservoir No.3 to G6 area tank was started. At 9:05 AM on May 28, the transfer was temporarily suspended.
At 9:54 AM on May 28, contaminated water transfer from the underground reservoir No.6 to G6 area tank was started.

<Measures to prevent expansion of contaminated water leakage>
Since April 10, work to return the leaked water accumulated in the leakage detection hole of the underground reservoir No.1 to the reservoir has been performed.
Since April 11, work to return the leaked water accumulated in the leakage detection hole of the underground reservoir No.2 to the reservoir has been performed.
Since April 13, work to return the leaked water accumulated in the leakage detection hole of the underground reservoir No.3 to the reservoir has been performed.
The measures to prevent expansion of contaminated water leakage are to be implemented for the underground reservoirs No.1-3 as necessary.
On May 29, the leaked water accumulated in the leakage detection holes of the underground reservoirs No.1-3 and in the drain hole of the underground reservoir No.2 was transferred to the notch tank.

<Sampling>
On April 6, sampling was performed in the drain holes of the underground reservoirs No.1, 3 and 4 as well as in the drain holes (northeast, southwest) and the leakage detection holes (northeast, southwest) of the underground reservoir No.2.
On April 7, sampling in the drain holes (northeast, southwest) and the leakage detection holes (northeast, southwest) of the underground reservoirs No.1-7 was started.
On April 10, sampling in the groundwater bypass pump wells No.1-4 was started.
On April 11, sampling in the groundwater bypass investigation holes A-C was started.
On April 14, sampling was performed in the leakage detection hole (southwest) of the underground reservoir No.7 for background measurement.
On April 15, sampling in the observation hole (A8) of the underground reservoir was started.
On April 17, sampling in the observation holes (A11, A18) of the underground reservoir was started.
On April 21, sampling in the observation holes (A9, A10, A12, A14, B1 and B2) of the underground reservoir was started.
On April 22, sampling in the observation holes of the underground reservoirs (A3, A4, A15, A19 and B3) and in the observation holes on the sea side ((1) and (2)) was started.
On April 23, sampling in the observation holes of the underground reservoirs (A2, A5, A13 and A16) and in the observation hole on the sea side ((3)) was started.
On April 24, sampling in the observation holes of the underground reservoirs (A1, A6, A7 and A17) and the observation hole on the sea side ((4)) was started.
On April 29, sampling in the observation holes on the sea side ((5), (6)) was started.
On April 30, sampling in the observation hole on the sea side ((8)) was started.
On May 1, sampling in the observation hole on the sea side ((7)) was started.
On May 8, sampling in the observation holes of the underground reservoir No.2 (2-3, 2-4) was started.
On May 10, sampling in the observation holes of the underground reservoir No.2 (2-1, 2-2) was started.
On May 12, sampling in the observation holes of the underground reservoir No.2 (2-5, 2-6, geological survey hole (1)) was started.
On May 13, sampling in the observation hole of the underground reservoir No.2 (2-7) was started.
On May 21, sampling in the observation holes of the underground reservoir No.2 (2-9, 2-12) was started.
On May 22, sampling in the observation holes of the underground reservoir No.2 (2-10, 2-11) was started.
On May 23, sampling in the observation holes of the underground reservoir No.2 (2-8, 2-13) was started.
On May 29, sampling was performed in the drain holes of the underground reservoirs No.1-7 (14 locations), the leakage detection holes of the underground reservoirs No.1-4 and 6 (sample could not be collected at 2 out of 10 locations), and the observation holes of the underground reservoirs (22 locations). As a result of the analysis, no significant change was found compared to the analysis results from the sampling performed previously (on May 28). Further, analysis for tritium was performed on water sampled on May 22 in the drain holes and leakage detection holes of the underground reservoirs No.1-4 and 6 (the analysis is performed once a week). As a result, no significant change was found compared to the previous analysis results.

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

- In Unit 1, piping repair in the residual heat removal equipment cooling seawater system (B) in response to separation of lining attached on the inner surface of piping in this system was completed. An internal voluntary inspection confirmed that this system and the related systems are sound. Accordingly, restoration of the proper facilities and equipment for cold shutdown of Unit 1 has been completed today.
Upon this restoration, restoration of the facilities for cold shutdown in all of the units (Units 1-4) at this power station according to the restoration plan has been completed.

- At around 5:18 PM on December 7, a M7.3 earthquake occurred at the offshore of Sanriku. Upon plant checkup, no problem originating from the earthquake was found. Since the pressure in Unit 1 Reactor Building had turned positive relative to the outdoor air pressure (though the pressure had been kept negative), the standby gas treatment system^* was started upon judgment of an operator. The pressure in the Reactor Building increased to 0.05kPa right after the system was started and later the pressure turned back to negative and became stable. In order to investigate the cause of the pressure turning to positive, the standby gas treatment system was suspended and the Reactor Building ventilation and air conditioning system was started on December 8. The pressure in the Reactor Building has been stably maintained negative relative to the outdoor air pressure after this switching. The following is the result of a later-conducted investigation of the cause. When the supply air flow rate in the Reactor Building 6th floor had increased to approx. 51000m³/h from approx. 43000m³/h at the time of installation of a damper (an isolation plate for an air conditioning duct), the earthquake occurred, and caused the damper to close; the exhaust air flow rate of the Reactor Building ventilation and air conditioning system was thereby reduced; and the supply air flow rate exceeded the exhaust air flow rate in the Reactor Building 6th floor, which possibly caused the pressure in the Reactor Building to turn positive. From this time on, we will operate the ventilation and air conditioning system with the supply air flow rate in the Reactor Building 6th floor maintained at approx. 32000m³/h, which was determined considering the necessary number of air exchanges and the amount of air needed for the cold shutdown state. Also, in order to control the pressure in the Reactor Building to keep it negative, we will measure the exhaust air flow rate in the Reactor Building 6th floor when conducting work of opening the reactor or work involving irradiated fuel.
* Standby gas treatment system: System that purifies the air in the Reactor Building utilizing high performance filter and discharge it to the outside through the exhaust stack. The system is comprised of systems (A) and (B).

* Revised past progress

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