ML080520372

Response to Request for Additional Information on the Proposed Amendment for Degraded Voltage Setpoints, Proposed Change Number (PCN) 574

ML080520372
Person / Time
Site:	San Onofre
Issue date:	02/19/2008
From:	Ridenoure R Southern California Edison Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC MD4419, TAC MD4420
Download: ML080520372 (4)

Text

Ross T. Ridenoure VP and Site Manager JSOUTHERN EDISON' CALIFORNIA An EDISON INTERNATIONAL* Company San Onofre Nuclear Generating Station February 19, 2008 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Docket Nos. 50-361 and 50-362 Response to Request for Additional Information on the Proposed Amendment for Degraded Voltage Setpoints, Proposed Change Number (PCN) 574 (TAC Nos. MD4419 and MD4420)

San Onofre Nuclear Generating Station, Units 2 and 3

Reference:

February 8, 2007 letter from B. Katz (SCE) to Document Control Desk (NRC),

Subject:

San Onofre Nuclear Generating Station Units 2 and 3, Docket Nos. 50-361 and 50-362, Proposed Change Number (PCN)-574, Degraded Voltage Setpoints

Dear Sir or Madam:

By letter dated February 8, 2007 Southern California Edison (SCE) submitted the referenced Proposed Change Number (PCN)-574, Degraded Voltage Setpoints. In a telephone conversation on January 8, 2008, NRC staff requested additional information regarding the submittal. The NRC staff questions and the SCE responses are contained in the enclosure.

The only commitment contained herein is to the action stated in the response to NRC Question 2 in the enclosure.

If you have any questions or require additional information, please contact Ms. Linda T.

Conklin at (949) 368-9443.

Sincerely,

Enclosure:

As Stated Mail Drop D45 P.O. Box 128 San Clemente, CA 92672 949-368-6255 PAX 86255 Fax: 949-368-6183 Ross.Ridenoure@sce.com

Document Control Desk February 19, 2008 cc: E. E. Collins, Regional Administrator, NRC Region IV N. Kalyanam, NRC Project Manager, San Onofre Units 2 and 3 C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 and 3 S. Y. Hsu, California Department of Public Health, Radiological Health Branch

ENCLOSURE NRC QUESTION I

a. Please explain why you have assumed an undervoltage relay drift of 0.45% in setpoint calculation E4C-130 ECN A47480, compared to the 0.1% approved by the NRC in 2005. This is a significant increase when the total loop uncertainty (TLU) is 0.7%.

b. In calculation E4C-130 ECN A47480 you stated that after six months of operation with the new relay settings, you will evaluate the As-Left and As-Found values to determine the correct drift. Please document the details of field testing experience for selecting 0.45% drift.

SCE RESPONSE The change in the assumed undervoltage relay drift from 0.1% to 0.45% is based on a drift analysis performed using more than 80 data points taken at intervals ranging from one to eight months. Details are provided in SCE document "ABBN27 Relay Drift Report."

NRC QUESTION 2 The licensee's plant procedures should meet the requirements specified in Notes I and 2 of the September 7, 2005 NRC letter to the Nuclear Energy Institute Setpoint Methods Task Force, including the clarifications provided in Section 4 of the letter.

SCE RESPONSE SCE commits to the following:

If the as-found relay setpoint is conservative with respect to the Allowable Value but outside its predefined as-found acceptance criteria band, then the relay shall be evaluated to verify that it is functioning as required before returning the relay to service.

If the as-found relay setpoint is not conservative with respect to the Allowable Value, the relay shall be declared inoperable.

The relay setpoint shall be reset to a value that is within the as-left tolerance of the nominal relay setpoint; otherwise, the relay shall be declared inoperable.

If the as-found trip setpoint (TSP) is found to be non-conservative with respect to the allowable value (AV) specified in the Technical Specifications (TSs), the relay shall be declared inoperable and the associated TS action statement followed.

If the as-found TSP is found to be conservative with respect to the AV, and outside the as-found predefined acceptance criteria band, but SCE is able to determine that the relay is functioning as required and can be reset to within the setting tolerance of the limiting TSP, or a value more conservative than the limiting TSP, then the relay may be Page 1 of 2

considered operable. If it cannot be determined that the relay is functioning as required, it shall be declared inoperable and the associated TS actions followed.

If the as-found TSP is outside the as-found predefined acceptance criteria band, the condition shall be entered into the corrective action program for further evaluation.

NRC QUESTION 3 Please confirm that the calculation results and recommendations are designed to minimize the occurrence of a class 1E bus transfer from off-site power to the emergency diesel generator when adequate grid voltage is available.

SCE RESPONSE SCE confirms that the results and recommendations of SCE calculation E4C-1 30 are designed to minimize the occurrence of a class 1 E bus transfer from off-site power to the emergency diesel generator when adequate grid voltage is available.

NRC QUESTION 4 Please provide the basis for the setting tolerance of + 0.05 Vac for adjusting the undervoltage relay setpoint.

SCE RESPONSE The setting tolerance of + 0.05 Vac is based on plant experience with these relays.

NRC QUESTION 5 Please confirm that the redesign work on the 120 volt AC systems referred to in your February 8, 2007 license amendment request is complete.

SCE RESPONSE The redesign work on the 120 volt AC systems referenced in our February 8, 2007 submittal was to:

"Increase 120 VAC power feeder size to 120 VAC panel 2L541 from MCC Panel 2Q039 by replacing the feeder cable from #12 AWG to #8 AWG for reducing voltage drop in the feeder circuit."

This work has been completed under Engineering Change Package 060401140-96.

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