Containment Isolation Device for Fluid System after Loss of Coolant Accident
失水事故后流体系统的安全壳隔离装置
1 Subject Content and Applicable Scope
This standard specifies the basic requirements for the installation, design, test, operation and maintenance of containment isolation and isolation devices that are arranged in the whole containment fluid system after loss of coolant accident.
This standard is applicable to the fluid system containment isolation after the pressurized water reactor nuclear power plant suffers from loss of coolant accident.
2 Normative References
HAF 0307 Nuclear Power Plant Maintenance
3 Terminologies
3.1
Accident
Single accident including loss of coolant accident in containment, which is hypothetical but not impossible and will cause failure of one or more fission product barriers.
3.2
Accident isolation
Closing the isolation device arranged on the fluid pipe running through the containment to prevent the accident or mitigate the consequences caused thereby.
3.3
Accident isolation signal
Signal that automatically triggers the isolation device to implement the accident isolation function.
3.4
Closed system
Closed circuit loop line inside or outside of and running through the containment. During normal operation or in the event of loss of coolant accident, the closed system in the containment is neither directly connected to the primary coolant pipe nor to the containment atmosphere.
3.5
Containment atmosphere
Gas in the free space contained by the containment.
3.6
Containment isolation signal
Signal used to automatically trigger the containment isolation device to perform its isolation function. This signal is sent by the protection system or by the operator in the main control room.
3.7
Isolation barrier(s)
Mechanical device that prevents fluids in the containment fluid system from flowing out of the containment, such as valve, closed system or blind flange.
3.8
Isolation barrier protection
Protective measures against loss of function of the isolation barrier in the event of an external event such as missile, pipe slamming, jetting force or natural phenomenon.
3.9
Isolation valve seal system
System that protect the isolation valve from leaking.
3.10
Missile protection
Protecting structures, systems or components from being influenced by missile, including jetting force and pipe slamming, through physical barriers, limiting device or design and layout.
3.11
Motive power failure
Loss of driving source.
3.12
Protection system
System that generates signal automatically triggering the containment isolation device to operate, including all electrical and mechanical devices as well as circuits from the sensitive elements to the valve operator input end.
3.13
Administrative controls
Controlling by virtue of rules, directives, regulations, policies, implementation methods, or assignment of authority and responsibility.
3.14
Automatic isolation valve
Valve or simple check valve that automatically closes without being operated by the operator after receiving an isolation signal from the protection system.
3.15
Containment isolation
Process of closing the containment isolation valve arranged in the whole containment fluid system to enclose the radioactive product in the containment.
3.16
Phased isolation
Sending containment isolation signal by using different measurement parameter values or different combinations thereof according to the ability required for fluid system running through the containment mitigates the consequences of an accident or maintains a plant's safe state so as to cause the fluid system running through the containment to be grouped and successively isolated.
3.17
Power operator
Device that operates a valve using gas, electricity, hydraulic pressure or spring force.
3.18
Simple check valve
Valve that is closed only by the reverse flow of fluid.
3.19
Reactor coolant pressure boundary
Pressure components including reactor pressure vessels, pressure stabilizer, steam generator primary side, control rod drive mechanism pressure shell, reactor core measuring instrument tube and reactor coolant pipeline, pump body and valve, they are:
a. constituent part of the reactor coolant system;
b. components from the reactor coolant system they are connected to any or all of the following valves (inclusive): the outermost containment isolation valve in the pipeline running through the containment; the second valve of the two normally closed valves during normal operation of the reactor, the pipeline where such valve is located does not run through the containment; the safety valve and pressure relief valve of the reactor coolant system.
3.20
Sealed closed isolation valve
Valve that is kept close under administrative control in one of the following ways:
a. Keep the valve in closed position with a mechanical device or lock;
b. Lock the manual manipulator of valve that has been closed by sealing or with a lock;
c. Lock the switch or motive power by sealing or with a lock to prevent it from supplying power to the valve.
3.21
Valve closure time
Time required from the valve drive device obtaining driving power to the full closure of the valve, excluding the lag time of instruments and control.
3.22
Redundant system
Two or more systems being capable of independently performing the same function during normal operation or accident, which has nothing to do with the operating state or whether another system fails.
3.23
Valve position
Open or closed state of valve.
3.24
Full-stroke time
Time interval from the moment the actuating signal is sent out to the end of the valve action process.
3.25
Active valves
Valve that requires a change in its position when performing its function.
3.26
Passive valves
Valve that does not require a change in its position when performing its function.
3.27
Category A
Valve with its valve seat leakage amount not allowed to exceed the specified maximum value when performing its function in the closed position.
3.28
Category B
Valve with its valve seat leakage amount not critical when performing its function in the closed position.
3.29
Category C
Valve that operates automatically in response to changes in certain characteristic parameters of the system, such as pressure (pressure relief valve) or flow direction (check valve).
3.30
Category D
Valve that can only be operated once under the action of energy, such as a burst disk or a blast-activated valve.
3.31
Exercising
Verification test based on direct or indirect visual or other methods that clearly indicate that the valve operating components are performing well.
3.32
Inservice life
Time period from installation and acceptance to decommissioning.
3.33
Inservice test
Special test method of determining the valve’s capability in implementing its function based on the data obtained by observation or measurement.
3.34
Maintenance
Routine maintenance of valves to correct or prevent abnormal and poor operating conditions.
4 Containment Isolation Design Criteria
4.1 Fluid system running through the containment
Containment isolation barriers must be arranged on each pipeline running through the containment so that the containment is able to be automatically and reliably isolated in case of loss of coolant accident or other accidents in the containment that require the containment isolate so as to ensure the sealing and leakage-proof performance of the containment.
The containment isolation barriers may be isolation valves, closed systems or a blind flanges.
Containment isolation facilities shall be designed by following the principle of multiplicity and diversity. Typically, two isolation valves are placed in series on each fluid pipe running through the containment, each isolation valve must be able to limit the radioactive substance leakage to acceptable limits and must be able to operate reliably and independently. Containment isolation must be able to be implemented in case of a single failure.
For the design of fluid system running through the containment, it must be taken into account that the tests on performability and leak rate of isolation valve and relevant equipment are able to be regularly conducted and the leakage is within acceptable limits.
For connection pipeline running through the containment between containment isolation facilities, leak detection must be able to be conducted and overpressure protection arranged.
4.2 Containment isolation valve arrangement criteria
4.2.1 For pipelines that run through the containment and are part of the reactor coolant pressure boundary, unless otherwise specified, containment isolation valves must be arranged in one of the following ways (see Figure 1):
a. A sealed closed isolation valve is arranged both inside and outside the containment respectively;
b. An automatic isolation valve is arranged inside the containment and a sealed closed isolation valve outside it;
c. A sealed closed isolation valve is arranged inside the containment and an automatic isolation valve outside it;
d. An automatic isolation valve is arranged both inside and outside the containment respectively.
A simple check valve cannot be used as an automatic isolation valve outside the containment.
In normal operation, if there is pipeline for the fluid flows into the containment but no pipeline for it flows out of the containment, the simple check valve may be used as an automatic isolation valve inside the containment.
The isolation valve outside the containment must be as close as possible to the containment. The automatic isolation valve must be designed such that it is in a state in which it is required to implement its function when the operating power is lost and a loss of coolant accident occurs.
In order to ensure safety, other appropriate requirements shall be specified as necessary to minimize the chances or consequences of rupture of these pipelines or other pipelines connecting them. Population density, utilization characteristics and natural characteristics around the site shall be taken into account when determining whether requirements are appropriate such as higher quality design, manufacturing and test, supplement measures for in-service inspections, prevention of more serious natural disasters, and additional isolation valves and closures.
4.2.2 For pipelines that run through the containment and vent to the containment atmosphere, unless otherwise specified, the containment isolation valve must be arranged in one of the following ways (see Figure 1):
a. A sealed closed isolation valve is arranged both inside and outside the containment respectively;
b. An automatic isolation valve is arranged inside the containment and a sealed closed isolation valve outside it;
c. A sealed closed isolation valve is arranged inside the containment and an automatic isolation valve outside it;
d. An automatic isolation valve is arranged both inside and outside the containment respectively.
A simple check valve cannot be used as an automatic isolation valve outside the containment.
In normal operation, if there is pipeline for the fluid flows into the containment but no pipeline for it flows out of the containment, the simple check valve may be used as an automatic isolation valve inside the containment.
The isolation valve outside the containment must be as close as possible to the containment. The automatic isolation valve must be designed such that it is in a state in which it is required to implement its function when the operating power is lost and a loss of coolant accident occurs.
4.2.3 For a closed system that runs through the containment and is neither part of the reactor coolant pressure boundary nor directly vent to the containment atmosphere, each pipeline running through the containment must be equipped with at least one containment isolation valve which may be automatic isolation valve, sealed closed isolation valve or remote manual isolation valve. The isolation valve must be arranged outside and as close as possible to the containment. A simple check valve shall be used as an automatic isolation valve (Figure 2).
4.2.4 For small instrumented lines at dead ends (e.g., lines with an inner diameter <26mm), only one manual operated isolation valve is required outside the containment. Instrument pipelines that are enclosed both inside and outside the containment, such as containment pressure measuring lines, may not be equipped with isolation valves provided that they are designed to withstand the maximum pressure of the containment structural integrity test and the design temperature of the containment and are provided with measures against missiles and dynamic effects.
4.2.5 The isolation function of the following systems may be fulfilled by replacing the automatic isolation valve with the remote manual isolation valve.
a. Engineered safety features;
b. Systems that are not required to be performed in the event of a loss of coolant accident but can be used to fulfill the same functions as those of engineered safety features, such as the fluid system necessary for the operation of the main coolant pump.
If the failure that possibly occurs in the fluid pipelines inside and/or outside the containment can be detected and the pipelines can be isolated through remote manual operation, a remote manual isolation valve may be adopted.
4.2.6 For the systems required by the engineered safety features or those features for test, as long as it can be confirmed that such systems can adapt to a single active failure with only one valve and the reliability of the fluid system functions are enhanced by using one valve rather than two series-connected valves, or the closed system outside the containment can meet the requirements of 4.3.2, it is allowed to arrange only one isolation valve outside the containment.
A closed system with only one isolation valve must be verified that the its integrity is maintained at pressures greater than or equal to the containment design pressure, and the system must be subjected to the leakage test in accordance with those specified in 6.2 of this standard.
The valve and the connection pipeline between the valve and the containment must be contained in a leak-proof seal housing or a controlled leakage chamber to avoid the leakage to the environment (Figure 3), and such seal housing or chamber may not be considered if a conservative design which can eliminate the damage to the integrity of the pipeline is adopted for the valve and the connection pipeline, in which case, it must be possible to detect and eliminate the leakage at the sealed part of the valve stem and/or valve body.
4.2.7 If two series-connected isolation valves are required for the system necessary for engineered safety features or the testing of those features, and one of the valves cannot be mounted inside the containment, both isolation valves may be mounted outside the containment and as close as possible to the containment. The valve near the containment and the connection pipeline between it and the containment must be contained in the leak-proof seal housing or controlled leakage chamber to avoid the leakage to the environment (Figure 4), and such seal housing or chamber may not be considered if a conservative design which can eliminate the damage to the integrity of the pipeline is adopted for the valve and the connection pipeline, in which case, it must be possible to detect and eliminate the leakage at the sealed part of the valve stem and/or valve body.
4.2.8 The pressure relief valve may be used as an isolation valve for the pressure relief direction or the return direction as long as it meets the requirements of this standard.
4.2.9 The process valves may be used as containment isolation valves as long as they meet the requirements of this standard.
1 Subject Content and Applicable Scope
2 Normative References
3 Terminologies
4 Containment Isolation Design Criteria
5 Design Requirements
6 Test
7 Maintenance
8 Materials
Appendix A (Informative) Inservice Test for Valves of Nuclear Power Plant
Appendix B (Informative) Typical Setup Figures of Pressurized Water Reactor (PWR) Containment Isolation Devices
Appendix C (Informative) Typical Isolation Valve Maintenance Program
失水事故后流体系统的安全壳隔离装置
EJ/T 331—92
代替EJ 331—88
1主题内容与适用范围
本标准规定了失水事故后贯穿安全壳流体系统的安全壳隔离及隔离装置的设置、设计、试验、操作和维修的基本要求。
本标准适用于压水堆核电厂失水事故后流体系统的安全壳隔离。
2引用标准
HAF 0307核电厂维修
3术语
3.1事故accident
包括安全壳内的失水事故在内的一个单一事故，这一事故是假想的但不是不可能的，该事故将引起一道或一道以上裂变产物屏障失效。
3.2 事故隔离 accident isolation
关闭贯穿安全壳的流体管道上设置的隔离装置，以阻止或减轻事故后果。
3.3事故隔离信号accident isolation signal
自动触发隔离装置实施事故隔离功能的信号。
3.4封闭环路closed system
贯穿安全壳，在安全壳内或在安全壳外是一个闭环管路。在正常运行期间或失水事故时，安全壳内的封闭环路既不与一次冷却剂管道直接连通，也不与安全壳大气相通。
3.5安全壳大气containment atmosphere
安全壳包容的自由空间内的气体。
3.6安全壳隔离信号containment isolation signal
用来自动触发安全壳隔离装置实施其隔离功能的信号。该信号由保护系统发出或由操纵员在主控室发出。
3.7隔离屏障isolation barrier(s)
阻止贯穿安全壳流体系统中的流体流出安全壳的机械装置，如阀门、封闭环路或法兰盲板。
3.8隔离屏障防护isolation barrier protection
在发生外部事件(如飞射物、管道甩击、喷射力或自然现象)时，防止隔离屏障丧失功能的保护措施。
3.9隔离阀密封系统isolation valve seal system
控制隔离阀泄漏的系统。
3.10飞射物防护missile protection
用实体屏障、限止器或设计布置防止飞射物(包括喷射力、管道甩击)对构筑物、系统或部件的影响。
3.11动力源故障motive power filure
丧失驱动源。
3.12 保护系统protection system
产生自动触发安全壳隔离装置运行信号的系统，包括所有的电气、机械器件和从敏感元件到阀门操作器输入端的线路。
3.13行政控制 administrative controls
通过规则、指令、规程、政策、实施方法或权限和责任的分配进行控制。
3.14 自动隔离阀automatic isolation valve
收到保护系统发出的隔离信号后不需由操作员操作而自动关闭的阀门或简单止回阀。
3.15安全壳隔离containment isolation
关闭贯穿安全壳流体系统中的安全壳隔离阀，将放射性产物封闭在安全壳内。
3.16分阶段隔离phased isolation
根据贯穿安全壳流体系统减轻事故后果或维持电厂安全状态所需的能力，用不同测量参数值或它们的不同组合发出安全壳隔离信号，使贯穿安全壳的流体系统分组依次隔离。
3.17动力驱动装置power operator
利用气、电、液压或弹簧力来操作阀门的装置。
3.18简单止回阀simple check valve
只靠流体反向流动关闭的阀门。
3.19反应堆冷却剂压力边界reacor coolant pressure boundary
包括反应堆压力容器、稳压器、蒸汽发生器一次侧、控制棒驱动机构承压壳、堆芯测量仪表管和反应堆冷却剂管道、泵体和阀门等承压部件，它们是：
a. 反应堆冷却剂系统的组成部分；
b. 与反应堆冷却剂系统连接直到并包括下列任何或全部阀门：贯穿安全壳的管道中最外一个安全壳隔离阀；反应堆正常运行期间通常关闭的两个阀的第二个阀，该阀所在管道不贯穿安全壳；反应堆冷却剂系统的安全阀和卸压阀。
3.20锁关隔离阀sealed clsed isolation valve
用下列方式之一由行政控制保持在关闭状态的阀门：
a. 用机械装置或锁将阀门保持在关闭位置；
b. 用封印或锁锁住已关闭阀的手操作器；
c. 用封印或锁锁住电闸或动力源，防止向阀门供给动力。
3.21阀门关闭时间valve closure time
从阀门驱动装置得到驱动动力到阀门完全关闭所需的时间，这段时间不包括仪表和控制滞后时间。
3.22多重系统redudant system
两个或多个系统在正常运行或事故时能独立完成同样功能而且与运行状态或另一个系统是否失效无关。
3.23 阀位valve position
指阀门开或关的状态。
3.24全行程时间full-stroke time
从发出动作信号到阀门动作过程结束的时间间隔。
3.25 能动阀门 active valves
执行其功能时要求改变阀位的阀门。
3.26非能动阀门passive valves
执行其功能时不要求改变阀位的阀门。
3.27 A类阀门 category A
在关闭位置执行其功能时，阀座的泄漏量不允许超过规定的最大值的阀门。
3.28 B类阀门category B
在关闭位置执行其功能时，阀座的泄漏量并不重要的阀门。
3.29 C类阀门category C
能响应系统内某些特性参数，如压力(卸压阀)或流向(止回阀)的变化而自动操作的阀门。
3.30 D类阀门 category D
在能源的作用下仅能操作一次的阀门，如炸破盘或爆破致动的阀门。
3.31 动作操演 exercising
根据直接的或间接的目视或其它能明确指示阀门运行部件动作良好的方法进行的一种验证试验。
3.32在役寿期inservice life
从安装和验收直到退役的时间周期。
3.33 在役试验 inservice test
通过观察或测量获得资料以确定阀门执行其功能能力的一种特殊试验方法。
3.34维护maintenance
为矫正或防止异常和不良工况而进行的阀门常规保养。
4安全壳隔离设计准则
4.1贯穿安全壳的流体系统
必须在贯穿安全壳的每根管道上设置安全壳隔离屏障，在安全壳内发生失水事故或其它要求安全壳隔离的事故时，必须能自动而又可靠地隔离，以确保安全壳的密封防漏性能。
安全壳隔离屏障可以是隔离阀、封闭环路或法兰盲板。
安全壳隔离设施应采用多重性和多样性设计原则。通常，在贯穿安全壳的每根流体管道上串联设置两个隔离阀。每个隔离阀门必须足以限制放射性物质泄漏在可接受的限值内，并必须能可靠而独立地动作。假定一个单一故障发生时必须能实施安全壳隔离。
设计贯穿安全壳的流体系统必须考虑要能定期进行隔离阀和有关设备的可运行性和泄漏率试验，并确认阀门的泄漏是在允许的范围内。
安全壳隔离设施之间贯穿安全壳部分的连接管道必须可进行泄漏检测，并要有超压保护。
4.2安全壳隔离阀设置准则
4.2.1 贯穿安全壳且属于反应堆冷却剂压力边界的一部分的管道，除另有条文规定外，必须按照下列方式之一设置安全壳隔离阀(如图1)：
a. 安全壳内一只锁关隔离阀，安全壳外一只锁关隔离阀；
b. 安全壳内一只自动隔离阀，安全壳外一只锁关隔离阀；
c. 安全壳内一只锁关隔离阀，安全壳外一只自动隔离阀；
d. 安全壳内一只自动隔离阀，安全壳外一只自动隔离阀。
简单止回阀不能作为安全壳外的自动隔离阀。
正常运行时，流体只有流入而没有流出(指安全壳)的管道，简单止回阀可以作为安全壳内的自动隔离阀。
安全壳外的隔离阀必须尽可能靠近安全壳。自动隔离阀必须设计成在失去操作动力时处于失水事故时要求实施其功能的状态。
为了确保安全，必要时应规定其它一些适当要求.使这些管线或与其相连管线破裂的几率或后果减到最小。在确定这些诸如更高质量的设计、制造及试验，在役检查的补充措施、防止更加严重的自然灾害以及附加的隔离阀和封闭等要求是否合适时，应考虑到人口密度、利用特点以及厂址周围的自然特性。
4.2.2贯穿安全壳且与安全壳大气相通的管道，除另有条文规定外.必须按照下列方式之一设置安全壳隔离阀(如图1)：
a. 安全壳内一只锁关隔离阀，安全壳外一只锁关隔离阀；
b. 安全壳内一只自动隔离阀，安全壳外一只锁关隔离阀；
c. 安全壳内一只锁关隔离阀，安全壳外一只自动隔离阀；
d. 安全壳内一只自动隔离阀，安全壳外一只自动隔离阀。
简单止回阀不能作为安全壳外的自动隔离阀。
正常运行时，流体只有流入(安全壳)而无流出的管道，简单止回阀可以作为安全壳内的自动隔离阀。
安全壳外的隔离阀必须尽可能靠近安全壳，自动隔离阀必须设计成在失去操作动力时处于失水事故时要求实施其功能的状态。
4.2.3贯穿安全壳且既不是反应堆冷却剂压力边界的一部分，不直接与安全壳大气相通的封闭环路，每根贯穿安全壳的管道必须至少有一个安全壳隔离阀，该阀可以是自动隔离阀、锁关隔离阀或远距离手动隔离阀。隔离阀必须设置在安全壳外，且尽可能靠近安全壳。简单止回阀不能作为自动隔离阀(如图2)。
4.2.4 对于盲端的小仪表管线(例如内径<26mm的管线)，只要求在安全壳外则设置一个手操作隔离阀。在安全壳内和安全壳外都封闭的仪表管道，如安全壳压力测量管线，只要设计成能承受安全壳结构完整性试验的最大压力、能承受安全壳的设计温度并具有防飞射物和动态效应的措施，可以不设隔离阀。
4.2.5下列系统的隔离功能可由远距离手动隔离阀代替自动隔离阀来完成：
a. 专设安全设施；
b. 失水事故时不要求执行功能，但需要时能完成专设安全设施同样功能的那些系统，如主冷却剂泵运行所需要的流体系统。
当安全壳内和(或)安全壳外的流体管道可能发生的故障能被探测到并且能够用远距离手动保持隔离这些管道，那么可以用远距离手动隔离阀。
4.2.6专设安全设施或试验专设安全设施所要求的系统，只要能证实只需一个阀门就能适应单一能动故障，并且流体系统功能的可靠性采用一个阀门比二个串联阀门得到增强，或者在安全壳外的封闭环路满足4.3.2要求，则允许只在安全壳外设一只隔离阀。
只设一只隔离阀的封闭式环路除了能证实在压力大于或等于安全壳设计压力时能保持系统的完整性外必须按照本标准6.2的有关要求进行泄漏试验。
该阀及其与安全壳之间的连接管道必须包容在一个防泄漏密封壳或可控泄漏间内以避免向环境泄漏(如图3)，或者设计阀门和连接管道时采取保守的设计，能消除管道完整性的破坏，则可以不考虑防泄漏密封壳或可控泄漏间，在此情况下必须要能检测从阀杆和(或)阀体密封处的泄漏并消除泄漏。
4.2.7如果专设安全设施或试验专设安全设施所要求的系统需要两个串联隔离阀，而其中之一又不可能设置在安全壳内时，两个隔离阀均可设置在安全壳外，并尽可能靠近安全壳。靠近安全壳的阀及其与安全壳之间的连接管道必须包容在防泄漏密封壳或可控泄漏间内以防止向环境泄漏(如图4)，或者该阀门和管道采取保守的设计，能消除管道完整性的破坏，则可以不考虑防泄漏密封壳或可控泄漏间，在此情况下必须要能检测从阀杆和(或)阀体密封处的泄漏，并消除泄漏。
4.2.8卸压阀只要满足本标准的要求可以作为卸压方向或回流方向的隔离阀。
4.2.9工艺阀门只要满足本标准的要求，则可以作为安全壳隔离阀。
4.3封闭环路准则
4.3.1安全壳内的封闭环路作为安全壳两个隔离装置之一，须满足下列全部要求：
a. 既不与一次冷却剂管道连接，也不与安全壳大气连通；
b. 要有防飞射物、管道甩动和喷射力冲击的保护措施；
c. 满足安全二级设计要求；
d. 能承受安全壳结构完整性试验压力相等的外压；
e. 能承受安全壳设计温度；
f. 能承受失水事故所造成的瞬态和事故后的环境条件；
g. 满足抗震I类设计要求；
h. 有隔离后由于事故引起安全壳内温度升高使系统内流体的热膨胀引起超压的超压保护；
i. 要能进行泄漏试验并满足安全壳整体泄漏试验的有关要求。
如果上述要求不能全部满足，则设置该封闭环路的安全壳隔离设施必须满足本标准4.2的要求。
4.3.2安全壳外的封闭环路作为专设安全设施或专设安全设施有关系统的两个隔离装置之一时，该封闭环路必须满足下列全部要求：
a. 与外部大气不连通；
b. 满足安全二级设计要求；
c. 能承受安全壳设计温度和压力；
d. 能承受失水事故瞬态和环境条件；
e. 满足抗震1类设计要求；
f. 具有防隔离后系统内流体热膨胀引起超压的超压保护；
g. 如果当高能管道破裂需要安全壳隔离时，应具有防高能流体管道破裂对封闭环路影响的保护措施；
h. 具有防飞射物的保护措施；
i. 能进行泄漏试验。
4.4隔离阀设计准则
所有安全壳隔离阀必须能完全关死以满足安全壳泄漏试验的有关要求。
安全壳隔离阀可以是自动隔离阀、锁关隔离阀或远距离手动阀。隔离阀的关闭时间要求(包括检测、操作时间)必须确保阀门预期的安全功能。
4.5连接管道准则
4.5.1 安全壳与安全壳外隔离阀之间的连接管道和安全壳外的两个隔离阀之间的连接管道必须：
a. 至少满足安全二级设计要求；
b. 能承受安全壳设计温度；
c. 能承受安全壳结构完整性试验压力相等的内压；
d. 能承受失水事故瞬态和事故后的环境条件；
e. 满足抗震I类设计要求；
f. 当高能管道破裂需要安全壳隔离时，应具有防高能流体管道破裂对连接管道影响的保护措施；
g. 具有隔离后由于流道内流体热膨胀引起超压的超压保护；
h. 具有防飞射物的保护措施。
4.5.2安全壳与安全壳内隔离阀之间的连接管道必须：
a. 满足安全二级设计要求；
b. 能承受安全壳设计温度；
c. 能承受安全壳结构完整性试验压力相同的外压；
d. 能承受失水事故瞬态和事故后的环境条件；
e. 满足抗震1类设计要求；
f. 如果需要，还应具有防失水事故引起的飞射物、管道甩动和喷射力的保护措施；
g. 具有隔离后由于流道内流体热膨胀引起超压的超压保护。
4.5.3安全壳隔离阀之间的连接管道必须要能进行泄漏检测。
4.6安全壳隔离触发准则
4.6.1对于除专设安全设施和完成专设安全设施同样功能的系统以外的其它系统，触发其安全壳隔离的隔离信号必须优先于其它触发信号。
4.6.2设计者必须确定是否需要分阶段隔离，并以文件形式说明确定的依据。分阶段隔离可以利用潜在有利的流体系统去减轻事故后果和增强电厂的安全。
4.6.3如果不采用分阶段隔离，安全壳隔离信号必须由多种参数发出，如堆芯应急冷却的启动、安全壳压力和安全壳剂量。安全壳隔离信号的逻辑必须使每个输入参数能独立地触发安全壳隔离装置。但是在某些情况下，根据事件的性质和电厂的响应的不同，进入安全壳隔离信号逻辑的一些多样性参数达不到或不能同时达到它们的整定值，因此需要确定一个可接受的参数多样性水平。
如果采用分阶段隔离，除最后阶段外每个阶段必须采用多样信号触发。可能时最后阶段也必须用多样信号触发。
4.6.4安全壳隔离最迟必须与应急堆芯冷却同时投入。在分阶段隔离时，第一阶段隔离最迟必须与应急堆芯冷却同时投入。
4.6.5如果采用分阶段隔离，除下述系统外都必须自动隔离；
a.专设安全设施，
b. 在失水事故后不要求实施其功能，但需要时，可以用来完成类似于专设安全设施的功能的那些系统，如反应堆冷却剂泵运行所要求的流体系统。
如果不采用分阶段隔离，除专设安全设施外所有具有安全壳隔离装置的系统都必须自动隔离。
4.6.6在隔离最后阶段，必须考虑除专设安全设施以外在隔离初期阶段未被隔离的那些系统的自动隔离。
4.6.7对于除专设安全设施以外任一不隔离的系统，都必须有手段确定它们没有降低安全壳隔离功能的能力或影响专设安全设施运行。只要这些系统开始降低安全壳隔离功能或影响专设安全设施运行，就必须隔离这些系统，必须对不隔离的各系统的泄漏和管道破裂后果进行分析，以便确定如何尽快将这些功能下降系统进行隔离。
4.7超压保护准则
安全壳隔离后，隔离阀之间充满流体的管道内的压力或起隔离屏障的封闭环路内的压力可能由于管道内流体的热膨胀超过它的设计压力而受到损伤，为此必须对它们提供防止隔离后超压的超压保护。
只要能证明隔离后的压力不会超过管道和隔离屏障的设计压力，可以不要求超压保护。
有些安全壳隔离阀本身具有超压保护的功能，如图5和图6。
图5所示的止回阀，当隔离阀之间压力升高时可向安全壳内侧方向卸压。
图6所示的气动截止阀，只要其阀门弹簧设计成低于管道和阀门的设计压力时，可以打开阀门向安全壳内卸压。
有些安全壳隔离阀本身不具有超压保护功能、应另设超压保护，如图7、图8。但不得向安全壳外卸压。
图7所示是安全壳内的隔离阀加一旁通止回阀，超压时止回阀可向安全壳内侧方向卸压。
图8所示的卸压阀，超压时可向安全壳内侧卸压。
任何超压保护措施都必须在失水事故期间的最大背压条件下完成超压保护功能。
