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 since the previous press release 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)
· Since December 22, 2011, the atmospheric temperatures at point C
of Unit 1 Primary Containment Vessel (PCV) monitored by the Containment
Atmospheric Monitoring System had risen (the atmospheric temperature of
the PCV on December 22 was approx. 38°C, at 7 pm on December 27 was
approx. 49°C). The other temperatures had not risen, so we conducted a
survey checking the reliability of the meters from 9 am to 10 am on
December 28, and we confirmed that there are no problems. From 11:00am
to 12:15pm on the same day, we adjusted the volume of Nitrogen injection,
from approx. 8 m3/h to approx.18 m3/h, and emission of the gas management
system, from approx. 23 m3/h to approx.30 m3/h, in order to identify the
cause by monitoring the system with the same injection and emission
volume as before December 22. The temperature went up to approx. 54.6°C
at 6 pm on December 28 and fell to approx. 43.3°C at 11:00 am on January
2, 2012. Temperatures at other two points also indicated slight increases
but are currently in the stable status.
Point D: (Maximum) approx. 35.8°C at 5:00 pm on December 29, 2011 →
approx. 32.6°C at 11:00 am on January 2, 2012.
Point E: (Maximum) approx. 40.0°C at 5:00 pm on December 29, 2011 →
approx. 35.8°C at 11:00 am on January 1, 2012.
We will continuously conduct the survey for the cause of temperature
increase and surveillance of the plant.
· At approx. 5:30 pm on January 1, 2012, we observed approx. 240 mm
decrease in the water level of the skimmer surge tank*1 of Unit 4 spent
fuel pool in the three hours between 2:00 pm to 5:00 pm (According to the
operation record so far, there had been an approx. 50 mm decrease.). As a
result of the site investigation later, we did not observe any leakage
around the Unit 4 reactor building, connecting points of primary system
pipes of Unit 4 spent fuel pool alternative cooling system, or its
installation space. The water temperature of Unit 4 spent fuel pool as of
5:00 pm on January 1 is 23°C (22°C as of 5:00 am on January 2). The spent
fuel pool alternative cooling system is still in operation and there is
no problem in cooling the reactor. Though the water level of the spent
fuel pool is kept stable without any problem, the water level in the
skimmer surge tank continues decreasing. Therefore, from 10:27 pm to
11:13 pm on January 1, we filled water in the skimmer surge tank. At
present, the water level in the skimmer surge tank keeps decreasing
approx. 90mm/hour. We will strengthen surveillance on observation of the
water level in the skimmer surge tank, increasing the frequency to once
in an hour from once in three hours. At the same time, we will continue
examination of the causes of the decrease in the water level, such as
site investigations based on such possibilities as the water may flow
into the reactor well*2 from the spent fuel pool.
At present, no leakage is observed outside the building. No significant
change is observed in the water level of the accumulated water in the
building.
By further investigation, we confirmed that amount of water that is
equivalent to decreased water level of the skimmer surge tank and amount
of water that is equivalent to increased water level of the reactor well*2
are almost the same and the water level at reactor well is lower than
that of the spent fuel pool. With these facts, we estimate that
situation of gate between the reactor well and the spent fuel pool
changed and water flow from the spent fuel pool to the reactor well
increased made decrease in water flow from the spent fuel pool to the
skimmer surge tank, and so decrease in water level at the skimmer surge
tank was more than usual. To decrease the difference between the water
level of the reactor well and that of the spent fuel pool, we put water
into the reactor well from 11:50 am to 11:59 am on January 2. As of 4:00
pm, we can not find decrease in the water level of the skimmer surge tank.
We will continue surveillance the water level of the skimmer tank.
*1 The tank installed in order to receive the water overflows from the
spent fuel pool. The water in the spent fuel pool is overflowed into
the skimmer surge tank in order to cool the fuel assembly and remove
impurities in the water. The water returns to the spent fuel pool
after passing through the heat exchanger and the filter.
*2 The reactor well is the space which contains the reactor pressure
vessel and the lid of the reactor containment vessel. During the
periodical inspections, the space filled with water and the fuel is
changed.
· Fukushima Daini Nuclear Power Station:
Units 1 to 4: shutdown due to the earthquake
· Kashiwazaki Kariwa Nuclear Power Station: Units 5, 6: under normal
operation
(Units 1 to 4 and 7: outage due to regular inspections)
[Thermal Power Station]
· Power supply has returned to normal and facilities damaged by the
earthquake are now being handled in a timely manner.
[Hydro Power Station]
· Power supply has returned to normal and facilities damaged by the
earthquake are now being handled in a timely manner.
[Impacts on Transmission Facilities]
· Power supply has returned to normal and facilities damaged by the
earthquake are now being handled in a timely manner.
[Impacts on Power Supply and Demand Balance]
This winter, there will be some minus factors such as the regular
inspection of Unit 5 at Kashiwazaki-Kariwa Nuclear Power Station. On the
other hand, there will be several plus factors such as the recovery of the
common thermal power stations which suffered the earthquake. As a result,
we expect to secure 54.9 GW (at the end of December), 54.6 GW (at the end
of January), 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 - 3.4 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 4:00 pm, January 2, 2012) (PDF 263KB)
Appendix: Past Progress (From March 11, 2011 to July 31, 2011) (PDF 225KB)
* Revised past progress