Nuclear Reactor Cooling System
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Questions and Answers

What is the design pressure that satisfies the commitment for the RNS?

  • 800 psig
  • 1000 psig
  • 900 psig (correct)
  • 1100 psig

    • During which operations does the RNS provide LTOP for the RCS?

  • Only during refueling operations
  • During refueling, startup, and shutdown operations (correct)
  • Only during startup and shutdown operations
  • Only during normal operation

    • What is the purpose of the IRWST Gravity Injection to RCS Hot-Leg thru RNS Suction function?

  • To reduce the RCS pressure
  • To provide makeup to the RCS hot leg during cold shutdown and refueling conditions (correct)
  • To increase the RCS temperature
  • To bypass the RNS during emergency situations

    • What is the benefit of using the RNS to cool the RCS following an MSLB?

    <p>It prevents continued secondary coolant steaming</p> Signup and view all the answers

    At what temperature does the release of airborne radionuclides cease after an MSLB?

    <p>Below boiling conditions</p> Signup and view all the answers

    What is the role of the RNS in plant recovery following an accident?

    <p>It provides closed-loop heat removal</p> Signup and view all the answers

    What is the primary purpose of the RNS system?

    <p>To remove decay heat from the RCS during normal operation</p> Signup and view all the answers

    Which of the following is a safety-related function of the RNS system?

    <p>CTMT Isolation</p> Signup and view all the answers

    Which valve is NOT part of the RCS pressure boundary isolation function?

    <p>RNS-V080 IRWST Suct Vent</p> Signup and view all the answers

    What is the purpose of the flow path available via the test connection in the discharge CTMT penetration?

    <p>To provide a flow path for the long-term CTMT-inventory makeup/ultimate removal</p> Signup and view all the answers

    What is the design consideration for the RNS piping and components outside containment?

    <p>To minimize the probability of containment bypass</p> Signup and view all the answers

    What is the function provided by the 2 parallel paths, each containing 2 MOVs in series in the RNS pump suction piping?

    <p>RCS pressure boundary isolation</p> Signup and view all the answers

    Which of the following is NOT a non-safety related function of the RNS system?

    <p>CTMT inventory makeup/ultimate removal</p> Signup and view all the answers

    What is the operating pressure of the RCS that the RNS piping and components are designed to withstand?

    <p>2235 psig</p> Signup and view all the answers

    Study Notes

    Purpose and Functions

    • The Reactor Natural circulation System (RNS) is an active, non-safety decay heat removal system.
    • It is used under normal conditions when the Steam Generator System (SGS) and Main Steam System (MSS) are ineffective.
    • During accident conditions, it supplements the Passive Exothermic System (PXS).
    • RNS provides cooling to the Reactor Coolant System (RCS) at reduced temperature and pressure conditions after shutdown.
    • It also cools the In-containment Refueling Water Storage Tank (IRWST) during normal plant conditions.

    CTMT Isolation

    • RNS provides CTMT isolation for the RNS piping that penetrates the Containment Thermal Treatment Module (CTMT) barrier.
    • Outside CTMT, valves RNS-V011, RNS-V012, and RNS-V022 provide isolation.
    • Inside CTMT, valves RNS-V002A/B, RNS-V013, RNS-V020, RNS-V021, RNS-V023, and RNS-V061 provide isolation.

    RCS Pressure Boundary Isolation

    • RNS provides a RCS boundary at the RNS suction and discharge interface with the RCS.
    • This function is provided by two parallel paths, each containing two Motor-Operated Valves (MOV) in series in the RNS pump suction piping and two parallel paths each containing a stop-check valve and a check valve in series in the pump discharge piping.
    • RCS pressure boundary valves include RNS-V001A/B, RNS-V002A/B, RNS-V015A/B, and RNS-V017A/B.

    CTMT Inventory M/U

    • RNS provides a flow path for long-term CTMT-inventory makeup/removal in case of design-basis leakage from CTMT after a Loss-of-Coolant Accident (LOCA).
    • This flow path is available via the test connection in the discharge CTMT penetration, which is normally locked-closed and plug-capped.

    Interfacing System LOCA

    • The RNS piping and components are designed to have an ultimate rupture strength not less than the RCS operating pressure (2235 psig), with a design pressure of 900 psig.

    LTOP and IRWST Gravity Injection

    • RNS provides Low-Temperature Overpressure Protection (LTOP) for the RCS during refueling, startup, and shutdown operations.
    • It also provides an alternate gravity-injection path through RNS-V023 to provide makeup to the RCS hot leg during cold shutdown and refueling conditions.

    RCS Cooldown and Shutdown/Post-Accident Heat Removal

    • Following a Main Steam Line Break (MSLB), RNS can be used to reduce the RCS temperature below boiling conditions within 72 hours after reactor shutdown.
    • It provides closed-loop heat removal from the core and the RCS during shutdown operations to achieve plant recovery following successful mitigation of an accident.

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    Description

    This quiz covers the purpose and safety-related functions of a cooling system used in nuclear reactors, including decay heat removal and cooling of the IRWST during normal plant conditions.

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