NEI 99-04, Sequoyah Units 1 & 2, Commitment Summary Report

Sequoyah Units 1 & 2, Commitment Summary Report

ML101460115
Person / Time
Site:	Sequoyah
Issue date:	05/21/2010
From:	Krich R M Tennessee Valley Authority
To:	Document Control Desk, Office of New Reactors
References
NEI 99-04
Download: ML101460115 (3)

Text

Tennessee Valley Authority 1101 Market Street, LP 3R Chattanooga, Tennessee 37402-2801 R. M. Krich Vice President Nuclear Licensing May 21, 2010 10 CFR 50.4 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Units 1 and 2 Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 50-328

Subject:

Commitment Summary Report The purpose of this letter is to provide the Sequoyah Nuclear Plant Commitment Summary Report for the period of October 1, 2008 to December 31, 2009, as required by the NRC endorsed Nuclear Energy Institute's "Guidelines for Managing NRC Commitment Changes" (NEI 99-04). This enclosed report summarizes docketed commitments that TVA has evaluated and revised using administrative controls that incorporate the guidelines.

If you have any questions, please contact Beth A Wetzel at (423) 843-7170 or J. W. Proffitt at (423) 843-6651.Respectfully, R. M. Krich

Enclosure:

Commitment Summary Report cc (Enclosure):

NRC Regional Administrator

-Region II NRC Senior Resident Inspector

-Sequoyah Nuclear Plant printed on recycled paper ENCLOSURE SEQUOYAH NUCLEAR PLANT COMMITMENT

SUMMARY

REPORT COMMITMENT

SUMMARY

REPORT Basis/Justification for Change: An evaluation of each of the below listed commitments was performed in accordance with NEI 99-04. The evaluation determined that each of the items are no longer commitments based on a modification to the feedwater control system. Implementation of Digital Feedwater Control replaces the analog/digital module that originally performed the MSS function.

The original analog/digital module provided no alarm/monitor function to observe its performance and as a result required periodic testing.Digital Feedwater Control System checks the quality of the instrument signal inputs and if all are of a good quality, the median signal is then selected for control. Should one of the signal inputs fail, the remaining signals are then averaged to provide the control function and an alarm is generated.

The inputs to Digital Feedwater Control system for MSS are redundant so a single failure of an input module would be detected and alarmed. Also, the processors are redundant.

Each processor stores its program internally and both processors continually monitor their redundant processor to check for errors. If a processing error is detected, that processor is automatically taken off line and the redundant processor assumes the lead. A system alarm is generated to allow prompt diagnostics and repair. Since the software is stored internally to the processor, a software failure in that processor will not cause a software failure in the redundant processor.

Performance of manual surveillance testing would require redundant signals to be removed from service which would increase the risk of a transient if additional equipment were to fail during the surveillance.

The Digital Feedwater Control System was installed on Sequoyah Nuclear Plant (SQN), Unit 2 during the last refueling outage (U2C16 Refueling Outage) and will be installed on SQN, Unit 1 during its next refueling outage (U1C17 Refueling Outage) schedule to begin in October 2010. The quarterly channel function test of the Median Signal Selector will continue to be performed on SQN, Unit 1 until the digital feedwater control system is installed on that unit.Therefore, these commitments are no longer valid. Because these commitments were initiated as a result of a safety evaluation report decision, they have been tabulated in the commitment summary report for NRC notification.

Commitment Commitment Source............mmary of Origina Summary of Evluation

1. Tracking # Document Commitment............Commitment Chanaes 22-01 NCO900054001 TVA letter to The steam generator level channel functional test procedure will be and NRC dated revised to ensure that the median signal selector (MSS) module is Decommit NC0900054002 April 11, 1990 functionally tested on a quarterly basis.E-1