05000324/LER-2016-001

LER-2016-001, Mispositioned Valves Result in Residual Heat Removal Service Water System Inoperability

Brunswick Steam Electric Plant (Bsep) Unit 2
Event date:	06-15-2016
Report date:	08-08-2016
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3242016001R00 - NRC Website

LER 16-001-00 for Brunswick Steam Electric Plant, Unit 2, Regarding Mispositioned Valves Result in Residual Heat Removal Service Water System lnoperability

ML16231A019
Person / Time
Site:	Brunswick
Issue date:	08/08/2016
From:	Gideon W R Duke Energy Progress
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 16-001-00
Download: ML16231A019 (5)

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to 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.

Brunswick Steam Electric Plant (BSEP) 001 05000-324 2016 - 000 Energy Industry Identification System (EllS) codes are identified in the text as [XX].

Background

Initial Conditions On June 15, 2016, at 05:15 Eastern Daylight Time (EDT), Unit 2 was in Mode 1 (i.e., Run mode) at 100 percent of rated thermal power. No out-of-service equipment contributed to, or affected the course of, this event.

Reportability Criteria This event is being reported in accordance with 10 CFR 50.73(a)(2)(i)(B) because Unit 2 was operated in a condition prohibited by the Technical Specifications (TS). Specifically, one division of the Residual Heat Removal (RHR) [BO] Service Water (RHRSW) [BI] system was found to be inoperable. The duration of the inoperability was based on the last successful operation of the RHRSW system, or June 4, 2016, at 14:41 EDT. TS Limiting Condition for Operation (LCO) 3.7.1 Condition B says that with one RHRSW subsystem inoperable for reasons other than Condition A (i.e., one pump inoperable), the system must be restored within 7 days or be in Mode 3 (i.e. shut down) within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The plant was operated until June 15, 2016, at 05:45 EDT in this condition (i.e., 10 days, 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />, 4 minutes).

Therefore, the plant was operated in a condition prohibited by the TS.

Event Description

On June 15, 2016, at 05:15 EDT, Unit 2 was in Mode 1 (i.e., Run mode) at 100 percent of rated thermal power. Operations personnel were preparing to start the RHRSW system in the suppression pool cooling mode. While opening Nuclear Service Water (NSW) system [BI] valves to supply RHRSW, operators received an annunciator for RHRSW pump suction pressure being low. Personnel then identified two RHRSW instrument valves which were closed and should have been open. The associated instrument lines feed pressure instruments for the suction of the "B" and "D" RHRSW pumps. With the valves closed, suction pressure from NSW could not be sensed, and the RHRSW pumps could not start. Both instrument valves were immediately opened. This restored the affected RHRSW subsystem to operable status at 05:45 EDT on June 15, 2016.

Event Causes It is most likely that the instrument valve mispositioning occurred during a previous operation of the "B" division of RHRSW on April 6, 2016. Investigators found no evidence of tampering. The RHRSW suction valves were opened on June 4, 2016, at 14:41 EDT, and the low pressure annunciator did not alarm. The absence of the low pressure alarm confirms the "B" and "D" RHRSW pumps could have started.

Therefore, the duration of inoperability is conservatively assumed to have begun on June 4, 2016, at 14:41 EDT.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to 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. I The apparent cause of this event is that procedures lacked sufficient control of the positions of the subject instrument valves. Procedures allowed operators to select which valves to manipulate under certain conditions, creating the possibility that valves might be left in the incorrect position during system restoration.

Safety Assessment The purpose of the RHRSW system is to provide a heat sink for the RHR system. It normally receives suction from the NSW system supply header and moves cooling water through the RHR heat exchangers.

The RHR heat exchangers receive flow from the RHR system. In the suppression pool cooling mode, RHR water is circulated from the suppression pool to the heat exchangers where RHRSW flow cools it.

In this event, one of two RHRSW subsystems was inoperable for a period greater than the allowable seven days. The unaffected division of RHRSW was always operable during this time. Consequently, the safety function of the RHRSW system was maintained.

Based on this analysis, this event had no adverse impact on the health and safety of the public.

Corrective Actions

Any changes to the corrective actions and schedules noted below will be made in accordance with the site's corrective action program.

• The affected instrument valves were placed in the correct position, and the RHRSW system was made operable. This action is complete.

• Procedures governing use of the affected instrument valves will be revised to specifically designate as-left positions, and valve positions will be independently verified. This action will be completed by September 16, 2016.

Previous Similar Events

A review of LERs and the site's corrective action program for the past three years did not identify any previous similar occurrences in which mispositioned components rendered a safety system inoperable.

Commitments This report contains no regulatory commitments.

4