Seismic Evaluation of Existing Nuclear Power Plants

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Seismic Evaluation of Existing Nuclear Power Plants

Author: Safety Repor ts Series No.28 | Size: 0.5 MB | Format: PDF | Quality: Unspecified | Publisher: International Atomic Energ y Agency, V ienna, 2003 | Year: 2003 | pages: 70

The IAEA nuclear safety standards publications address the site evaluation and
the design of new nuclear power plants (NPPs), including seismic hazard assessment
and safe seismic design, at the level of the Safety Requirements as well as at the level
of dedicated Safety Guides. It rapidly became apparent that the existing nuclear safety
standards documents were not adequate for handling specific issues in the seismic
evaluation of existing NPPs, and that a dedicated document was necessary. This is the
purpose of this Safety Report, which is written in the spirit of the nuclear safety
standards and can be regarded as guidance for the interpretation of their intent.
Worldwide experience shows that an assessment of the seismic capacity of an
existing operating facility can be prompted for the following:
(a) Evidence of a greater seismic hazard at the site than expected before, owing to
new or additional data and/or to new methods;
(b) Regulatory requirements, such as periodic safety reviews, to ensure that the
plant has adequate margins for seismic loads;
© Lack of anti-seismic design or poor anti-seismic design;
(d) New technical finding such as vulnerability of some structures (masonry walls)
or equipment (relays), other feedback and new experience from real
earthquakes.
Post-construction evaluation programmes evaluate the current capability of the
plant (i.e. the plant ‘as is’) to withstand the seismic concern and identify any
necessary upgrades or changes in operating procedures. Seismic qualification is
distinguished from seismic evaluation primarily in that seismic qualification is
intended to be performed at the design stage of a plant, whereas seismic evaluation is
intended to be applied after a plant has been constructed.
Although some guidelines do exist for the evaluation of existing NPPs, these
are not established at the level of a regulatory guide or its equivalent. Nevertheless,
a number of existing NPPs throughout the world have been and are being subjected
to review of their seismic safety. Rational feasible criteria for resolving the main
issues have been developed in some Member States.1

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