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.
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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>
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. 1×10
1Bq/cm
3) or filtered water into the reservoir was started (the all-β radioactivity density of residual water in the underground reservoir No.1: 6.6×10
4Bq/cm
3).
[Recent dilution operation] On July 30, approx. 60m
3 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. 1×10
1Bq/cm
3) into the reservoir was started.
[Recent dilution operation] On July 31, approx. 72m
3 of water was transferred to a temporary tank.
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. 1×10
1Bq/cm
3) into the reservoir was started.
[Recent dilution operation] On July 30, approx. 70m
3 of water was transferred to a temporary tank. On July 31, approx. 60m
3 of filtered water was injected.
<Sampling>
On July 31, 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 July 30). Further, analysis for tritium was conducted on water sampled on July 24 in the drain holes and leakage detection holes of the underground reservoirs No.1-No.4 and No.6. The analysis results showed no significant change compared to the previous results (from sampling performed on July 17).
- At 6:40 AM on July 30, cooling of the Unit 4 spent fuel pool was suspended due to inspection on instruments of the Unit 4 spent fuel pool alternative cooling system.
At 3:30 PM on July 31, cooling of the spent fuel pool was restarted after the completion of the instrument inspection. The pool water temperature increased to 39℃ from 31℃ while the cooling was being suspended. However, the temperature is still sufficiently low compared with the operational limit value of 65℃, and causes no problem in controlling the water temperature of the spent fuel pool.
- 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.
Radiation dose rate distribution measurement was conducted on the boring core of the groundwater observation hole No.5-1 (the whole boring core, which was sampled between the ground surface and 16 meter-depth level, was divided into 160 segments each corresponding to 10 cm along the depth). As a result, the highest dose rate was found in a core part sampled at depths of 1.5-2.0m from the ground surface. We consider that the peaks in core parts sampled at depths of 0.5-1m, at depths of 2.5-3.0m, and at depths of 3.5-4.0m from the ground surface were affected as those core parts were placed next to the core part sampled at depths of 1.5-2.0m that showed the highest dose rate. Therefore, we will conduct the measurement again with the core segments separated from each other. A part of the core that corresponds to depths of 2.7-5.9m from the ground surface had been solidified in a concrete-like state as a result of the foundation improvement, and there was found no trace of groundwater passing through this part. We will conduct the same measurement on other groundwater observation holes to find out underground radiation dose rate distributions.
The γ nuclide and all-β densities in water sampled on July 31 in the newly installed groundwater observation hole No.1-5 (west of the groundwater observation hole No.1-3) were measured.
<Groundwater observation hole No.1-5> (new)
- Sampling on July 31: Cesium-134 21Bq/L
Cesium-137 44Bq/L
All-β 1,200Bq/L
Analysis was conducted on 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 almost the same values, and the 13-meter water depth location showed higher values than the 1-meter and 7-meter water depth locations. With respect 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]
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]
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]
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]
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]
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]
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)
<Quality of water leaked into the Unit 2 water intake screen room in April 2011>
Cesium-134 1,800,000,000Bq/L (1,800,000Bq/cm3)
Cesium-137 1,800,000,000Bq/L (1,800,000Bq/cm3)
The water level in the Unit 2 water intake power cable trench was 3,180mm, showing an increase of approx. 30mm from the previous value (3,150mm). We will keep track on the trend while reflecting results that will be available in the subsequent measurement. The water level in the seawater pipe trench (A of Unit 2) measured at the same point in time was 3,045mm.
- At 10:33 AM on July 26, accumulated water transfer from the Unit 2 Turbine Building basement to the Unit 3 Turbine Building basement was started.
At 9:31 AM on August 1, the transfer was stopped.
-
At 11:40 AM on August 1, accumulated water transfer from the Unit 1 Turbine Building basement to Unit 1 Waste Treatment Building was started.
- At around 9:53 AM on July 30, an alarm went off indicating suspension of a booster pump and detection of leakage, and the second cesium adsorption apparatus (SARRY) was suspended. A TEPCO employee checked the site and did not find any problem such as leakage. Later, the alarm panel at the site was checked, which gave us information that the suspended booster pump was in the system B, and that an alarm indicating an abnormality of the cesium adsorption tower had been going off. Incidentally, water treatment and reactor water injection will be unaffected by the suspension of treatment operation of the second cesium adsorption apparatus (SARRY) as we have confirmed that the Central Radioactive Waste Treatment Facility (High Temperature Incinerator Building and Process Main Building used in combination) has sufficient room to receive water in transfer of accumulated water and that water to be injected into the reactors has been secured in a sufficient amount through condensate water storage tanks and the desalination system used in combination. On July 31, a detailed investigation was conducted, which revealed that this was an incident where the alarm went off due to a faulty instruction from a pressure reading transmitter placed at the absorption tower entrance and resulted in the suspension.
On August 1, we replaced the pressure reading transmitter found to have issued the faulty instruction. Then, on the same day, we started up the second cesium adsorption apparatus (SARRY) at 1:05 PM, and the regular flow rate was reached at 2:25 PM. No abnormality has been found in the operation status.
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