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McGuire Units 1 and 2 B 3.7.6-1 Revision No. 127 CCW System B 3.7.6 B 3.7 PLANT SYSTEMS B 3.7.6 Component Cooling Water (CCW) System BASES BACKGROUND The CCW System provides a heat sink for the removal of process and operating heat from safety related components during a Design Basis Accident (DBA) or transient. During normal operation, the CCW System also provides this function for various nonessential components, as well as the spent fuel storage pool. The CCW System serves as a barrier to the release of radioactive byproducts between potentially radioactive systems and the Nuclear Service Water System (NSWS), and thus to the environment.
The CCW System is arranged as two independent, full capacity cooling loops, and has isolatable nonsafety related components. Each safety related train includes two pumps, surge tank, heat exchanger, piping, valves, and instrumentation. Each safety related train is powered from a separate bus. An open surge tank in the system provides pump trip protective functions to ensure that sufficient net positive suction head is available. Both pumps in each train are automatically started on receipt of a safety injection or Station Blackout signal, and all nonessential components are isolated.
Additional information on the design and operation of the system, along with a list of the components served, is presented in the UFSAR, Section 9.2 (Ref. 1). The principal safety related function of the CCW System is the removal of decay heat from the reactor via the Residual Heat Removal (RHR) System. This may be during a normal or post accident cooldown and shutdown.
APPLICABLE The design basis of the CCW System is for one CCW train to remove the SAFETY ANALYSES post loss of coolant accident (LOCA) heat load from the containment sump during the recirculation phase. The maximum CCW temperature for all modes of CCW pump operation, including cooldown to MODE 5 (Tcold
<200oF), is 160oF, based on pump design and piping analysis. Design supply temperature of less than 110 oF and normal return temperature less than 155 oF was used to size the CCW heat exchanger (Ref. 1).
CCW System B 3.7.6 BASES McGuire Units 1 and 2 B 3.7.6-2 Revision No. 127 APPLICABLE SAFETY ANALYSES (continued)
The CCW System is designed to perform its function with a single failure of any active component, assuming a loss of offsite power.
The CCW System also functions to cool the unit from RHR entry conditions (Tcold < 350°F), to MODE 5 (Tcold < 200°F), during normal and post accident operations. The time required to cool from 350°F to 200°F is a function of the number of CCW and RHR trains operating. One CCW train is sufficient to remove decay heat during subsequent operations with Tcold < 200°F.
The CCW System satisfies Criterion 3 of 10 CFR 50.36 (Ref. 2).
LCO The CCW trains are independent of each other to the degree that each has separate controls and power supplies and the operation of one does not depend on the other. In the event of a DBA, one CCW train is required to provide the minimum heat removal capability assumed in the safety analysis for the systems to which it supplies cooling water. To ensure this requirement is met, two trains of CCW must be OPERABLE.
At least one CCW train will operate assuming the worst case single active failure occurs coincident with a loss of offsite power.
A CCW train is considered OPERABLE when:
- a.
Both pumps and associated surge tank are OPERABLE; and
- b.
The associated piping, valves, heat exchanger, and instrumentation and controls required to perform the safety related function are OPERABLE.
The isolation of CCW from other components or systems not required for safety may render those components or systems inoperable but does not affect the OPERABILITY of the CCW System.
APPLICABILITY In MODES 1, 2, 3, and 4, the CCW System is a normally operating system, which must be prepared to perform its post accident safety functions, primarily RCS heat removal, which is achieved by cooling the RHR heat exchanger.
In MODE 5 or 6, the requirements of the CCW System are determined by the systems it supports.
CCW System B 3.7.6 BASES McGuire Units 1 and 2 B 3.7.6-3 Revision No. 127 ACTIONS A.1 Required Action A.1 is modified by a Note indicating that the applicable Conditions and Required Actions of LCO 3.4.6, "RCS LoopsMODE 4,"
be entered if an inoperable CCW train results in an inoperable RHR loop.
This is an exception to LCO 3.0.6 and ensures the proper actions are taken for these components.
If one CCW train is inoperable, action must be taken to restore OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. In this Condition, the remaining OPERABLE CCW train is adequate to perform the heat removal function.
The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is reasonable, based on the redundant capabilities afforded by the OPERABLE train, and the low probability of a DBA occurring during this period.
B.1 and B.2 If the CCW train cannot be restored to OPERABLE status within the associated Completion Time, the unit must be placed in a MODE in which the LCO does not apply. To achieve this status, the unit must be placed in at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in MODE 5 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. The allowed Completion Times are reasonable, based on operating experience, to reach the required unit conditions from full power conditions in an orderly manner and without challenging unit systems.
SURVEILLANCE SR 3.7.6.1 REQUIREMENTS This SR is modified by a Note indicating that the isolation of the CCW flow to individual components may render those components inoperable but does not affect the OPERABILITY of the CCW System.
Verifying the correct alignment for manual, power operated, and automatic valves in the CCW flow path provides assurance that the proper flow paths exist for CCW operation. This SR does not apply to valves that are locked, sealed, or otherwise secured in position, since these valves are verified to be in the correct position prior to locking, sealing, or securing. This SR also does not apply to valves that cannot be inadvertently misaligned, such as check valves. This Surveillance does not require any testing or valve manipulation; rather, it involves verification that those valves capable of being mispositioned are in the correct position.
The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
CCW System B 3.7.6 BASES McGuire Units 1 and 2 B 3.7.6-4 Revision No. 127 SURVEILLANCE REQUIREMENTS (continued)
SR 3.7.6.2 This SR verifies proper automatic operation of the CCW valves on an actual or simulated actuation safety injection signal. The CCW System is a normally operating system that cannot be fully actuated as part of routine testing during normal operation. This Surveillance is not required for valves that are locked, sealed, or otherwise secured in the required position under administrative controls. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
SR 3.7.6.3 This SR verifies proper automatic operation of the CCW pumps on an actual or simulated actuation signal. The CCW System is a normally operating system that cannot be fully actuated as part of routine testing during normal operation. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.
REFERENCES
- 1.
UFSAR, Section 9.2.
- 2.
10 CFR 50.36, Technical Specifications, (c)(2)(ii).