05000456/LER-2002-001, Set Point Drift Causes Two of Three Pressurizer Safety Valve Lift Tests to Exceed Technical Specification Tolerance on April 8, 2002
| ML021710070 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 06/07/2002 |
| From: | Vonsuskil J Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BW020054 LER 02-001-00 | |
| Download: ML021710070 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4562002001R00 - NRC Website | |
text
ExekInM Exelon Generation Company, LLC www.exeloncorp.com Nuclear Braidwood Station 35100 South Rt 53, Suite 84 Braceville, IL 60407-9619 Tel. 815-417-2000 June 7, 2002 BW020054 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Unit 1 Facility Operating License No. NPF-72 NRC Docket No. STN 50-456
Subject:
Submittal of Licensee Event Report Number 2002-001-00, "Set Point Drift Causes Two of Three Pressurizer Safety Valve Lift Tests to Exceed Technical Specification Tolerance" The enclosed Licensee Event Report (LER) is being submitted in accordance with 10 CFR 50.73, "Licensee event report system", paragraph (a)(2)(i)(B). 10 CFR 50.73(a) requires an LER to be submitted within 60 days after discovery of the event; therefore, this report is being submitted by June 7, 2002.
Should you have any questions concerning this letter, please contact Amy Ferko, Regulatory Assurance Manager, at (815) 417-2699.
Respectfully, Jmes D. von Suskil ite Vice President Braidwood Station
Enclosure:
LER Number 2002-001-00 cc:
Regional Administrator - Region IlIl NRC Braidwood Senior Resident Inspector
bcc: Braidwood Station Project Manager - NRR Nicholas Reynolds - Winston & Strawn Regulatory Assurance Manager - Braidwood Station Regulatory Assurance Manager - Byron Station Vice President - Licensing and Regulatory Affairs Director, Licensing - Midwest Regional Operating Group Manager, Licensing - Braidwood and Byron Stations Braidwood Nuclear Licensing Administrator Exelon Document Control Desk Licensing (Hard Copy)
Exelon Document Control Desk Licensing (Electronic Copy)
Abstract
On April 8, 2002, Braidwood Station discovered that two of three pressurizer safety valves (PSVs) removed during refueling outage AlR09 and subsequently tested at an offsite facility, did not meet the Technical Specification (TS) acceptance criteria. TS 3.4.10, "Pressurizer Safety Valves," requires three pressurizer safety valves to be operable with lift settings greater than or equal to 2460 psig and less than or equal to 2510 psig.
The surveillance requirement requires each valve to be operable in accordance with the Inservice Testing (IST)
Program and that following testing the lift setting shall be within +/-
1 percent of the TS setpoint. One valve had a lift setpoint 1.1 percent high, the other was 1.4 percent low.
There are no material condition issues with the PSVs that are contributing to the test failures. The PSVs are performing within their design capabilities.
The test failures are mainly due to the close tolerance required by the current plant safety analysis and reflected in TSs and the inability of the valves to perform within that tolerance.
Contributing to the valve test failures is lack of management responsiveness to reconcile continued PSV test failures.
The corrective action is to investigate revising the safety analysis to support a relaxation of the 1 percent TS requirement for the PSV lift setpoint tolerance.
An engineering analysis on the effects of the PSVs lifting outside of the TS tolerance concluded that all acceptance criteria in the Updated Final Safety Analysis Report Chapter 15, "Accident Analyses," were still met.
This event is being reported pursuant to 10CFR50.73(a)(2)(i) (B).U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
FACILITY NAME (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION NUMB3ER NUMBER Braidwood, Unit 1 STN 05000456 N
2 of 3 2002 -
001 -
00 A.
Plant Operating Conditions Before The Event
Unit: 1 Event Date: 4/8/2002 Event Time: 0900 MODE: 1 Reactor Power: 100 percent Reactor Coolant System [AB] Temperature: 580 degrees F, Pressure: 2235 psig B.
Description of Event
There were no systems or components inoperable at the beginning of this event that contributed to the severity of the event.
As part of refueling outage AlRO9 activities (AlRo9 occurred between September 22, 2001 and October 12, 2001), the three PSVs (i.e., lRY8010A, lRY8010B and lRY8010C) were removed in accordance with the IST program and replaced with three spare valves which had been previously verified to be within the TS required tolerance of +/-
1 percent.
The three PSVs that were removed were sent to the NWS Technologies facility for as-found lift setpoint testing and refurbishment.
The PSVs acceptance criteria for the as-found lift setpoint is 2485 psig +/- 1 percent, as required by TS 3.4.10. Two of the three PSVs exceeded this criterion.
One valve lifted at 2513 psig (i.e., 1.1 percent high), and the other lifted at 2449 psig (i.e., 1.4 percent low).
The third valve was within tolerance.
Although outside of the TS required tolerance, the valve lift setpoints were within the American Society of Mechanical Engineers,Section XI, "Rules For Inservice Inspection of Nuclear Power Plant Components," part OM-1 acceptance criteria of +/-
3 percent.
- Also, the valves were subjected to subsequent bench tests where the valves tested within the +/- 1 percent of the TS acceptance criteria without any repairs being made to the valves.
Since both of the valves that failed the as-found lift setpoint testing had been replaced with operable valves during AlRO9, no TS action applied at the time the valve test failures were discovered.
However, the condition of multiple pressurizer safety valves being outside of their required lift setting tolerance band is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B), "Any operation or condition prohibited by the plant's Technical Specifications."
C.
Cause of Event
The safety valves were inspected by the vendor and no material condition issues were found that may have contributed to the out of tolerance condition.
An Electric Power Research Institute (EPRI) evaluation concerning safety and relief valve testing indicates that the PSVs at Braidwood are performing within their design capabilities. The test failures are mainly due to the close tolerance required by the current plant safety analysis and reflected in TSs and the inability of the valves to perform within those tolerances.U.S. NUCLEAR REGULATORY COMMISSION (1-2001)
LICENSEE EVENT REPORT (LER)
FACILITY NAME (1)
DOCKET (2)
LER NUMBER (6)
PAGE (3)
YEAR SEQUENTIAL REVISION NUMBER NUMBER Braidwood, Unit 1 STN 05000456 1
3 of 3 2002 -
001 -
00 The offsite test facility, NWS Technologies, indicated that based on industry experience, the PSVs performed as expected.
They stated that in the industry, the number of valves exceeding the 1 percent tolerance band is significant.
They also stated that most valves tested do not exceed the 2 percent level, and it is rare for valves to exceed the 3 percent range.
Based on this response and a review of Braidwood Station's historical data, the Braidwood Station PSV test results are typical of those in the industry.
Contributing to the valve test failures is lack of management responsiveness to reconcile continued PSV test failures.
D.
Safety Consequences
The pressurizer safety valves in conjunction with the Reactor Protection System, provide overpressure protection for the Reactor Coolant (RC)[AB] System.
The safety valves are designed to prevent system pressure from exceeding the RC System safety limit of 2735 psig.
An engineering analysis on the effects of the PSVs lifting outside of the TS tolerance concluded that all acceptance criteria in the Updated Final Safety Analysis Report Chapter 15 analyses were still met.
The event did not result in a Safety System Functional Failure.
E.
Corrective Actions
Revision of the safety analysis to support relaxation of the TS lift tolerance for pressurizer safety valves is being investigated as the corrective action to prevent future PSV lift test failures.
F.
Previous Occurrences
Test data from the last five refueling outages at Braidwood Station show that out of 15 valves tested, eight were out of tolerance.
Five of those eight were out of tolerance low, three were high.
Only one of the valves exceeded 2 percent; none exceeded 3 percent.
There have been no previous corrective actions applied to PSV lift test failures.
Until the valve failures from refueling outage AlRO9 were determined to be outside of the TS limits, station management interpreted the TS as being met if the as-found condition of the valve was within 3 percent, as required by the IST program, and the as-left setpoint was within 1 percent as required by the TS.
G.
Component Failure Data
Manufacturer Nomenclature Model Mfg. Part Number Crosby Pressurizer Safety Valve HB-BP-86 N/A