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Post-quake status of the Kashiwazaki-Kariwa Nuclear Power Station (Report #15)
- Results of seismic safety evaluation following the revision of the “Guidelines for Seismic Design Evaluation” (interim report) -
A document dated September 20, 2006 was sent from the Nuclear and Industrial Safety Agency to all utilities and related organizations requesting that they conduct seismic safety evaluations according to the revised “Guidelines for Seismic Design Evaluation of Nuclear Power Reactor Facilities” (hereinafter, “New Guidelines”), accordingly, companies have been conducting such seismic safety evaluations. Furthermore, the Minister of Economy, Trade and Industry instructed that the knowledge gained from the Niigata Chuetsu-oki Earthquake, which occurred in July 2007, be reflected in the seismic safety evaluations adequately and to expedite the completion of such.
Given such background, this Report #15 will introduce the outline of seismic safety evaluation results (interim report) reported to the Nuclear and Industrial Safety Agency from utilities by the end of March this year (including outline of evaluation report by Chubu Electric Power regarding Hamaoka Unit 3 and 4, submitted to the Nuclear and Industrial Safety Agency in January/February last year).
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<Points of interim report> |
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Conducted geological surveys according to the New Guidelines (including topographical, geological, geophysical methods) and made conservative evaluations such as for the length of active faults, considering the objectives of the New Guideline. Results show the notable instances of estimating lengths longer than before, considering the possibility of multiple continuous faults. |
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Based on the active fault evaluation, the design basis earthquake ground motion, Ss, was established with consideration of “earthquake ground motion decided by identifying the hypocenter within the site” and “earthquake ground motion decided without identifying a hypocenter.” As a consequence, the design basis earthquake ground motion, Ss, based on the New Guidelines became 1.2 to 1.6 times the design basis earthquake ground motion under the former guideline, S2.
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For this interim report, based on the design basis earthquake ground motion Ss, seismic analysis was conducted on the reactor building or on the representative part of major facilities that have important safety functions and that are designated as earthquake resistance S class in order to ensure that seismic safety was secured.
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Note, the on-going review and deliberations by the Seismic and Structural Design Subcommittee of the Nuclear and Industrial Safety Subcommittee under the Advisory Committee for Natural Resources and Energy will replace this interim report and deliberations for Tokyo Electric Power Company’s Kashiwazaki Kariwa Nuclear Power Station.
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Flow of seismic safety evaluation in the interim report |
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| 2. |
Outline of evaluation results |
| (1) |
Establishing design basis earthquake ground motion Ss |
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Attachment 1 indicates the design basis earthquake ground motion Ss established by each nuclear power station in its seismic safety evaluation following the revision of the Guidelines for Seismic Design Evaluation and their approach to it.
The design basis earthquake ground motion Ss that was established this time with the New Guideline is 1.2 to 1.6 times that of the design basis earthquake ground motion under the former guidelines. Due to the meticulous surveying and review, it provides sufficient margins for safety, such as considering the possibility of multiple faults being connected.
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| (2) |
Seismic safety evaluation of facilities and other items |
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Attachment 2 indicates the results of seismic safety evaluations of facilities in representative plants at respective utilities, based on the established design basis earthquake ground motion Ss.
It was confirmed that important safety-related buildings, structures, equipment, and piping would meet evaluation standard values even when subject to design basis earthquake ground motion Ss.
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Future plan |
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At respective utilities, systematically continue to conduct seismic safety analysis for other facilities important to safety other than the major facilities of representative plants evaluated at this time and facilities important to safety at other plant not tested at this time. This will be reported to the Nuclear and Industrial Safety Agency.
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The Nuclear and Industrial Safety Agency will strictly confirm the interim reports submitted at this time through reviews of their validity at the Seismic Safety and Structural Design Subcommittee of the Nuclear and Industrial Safety Subcommittee under the Advisory Committee for Natural Resources and Energy. Subsequently, the confirmed results will be reported to the Nuclear Safety Commission.
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End |
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Japan Nuclear Technology Institute
Rev.0
April 16, 2008
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