标准编号:	HAD102/11-2019
中文名称:	核动力厂防火与防爆设计
英文名称:	Design of fire and explosion protection in nuclear power plant
行业分类:	HAD    核电行业标准
发布机构:	国家核安全局
发布日期:	2019-12-31
实施日期:	2019-12-31
标准状态:	现行
替代旧标准:	HAD102/11-1996
翻译语言:	英文
文件格式:	PDF
中文字符数:	30000 字
翻译价格(元):	3000.00 元
交付时间:	付款后 1 个工作日

1 Introduction



1.1 Purpose



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.



2.3 Automatic fire alarm and fire extinguishing systems



2.3.1 There shall be automatic fire alarm and fire extinguishing systems, and other necessary systems determined by fire hazard analysis (see 3.5). In case of a fire, the automatic fire alarm and fire extinguishing systems shall give an alarm and/or extinguish the fire in time and minimize the adverse influence of fire on items important to safety and working personnel.



2.3.2 The fire extinguishing system shall be able to start automatically when necessary. The design and layout of fire extinguishing system shall guarantee that its operation, breakage or misoperation will not (1) affect the function of structures, systems and components important to safety, (2) damage the protective measures of critical accidents and (3) affect multiple safety systems at the same time, so as to ensure the effectiveness of measures adopted for meeting single fault criterion.



2.3.3 Consideration shall be given to the possibility of fire extinguishing system fault and the influence of system effluent from places adjacent to fire compartments or adjacent fire cells.



2.3.4 Appropriate emergency lighting and communication equipment shall be set up to ensure the smooth implementation of manual fire extinguishing action.



2.4 Fire confinement and mitigation of fire consequences



2.4.1 Multiple components of safety systems shall be fully isolated to ensure that the fire will only affect a certain series of the safety systems and will not prevent another redundant series from performing safety functions. Each redundant series of safety systems may be placed in an independent fire compartment, or at least in an independent fire cell, to achieve the above objectives (see 3.3-3.4). The number of penetrating components between fire compartments shall be minimized.



2.4.2 The consequence of hypothetical fires shall be analyzed for all areas provided with safety systems and other parts posing fire hazards to safety systems. In the analysis, it should be assumed that the functions of all safety systems in the fire compartment or fire cell where hypothetical fires are located are all failed, except that the safety systems are protected by qualified fire barriers or can take the consequences of the fire. For the exceptional case, the rationality of the analysis shall be proved.



2.4.3 The automatic fire alarm system, fire extinguishing system and their supporting systems (such as ventilation and drainage systems) in each fire compartment shall be as independent as possible from their corresponding parts in other fire compartments to maintain the operability of these systems in adjacent fire compartments.



2.5 Event combination



2.5.1 If the probabilistic safety analysis can prove that the frequency of random combination of certain extremely unlikely events is so low as to be negligible, such event combination may not be considered as a postulated accident.



2.5.2 In the design of fire-fighting system and equipment, consideration shall be given to the combination of fire and other postulated initiating events that may be independent of fire and appropriate countermeasures shall be taken. For example, for the combination of loss of coolant accident and independent fire events, consideration shall be given to the independent fires in the long-term stage after the accident, but not to the combined independent fires in short-term stages such as accident occurrence and mitigation system startup.



2.5.3 A postulated initiating event shall not lead to a fire that endangers any safety system. The possible causes of the fire shall be determined in the fire hazard analysis, such as serious earthquakes or the disintegration of steam turbine generators, and specific countermeasures (e.g. adopting cable wrapping, automatic fire alarm system, fire extinguishing system, etc.) shall be taken if necessary. In the fire hazard analysis, special attention shall be paid to the possibility of failure of high-temperature equipment and pipelines conveying flammable liquids and gases.



2.5.4 Fire-fighting systems and equipment that still need to maintain their functions (e.g. integrity, and/or functionality, and/or operability) under various effects of the postulated initiating events shall be identified, and they shall be properly designed and qualified so that they have the appropriate capability to resist the impact of postulated initiating events.



2.5.5 For the fire-fighting systems and equipment that do not need to maintain their functions after a postulated initiating event, their design and qualification shall ensure that their failure modes will not endanger nuclear safety related items.



2.6 Protection against explosion hazards



2.6.1 The explosion hazards of nuclear power plants shall be eliminated as much as possible through design. Measures to prevent or limit the formation of explosive environment shall be given priority in the design.



2.6.2 Flammable gases, combustible liquids and combustible materials that may produce or contribute to the production of explosive mixed gases shall be excluded from fire compartments, fire cells, areas adjacent to fire compartments and fire cells, and areas connected through ventilation systems as far as possible. If this is impossible, the quantity of these materials shall be strictly limited, sufficient storage facilities shall be provided, and the active substances, oxidizing agents and combustible materials shall be isolated from each other. Compressed flammable gas cylinders shall be properly stored in a special enclosure far away from the main plant building and shall be properly protected according to the local environmental conditions. The automatic fire alarm system, automatic flammable gas detection system and automatic fire extinguishing system shall be set up to prevent fire-induced explosion from affecting the items important to safety in other plant buildings.



2.6.3 The explosion hazards shall be identified for fire compartments, fire cells and other areas that are obviously affected by explosions. In identifying explosion hazards, consideration shall be given to the physical explosion (such as rapid air expansion caused by high-energy electric arc), chemical explosion (such as gas mixture explosion and oil-filled transformer explosion) and explosion caused by fire, as well as the effect of postulated initiating events (such as rupture of flammable gas transmission pipeline).



2.6.4 Appropriate electrical components (such as circuit breakers) shall be selected, and the probability, size and duration of electric arc may be limited by design to minimize the harm of physical explosion.



2.6.5 If the formation of explosive environment is inevitable, appropriate design or necessary operation procedures shall be adopted to minimize risks. Relevant measures include: limiting the volume of explosive gas, eliminating ignition sources, sufficient ventilation, selecting electrical equipment suitable for explosive environment, inerting, explosion venting (such as explosive plates or other pressure-relief devices) and isolation from items important to safety. Equipment that need to maintain their functions after a postulated initiating event shall be identified, and appropriately designed and qualified.



2.6.6 The risk of fire-induced explosion (e.g. explosion caused by boiling liquid expansion vapor explosion) shall be minimized by isolating potential fire from potential explosive liquids and gases, or by active measures (e.g. fixed water-based fire extinguishing system capable of providing cooling and vapor diffusion). Consideration shall be given to the positive pressure of shock wave and projectiles generated by the boiling liquid expansion vapor explosion, as well as the possibility of gas cloud explosion caused by ignition of flammable gas far away from the release point.



2.6.7 Explosion hazards that cannot be eliminated shall be identified and design measures shall be taken to limit explosion consequences (e.g. overpressure, generation of projectiles or fires). The influence of hypothetical explosion on safety systems shall be evaluated according to the requirements of 2.1.1. In addition, the evacuation and rescue routes for personnel in main control room and auxiliary control room shall also be evaluated. If necessary, specific design measures shall be adopted.



3 Plant building design



3.1 General



3.1.1 In order to ensure the reflection of fire safety objectives mentioned in Clause 2 in the design of nuclear power plants, this clause describes the necessary design activities.



3.2 Layout and construction



3.2.1 In the early stage of design, the plant building shall be divided into fire compartments which isolate items important to safety from high fire loads and isolate multiple safety systems from each other. By isolation, the risk of fire spread is reduced, the secondary effect of fire is reduced, and common mode faults are prevented.



3.2.2 Plant building structures shall have appropriate fire resistance. The fire stability grade (bearing capacity) of plant building structural components that are placed in or constitute the boundary of the fire compartment shall not be inferior to the fire- resistance requirements of the fire compartment itself.



3.2.3 Non-combustible or flame-retardant and heat-resistant materials shall be used as far as possible in the whole nuclear power plant (especially in reactor containment and control room).



3.2.4 A list of combustible materials and their locations in the plant building shall be established at the initial stage of design. This list is an important input for fire hazard analysis and shall be continuously updated throughout the service life of the nuclear power plant.



3.2.5 Combustible materials shall be avoided as far as possible near the items important to safety.



3.2.6 Adequate evacuation and rescue routes shall be arranged (see Annex II).



3.3 Application of fire compartments: fire blocking method



3.3.1 In order to embody the isolation principle described in Clause 2 and isolate items important to safety from high fire loads and other fire hazards, priority shall be given to arranging multiple items important to safety in mutually isolated fire compartments. This method is called fire blocking method.



3.3.2 A fire compartment is a plant building or area completely surrounded by fire barriers. The fire resistance of the fire barrier in fire compartment shall be high enough to keep the fire barrier undamaged even when the fire load therein is completely burnt.



3.3.3 The fire shall be confined in the fire compartment to prevent the fire and its effects (such as smoke and heat) from spreading between fire compartments, so as to avoid the simultaneous failure of multiple items important to safety.



3.3.4 The isolation provided by fire barriers shall be reliable and shall not be weakened by the temperature or pressure effect of fire on common plant building components (such as building equipment system or ventilation system).



3.3.5 Since any penetrating component will reduce the reliability and overall effect of fire barriers, the number of penetrating components shall be minimized. For passage blocking devices (such as fire doors, fire dampers, containment gates and fire blocks) and fire compartment boundaries that form part of the fire barrier, their fire resistance shall be at least the same as that required by the fire barrier itself.



3.3.6 For the fire compartment adopting fire blocking method, a fire extinguishing system shall be set up in the area with high fire load determined by fire hazard analysis to control the fire as soon as possible.



3.3.7 The fire resistance of the fire barrier constituting the boundary of fire compartment shall be determined in the fire hazard analysis, and it shall be at least 60min. Annex III provides relevant information on fire barriers and penetrating components.

1 Introduction
2 General principles
3 Plant building design
4 Fire preventive measures and explosion hazard control
5 Automatic fire alarm and fire extinguishing systems
6 Mitigation of the secondary effect of fires
7 Safety classification and quality assurance
Terms and definitions
Annex I Application of fire blocking method and fire extinguishing method
Annex II Evacuation and rescue routes
Annex III Fire barriers
Annex IV Cable fire protection
Annex V Fire detectors
Annex VI Automatic water sprinkler and water mist spray systems
Annex VII Gas fire extinguishing system

核动力厂防火与防爆设计
（2019 年 12 月 31 日国家核安全局批准发布）

本导则自 2019 年 12 月 31 日起实施 本导则由国家核安全局负责解释


本导则是指导性文件。在实际工作中可以采用不同于本导则 的方法和方案，但必须证明所采用的方法和方案至少具有与本导 则相同的安全水平。




1 引言
1.1 目的

1.1.1 本导则是对《核动力厂设计安全规定》（HAF 102，以 下简称《规定》）中有关条款的说明和细化，为核动力厂设计单位 和执照申请者提供关于核动力厂内部防火与防爆设计的指导。
1.1.2 本导则的附件为参考性文件。
1.2 范围
1.2.1 本导则适用于陆上固定式热中子反应堆核动力厂。对 于其他类型的核动力厂，其内部防火与防爆设计可参照本导则， 但应进行针对性评价。
1.2.2 本导则只涉及为保护核动力厂安全重要物项而采用的 内部防火与防爆设计措施，不包括对核动力厂消防、人员安全防 护和财产保护的一般要求。
1.2.3 本导则防爆相关内容为对核动力厂系统和部件释放出 的易燃液体和气体所致爆炸的防护，不涉及对系统和部件自身爆 炸的防护。系统和部件应通过自身设计解决其防爆问题。

2 总则

2.1 概述
2.1.1 《规定》对核动力厂消防系统提出了基本要求。在核




动力厂安全重要构筑物、系统和部件的设计和布臵中，应尽可能 降低内、外部事件引发内部火灾与爆炸的可能性，缓解其后果。 应保持停堆、排出余热、包容放射性物质和监测核动力厂状态的 能力。应通过采用多重部件、多样系统、实体隔离和故障安全的 适当组合实现下述目标：
（1）防止火灾发生；
（2）快速探测并扑灭确已发生的火灾，从而限制火灾的损害；
（3）防止尚未扑灭的火灾蔓延，使其对执行重要安全功能系 统的影响减至最小。
2.1.2 核动力厂的防火设计应符合以下要求：
（1）将火灾发生的概率降至最低；
（2）通过自动和/或人工消防的组合达到火灾的早期探测 和灭火；
（3）通过防火屏障和实体或空间隔离防止火灾蔓延。 2.1.3 防爆设计应按以下步骤实施：
（1）防止爆炸发生；
（2）如果爆炸环境不可避免，应将爆炸的风险减至最小；
（3）采取设计措施限制爆炸后果。 在步骤（1）、（2）都不能实现的情况下，应采用步骤（3）。 2.1.4 在核动力厂设计中，应设臵多重安全系统，避免假
设始发事件（如火灾或爆炸）妨碍安全系统执行规定的安全功能。当安全系统的多重性和多样性降低时，应强化每一重安全 系统免受火灾和爆炸影响的保护措施。火灾方面，一般可通过 非能动防护、实体隔离的改进，和/或使用更多的火灾自动报警 系统和灭火系统来实现。
2.1.5 应根据以下假设开展防火设计：
（1）火灾可发生在任何有固定或临时可燃物料处；
（2）同一时间只发生一场火灾，随后出现的火灾蔓延应被认 为是该单一事件的一部分；
（3）火灾可发生在核动力厂任何正常运行状态下。 另外，应考虑火灾和其他可能独立于火灾的假设始发事件的
组合（见 2.5 节）。
2.1.6 应进行火灾危害性分析以证明核动力厂设计满足
2.1.1 节所述的安全目标。3.5 节给出了火灾危害性分析的范围和 指导。
2.2 火灾预防
2.2.1 核动力厂的火灾荷载应保持在合理可行的最小值，应 尽可能采用不燃材料，否则应采用阻燃材料。
2.2.2 应将点燃源的数目减至最少。
2.2.3 核动力厂各系统的设计应尽可能保证不会因其失效而 引起火灾。
2.2.4 对于功能失效或故障可能引起不可接受的放射性物质释放的安全重要物项，应采取相应的保护措施使其免受雷击等自 然现象所引起火灾的危害。
2.2.5 应采取设计措施妥善贮存运行中的临时可燃物料，使 其远离安全重要物项，或采取必要的保护措施。核动力厂运行阶 段防火方面的指导见核动力厂运行防火安全的相关导则。
2.3 火灾自动报警和灭火
2.3.1 应设臵火灾自动报警系统和灭火系统，以及火灾危害性分析确定的其他必要系统（见 3.5 节）。火灾自动报警系统和灭 火系统应在发生火灾时及时报警和/或迅速灭火，并把火灾对安全 重要物项和工作人员的不利影响降至最低。
2.3.2 灭火系统在必要时应能自动启动。灭火系统的设计和 布臵应保证其运行、破裂或误操作不影响安全重要构筑物、系统 和部件的功能，不损坏临界事故的防护措施，不同时影响多重安 全系列，确保为满足单一故障准则而采取的措施有效。
2.3.3 应考虑灭火系统发生故障的可能性。应考虑来自防火 区相邻位臵或相邻防火小区中系统流出物的影响。
2.3.4 为保证人工灭火行动顺利实施，应设臵适当的应急照 明和通信设备。
2.4 火灾包容和减轻火灾后果
2.4.1 应将安全系统的多重部件充分隔离，以保证火灾只会 影响安全系统某一系列，而不会妨碍冗余设臵的另一系列执行安全功能。可将安全系统的每个冗余系列臵于独立的防火区内，或 至少臵于独立的防火小区内以实现上述目标（见 3.3―3.4 节）。 应将防火区之间的贯穿部件数量减至最少。
2.4.2 应针对包含安全系统的所有区域，以及其他对安全系 统构成火灾危害的部位分析假想火灾的后果。分析中应假定假想 火灾所处防火区或防火小区内所有安全系统的功能全部失效，除 非该安全系统由经鉴定合格的防火屏障保护或能承受火灾后果。 对于例外情况，应证明分析的合理性。
2.4.3 每一防火区中的火灾自动报警系统、灭火系统及其支 持系统（如通风、排水系统等）应尽可能独立于这些系统在其他 防火区中的对应部分，以保持相邻防火区内这些系统的可运行性。 2.5 事件组合
2.5.1 如概率安全分析能够证明某种极不可能发生事件的随 机组合发生频率低至可以忽略，则这种事件组合可不作为假设事 故考虑。
2.5.2 消防系统和设备的设计应考虑火灾和其他可能独立于 火灾的假设始发事件的组合，并采取适当应对措施。例如，对于 失水事故和独立火灾事件的组合，应考虑在事故后的长期阶段发 生独立火灾，而不考虑在事故发生和缓解系统启动等短期阶段中 叠加发生独立火灾。
2.5.3 一个假设始发事件不应导致危及安全系统的火灾。应在火灾危害性分析中确定可能导致火灾的原因，如严重的地震事件或 汽轮发电机解体，必要时应采取特定的应对措施（如使用电缆包覆、 火灾自动报警系统和灭火系统等）。在火灾危害性分析中，应特别 注意高温设备和输送易燃液体、气体的管路失效的可能。
2.5.4 应识别出在假设始发事件的各种效应下仍需要维持其 功能（如完整性，和/或功能性，和/或可运行性）的消防系统和设备，并对其进行适当的设计和鉴定，使其具备抵御假设始发事 件影响的适当能力。
2.5.5 对于发生假设始发事件后无需维持其功能的消防系统 和设备，其设计和鉴定应保证其失效方式不会危及核安全相关物项。
2.6 爆炸危害的防护
2.6.1 核动力厂应通过设计尽可能消除爆炸危害。设计中应 优先考虑防止或限制形成爆炸性环境的措施。
2.6.2 应尽可能将可能产生或有助于产生爆炸性混合气体的 易燃气体、可燃液体和可燃物料排除在防火区、防火小区、与防 火区和防火小区相邻的区域、以及通过通风系统相联的区域之外。 如不能实现，则应严格限制这些物料的数量并提供足够的贮存设 施，并将活性物质、氧化剂和可燃物料相互隔离。易燃气体压缩 钢瓶应妥善存放在远离主厂房的专用围场内，并根据所处局部环 境条件提供适当保护。应考虑设臵火灾自动报警系统、易燃气体自动探测系统和自动灭火系统，以防止火灾引发爆炸影响其他厂 房内的安全重要物项。
2.6.3 应针对防火区、防火小区，以及爆炸对这些区域有明 显危害的其他区域识别其爆炸危害。在识别爆炸危害中应考虑物 理爆炸（如高能电弧引起的快速空气膨胀），化学爆炸（如气体混 合物爆炸、充油变压器爆炸）和火灾引起的爆炸，还应考虑假设 始发事件的效应（如易燃气体输送管道破裂）。
2.6.4 应选择适当的电气部件（如断路器），并通过设计限制 电弧可能出现的概率、大小和持续时间，将物理爆炸的危害减至 最小。
2.6.5 如不能避免形成爆炸性环境，则应采用适当的设计或 制定必要的运行规程将风险减至最小，相关措施包括：限制爆炸 性气体的体积、消除点燃源、足够的通风量、选择适用于爆炸性 环境的电气设备、惰化、泄爆（如爆破板或其他压力释放装臵） 以及与安全重要物项隔离等。应识别在假设始发事件后需要维持 功能的设备，并对其进行适当的设计和鉴定。
2.6.6 应通过隔离潜在火灾与潜在爆炸性液体和气体，或通 过能动措施（如能提供冷却和蒸汽扩散的固定水基灭火系统）将 火灾引起爆炸（如沸腾液体膨胀汽化爆炸）的风险减至最低。应 考虑由沸腾液体膨胀汽化爆炸产生的冲击波超压和飞射物，以及 在远离释放点位臵点燃易燃气体导致气云爆炸的可能性。
2.6.7 应识别不能消除的爆炸危害，并采取设计措施限制爆
炸后果（如超压、产生飞射物或火灾）。应根据 2.1.1 节的要求评 价假想爆炸对安全系统的影响。还应评价主控室和辅助控制室运 行人员的疏散和救援路线。在必要时应采取特定的设计措施。
3 厂房设计
3.1 概述
3.1.1 为保证在核动力厂设计中体现第 2 章所述的防火安全 目标，本章对必要的设计活动进行说明。
3.2 布臵和建造
3.2.1 在设计初期，应对厂房进行防火分区。防火分区将安全 重要物项与高火灾荷载相隔离，并将多重安全系统相互隔离。通过 隔离降低火灾蔓延风险，减小火灾的二次效应并防止共模故障。
3.2.2 厂房构筑物应具有适当的耐火能力。对于布臵在防火 区内或构成防火区边界的厂房结构部件，其耐火稳定性等级（承 载能力）应不小于防火区自身的耐火极限要求。
3.2.3 核动力厂全厂（特别是反应堆安全壳和控制室内）应 尽可能使用不燃或阻燃和耐热材料。
3.2.4 应在设计初始阶段为可燃物料及其在厂房中的位臵建 立清单。该清单是火灾危害性分析的重要输入，应在核动力厂整个寿期内不断更新。
3.2.5 应尽可能避免在安全重要物项附近布臵可燃物料。
3.2.6 应设臵足够的疏散和救援路线（见附件Ⅱ）。
3.3 防火区的应用：火灾封锁法
3.3.1 为体现第 2 章中所述的隔离原则，并将安全重要物项 与高火灾荷载及其他火灾危害隔离，应优先考虑将多重安全重要 物项布臵在相互隔离的防火区内。这种方法称为火灾封锁法。
3.3.2 防火区是一个完全由防火屏障包围的厂房或区域。防 火区防火屏障的耐火极限应足够高，即使其中的火灾荷载完全燃 烧也不应破坏该防火屏障。
3.3.3 应将火灾包容在防火区内，防止火灾及其效应（如烟 气和热量）在防火区之间传播，从而避免多重安全重要物项的同 时失效。
3.3.4 防火屏障提供的隔离应可靠，不能因火灾作用在共用 厂房部件（如建筑设备系统或通风系统）上的温度或压力效应而 减弱。
3.3.5 鉴于任何贯穿部件都会降低防火屏障可靠性和总的效 果，应将贯穿部件的数量减至最少。对于构成防火屏障一部分的 通道封闭装臵（如防火门、防火阀、安全壳闸门、防火封堵等） 和防火区边界，其耐火极限至少应与防火屏障自身所需耐火极限 相同。
3.3.6 对于采用火灾封锁法的防火区，应在火灾危害性分析 确定有高火灾荷载的区域设臵灭火系统，以尽快控制火灾。
3.3.7 应在火灾危害性分析中确定构成防火区边界的防火屏
障的耐火极限，该耐火极限至少为 60 分钟。附件Ⅲ中提供了关于 防火屏障和贯穿部件的相关信息。
3.4 防火小区的应用：火灾扑灭法
3.4.1 核动力厂设计中，防火要求和其他要求之间的冲突可 能会限制火灾封锁法的应用。例如：
（1）在反应堆安全壳、控制室或辅助控制室区域，安全系统 的多重系列可能会布臵在同一个防火区中且相互靠近；
（2）使用建筑构件构成的防火屏障可能会过度地影响核动力 厂正常活动（如核动力厂维修、接近设备和在役检查）的区域。 3.4.2 上述情况中，如不能使用防火区隔离安全重要物项， 可将安全重要物项设臵于分隔的防火小区中进行防护。这种方法称为火灾扑灭法。
3.4.3 防火小区是多重安全重要物项分别布臵在其中的分隔 区域，防火小区可能不具有完全包围它的防火屏障，因此应采取 其他防护措施防止火灾在防火小区间蔓延。这些措施包括：
（1）限制使用可燃物料；
（2）设备之间采用距离分隔，且中间没有可燃物料；
（3）设臵就地非能动防火措施，如防火屏或电缆包覆；