Protection against Internal Hazards in the Design of Nuclear Power Plants

Specific Safety Guide

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• Publisher: International Atomic Energy Agency
• Year: 2021
• eBook ISBN: 9789201162212
• Topic: Technology & Engineering
• Subtopic: Mechanical Engineering
• Index: Technology & Engineering

Internal hazards have to be considered in the design of items important to safety in a nuclear power plant. The objective is to provide appropriate features to prevent internal hazards and mitigate their effects to ensure that safety is not compromised. This Safety Guide provides recommendations to regulatory bodies, nuclear power plant designers and licensees on hazard assessment (including for combinations of hazards) and design concepts for protection against internal hazards in nuclear power plants, in order to meet the requirements established in IAEA Safety Standards Series No. SSR 2/1 (Rev. 1), Safety of Nuclear Power Plants: Design. The following internal hazards are reviewed in this Safety Guide: fires, explosions, missiles, pipe breaks, flooding, collapse of structures and falling objects with a focus on heavy load drop, electromagnetic interference and release of hazardous substances originating from within the site boundary.

1. INTRODUCTION

Background

1.1. This Safety Guide provides recommendations on how to meet the requirements established in IAEA Safety Standards Series No. SSR-2/1 (Rev. 1), Safety of Nuclear Power Plants: Design [1], in relation to protection against internal hazards in the design of land based stationary nuclear power plants with water cooled reactors.

1.2. This Safety Guide is a revision and merger of IAEA Safety Standards Series No. NS-G-1.11, Protection against Internal Hazards other than Fires and Explosions in the Design of Nuclear Power Plants1, and IAEA Safety Standards Series No. NS-G-1.7, Protection against Internal Fires and Explosions in the Design of Nuclear Power Plants2, both of which are superseded by this Safety Guide. This revision principally consists of updating the technical content to make it consistent with the requirements established in SSR-2/1 (Rev. 1) [1]. In addition, internal hazards due to electromagnetic fields or electromagnetic interference, and those due to the release of hazardous substances originating from within the site boundary are included in the scope of this Safety Guide.

Objective

1.3. The objective of this Safety Guide is to provide recommendations to regulatory bodies, nuclear power plant designers and licensees on hazard assessment (including for combinations of hazards) and design concepts for protection against internal hazards in nuclear power plants, in order to meet the requirements established in SSR-2/1 (Rev. 1) [1].

Scope

1.4. This Safety Guide applies primarily to land based stationary nuclear power plants with water cooled reactors designed for electricity generation or for other heat production applications (such as district heating or desalination). For innovative developments in future systems, for plant modifications or for other reactor types, some parts of this Safety Guide might not be fully applicable or might need some judgement in their interpretation.

1.5. This Safety Guide covers the design features necessary to protect items (i.e. structures, systems and components (SSCs)) important to safety in nuclear power plants against the effects of internal hazards during all modes of operation. The following internal hazards are reviewed in this Safety Guide: fires, explosions, missiles, pipe breaks, flooding, collapse of structures and falling objects with a focus on heavy load drop, electromagnetic interference and release of hazardous substances originating from within the site boundary.

1.6. This Safety Guide does not cover conventional industrial safety, except where this could affect the safety of the nuclear power plant.

1.7. The recommendations provided in this Safety Guide are targeted primarily at new nuclear power plants. For plants designed with earlier standards, it is expected that in the safety assessments of such designs a comparison will be made with the current standards (for example as part of the periodic safety reassessment for the plant), to determine whether the safe operation of the plant could be further enhanced by means of reasonably practicable safety improvements: see para. 1.3 of SSR-2/1 (Rev. 1) [1].

Structure

1.8. Section 2 outlines general considerations for protection against internal hazards in nuclear power plants. Section 3 provides general design recommendations for protection against internal hazards in nuclear power plants. Section 4 provides specific recommendations for protection against fires, explosions, missiles, pipe breaks, flooding, collapses of structures and falling objects with a focus on heavy load drop, electromagnetic interference and release of hazardous substances originating within the site boundary. Appendix I provides guidance on dealing with hazard combinations. Appendix II provides detailed guidance on protection against internal fires.

2. GENERAL CONSIDERATIONS

2.1. Requirement 17 of SSR-2/1 (Rev. 1) [1] states:

“All foreseeable internal hazards and external hazards, including the potential for human induced events directly or indirectly to affect the safety of the nuclear power plant, shall be identified and their effects shall be evaluated. Hazards shall be considered in designing the layout of the plant and in determining the postulated initiating events and generated loadings for use in the design of relevant items important to safety for the plant.”

2.2. Paragraph 5.16 of SSR-2/1 (Rev. 1) [1] states:

“The design shall take due account of internal hazards such as fire, explosion, flooding, missile generation, collapse of structures and falling objects, pipe whip, jet impact and release of fluid from failed systems or from other installations on the site. Appropriate features for prevention and mitigation shall be provided to ensure that safety is not compromised.”

2.3. Sections 3 and 4 of this Safety Guide provide general design recommendations and specific design recommendations, respectively, to meet Requirement 17 and the requirements established in para. 5.16 of SSR-2/1 (Rev. 1) [1] reg...

Table of contents

• 1. INTRODUCTION
• REFERENCES
• CONTRIBUTORS TO DRAFTING AND REVIEW