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Nuclear Plant - Active Component (Valves)

  1. Jun 27, 2011 #1
    This is for all you System guys. What are the classifications for a valve to be considered an Active Component? Also, if the valve is classified as an Active Component does it automatically mean that the valve is a Safety Related Valve? I have several valves in my system (Check, Control, Isolation) that are Safety Related Valves but are not considered Active Components... Why?

    Any NRC, IAEA, or the likes reference material is helpful.

  2. jcsd
  3. Jun 27, 2011 #2


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    A valve is an active component because it changes state. It is safety related and active if it has to reposition to accomplish its safety function. (For example an isolation valve must close to perform its safety function, an RHR vslve has to open to create the flowpath for its safety function, and an SRV must both open and close to perform its safety functions.) Not every valve is safety related, but every valve is an active component. An isolation valve that is installed for maintenance in a safety system may not be required to reposition for a safety function if it is normally open. In this case the valve has a safety function of pressure boundary, but no active safety functoion.

    I will see if I can find a discussion reference and edit this post. In the meantime you may want to search for :active component: or :active safety function: on the NRC website

    10 CFR 50 Appendix A Criterion 43 specifies valves as "active" components. The safety function for a valve requires that the system have a safety function. Any activation, isolation or repositioning of the valve during a mode change of the system will result in the valve having an active safety function. If the valve doesn't reposition it still has a passive safety function if the system is safety related.
    Last edited: Jun 27, 2011
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