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
-At around 8:20 AM on July 18, an associated company worker, investigating the site using a camera ahead of debris removal work, encountered a steam-like gas wafting through the air near the central part of the fifth floor (equipment storage pool side) of Unit 3 Reactor Building. No significant change was found in the main parameters related to the plant (temperature, pressure and xenon density of PCV/RPV). Neither was any significant fluctuation found in the monitoring post readings or the continuous dust monitor amounts. At 9:20 AM on the same day, the subcritical state was found being maintained. With regards the measurement result of ambient dose on the upper part of the spent fuel pool protection at Unit 3 Reactor Building, no remarkable change was found compared to the measurement result so far obtained every day before work.
All of the values obtained from dust sampling conducted on the same day in the north side (where the sampling was performed twice) and the northeast side of a space over the reactor at Unit 3 Reactor Building fell within the fluctuation ranges observed during the past half year.
Given the dust sampling results and the status of the plant, we consider that the steam was generated due to rainwater having leaked through gaps near the well cover and having been heated at the head of the primary containment vessel. At 7:55 AM on July 19, no steam-like gas was found when we investigated through a camera the site where a steam-like gas was wafting.
On the same day, the temperatures near the site were measured and found to be in the range of 20.8-22.3°C (between 1:44 and 2:54 PM). The outside air temperatures were 21.4°C (as at 1:40 PM) and 20.1°C (as at 3:00 PM).
On July 20, the third and fourth rounds of dust sampling were conducted in the north side of the space over the reactor at Unit 3 Reactor Building, and dust sampling was also conducted in the northeast side of the space over the reactor (where the sampling is regularly conducted). As a result, we found that all of the thus obtained values were at levels equivalent to or lower than the levels in the previous measurement (on July 18) and fell within the fluctuation ranges observed during the past half year.
-
At 9:40 AM on July 21, accumulated water transfer from the Unit 1 Turbine Building basement to Unit 1 Waste Treatment Facility Building was started.
-
At 9:52 AM on July 21, accumulated water transfer from On-site Bunker Building to Process Main Building was started in Central Radioactive Waste Treatment Facility. At 2:56 PM on the same day, the transfer was stopped.
-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 20, 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 18, approx. 20ｍ
3 of desalination-system (RO) treated water was injected.
On July 21, 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>
Analysis was conducted on water sampled on July 20 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 19).
-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.
*
Revised past progress
The aforementioned attachments are only available in Japanese.
We apologize for any inconvenience this may cause.
