05000269/LER-2013-002

LER-2013-002, LPI and RBS Trains Inoperable When 1LP-21 Was Closed Due To Human Error

Oconee Nuclear Station, Unit 1
Event date:	06-26-2013
Report date:	08-26-2013
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
2692013002R00 - NRC Website

10. POWER LEVEL

100%

NAME

Bob Meixell, Oconee Regulatory Affairs TELEPHONE NUMBER (Include Area Code) (864) 873-3279

TO EPIX

A BP 1LP-21 P305 Yes 14. SUPPLEMENTAL REPORT EXPECTED 15. EXPECTED

MONTH DAY YEAR

• YES (If yes, complete Item 15) @ NO DATE 16. ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On June 26, 2013, Oconee Unit 1 was operating at 100% power in Mode 1 with the 1B train Low Pressure Injection (LPI) and Reactor Building Spray (RBS) out of service for scheduled maintenance and testing. Maintenance was performing Motor Operated Valve (MOV) testing on 1LP-22, which is the 1B train LPI and RBS pump suction valve from the Borated Water Storage Tank (BWST). With 1B train of LPI and RBS already declared inoperable, a licensed operator inadvertently closed 1LP-21 (the 1A train LPI and RBS pump suction valve), rendering both trains of LPI and RBS inoperable, and resulting in an unplanned Tech Spec 3.0.3 entry. The inadvertent action was immediately recognized by the licensed operator and after appropriate assessment and communication with shift personnel, the valve was reopened.

Tech Specs 3.5.3 and 3.6.5 require two trains of LPI and RBS to be operable in Mode 1. The duration of inoperability of 1A train LPI and RBS was approximately 13 minutes. This event was reported as an 8-hour notification to the NRC on June 26, 2013, in Event Notification (EN) number 49149 under 10 CFR 50.72(b)(3)(v)(A-D), "Event or Condition that Could Have Prevented Fulfillment of a Safety Function.

BACKGROUND

The following information is provided to assist readers in understanding the event described in this Licensee Event Report (LER). Applicable Energy Industry Identification [EMS] system and component codes are enclosed within brackets.

Low Pressure Injection System (LPI) The purpose of the Low Pressure Injection (LPI) [EllS: BP] system is to remove decay heat during cold shutdown and refueling operation. It also acts as a portion of the Emergency Core Cooling System (ECCS) to provide cooling water to the reactor after large and intermediate size Loss Of Coolant Accidents (LOCAs). The LPI System also supplies suction from the Reactor Building Emergency Sump (RBES) to the High Pressure Injection (HPI) [EllS: BG] system (Piggyback mode of operation) during small break LOCAs following the depletion of the Borated Water Storage Tank (BWST).

The BWST is the initial source of borated water for the LPI and the HPI pumps to inject into the Reactor Coolant System (RCS) [EllS: AB] and supplies water to the Reactor Building Spray (RBS) [EllS: BE] pumps. After the BWST is depleted, water is recirculated from the RBES by realigning a direct suction to the LPI pumps. The HPI pump suction can be supplied from the RBES by means of the LPI/HPI piggyback alignment.

The LPI System shall be capable of being automatically initiated to supply flow from the BWST to the Reactor Vessel in response to postulated LOCAs that result in rapid depressurization of the RCS. Operability of the automatic and manual initiation circuitry for the system is required by Technical Specifications.

Reactor Building Spray System (RBS) The RBS system functions to remove heat (both sensible and latent) from the containment atmosphere in accident conditions. The RBS system in conjunction with the Reactor Building Cooling (RBC) [EllS:BK] and the LPI systems is capable of removing sufficient heat from the containment atmosphere to maintain the Reactor Building post-event conditions (i.e., pressure, temperature, etc.) within design limits. The RBS System also functions to remove iodine from the post-event containment atmosphere.

The RBS system consists of two separate trains, each of which shares a suction source with a corresponding train of the LPI system.

Tech Specs 3.5.3 and 3.6.5 require two trains of LPI and RBS to be operable in Mode 1.

On June 26, 2013, both trains of LPI and RBS were inoperable for approximately 13 minutes due to a human error when a licensed operator inadvertently closed 1LP-21 instead of 1LP-22.

1LP-21 was closed. 1LP-21 is required to be in the open position to support the operability of the 1A train of LPI and RBS.

Reportability Determination NUREG 1022 "Event Report Guidelines 10 CFR 50.72 and 50.73, Section 3.2.7 "Event or Condition that Could Have Prevented Fulfillment of a Safety Function" states in part: "...a report is required when 1) there is a determination that the SSC is inoperable in a required mode or other specified condition in the TS Applicability, 2) the inoperability is due to one or more personnel errors, including procedure violations; equipment failures; inadequate maintenance; or design, analysis, fabrication, equipment qualification, construction, or procedural deficiencies, and 3) no redundant equipment in the same system was operable.

Based on the above, Oconee determined that for the approximate 13 minute period from 1040 to 1053 on June 26, 2013, this event met the 8-hour reporting requirements of 10 CFR 50.72(b)(3)(v)(A-D), and the 60-day Licensee Event Report (LER) reporting requirements of 10 CFR 50.73(a)(2)(v)(A-D) as an "Event or Condition that Could Have Prevented Fulfillment of a Safety Function.

Prior to this event Unit 1 was operating at 100% power with no safety systems or components out of service that would have contributed to this event.

EVENT DESCRIPTION

On June 26, 2013, at approximately 1040, while performing a procedure to stroke test 1LP-22 (B LPI BWST Suction) for maintenance, 1LP-21 (1A LPI BWST Suction) was inadvertently closed.

The licensed operator immediately informed the Control Room SRO (CRSRO) that the wrong component had been operated. The CRSRO notified the Operations Shift Manager (OSM) and Shift Technical Advisor (STA). The CRSRO with OSM concurrence directed 1LP-21 to be opened.

Prior to starting 1B train maintenance and testing, and prior to declaring the 1B train of LPI and RBS inoperable, protected train barriers were put in place under administrative control to protect equipment in the 1A train.

1LP-21 was closed for approximately 13 minutes.

During this event Unit 1 was in TS 3.5.3, Condition A, for 1B train LPI and was in TS 3.6.5, Condition A, for 1B train RBS due to maintenance and testing that included Motor Operated Valve (MOV) surveillance and testing, and electro/mechanical PMs being performed on 1LP-22. 1LP-22 remained in the open position during the time 1LP-21 was closed. Although 1LP-22 was open, operability of 1LP-22 could not be demonstrated while in the MOV test configuration without extensive evaluation and testing.

When 1LP-21 was closed, TS 3.0.3 was entered by direction from TS 3.6,5 and due to TS 3.5.3 not having a condition for both LPI trains being inoperable. TS 3.0.3 was exited after 1LP-21 was opened.

CAUSAL FACTORS

The inadvertent closure of 1LP-21 was determined to be human error by a licensed operator who operated a component other than the one directed by the procedure. The error occurred in the Unit 1 Control Room, with no unusual distractions occurring at the time of the event.

Extent of Condition is being addressed by incorporating this event into the action plan and proposed corrective actions in existing Problem Identification Program (PIP) 0-13-6528, which addresses a gap to excellence in Operations supervisor performance.

One root cause and one contributing cause were identified for this event.

• The root cause is that the protected train barriers that were being used were not robust enough to provide the required protection

• The contributing cause is that Operations supervision did not effectively reinforce management expectations for human performance standards including Task Preview, Correct Component Verification (CCV) and Procedure Use and Adherence (PU&A)

CORRECTIVE ACTIONS

Immediate:

• Work was stopped on 1B LPI train pending further investigation

• Qualifications were suspended for involved individuals pending further investigation

• A site stand down was performed to discuss the event

• A Human Performance Review Board was conducted to evaluate the event Subsequent:

• A Prompt Investigation Response Team (PIRT) was formed. The PIRT evaluated the event and made recommendations (Complete)

• Implementation of a supervisory oversight tool was accelerated which provides a list of expectations for the various skill sets used to ensure precise control of the plant and full compliance with the processes required to operate the plant in a safe and reliable manner (Complete)

• Increased supervisory observations utilizing the supervisory oversight tool (Complete) Planned:

• Implement a process to provide more robust protected equipment barriers to be utilized on control room components

• Conduct training on supervisor performance, focusing on the role of the supervisor in observations and driving rigorous adherence to standards potential impact to plant risk. A bounding analysis assuming the inoperability of both trains of Low Pressure Injection (LPI) and Reactor Building Spray (RBS) for 13 minutes determined the incremental conditional core damage probability (ICCDP) to be less than 1E-07. The incremental conditional large early release probability (ICLERP) was not explicitly calculated but is also very low given that the ICLERP is a subset of the ICCDP.

Considering the above, this event had a very small risk impact due to the very short time frame that both the 1A and 1B trains of LPI and RBS were inoperable.

There was no actual impact on the health and safety of the public because there was no plant event requiring LPI and RBS functions at the time, and there were no releases of radioactive materials or radiation exposures. There were no personnel injuries associated with this event.

ADDITIONAL INFORMATION

To determine if this event was recurring, a search of the Oconee Problem Identification Program (PIP) database was conducted for a time period covering three years prior to the date of this event. For those applicable events with corresponding cause codes, a review identified PIPs potentially related to mispositioned components. Further review identified three events related to unplanned Tech Spec (TS) and Selected Licensee Commitment (SLC) entry (PIPs 0-11-4747, 0-12-1488 and 0-12-6599). None of the three related events resulted in entry into LCO 3.0.3, and none were reportable to the NRC under 10 CFR 50.72 or 10 CFR 50.73.

A Licensee Event Report (LER) search for a time period covering three years prior to the date of this event identified two Oconee LERs also reported under 10 CFR 50.73(a)(2)(v)(A-D):

• LER 269/2011-05 "Reactor Protection System Overpower Flux/Flow/Imbalance Channels Inoperable" o The causal factors for the event in LER 269/2011-05 included human performance issues, but the causal factors were not sufficiently similar to the human performance issue described in this LER to be considered recurring

• LER 269/2013-01 "Inadequate HVAC Load Analysis and Design Impacts on Emergency Power Equipment" o The causal factors for the event in LER 269/2013-01 involve legacy design issues and are not similar to the event described in this LER Therefore, this event was not considered to be recurring.

This event is considered reportable under the Equipment Performance and Information Exchange (EPIX) program.