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 major facilities.
*Updates are underlined.
[Nuclear Power Station]
Fukushima Daiichi Nuclear Power Station: Unit 1 to 3: shut down due to
the earthquake:
(Units 4 to 6: outage due to regular inspections before the earthquake)
-At 8:46 am on February 17, since the treatment capacity of the 2nd
Cesium adsorption apparatus was declining gradually, we stopped it for
the reverse cleaning of the filters. At 10:59 am on the same day, we
restarted it, and at 11:05 am it reached to the rated flow (approx.
36.4 m3/h).
-At 11:33 on February 17, we reduced the water injection rate to Unit 3
by the core spray system from approx. 6.0m3/h to approx. 5.0m3/h in
order to transfer the accumulated water increased due to the increase of
the water injection rate to Unit 2 as well as to reduce the burden of
the water treatment, seeing that we had some margins in the volume of
water injection at that time against the rate equivalent to the delay
heat. We also adjusted the water injection rate from the feed water
system, which was fluctuating, from approx. 2.9 m3/h to approx. 3.0 m3/h.
-Regarding the Unit 2 the bottom of whose RPV showed the increasing trend
of the temperature rise, since the trend was still continuing, we
started the operation to increase the water injection rate*1 at 2:10
February 12. At 2:20 pm, we judged that it did not satisfy the condition
"the temperature is below 80 °C at the bottom of PCV", which is one of
operational limits stipulated in "the Reactor Facility safety
Regulation*2. We conducted measures to satisfy those operational limits,
and increased the volume of water injection. The trend of the
temperature rise was continued further, we investigated the thermometer
in the lower part of the RPV of Unit 2 on February 13. Through the
investigation, we considered the possibility that the wires of device
are broken, since the higher DC resistance value than normal was
measured. After the final evaluation, we concluded that the device was
broken. Therefore, at 2:00 pm on February 17, we judged that the
temperature at the bottom of PCV was not actually increasing, and we
corrected the judge of the deviation from the conditions of operations
stipulated in the management of facilities retrospectively back from
February 12. We also excluded this device from the items to be monitored
for the temperature at the bottom of PCV stipulated in the Reactor
Facility safety Regulation, and we decided to monitor the temperature
using other devices.
*1) Based on the management of facilities stipulated at the Article 12
"Mid-term safety securing" of Act of the Regulation of Nuclear
Source Material, Nuclear Fuel Material and Reactors, it provides
"Operational Limit" and "measures required in the case that does not
satisfy the Operational Limit", it is required to respond based on
the measures required in the case that does not satisfy the
Operational Limit. In this case, in order to implement the
preservation work, it was shifted to outside of operational limit
condition [the rate of the increase in the water injection volume is
less than 1.0m3/h in any 24 hour period] as planned (from 1:55 pm on
February 12), we change the water injection amount into the reactor
of Unit 2. Later at 2:00 pm on February 17, we judged that the
Operational Limit [the temperature at the bottom of PCV is below 80
°C] has been satisfied, and corrected the judge of the deviation
from Operational Limit. We also lifted the application of the
planned shift to the outside of operational limit condition.
*2) Reactor Facility Safety Regulation provides necessary conditions
such as the numbers of the permitted machines etc. or criteria of
temperatures and pressures for securing multiple safety function for
operating reactors and for keeping nuclear power stations stable and
these are treated as conditions for operation. When there happen
some malfunctions of equipment provided in the regulation and a
nuclear power station can not clear the conditions temporarily,
operators have to take required countermeasures.
-In order to conduct inspection of the strainer changeover valve of the
pump of the reactor sea water system of Unit 6 from February 14 to
February 17, at 10:02 am on February 14, we stopped cooling of the
spent fuel pool by the spent fuel pool cooling system (B) and at 10:06
am on the same day, we stopped the pump of the reactor sea water
system (A) (spent fuel pool water temperature during the stoppage:
approx. 23°C). Because the spent fuel pool cooling system isn't in
operation during the inspection, we conduct alternating cooling of the
reactor and the spent fuel pool by the residual heat removal system.
At 2:07 pm on February 17, we finished the inspection and started the
pump of the reactor sea water system (A), and at 2:53 pm on the same
day, we resumed the cooling of the spent fuel pool by the spent fuel
pool cooling system (B), back to normal cooling condition (the maximum
temperature during the alternative cooling period: 33.6°C(water in the
reactor), 29°C(water in ths spent fuel pool).
・Fukushima Daini Nuclear Power Station:
(Units 1 to 4: shutdown due to the earthquake)
・Kashiwazaki Kariwa Nuclear Power Station: Units 6: under normal operation
(Units 1 to 5 and 7: outage due to regular inspections)
[Thermal Power Station]
・Power supply has returned to normal and the facilities damaged by the
earthquake are now being handled in a timely manner.
[Hydro Power Station]
・Power supply has returned to normal and the facilities damaged by the
earthquake are now being handled in a timely manner.
[Impacts on Transmission Facilities]
・Power supply has returned to normal and the facilities damaged by the
earthquake are now being handled in a timely manner.
[Impacts on Power Supply and Demand Balance]
This winter, there are some minus factors such as the regular inspection
of Unit 5 at Kashiwazaki-Kariwa Nuclear Power Station. On the other hand,
there are several plus factors such as the recovery of the common thermal
power stations which suffered the earthquake. As a result, we expect to
secure 53.7 GW (at the end of February) supply power.
Compared to the maximum demand in the last winter, which is 51.5 GW, we
will have 2.2 GW generation reserve margin.
We expect to maintain stable power supply this winter. However, as there
remains possibilities of unplanned shutdowns at our power stations and
growth in the demand according to the rapid change in the temperature, we
would like to ask your reasonable effort to save electricity.
We will continue to make our efforts to maintain stable operation and
maintenance of the power facilities in order to "prevent in principle" the
planned blackouts and secure power supply.
Appendix: Past Progress (As of 3:00 pm on February 17, 2012) (PDF 434KB)
Appendix: Past Progress (From March 11, 2011 to July 31, 2011) (PDF 225KB)
* Revised past progress
