SBK-L-14225, Response to Request for Additional Information Re License Amendment Request 14-02 on Proposed Change to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement

Response to Request for Additional Information Re License Amendment Request 14-02 on Proposed Change to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement

ML15015A012
Person / Time
Site:	Seabrook
Issue date:	01/09/2015
From:	Dean Curtland NextEra Energy Seabrook
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
SBK-L-14225
Download: ML15015A012 (9)

Text

NExTera ENERGY 0 SEAROO January 9, 2015 10 CFR 50.90 SBK-L- 14225 Docket No. 50-443 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Seabrook Station Response to Request for Additional Information Regarding License Amendment Request 14-02 Proposed Change to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement

References:

1. NextEra Energy Seabrook letter SBK-L- 14126, "License Amendment Request 14-02 Proposed Change to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement," dated July 24, 2014 (ML14209A918).

2. NRC letter, "Request for Additional Information Regarding License Amendment Request to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement (TAC No. MF4578)," dated November 24, 2014 (ML14324A637).

In Reference 1, NextEra Energy Seabrook, LLC (NextEra) requested, in part, to revise Technical Specification (TS) 3.8.1.1, "A.C. Sources - Operating," to increase the voltage limit for a full load rejection test of the emergency diesel generator specified in TS surveillance requirement (SR) 4.8.1.1.2.f.3.

In Reference 2, the NRC requested additional information (RAI) in order to complete its review of the license amendment request. of this letter provides the responses to NRC RAIs 1 and 2. Attachment 2 contains the single line diagrams requested by NRC RAI 3.

This letter contains no new regulatory commitments.

NBoee NextEra Energy Seabrook, LLC, P.O. Box 300, Lafayette Road, Seabrook, NH 03874

'U.S. Nuclear Regulatory Commission SBK-L- 14225/Page 2 If you have any questions regarding this report, please contact Mr. Michael Ossing, Licensing Manager, at (603) 773-7512.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on January  ? ,2015.

Sincerely, NextEra Energy Seabrook, LLC Dean Curtland Site Vice President Attachments cc: NRC Region I Administrator J.G. Lamb, NRC Project Manager, Project Directorate 1-2 NRC Senior Resident Inspector Mr. Perry Plummer Director Homeland Security and Emergency Management New Hampshire Department of Safety Division of Homeland Security and Emergency Management Bureau of Emergency Management 33 Hazen Drive Concord, NH 03305 Mr. John Giarrusso, Jr., Nuclear Preparedness Manager The Commonwealth of Massachusetts Emergency Management Agency 400 Worcester Road Framingham, MA 01702-5399

Attachment 1 to SBK-L-14225 Response to NRC RAIs Regarding License Amendment Request 14-02 Proposed Change to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement

Response to NRC RAIs Regarding License Amendment Request 14-02 Proposed Change to Increase Voltage Limit for Diesel Generator Load Rejection Surveillance Requirement NRC RAI No. 1.

On page 1 of the license amendment request (LAR), the licensee states: "When an EDG

[emergency diesel generator] is operated in parallel with the grid for the purpose of the full load rejection test, the emergency bus voltage is further increased as excitation is adjusted to meet the required VAR [volt-ampere reactive] loading."

Please provide the value of the required VAR loading considered for the full load rejection test and the basis for that value. Since the overvoltage limit is also dependent on the VAR loading, please explain why the VAR loading is not considered as part of SR 4.8.1.1.2.f.3.

NextEra Response There is no Technical Specification requirement for a specific VAR loading associated with the EDG full load rejection. The existing TS overvoltage limit of 4784V was not based on any specific VAR loading requirement. The existing VAR loading requirement for the full load rejection test as described in station procedure OX1426.34, "Diesel Generator IA 18 Month Operability Surveillance," is 3900 kVAR (3700 - 4100 kVAR range). Section 1.2.24 of OX1426.34 describes the basis for this value. OX1426.32, "Diesel Generator lB 18 Month Operability Surveillance," contains the same requirement.

OX1426.34 (OX1426.32) Section 1.2.24 states:

NRC IN 91-13 identified a concern with EDG tests not using adequate kW and kVAR loading. Seabrook's review of IN 91-13 is documented in Yankee Memo SBP-91-580, dated 10/16/91. The memo included a recommendation to increase the kVAR loading used during the tests when the EDG was paralleled with offsite power. The memo also indicated that it was acceptable to continue testing if the specified kVAR loading could not be achieved as long as an evaluation was performed to determine whether the limitation was because of grid conditions (high voltage) or was a problem with the EDG excitation system. The EDG T.S. Background Document (Memo CEM-98-061, dated 2/19/98) identified that the procedure steps, which accepted a kVAR loading less than the limits, also specify that an evaluation be performed to verify that the kVAR limitation is due to grid conditions and not problems with the voltage regulator. For this evaluation an observation that grid & bus voltages are higher than normal, that EDG VARS can be raised and lowered indicating VAR control, and no abnormal EDG operating parameters that could indicate a voltage regulator problem will be utilized.

The referenced "TS Background document" further describes that the selected VAR loading verifies that the EDG surveillance is performed at a power factor that represents the design load as determined in the EDG loading calculation.

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The Tech Spec Bases 3/4.8.1 state:

Note that although no power factor requirements are established by SR 4.8.1.1.2a.6), the EDG is normally operated at a power factor between 0.8 lagging and 1.0. The 0.8 value is the design rating of the machine, while the 1.0 is an operational limitation to ensure circulating currents are minimized. The load band is provided to avoid routine overloading of the EDG. Routine overloading may result in more frequent tear down inspections in accordance with vendor recommendations in order to maintain EDG OPERABILITY. Similarly, though not stated in footnote ****, momentary kVAR transients above the limit do not invalidate the test.

Per UFSAR 8.1, Seabrook islicensed to IEEE 387-77 and RG 1.9 Rev. 2. Previous reviews by the station have concluded that Seabrook EDG surveillance testing meets these requirements.

NRC RAI No. 2.

On pages 2 and 3 of the LAR, the licensee states: "NextEra evaluated why previous voltage excursions on April 24, 2005 and December 7, 2005, on EDG-IB did not affect its ability to perform its safety function of providing backup power to the emergency bus. The subject voltage excursions lasted approximately 4.7 minutes and 5.3 minutes. The evaluation concluded that a voltage of about 6000 volts, although undesirable, will not damage the generator or exciter components."

Please provide the peak voltages experienced during the previous voltage excursions on EDG-1B on April 24, 2004, and December 7, 2005, and explain the reasons for these voltage excursions.

NextEra Response Engineering Evaluation EE-05-021 addresses the April 24, 2005 and December 7, 2005 voltage excursions on DG-IB.

April 24, 2005 event: MCB voltage indicator went off scale at about 5200V. The exact upper value was indeterminate due to instrument limitations.

Per AR170423 (CR 05-05540), the Apparent Cause Evaluation and Engineering Evaluation EE-05-022 identified a rectifier chassis SCR failure as the most probable cause for the voltage excursion..

December 7, 2005 event: MCB voltage indicator went off scale at about 5331V. The exact upper value was indeterminate due to instrument limitations.

Per AR88835 (CR 05-14748), the Apparent Cause Evaluation identified a degraded voltage regulator gate firing circuit board as the apparent cause.

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NRC RAI No. 3.

Please provide a copy of the single line diagram showing the connection of one of the EDGs to an emergency bus and associated protections (protective relays, etc.) provided for the EDG.

NextEra Response See Attachment 2 for drawing 1-NHY-310007, 4160V Switchgear Bus 1-E5 One Line Diagram.

This drawing shows Bus-E5 and DG-1A, See Attachment 2 for drawing 1-NHY-3 10010, Sh. 1, Diesel Generator DG-1A and DG-1B One Line Diagram, for DG-1A protective relays.

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Attachment 2 to SBK-L-14225 Drawing 1-NHY-310007, 4160V Switchgear Bus 1-E5 One Line Diagram Drawing 1-NHY-310010, Sh. 1, Diesel Generator DG-1A and DG-1B One Line Diagram DG-1A protective relays