ML18338A106
| ML18338A106 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/22/2018 |
| From: | Mladen F Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 18-420 | |
| Download: ML18338A106 (3) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 NOV 2 2 2018 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555-0001 VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNIT 2 Serial No.:
18-420 SPS: TSC RO Docket No.: 50-281 30-DAY SPECIAL REPORT FOR AN RCS PRESSURE TRANSIENT In accordance with the Surry Power Station Technical Specifications (TS), Section 3.1.G.3, this Special Report is submitted in order to document a Unit 2 Reactor Coolant System (RCS) pressure transient.
TS 3.1.G.3 requires submittal of a special report to the Nuclear Regulatory Commission within 30 days if the Reactor Coolant System Overpressure Mitigation System is used to mitigate a RCS pressure transient. The report shall describe the circumstances initiating the transient, the effect of the mitigation system or administrative controls on the transient, and any corrective actions necessary to prevent recurrence.
Circumstances Initiating the Transient On October 28, 2018, at approximately 03:10 hours, with Unit 2 at Cold Shutdown, water solid RCS plant operation, Control Room operators observed an unplanned rise in RCS pressure. A pressurizer Power Operated Relief Valve (PORV) opened on a high pressure signal in order to limit the RCS pressure rise. Just prior to the pressure increase, the reactor operator at the controls was attempting to adjust level in the volume control tank, and mistakenly reduced letdown flow causing the rise in RCS pressure. The Operations team responded by adjusting charging and letdown flow to restore normal RCS pressure.
The volume control tank divert valve and the letdown pressure control valve controllers look similar and are separated on the Main Control Room bench board by less than six inches. Due to inadequate self-check and lack of peer review, the operator adjusted the wrong valve controller.
This event was entered into the Surry Power Station Corrective Action Program (CR1108816, Over Pressure Mitigation System (OPMS) actuated during water solid plant operations).
Effect of the Mitigation System.
Serial No.18-420 Special Report Unit 2 Pressure Transient Page 2 of 3 Engineering performed an evaluation of plant data (minimum temperature, peak pressure, cooldown rate, etc.) recorded at the time of PORV actuation to assess impact of thermal and pressure stresses on design piping stress analyses. Also, a review was performed to determine if the RCS pressure at the reactor vessel (RV) beltline remained within the pressure / temperature limits set forth by 1 OCFR50 Appendix G and ASME Code Section XI Appendix G.
The maximum RCS pressure allowed by Tech Spec Figure 3.1-2 under event conditions (RCS cooldown rate of conservatively 20 degrees F/ hour at 145 degrees F) is 490.65 psig. Review of plant data indicates that during the pressure transient, the peak RCS pressure was 397.4 psig.
Based upon the evaluation, it is concluded that there is no impact on the structural integrity of the RV and RCS resulting from the increase in RCS pressure. The mitigation system (Pressurizer PORV) operated as designed to maintain RCS pressure within the Technical Specifications acceptable operation range. Therefore, the 1 OCFR50 Appendix G limits were not exceeded.
Corrective Actions The following actions will be taken in order to prevent recurrence:
Water solid RCS controllers will be made distinct from other controllers by adding covers and placards to prevent inadvertent operation during water solid RCS conditions. These controls will be specified by procedure.
Water solid RCS operating procedures will be modified to direct Infrequently Conducted or Complex Evolution (ICCE) controls for the entire period of water solid plant operations.
ICCE controls ensure management oversight, require additional emphasis on nuclear safety, include enhanced briefing and training for operators designated with explicit command and control duties, and specify ICCE termination criteria.
An attachment will be added to water solid RCS operating procedures that will clarify specific controls required to maintain water solid RCS parameters.
Additional direction and approval for other plant activities that could impact solid plant operations will be added to water solid RCS operating procedures.
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Serial No.18-420 Special Report Unit 2 Pressure Transient Page 3 of 3 This report has been approved by the Facility Safety Review Committee.
Commitments contained in this letter: None cc:
U. S. Nuclear Regulatory Commission Region II Marquis One Tower Very truly yours, Fred Mladen Site Vice President Surry Power Station 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 NRG Senior Resident Inspector Surry Power Station