05000280/LER-2017-001

From kanterella
Jump to: navigation, search
LER-2017-001, 1 OF 3
Surry Power Station, Unit 1
Event date: 08-09-2017
Report date: 10-11-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown

10 CFR 50.73(a)(2)(ii)

10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded
LER closed by
IR 05000280/2017004 (1 February 2018)
2802017001R00 - NRC Website
LER 17-001-00 for Surry, Unit 1, Regarding Shutdown due to an Unisolable Leak in Reactor Coolant Pressure Boundary
ML17297A457
Person / Time
Site: Surry Dominion icon.png
Issue date: 10/06/2017
From: Mladen F
Virginia Electric & Power Co (VEPCO)
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML17297A457 (4)


Reported lessons leamed are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S.

Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Surry Power Station, Unit 1 05000- 280

3. LER NUMBER

2017 001 00 1.0 DESCRIPTION OF THE EVENT On August 6, 2017 at 18:55 hours, with Unit 1 operating at 100% power, containment air particulate radiation monitor alert annunciator was received in the main control room. A Reactor Coolant System (RCS) leak rate calculation was performed and indicated that the unidentified leak rate had increased by 0.08 gallons per minute (GPM). Actions were taken to investigate and evaluate the source of leakage. On August 8, at 10:55 hours, steam was identified coming from an RCS hot leg sample system valve in an RCS loop room. At 16:32 hours, power reduction was initiated to facilitate personnel entry into the loop room to investigate and isolate the leakage. The root isolation valve was closed, however, leakage could not be verified as completely isolated. On August 9, 2017, at approximately 13:38 hours, with Unit 1 at 32% power, a through wall pressure boundary leak was identified at the inlet to a 3/8 inch RCS sample system valve (EIIS-AB-HCV). Since the source of the leakage could not be verified as drainage from the isolated tubing, Unit 1 was shut down for repairs at 16:37 hours. On August 10, 2017, additional isolation valves were closed and the sample system tubing was cut and capped on each side of the RCS sample system valve to repair the leak.

Unit 1 was returned to power operation on August 11, 2017.

A four-hour report was made to the NRC pursuant to 10 CFR 50.72(b)(2)(i) due to a plant shutdown required by Technical Specifications and an eight-hour report was made pursuant to 10 CFR 50.72(b)(3)(ii)(A) due to degradation of a principal safety barrier. This report is being made pursuant to 10 CFR 50.73(a)(2)(i)(A) and 10 CFR 50.73(a)(2)(ii) (A), as a plant shutdown required by Technical Specifications and as a condition resulting in the degradation of a principal safety barrier.

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS Technical Specification Limiting Condition for Operation (LCO) 3.1.C, RCS Operational Leakage, does not permit pressure boundary leakage through a unisolable fault in an RCS component body, pipe wall, or vessel wall. Since it could not be verified that the pressure boundary leak was completely isolated after closing the root isolation valve, Unit 1 shutdown was required due to the degradation of a principal safety barrier. Leakage was confined to small bore 3/8 inch tubing. No reactor protection actuation occurred, nor was actuation necessary. A complete rupture of this sample line would have resulted in RCS leakage within the capacity of the normal makeup system, and therefore, Emergency Core Cooling System (ECCS) actuation would not have been expected to occur. Therefore, this event is of minimal safety significance.

3.0 CAUSE OF THE EVENT An apparent cause evaluation is being conducted. The equipment that was leaking is located in a high radiation area in an RCS loop room inside containment. Therefore, component removal, failure analysis, and permanent repair will be performed during the next Unit 1 refueling outage.

4.0 IMMEDIATE CORRECTIVE ACTIONS While Unit 1 was at Hot Shutdown, additional isolation valves were closed, and the area of leakage was isolated from the RCS. The tubing was cut and capped on each side of the RCS hot leg sample system valve.

Reported lessons learned are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S.

Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, means used to impose an informa on collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person Is not required to respond to, the information collection.

Surry Power Station, Unit 1 05000- 280

3. LER NUMBER

001 00 2017 5.0 ADDITIONAL CORRECTIVE ACTIONS An American Society of Mechanical Engineers (ASME) Code repair will be completed, and the tubing and the RCS hot leg sample system valve will be restored to design specifications and functionality during the next Unit 1 refueling outage.

6.0 ACTIONS TO PREVENT RECURRENCE Corrective actions determined by the apparent cause evaluation will be implemented in accordance with the corrective action program.

7.0 SIMILAR EVENTS None 8.0 MANUFACTURER/MODEL NUMBER NUPRO SS-6UG-TN3-4C 9.0 ADDITIONAL INFORMATION Unit 2 was at 100 percent power at the time of this event and was unaffected by the Unit 1 shutdown. There were no other structures, systems, or components that were inoperable at the start of the event that contributed to the event.