05000334/LER-2017-003

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LER-2017-003, Beaver Valley Power Station Unit 1 Reactor Trip due to Turbine Trip and Automatic Initiation of the Auxiliary Feedwater System
Beaver Valley Power Station Unit Number 1
Event date: 11-07-2017
Report date: 01-04-2018
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(B), System Actuation

10 CFR 50.73(a)(2)(iv)(A), System Actuation
Initial Reporting
ENS 53056 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation
3342017003R00 - NRC Website
LER 17-003-00 for Beaver Valley, Unit 1, Regarding Reactor Trip due to Turbine Trip and Automatic Initiation of the Auxiliary Feedwater System
ML18008A063
Person / Time
Site: Beaver Valley FirstEnergy icon.png
Issue date: 01/04/2018
From: Bologna R D
FirstEnergy Nuclear Operating Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-17-374
Download: ML18008A063 (4)


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

05000- Beaver Valley Power Station Unit Number 1 334 Energy Industry Identification System (EIIS) codes identified in the text as [XX].

CONDITIONS PRIOR TO OCCURENCE

Beaver Valley Power Station Unit 1 (BV-1) was in Mode 1 at 100% Power There were no Structures, Systems, or Components (SSCs) that were inoperable at the start of the event that contributed to the event.

DESCRIPTION OF EVENT

On November 7, 2017, at 05:04 EST, BV-1 experienced an automatic Reactor Trip due to an automatic Turbine [TRB] Trip initiated by a Main Unit Generator [MG] over-current protection [51] relay [RLY] actuation. The reactor trip was without complications, with safety related equipment performing their required functions to place and maintain the plant in Mode 3.

All control rods [AA] fully inserted into the reactor core. The Auxiliary Feedwater System [BA] automatically actuated on low Steam Generator [SG] Water Level as expected, and performed as designed. The plant was stabilized in Mode 3 with the normal Main Feedwater System [SJ] in service and the Auxiliary Feedwater System properly secured. Post trip response addressed an issue with both source range detectors [JI] which had no impact on maintaining the plant in Mode 3.

CAUSE OF EVENT

The Direct Technical Cause of this event was conductive foreign material in the isophase bus duct. The foreign material was found during an inspection of the Main Unit Generator Isophase Bus [BU] Duct Cooling System. The foreign material caused an electrical ground fault which led to the generator protection trip and subsequent turbine trip and reactor trip.

High Potential (Hi-Pot) testing was performed on all three phases of the bus, confirming that the "B" phase was faulted.

In 2013, a full bus duct inspection was to be completed but the scope was changed and only a partial bus duct inspection was performed. The Root Cause was determined to be, "individuals made decisions in 2013 that allowed personnel to change the work scope, without following the process to get approval for the change in work scope".

The contributing cause was that the procedure to perform the bus duct inspections was unclear as to what constituted a "full" inspection and if such a "full" inspection was required. The lack of clarity in the procedure created a "weak barrier" and contributed to confusion on the part of the workers.

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

05000- Beaver Valley Power Station Unit Number 1 334

ANALYSIS OF EVENT

The plant risk associated with the BVPS Unit 1 reactor trip and automatic auxiliary feedwater actuation due to a turbine trip on November 7, 2017 is considered to be very low. This is based on the change in average core damage frequency derived using conditional large early release probability for this event.

This event is being reported pursuant to 10 CFR 50.73(a)(2)(iv)(A) as a condition that resulted in the automatic actuation of the Reactor Protection System (RPS) and the expected automatic actuation of the Auxiliary Feedwater System.

CORRECTIVE ACTIONS

1. The BVPS Unit 1 isophase bus ducts have been properly inspected and cleared of all foreign material. (Complete) 2. In order to preclude recurrence, the inspection procedure is being revised to clearly state the requirement to perform a full isophase bus duct inspection.

Completion of item 2 listed above is being tracked in the Corrective Action Program.

PREVIOUS SIMILAR EVENTS

A review of the previous three years identified the following similar event:

BV-1 LER 2014-001-01 "Beaver Valley Unit 1 Trip due to Main Unit Transformer Failure".

CR 2017-11134, 11215