ML20101H307
| ML20101H307 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 03/26/2020 |
| From: | Denise Wilson Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 20-089 | |
| Download: ML20101H307 (3) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 March 26, 2020 VIRGINIA ELECTRIC AND POWER COMPANY SURRY.POWER STATION UNITS 1 AND 2 ANNUALCHANGES, TESTS, AND EXPERIMENTS REPORT REGULATORY COMMITMENT EVALUATION REPORT
Dear Sir or Madam,
Serial No.
SPS/SCN:
Docket Nos.
License Nos.20-089 RO 50-280 50-281 DPR-32 DPR-37 Virginia Electric and Power Company hereby submits the annual report of Changes, Tests, and Experiments pursuant to 10 CFR 50.59(d)(2) implemented at Surry Power Station. The Attachment provides the descriptions and summaries of the Regulatory Evaluations and the Regulatory Commitment Change Evaluation completed in 2019.
Should you have any questions regarding this report, please contact Stephen C. Newman at (757) 365-3397.
Very truly yo~.k
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. J ! VJ-:----
David H. Wilson Director Nuclear Safety & Licensing Surry Power Station Attachment Commitments made in this letter: None cc:
United States Nuclear Regulatory Commission, Region II Marquis One Tower, Suite 1200 245 Peachtree Center Avenue, NE Atlanta, Georgia 30303-1257 NBC Senjor Resident Inspector Surry Power.Station
Attachment Surry Units 1 & 2 Serial No.20-089 10 CFR 50.59 Annual Report Page 2 of 3 10 CFR 50.59 Changes, Tests, and Experiments, and Regulatory Commitment Evaluations for 2019
- 1. SPSO-EVAL-2017-0007 Regulatory Evaluation 08/22/2019
==
Description:==
The existing Surry Power Station (SPS) Units 1 and 2 Screenwell Transformers 1 G and 2G are original plant equipment and are reaching the end of their dependable service life.
This activity will replace the existing Screenwells with new transformers manufactured by GE Prolec. Components that support Screenwell Transformer operation, including load tap changers, transformer monitoring equipment, breakers, new control cabling, and secondary connections will also be replaced. An evaluation is required because the use of microprocessor based Screenwell On-Load Tap Changers (OL TCs) to replace existing analog devices introduces the potential for a software or firmware common mode failure.
This failure could adversely affect the supply of power from Screenwell Transformers 1 G and 2G which are power sources to the station's 4160V and 480V 'G' buses..The remaining changes discussed above were screened in accordance with 10 CFR 50.59 and determined not to be adverse.
Summary:
The evaluation determined the following:
Potential failures of the new digital OL TCs may result in loss of offsite power or in.correct voltages, either high or low, to the associated 'G' buses. These failure modes for the Screenwell Transformers (and the associated equipment) remain unchanged. The new equipment, while digital, has been fully tested, analyzed, and designed to support the application at SPS. The new digital devices have programmable settings that will be documented. In addition to the settings, the software (firmware) of these devices will be documented and controlled. The equipment is of proven reliability and environmentally suited to the expected conditions. Therefore, the frequency of occurrence of an accident previously evaluated in the UFSAR is not more than minimally increased. Similarly, the proposed activity will not result in more than a minimal increase in the likelihood of occurrence of a malfunction of an SSC important to safety previously evaluated in the UFSAR.
The SPS accident analysis is bounding for the loss of offsite power, including the Screenwells under all analyzed accident conditions. As such, the failure of a Screenwell transformer to supply power to mitigate accident consequences is not credited. Similarly, where the worst-case accident condition assumes that offsite power remains available, the consequences of the accident analyses remain bounding. Though the potential failure causes (software or firmware related) are potentially different, the associated failure modes of the load tap changers are not different from their analog equivalents. Thus, the resultant
Serial No.20-089 10 CFR 50.59 Annual Report Page 3 of 3 consequences of those failures remain unchanged. Therefore, the consequences of an accident or the malfunction of an SSC important to safety previously evaluated in the SAR are not changed. Likewise, since no failure modes are changed, no new accident initiators are created, and an accident of a different type will not be created nor will a failure of an SSC important to safety result.
The Screenwell transformers are non-safety related and do not provide a power source for any Safety-Related equipment. In the event of a loss of power from the Screenwell Transformers, the Emergency Diesel Driven Service Water pumps at the Low-Level Pump House will be started and provide make up inventory to the intake canal and will assure there is enough inventory to safely perform plant shutdown activities.
The accident analyses assume either the coincident loss of offsite power, or that it remains available, whichever case is more bounding. Since the Screenwell transformers are not credited for accident mitigation, no fission product barrier limits will be exceeded or altered, and this activity does not include a method of operation.
All evaluation questions are answered NO or are not applicable. Therefore, it has been determined that this modification may be implemented without prior NRC approval.
- 2. Commitment Change Evaluations There were no Commitment Change Evaluations approved in 2019.