Containment Isolation Device for Fluid System after Loss of Coolant Accident
失水事故后流體系統的安全殼隔離裝置
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
失水事故后流體系統的安全殼隔離裝置
EJ/T 331—92
代替EJ 331—88
1主題內容與適用范圍
本標準規定了失水事故后貫穿安全殼流體系統的安全殼隔離及隔離裝置的設置、設計、試驗、操作和維修的基本要求。
本標準適用于壓水堆核電廠失水事故后流體系統的安全殼隔離。
2引用標準
HAF 0307核電廠維修
3術語
3.1事故accident
包括安全殼內的失水事故在內的一個單一事故，這一事故是假想的但不是不可能的，該事故將引起一道或一道以上裂變產物屏障失效。
3.2 事故隔離 accident isolation
關閉貫穿安全殼的流體管道上設置的隔離裝置，以阻止或減輕事故后果。
3.3事故隔離信號accident isolation signal
自動觸發隔離裝置實施事故隔離功能的信號。
3.4封閉環路closed system
貫穿安全殼，在安全殼內或在安全殼外是一個閉環管路。在正常運行期間或失水事故時，安全殼內的封閉環路既不與一次冷卻劑管道直接連通，也不與安全殼大氣相通。
3.5安全殼大氣containment atmosphere
安全殼包容的自由空間內的氣體。
3.6安全殼隔離信號containment isolation signal
用來自動觸發安全殼隔離裝置實施其隔離功能的信號。該信號由保護系統發出或由操縱員在主控室發出。
3.7隔離屏障isolation barrier(s)
阻止貫穿安全殼流體系統中的流體流出安全殼的機械裝置，如閥門、封閉環路或法蘭盲板。
3.8隔離屏障防護isolation barrier protection
在發生外部事件(如飛射物、管道甩擊、噴射力或自然現象)時，防止隔離屏障喪失功能的保護措施。
3.9隔離閥密封系統isolation valve seal system
控制隔離閥泄漏的系統。
3.10飛射物防護missile protection
用實體屏障、限止器或設計布置防止飛射物(包括噴射力、管道甩擊)對構筑物、系統或部件的影響。
3.11動力源故障motive power filure
喪失驅動源。
3.12 保護系統protection system
產生自動觸發安全殼隔離裝置運行信號的系統，包括所有的電氣、機械器件和從敏感元件到閥門操作器輸入端的線路。
3.13行政控制 administrative controls
通過規則、指令、規程、政策、實施方法或權限和責任的分配進行控制。
3.14 自動隔離閥automatic isolation valve
收到保護系統發出的隔離信號后不需由操作員操作而自動關閉的閥門或簡單止回閥。
3.15安全殼隔離containment isolation
關閉貫穿安全殼流體系統中的安全殼隔離閥，將放射性產物封閉在安全殼內。
3.16分階段隔離phased isolation
根據貫穿安全殼流體系統減輕事故后果或維持電廠安全狀態所需的能力，用不同測量參數值或它們的不同組合發出安全殼隔離信號，使貫穿安全殼的流體系統分組依次隔離。
3.17動力驅動裝置power operator
利用氣、電、液壓或彈簧力來操作閥門的裝置。
3.18簡單止回閥simple check valve
只靠流體反向流動關閉的閥門。
3.19反應堆冷卻劑壓力邊界reacor coolant pressure boundary
包括反應堆壓力容器、穩壓器、蒸汽發生器一次側、控制棒驅動機構承壓殼、堆芯測量儀表管和反應堆冷卻劑管道、泵體和閥門等承壓部件，它們是：
a. 反應堆冷卻劑系統的組成部分；
b. 與反應堆冷卻劑系統連接直到并包括下列任何或全部閥門：貫穿安全殼的管道中最外一個安全殼隔離閥；反應堆正常運行期間通常關閉的兩個閥的第二個閥，該閥所在管道不貫穿安全殼；反應堆冷卻劑系統的安全閥和卸壓閥。
3.20鎖關隔離閥sealed clsed isolation valve
用下列方式之一由行政控制保持在關閉狀態的閥門：
a. 用機械裝置或鎖將閥門保持在關閉位置；
b. 用封印或鎖鎖住已關閉閥的手操作器；
c. 用封印或鎖鎖住電閘或動力源，防止向閥門供給動力。
3.21閥門關閉時間valve closure time
從閥門驅動裝置得到驅動動力到閥門完全關閉所需的時間，這段時間不包括儀表和控制滯后時間。
3.22多重系統redudant system
兩個或多個系統在正常運行或事故時能獨立完成同樣功能而且與運行狀態或另一個系統是否失效無關。
3.23 閥位valve position
指閥門開或關的狀態。
3.24全行程時間full-stroke time
從發出動作信號到閥門動作過程結束的時間間隔。
3.25 能動閥門 active valves
執行其功能時要求改變閥位的閥門。
3.26非能動閥門passive valves
執行其功能時不要求改變閥位的閥門。
3.27 A類閥門 category A
在關閉位置執行其功能時，閥座的泄漏量不允許超過規定的最大值的閥門。
3.28 B類閥門category B
在關閉位置執行其功能時，閥座的泄漏量并不重要的閥門。
3.29 C類閥門category C
能響應系統內某些特性參數，如壓力(卸壓閥)或流向(止回閥)的變化而自動操作的閥門。
3.30 D類閥門 category D
在能源的作用下僅能操作一次的閥門，如炸破盤或爆破致動的閥門。
3.31 動作操演 exercising
根據直接的或間接的目視或其它能明確指示閥門運行部件動作良好的方法進行的一種驗證試驗。
3.32在役壽期inservice life
從安裝和驗收直到退役的時間周期。
3.33 在役試驗 inservice test
通過觀察或測量獲得資料以確定閥門執行其功能能力的一種特殊試驗方法。
3.34維護maintenance
為矯正或防止異常和不良工況而進行的閥門常規保養。
4安全殼隔離設計準則
4.1貫穿安全殼的流體系統
必須在貫穿安全殼的每根管道上設置安全殼隔離屏障，在安全殼內發生失水事故或其它要求安全殼隔離的事故時，必須能自動而又可靠地隔離，以確保安全殼的密封防漏性能。
安全殼隔離屏障可以是隔離閥、封閉環路或法蘭盲板。
安全殼隔離設施應采用多重性和多樣性設計原則。通常，在貫穿安全殼的每根流體管道上串聯設置兩個隔離閥。每個隔離閥門必須足以限制放射性物質泄漏在可接受的限值內，并必須能可靠而獨立地動作。假定一個單一故障發生時必須能實施安全殼隔離。
設計貫穿安全殼的流體系統必須考慮要能定期進行隔離閥和有關設備的可運行性和泄漏率試驗，并確認閥門的泄漏是在允許的范圍內。
安全殼隔離設施之間貫穿安全殼部分的連接管道必須可進行泄漏檢測，并要有超壓保護。
4.2安全殼隔離閥設置準則
4.2.1 貫穿安全殼且屬于反應堆冷卻劑壓力邊界的一部分的管道，除另有條文規定外，必須按照下列方式之一設置安全殼隔離閥(如圖1)：
a. 安全殼內一只鎖關隔離閥，安全殼外一只鎖關隔離閥；
b. 安全殼內一只自動隔離閥，安全殼外一只鎖關隔離閥；
c. 安全殼內一只鎖關隔離閥，安全殼外一只自動隔離閥；
d. 安全殼內一只自動隔離閥，安全殼外一只自動隔離閥。
簡單止回閥不能作為安全殼外的自動隔離閥。
正常運行時，流體只有流入而沒有流出(指安全殼)的管道，簡單止回閥可以作為安全殼內的自動隔離閥。
安全殼外的隔離閥必須盡可能靠近安全殼。自動隔離閥必須設計成在失去操作動力時處于失水事故時要求實施其功能的狀態。
為了確保安全，必要時應規定其它一些適當要求.使這些管線或與其相連管線破裂的幾率或后果減到最小。在確定這些諸如更高質量的設計、制造及試驗，在役檢查的補充措施、防止更加嚴重的自然災害以及附加的隔離閥和封閉等要求是否合適時，應考慮到人口密度、利用特點以及廠址周圍的自然特性。
4.2.2貫穿安全殼且與安全殼大氣相通的管道，除另有條文規定外.必須按照下列方式之一設置安全殼隔離閥(如圖1)：
a. 安全殼內一只鎖關隔離閥，安全殼外一只鎖關隔離閥；
b. 安全殼內一只自動隔離閥，安全殼外一只鎖關隔離閥；
c. 安全殼內一只鎖關隔離閥，安全殼外一只自動隔離閥；
d. 安全殼內一只自動隔離閥，安全殼外一只自動隔離閥。
簡單止回閥不能作為安全殼外的自動隔離閥。
正常運行時，流體只有流入(安全殼)而無流出的管道，簡單止回閥可以作為安全殼內的自動隔離閥。
安全殼外的隔離閥必須盡可能靠近安全殼，自動隔離閥必須設計成在失去操作動力時處于失水事故時要求實施其功能的狀態。
4.2.3貫穿安全殼且既不是反應堆冷卻劑壓力邊界的一部分，不直接與安全殼大氣相通的封閉環路，每根貫穿安全殼的管道必須至少有一個安全殼隔離閥，該閥可以是自動隔離閥、鎖關隔離閥或遠距離手動隔離閥。隔離閥必須設置在安全殼外，且盡可能靠近安全殼。簡單止回閥不能作為自動隔離閥(如圖2)。
4.2.4 對于盲端的小儀表管線(例如內徑<26mm的管線)，只要求在安全殼外則設置一個手操作隔離閥。在安全殼內和安全殼外都封閉的儀表管道，如安全殼壓力測量管線，只要設計成能承受安全殼結構完整性試驗的最大壓力、能承受安全殼的設計溫度并具有防飛射物和動態效應的措施，可以不設隔離閥。
4.2.5下列系統的隔離功能可由遠距離手動隔離閥代替自動隔離閥來完成：
a. 專設安全設施；
b. 失水事故時不要求執行功能，但需要時能完成專設安全設施同樣功能的那些系統，如主冷卻劑泵運行所需要的流體系統。
當安全殼內和(或)安全殼外的流體管道可能發生的故障能被探測到并且能夠用遠距離手動保持隔離這些管道，那么可以用遠距離手動隔離閥。
4.2.6專設安全設施或試驗專設安全設施所要求的系統，只要能證實只需一個閥門就能適應單一能動故障，并且流體系統功能的可靠性采用一個閥門比二個串聯閥門得到增強，或者在安全殼外的封閉環路滿足4.3.2要求，則允許只在安全殼外設一只隔離閥。
只設一只隔離閥的封閉式環路除了能證實在壓力大于或等于安全殼設計壓力時能保持系統的完整性外必須按照本標準6.2的有關要求進行泄漏試驗。
該閥及其與安全殼之間的連接管道必須包容在一個防泄漏密封殼或可控泄漏間內以避免向環境泄漏(如圖3)，或者設計閥門和連接管道時采取保守的設計，能消除管道完整性的破壞，則可以不考慮防泄漏密封殼或可控泄漏間，在此情況下必須要能檢測從閥桿和(或)閥體密封處的泄漏并消除泄漏。
4.2.7如果專設安全設施或試驗專設安全設施所要求的系統需要兩個串聯隔離閥，而其中之一又不可能設置在安全殼內時，兩個隔離閥均可設置在安全殼外，并盡可能靠近安全殼。靠近安全殼的閥及其與安全殼之間的連接管道必須包容在防泄漏密封殼或可控泄漏間內以防止向環境泄漏(如圖4)，或者該閥門和管道采取保守的設計，能消除管道完整性的破壞，則可以不考慮防泄漏密封殼或可控泄漏間，在此情況下必須要能檢測從閥桿和(或)閥體密封處的泄漏，并消除泄漏。
4.2.8卸壓閥只要滿足本標準的要求可以作為卸壓方向或回流方向的隔離閥。
4.2.9工藝閥門只要滿足本標準的要求，則可以作為安全殼隔離閥。
4.3封閉環路準則
4.3.1安全殼內的封閉環路作為安全殼兩個隔離裝置之一，須滿足下列全部要求：
a. 既不與一次冷卻劑管道連接，也不與安全殼大氣連通；
b. 要有防飛射物、管道甩動和噴射力沖擊的保護措施；
c. 滿足安全二級設計要求；
d. 能承受安全殼結構完整性試驗壓力相等的外壓；
e. 能承受安全殼設計溫度；
f. 能承受失水事故所造成的瞬態和事故后的環境條件；
g. 滿足抗震I類設計要求；
h. 有隔離后由于事故引起安全殼內溫度升高使系統內流體的熱膨脹引起超壓的超壓保護；
i. 要能進行泄漏試驗并滿足安全殼整體泄漏試驗的有關要求。
如果上述要求不能全部滿足，則設置該封閉環路的安全殼隔離設施必須滿足本標準4.2的要求。
4.3.2安全殼外的封閉環路作為專設安全設施或專設安全設施有關系統的兩個隔離裝置之一時，該封閉環路必須滿足下列全部要求：
a. 與外部大氣不連通；
b. 滿足安全二級設計要求；
c. 能承受安全殼設計溫度和壓力；
d. 能承受失水事故瞬態和環境條件；
e. 滿足抗震1類設計要求；
f. 具有防隔離后系統內流體熱膨脹引起超壓的超壓保護；
g. 如果當高能管道破裂需要安全殼隔離時，應具有防高能流體管道破裂對封閉環路影響的保護措施；
h. 具有防飛射物的保護措施；
i. 能進行泄漏試驗。
4.4隔離閥設計準則
所有安全殼隔離閥必須能完全關死以滿足安全殼泄漏試驗的有關要求。
安全殼隔離閥可以是自動隔離閥、鎖關隔離閥或遠距離手動閥。隔離閥的關閉時間要求(包括檢測、操作時間)必須確保閥門預期的安全功能。
4.5連接管道準則
4.5.1 安全殼與安全殼外隔離閥之間的連接管道和安全殼外的兩個隔離閥之間的連接管道必須：
a. 至少滿足安全二級設計要求；
b. 能承受安全殼設計溫度；
c. 能承受安全殼結構完整性試驗壓力相等的內壓；
d. 能承受失水事故瞬態和事故后的環境條件；
e. 滿足抗震I類設計要求；
f. 當高能管道破裂需要安全殼隔離時，應具有防高能流體管道破裂對連接管道影響的保護措施；
g. 具有隔離后由于流道內流體熱膨脹引起超壓的超壓保護；
h. 具有防飛射物的保護措施。
4.5.2安全殼與安全殼內隔離閥之間的連接管道必須：
a. 滿足安全二級設計要求；
b. 能承受安全殼設計溫度；
c. 能承受安全殼結構完整性試驗壓力相同的外壓；
d. 能承受失水事故瞬態和事故后的環境條件；
e. 滿足抗震1類設計要求；
f. 如果需要，還應具有防失水事故引起的飛射物、管道甩動和噴射力的保護措施；
g. 具有隔離后由于流道內流體熱膨脹引起超壓的超壓保護。
4.5.3安全殼隔離閥之間的連接管道必須要能進行泄漏檢測。
4.6安全殼隔離觸發準則
4.6.1對于除專設安全設施和完成專設安全設施同樣功能的系統以外的其它系統，觸發其安全殼隔離的隔離信號必須優先于其它觸發信號。
4.6.2設計者必須確定是否需要分階段隔離，并以文件形式說明確定的依據。分階段隔離可以利用潛在有利的流體系統去減輕事故后果和增強電廠的安全。
4.6.3如果不采用分階段隔離，安全殼隔離信號必須由多種參數發出，如堆芯應急冷卻的啟動、安全殼壓力和安全殼劑量。安全殼隔離信號的邏輯必須使每個輸入參數能獨立地觸發安全殼隔離裝置。但是在某些情況下，根據事件的性質和電廠的響應的不同，進入安全殼隔離信號邏輯的一些多樣性參數達不到或不能同時達到它們的整定值，因此需要確定一個可接受的參數多樣性水平。
如果采用分階段隔離，除最后階段外每個階段必須采用多樣信號觸發。可能時最后階段也必須用多樣信號觸發。
4.6.4安全殼隔離最遲必須與應急堆芯冷卻同時投入。在分階段隔離時，第一階段隔離最遲必須與應急堆芯冷卻同時投入。
4.6.5如果采用分階段隔離，除下述系統外都必須自動隔離；
a.專設安全設施，
b. 在失水事故后不要求實施其功能，但需要時，可以用來完成類似于專設安全設施的功能的那些系統，如反應堆冷卻劑泵運行所要求的流體系統。
如果不采用分階段隔離，除專設安全設施外所有具有安全殼隔離裝置的系統都必須自動隔離。
4.6.6在隔離最后階段，必須考慮除專設安全設施以外在隔離初期階段未被隔離的那些系統的自動隔離。
4.6.7對于除專設安全設施以外任一不隔離的系統，都必須有手段確定它們沒有降低安全殼隔離功能的能力或影響專設安全設施運行。只要這些系統開始降低安全殼隔離功能或影響專設安全設施運行，就必須隔離這些系統，必須對不隔離的各系統的泄漏和管道破裂后果進行分析，以便確定如何盡快將這些功能下降系統進行隔離。
4.7超壓保護準則
安全殼隔離后，隔離閥之間充滿流體的管道內的壓力或起隔離屏障的封閉環路內的壓力可能由于管道內流體的熱膨脹超過它的設計壓力而受到損傷，為此必須對它們提供防止隔離后超壓的超壓保護。
只要能證明隔離后的壓力不會超過管道和隔離屏障的設計壓力，可以不要求超壓保護。
有些安全殼隔離閥本身具有超壓保護的功能，如圖5和圖6。
圖5所示的止回閥，當隔離閥之間壓力升高時可向安全殼內側方向卸壓。
圖6所示的氣動截止閥，只要其閥門彈簧設計成低于管道和閥門的設計壓力時，可以打開閥門向安全殼內卸壓。
有些安全殼隔離閥本身不具有超壓保護功能、應另設超壓保護，如圖7、圖8。但不得向安全殼外卸壓。
圖7所示是安全殼內的隔離閥加一旁通止回閥，超壓時止回閥可向安全殼內側方向卸壓。
圖8所示的卸壓閥，超壓時可向安全殼內側卸壓。
任何超壓保護措施都必須在失水事故期間的最大背壓條件下完成超壓保護功能。
