05000331/LER-2016-002

LER-2016-002, Unplanned RCIC Inoperability Results in Safety System Functional Failure

Duane Arnold Energy Center
Event date:	4-28-2016
Report date:	12-6-2016
Reporting criterion:	10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
3312016002R00 - NRC Website

LER 16-002-00 for Duane Arnold Energy Center Regarding Unplanned RCIC Inoperability Results in Safety Functional Failure

ML16342C568
Person / Time
Site:	Duane Arnold
Issue date:	12/06/2016
From:	Vehec T A NextEra Energy Duane Arnold
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NG-16-0226 LER 16-002-00
Download: ML16342C568 (5)

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I. Description of Event:

On April 28, 2016, at 0848, while operating at 100% power, with no structures, systems, or components inoperable that contributed to this event, Surveillance Test Procedure (STP) 3.3.6.1-28, Reactor Core Isolation Cooling (RCIC) System (System Code BN) Steam Line Flow — High Channel Functional Test was started as part of planned testing. The purpose of STP 3.3.6.1-28 is to demonstrate operability of the Steam Line High Differential Pressure (flow) isolation instruments (PDIS-2441 and PDIS-2442) of the RCIC system.

During the performance of the STP, relay blocks are installed to inhibit the RCIC turbine trip associated with the RCIC automatic isolation logic under test. Step 7.3.2, which functional checks PDIS-2442, required the installation of three relay blocks, two associated with the inboard isolation signals and one associated with the turbine trip. During the performance of subsequent steps, the RCIC turbine received an unexpected trip signal and MO-2405, RCIC Trip Throttle Valve closed and Control Room annunciator 1C04C (A- 5) RCIC MO-2045 Turbine Trip actuated at 1055. Therefore, at 1055 on April 28, 2016, unplanned Limiting Condition for Operability (LCO), LCO 3.5.3 Condition A, RCIC System Inoperable, was entered. Investigations determined that the relay block for the PDIS-2442 turbine trip signal was placed on the contacts for PDIS-2441. At 1353 on April 28, 2016, the RCIC turbine was reset and RCIC was declared available and LCO 3.5.3 was exited.

II. Assessment of Safety Consequences:

The safety significance of this event was low. During the time that RCIC was unavailable, all of the Emergency Core Cooling Systems (High Pressure Coolant Injection, Core Spray, and Low Pressure Coolant Injection) that would have initiated in response to an accident or transient were operable.

All components and systems actuated as designed due to this event.

This event resulted in a Safety System Functional Failure and a Maintenance Preventable Functional Failure under the Maintenance Rule.

III. Cause of Event:

An Apparent Cause Evaluation (ACE) was completed for this event. The ACE determined that the direct cause of the RCIC turbine trip was the incorrect installation of relay block associated with inhibiting the RCIC turbine trip associated with the RCIC automatic isolation logic under test.

Duane Arnold Energy Center The Apparent Cause of the event was a human performance error associated with verifying the correct installation location of the relay block. Specifically, the use of Concurrent Verification was not consistent with procedural requirements. Contributing to this was inadequate placekeeping.

IV. Corrective Actions:

Immediate Corrective Action At 1353 on April 28, 2016, the RCIC turbine was reset and RCIC was declared available and LCO 3.5.3 was exited.

On May 6, 2016, a Human Performance Evaluation (NUPE) for the installation of the relay block on the incorrect contacts was completed.

On May 10, 2016, a Human Performance Department Clock Reset for the Instrument and Control Maintenance (ICM) department was completed to share lessons learned.

Corrective Actions for Cause of Event The cause and contributing causes of this event were addressed by:

1. The implementation and tracking of the Management Action Response Checklist (MARC) process for the individuals involved with the installation of the relay in order to improve performance.

2. Development of Performance Focus Area for Training (PFAT) in ICM to ensure mastery of concurrent verification including proper placekeeping.

3. Development of a Dynamic Learning Activity for 'in cabinet' work to include expectations for concurrent verifications and placekeeping.

V. Additional Information:

Previous Similar Occurrences:

A review of NextEra Energy Duane Arnold Licensee Event Reports from the previous three years found no other instances of events related to unplanned inoperability of RCIC.

EIIS System and Component Codes:

BN - Reactor Core Isolation Cooling System Reporting Requirements:

This activity is being reported pursuant to the requirements of 1 OCFR50.73(a)(2)(v)(D).