05000254/LER-2021-001, Automatic Actuation of Emergency Diesel Generator Due to Transformer Maintenance
| ML21138A819 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 05/18/2021 |
| From: | Ohr K Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVP-21-029 LER 2021-001-00 | |
| Download: ML21138A819 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2542021001R00 - NRC Website | |
text
Exelon Generation SVP-21-029 May 18, 2021 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Quad Cities Nuclear Power Station, Unit 1 Renewed Facility Operating License No. DPR-29 NRC Docket No. 50-254 10 CFR 50.73
Subject:
Licensee Event Report 254/2021-001-00 "Automatic Actuation of Emergency Diesel Generator Due to Transformer Maintenance" Enclosed is Licensee Event Report 254/2021-001-00 "Automatic Actuation of Emergency Diesel Generator Due to Transformer Maintenance," for Quad Cities Nuclear Power Station, Unit 1.
This report is submitted in accordance with 10 CFR 50. 73(a)(2)(iv)(A), for any event or condition that resulted in manual or automatic actuation of any emergency AC electrical power systems.
There are no regulatory commitments contained in this letter.
Should you have any questions concerning this report, please contact Brandon Nichols at (309) 227-4833.
Kenneth S. Ohr Site Vice President Quad Cities Nuclear Power Station cc:
Regional Administrator-NRC Region Ill NRC Senior Resident Inspector-Quad Cities Nuclear Power Station
Abstract
On March 19, 2021, Unit 1 was in a refueling outage and Unit 2 was operating at 100% power with the 1/2 Emergency Diesel Generator (EDG) inoperable for planned maintenance. On March 19, 2021 at 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br />, the Operational Analysis Department (OAD) was performing Unit 1 Reserve Auxiliary Transformer (RAT) to Bus 12 relay routines when an unplanned trip of the Unit 1 RAT occurred and the Unit 1 EDG automatically started and loaded to Bus 14-1. All automatic actions occurred as expected. Unit 2 entered TS 3.8.1 Condition A for the RAT inoperability, and TS 3.8.1 Condition D due to inoperability of the 1/2 EDG and the RAT.
The cause of the Unit 1 RAT trip and auto initiation of the Unit 1 EDG was due to a human performance error.
Immediate corrective actions included the restoration of power to the Unit 1 RAT and associated electrical power buses. Follow up corrective actions include management to reinforce expectations for pre-job briefs.
This report is being submitted under 10 CFRSO. 73(a)(2)(iv)(A) for any event or condition that resulted in manual or automatic actuation of an emergency AC electrical power s stems.
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor, 2957 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) c'odes are identified in the text as (XX].
EVENT IDENTIFICATION Automatic Initiation of Emergency Diesel Generator Due to Transformer Maintenance
A. CONDITION PRIOR TO EVENT
Unit: 1 Event Date: March 19, 2021 Reactor Mode: 5 Mode Name: Refueling Event Time: 2030 Power Level: 0%
001 The 1 /2 Emergency Diesel Generator was inoperable for planned maintenance at the time of the event.
B. DESCRIPTION OF EVENT
On March 19, 2021, Unit 1e was in refueling outage Q1R26 and Unit 2 was operating at 100% power.
The 1/2 Emergency Diesel Generator (EDG)[EK] was inoperable for planned maintenance, causing Unit 2 to be in Technical Specification (TS) 3.8.1 Condition B. Off-site power to Unit 1 was being provided through the Unit 1 Reserve Auxiliary Transformer (RAT)[XFMR].
00 At 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br /> on March 19, 2021, the Operational Analysis Department (OAD) was performing Unit 1 RAT to Bus 12 (BU] relay routines when an unplanned trip of the Unit 1 RAT occurred and the Unit 1 EOG automatically started and loaded to Bus 14-1. All automatic actions occurred as expected. Unit 1 entered an abnormal operating procedure for a Loss of Offsite Power. Unit 2 entered TS 3.8.1 Condition A for the RAT inoperability, and TS 3.8.1 Condition D due to inoperability of the 1/2 EOG and the RAT.
At 2310 hours0.0267 days <br />0.642 hours <br />0.00382 weeks <br />8.78955e-4 months <br /> on March 19,2021, the Unit 1 RAT was restored to service, being available and operable to Unit 2. TS 3.8.1 Condition A and D was exited for Unit 2 at that time.
At 0350 hours0.00405 days <br />0.0972 hours <br />5.787037e-4 weeks <br />1.33175e-4 months <br /> on March 20, 2021, the 1/2 EOG was declared operable to both units and TS 3.8.1 Condition B was exited. At 0355 on March 20, 2021, an Event Notification Sheet (ENS) #55146 was submitted under 10 CFR 50. 72(b )(3)(iv)(A) for an automatic actuation of the Unit 1 EOG. This report is being submitted under 10 CFR50.73(a)(2)(iv)(A) for any event or condition that resulted in manual or automatic actuation of an emergency AC electrical power system.
- C. CAUSE OF EVENT 05000-254 YEAR 2021 SEQUENTIAL NUMBER 001 The cause of the trip of the Unit 1 RAT and automatic initiation of Unit 1 EOG was a human performance error during performance of the Unit 1 RAT to Bus 12 relay routines. Workers failed to perform an adequate pre-job brief prior to work execution and failed to perform human performance verification techniques to validate the status of the Unit 1 RAT. The OAD person assumed that the Unit 1 RAT had already been removed from service without validating the actual condition.
D. SAFETY ANALYSIS
System Design
REV NO.
00 Auxiliary power can be supplied from four separate sources: Unit 1, Unit 2, the 345KV transmission systems, and the diesel generators. Each unit has one reserve auxiliary transformer and one unit auxiliary transformer. The reserve auxiliary transformer has sufficient capacity to handle the normal auxiliary power needs (with the load divided between the unit auxiliary and reserve auxiliary transformers) of one unit and the emergency shutdown auxiliary equipment needs of the other unit.
Each of these auxiliary power supplies (such as the RAT) is available, through circuit breaker switching, to the Division I or II emergency auxiliary equipment of both units and therefore serves as a redundant offsite source of auxiliary power.
The Unit 1 RAT provides the primary source of off-site power to Unit 1 with the unit off-line, providing all required 4kV and 480V buses. The Unit 1 RAT also provides one of the sources of off-site power to Unit 2.
Safety Impact The safety significance of this event was minimal. At the time of the event, Unit 1 was in Mode 5 (refueling) with reactor head removed, reactor cavity flooded, shutdown cooling secured, and no fuel moves in progress. With the loss of the Unit 1 RAT, one qualified offsite circuit was made unavailable.
However, another qualified circuit was available, as provided by the bus ties between the corresponding Essential Service (ESS) buses of the two units. The Unit 1 EOG started per design and provided power to its' associated 4KV division. Immediate operator actions were taken to restore both the Unit 1 RAT and the 1/2 EOG to operable status. The 4kV unit cross-tie breakers were utilized to provide power to the second 4kV division.
E. CORRECTIVE ACTIONS
Immediate:
- 1. Operations restored power to the Unit 1 RAT and associated 480V [EC,ED] and 4kV [EB] buses per station procedures.
Follow up:
- 1. Management to review and reinforce expectations/requirements for pre-job briefs. This would include the development of pre-job brief work aid in the performance of briefs.
F. PREVIOUS OCCURENCES
The station events database, LERs and INPO Industry Reporting Information System (ISIS) were reviewed for similar events at Quad Cities Nuclear Power Station. This event was caused by a human performance error of inadequate pre-job brief resulting in the trip of the Unit 1 RAT and automatic initiation of the Unit 1 EDG. Based on the conditions of this event, cause and associated corrective actions, one event described below has been found to have a similar cause.
LER 254-2018-004-00 (09/26/2018) Reactor Scram due to Turbine-Generator Load Reject was found to be a similar event. The contributing cause of the reactor scram was found to be a Technical Human Performance error and pre-job briefing standards. This caused the operations crew to not correctly identify error precursors with the work to be performed.
G. COMPONENT FAILURE DATA
There were no equipment failures associated with this event. Page_4_ of _4_