05000333/LER-2020-001, Automatic Scram Due to Main Turbine Trip on High RPV Water Level

Automatic Scram Due to Main Turbine Trip on High RPV Water Level

ML20091L895
Person / Time
Site:	FitzPatrick
Issue date:	03/31/2020
From:	Pat Navin Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
JAFP-20-0025 LER 2020-001-00
Download: ML20091L895 (4)

LER-2020-001, Automatic Scram Due to Main Turbine Trip on High RPV Water Level

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function
3332020001R00 - NRC Website

text

Exelon Generation JAFP-20-0025 March 31, 2020 United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 James A. FitzPatrick NPP P.O. Box 110 Lycoming. NY 13093 Tel 315-349-6024 Fax 315-349-6480 Patrick D. Navin Site Vice President - JAF James A. FitzPatrick Nuclear Power Plant Renewed Facility Operating License No. DPR-059 NRC Docket No. 50-333

Subject:

Licensee Event Report (LEA) 2020-001 Enclosed is a Licensee Event Report concerning an automatic scram following a turbine trip on high RPV water level. In accordance with NEI 99-04, the regulatory commitment contained in this correspondence is to restore compliance with the regulations. The specific methods that have been planned to restore and maintained compliance are discussed in the LEA. If you have any questions or require additional information, please do not hesitate to contact Richard Sullivan, Regulatory Assurance Manager, at (315) 349-6562.

Sincer/tl

_/)_

Patrick D. Navin Site Vice President FitzPatrick Nuclear Power Plant TCP/RS Enclosure cc:

USNRC, Region I Administrator USNRC, Project Manager USNRC, Resident Inspector INPO Records Center (IRIS)

NRC FORM 366 (04-2018)

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (04-2018)

LICENSEE EVENT REPORT (LER)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. Facility Name James A. FitzPatrick Nuclear Power Plant

2. Docket Number 05000333

3. Page 1 OF 3

4. Title Automatic Scram due to Main Turbine Trip on High RPV Water Level

5. Event Date

6. LER Number

7. Report Date

8. Other Facilities Involved

Month

Day

Year

Year Sequential Number Rev No.

Month Day Year Facility Name N/A Docket Number N/A 01 31 2020 2020 - 001 - 00 03 31 2020 Facility Name N/A Docket Number N/A

9. Operating Mode Month Day Year Yes (If yes, complete 15. Expected Submission date) No Abstract (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On January 31, 2020, an automatic scram occurred as a result of a main turbine trip on high Reactor Pressure Vessel (RPV) water level. The plant was at reduced power in preparation for maintenance activities. When the A Reactor Feed Pump (RFP) was removed from service, the A RFP discharge check valve (34FWS-4A) failed to immediately close resulting in a rapid increase in RPV level. A high RPV level trip signal resulted in the B RFP trip and Main Turbine trip.

This event resulted in the automatic actuation of the Reactor Protection System and containment isolations in multiple systems, reportable per 10 CFR 50.73(a)(2)(iv)(A). When Secondary Containment automatically isolated, a differential pressure excursion momentarily exceeded Technical Specification limits, a condition reportable in accordance with 10 CFR 50.73(a)(2)(v)(C).

The cause of the event was determined to be due to a failure of the A RFP discharge check valve (34FWS-4A) to close.

There were no actual safety consequences as a result of this event. The B RFP was restored to service and the condensate and feedwater systems remained available for post-scram recovery.

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

(See Page 2 for required number of digits/characters for each block)

=

Background===

Unit Conditions Prior to the Event The James A. FitzPatrick Nuclear Power Plant (JAF) was in Mode 1 at approximately 38% rated thermal power to perform planned maintenance. There were no structures, systems, or components out of service that contributed to this event.

Event Description

On January 31, 2020 at approximately 0555 hours0.00642 days <br />0.154 hours <br />9.176587e-4 weeks <br />2.111775e-4 months <br />, after the operators removed the A Reactor Feed Pump (RFP) from service, the A RFP discharge check valve 34FWS-4A failed to close and B RFP started to short cycle flow back through A RFP. The feedwater control system responded to a lowering reactor water level and increased the B feedwater turbine speed to automatically maintain RPV water level.

When the 34FWS-4A, A RFP Discharge Check Valve rapidly closed, the elevated B RFP flow was redirected to the RPV resulting in a rapid increase in RPV level until the RPV Water Level - High (Level 8) condition was reached. The trip signal resulted in the B RFP trip and Main Turbine trip. The Main Turbine trip signal resulted in the Reactor Protection System (RPS) [JC] actuation and resultant Reactor Scram.

A subsequent low RPV water level resulted in a Group 2 isolation. The initiation of the RPS due to the automatic scram signal at critical power and the general containment Group 2 were reported per 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A) as ENS 54503.

In addition, when Secondary Containment was isolated with Group 2 isolation, the transitory differential pressure change exceeded Technical Specification (TS) Surveillance Requirement (SR) 3.6.4.1.1 of greater than or equal to 0.25 inches of vacuum water gauge to 0.09 inches of vacuum water gauge for approximately 4 seconds. The Secondary Containment DP did not exceed 0 inches of vacuum water gauge. The cause of the DP change during the transition phase is the difference in closure time for the RBV supply and exhaust isolation valves.

Event Analysis

34FWS-4A, A RFP Discharge Check Valve, was removed and inspected. It was identified that several sub-components were found degraded or broken. This deficiency was determined to have originated at some point prior to this event, during normal operation.

Under the current piping design, during a plant startup, makeup water to the RPV is aligned through a low flow line. This flow rate is insufficient to fully open the model DRV-B discharge check valve causing the check valve to flutter, exercising the internal valve parts. During normal power operations the main block valves are opened allowing sufficient flow.

The high water level trip of the main turbine resulted in the actuation of RPS. A low water level from the scram resulted in containment isolations in multiple systems; an event reportable per 10 CFR 50.73(a)(2)(iv)(A).

In this LER event, the transitory the secondary containment DP change exceeded SR 3.6.4.1.1 of greater than or equal to 0.25 inches of vacuum water gauge for a few seconds. When the SR is not met then TS 3.6.4.1 was not met and Secondary Containment was Inoperable; therefore, this event is also reportable per 10 CFR 50.73(a)(2)(v)(C). U.S. NUCLEAR REGULATORY COMMISSION (04-2018)

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LER NUMBER James A. FitzPatrick Nuclear Power Plant 05000 - 333 YEAR SEQUENTIAL NUMBER REV N0.

2020

- 001

- 00 Page 3 of 3 (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

There were no actual safety consequences as a result of this event. The B RFP was restored to service and the condensate and feedwater systems remained available for post-scram recovery.

Cause

The cause for the scram event was the failure of A Feed Pump discharge check valve, 34FWS-4A, resulting in reactor water level perturbation, Main Turbine trip, and automatic reactor scram.

Similar Events

LER: 1993-009-03, Low Reactor Water Level Scram Due to Feedwater Transient, JAFP-96-0072 dated February 22, 1996.

LER: 2015-006-01, Transitory Secondary Containment Differential Pressure Excursions, JAFP-16-0002, dated February 4, 2016.

FAILED COMPONENT IDENTIFICATION:

Manufacturer:

Enertech Manufacturer Model Number:

DRV-B NPRDS Manufacturer Code:

E334JA NPRDS Component Code:

CKV FitzPatrick Component ID:

34FWS-4A

Corrective Actions

The A Feed Pump discharge check valve, 34FWS-4A, was repaired. Additional corrective actions are documented in the Corrective Action Program.

References Issue Report - IR 04314313, James A. FitzPatrick Reactor Scram 1/31/20