DS552 - Safety Evaluation of Nuclear Installations for External Events Excluding Earthquakes

Status: STEP 4

Neues Dokument

Beteiligte IAEO-Komitees: NUSSC, WASSC

Specific Safety Guide

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Background Information

SSR-2/1 (Rev. 1) requires that a comprehensive safety assessment be carried out for design of nuclear power plants. The safety assessment should investigate the capability of the design to withstand postulated initiating events and accidents – including those triggered by external hazards. Requirement 17 of SSR-2/1 (Rev. 1) requires that items important to safety be designed for protection against internal and external hazards. The external hazards include seismic, meteorological, hydrological, volcanic hazards, and human induced events.

Recommendations on seismic safety assessment are provided in SSG-89, Evaluation of Seismic Safety for Nuclear Installations, and practical guidance is provided in Safety Report No. 103, Methodologies for Seismic Safety Evaluation of Existing Nuclear Installations. Needed is a new safety guide that provides recommendations on conducting safety evaluations of nuclear installations in relation to external events other than earthquakes.

This new publication will provide recommendations on methodologies for the safety assessment for external events excluding earthquakes, validated by the current international state of the practice and intended to meet the requirements for nuclear facilities established in SSR-1 (e.g., Requirements 7), SSR-2/1 (Rev. 1) (e.g., Requirements 10 & 17), SSR-3 (e.g., Requirements 5, 18, 20 & 22) and SSR-4 (e.g., Requirements 16, 20 & 21), in relation to external events such as high wind and tornadoes, flooding, extreme temperatures, volcanic activity, and accidental human induced external events as well as combinations of external events hazards. Additionally, this safety guide will provide guidance which can be used to address the impact of climate change on meteorological and hydrological hazards.

This safety guide is complementary to SSG-68 Design of Nuclear Installations Against External Events Excluding Earthquakes. SSG-68 is focused on design of installations for external events, whereas this new safety guide will focus on safety assessments and not design.

This new safety guide will:

• provide specific recommendations on the conduct of safety assessments for both new and existing nuclear installations in relation to external events other than earthquakes;
• appropriately reflect lessons learned based on applied practices following the Great East Japan Earthquake and Tsunami of 2011 and the subsequent Fukushima Daichi accident;
• address the use of a graded approach to safety evaluation of nuclear installations other than nuclear power plants in relation to external hazards excluding earthquakes;
• cover both new and existing nuclear installations;
• address the need for maintenance of the safety assessment of the nuclear installation throughout its life cycles. Re-evaluation of the safety assessment may be triggered by new information, advanced methodologies, or regulatory requirements;
• address external events in the safety evaluation of nuclear installations taking into account all operational and accidental conditions for those external events outlined in SSG-68 to include natural external events (e.g. floods, extreme meteorological conditions, extreme winds, volcanism), human induced external events (e.g. aircraft crashes, external explosions, external fire) and combinations of external hazards.

Recommendations on the conduct of safety assessments which address of malevolent acts will not be provided in the proposed publication.