View source for RS-20-143, Response to Request for Additional Information Regarding Application to Revise Technical Specifications 3.8.1, AC Sources- Operating

{{Adams
| number = ML20325A252
| issue date = 11/20/2020
| title = Response to Request for Additional Information Regarding Application to Revise Technical Specifications 3.8.1, AC Sources- Operating
| author name = Murray D
| author affiliation = Exelon Generation Co, LLC
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000454, 05000455, 05000456, 05000457
| license number = NPF-037, NPF-066, NPF-072, NPF-077
| contact person = 
| case reference number = RS-20-143
| document type = Letter type:RS, Response to Request for Additional Information (RAI)
| page count = 13
| project = 
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:4300 Winfield Road Warrenville, IL 60555 www.exeloncorp.com 10 CFR 50.90 RS-20-143 November 20, 2020 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455

==Subject:==
Response to Request for Additional Information regarding Braidwood Station and Byron Station Application to Revise Technical Specifications 3.8.1, "AC Sources-Operating"

==References:==
: 1. Letter from D. Murray (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Application to Revise Technical Specifications 3.8.1, 'AC Sources-Operating,'" dated June 26, 2020 (ML20178A467)
: 2. Email from J. Wiebe (Project Manager, U.S. Nuclear Regulatory Commission) to J. Taken (Exelon Generation Company, LLC), "Preliminary RAIs for LAR Regarding Non-conservative TS EDG Frequency Tolerance," dated October 9, 2020 In Reference 1, Exelon Generation Company, LLC (EGC) submitted a request to the U.S.
Nuclear Regulatory Commission (NRC) for an amendment to Renewed Facility Operating License Nos. NPF-72 and NPF-77 for Braidwood Station (Braidwood), and Renewed Facility Operating License Nos. NPF-37 and NPF-66 for Byron Station (Byron).
The License Amendment Request (LAR) is required to correct a non-conservative Technical Specifications (TS). Plant operations are currently administratively controlled as described in NRC Administrative Letter (AL) 98-10, "Dispositioning of Technical Specifications that are Insufficient to Assure Plant Safety." In accordance with the guidance in AL 98-10, the LAR is required to resolve non-conservative TS and is not a voluntary request to change the Braidwood and Byron Stations' licensing basis. Therefore, the request is not subject to "forward fit" considerations as described in a letter from S. G. Burns (NRC, General Counsel) to E. C.
Ginsberg (NEI), dated July 14, 2010 (ADAMS Accession No. ML101960180)
On October 9, 2020, the NRC provided a Preliminary Request for Additional Information (RAI)
(Reference 2) to support their continued review of Reference 1. A clarification call between

U.S. Nuclear Regulatory Commission November 20, 2020 Page 2 NRC and EGC was held on October 26, 2020, and no changes to the RAIs were necessary.
Response to the RAIs was requested within 30 days of the clarification call and is provided in the attachment to this letter.
EGC has reviewed the information supporting a finding of no significant hazards consideration and the environmental consideration provided to the NRC in Reference 1. The supplemental information provided in this letter does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. Furthermore, the supplemental information provided in this letter does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.
There are no regulatory commitments contained in this response.
Should have any questions regarding this submittal, please contact Jason Taken at 630-806-9804.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 20th day of November 2020.
Respectfully, Dwi Murray Sr. Manager, Licensing Exelon Generation Company, LLC

==Attachment:==
Response to Request for Additional Information cc:    NRC Regional Administrator - Region III NRC Senior Resident Inspector - Braidwood Station NRC Senior Resident Inspector - Byron Station NRC Project Manager, NRR - Braidwood and Byron Stations Illinois Emergency Management Agency - Division of Nuclear Safety

ATTACHMENT Braidwood Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Renewed Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455 Response to Request for Additional Information

ATTACHMENT Response to Request for Additional Information General Design Criterion (GDC)-17, "Electric power systems," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, requires, in part, that nuclear power plants have onsite and offsite electric power systems to permit the functioning of structures, systems, and components (SSCs) that are important to safety.
The following information is needed to determine if the affected SSCs will function in the specified frequency band:
RAI EPNB-1 For the emergency diesel generator (EDG) lube oil pump and jacket water pump on the EDG skid, provide the (1) flow rate at 59.5 Hertz (Hz), 60 Hz, and 60.5 Hz, (2) the discharge pressure at 59.5 Hz, 60 Hz, and 60.5 Hz, and (3) required net positive suction head and available net positive suction head at 59.5 Hz, 60 Hz, and 60.5 Hz. Also provide the minimum required flow rate, the minimum required discharge pressure, and any low-pressure alarm settings for each pump.
EGC RESPONSE:
The RAI responses provided apply to both Byron Station and Braidwood Station due to the similarity in EDG and emergency power system design.
Engine Driven Jacket Water (JW) Pump:
The nominal rating of the JW Pump is 1350 gpm at 70 feet of developed head with the engine operating at rated speed (600 rpm or 60.0 Hz) (Reference 1). No pressure indicators are provided on the EDG skid for measuring JW Pump suction and discharge pressure. An alarm-only function is provided for pump discharge pressure. The alarm setpoint is 12 psig (Reference 2). No engine trip functions are provided for low JW Pump discharge pressure. JW system flow rate is not measured and a minimum flow rate is not specified by the EDG manufacturer. Adequate JW system hydraulic performance is verified by JW system operating temperatures and the absence of the JW Pump low pressure alarm.
The Net Positive Suction Head (NPSH) analysis for JW Pump (Reference 3) indicates that for minimal acceptable level in the JW Standpipe, the pump suction head (static head minus suction losses) is approximately 7.6 feet at nominal flow conditions. This corresponds to a pump suction pressure of 3.2 psig at 170&deg;F (density = 60.794 lbm/ft3). The pump developed head of 70 feet corresponds to a pump differential pressure of 29.5 psid at 170&deg;F. Therefore, the JW Pump discharge pressure is approximately 32.7 psig at nominal JW system temperature conditions.
Using the affinity laws as described in WCAP-17308-NP-A (Reference 4) to adjust flow and pump differential pressure, the following table specifies the JW Pump discharge pressure and flow conditions with the EDG operating at 60.0+/-0.5 Hz conservatively ignoring the variation in pump suction pressure as a function of flow to simplify the analysis.
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ATTACHMENT Response to Request for Additional Information JW Pump Parameter         59.5 Hz (595 rpm)      60.0 Hz (600 rpm)         60.5 Hz (605 rpm)
Pump Flow (gpm)                1339                    1350                     1361 Pump Discharge 32.2                   32.7                      33.2 Pressure (psig)
As indicated in the table above, the impact of the EDG operating speed/frequency of 60.0+/-0.5 Hz has an insignificant impact on JW Pump performance. JW Pump discharge pressure remains significantly above the low pressure alarm setpoint.
The NPSH analysis for the JW Pump considers minimum level in the JW Standpipe, maximum JW temperature, and conservative pressure losses between the pump and standpipe. The NPSH available under these conditions is 17.51 feet. The only component of the calculated NPSH available impacted by flow are the suction line losses due to piping and pipe fittings. The analysis determined a suction line head loss of 1.06 feet at 1350 gpm. The required NPSH in the analysis is 16.8 feet at nominal pump conditions. The affinity laws are used to adjust the suction line losses for the EDG operating at 60.0+/-0.5 Hz. It is conservative to not adjust the NPSH required at lower EDG operating speeds. The NPSH required at higher EDG operating speed is adjusted conservatively in a manner consistent with the affinity laws for differential pressure (Reference 5). The following table specifies the JW Pump NPSH available and required with the EDG operating at 60.0+/-0.5 Hz.
JW NPSH Parameter          59.5 Hz (595 rpm)      60.0 Hz (600 rpm)         60.5 Hz (605 rpm)
NPSH Available 17.53                  17.51                     17.49 (feet)
NPSH Required 16.8                   16.8                     17.08 (feet)
As indicated in the table above, JW Pump NPSH available remains greater than NPSH required with the EDG operating at 60.0+/-0.5 Hz.
Engine Driven Lube Oil (LO) Pump:
The LO Pump is physically attached to the EDG crankcase. The nominal rating of the LO Pump at rated EDG speed is 670 gpm at 90 psig discharge pressure (References 6 and 7). No pressure indicators are provided on the EDG skid for measuring LO Pump suction and discharge pressure. LO system flow rate is not measured and a minimum flow rate is not specified by the EDG manufacturer. In addition to LO system operating temperatures, system performance is monitored by the pressure delivered to the EDG bearings. The normal pressure is 50 psig which is maintained/controlled by a pressure regulating relief valve. This valve relieves LO Pump excess pumping after providing flow through skid mounted filtration and cooling components. A low pressure alarm is provided at 35 psig (Reference 8) and an engine trip/alarm occurs at 30 psig (Reference 9). The engine trip at 30 psig is bypassed during the emergency mode operation of the EDG.
Ignoring any suction pressure at the LO Pump inlet, the LO Pump discharge pressure and flow can be determined using the affinity laws for EDG operation at 60.0+/-0.5 Hz.
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ATTACHMENT Response to Request for Additional Information LO Pump Parameter         59.5 Hz (595 rpm)         60.0 Hz (600 rpm)        60.5 Hz (605 rpm)
Pump Flow (gpm)                 664                      670                     676 Pump Discharge 88.5                      90                     91.5 Pressure (psig)
Any small variations from nominal EDG operating speed can be addressed by the operation of the pressure regulating relief valve to deliver the required pressure/flow to the EDG bearings.
No NPSH analysis exists for the LO Pump. Sufficient NPSH is ensured by maintaining oil level in the engine crankcase. This parameter is monitored during EDG operation and oil is added if level is one inches below nominal level (blue line in sightglass). An alarm is provided when engine crankcase level is two inches below nominal level (Reference 10). Maintaining adequate NPSH is not a concern for EDG operation at 60.0+/-0.5 Hz.
The small variations in EDG speed and the impact on JW and LO Pump operation can also be dispositioned by EDG system performance during normal operation. At the conclusion of every EDG run, the engine operates in a cooldown cycle at 608 rpm for five minutes when an engine stop is demanded (Reference 11). During routine starts of the EDG, a slow or idle start is performed. When a slow/idle start is demanded, the EDG operates at 450 rpm for three minutes before accelerating to 600 rpm (Reference 12). Neither of these operating conditions result in JW/LO system low pressure alarms or any other adverse impact on the EDG. These EDG speeds bound the speeds considered in this RAI.

==References:==

(References are provided for Braidwood Station and the 1A EDG, which are applicable to both Braidwood and Byron Stations' EDGs)
: 1. M-152 Sheet 14, Rev. V, Manufacturers Supplemental Diagram of Diesel Generator Jacket Water Schematic Units 1 and 2
: 2. BwAR 1PL07J-1-D3, Rev. 52, Jacket Water Low Pressure
: 3. Calculation JP-95-263, Rev. 1, Verify the Adequacy of the Available Suction Head for the Engine Driven Jacket Cooling Water Pump and the Jacket Water Circulating Pump for the Emergency Diesel Generators.
: 4. WCAP-17308-NP-A, Rev. 0, Treatment of Diesel Generator (DG) Technical Specification Frequency and Voltage Tolerances
: 5. ML12300A219, Containment Accident Pressure Committee, Task 2 - Equation for Pump Speed Correction (CVDS Pump)
: 6. UFSAR Section 9.5.7.1, System Description
: 7. M-152 Sheet 9, Rev. V, Manufacturers Supplemental Diagram of Diesel Generator Lube Oil Schematic Units 1 and 2
: 8. BwAR 1PL07J-1-C5, Rev. 6, Engine Lube Oil Pressure Low
: 9. BwAR 1PL07J-1-A1, Rev. 6, Engine Lube Oil Pressure Low
: 10. BwAR 1PL07J-1-C8, Rev. 53, Engine Crankcase Level Low
: 11. BwHS 900-35, Rev. 0, Diesel Generator Governor Set-Up Following Governor Replacement
: 12. BwOP DG-11, Rev. 53, Diesel Generator Startup and Operation 3 of 10

ATTACHMENT Response to Request for Additional Information RAI EPNB-2:
For the fuel oil transfer pump, provide the (1) flow rate at 59.5 Hz, 60 Hz, and 60.5 Hz, (2) the discharge pressure at 59.5 Hz, 60 Hz, and 60.5 Hz, and (3) required net positive suction head and available net positive suction head at 59.5 Hz, 60 Hz, and 60.5 Hz.
EGC RESPONSE:
The Diesel Oil (DO) Transfer Pumps are rated at 20 gpm at a discharge pressure of 50 psig when the pump is driven at 1150 rpm (Reference 1). This represents a minimum performance rating at the design pressure of the system. Actual pumping capacity is greater than 20 gpm and discharge pressure is less than 50 psig as determined during pump Inservice Testing.
The motors for the DO Transfer Pumps are rated at 460 V with a synchronous speed of 1200 rpm. Utilizing the methodology in WCAP-17308-NP-A (Reference 2), motor speed is adjusted for an EDG operating frequency of 60.0+/-0.5 Hz and motor voltages +/-10% of rated in the following table.
DO Pump Motor             59.5 Hz/414 V             60.0 Hz/460 V          60.5 Hz/506 V Parameter Motor Speed (rpm)               1130                     1150                    1168 These speeds are used to adjust DO Transfer Pump flow and discharge pressure using the affinity laws. Adjusting the pump discharge pressure and not the pump developed pressure is conservative with respect system margin limitations (margin to relief valve setpoint). The DO Transfer Pump with the highest discharge pressure reference value at each station will be used to demonstrate the impact on pump performance. The 2B DO Transfer Pump at both stations has the highest discharge pressure reference value (References 3, 4 and 5) and the impact on pump performance is provided in the tables below.
Braidwood 2B DO               1130 rpm                 1150 rpm               1168 rpm Transfer Pump Parameter Pump Flow (gpm)                 26.6                      27.1                   27.5 Pump Discharge 29.4                      30.5                   31.5 Pressure (psig)
Byron 2B DO                1130 rpm                 1150 rpm               1168 rpm Transfer Pump Parameter Pump Flow (gpm)                 27.3                      27.8                   28.2 Pump Discharge 24.9                      25.8                   26.6 Pressure (psig)
As indicated in the tables above, DO Transfer Pump capacity is greater than the minimum performance rating of 20 gpm. At full EDG load, the fuel oil flow delivered to the engine from the day tank is less than half of the flow delivered to the day tank from the Diesel Oil Storage Tank (DOST) by a single DO Transfer Pump. Even if the pumps were performing at their 4 of 10

ATTACHMENT Response to Request for Additional Information minimum capacity of 20 gpm at 1150 rpm, the resulting flow would be 19.6 gpm at 59.5 Hz and 414 V (1130 rpm).
The NPSH analysis (Reference 6) for the DO Transfer Pumps considers minimum level in the DOST with the tank vent crimped, the pump suction strainer differential pressure at its alarm condition of 8 psid, and conservative pressure losses between the pump and the DOST with the pumps operating at 20 gpm. The pump inlet pressure under these conditions is 5.66 psia. The required pump inlet pressure in the analysis is 5 psia based on vendor nameplate data.
The only component of the calculated pump suction pressure impacted by flow are the suction line losses due to piping and pipe fittings. The pressure drop across the suction strainer is assumed to be at the maximum value associated with the alarm condition (8 psid). The analysis determined a suction line pressure loss of 0.13 psid at 20 gpm. This pressure loss is adjusted using the affinity laws.
It is conservative to not adjust the minimum required inlet pressure at lower motor/pump speeds. The minimum pump inlet pressure at higher motor/pump speeds is adjusted conservatively in a manner consistent with the affinity laws for differential pressure (Reference 7). The following table provides the calculated DO Transfer Pump inlet pressure and the required pump inlet pressure with the motor/pump operating at 1130 rpm, 1150 rpm, and 1168 rpm.
DO Pump NPSH                 1130 rpm                1150 rpm                 1168 rpm Parameter Inlet Pressure (psia)             5.67                   5.66                      5.65 Minimum Pump Suction Pressure                 5                       5                       5.16 (psia)
If the suction line pressure drop is conservatively adjusted for a bounding flow rate of 35 gpm, the resulting pressure drop is 0.4 psid and the calculated inlet pressure is 5.39 psia. Adequate pump inlet pressure remains available to support pump operation.

==References:==
: 1. SCS5110, Rev. 3, Fuel Pump Outline
: 2. WCAP-17308-NP-A, Rev. 0, Treatment of Diesel Generator (DG) Technical Specification Frequency and Voltage Tolerances
: 3. 2BwOSR 5.5.8.DO-2B, Rev. 4, Comprehensive Inservice Testing (IST) Requirements for the Diesel Fuel Oil Transfer System (B-Train)
: 4. 2BOSR 5.5.8.DO-1, Rev. 10, Unit Two Test of the Diesel Oil Transfer System
: 5. Report #P-DO-13, 2DO01PB IST Pump Evaluation Form
: 6. BRW-13-0078-M/BYR13-096, Rev. 4, External Pressure Evaluation of Diesel Fuel Oil Storage Tanks
: 7. ML12300A219, Containment Accident Pressure Committee, Task 2 - Equation for Pump Speed Correction (CVDS Pump) 5 of 10

ATTACHMENT Response to Request for Additional Information RAI EPNB-3:
Discuss whether or not any relief valves on the fuel oil transfer pump, engine driven lube oil pump, and engine driven jacket water pump discharge piping will lift due to the higher discharge pressure when the EDG is operating at 60.5 Hz.
EGC RESPONSE:
Diesel Oil (DO) Transfer Pump:
A relief valve is located on the discharge of the DO Transfer Pumps (References 1 and 2). The setpoint for this relief is 50 psig at Braidwood. The actual lift pressure may be 57 psig due to backpressure from the fuel in the relief valve tail pipe. The setpoint for the relief valve at Byron is 43 psig to compensate for the fuel oil in the relief valve tail pipe. As indicated in the response to RAI EPNB-2, the maximum expected discharge pressure is 31.5 psig for the Braidwood 2B DO Transfer Pump at 60.5 Hz. This pressure is below the relief valve setting. The maximum expected discharge pressure for the Byron 2B DO Transfer Pump is 26.6 psig at 60.5 Hz, which is below the relief valve setting. Therefore, DO Transfer Pump discharge relief valves will not lift when the EDG is operating at 60.5 Hz.
Engine Driven Lube Oil (LO) Pump:
The LO Pump has a relief valve immediately downstream of the pump (References 3 and 4).
This relief valve is set at a differential pressure of 45 psid from pump discharge to the system pressure immediately upstream of the pressure regulating relief valve. This differential pressure is a function of oil flow through the LO Cooler, LO Filter, LO Strainer, and associated system piping. A conservative estimate for the differential pressure sensed by the relief valve is 35 psid based on maximum expected values for LO Strainer (< 15 psid) and LO Filter (< 5 psid) differential pressures measured during routine EDG operation (Reference 5) with margin provided to account for LO Cooler and piping pressure losses. For EDG operation at 60.5 Hz, the maximum differential pressure will increase to 35.6 psid. Therefore, the small increase in LO Pump flow as a result of EDG operation at 60.5 Hz will not result in the LO Pump discharge relief valve lifting.
Engine Driven Jacket Water (JW) Pump:
The JW Pump does not have any relief valves downstream of the pump (Reference 6). No isolation valves exist in the system that would result in deadheading the pump. In addition, the JW Pump is a low head, high flow pump that would not over-pressurize the system in the unlikely event that it was deadheaded.
The small variations in EDG speed and the impact on JW and LO Pump operation can also be dispositioned by EDG system performance during normal operation. At the conclusion of every EDG run, the engine operates in a cooldown cycle at 608 rpm for five minutes when an engine stop is demanded. This operating condition does not result in any adverse impact on the EDG due to JW and LO pressure. The EDG speed during cooldown bounds the speed corresponding to 60.5 Hz.
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ATTACHMENT Response to Request for Additional Information

==References:==
: 1. M-50, Sheet 1A, Rev BA, Diagram of Diesel Fuel Oil Unit 1 (Braidwood)
: 2. M-50, Sheet 1A, Rev BA, Diagram of Diesel Fuel Oil Unit 1 (Byron)
: 3. M-152 Sheet 9, Rev. V, Manufacturers Supplemental Diagram of Diesel Generator Lube Oil Schematic Units 1 and 2 (Braidwood)
: 4. UFSAR 9.5.7.1, System Description
: 5. BOP DG-11T2, Rev. 17, Diesel Generator Operating Log (Byron)
: 6. M-152 Sheet 14, Rev. V, Manufacturers Supplemental Diagram of Diesel Generator Jacket Water Schematic Units 1 and 2 (Braidwood)
EEOB RAI - 1:
The licensee states in its June 26, 2020 (Agencywide Document Access and Management System (ADAMS) Accession Number ML20178A467) letter that the methodology outlined in WCAP-17308-NP-A was used to evaluate the impact of the EDG frequency and voltage variation on the performance of the affected equipment and existing safety analyses. Sections 3.1.1 and 3.1.2 of WCAP-17308-NP-A provide guidance for evaluating the impact of frequency and voltage variations, respectively, on the EDG loading, as summarized below:
Frequency: By applying the upper bound of frequency (> 60 Hz) allowed by the EDG governor to the maximum inductive loads calculated for the DG, an additional power load can be calculated for the potential variation in frequency allowed by the EDG governor operating range.
Voltage: The voltage variation of the EDG voltage regulator at steady-state operation should be confirmed to be within the allowable operating voltage range for the motors powered by the EDG. The effect of voltage variation from the nominal voltage rating of the EDG would cause the current of the motor load circuits to decrease or increase accordingly. The net change in power required by the loads on the EDG should be evaluated for lower than nominal voltage and frequency conditions, where there is a change in the power factor and real and reactive portions of the current. Since the real power is a function of the governor controls and reactive power is controlled by the EDG exciter and voltage regulator, the overall impact of EDG output voltage should be considered for real and reactive components of the EDG loading evaluation.
Regarding the evaluation of the frequency and voltage variations on the EDG, the {{letter dated|date=June 26, 2020|text=June 26, 2020, letter}} states that the licensee evaluated, in detail, the following miscellaneous loads to ensure the EDG frequency and voltage variances are acceptable:
* 125 VDC Battery Chargers
* UPS Inverters
* Required Heaters (including pressurizer heaters)
* 120 VAC Loads
* Control Room Refrigeration Units and Main Control Room chilled water (WO) pumps
* Containment Hydrogen Monitoring System Sample pumps
* Lighting
* Main Steam and Feedwater Isolation Valves 7 of 10

ATTACHMENT Response to Request for Additional Information Confirm that the evaluations for the equipment above explicitly follow the WCAP-17308-NP-A guidance. In particular, whether a) the upper bound of frequency was applied to the maximum inductive loads to calculate the frequency variation; and b) the miscellaneous loads listed above represent all applicable loads used to calculate the net change in power in evaluating the impact of frequency and voltage variations.
EGC RESPONSE:
EDG loads are evaluated for load changes as a result of variations in EDG voltage and frequency. The methodology outlined in WCAP-17308-NP-A was applied to the loads applied to the EDG. Safety Evaluation Report (SER) for WCAP-17308-NP, Revision 0, "Treatment of Diesel Generator (DG) Technical Specification Frequency and Voltage Tolerances," Section 3, Technical Evaluation, states that "Support systems such as heating, ventilation, and air conditioning systems, battery chargers and uninterruptible power supplies, not included in the TR, may also need to be evaluated separately for operation under steady state conditions with DG voltage and frequency at the extremes of allowable bands."
Therefore, the following equipment was listed separately in EGC {{letter dated|date=June 26, 2020|text=letter dated June 26, 2020}} to highlight the evaluation of the additional loads consistent with the requirements specified in the SER for WCAP-17308-NP.
* 125 VDC Battery Chargers
* UPS Inverters
* Required Heaters (including pressurizer heaters)
* 120 VAC Loads
* Control Room Refrigeration Units and Main Control Room chilled water (WO) pumps
* Containment Hydrogen Monitoring System Sample pumps
* Lighting
* Main Steam and Feedwater Isolation Valves The evaluations for the above equipment were performed on the equipment required during EDG operation for operation under steady-state conditions with DG voltage and frequency at the extremes of allowable bands.
Vendor information for the miscellaneous electrical loads was used to identify acceptable voltage and frequency ranges that allow the loads to operate and/or maintain design conditions. The vendor information was then compared to steady state running voltage and frequency variations of the EDG to determine the capability of the miscellaneous electrical loads to operate and/or maintain design conditions.
If the equipment acceptable frequency range bounds the EDG frequency variance (59.5Hz -
60.5 Hz), the equipment was considered to be capable of operation and maintaining design conditions. As it relates to EDG frequency variance on 120VAC loads, the 120VAC loads do not include major rotating equipment subject to adverse performance due to EDG frequency variances. Therefore, the effect of EDG frequency variance on 120VAC loads was considered to be negligible.
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ATTACHMENT Response to Request for Additional Information EEOB RAI-2:
The licensees {{letter dated|date=June 26, 2020|text=June 26, 2020, letter}} does not contain information describing the methodology and how the proposed tolerances for the EDG frequency and voltage are established and why these proposed tolerances are acceptable. Provide a discussion of how the proposed tolerances for the EDG frequency and voltage are established and why these tolerances are acceptable. In the response, include a summary of the performed calculation/analysis that demonstrates the proposed tolerances for the DG frequency and voltage are conservative and adequate for the worst-case voltage and frequency variations.
EGC RESPONSE:
The change in the tolerances for EDG frequency and voltage are based on issues identified by the NRC with regards to historical values approved in the Technical Specifications (TS) for EDGs. The current allowable steady-state frequency and voltage ranges for the EDGs as delineated in TS 3.8.1, "AC Sources - Operating," are:
Frequency, 58.8 to 61.2 Hz (+/- 2%)
Voltage, 3950 to 4580 Volts (-5%, +10%)
Since the EDGs are capable of operating at tighter tolerance, new analyses were performed to support the new operating tolerances. The tolerances proposed in the amendment request are bounded by the current Technical Specifications variations for EDG frequency and voltage. Since the EDGs were designed to operate within the original tolerances, limiting the tolerances to a tighter band was considered acceptable for EDG operation.
The standard operating range for offsite power distribution is +/-5% of rated voltage and +/-
0.5Hz, which is historically used as the design tolerance for AC distribution system. Further, manufacturers also use this to define the expected range of voltage used in the design of equipment. Selection of the tolerances based on industry standards simplified the analytical work since the equipment is being operated within it design requirements. For example, NEMA MG-1 uses +/-10% of motor nameplate and +/-5% rated frequency as the variation that a motor is designed to operate at. Therefore, the high limit for the EDG operating voltage was established at +5% to be consistent with the standard range of AC distribution system operating voltage. The low voltage limit was previously changed to ensure that EDG operation at minimum voltage is above the degraded voltage analytical limit established in accordance with BTP PSB-1, " Adequacy of Shutdown Electronic Distribution System Voltages," Revision 2, dated July 1981. This limit is not being changed in the license amendment request.
The EDG frequency range was reduced to minimize the impact of frequency variation on the operation of connected loads. The EDG electronic governor is capable of maintaining EDG speed to within a narrow tolerance and periodic surveillances are performed to verify proper operation of the governor using specified test equipment. However, normal EDG surveillances are performed using installed instrumentation/meters. Further, if an Operator was required to take manual control of EDG speed, the Operator would also use the available indication. Therefore, the frequency range was established based on the indications available for the EDGs.
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ATTACHMENT Response to Request for Additional Information Calculation 19-T-6 (19-T-5 for Byron), "Diesel Generator Loading During LOOP/LOCA,"
discusses the impact of EDG frequency and voltage variation on EDG connected loads.
For an EDG under frequency, the connected loads were evaluated to be within the EDG ratings.
However, an increase in EDG operating frequency will increase the synchronous speed of the connected motors by the same percent, which increases the operating shaft speed of the associated equipment. The increase in shaft speed will result in a higher motor load. By applying the upper bound of frequency allowed by the EDG governor (i.e., 60.5 Hz) to inductive loads, an additional power load can be calculated for the potential variation in frequency.
WCAP-17308-NP-A conservatively recommends that the increase in load associated with the increase in frequency be determined by cubing the percent increase in frequency above nominal. Using the methodology in the WCAP-17308-NP-A, the increase in loads for operation at 60.5 Hz (0.83% speed increase) will result in a 2.52% increase in motor load for pumps and fans ((60.5/60)3 = 1.00833). However, in order to increase shaft speed, additional torque must be developed by the motor to account for the increased load resulting from the speed increase.
In addition, for an induction motor, increasing frequency results in reduced field strength and the torque. Therefore, a load increase of 2.5% for individual motor loads is a realistic increase for operation at 60.5 Hz. Based on this, all pump and fan motor loads modeled at a specific BHP were increased 2.5% for operation at 60.5 Hz.
Voltage variation consideration is inherent to the load flow analytical software by including a voltage range. The voltage range associated with the EDGs is design input for the respective EDGs and loaded into the program as minimum source voltage. The load flow analytical software model is configured to use the minimum source voltage for all voltage and load flow calculations performed. Therefore, resultant loading is based on operation at minimum source voltage.
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