Status of TEPCO's Nuclear Power Stations after the Tohoku-Chihou-Taiheiyou-Oki Earthquake (Daily Report as of 3:00 PM on September 26)

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

-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>
· Since the decreases of all-β radioactivity densities in the leakage detection holes (at the northeast side of the underground reservoir No.1, the northeast side of the underground reservoir No.2, and the southwest side of the underground reservoir No.3) have been slow, operations to dilute the underground reservoirs No.1-No.3 by transferring filtered water or desalination-system (RO) treated water (the all-β radioactivity density: approx. 1×10¹Bq/cm³) into these reservoirs have been conducted as appropriate.

<Recent dilution operations>
· Underground reservoir No.1 (since June 19): On August 3, approx. 60m³ of filtered water was injected.
· Underground reservoir No.2 (since June 27): On August 1, approx. 60m³ of filtered water was injected.
· Underground reservoir No.3 (since July 24): On August 12, approx. 107m³ of water in the drain hole (northeast) of this underground reservoir was injected.

On September 25, 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 September 25, 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). No significant change was found in the analysis results in comparison to the analysis results for the samples collected previously (on September 24).
Also, no significant change was found from the analysis results of the previous time (collected on September 11) in the results of the analysis conducted for tritium in the samples collected on September 18 at the drain holes of the underground reservoirs No.1-No.7 (14 locations) and the leakage detection holes of the underground reservoirs No.1-No.4 and No.6 (samples could not be collected at 2 of 10 locations).
The all-β values of the leakage detection hole of underground reservoir No. 3 changed to increase again following the recommencement of construction work to counter uplift in the underground reservoir, and the countermeasure construction work for preventing uplift in the underground reservoir in question is to continue until the end of this month, so we believe that a change in density in the detection hole in question will be found after this.

-On August 19, puddles were found inside a dike around the H4 area tanks in the power station and outside of a drain valve of the dike.
We found water spread at the bottom level of tanks near Tank No.5 in the Group I in the H4 area. Therefore, we checked the water level of this tank, and found out that the water level has fallen by approx. 3m than the normal level (the amount of water: approx. 300m³). We started collecting the water remaining inside the dike and already collected some of the water. However, since it seemed that the water has flowed out of the dike through the drain valve, we are collecting soil in the surrounding area and continuing to conduct an investigation to find out the range reached by the water. Later, we found streaky traces of flows on the wall surface of a drainage channel located east of the H4 area tanks. The maximum surface dose equivalent rate measured at this location was 6.0mSv/h (β+γ rays (70μm dose equivalent rate)). As this information indicates the possibility that contaminated earth and sand, etc. may have flowed into the drainage channel, we are planning to conduct a detailed investigation and evaluation concerning these traces.

On August 22, transfer of water stored in Tank No.5 in Group I in the H4 area and water collected in a temporary tank (water accumulated inside the dike) into Tank No.10 in Group B in the H4 area was completed.

On August 22, we conducted full inspections (appearance inspections and dose measurement) on the flanged tanks in the other areas, which are of the same type as the tank from which water has leaked. Neither leak nor puddle was found by the appearance inspections on the tanks and the drain valves. However, 2 locations locally showing high dose rates were found around the H3 area tanks. The surfaces of these locations were dry, and we confirmed that there has been no water having flowed into the inside of the dike or the outside of the dike. We also confirmed that the water levels of these tanks remain unchanged after they received water. Additionally, we conducted soundness inspections (visual appearance inspections and water level confirmation) on the flanged tanks that are in use for storage of accumulated water from Units 5 and 6. The inspections were completed on August 26 and showed no abnormality.

During our inspection of Tank No.5 in Group I in the H4 area from which water has leaked, we found out the following:
· 3 tanks including this tank (Tank No.5 in Group I, Tank No.10 in Group I, and Tank No.3 in Group II in the H4 area) were initially installed in the H1 area.
· Ground subsidence occurred in the H1 area at the foundations on which these tanks had been placed, and these tanks were planned to be installed in the H2 area, but actually, have been placed in the H4 area despite our plan.
Although it is still unclear whether there is a causal relationship between the water leaking of Tank No.5 and the tank's having experienced ground subsidence occurred in the H1 area at the foundation on which it had been placed, we conducted water transfer from inside Tank No.3 in Group II in the H4 area to Tank No.10 in Group B in the H4 area to reduce the risk of leakage.
<The latest transfer operations>
· At 3:57 PM on August 25, transfer from Tank No. 10 in Group I in the H4 area to Tank No. 10 in Group B in the H4 area was started. At 2:07 AM on August 27, the transfer was completed.
· At 10:30 AM on August 29, transfer from Tank No. 3 in Group II in the H4 area to Tank No. 10 in Group B in the H4 area was started. At 2:07. At 11:03 AM on September 2 water transfer was suspended due to the implementation of rainfall countermeasures.

During a patrol on August 31, we found 4 locations showing high dose equivalent rates (γ and β rays (70μm dose equivalent rate)). We consider that there has been no leakage to the outside of the dike because the water levels of all of the relevant tanks have not decreased and also because the drainage valves have been closed.
One of the 4 locations, the connecting pipe section between Tank No.5 and Tank No.6 in Group IV in the H5 area has the heat insulation material placed in the upper part of the pipe, and one drop of water fell to the floor surface when this heat insulation material was pressed. The dose equivalent rate at a location on the floor surface to which the water fell was measured and confirmed to be approx. 230mSv/h. Although water then stopped dropping from the connecting pipe, a discolored part (in a dry condition) of approx. 20cm×20cm was found on the floor surface under the pipe section. Then, we checked the status of water dropping from the connecting pipe between Tank No.5 and Tank No.6 in Group IV in the H5 area with the heat insulation material having been pulled out. Then, we found out that a flange part connecting an isolation valve on the Tank No.5 side (there are 2 isolation valves connecting these tanks and connecting pipe) and the connecting pipe was dripping one drop per approx. 90 seconds. In response, on the same day, we wrapped the adsorption mat around this flange part and covered it with plastic-sheet protection, while placing a drain receiving pan under the flange part on the floor. Both of the 2 isolation valves on the respective Tanks No.5 and No.6 sides of this connecting pipe were found to have been closed. On September 1, we tightened up 12 flange bolts at this flange part, and we confirmed that no water leakage was occurring. For the confirmation purpose, the water levels of Tank No.5 and Tank No.6, in Group IV in the H5 area, were measured and found unchanged.
<Results of the latest patrol>
During a patrol on September 25, no location showed a high dose equivalent rate (β and γ rays (70μm dose equivalent rate)). Locations near the dike floor continued to show low dose equivalent rates since rainwater accumulated inside the dike (approx. 3 to 4 cm deep) worked as a shield. Additionally, we conducted a visual inspection, and all of the tanks were found without any abnormality such as leakage (except for within accumulated water inside the dike where leaks could not be confirmed). No abnormalities were confirmed in the water level by means of thermography (results of analysis of images taken on September 24).

As a result of the full inspections (appearance inspections and dose measurement) conducted on August 22 on the tanks in the areas other than the H4 area, we found tanks (Tank No.4 in Group B and Tank No.10 in Group A, both in the H3 area) each having a part locally showing a high dose rate. Although no water dropping was found on the outside of these tanks, we transferred water inside the tanks to an RO waste liquid supply tank since August 29 and completed by September 18. Also, the transfer of residual water in Tank No. 10 in Group A in the H3 area to Tank No. 5 in Group B in the H3 area has been completed.
<Sampling>
Following the leakage from a tank this time, we sampled water at the point near the south water outlet (T-2), at the junction of the drainage channels B and C near the H4 area (C-1), at the point immediately short of the junction with the drainage channel C (B-3), at the point near Fureai Intersection in the drainage channel B (B-0-1), at the point near the main gate in the drainage channel C (C-0), and at the drainage channel C OP. 35m exit (C-2) (on September 25), and conducted nuclide analysis on the water.
Although the analysis results were within the range of variation of past data, the all-β value, which was below the detection limit value until the previous day at C-2 rose to 160 Bq/L, and will continue to be monitored. No significant change was found in other analysis results from the previous day (samples collected on September 24).
On September 24, samples were collected of water in the groundwater bypass pump wells Nos. 5-12 (8 locations). No significant change was found in the analysis results in comparison to previous measured values. The situation will continue to be observed in the future as well.

We conducted analysis for all-β and tritium on water in observation holes installed near the H4 area tanks.

The analysis results for tritium in samples collected on September 24 from an observation hole (E-5) around the H4 area, which was newly analyzed this time, was found to be below the detection limit value. No significant change was found in the analysis results for tritium in samples collected on September 24 from observation holes (E-1, E-2, E-3, E-4) around the H4 area in comparison with the analysis results for samples collected on September 23.

· 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 and have been pumping up groundwater at the well point and the water collection point (south) on the east of Unit 1 and Unit 2 Turbine Buildings.

<The latest groundwater transfer operation>
At 3:50 PM on August 31, the water transfer to the Unit 2 vertical shaft C from the well points and the water collection pit (south) was suspended, and the water transfer to the Unit 2 Turbine Building was started at 3:55 PM on August 31.
So that water in the Unit 2 vertical shaft B (water collected due to the closure of the trench) could be transferred to Unit 2 Turbine Building during the daytime from September 3, groundwater transfer from the well points and the water collection pit (south) was conducted while the transfer destination was sequentially changed. The work of closing the trench was almost completed, and transfer of groundwater in the well points and the water collection pit (south) to Unit 2 Turbine Building has been underway.

-We conducted a purification test of wells (sub-drain pits) located next to the Units 1-4 buildings at Fukushima Daiichi NPS, and detected radioactive materials in water accumulated in the pits. One possible cause of the entrance of radioactive materials there is fallout. In order to find out the influence of fallout, we have been installing new observation wells around the Units 1-4 buildings.
<Sampling>
The analysis results for gamma and all-β in the water of samples collected on September 25 at observation well 3R-1 on the mountain side of the Unit 3 building, which was newly analyzed this time, was found to be below the detection limit value.

*At 2:20PM on September 25, operation of the accumulated water treatment system at Units 5 & 6 was restarted. There were no abnormalities in the operational state after restart.

*From the results of the investigation into the cause of a penetration defect due to crevice corrosion of the Advanced Liquid Processing System A system batch processing tank ("batch processing tank"), we have inferred that leakage from the lower part of the tank, which occurred from the batch processing tank 2A, was a superimposition of the compound factors of formation of a crevice environment due to iron deposits, which were generated, accumulating and attaching to the inside of the tank and acceleration of a corrosive environment due to chemical feeding (principally, hypochlorous acid) and other such factors, which caused more corrosion than anticipated and the defect lead to penetration and leakage. We have inferred that the corrosion found at adsorption tower 6 was generated and accelerated by the silver impregnated charcoal loaded into adsorption tower 6, which is not an alkaline environment. We have estimated that the adsorption tower inspection door flange, which was low flow rate making it prone to local corrosion in a stagnate state, was also a factor accelerating corrosion. As a recurrence prevention measure, we will create a rubber lining (chloroprene rubber) inside the tank after repairing the patch processing tank defect. We will construct a gasket-type sacrificial anode and other such components on the flange, where crevice corrosion may occur.

*As for the September 25 inspection of drains inside the outdoor trench of the standby gas treatment system (SGTS) for Units 5 & 6 and the SGTS piping (exhaust air line), an external visual inspection of the piping did not find any cracking deformation as well as other damage or significant corrosion.

*At about 8:00AM on September 26, a camera found steam being generated from the vicinity of the central area of the 5th floor of the Unit 3 reactor building (dryer separator storage pool side). No abnormalities were found in the plant status, monitoring post indicated values or other such parameters confirmed by 8:08AM on the same day (meteorological data as of 8:00AM showed a temperature of 18.8℃ and humidity of 93.3%).

*At about 10:42AM on September 26, a contractor worker discovered that the silt fence installed near the water intake for Units 5 & 6 was severed. Presently, wave height inside the port is high due to the effects of a typhoon, so repairs are planned as soon as conditions are able to ensure safety for the work to be performed.

* Revised past progress

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