1.1.1 This guide explains and refines the relevant clauses of HAF 102 Safety specifications for design of nuclear power plant (hereinafter referred to as Specifications), and provides guidance on the design of fire and explosion protection in nuclear power plant for the nuclear power plant designer and licence applicant.
1.1.2 The annexes to this guide are informative.
1.2 Scope
1.2.1 This guide is applicable to land-based stationary thermal-neutron reactor nuclear power plants. It may be referenced by other types of nuclear power plants in terms of their internal design of fire and explosion protection.
1.2.2 This guide only covers the internal design measures of fire and explosion protection adopted to protect items important to safety of nuclear power plants, excluding the general requirements for fire control, personnel safety protection and property protection in nuclear power plants.
1.2.3 The contents related to explosion protection in this guide focus on the protection of explosion caused by flammable liquids and gases released from systems and components of nuclear power plants, but not the protection of system and component explosion. The explosion protection problem of systems and components shall be solved through their own design.
2 General principles
2.1 General
2.1.1 The Specifications specifies basic requirements for the fire-fighting system of nuclear power plants. In the design and layout of structures, systems and components which are important to safety in nuclear power plants, attention shall be paid to reduce the possibility and result of internal fires and explosions caused by internal and external events. The ability to shutdown, remove waste heat, confine radioactive substances and monitor the status of nuclear power plants shall be held. The following objectives shall be achieved by using an appropriate combination of multiple components, various systems, physical isolation and fault safety:
(1) prevention of fire;
(2) rapid detection and extinguishing of the occurred fire, thus limiting the fire damage;
(3) prevention of the un-extinguished fire from spreading, thus minimizing its influence on the system that implements important safety functions.
2.1.2 The design of fire protection in nuclear power plants shall meet the following requirements:
(1) minimizing the probability of fire occurrence;
(2) realizing early detection and extinguishing of fire through combination of automatic and/or manual fire control;
(3) preventing fires from spreading by using fire barriers and physical members or by spatial isolation.
2.1.3 The design of explosion protection shall follow the following steps:
(1) prevent explosion;
(2) if the explosive environment is inevitable, minimize the risk of explosion;
(3) adopt design measures to limit the consequence of explosion.
Where steps (1) and (2) cannot be implemented, step (3) shall be adopted.
2.1.4 Multiple safety systems shall be included in the design of nuclear power plants to prevent postulated initiating events (e.g. fire or explosion) from disturbing safety systems to implement specified safety functions. Where the multiplicity and diversity of safety systems are reduced, protective measures against fire and explosion shall be strengthened for each safety system. In terms of fire, its protection is generally realized by passive protection, improvement of physical isolation and/or application of more automatic fire alarm systems and fire extinguishing systems.
2.1.5 The design of fire protection shall be carried out according to the following assumptions:
(1) fires may occur at any place where fixed or temporary combustible materials are present;
(2) the fire occurred at the same time is taken as a single event and subsequent fire spread shall be considered as its constituent part;
(3) fires may occur in nuclear power plants under any normal operating state.
In addition, consideration shall be given to fires and the combination of postulated initiating events that may be independent of fires (see 2.5).
2.1.6 Fire hazard analysis shall be conducted to prove that the design of nuclear power plants meets the safety objective specified in 2.1.1. The scope and guidance of fire hazard analysis are detailed in 3.5.
2.2 Fire prevention
2.2.1 The nuclear power plants shall keep at a reasonable and feasible minimum fire load. The material of nuclear power plants shall be non-combustible as much as possible, otherwise flame retardant.
2.2.2 The number of ignition sources shall be minimized.
2.2.3 For the systems of nuclear power plants, their design shall guarantee as much as possible that no fire will be caused by system failure.
2.2.4 For items important to safety whose function failure or fault may cause unacceptable release of radioactive substances, corresponding protective measures shall be taken to protect them from fire hazards caused by natural phenomena such as lightning.
2.2.5 Design measures shall be taken for the proper storage of temporary combustible materials in operation to keep them away from items important to safety or necessary protective measures shall be taken. For the guidance on fire protection during the operation of nuclear power plants, see relevant guides given in Fire safety for the operation of nuclear power plant.
