Top > Releases ･ Announcements > Press Releases > Status of TEPCO's Nuclear Power Stations after theTohoku-Chihou-Taiheiyou-Oki Earthquake > 2013 > Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM on August 3)
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
- On August 3, sampling was performed at the charcoal filter and the particulate filter of the Unit 3 PCV gas control system.
- On August 3, dust sampling was performed in the upper part of Unit 3 Reactor Building.
- 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.
At the underground reservoir No.2, the observation holes No.2-14, No.2-15, and No.2-16 were additionally bored outside the observation holes No.2-10, No.2-11, and No.2-12, where all-β was detected, so that the contaminated area would be identified. We were able to identify the range of the contaminated area. Accordingly, on July 13, we started work of removing soil within the identified contaminated area and replacing the removed soil with filler. On August 2, the work was completed.
<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 August 3, 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 August 1, approx. 60m3 of filtered water was injected.
On July 24, since the decrease of all-β radioactivity density in the leakage detection hole (southwest) at the underground reservoirs No.3 has been slow, an operation to dilute the underground reservoir No.3 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 31, approx. 60m3 of filtered water was injected. On August 2, approx. 113m3 of water was transferred to a temporary tank.
On August 2 and 3, 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 2, 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). The analysis results showed no significant change compared to the results from sampling previously performed (on August 1).
- From 2:25 to 2:56 PM on August 2, cooling with the reactor shutdown cooling mode of the Unit 5 residual heat removal system was temporarily suspended as the reactor shutdown cooling mode had to be switched from the system A to the system B due to inspection on the residual heat removal seawater system pump (C). Since the restart of the cooling system using the system B, no abnormality has been found in its operation status. The reactor water temperature, although having increased from 31.0℃ to 31.1℃ during the suspension, has remained sufficiently low compared with the operational limit value of 100℃, and brings no problem in controlling the reactor water temperature.
- At 9:38 AM on August 2, accumulated water transfer from the Unit 1 Turbine Building basement to Unit 1 Waste Treatment Building was started. At 4:43 PM on the same day, the transfer was stopped.
- 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.
Tritium densities were measured in water sampled on July 31 from the Unit 2 seawater pipe trench vertical shaft C and the Unit 3 seawater pipe trench vertical shaft B where sampling has been newly started for the survey conducted for such purposes as identification of the contamination source of high-density contaminated water inside the sea-side trench. With regards to the analysis results on the Unit 2 seawater pipe trench vertical shaft C, the 1-meter and 7-meter water depth locations showed the same value, and the 13-meter water depth location showed higher value than the 1-meter and 7-meter water depth locations. With regards to the analysis results on the Unit 3 seawater pipe trench vertical shaft B, no water-depth related difference was found.
<Unit 2 seawater pipe trench vertical shaft C>
- Sampling on July 31:
[1-m water depth]
Tritium 2,400,000Bq/L (2,400Bq/cm3)
Chlorine 700ppm
Cesium-134 110,000,000Bq/L (110,000Bq/cm3)
Cesium-137 230,000,000Bq/L (230,000Bq/cm3)
All-β 330,000,000Bq/L (330,000Bq/cm3)
[7-m water depth]
Tritium 2,400,000Bq/L (2,400Bq/cm3)
Chlorine 700ppm
Cesium-134 110,000,000Bq/L (110,000Bq/cm3)
Cesium-137 240,000,000Bq/L (240,000Bq/cm3)
All-β 330,000,000Bq/L (330,000Bq/cm3)
[13-m water depth]
Tritium 4,600,000Bq/L (4,600 Bq/cm3)
Chlorine 7,500ppm
Cesium-134 300,000,000Bq/L (300,000Bq/cm3)
Cesium-137 650,000,000Bq/L (650,000Bq/cm3)
All-β 520,000,000Bq/L (520,000Bq/cm3)
<Unit 3 seawater pipe trench vertical shaft B>
- Sampling on July 31:
[1-m water depth]
Tritium 360,000Bq/L (360Bq/cm3)
Chlorine 16,000ppm
Cesium-134 13,000,000Bq/L (13,000Bq/cm3)
Cesium-137 26,000,000Bq/L (26,000Bq/cm3)
All-β 32,000,000Bq/L (32,000Bq/cm3)
[7-m water depth]
Tritium 340,000Bq/L (340Bq/cm3)
Chlorine 17,000ppm
Cesium-134 10,000,000Bq/L (10,000Bq/cm3)
Cesium-137 22,000,000Bq/L (22,000Bq/cm3)
All-β 34,000,000Bq/L (34,000Bq/cm3)
[13-m water depth]
Tritium 350,000Bq/L (350Bq/cm3)
Chlorine 17,000ppm
Cesium-134 12,000,000Bq/L (12,000Bq/cm3)
Cesium-137 24,000,000Bq/L (24,000Bq/cm3)
All-β 34,000,000Bq/L (34,000Bq/cm3)
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