05000333/LER-2019-003, Safety Relief Valves Out of Tolerance
| ML19263B250 | |
| Person / Time | |
|---|---|
| Site: | FitzPatrick  |
| Issue date: | 09/20/2019 |
| From: | Timothy Peter Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| JAFP-19-0091 LER 2019-003-00 | |
| Download: ML19263B250 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3332019003R00 - NRC Website | |
text
Exelon Generation JAFP-19-0091 September 20, 2019 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 Timothy C. Peter Plant Manager - JAF James A. FitzPatrick Nuclear Power Plant Renewed Facility Operating License No. DPR-059 NRG Docket No. 50-333
Subject:
LER: 2019-003, Safety Relief Valves Out of Tolerance
Dear Sir or Madam:
This report is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) and 1 O CFR 50.73(a)(2)(v)(D) as an "Operation or Condition Prohibited by Technical Specifications" and "Event or Condition that Could Have Prevented Fulfillment of a Safety Function," respectively.
There are no new regulatory commitments contained in this report.
Questions concerning this report may be addressed to Mr. William Drews, Regulatory Assurance Manager, at (315) 349-6562.
TCP/WD/hm
Enclosure:
LER: 2019-003, Safety Relief Valves Out of Tolerance cc:
USNRC, Region I Administrator USNRC, Project Manager USNRC, Resident Inspector INPO Records Center (ICES)
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 4
- 4. Title Safety Relief Valves Out of Tolerance
- 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 7
29 2019 2019 - 003 - 00 09 20 2019 Facility Name N/A Docket Number N/A
- 9. Operating Mode Month Day Year Yes (If yes, complete 15. Expected Submission date) No 9
20 2019 Abstract (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
The As-Foundtest results for the eleven Safety/Relief Valve (S/RV) pilot assemblies removed and replaced during the 2018 Refueling Outage at James A. FitzPatrick Nuclear Power Plant (JAF) identified eight (8) S/RV pilot assemblies that lifted outside of the allowable tolerance required by Technical Specification Surveillance Requirement 3.4.3.1. Eight (8) two-stage S/RVs were found out of tolerance high. The eight S/RV pilot assemblies are assumed to have been inoperable at some point in the operating cycle that preceded the 2017 Refueling Outage resulting in a condition reportable pursuant to 10 CFR 50.73(a)(2)(i)(B).
The S/RV design features an electric actuation capability that provides a diversified means of opening the S/RVs despite the out of tolerance condition. However, the electric lift function is considered a backup to the mechanical S/RVs and is not credited in the accident analysis. Therefore, the TS inoperability of the eight (8) S/RVs also resulted in a condition reportable pursuant to 10 CFR50.73(a)(2)(v)(D).
The cause of the two-stage failures has been identified as corrosion bonding. The safety consequences associated with this event are considered low due to the electric actuation capability.
(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===
The ASME Boiler and Pressure Vessel Code requires the reactor pressure vessel be protected from overpressure during upset conditions by self-actuated safety valves. As part of the nuclear pressure relief system, the size and number of S/RVs are selected such that peak pressure in the Reactor Coolant Pressure Boundary (RCPB) will not exceed the ASME Code limits.
The James A. FitzPatrick Nuclear Power Plant (JAF) used eleven (11) two-stage Target Rock Safety/Relief Valves (S/RV) [EIIS Identifier: SB] for emergency pressure relief during operating Cycle 23. These valves are located on the main steam lines between the reactor vessel and the first isolation valve within the drywell.
Each S/RV discharges steam through a discharge line to a point below the minimum water level in the suppression pool.
The S/RVs can actuate by either of two modes: the safety mode or the relief mode. In safety mode (or spring mode of operation), the spring-loaded pilot valve opens when steam pressure at the valve inlet overcomes the spring force holding the pilot valve closed. Opening the pilot valve allows a pressure differential to develop across the main valve piston and opens the main valve. This satisfies the code requirement.
Each S/RV can be opened manually in the relief mode from the control room by its associated two-position switch. If one of these switches is placed in the open position the logic output will energize the associated S/RV solenoid control valve directing the pneumatic supply to open the valve. Seven of the installed S/RV solenoid control valves can also be energized by the relay logic associated with the Automatic Depressurization System (ADS).
During each refueling outage all eleven of the pilot assemblies are removed and replaced with vendor tested and certified components. The pilots that are removed are sent to a vendor facility for testing, refurbishment, and certification. The test results for pilot assemblies removed in 2018, during Refueling Outage 23, identified eight (8) S/RV pilot assemblies that were out of allowable tolerance. Eight (8) of the pilots (all two-stage) lifted at greater than the allowable setpoint range.
In order to address the concerns with corrosion bonding, JAF has replaced two-stage S/RVs with new design of three-stage Target Rock S/RVs in the Fall 2018 Refueling Outage (RO). Industry experience has shown that the three stage S/RVs are less susceptible to corrosion bonding. The design of the three-stage S/RVs produces a greater mechanical force on opening, resulting in a greater likelihood of overcoming any potential effects of corrosion bonding that might occur.
Event Description
As-Found testing was performed on all eleven main S/RV pilot assemblies removed in 2018, during RO23.
The testing was conducted by NWS Technologies. The TS setpoint for each S/RV is 1145 +/- 34.3 psig.
During the initial lift test, eight of the eleven pilot assemblies failed to open within the allowable range (1110.7 to 1179.3 psig). Eight of the eleven two-stage S/RV pilots failed high. As-Found failed test results are tabulated below. 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.
2019
- - 003
- - 00 Page 3 of 4 (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/)
Table 1 - As-Found Test Results In-service Location Pilot Serial Number First Test (psig)
Acceptance Range (1110.7 - 1179.3 psig) 02RV-71A 1051 1223 Unsat - High 02RV-71B 1045 1224 Unsat - High 02RV-71F 1052 1188 Unsat - High 02RV-71G 1238 1182 Unsat - High 02RV-71H 1236 1251 Unsat - High 02RV-71J 1218 1220 Unsat - High 02RV-71K 1191 1196 Unsat - High 02RV-71L 1013 1228 Unsat - High
Cause
JAF has extensive internal Operating Experience with the S/RVs failing higher than the allowable setpoint.
Causal evaluations identified corrosion bonding as the cause for the upward setpoint drift on the two-stage S/RVs. The As-Found test results shown above in conjunction with the successful second lift of all two-stage valves support this conclusion. Corrosion bonding is a crevice corrosion phenomenon that occurs between highly polished metals in a wetted solution in close proximity to each other. This proximity (usually a gap of between 0.1 and 100 µm) creates a crevice-like condition between the two wetted surfaces setting up the conditions for crevice corrosion to occur. An oxygen rich environment is created by the accumulation of oxygen in the area of the pilot disc due to the breakdown of water into hydrogen and oxygen. Susceptible material in the right geometry with exposure to oxygen and high temperatures are the conditions which cause corrosion bonding in JAF S/RVs. There is extensive industry experience with corrosion bonding in the Target Rock two-stage S/RVs pilot assemblies.
Similar Events
Internal JAF LER-17-004 Safety Relief Valves Out of Tolerance March 30, 2018 JAF LER-15-002 Safety Relief Valve Upward Setpoint Drift, June 1, 2015 JAF LER-11-003 Safety Relief Valve Setpoints Outside of Allowable Tolerances, August 8, 2011 JAF LER-09-005 Safety Relief Valve Setpoints Outside of Allowable Tolerances, June 22, 2009U.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.
2019
- - 003
- - 00 Page 4 of 4 (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/)
JAF LER-07-001 Safety Relief Valve Setpoints Outside of Allowable Tolerances, August 6, 2007 External Edwin I. Hatch Nuclear Plant, Unit 1: LER-16-004 Safety Relief Valves As Found Settings Resulted in Not Meeting Tech Spec Surveillance Criteria, May 26, 2016 Edwin I. Hatch Nuclear Plant, Unit 2: LER-08-004 Safety Relief Valves Allowable Test Range Exceeded Due to Setpoint Drift, August 12, 2008
Corrective Actions
Completed Corrective Actions Completed replacement of S/RVs with redesigned three-stage (RO23)
Future Corrective Actions None
Safety Significance
Nuclear safety -
Actual Consequences There were no actual consequences to the general safety of the public, nuclear safety, industrial safety, or radiological safety associated with this event.
Potential Consequences The potential consequences of this event are associated with the over-pressurization of the Reactor Coolant Pressure Boundary. The S/RVs provide overpressure protection for the Reactor Coolant Pressure Boundary as required by the ASME Boiler and Pressure Vessel Code. Events similar to the one reported herein may be significant if design limits are challenged. The potential consequences of this event are considered low based on the operation and availability of the Electric Lift System.
Radiological Safety There was no radiological safety impact associated with this event.
Industrial Safety There was no industrial safety impact associated with this event.
References JAF Issue Report - IR 04267818, July 29, 2019 JAF Technical Specifications