ML15251A204

McGuire Nuclear Station Tech Spec Bases 3.8.4 - DC Sources - Operating

ML15251A204
Person / Time
Site:	McGuire, Mcguire
Issue date:	08/27/2015
From:	Duke Energy Carolinas
To:	Office of Nuclear Reactor Regulation
References
TR-NUC-MC-000527
Download: ML15251A204 (10)

Text

Distribution: Duke Energy Date: 8/27/2015Document Transmittal #: TR-NUC-MC-0005271. Gardner, Tray R D C M N R N M T A O M Proe su2. Mc Ginnis, Vickie L (At Mcguire) D C M N R N M T A O MProe su3. McCree, Victor M Released By:4. SCIENTECH CLEARWTR, FL Facility: MCGUIRE NUCLEAR STATION Duke Enerciy5. SERV BLDG FILE ROOM -SUBJECT 13225 Haqiers Ferry Road6. U S NUC REG WASHINGTON, DC Tech Spec Bases 3.8.4 -DC Sources -Operatina Document Management7. USNRC MG02M8. WESTINGHOUSE ELECTRIC CO LLC Huntersville, NC 28078Page 1 of 1 MNSDCRI~c~duke-enerav.comRemarks: This is Rev 137 of the Tech Spec Bases. Please chancie out the entire section 3.8.4. Reference TR-NUC-MC-O00446p DC Sources--OperatingB 3.8.4B 3.8 ELECTRICAL POWER SYSTEMSB 3.8.4 DC Sources-OperatingBASESBACKGROUNDThe station DC electrical power system provides the AC emergencypower system with control power. It also provides both motive andcontrol power to selected safety related equipment and preferred AC vitalbus power (via inverters). As required by 10 CFR 50, Appendix A,GDC 17 (Ref. 1), the DC electrical power system is designed to havesufficient independence, redundancy, and testability to perform its safetyfunctions, assuming a single failure. The DC electrical power system alsoconforms to the recommendations of Regulatory Guide 1.6 (Ref. 2) andIEEE-308 (Ref. 3).The 125 VDC electrical power system consists of two independent andredundant safety related Class 1 E DC electrical power subsystems(Train A and Train B). Each subsystem consists of two channels of125 VDC batteries (each battery 100% capacity), the associated batterycharger(s) for each battery, and all the associated control equipment andinterconnecting cabling.Additionally there is one spare battery charger, which provides backupservice in the event that the preferred battery charger is out of service. Ifthe spare battery charger is substituted for one of the preferred batterychargers, then the requirements of independence and redundancybetween subsystems are maintained.During normal operation, the 125 VDC load is powered from the batterychargers with the batteries floating on the system. In case of loss ofnormal power to the battery charger, the DC load is automaticallypowered from the station batteries.The Train A and Train B DC electrical power subsystems provide thecontrol power for its associated Class 1 E AC power load group, 4.16 kVswitchgear, and 600 V load centers. The DC electrical power subsystemsalso provide DC electrical power to the inverters, which in turn power theAC vital buses.The DC power distribution system is described in more detail in Bases forLCO 3.8.9, "Distribution System--Operating," and LCO 3.8.10,"Distribution Systems--Shutdown."McGuire Units 1 and 2 B3841Rvso o 3B 3.8.4-1Revision No. 137 DC Sources-OperatingB 3.8.4BASESBACKGROUND (continued)Each battery (EVCA, EVCB, EVCC, EVOD) has adequate storagecapacity to carry the required duty cycle for one hour after the loss of thebattery charger output. In addition, the battery is capable of supplyingpower for the operation of anticipated momentary loads during the onehour period.Each 125 VDC battery is separately housed in a ventilated room apartfrom its charger and distribution centers. Each channel is located in anarea separated physically and electrically from the other channel toensure that a single failure in one subsystem does not cause a failure in aredundant subsystem. There is no sharing between redundant Class 1 Esubsystems, such as batteries, battery chargers, or distribution panels.The batteries for the channels of DC are sized to produce requiredcapacity at 80% of nameplate rating, corresponding to warranted capacityat end of life cycles and the 100% design demand. Battery size is basedon 125% of required capacity and, after selection of an availablecommercial battery, results in a battery capacity in excess of 150% ofrequired capacity. The individual cell voltage limit is 2.13 V per cell. Theminimum battery terminal voltage limit is greater than or equal to 125 Vwhile on float charge as discussed in the UFSAR, Chapter 8 (Ref. 4).The criteria for sizing large lead storage batteries are defined in IEEE-485(Ref. 5).Each channel of DC has ample power output capacity for the steady stateoperation of connected loads required during normal operation, while atthe same time maintaining its battery bank fully charged. Each batterycharger also has sufficient capacity to restore the battery from the designminimum charge to its fully charged state within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> while supplyingnormal steady state loads discussed in the UFSAR, Chapter 8 (Ref. 4).APPLICABLE The initial conditions of Design Basis Accident (DBA) and transientSAFETY ANALYSES analyses in the UFSAR, Chapter 6 (Ref. 6), and in the UFSAR,Chapter 15 (Ref. 7), assume that Engineered Safety Feature (ESE)systems are OPERABLE.The OPERABILITY of the DC sources is consistent with the initialassumptions of the accident analyses and is based upon meeting thedesign basis of the unit. This includes maintaining the DC sourcesOPERABLE during accident conditions in the event of:McGuire Units 1 and 2 B3842Rvso o 3B 3.8.4-2Revision No. 137 DC Sources--OperatingB 3.8.4BASESAPPLICABLE SAFETY ANALYSES (continued)a. An assumed loss of all offsite AC power or all onsite AC power; andb. A worst case single failure.The DC sources satisfy Criterion 3 of 10 CFR 50.36 (Ref. 8).LCO Each DC channel consisting of one battery, battery charger for eachbattery and the corresponding control equipment and interconnectingcabling supplying power to the associated bus within the train is requiredto be OPERABLE to ensure the availability of the required power to shutdown the reactor and maintain it in a safe condition after an anticipatedoperational occurrence (AOO) or a postulated DBA. Loss of any channelof DC does not prevent the minimum safety function from beingperformed (Ref. 4).An OPERABLE channel of DC requires the battery and respectivecharger to be operating and connected to the associated DC bus.APPLICABILITY The DC electrical power sources are required to be OPERABLE inMODES 1, 2, 3, and 4 to ensure safe unit operation and to ensure that:a. Acceptable fuel design limits and reactor coolant pressureboundary limits are not exceeded as a result of AOOs or abnormaltransients; andb. Adequate core cooling is provided, and containment integrity andother vital functions are maintained in the event of a postulatedDBA.The DC electrical power requirements for MODES 5 and 6 are addressedin the Bases for LCO 3.8.5, "DC Sources-- Shutdown."ACTIONS A.1 and A.2Condition A represents one channel of DC with a loss of ability to fullyrespond to a DBA with the worst case single failure. Two hours isprovided to restore the channel of DC to OPERABLE status and isconsistent with the allowed time for an inoperable channel of DCdistribution system requirement.McGuire Units 1 and 2 B3843Rvso o 3B 3.8.4-3Revision No. 137 DC Sources-OperatingB 3.8.4BASESACTIONS (continued)If one of the required channels of DC is inoperable (e.g., inoperablebattery, inoperable battery charger(s), or inoperable battery charger andassociated inoperable battery), the remaining DC channels have thecapacity to support a safe shutdown and to mitigate an accidentcondition. If the channel of DC cannot be restored to OPERABLE status,Action A.2 must be entered and the DC channel must be energized froman OPERABLE channel, from the same train, within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Thecapacity of the redundant channel is sufficient to supply its normallysupplied channel and cross tied channel for the required time, in case of aDBA event. The inoperable channel of DC must be returned toOPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and the cross ties to the other channelopen. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time reflects a reasonable time to assessunit status as a function of the inoperable channel of DC and, if the DCchannel is not restored to OPERABLE status, to prepare to effect anorderly and safe unit shutdown.As part of the battery replacement project, the Completion Time that onechannel of DC source can be inoperable as specified by Required ActionA.2.2 may be extended beyond the "72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />" for up to 14 days. Thisallowance may be used one-time for each of the four DC channels. Uponcompletion of the battery replacement project, the Completion Timefootnote is no longer applicable and will expire on December 31, 2016.B.1 and B.2If the inoperable channel of DC cannot be restored to OPERABLE statuswithin the required Completion Time, the unit must be brought to a MODEin which the LCO does not apply. To achieve this status, the unit must bebrought to 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 to MODE 5 within 36hours. The allowed Completion Times are reasonable, based onoperating experience, to reach the required unit conditions from full powerconditions in an orderly manner and without challenging plant systems.The Completion Time to bring the unit to MODE 5 is consistent with thetime required in Regulatory Guide 1.93 (Ref. 9).SURVEILLANCE SR 3.8.4.1REQUIREMENTSVerifying battery terminal voltage while on float charge for the batterieshelps to ensure the effectiveness of the charging system and the ability ofthe batteries to perform their intended function. Float charge is thecondition in which the charger is supplying the continuous chargerequired to overcome the internal losses of a battery (or battery cell) andmaintain the battery (or a battery cell) in a fully charged state. Thevoltage requirements are based on the nominal design voltage of thebattery and are consistent with the initial voltages assumed in the batteryMcGuire Units 1 and 2 B3844Rvso o 3B3.8.4-4Revision No. 137 DC Sources-OperatingB 3.8.4BASESSURVEILLANCE REQUIREMENTS (continued)sizing calculations. The Surveillance Frequency is based on operatingexperience, equipment reliability, and plant risk and is controlled underthe Surveillance Frequency Control Program.SR 3.8.4.2Visual inspection to detect corrosion of the battery cells and connections,or measurement of the resistance of each intercell, interrack, intertier, andterminal connection, provides an indication of physical damage orabnormal deterioration that could potentially degrade batteryperformance. For any connection that shows corrosion, the resistanceshall be measured at that connection to verify acceptable connectionresistance (Ref. 10). The limits for battery connection resistance arespecified in Table 3.8.4-1.The plant safety analyses do not assume a specific battery connectionresistance value, but typically assume that the batteries will supplyadequate power for a specified period of time. The resistance of eachbattery connection varies independently from all the others. Some ofthese individual connection resistance values may be higher or lower thanthe others, and the battery will still be able to perform its design function.Overall connection resistance, which is the sum total of all connectionresistances, has a direct impact on battery operability. The values listed inTable 3.8.4-1 are based on the battery manufacturers recommendedconnection voltage drop. As long as battery connection resistance valuesare at or below the values listed in Table 3.8.4-1, battery operability willnot be in question based on intercell, interrack, intertier, and terminalconnection resistance.The Surveillance Frequency is based on operating experience, equipmentreliability, and plant risk and is controlled under the SurveillanceFrequency Control Program.SR 3.8.4.3Visual inspection of the battery cells, cell plates, and battery racksprovides an indication of physical damage or abnormal deterioration thatcould potentially degrade battery performance. The presence of physicaldamage or deterioration does not necessarily represent a failure of thisSR, provided an evaluation determines that the physical damage ordeterioration does not affect the OPERABILITY of the battery (its ability toperform its design function). The Surveillance Frequency is based onoperating experience, equipment reliability, and plant risk and iscontrolled under the Surveillance Frequency Control Program.McGuire Units 1 and 2 B3845Rvso o 3B 3.8.4-5Revision No. 137 DC Sources--OperatingB 3.8.4BASESSURVEILLANCE REQUIREMENTS (continued)SR 3.8.4.4 and SR 3.8.4.5Visual inspection and resistance measurements of intercell, interrack,intertier, terminal connections, and the average intercell connectionresistance provide an indication of physical damage or abnormaldeterioration that could indicate degraded battery condition. The limits forbattery connection resistance are specified in Table 3.8.4-1. Singleterminal connection resistance is defined as the measurement from eachindividual load cable lug to the battery cell post. Average intercellconnection resistance is defined as the battery manufacturer's maximumallowed intercell connection voltage drop divided by the maximum batteryduty cycle load current. The maximum allowable battery total intercellconnection resistance can then be defined as the average intercellconnection resistance times the total number of intercell connectors in thebattery string. Intercell connection is referring to the 56 copper connectionstraps between the battery lar posts and the battery terminal connections.The plant safety analyses do not assume a specific battery connectionresistance value, but typically assume that the batteries will supplyadequate power for a specified period of time. The resistance of eachbattery connection varies independently from all the others. Some ofthese individual connection resistance values may be higher or lower thanthe others, and the battery will still be able to perform its design function.Overall connection resistance, which is the sum total of all connectionresistances, has a direct impact on battery operability. The values listed inTable 3.8.4-1 are based on the battery manufacturers recommendedconnection voltage drop. As long as battery connection resistance valuesare at or below the values listed in Table 3.8.4-1, battery operability willnot be in question based on intercell, interrack, intertier, and terminalconnection resistance.The anticorrosion material is used to help ensure good electricalconnections and to reduce terminal deterioration. The visual inspectionfor corrosion is not intended to require removal of and inspection undereach terminal connection. The removal of visible corrosion is apreventive maintenance SR. The presence of visible corrosion does notnecessarily represent a failure of this SR provided visible corrosion isremoved during performance of SR 3.8.4.4. The Surveillance Frequencyis based on operating experience, equipment reliability, and plant risk andis controlled under the Surveillance Frequency Control Program.McGuire Units 1 and 2 B3846Rvso o 3B 3.8.4-6Revision No. 137 DC Sources--OperatingB 3.8.4BASESSURVEILLANCE REQUIREMENTS (continued)SR 3.8.4.6This SR requires that each battery charger be capable of supplying400 amps and 125 V for > 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. These requirements are based on thedesign requirements of the chargers. According to Regulatory Guide 1.32(Ref. 11), the battery charger supply is required to be based on thelargest combined demands of the various steady state loads and thecharging capacity to restore the battery from the design minimum chargestate to the fully charged state, irrespective of the status of the unit duringthese demand occurrences. The minimum required amperes andduration ensures that these requirements can be satisfied.The Surveillance Frequency is based on operating experience, equipmentreliability, and plant risk and is controlled under the SurveillanceFrequency Control Program.SR 3.8.4.7A battery service test is a special test of battery capability, as found, tosatisfy the design requirements (battery duty cycle) of the DC electricalpower system. The discharge rate and test length of 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> shouldcorrespond to the design duty cycle requirements as specified inReference 4.The Surveillance Frequency is based on operating experience, equipmentreliability, and plant risk and is controlled under the SurveillanceFrequency Control Program.This SR is modified by a Note. The Note allows the performance of amodified performance discharge test in lieu of a service test.The modified performance discharge test, as defined by IEEE-450 (Ref. 10)is a simulated duty cycle consisting of just two rates; the one minute ratepublished for the battery or the largest current load of the duty cycle,followed by the test rate employed for the performance test, both of whichenvelope the duty cycle of the service test. Since the ampere-hoursremoved by a rated one minute discharge represents a very small portion ofthe battery capacity, the test rate can be changed to that for theperformance test without compromising the results of the performancedischarge test. The battery terminal voltage for the modified performancedischarge test should remain above the minimum battery terminal voltagespecified in the battery service test for the duration of time equal to that ofthe service test.McGuire Units 1 and 2 B3847Rvso o 3B 3.8.4-7 DC Sources--OperatingB 3.8.4BASESSURVEILLANCE REQUIREMENTS (continued)A modified discharge test is a test of the battery capacity and its ability toprovide a high rate, short duration load (usually the highest rate of the dutycycle). This will often confirm the battery's ability to meet the critical periodof the load duty cycle, in addition to determining its percentage of ratedcapacity. Initial conditions for the modified performance discharge testshould be identical to those specified for a service test.SR 3.8.4.8A battery performance discharge test is a test of constant current capacity ofa battery, normally done in the as found condition, after having been inservice, to detect any change in the capacity determined by the acceptancetest. The test is intended to determine overall battery degradation due toage and usage.A battery modified performance discharge test is described in the Bases forSR 3.8.4.7 and in IEEE-450 (Ref. 10): Either the battery performancedischarge test or the modified performance discharge test is acceptable forsatisfying SR 3.8.4.8; however, only the modified performance dischargetest may be used to satisfy SR 3.8.4.8 while satisfying the requirements ofSR 3.8.4.7 at the same time.The acceptance criteria for this Surveillance are consistent with IEEE-450(Ref. 10). These references recommend that the battery be replaced if itscapacity is below 80% of the manufacturer's rating. A capacity of 80%shows that the battery rate of deterioration is increasing, even if there isample capacity to meet the load requirements.If the battery shows degradation, or if the battery has reached 85% of itsexpected life and capacity is < 100% of the manufacturer's rating, theSurveillance Frequency is reduced to 12 months. However, if the batteryshows no degradation but has reached 85% of its expected life, theSurveillance Frequency is only reduced to 24 months for batteries thatretain capacity _ 100% of the manufacturer's rating. Degradation isindicated, according to IEEE-450 (Ref. 10), when the battery capacitydrops by more than 10% relative to its capacity on the previousperformance test or when it is > 10% below the manufacturer's rating. TheSurveillance Frequency is based on operating experience, equipmentreliability, and plant risk and is controlled under the SurveillanceFrequency Control Program.McGuire Units 1 and 2 B3848Rvso o 3B 3.8.4-8Revision No. 137 DC Sources--OperatingB 3.8.4BASESREFERENCES1.2.3.4.5.6.7.8.9.10.11.12.10 CFR 50, Appendix A, GDC 17.Regulatory Guide 1.6, March 10, 1971.IEEE-308-1 971.UFSAR, Chapter 8.IEEE-485-1 983, June 1983.UFSAR, Chapter 6.UFSAR, Chapter 15.10 CFR 50.36, Technical Specifications, (c)(2)(ii).Regulatory Guide 1.93, December 1974.IEEE-450-1 995.Regulatory Guide 1.32, February 1977.IEEE-450-1 980.McGuire Units 1 and 2 B3849Rvso o 3B 3.8.4-9Revision No. 137