The following is the known status as of Thursday morning of each of the six reactors at the Fukushima Daiichi nuclear power plant and the four reactors at the Fukushima Daini plant, both in Fukushima Prefecture, which were crippled by the magnitude 9.0 earthquake and ensuing tsunami on March 11.
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 8:00 AM on September 13, we found steam-like gas coming again from the vicinity of the central part of the fifth floor (equipment storage pool side) of Unit 3 Reactor Building by a camera. No abnormality has been found in the plant status, the monitoring post readings, etc., as of 8:30 AM. (As of 8:00 AM, the air temperature was 22.7℃, and the humidity 94.5%.) At around 3:00 PM on the same day, steam was not found. Further, no abnormality has been found in the plant status, the monitoring post readings, etc., as of 3:00 PM. (As of 3:00 PM, the air temperature was 25.3℃, and the humidity 82.3%.)
-At 10:00 AM on September 13, accumulated water transfer from the Unit 6 Turbine Building basement to a temporary tank was started. At 1:00 PM on the same day, the transfer was stopped.
-At around 3:20 PM on September 12, a TEPCO employee found water leaking from the accumulated water treatment system (vehicle-mount type) for Units 5 and 6. Accordingly, the accumulated water treatment system was immediately stopped, and it was confirmed that the water leaking was stopped. We performed a detailed investigation as to the range over which the leaked water has spread, and found a trace of water leakage, sized approx. 2m×6m, in the trailer on which the accumulated water treatment system has been mounted. Water having leaked from inside to outside the trailer was found over a range of approx. 3m×3m×1cm. The amount of the leaked water was estimated to be about 0.065m3 based on the leakage time, the flow rate, etc. Given that there is no watercourse such as a drainage ditch around the system, we consider that water having thus leaked has not flowed into the sea. Further, we sampled and analyzed the leaked water, and the water showed almost the same values as water used for sprinkling at the site*.
<The results of sampled leaked water>
Cesium-134: Below the detection limit value (the detection limit value: 1.6×10-3Bq/cm3)
All-β: Below the detection limit value (the detection limit value: 1.4×10-2Bq/cm3)
*Radioactivity density of water which could be used as sprinkling water: The sum of cesium-134 and cesium-137 should meet 1×10-2Bq/cm3.
-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 12 and 13, 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.
On September 12, 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 compared to the analysis results on the previous samples (taken on September 11).
-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 (γ and β 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 12, 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 (expect for the leaks that resulted in accumulated water inside the dike).
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 are planning to transfer water inside the tanks to an RO waste liquid supply tank to reduce the risk of leakage. The transfer is scheduled to be conducted between August 29 and September 17.
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. 30m exit (C-2) (on September 12), and conducted nuclide analysis on the water. Remarkable results of the analysis are as follows.
· The all-β density at the point B-3 was high (2,400Bq/L) compared to the past analysis results for all-β (380 to 920Bq/L). This is considered because the water at the point B-3 is residual water that has been held back and left, which is currently cleaned in the cleaning of the drainage channel B.
· The all-β density at the point C-2, where the previous value (in the sample taken on September 11) was high, fell below the detection limit value (the detection limit value: 11Bq/L). Therefore, this location seems to have been temporarily affected by work conducted upstream of the point C-2.
The other analysis results showed no remarkable change from the previous values.
Incidentally, at 2 points (B-1 and B-2) in the drainage channel B, there was no water and hence the sampling was impossible.
We conducted analysis for γ nuclides, all-β and tritium on water in observation holes (E-1: on the north of the dike that surrounds tanks including Tank No.5 in Group I in the H4 area from which water has leaked, E-2: on the south of the dike that surrounds tanks including Tank No.5 in Group I in the H4 area from which water has leaked) newly installed near the H4 area tanks.
With regards the groundwater observation hole (E-1) around the H4 area, tritium in the sample taken on September 11 was detected at 97,000Bq/L, which is high compared to 64,000Bq/L in the sample taken on September 10. As it is highly possible that the leakage from the H4 area tank had an impact on the density, we will continue analysis on groundwater around the area to find out the range reached by the leaked water. With regards the groundwater observation hole (E-2) around the H4 area, the analysis resulted in a value about the same as that in the sample taken on September 10.
We are planning to disassemble and inspect Tank No.5 in Group I in the H4 area, which was found leaking water. On September 13, in preparation for the disassembly and inspection, we started to disassemble Tank No.10 in Group I in the H4 area for the purpose of securing a work area.
-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 to 13, 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.
We conducted analysis for tritium on water in the newly installed sub-drain observation well (1T-4) at the sea-facing side of Unit 1 Turbine Building, and the newly installed sub-drain observation wells (2T-1 and 2T-2) at the sea-facing side of Unit 2 Turbine Building (sampled on September 11).
<Sub-drain observation well 1T-4 (at the sea-facing side of Unit 1 Turbine Building)>
· Sampled on September 11
<Sub-drain observation well 2T-1 (at the sea-facing side of Unit 2 Turbine Building)>
· Sampled on September 11
<Sub-drain observation well 2T-2 (at the sea-facing side of Unit 2 Turbine Building)>
· Sampled on September 11
-On August 12 and 19, an alarm indicating a high radioactivity density (a high-high radioactivity alarm) went off at a continuous dust monitor installed in front of the Main Anti-earthquake Building. We determined that this incident was caused by debris removal work in the upper part of Unit 3 Reactor Building, based on the facts that: the debris removal work in the upper part of Unit 3 Reactor Building was ongoing on the windward side of the continuous dust monitor on both of these days, and an association was found between what was being conducted and the time points when the alarm went off; and we have seen no change in the continuous dust monitor readings since August 20 when we suspended the debris removal work in the upper part of Unit 3 Reactor Building. Meanwhile, we implemented the following recurrence prevention measures.
· Suppression of increase in dust during debris removal work by reforming the procedure of spraying anti-scattering agents
· Intensification of monitoring of in-air densities of radioactive materials on dust in the work space (on the operating floor) and the surrounding areas (the slope near Unit 3 Reactor Building)
· Installation of a covering tunnel to function as a measure to protect the bus stop shelter in front of the Main Anti-earthquake Building from contamination
At 12:00 AM on September 13, the instruction to wear masks in the areas within the power station where full-face (half-face) masks are not required was withdrawn as these recurrence prevention measures were put into operation.