05000315/LER-2022-003-01, Automatic Trip on Losss of Flow Due to Reactor Coolant Pump Trip
| ML23053A162 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 02/22/2023 |
| From: | Ferneau K Indiana Michigan Power Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| AEP-NRC-2023-06 LER 2022-003-01 | |
| Download: ML23053A162 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 3152022003R01 - NRC Website | |
text
INDIANA MICHIGAN POWER-An MP Company BOUNDLESS ENERG Y-February 22, 2023 Docket No.: 50-315 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 Donald C. Cook Nuclear Plant Unit 1 LICENSEE EVENT REPORT 315/2022-003-01 Indiana Michigan Power Cook Nuclear Plant One Cook Place Bridgman, Ml 49106 indianamichiganpower.com AEP-NRC-2023-06 10 CFR 50.73 Automatic Reactor Trip on Loss of Flow Due To Reactor Coolant Pump Trip In accordance with 10 CFR 50. 73, Licensee Event Report (LER) System, Indiana Michigan Power Company, the licensee for Donald C. Cook Nuclear Plant Unit 1, is submitting as an enclosure to this letter the following report:
LER 315/2022-003-01: Automatic Reactor Trip on Loss of Flow Due To Reactor Coolant Pump Trip This LER is a revision to LER 315/2022-003-00, which was previously submitted by letter dated, October 19, 2022. The enclosed LER has been revised to update the root cause of the event and the corrective actions.
There are no commitments contained in this submittal.
Should you have any questions, please contact Mr. Michael K. Scarpello, Regulatory Affairs Director, at (269) 466-2649.
Sincerely, Kelly J Ferneau Site Vice President MPH/sjh Enclosure: Licensee Event Report 315/2022-003-01: Automatic Reactor Trip on Loss of Flow Due To Reactor Coolant Pump Trip
U. S. Nuclear Regulatory Commission Page 2 c:
EGLE - RMD/RPS J.B. Giessner-NRC Region Ill M. G. Menze - AEP Ft. Wayne NRC Resident Inspector N. Quilico - MPSC R. M. Sistevaris-AEP Ft. Wayne S. P. Wall - NRC, Washington D.C.
A. J. Williamson - AEP Ft. Wayne AEP-NRC-2023-06
Enclosure to AEP-NRC-2023-06 Licensee Event Report 315/2022-003-01: Automatic Reactor Trip on Loss of Flow Due To Reactor Coolant Pump Trip
Abstract
On August 28, 2022, at 1348 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12914e-4 months <br />, the Donald C. Cook Nuclear Plant Unit 1 Reactor automatically tripped from 100 percent power, due to Reactor Coolant System Loop 3 Low Flow, caused by a trip of the Unit 1 Reactor Coolant Pump (RCP) 3.
Following the reactor trip, Unit 1 continued to be supplied by offsite power. All control rods fully inserted. The Auxiliary Feedwater Pumps started as required and operated properly, and Decay Heat Removal was through the Steam Dump System.
All required equipment operated as expected, and the trip was not complicated.
An investigation determined that Unit 1 RCP 3 tripped due to a motor differential, created by a phase-to-phase electrical fault I on the insulating spacer board at the containment penetration. The Root Cause was determined to be age related degradation of tape on the penetration terminations causing contaminants to be available to transfer to the insulating spacer The event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A), System Actuation, due to the valid actuation of the
'r Reactor Protection System and the Auxiliary f eedwater System, as a result of the automatic reactor trio.
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EVENT DESCRIPTION
Estimated burden per response to comply with this mandatory collection request: 8C hours. Reported lessons learned are incorporated into the licensing process and fee back to industry. Send comments regarding burden estimate to the FOIA, Library, an~
Information Collections Branch (T--6 A10M), U. S. Nuclear Regulatory Commission Washington, OC 20555--0001, or by email to lnfocollects.Resource@nrc.gov, and the 0MB reviewer at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW, Washington DC 20503; email: oira submisslon@omb.eop.gov. The NRC may not conduct 01 sponsor, and a person is not required to respond to, a collection of information unless the document requesting or requiring the collection displays a currently valid 0MB control number.
- 2.
DOCKET NUMBER YEAR 00315 2022
.J,LCI'(-*
SEQUENTIAL NUMBER 003
- 01 REV NO.
On August 28, 2022, at 13:48 hours, the Donald C. Cook Nuclear Plant Unit 1 Reactor automatically tripped from 100 percent power, due to Reactor Coolant System [AB] (RCS) Loop 3 Low Flow, caused by a trip of the Unit 1 Reactor Coolant Pump (RCP) 3.
Above the Power Range Neutron Flux (P-8) Interlock setpoint, which is 29 percent Rated Thermal Power (RTP),
low flow in any one RCS loop will actuate a reactor trip. This Reactor Coolant Flow - Low Trip Function ensures that protection is provided against violating the Departure from Nucleate Boiling Ratio limit, while avoiding reactor trips due to normal variations in loop flow. Therefore, the RCP 3 trip created a low flow condition, which resulted in the automatic reactor trip.
Following the reactor trip, Unit 1 continued to be supplied by offsite power. All control rods fully inserted. The Auxiliary Feedwater Pumps started as required and operated properly, and Decay Heat Removal was through the Steam Dump System. All required equipment operated as expected, and the trip was not complicated.
An investigation determined that Unit 1 RCP 3 tripped due to a motor differential, created by a phase-to-phase electrical fault on the insulating spacer board at the containment penetration. The Root Cause was determined to be age related degradation of tape on the penetration terminations causing contaminants to be available to transfer to the insulating spacer.
Event Notification 56076 was submitted in accordance with 10 CFR 50.72(b)(2)(iv)(B), RPS [JG] actuation as a four (4) hour non-emergency report, and under 10 CFR 50.72(b)(3)(iv)(A), specified system actuation of the Auxiliary Feedwater System [BA], as an eight (8) hour non-emergency report.
The event is also reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A), System Actuation, due to the valid actuation of the Reactor Protection System and the Auxiliary Feedwater System, as a result of the automatic reactor trip.
COMPONENT 1-PP-45-3, REACTOR COOLANT PUMP NO. 3
CAUSE OF THE EVENT
The direct cause of the Unit 1 RCP 3 trip was electrical tree growth on the insulating spacer board, caused by partial discharge providing a conductive path to another phase, reducing insulation integrity until a phase-to-phase fault occurred, causing an RCP Motor Differential Trip.
A Root Cause Evaluation was performed and determined the Root Cause of the Unit 1 RCP 3 trip to be age related degradation of tape on the penetration terminations causing contaminants to be available to transfer to the insulating spacer. Monitoring methods to include thermography, acoustic monitoring, and visual inspection, will continue to be used on the remaining insulating boards, which will detect any reduction in insulation properties of the board due to partial discharge until they can be replaced in the Fall 2023 Unit 1 Refueling Outage (U1 C32).
CORRECTIVE ACTIONS
Estimated burden per response to comply with this mandatory collection request: 8(
hours. Reported lessons learned are incorporated into the licensing process and fee back to industry. Send comments regarding burden estimate to the FOIA, Library, anc Information Collections Branch (T-6 A 10M), U. S. Nuclear Regulatory Commission Washington, DC 20555-0001, or by email to lnfocollects.Resource@nrc.gov, and thE 0MB reviewer at: 0MB Office of Information and Regulatory Affairs, (3150-0104), Attn Desk Officer for the Nuclear Regulatory Commission, 725 17th Street NW, Washington DC 20503; email: oira submission@omb.eop.gov. The NRC may not conduct o sponsor, and a person is not required to respond to, a collection of information unles!
the document requesting or requiring the collection displays a currently valid OME control number.
- 4.
DOCKET NUMBER J. LER,_
YEAR SEQUENTIAL 00315 NUMBER 2022 003 REV NO.
- - 01 The Unit 1 RCP 3 cable termination at the Containment penetration (1-CEP-3P7) were repaired, which included replacing the tape, hardware, and insulating spacer on the Reactor Cable Tunnel (RCT) side and replacing the tape and hardware on the annulus side. All additional Unit 1 Reactor Coolant Pump Containment Penetration Insulating Spacers and associated tape are scheduled to be replaced during the Fall 2023 Unit 1 Refueling Outage (U1 C32). All Unit 2 Reactor Coolant Pump Containment Penetration Insulating Spacers and associated tape were replaced during the Fall 2022 Refueling Outage (U2C27).
Implementation of preventative maintenance strategy to replace tape and insulating spacer for all Medium Voltage Containment penetrations on 20-year (Y20) frequency.
ASSESSMENT OF SAFETY CONSEQUENCES
NUCLEAR SAFETY All equipment operated as designed, and there was no actual or potential nuclear safety hazard resulting from the automatic reactor trip on loss of RCS flow due to Unit 1 RCP 3 trip.
INDUSTRIAL SAFETY There was no actual personnel safety hazard resulting from the automatic reactor trip on loss of RCS flow due to Unit 1 RCP 3 trip.
RADIOLOGICAL SAFETY There was no actual or potential radiological safety hazard, or radiological release, resulting from the automatic react9r trip on loss of RCS flow due to Unit 1 RCP 3 trip.
PROBABILISTIC RISK ASSESSMENT (PRA)
The safety significance of the Unit 1 RCP 3 trip can be estimated by calculating the Conditional Core Damage Probability (CCDP) and the Conditional Large Early Release Probability (CLERP) of the transient initiating event.
A PRA risk assessment was performed and determined the estimated CCDP and the estimated CLERP of this event. A comparison of the CCDP and CLERP estimates to regulatory guidance resulted in the conclusion that this event was of very low safety significance.
PREVIOUS SIMILAR EVENTS
A review of LERs for the past five years involving reactor trips was performed. None of the trips were a result of similar causes.