Press Release
Ensuring Reliability of External Power at Hamaoka Nuclear Power Station(Report Concerning Directive of the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency)
May 16, 2011
Chubu Electric Power Co.,Inc.
This is to announce that, following a directive*1 from the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency, Chubu Electric Power has summarized its plan for ensuring the reliability of external power at Hamaoka Nuclear Power Station and today submitted its report to the Nuclear and Industrial Safety Agency. (The agency's directive was issued in light of the loss of external power at the Higashidori Nuclear Power Station of Tohoku Electric Power Co., Inc. and the Rokkasho Reprocessing Plant of Japan Nuclear Fuel Limited due to an earthquake on April 7, 2011 off the coast of Miyagi Prefecture.)
1. Content of Nuclear and Industrial Safety Agency directive
(1) Considering the possibility of supply disruptions, etc. resulting from earthquake or other event impacting the external power supply to Hamaoka Nuclear Power Station, conduct an analysis and evaluation of power system supply reliability that could impact the electric power supply to Hamaoka Nuclear Power Station, and in light of this analysis and evaluation, consider measures for further enhancing electric power supply reliability to Hamaoka Nuclear Power Station (including measures to strengthen on-grounds power sources at the station).
(2) To help enhance the reliability of the power supply to each reactor at the Hamaoka Nuclear Power Station, connect all transmission circuits for multiple power lines to each reactor so that they can provide power.
(3) Conduct an evaluation on the seismic resistance and foundation stability, etc., against earthquakes of power line transmission towers at Hamaoka Nuclear Power Station, and take the necessary response such as reinforcement as based on the results.
(4) Take countermeasures to prevent tsunami impacts at switching stations and other electrical equipment at Hamaoka Nuclear Power Station, such as by placing them indoors and making facilities watertight.
2. Report content
(1) Analysis and evaluation of power system supply reliability that could impact the electric power supply to Hamaoka Nuclear Power Station
The electric power supply system to Hamaoka Nuclear Power Station consists
of three routes and six lines to Reactors No. 3 and 4, and two routes and four
lines to Reactor No. 5, thus ensuring high reliability.
Additionally, analysis
and evaluation were done anticipating three scenarios: (1) a complete power
outage at a substation connected to Hamaoka Nuclear Power Station, or another
bottleneck substation (one substation) (the extreme case); (2) an accident at
a generating line at a substation connected to Hamaoka Nuclear Power Station,
or another bottleneck substation (the severe case); and (3) one transmission
line route gets cut off (the standard case). We judged that in all cases, the
electric power system supplying Reactors No. 3-5 would be ensured, and that
the current electric power supply ensures sufficient reliability.
(2) Connecting all circuits of multiple power lines to each reactor
As the on-grounds power supply circuits are currently structured at Hamaoka Nuclear Power Station, Reactors No. 3 and 4 can receive power from all transmission lines connected to the station (four 500 kV transmission line circuits and two 275 kV transmission line circuits). Although Reactor No. 5 can receive power from the four 500 kV transmission line circuits, which is considered highly reliable, we will set up an on-grounds power source circuit so that it can receive power from the 275 kV transmission line as well. As a result, all transmission circuits of the power lines will be connected to each reactor, thus enhancing electric power supply reliability.
(3) Evaluation of seismic resistance, etc. of power line transmission towers, and countermeasures
Japan's transmission towers, which were designed for wind load,*2 have sufficient
seismic resistance, and none of them have collapsed as a result of seismic motion
during major earthquakes, including the Great East Japan Earthquake of March
11, 2011. Therefore, we have judged that our transmission towers designed for
wind load, including the transmission lines that supply power to Hamaoka Nuclear
Power Station, are sufficiently safe against seismic motion.
However, in light of the fact that transmission problems occurred because
of breakage of long rod support insulators during the Great East Japan Earthquake,
we will replace the long rod support insulators with dangling support insulators
so that similar transmission problems do not occur on transmission lines supplying
power to Hamaoka Nuclear Power Station.
Our judgment is that there is no problem at this time with foundation stability.
Because there is a large embankment in one area near a transmission tower, we
will promptly confirm the stability of this embankment to evaluate its impact
on the tower.
(4) Tsunami impact prevention measures at switching stations, etc.
In light of the situation at Tokyo Electric Power Co., Inc.'s Fukushima Daiichi Nuclear Power Station, we conducted a study anticipating flooding on the Hamaoka Nuclear Power Station grounds. As a result, we will be building a new transformer on a high location in order to provide a high voltage power source (6.9 kV) from the 500 kV switching station on high ground (T.P. + 25 m) to Reactors No. 3-5.
*1 Directive of the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency: "Ensuring Reliability of External Power at Nuclear Power Stations and Reprocessing Facilities (Directive)" (April 15, 2011, NISA No. 3), issued by the Nuclear and Industrial Safety Agency, Ministry of Economy, Trade and Industry.
*2 Wind load: Refers to pressure caused by wind; this wind pressure is calculated by a method prescribed in technical standards relating to electrical equipment as based on the Electric Utility Law.