Due to the Tohoku-Chihou-Taiheiyou-Oki Earthquake which ocurred 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) - From February 2, tendency of temperature rise at the bottom of PCV has
been observed. While we increased the water injection to the reactor
and have been monitoring the trend of the temperature, it is still high
around 70°C. On February 6, we sampled the gas by the gas control
system of Unit 2 Primary Containment Vessel. The density of Xenon 135
at the entrance of the system was below the detection limit. Since it
is below 1Bq/cm3, which is the threshold for judging re-criticality,
we confirmed the reactor didn't go re-critical, however, in order to
avoid the possibility of going re-critical being increased as a result
of the water density in the reactor being increased by rapid injection
of cold water is increased, we injected the boric acid into the reactor
as a safety countermeasure from 0:19 am to 3:20 am on February 7, which
was before we increased the volume of the water injection. At 4:24 am
on the same day, we changed the amount of the core spray system
injection water from 3.7m3/h to 6.7m3/h (the amount of the continuing
feed water system injection is 6.8m3/h). After that, we continued to
monitor the temperature tendency, finding that the temperature slowly
increased. At 10:45 pm on February 11, we changed the water injection
amount through the reactor feed water system from approx. 6.8m3/h to
7.8m3/h (the water injection amount through the core spray system is
kept at approx. 6.8m3/h). On February 12, we conducted a sampling of
gas in the gas management system in the Primary Containment Vessel of
Unit 2 and the result is that around the entry of the system, Xe-135
was below the detection limit (9.5 x 10-2 Bq/cm3). As it is below 1
Bq/cm3, the criterion to judge re-criticality, we have confirmed that
it has not reached re-criticality. After that, we continued monitoring
the tendency of the temperature fluctuation, and then found that the
temperature at the bottom of PCV tended to be still high. Therefore,
in order to avoid a chance of the re-criticality due to the increase
of water density in the PCV by sudden cold water injection, from 11:38
am to 1:50 pm on February 12, before starting water flow rate change,
we injected boric acid into the reactor for the safety measures. Then,
from 2:10 pm on the same day, although we increased the water injection
rate, the indicated temperature of the bottom of PCV was confirmed to
be 82°C beyond 80 °C so that, At 2:20 pm, we judged that it was not
satisfied "the temperature is below 80 °C at the bottom of PCV *1",
which is stipulated in "the Reactor Facility safety Regulation *2" as
one of the "Conditions of operation". Thereafter, we continued the
increased water injection, and changed the water flow rate from approx.
7.2m3/h to 7.5m3/h through the reactor feed water system, and from
approx. 6.9m3/h to 9.9m3/h through the core spray system. Currently,
the temperature is approx. 79.2 °C as of 3pm on February 12 for
reference. We continue to monitor the tendency of the temperature. *1) 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. *2) 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 our case, in order to implement the
preservation work, it was shifted to outside of operational limit
condition as planned (from 1:55 pm on February 12), we change the
water injection amount into the reactor of Unit 2. At 2:20 pm, we
judged that it was not satisfied "the temperature is below 80 °C
at the bottom of PCV ", which is stipulated in "the Reactor
Facility safety Regulation" as one of the "Conditions of operation".
as the indicated temperature was 82 °C beyond 80 °C. We continue
to change the water injection amount accordingly.· 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 3:30 pm on February 12, 2012) (PDF 425KB)
Appendix: Past Progress (From March 11, 2011 to July 31, 2011) (PDF 225KB)
* Revised past progress
