L-PI-12-028, License Amendment Request (LAR) to Revise Technical Specification (TS) 3.8.1, AC Sources - Operating Emergency Diesel Generator Voltage Limits

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License Amendment Request (LAR) to Revise Technical Specification (TS) 3.8.1, AC Sources - Operating Emergency Diesel Generator Voltage Limits
ML12137A825
Person / Time
Site: Prairie Island  Xcel Energy icon.png
Issue date: 05/15/2012
From: Schimmel M
Northern States Power Co, Xcel Energy
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
L-PI-12-028
Download: ML12137A825 (28)
v • d • e


Text

MAY 1 5 2012 L-PI-12-028 10 CFR 50.90 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 License Amendment Request (LAR) to Revise Technical Specification (TS) 3.8.1, "AC Sources - Operating" Emergency Diesel Generator Voltage Limits Pursuant to 10 CFR 50.90, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), hereby requests an amendment to the TS for the Prairie Island Nuclear Generating Plant (PINGP), Units 1 and 2, to revise the lower steady state voltage limit in TS 3.8.1 Surveillance Requirements (SR) 3.8.1.2, 3.8.1.6 and 3.8.1.9, and revise the 5 10 second voltage in SR 3.8.1.6. NSPM evaluated the proposed changes in accordance with 10 CFR 50.92 and concluded that they involve no significant hazards consideration.

The enclosure to this letter, "Evaluation of the Proposed Changes" contains the licensee's evaluation of the proposed changes.

NSPM requests approval of this LAR within one calendar year of the submittal date.

Upon NRC approval, NSPM requests 90 days to implement the associated changes. In accordance with 10 CFR 50.91, NSPM is notifying the State of Minnesota of this LAR by transmitting a copy of this letter and enclosure to the designated State Official.

If there are any questions or if additional information is needed, please contact Mr. Dale Vincent, P.E., at 651-388-1121.

1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1 121

Document Control Desk Page 2 Summary of Commitments This letter contains no new commitments and no revisions to existing commitments I declare under penalty of perjury that the foregoing is true and correct.

6 c7/spz Mark A. Schimmel Site Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (1) cc: Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC State of Minnesota

ENCLOSURE Evaluation of the Proposed Changes License Amendment Request (LAR) to Revise Technical Specification (TS) 3.8.1, "AC Sources - Operating" Emergency Diesel Generator Voltage Limits

1.

SUMMARY

DESCRIPTION

2. DETAILED DESCRIPTION 2.1 Proposed Changes

2.2 Background

3. TECHNICAL EVALUATION
4. REGULATORY SAFETY ANALYSIS 4.1 Applicable Regulatory Requirementsicriteria 4.2 Precedent 4.3 Significant Hazards Consideration 4.4 Conclusions
5. ENVIRONMENTAL CONSIDERATION
6. REFERENCES ATTACHMENTS:
1. Technical Specification Pages (Markup)
2. Technical Specification Bases Pages (Markup)
3. Technical Specification Pages (Retyped)

Page 1 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit

1.

SUMMARY

DESCRIPTION This evaluation supports a request to amend Renewed Operating Licenses DPR-42 and DRP-60 for Prairie Island Nuclear Generating Plant (PINGP), Units 1 and 2, respectively.

Pursuant to 10 CFR 50.90, Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, hereby requests an amendment to the TS for PINGP, Units Iand 2, to revise Surveillance Requirements (SRs) in TS 3.8.1. This LAR proposes to increase the lower steady state voltage limit in SRs 3.8.1.2, 3.8.1.6 and 3.8. I.9 from 3740 VAC to 4027 VAC, and revise the 5 I 0 second voltage in SR 3.8.1.6 from 3740 VAC to 4027 VAC.

Currently EDG lower voltages in TS 3.8.1 which were identified as non-conservative are administratively controlled under the provisions of NRC Administrative Letter 98-10, "Dispositioning of Technical Specifications That Are Insufficient to Assure Plant Safety",

(Agencywide Documents Access and Management System (ADAMS) Accession No. ML031110108) to assure that plant safety is maintained. This LAR is submitted in accordance with the guidance of Administrative Letter 98-10.

NSPM has also identified that the EDG frequency limits specified in SRs 3.8.1.2, 3.8.1.6 and 3.8.1.9 require revision. Currently EDG frequencies in TS 3.8.1 are also administratively controlled under the provisions of Administrative Letter 98-10.

Changes to these TS frequency limits will be proposed in a separate LAR.

2. DETAILED DESCRIPTION 2.1 Proposed Changes A brief description of the associated proposed TS changes is provided below along with a discussion of the justification for each change. The specific wording changes to the TS are provided in Attachments 1 and 3 to this enclosure.

TS 3.8.1, "AC Sources - Operating", SR 3.8.1.2, SR 3.8.1.6 and SR 3.8.1.9:

This LAR proposes to increase the steady state lower voltage limit in each of these SRs (SR 3.8.1.6 paragraph b and SR 3.8.1.9 paragraph c.) from 3740 VAC to 4027 VAC. This LAR also proposes to increase the 5 10 second voltage in SR 3.8.1.6 paragraph a from 3740 VAC to 4027 VAC. These changes are acceptable because increasing the lower voltage at which the emergency diesel generators (EDGs) supply power will assure that the supplied equipment has adequate voltage to perform its required function.

Page 2 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit Although Bases changes are not a part of this LAR, Attachment 2 to this enclosure includes marked up Bases pages for information. The changes proposed in are directly related to the changes proposed to TS 3.8.1.

In summary these changes are acceptable because they assure the plant is operated in a safe manner.

2.2 Background NRC Information Notice (IN) 2007-09, "Equipment Operability Under Degraded Voltage Conditions," identified a nuclear power facility at which the EDG surveillance test procedure specified minimum required EDG voltage, based on TS requirements, was below the calculated minimum voltage required for component operability. The PINGP corrective action concluded that the Technical Specification minimum voltage value at steady state for the EDG was non-conservative to the lower limit of 3944 VAC identified in TS section 3.3.4, "4 kV Safeguards Bus Voltage Instrumentation". EDG voltage that is too low will not be sufficient to satisfy EDG safeguards loads. Low voltage conditions could also cause an increase in motor current which may cause some motor loads to trip on overcurrent. Thus, NSPM has determined that a similar condition may exist at PINGP which is considered a non-conservative TS under the guidance of NRC Administrative Letter 98-10 (ML031110108). Subsequent to issuance of IN 2007-09, NSPM has participated in nuclear industry initiatives for generic resolution of this issue. Pursuant to NRC Staff guidance, NSPM submits this LAR independent of the ongoing industry initiatives.

Administrative Letter 98-10 (ML031110108) provides guidance for correction of facility TS when they are found to contain non-conservative values. The NRC staff expressed their expectation in Administrative Letter 98-10 that, following imposition of administrative controls, an amendment to the TS will be submitted in a timely fashion.

NSPM has imposed administrative controls on the plant operations which require verification that EDG steady state output voltage is greater than 4027 VAC.

During development of this LAR, NSPM determined that for consistency, the SR 3.8.1.6.a voltage value should also be revised to 4027 VAC. The purpose of this test requirement is to demonstrate the capability of the EDG to quickly start and operate at a voltage and frequency which will support equipment operation. This issue has been entered into the NSPM Corrective Action Program (CAP) for determination if this is a non-conservative TS.

(Note that this document refers to 4kV buses which are actually 4160 VAC: these terms may be used interchangeably.)

With the TS changes proposed in this LAR the plant will continue to operate safely and the health and welfare of the public is protected.

Enclosure NSPM Revise TS 3.8.1 Voltage Limit

3. TECHNICAL EVALUATION PINGP is a two unit plant located on the right bank of the Mississippi River approximately 6 miles northwest of the city of Red Wing, Minnesota. The facility is owned and operated by Northern States Power Company, a Minnesota corporation (NSPM). Each unit at PINGP employs a two-loop pressurized water reactor designed and supplied by Westinghouse Electric Corporation. The initial PINGP application for a Construction Permit and Operating License was submitted to the Atomic Energy Commission (AEC) in April 1967. The Final Safety Analysis Report (FSAR) was submitted for application of an Operating License in January 1971. Unit 1 began commercial operation in December 1973 and Unit 2 began commercial operation in December 1974.

The PINGP was designed and constructed to comply with the licensee's understanding of the intent of the AEC General Design Criteria (GDC) for Nuclear Power Plant Construction Permits, as proposed on July 10, 1967. PINGP was not licensed to NUREG-0800, "Standard Review Plan (SRP)" and was not part of the NRC Systematic Evaluation Program (SEP).

EDG Description Unit 1 EDGs The Unit 1 EDGs, D l and 02, are Fairbanks-Morse opposed piston EDGs which provide onsite standby power sources for 4 kV safeguards buses 15 and 16. These EDGs are each rated at 2750 kW continuous (8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br /> basis), 0.8 power factor, 900 rpm, 4160 VAC, three phase, 60 Hertz, synchronous generators. The 1,000 hour0 days <br />0 hours <br />0 weeks <br />0 months <br /> rating of each EDG is 3000 kilowatts. The 30 minute rating of each unit is 3250 kW maximum. D l and D2 were sized and preoperational tested in accordance with the guidance of Safety Guide 9.

Unit 2 EDGs The Unit 2 EDGs, 05 and D6, consist of two tandem-drive units (gensets) manufactured by Societe Alsacienne de Constructions Mecaniques de Mulhouse (SACM) which provide onsite standby power sources for 4 kV safeguards buses 25 and

26. These EDGs are each rated at 5400 kW continuous (8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br /> basis), 0.8 power factor, 1200 rpm, 4160 VAC, 3-phase, 60 Hertz. Each engine is a SACM UD45 V-16, four-cycle diesel engine, that is, the 5400 kW generator is driven by two V-16 engines which share the load with a common electronic governor system. Subsequent to purchase of 0 5 and D6 for use at PINGP, Wartsila bought SACM; thus, the engine vendor is now known as Wartsila SACM. D5 and D6 meet the design and acceptance testing requirements of Regulatory Guide (RG) 1.9, Revision 2, except portions of the 1984 Edition of IEEE 387 were implemented in the factory testing instead of the 1977 revision.

Page 4 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit Degraded Voltage Response With degraded voltage on any of the four safeguards 4160 VAC buses, the associated Programmable Logic Controller (PLC) based load sequencer automatically initiates the following steps after a 60 second delay:

a. Auto start the EDG and trip the offsite source breakers to the bus.
b. Load rejection of the designated loads on the bus.
c. Close the breaker to the EDG once it has met established voltage and frequency criteria (within 10 seconds of receiving start signal).
d. Load restoration by sequencing loads at 5 second intervals.

If a safety injection (SI) signal is received during the 60 second degraded voltage time delay, the above logic is immediately actuated by the load sequencer with SI loads added during the last step, item d.

Current TS Requirements, Basis and Limitations The original plant TS did not contain requirements for verification that the EDG output voltage was within a specific range. These test requirements were first introduced into the TS for monthly (SR 3.8.1.2) and six month (SR 3.8.1.6) tests by license amendments (LA) 91 and 84 for Units 1 and 2, respectively (LA-91/84) (ML022210226),

which approved an LAR submitted March 17, 1986. These original test requirements (SRs) required verification that the generator output voltage is at 4160 2 420 VAC (nominal voltage 5 ten percent). Neither the LAR, nor the safety evaluation (SE) for LA-91/84 specifically addressed the basis for the new surveillance test requirements to verify generator output voltage. The LAR Determination of Significant Hazards Considerations discussion stated:

The proposed changes to the surveillance requirements, while less restrictive than the existing requirements, conform to recent NRC Staff guidance provided in Generic Letter 84-15 and North Anna License Amendment Safety Evaluation Report dated April 25, 1985.

Model TS were provided in Generic Letter (GL) 84-15 which included verification that the generator voltage is at 4160 5 420 VAC. However, the thrust of both referenced documents (GL 84-15 and the North Anna LA) was improved EDG reliability and they do not discuss the basis for including these new tests in the TS or the basis for the voltage range. Additionally, no insight on the basis for the voltage verification and the range is provided in the NRC SE for LA-91/84 (ML022210226) which stated, "In order to reflect the guidance of GL 84-15, the licensee proposes to modify TS 4.6.A.l .el TS 4.6.A.l .f and TS 4.6.An3.(b)and add a new section TS 4.6.A.2, which establishes the testing requirements for the six month interval."

Enclosure NSPM Revise TS 3.8.1 Voltage Limit PlNGP was modified in 1992 to power the Unit 1 safeguards buses from EDGs D l and D2 and power the Unit 2 safeguards buses from newly installed EDGs 0 5 and D6. LA-103196 (ML022240504) revised the TS to include provisions for testing D5 and D6 and also revised the requirements for the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test as follows:

Specification 4.6.A.3.c is revised to add 18-month full load carrying capacity tests of each EDG for an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of which 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> are at a load equal to 105 -1 10 percent of the continuous rating of an EDG and 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> are at a load equal to 90 -100 percent of the continuous rating. During this test, the voltage and frequency are to be verified to be 4160 5 420 volts and 60 5 1.2 Hertz. This revision is acceptable.

Prior to conversion to improved TS (ITS), the TS required a monthly EDG test to, "Verify the generator voltage and frequency can be adjusted to 41605420 volts and 6051.2 Hz", and a six month test to, "Verify the diesel generator starts and achieves generator voltage and frequency of 4160920 volts and 6021.2 Hz with 10 seconds after the start signal."

Current TS 3.8.1 SR 3.8.1.2, SR 3.8.1.6.b, and SR 3.8.1-9.c require verification that the EDGs achieve "steady state voltage 2 3740 V and 14580 V", and SR 3.8.1.6.a requires verification that the EDGs achieve "In ( 10 seconds, voltage 2 3740 V during performance of these tests. These requirements were incorporated into the TS in their current form with the TS conversion to improved TS (ITS) by LA-1581149 (ML022070613) which followed the format and content guidance of NUREG-1431, "Improved Standard Technical Specifications, Westinghouse Plants". This LA did not make any substantive changes to the surveillance test technical requirements for verification of EDG output voltage.

Operation of the EDGs at voltages which are too low could cause increased motor current which may cause some motor loads to trip on over current.

Proposed Changes This LAR proposes to revise TS 3.8.1 SR 3.8.1-2, SR 3.8.1.6.b, and SR 3.8.1.9.c by increasing the lower voltage limit of the acceptable range from 3740 VAC to 4027 VAC, and increase the < 10 second voltage in SR 3.8.1.6 paragraph a from 3740 VAC to 4027 VAC.

SR 3.8.1.2 will state:

Verify each DG [diesel generator] starts from standby conditions and achieves steady state voltage 14027 V and 5 4580 V, and frequency 2 58.8 Hz and

< 61.2 Hz.

Page 6 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit SR 3.8.1.6 will state:

Verify each DG starts from standby condition and achieves:

a. In 5 10 seconds, voltage 14027 V and frequency 5 58.8 Hz; and
b. Steady state voltage > 4027 V and 5 4580 V, and frequency > 58.8 Hz and

< 61.2 Hz.

SR 3.8.1.9 will state:

Verify each DG operates for > 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s:

a. For > 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> loaded:

Unit 1 > 2832 kW, and

< 3000 kW Unit 2 > 5400 kW, and

< 5940 kW; and

b. For the remaining hours of the test loaded:

Unit 1 > 2500 kW, and Unit 2 > 4860 kW; and

c. Achieves steady state voltage, 4027 V and 5 4580 V; and frequency > 58.8 Hz and 5 61.2 Hz.

Technical Basis for Change The proposed TS 3.8.1 lower limit of 4027 VAC (96.8% of 4160 V) for SR 3.8.1.2, SR 3.8.1.6 and SR 3.8.1.9 was chosen based on the design of the load sequencer at the PINGP. A ready to load relay (RTLR) permissive is provided to the EDGs. Once voltage (set at 95% for pickup) and frequency setpoints for the EDG have been satisfied, load restoration can occur. The criterion for continued load sequencing for the EDGs is that a degraded voltage condition is not present as identified in the load sequencer technical manual. The degraded voltage relay (DVR) dropout value is currently set at 95.4% but can be between 94.8% and 96.2% of 4160 VAC as discussed in Section 8.3.3 of the PINGP Updated Safety Analysis Report (USAR). The DVR reset value is 0.6% above the DVR dropout value. Once the DVR reset value is reached, a degraded voltage condition is not present. The proposed PS 3.8.1 lower limit of 4027 VAC for the EDGs is equivalent to the upper value of the DVR dropout range plus 0.6% (96.8%). At this voltage level, the DVR relay will reset (degraded voltage condition not present) and will permit the EDGs to continue to accept loads Page 7 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit based on the load sequencer design while supplying adequate voltage to the connected loads. This voltage value of 4027 VAC is also above the voltage value of 4002 VAC (96.2% of 4160 VAC) for the upper degraded voltage limit at the 4160 VAC safeguards buses per T.S. SR 3.3.4.3.

The 5 10 second voltage value for SR 3.8.1.6 of 4027 VAC was selected to be consistent with the steady state voltage value of 4027 VAC.

As discussed in Section 8 of the USAR:

The analysis results were used to establish operating guidelines which guarantee a minimum 4160V safeguards bus voltage of 94.8% to allow long term operation on offsite power without actuating degraded voltage protection relays (set at 95.5 k .7%). Testing and analysis (Reference 19 [degraded voltage calculation]) have shown that all safeguards loads will operate properly at or above the minimum degraded voltage setpoint.

TS Allowable Value and lnstrument Uncertainty The analytical limit (AL) for safeguards equipment operability which supports the allowable value (AV) of 94.8% is 94.5% at the 4160 VAC buses. This AL is used in the electrical calculations identified in the following discussions to demonstrate adequate voltage. lnstrument uncertainties for the degraded voltage relays at the safeguards 4160 VAC buses were included in the AL per the plant setpoint calculation. lnstrument uncertainties for the DVR dropout took into consideration potential transformer (PT) accuracy, relay accuracy, relay setting tolerance and test equipment performance. The "Square Root of the Sum of the Squares (SRSS)" methodology was used to combine uncertainty terms to determine total loop uncertainty per the setpoint methodology used at PINGP. The setpoint calculation shows that the AV for the degraded voltage relay setpoint is 94.7% of 4160 VAC. This value bounds the DVR dropout range of 95.5%

+ .7% identified in Section 8 of the PINGP USAR and TS SR 3.3.4.3 (Degraded voltage AV ,3944 and 5 4002 VAC). The degraded voltage relay settings are based on this setpoint calculation. These degraded voltage relays monitor safeguards 4kV bus voltage and are used in the EDG load shedding and load restoration scheme. The reset values for these DVR relays are 0.6% above the dropout values. The actual plant setting for the DVR dropout is 95.4% of 4160 VAC. Therefore, actual plant setting for the DVR reset would occur at 96.0%. However, the DVR dropout range identified in the

+

setpoint calculation and PINGP USAR section 8.3.3 is 95.5 0.7% (94.8% to 96.2%).

With an upper limit of 96.2% as the DVR dropout value, the DVR reset value would be 96.8% (4027 VAC). Once the DVR is reset, a degraded voltage condition is not present. The proposed TS minimum voltage value of 4027 VAC will allow continued sequencing of safeguards loads onto the EDGs by providing adequate voltage to clear a degraded voltage condition.

Enclosure NSPM Revise TS 3.8.1 Voltage Limit Degraded Voltage Calculation The electrical distribution system for voltages 4KV and under at PlNGP is modeled using Electrical Transient Analysis Program (ETAP) software. Safeguards equipment performance is analyzed in accordance with an electrical calculation which models the PlNGP electrical distribution system voltages 4KV and under using ETAP. A degraded voltage study case was generated along with numerous plant configurations per the calculation. The configurations include degraded voltage (94.5% of 4160V: 3931 VAC) at the 4kV safeguards bus while Unit 1 and Unit 2 are at normal conditions or experiencing a combination of events (such as hot shutdown or loss of coolant accident (LOCA)). Acceptance criterion is largely based on voltage being greater than 90% at the loads. The degraded voltage calculation concluded that safeguards equipment will continue to operate when the safeguards 4160 VAC buses degraded to 94.5% of 4160 VAC (3931 VAC). Therefore, this analysis supports the lower degraded voltage value of 3944 VAC (TS SR 3.3.4.3) at the 4KV buses and also bounds the proposed TS value of 96.8% (4027 VAC) at the 4160 VAC buses.

Motor operated valve (MOV) performance is also evaluated for the degraded voltage condition. Voltage at the motor control centers (MCCs) identified in the degraded voltage calculation provides the MCC voltage input to the PlNGP MOV calculations.

During degraded voltage conditions, the MOV calculations demonstrate acceptable performance.

Protective Relaying Calculations Calculations were performed to analyze protective relay settings based on safeguards motors experiencing a reduced voltage of 75% of their rated motor voltage. Reduced voltage of 75% of rated voltage is below the lower limit for EDG voltage at steady state value of 4027 VAC. These analyses, performed using ETAP, demonstrated that the protective relay settings were appropriately selected and configured to account for a reduced voltage of 75% rated motor voltage and to verify that the overcurrent devices for the motors will not trip while running at 75% of rated voltage. The values in the calculations bound the proposed EDG TS lower limit of 4027 VAC.

Emergency Diesel Generator Loading Calculations EDG loading calculations during a loss of offsite power (LOOP) with an SI event at PlNGP were reviewed. The calculations used equipment nameplate values for the loads and would not be impacted by the lower limit EDG voltage at a steady state value of 4027 VAC. The EDG loading calculations show that the ratings of the EDGs are adequate for supplying the safeguards loads.

The results of these calculations demonstrate that the proposed degraded voltage limit will ensure that safeguards loads supplied by the safeguards buses will perform their design safety functions. In the event that offsite power becomes unavailable, the emergency diesels will supply power to the 4160 VAC buses. The lower voltage limit of

Enclosure NSPM Revise TS 3.8.1 Voltage Limit 4027 VAC from the EDGs ensure that voltage requirements at the 4160 VAC buses are met and the analytical limit of 94.5% at the 4160 VAC buses is preserved as demonstrated by the PlNGP degraded voltage calculation.

EDG loading during a station blackout (SBO) event has also been considered. The EDGs (Dl, D2, D5, D6) have been sized appropriately to carry the required loads under the SBO rule of 10CFR 50.63 and the related guidance of RG 1.155.

Emergency Diesel Generator Testing The EDGs are tested monthly in a slow start with a fast start every six months to verify that the EDGs can come up to speed with the appropriate voltages and frequencies in accordance with TS and procedural requirements. The test procedures formerly specified the steady state lower limit voltage of 3740 VAC for the EDGs to be consistent with SRs 3.8.1-2, 3.8.1.6 and 3.8.1.9 values of 3740 VAC. When the issue of EDG lower voltage was identified, administrative limits of 3944 VAC for the lower steady state voltage were established. More recently with the development of this LAR, administrative limits of 4027 VAC have been required. Reviews of surveillances performed in the past five years show that the steady state output voltage has been greater than 4027 VAC for each EDG.

The EDGs are also tested under loading conditions for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> every 18 months.

Verifications for adequate output voltage are made during these surveillance tests.

Administrative limits of 4027 VAC have also been placed in these surveillance procedures in lieu of the TS SR 3.8.1.9 value of 3740 VAC. Review of the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> test surveillances performed since this voltage value has been recorded show that the EDG voltage has remained higher than 4027 VAC during these tests.

Each refueling outage, the loads are stripped from the safeguard buses and loaded onto the EDGs during the integrated SI test. The intent of this test is to verify that safeguard loads are stripped and then are sequenced onto the EDGs as designed.

EDG steady state voltage data retrieved from the PlNGP Emergency Response Computer System (ERCS) show that EDG voltage levels have been greater than 4027 VAC.

Based on the results of surveillance procedures, the EDGs are able to maintain steady state voltages above 4027 VAC. Administrative limits have been placed to ensure that the minimum voltage at the 4kV buses when supplied by the EDGs is 4027 VAC.

Summary The following table summarizes the percentage of nominal voltage (4160 VAC) and actual voltage used in documents, calculations and testing. As discussed above, the calculations demonstrated that the affected equipment (such as, pump motors, motor operated valves and protective relays) operates as required at the analysis values given in the table. The proposed TS test value is bounded by the analyses values. Review of Page 10 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit EDG test results confirmed that the EDG maintains the output voltage above the TS value.

% nominal Description Voltage Voltage Current TS SR 3.8.1.2, SR 3.8.1.6, SR 3.8.1.9 90 3740 Current procedure administrative limits 96.8 4027 Proposed TS SR 3.8.1.2, SR 3.8.1.6, SR 3.8.1.9 96.8 4027 Degraded voltage relay calculation - analytical limit 94.5 3931 Degraded voltage relay calculation - analytical limit 94.7 3940 with uncertainties (allowable value)

Safeguards loads degraded voltage operability 94.5 3931 calculation Motor operated valve degraded voltage operability 94.5 3931 calculation Protective relaying calculations for motors 75* 3000 Observed EDG steady state output voltage during >96.8 >4027 surveillance testing

  • - % of rated motor voltage (4000 VAC)

Conclusions This LAR proposes to revise the TS EDG surveillance testing by increasing the lower steady state voltage limit to 4027 V in TS SR 3.8.1-2, SR 3.8.1.6 and SR 3.8.1.9, and revise the 5 10 second voltage in SR 3.8.1.6 to 4027 VAC. This proposed lower voltage limit is more restrictive than the current limit and is consistent with TS SR 3.3.4.3.b. Analyses have been performed which demonstrate that the safeguards loads which are supplied power by the EDGs will perform their safety functions when the safeguards 4 KV bus voltages are 3931 VAC which bounds the proposed TS value of 4027 VAC. The proposed TS lower voltage value of 4027 VAC is also above the upper degraded voltage limit of 4002 VAC (including the reset) which will allow the EDGs to accept loads during sequencing. The EDGs have demonstrated their capability to supply steady state 4027 VAC under loaded conditions in their surveillance tests.

These proposed changes will assure that the EDGs are capable of accepting loads and supplying power at voltages which will operate the equipment supplied by the Page 11 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit safeguards buses. Operation and testing of the Prairie Island Nuclear Generating Plant with the proposed TS revisions will continue to protect the health and safety of the public.

4. REGULATORY SAFETY ANALYSIS 4.1 Applicable Requlatorv Requirementslcriteria Title 10 Code of Federal Regulations 50.36, "Technical specificationsJ1:

(c) Technical specifications will include items in the following categories:

3) Sun/eillance requirements. Surveillance requirements are requirements relating to test, calibration, or inspection to assure that the necessary quality of systems and components is maintained, that facility operation will be within safety limits, and that the limiting conditions for operation will be met.

This license amendment request proposes to increase the minimum required emergency diesel generator (EDG) output voltage in the applicable surveillance requirements. This is a more restrictive change and assures that the EDGs are capable of supplying power at voltages which will operate the equipment supplied by the safeguards buses. With these changes, the Technical Specifications will continue to assure that the necessary quality of the emergency diesel generators and their components is maintained and the limiting conditions for operation of these systems will continue to be met.

Thus with the changes proposed in this license amendment request, the requirements of Title 10 CFR 50.36 continue to be met.

General Design Criteria The construction of the Prairie Island Nuclear Generating Plant was significantly complete prior to issuance of 10 CFR 50, Appendix A, General Design Criteria. The Prairie Island Nuclear Generating Plant was designed and constructed to comply with the Atomic Energy Commission General Design Criteria as proposed on July 10, 1967 (AEC GDC) as described in the plant Updated Safety Analysis Report. AEC GDC proposed Criterion 39 provides design guidance for the operating capability of alternate power systems.

Criterion 39 - Emergency Power For Engineered Safetv Features Alternate power systems shall be provided and designed with adequate independency, redundancy, capacity, and testability to permit the functioning required of the engineered safety features. As a minimum, the onsite power Page 12 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit system and the offsite power system shall each, independently, provide this capacity assuming a failure of a single active component in each power system.

AEC GDC Criterion 39 is partially met at the Prairie Island Nuclear Generating Plant through the redundant source of onsite power from two emergency diesel generators installed at the plant for each unit. This license amendment request proposes to increase the minimum steady state EDG output voltage required to satisfy the Technical Specification surveillance requirements. These changes assure that the EDGs are capable of supplying power at voltages which will operate the equipment supplied by the safeguards buses. With these changes, the AEC GDC stated above will continue to be met when the plant is operated with the plant Technical Specifications revised as proposed. Thus with the changes proposed in this license amendment request, the requirements of AEC GDC 39 continue to be met and the plant Technical Specifications will continue to provide the basis for safe plant operation.

4.2 Precedent The NRC has reviewed and approved similar license amendments for other nuclear plants that have increased the TS lower voltage limit for EDG surveillance requirements. Specifically, a recent example is provided by a license amendment for the Catawba Nuclear Station, Units 1 and 2.

Duke Energy submitted an LAR on behalf of the Catawba Nuclear Station, Units 1 and 2 (Catawba), on May 28,2009 (ML091540013). The purpose of the Catawba LAR was:

The voltage range will be revised to minus five and plus ten percent. The revision to the voltage limits are becoming more restrictive to assure compliance with plant design bases and the way the plant is operated, thus assuring the Diesel Generators are capable of supplying power with correct voltage to the required electrical loads.

The NRC concluded in the SE (ML101370039) for this Catawba LAR:

Based on the above evaluation, the NRC staff finds that the proposed changes to the Catawba 1 and 2 TS 3.8.1 minimum-required voltage value, supported by the plant-specific calculations, provides reasonable assurance of the continued availability of the EDG to shut down the reactors and to maintain the reactors in a safe condition after an anticipated operational occurrence or a postulated event.

The specifics of the Catawba LAR differ from this LAR for PlNGP in that a difference voltage range is requested; however, the purpose and effect of the Catawba LAR are the same in that surveillance testing requirements were revised to assure the EDGs are capable of supplying power at voltages which will operate the equipment supplied by the safeguards buses. NSPM has also performed plant-specific calculations which support the use of the proposed lower steady state voltage limit.

Page 13of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit 4.3 Significant Hazards Consideration Northern States Power Company, a Minnesota corporation (NSPM) evaluated whether or not a significant hazards consideration is involved with the proposed amendment by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment,"

as discussed below:

1. Does the proposed amendment involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No This license amendment request proposes to increase the emergency diesel generator minimum voltage limits in the Technical Specification Surveillance Requirements.

The emergency diesel generators and the equipment on the safeguards buses supplied by the emergency diesel generators are not accident initiators and therefore the proposed voltage limit increases do not involve an increase in the probability of an accident.

The proposed increased emergency diesel generator surveillance test minimum voltage limits assure the emergency diesel generators are capable of providing an output voltage adequate to operate the required equipment on the safeguards buses and thus maintain the current licensing basis for accident mitigation. Thus the proposed voltage limit increases do not involve a significant increase in the consequences of an accident.

Therefore, the proposed Technical Specification changes do not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No This license amendment request proposes to increase the emergency diesel generator minimum voltage limits in the Technical Specification Surveillance Requirements.

The proposed Technical Specification changes which increase emergency diesel generator the minimum voltage limits do not change any system operations or maintenance activities. The changes do not involve physical alteration of the plant, that is, no new or different type of equipment will be installed. The Page 14 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit changes do not alter assumptions made in the safety analyses but ensures that the diesel generators are capable of operating equipment as assumed in the accident analyses. These changes do not create new failure modes or mechanisms which are not identifiable during testing and no new accident precursors are generated.

Therefore, the proposed Technical Specification changes do not create the possibility of a new or different kind of accident from any previously evaluated.

3. Does the proposed amendment involve a significant reduction in a margin of safety?

Response: No This license amendment request proposes to increase the emergency diesel generator minimum voltage limits in the Technical Specification Surveillance Requirements.

Since this license amendment proposes Technical Specification changes which increase the required minimum voltage limits, margins of safety are increased and thus no margin of safety is reduced as part of this change.

Therefore, the proposed Technical Specification changes do not involve a significant reduction in a margin of safety.

Based on the above, the Northern States Power Company, a Minnesota corporation (NSPM) concludes that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92(c) and, accordingly, a finding of "no significant hazards consideration" is justified.

4.4 Conclusions In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

5. ENVIRONMENTAL CONSIDERATION A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement. However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the Page 15 of 16

Enclosure NSPM Revise TS 3.8.1 Voltage Limit amounts of any effluent that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(~)(9).Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

6. REFERENCES None Page 16 of 16

ENCLOSURE, ATTACHMENT 1 Technical Specification Pages (Markup) 3 pages follow

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3 -8.1.1 Verify correct breaker alignment and indicated 7 days power availability for each required path.

SR 3.8.1.2 ............................ NOTES..........................

1. Performance of SR 3.8.1.6 satisfies this SR.
2. All DG starts may be preceded by an engine prelube period and followed by a warmup period prior to loading.
3. A modified DG start involving idling and gradual acceleration to synchronous speed may be used for this SR in consideration of manufacturer's recommendations. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3.8.1.6 must be met.

Verify each DG starts from standby conditions and 3 1 days achieves steady state voltage > 40273744 V and

- 4580 V, and frequency 2 5 8.8 Hz and 5 6 1.2 Hz.

Prairie Island Unit 1 - Amendment No. 43% 4%

Units 1 and 2 3.8.1-6 Unit 2 - Amendment No. 4-494-65

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.6 ............................ NOTE.................... --- ----

All DG starts may be preceded by an engine prelube period.

Verify each DG starts from standby condition and 184 days achieves:

a. In 5 10 seconds, voltage > 402737443 V and frequency 2 58.8 Hz; and
b. Steady state voltage > 4027374-0 V and

< 45 80 V, and frequency > 5 8.8 Hz and

< 61.2 Hz.

SR 3.8.1.7 Verify each DG does not trip during and following a 24 months load rejection of:

1. Unit 1 2 650 ItW; and
2. Unit 2 2 860 1tW.

SR 3.8.1.8 Verify each DG's automatic trips are bypassed on an -------NOTE------

actual or simulated safety injection signal except: SR 3.0.2 interval extension (1.25

a. Engine overspeed; times the interval) applies
b. Generator differential current; and to this SR
c. Ground fault (Unit 1 only).

24 months Prairie Island Unit 1 - Amendment No. 4-58 194 Units 1 and 2 Unit 2 - Amendment No. 4-49 4-83

AC Sources-Operating SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.9 ............................ NOTES..........................

1. Momentary transients outside the load and power factor ranges do not invalidate this test.
2. If performed with DG synchronized with offsite power, it shall be performed at a power factor

< 0.85. However, if grid conditions do not permit, the power factor limit is not required to be met. Under this condition the power factor shall be maintained as close to the limit as practicable.

Verify each DG operates for 2 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s: 24 months

a. For 2 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> loaded:

Unit 1 2 2832 ItW, and

< 3000 1tW Unit 2 2 5400 kW, and

< 5940 1tW; and

b. For the remaining hours of the test loaded:

Unit 1 2500 ltW, and Unit 2 2 4860 1tW; and

c. Achieves steady state voltage > 4 0 2 7 M V and 5 4580 V; and frequency 2 58.8 Hz and 5 61.2 Hz.

Prairie Island Unit 1 - Amendment No. 448489 1-94 Units 1 and 2 3.8.1-9 Unit2-AmendmentNo.~~

ENCLOSURE, ATTACHMENT 2 Technical Specification Bases (Markup)

B 3.8.1-16 1 page follows

AC Sources-Operating B 3.8.1 BASES SURVEILLANCE SR 3.8.1.2 and SR 3.8.1.6 REQ-(continued) These SRs help to ensure the availability of the standby electrical power supply to mitigate DBAs and transients and to maintain the unit in a safe shutdown condition.-- The steady state voltage requireineilt k to allow the DG to accefl loads and lo maintain the unit ill a safe shutdown condition, To minimize the wear on moving parts that do not get lubricated when the engine is not running, these SRs are modified by a Note (Note 2 for SR 3.8.1.2) to indicate that all DG starts for these Surveillances may be preceded by an engine prelube period and followed by a warmup period prior to loading.

In order to reduce stress and wear on diesel engines, some manufacturers recommend a modified start in which the starting speed of DGs is limited, warmup is limited to this lower speed, and the DGs are gradually accelerated to synchronous speed prior to loading. These start procedures are the intent of Note 3, which is only applicable when such modified start procedures are recommended by the manufacturer.

SR 3.8.1.6 requires that, at a 184 day Frequency, the DG starts from standby conditions and achieves required voltage and frequency within 10 seconds. The 10 second start requirement demonstrates the capability of the DG and supports the assumptions of the design basis LOCA analysis in the USAR (Ref. 3). The 10 second voltage value was selected to be consistent with the steady state vo1ta.g.e.

Standby conditions for a DG mean that the diesel engine coolant and oil temperatures are being maintained consistent with manufacturer recoinmendations.

The 10 second start requirement is not applicable to SR 3.8.1.2 (see Note 3) when a modified start procedure as described above is used.

If a modified start is not used, the 10 second start requirement of SR 3.8.1.6 applies.

Prairie Island Unit 1 I\lme-Revision Units 1 and 2 B 3.8.1-16 Unit 2 /,;I-Revision

ENCLOSURE, ATTACHMENT 3 Technical Specification Pages (Retyped) 3 pages follow

AC Sources-Operating 3.8.1 SURVEILLANCE REOUIREMENTS SURVEILLANCE I FREQUENCY SR 3.8.1.1 Verify correct breaker alignment and indicated 7 days power availability for each required path.

SR 3.8.1.2 ............................ NOTES..........................

1. Performance of SR 3 -8.1.6 satisfies this SR.
2. All DG starts may be preceded by an engine prelube period and followed by a warmup period prior to loading.
3. A modified DG start involving idling and gradual acceleration to synchronous speed may be used for this SR in consideration of manufacturer's recommendations. When modified start procedures are not used, the time, voltage, and frequency tolerances of SR 3 .8.1.6 must be met.

Verify each DG starts from standby conditions and 3 1 days achieves steady state voltage 2 4027 V and

< 4580 V, and frequency 2 58.8 Hz and 5 6 1.2 Hz.

I Prairie Island Unit 1 - Amendment No. 44-84%

Units 1 and 2 3.8.1-6 Unit 2 - Amendment No. 4-49 4-65

AC Sources-Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.6 ............................ NOTE------------------ - - --- ----

All DG starts may be preceded by an engine prelube period.

Verify each DG starts from standby condition and 184 days achieves:

a. In 5 10 seconds, voltage > 4027 V and frequency > 58.8 Hz; and
b. Steady state voltage > 4027 V and 5 4580 V, and frequency 2 58.8 Hz and 5 6 1.2 Hz.

SR 3.8.1.7 Verify each DG does not trip during and following a 24 months load rejection of:

1. Unit 1 > 650 1cW; and
2. Unit 2 2 860 1cW.

SR 3.8.1.8 Verify each DG's automatic trips are bypassed on an -------NOTE------

actual or simulated safety injection signal except: SR 3.0.2 interval extension (1 -25

a. Engine overspeed; times the interval) applies
b. Generator differential current; and to this SR
c. Ground fault (Unit 1 only).

24 months Prairie Island Unit 1 - Amendment No. 44%4-94 Units 1 and 2 3.8.1-8 Unit 2 - Amendment No. 44-9443

AC Sources-Operating SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.9 ............................ NOTES..........................

1. Momentary transients outside the load and power factor ranges do not invalidate this test.
2. If performed with DG synchronized with offsite power, it shall be performed at a power factor

< 0.85. However, if grid conditions do not permit, the power factor limit is not required to be met. Under this condition the power factor shall be maintained as close to the limit as practicable.

VerifL each DG operates for 2 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s: 24 months

a. For 2 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> loaded:

Unit 1 2 2832 ltW, and

-< 3000 kW Unit 2 2 5400 ItW, and

-< 5940 1tW; and

b. For the remaining hours of the test loaded:

Unit 1 2 2500 kW, and Unit 2 2 4860 kW; and

c. Achieves steady state voltage 2 4027 V and 1.4 5 80 V; and frequency 2 58.8 Hz and 5 61.2 Hz.

Prairie Island Unit 1 - Amendment No. 4-89 -194 Units 1 and 2 3.8.1-9 Unit 2 - Amendment No. 4-78 34S

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