Detail of EJ/T 331-1992

Introduction of EJ/T 331-1992

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.

Contents of EJ/T 331-1992

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