ML12184A107

Supplemental Information Needed for Acceptance of Requested Licensing Action Emergency Diesel Generator Voltage Limits Amendment Request

ML12184A107
Person / Time
Site:	Prairie Island
Issue date:	07/12/2012
From:	Thomas Wengert Plant Licensing Branch III
To:	Molden J Northern States Power Co
Wengert T
References
TAC ME8700, TAC ME8701
Download: ML12184A107 (5)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 July 12, 2012 Mr. James E. Molden Site Vice President Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota 1717 Wakonade Drive East Welch. MN 55089-9642

SUBJECT:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 SUPPLEMENTAL INFORMATION NEEDED FOR ACCEPTANCE OF REQUESTED LICENSING ACTION RE: EMERGENCY DIESEL GENERATOR VOLTAGE LIMITS AMENDMENT REQUEST (TAC NOS. ME8700 AND ME8701)

Dear Mr. Molden:

By letter dated May 15, 2012. Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, submitted a license amendment request for the Prairie Island Nuclear Generating Plant, Units 1 and 2. The proposed amendment would lower the steady state voltage limit in certain Surveillance Requirements in Technical Specification 3.8.1.

The purpose of this letter is to provide the results of the U.S. Nuclear Regulatory Commission (NRC) staff's acceptance review of this amendment request. The acceptance review was performed to determine if there is sufficient technical information in scope and depth to allow the NRC staff to complete its detailed technical review. The acceptance review is also intended to identify whether the application has any readily apparent information insufficiencies in its characterization of the regulatory requirements or the licensing basis of the plant.

Consistent with Section 50.90 of Title 10 ofthe Code of Federal Regulations (10 CFR), an amendment to the license (including the technical specifications) must fully describe the changes requested, and following as far as applicable, the form prescribed for original applications. Section 50.34 of 10 CFR addresses the content of technical information required.

This section stipulates that the submittal address the design and operating characteristics, unusual or novel design features, and principal safety considerations.

The NRC staff has reviewed your application and has concluded that additional information delineated in the enclosure to this letter is necessary to enable the staff to make an independent assessment regarding the acceptability of the proposed amendment in terms of regulatory requirements and the protection of public health and safety and the environment.

In order to make the application complete, the NRC staff requests that NSPM supplement the application to address the information requested in the enclosure by August 10, 2012. This will enable the NRC staff to begin its detailed technical review. If the information responsive to the NRC staff's request is not received by the above date, the application will not be accepted for review pursuant to 10 CFR 2.101, and the NRC will cease its review activities associated with the application. If the application is subsequently accepted for review, you will be advised of

J. Molden -2 any further information needed to support the staff's detailed technical review by separate correspondence.

The information requested and associated time frame in this letter were discussed with Mr. Dale Vincent of your staff on June 28, 2012.

If you have any questions, please contact me at (301) 415-4037.

Sincerely, Thomas J. Wengert, Senior Project Manager Plant Licensing Branch 111-1 Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306

Enclosure:

As stated cc w/encl: Distribution via Listserv

SUPPLEMENTAL INFORMATION REQUIRED FOR AMENDMENT REQUEST CONCERNING EMERGENCY DIESEL GENERATOR VOLTAGE LIMITS NORTHERN STATES POWER COMPANY - MINNESOTA PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 DOCKET NOS. 50-282 AND 50-306 By letter dated May 15, 2012 (Agencywide Documents Access and Management System Accession No. ML12137A825), Northern States Power Company, a Minnesota corporation, dOing business as Xcel Energy, submitted a license amendment request (LAR) for the Prairie Island Nuclear Generating Plant, Units 1 and 2. The proposed amendment would lower the steady state voltage limit in certain Surveillance Requirements (SRs) in Technical Specification (TS) 3.8.1, The Nuclear Regulatory Commission (NRC) staff has reviewed this request and has determined that the following supplemental information is required prior to accepting the application for review.

Background

The LAR proposes revising TS 3.8.1, "AC Sources - Operating" to change the minimum voltage acceptance criterion for the emergency diesel generator (EDG) surveillance testing for the lower steady state voltage limit in TS 3.8.1 SRs 3.8.1.2, 3.8.1.6 and 3.8.1.9, from 3740 Volts alternating current (VAC) to 4027 VAC. The LAR states that the minimum voltage limits specified in the SRs are non-conservative but are administratively controlled in an acceptable range to ensure operation of safety related equipment.

As an example, the proposed SR 3.8.1.6 would state:

Verify each DG starts from standby condition and achieves:

a. In S 10 seconds, voltage ~ 4027 V and frequency ~ 58.8 Hz; and

b. Steady state voltage ~ 4027 V and s 4580 V, and frequency ~ 58.8 Hz and s61.2Hz.

SR 3.8.1.2, SR 3.8.1.6, and SR 3.8.1.9 also have an upper voltage value and a frequency component that can affect equipment performance. The relationships among frequency, voltage, and equipment performance are such that changes to one of these parameters must be evaluated in the context of the other parameters. In addition, since the voltage and frequency requirements are specified together and include high and low limits, any changes must be evaluated within the context of the other requirements.

Supplemental Information Requested In order to understand the adequacy of all the proposed parameters in SRs 3.8.1.2, 3.8.1.6, and 3.8.1.9 for equipment operability, the NRC staff requests the following supplemental information:

Enclosure

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1. The upper end of allowable voltage for steady state operation (4580 V) is not changed.

Verify that voltage spikes observed during full load rejection testing at given power factor and initial voltage of 4580 V will not adversely impact the EDG or any other safety related equipment.

2. The typical nominal rating of equipment used in 4160 V system is 4000 V +/-10%. Verify that extended operation of the EDGs at 4580 V will not adversely impact the reliable operation of safety related equipment. Validate that protective relaying set points have been evaluated for higher load currents.

3. TS SR 3.8.1.9 has EDG load testing requirements. The torque speed curves of induction motors are dependent on system frequency. Verify that EDG testing envelopes the EDG loading at the onset of an event when the pumps may be operating at run-out conditions and during steady state conditions with the EDG operating at the allowable extremes of voltage and frequency.

4. Provide details on how the minimum frequency of ~ 58.8 Hertz (Hz) and steady state frequency values ~ 58.8 Hz and::; 61.2 Hz are used to determine safeguards equipment operational requirements during design basis accident calculations.

a) Provide details on performance capabilities of accident mitigation equipment (pumps, motors, valves, etc.) when the EDG is operating at the lower end of the allowable voltage and frequency bands during design basis events.

b) Verify that motor operated valve performance is not adversely impacted (accident analyses) at the lower end of the TS allowable frequency coupled with the frequency/voltage variations observed during the EDG loading sequence.

J. Molden - 2 any further information needed to support the staffs detailed technical review by separate correspondence.

The information requested and associated time frame in this letter were discussed with Mr. Dale Vincent of your staff on June 28, 2012.

If you have any questions, please contact me at (301) 415-4037.

Sincerely, IRAJ Thomas J. Wengert, Senior Project Manager Plant licensing Branch 111-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION:

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