05000237/LER-2022-001-01, Reactor Scram Due to Turbine Trip on High Reactor Water Level Caused by Feedwater Regulating Valve Failure
| ML22304A228 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/28/2022 |
| From: | Patrick Boyle Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| SVPL TR 22-0046 LER 2022-001-01 | |
| Download: ML22304A228 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 2372022001R01 - NRC Website | |
text
Constellation SVPL TR # 22-0046 October 28, 2022 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 2 Renewed Facility Operating License No. DPR-19 NRC Docket No. 50-237 Dresclen \\Juclea, Power Station 6500 \\ort11 Dresclen Roacl Morns. IL 60450 10 CFR 50.73
Subject:
Licensee Event Report 237/2022-001-01, Reactor Scram due to Turbine Trip on High Reactor Water Level caused by Feedwater Regulating Valve Failure Enclosed is Licensee Event Report 237/2022-001-01, Reactor Scram due to Turbine Trip on High Reactor Water Level caused by Feedwater Regulating Valve Failure. This report describes an event being reported in accordance with 10 CFR 50. 73(a)(2)(iv)(A) an event that resulted in automatic actuation of a system listed in paragraph 10 CFR 50. 73(a)(2)(iv)(B).
There are no regulatory commitments contained in this submittal.
Should you have any questions concerning this letter, please contact Duane Avery, Acting Regulatory Assurance Manager, at (815) 416-2804.
Patrick J. Boyle Site Vice President Dresden Nuclear Power Station
Enclosure:
Licensee Event Report 237/2022-001-01 CC:
Regional Administrator-NRC Region Ill NRC Senior Resident Inspector - Dresden Nuclear Power Station
Abstract
On July 12, 2022, at 0803 CDT, an automatic reactor protection system actuation occurred following a main turbine trip due to high reactor water level. The safety significance of this event was minimal. All control rods inserted to their full-in position. Following the reactor scram, all systems operated as expected.
The cause of high reactor water level is due to a feedwater regulating valve unexpectedly failing full-open. The root cause of the feedwater regulating valve failing full-open was due to the feedwater regulating valve pilot valve assembly not operating due to a manufacturing byproduct inside the pilot valve introduced during the manufacturing process.
Corrective actions included replacement of the respective air solenoid valve. Additional corrective actions include inspecting and certifying these incoming valves are free of foreign material. Also, the solenoid valves for the feedwater regulating valves were reclassified as single point vulnerabilities.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), an event that resulted in automatic actuation of a system listed in paragraph 10 CFR 50. 73(a)(2)(iv)(B}, specifically the reactor protection system including reactor scram.
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor, 2957 megawatts thermal rated core power Energy Industry Identification System (EIIS) codes are identified in the text as [XX].
A. CONDITIONS PRIOR TO EVENT
Unit: 2 Reactor Mode: 1 Event Date: July 12, 2022 Mode Name: Power Operation
8. DESCRIPTION OF EVENT
Event Time: 0803 CDT Power Level: 100%
SEQUENTIAL NUMBER 001 REV NO.
01 On July 12, 2022, at 0759 CDT, one of two Feedwater [JB] regulating valves (FWRV) [FCV]. which are used to control feedwater flow to the reactor vessel, unexpectedly failed to the full-open position from its initial position of 42% open, resulting in a Reactor Feedwater [SK] Pump [P] trip on low suction pressure and an automatic Reactor Recirculation [AD] runback. This condition resulted in reactor water level rising due to the inability of the Feedwater system to regulate flow.
At 0803 CDT, an automatic reactor protection system [JC] actuation occurred following a main turbine [TA] trip due to high reactor water level. Plant systems operated as expected in response to the automatic scram. All control rods [AA] inserted to their full-in position and the scram was not complicated. Reactor pressure was maintained in the normal control band. Reactor water level was restored and maintained in the normal control band.
The NRC was notified via ENS 55988 at 1147 EDT.
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A), an event that resulted in automatic actuation of a system listed in paragraph 10 CFR 50.73(a)(2)(iv)(B), specifically the reactor protection system including reactor scram.
C. CAUSE OF EVENT
The cause of the FWRV failure was due to failure of the respective air solenoid valve [SOL], which is used to control FWRV position. The solenoid valve failure prevented the FWRV from repositioning.
Failure analysis and root cause of the air solenoid valve failure was due to a manufacturing byproduct on the pilot valve plunger, which prevented the pilot valve from seating. A small piece of plastic was found on the internal seat surface. The plastic is the same material as the valve body construction. This material is not consistent with any other component in the instrument air system. Evidence supports the conclusion that the material was present when the valve was assembled at the factory.
D. SAFETY ANALYSIS
SEQUENTIAL NUMBER 001 REV NO.
01 The safety significance of this event was determined to be minimal based upon the availability of the required systems to
- 1) Shutdown the reactor and maintain it in a safe shutdown condition,
- 2) Remove residual heat,
- 3) Control the release of radioactive material, or
- 4) Mitigate the consequences of an accident.
There were no safety consequences impacting plant or public safety as a result of this event. There was no loss of safety function for this event.
E. CORRECTIVE ACTIONS
Corrective actions included replacement of the failed air solenoid valve.
Additional corrective action(s) include inspecting similar incoming valves and certifying the valves are free of foreign material by a second or third party vendor and the solenoid valves for the feedwater regulating valves were reclassified as single point vulnerabilities to develop mitigation and elimination strategies for potential failures.
F. PREVIOUS OCCURRENCES
No previous occurrences of this event were determined through the investigation.
G. COMPONENT FAILURE DATA
I Device I Manufacturer I Model I SIN I Comp Type I
I Solenoid Valve IASCO I 542 02 020 I NIA I SOL I Page_3_ of _3_