05000397/LER-2016-001

LER-2016-001, MANUAL REACTOR SCRAM FOLLOWING LOSS OF REACTOR CLOSED COOLING

Columbia Generating Station
Event date:	03-28-2016
Report date:	07-25-2016
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
Initial Reporting
ENS 51826	10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation
3972016001R01 - NRC Website

LER 16-001-00 for Columbia Regarding Manual Reactor Scram Following Loss of Reactor Closed Cooling

ML16145A332
Person / Time
Site:	Columbia
Issue date:	05/24/2016
From:	Hettel W G Energy Northwest
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GO2-16-078 LER 16-001-00
Download: ML16145A332 (5)

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Columbia Generating Station

2. DOCKET

05000 397

Plant Conditions

The reactor was at 100% power before the event. There were no structures, systems or components that malfunctioned or that were out of service that contributed to this event. One of the four reactor source range detectors failed to insert during the scram, with no impact on safety functions.

Event Description

On March 28, 2016, Operators performed a partial surveillance of the Fuel Pool Cooling (FPC) System [DA] to satisfy Post Maintenance Testing (PMT) for a Service Water (SW) [BI] to FPC isolation valve. Per PMT instructions, sections of the surveillance procedure had been marked as Not Applicable (N/A) for steps not considered necessary for the partial surveillance. The steps marked as N/A included closing Reactor Closed Cooling (RCC) [CC] isolation valves on the downstream side of the heat exchanger that isolate SW from RCC. Opening the SW valve without isolating RCC resulted in loss of pressurized RCC inventory into depressurized SW piping.

Operators recognized the loss of RCC from Control Room indications and took appropriate actions to manually scram the reactor as required by abnormal operating procedures. All plant systems responded as expected during the scram transient. The SW valve was closed after approximately 2 minutes of being opened and RCC inventory recovered quickly.

This event was reported (EN # 51826 — 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> notification) under criterion 10 CFR 50.72(b)(2)(iv)(B) — Actuation of Reactor Protection System (RPS) [JC] when the reactor is critical. The event also requires a 60-day report, or Licensee Event Report (LER), under criterion 10 CFR 50.73(a)(2)(iv)(A) as applicable to condition 50.73(a)(2)(iv)(B)(1) — An event or condition that resulted in manual or automatic actuation of the RPS system including: reactor scram or reactor trip.

Event Precursors The SW valve maintenance was originally scheduled to be performed concurrent with the quarterly surveillance of FPC. A change to the schedule moved the maintenance to after the surveillance. As a result a partial surveillance was performed. Work control reviews and pre job briefs failed to recognize the significance of some of the steps being bypassed (N/A'd) in the partial surveillance such as closing the RCC isolation valves.

Cause

The root cause was determined to be that plant Operators did not properly evaluate plant configuration when performing a partial surveillance including the marking as "N/A" (not applicable) of procedural steps, in accordance with plant's Procedure and Work Instruction Use and Adherence requirements.

26158A R3 Contributing Causes were that Work Control did not follow procedures when revising the work instructions, Technical Specification tracking log, and the work order impact statement, and that the Work Management process per the Integrated Risk Management procedure does not ensure that PMT tasks (and potentially other tasks on the same work order) are adequately evaluated for risk as stand-alone activities.

Corrective Actions

Human performance aspects of the event were immediately addressed, including coaching to the individuals involved. A Stand Down was conducted with oncoming day and night shift crews on the event, and instructions were issued requiring appropriate levels of reviews and peer checks when bypassing procedure steps for partial performance of procedures. Expectations were communicated to place keep all Notes, Cautions and Warnings in Continuous Use procedures even when steps in a section are bypassed (N/A'd).

Additional Corrective Actions include reinforcing and monitoring procedure standards, updating work control procedures, and revising the Integrated Risk Management procedure to require evaluation of each task on a work order for risk, as well as aggregate risk of the entire work order, and document this evaluation in a summary on the impact statement.

Previous Occurrences

Previous occurrences or events where improper application of N/A to work documents was a contributing factor to a plant event were investigated. There were no noteworthy examples where the improper use of N/A required issuance of an LER.

Assessment of Safety Consequences

This event resulted in a reactor trip and associated loss of generation. The loss of RCC resulted in the loss of cooling to several components, including Reactor Recirculation Pumps, the Non- Regenerative Heat Exchanger, and Drywell Cooling. There were no adverse effects to those systems due to the temporary loss of cooling. There were no undesired radiological or industrial safety aspects resulting from this event. This event did not challenge the ability of Columbia Generating Station to safely shutdown, and all plant systems responded as designed.

Energy Industry Identification System Information Energy Industry Identification System information codes from IEEE Standards 805-1984 and 803- 1983 are represented in brackets as [X] and [)0(] throughout the body of the narrative.

26158A R3