Press Release
Regarding Earthquake Countermeasures at Switching Stations, etc. for Ensuring Reliability of External Power at Hamaoka Nuclear Power Station (Report Concerning Directive of the METI's NISA)
July 07, 2011
Chubu Electric Power Co.,Inc.
This is to announce that Chubu Electric Power today submitted a report to the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency that summarizes earthquake countermeasures at switching stations, etc. to ensure reliability of external power at Hamaoka Nuclear Power Station. The report is in response to the directive of the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency*1, which was issued following damage to circuit breakers and other equipment at switching stations at the Tokyo Electric Power Co., Inc.'s Fukushima Daiichi Nuclear Power Station when it was shaken by the Tohoku-Pacific Ocean Earthquake of March 11, 2011.
1. Content of Nuclear and Industrial Safety Agency directive
(1) In light of results of analysis of earthquake observation records at the Tokyo Electric Power Co., Inc.'s Fukushima Daiichi Nuclear Power Station during the Tohoku-Pacific Ocean Earthquake of 2011, do an impact assessment of the possibility of a switching station or other electric facility experiencing collapse, damage, etc. that would cause its functional failure at a nuclear power station, etc. of a general electric utility, etc.
When doing this assessment, set the standard seismic force on the ground surface of switching stations, etc. for each power station, then determine the stress on the electric facility by analysis and assess it by comparison to the structural strength of that electric facility.
(2) If the assessment described in (1) above finds a possibility of collapse, damage, etc. that would cause functional failure, decide on earthquake countermeasures for the affected facilities.
2. Report content
(1) Facilities subject to assessment
Although the mechanism, etc. of how the circuit breakers, etc. at Fukushima Daiichi Nuclear Power Station, Reactors No. 1 and 2 were damaged in this event are not understood in detail, in light of the damage to circuit breakers, etc., it has been decided to do impact assessments of similar switching station facilities at Hamaoka Nuclear Power Station.
Additionally, nuclear power stations have transformers that convert the voltage of electrical power after it is received at the switching station facility, and this includes some large equipment. Therefore it was decided to do impact assessment on a scenario of strong excitation force from an earthquake.
(2) Impact assessment technique
It was decided to do assessments according to the Japan Electrical Manufacturers' Association standard JEAG 5003-2010, "Electric Facility Seismic Design Guideline for Substations, Etc." and check equipment design tolerance (the ratio of stress occurring at each component to that component's allowable stress).
(3) Assessment results
Switching stations and transformer equipment at Hamaoka Nuclear Power Station were each found to have more than the set level of tolerance and therefore assessed as having a low possibility of collapse, damage, etc. that would cause functional failure.
(4) Future measures
Because there are still unknowns about the damage to the circuit breakers, etc. at Fukushima Daiichi Nuclear Power Station, Reactors No. 1 and 2, including the response spectrum and damage mechanism, the Tokyo Electric Power Co., Inc. is doing a detailed assessment of this.
When the results of that evaluation are known, a new study will be performed that includes checking whether the new knowledge needs to be reflected, and the results of that study will be reported to the Nuclear and Industrial Safety Agency.
*1 Directive of the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency: "Regarding Earthquake Countermeasures at Switching Stations, etc. for Ensuring Reliability of External Power Supply to Nuclear Power Stations (Direction)," issued by the Ministry of Economy, Trade and Industry's Nuclear and Industrial Safety Agency on June 07, 2011 (06.07.2011 NISA Number 1).