05000530/LER-2003-001, Regarding Main Steam Safety Valve as Found Lift Pressures Outside of TS Limits
| ML031400210 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 05/09/2003 |
| From: | Overbeck G Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 192-01118-GRO/SAB/DJS LER 03-001-00 | |
| Download: ML031400210 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 5302003001R00 - NRC Website | |
text
LAMi Palo Verde Nuclear Generating Station Gregg R. Overbeck Senior Vice President Nuclear 1 OCFR50.73 Mail Station 7602 TEL (623) 393-5148 P.O. Box 52034 FAX (623) 393-6077 Phoenix, AZ 85072-2034 192-01118-GRO/SAB/DJS May 9, 2003 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555-0001
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS) Unit 3 Docket No. STN 50-530 License No. NPF-74 Licensee Event Report 2003-001-00 Attached please find voluntary Licensee Event Report (LER) 50-530/2003-001-00 that has been prepared and submitted pursuant to 1 OCFR50.73. This voluntary LER reports findings related to an out-of-tolerance main steam safety valve (MSSV) which was discovered during pre-outage testing in Unit 3.
In accordance with 10CFR50.4, a copy of this LER is being forwarded to the NRC Regional Office, NRC Region IV and the Senior Resident Inspector. If you have questions regarding this submittal, please contact Daniel G. Marks, Section Leader, Regulatory Affairs, at (623) 393-6492.
Arizona Public Service Company makes no commitments in this letter. The corrective actions described in this LER are not necessary to maintain compliance with regulations.
Sincerely, G RO/SAB/DJ S/kg Attachment cc:
Regional Administrator-NRC Region IV N. L. Salgado J. N. Donohew
4 /
(all with attachment)
Z Z L__
APPROVED BY OMB NO. 3150-0104 EXPIRES 7-31-2004
Abstract
On March 20, 2003, Unit 3 was in MODE 1, operating at approximately 98 percent power when augmented testing revealed that one main steam safety valve (MSSV) had an as-found lift pressure above the Technical Specification limit of +/- 3 percent of design lift pressure. This MSSV is believed to have experienced setpoint drift.
The valve was reset per plant procedures to +/-1 % of the required setpoint upon completion of valve testing.
Previous similar events were reported in LER 50-529/2000-002, LER 50-529/2000-009, LER 50-529/2001-001 and LER 50-529/2002-001.
(If more space is required, use additional copies of (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Forrn 366A)
5. ASSESSMENT OF SAFETY CONSEQUENCES
A safety analysis has been performed to evaluate the as-found results from the Unit 3 surveillance testing. The analysis found that the as-found condition of the Unit 3 MSSV would not, under accident conditions, have resulted in peak pressures that would have exceeded the overpressure protection limits for the primary or secondary systems.
Based on the analysis, the out of tolerance condition would not have prevented the fulfillment of the safety function and did not result in a safety system functional failure as defined by 10CFR50.73(a)(2)(v).
- 6.
CAUSE OF THE EVENT
APS has concluded that the out of tolerance as-found MSSV setpoint was the result of setpoint drift. The valves did not exhibit the characteristics of sticking, therefore valve seat sticking is not considered to be the cause of this event.
No unusual characteristics of the work location (e.g., noise, heat, poor lighting) directly contributed to this event. No personnel or procedural errors contributed to this event.
The out of tolerance setpoint (greater than +/- 3%) was determined to be a Maintenance Rule Functional Failure (MRFF) even though the MSSVs as a group would not have exceeded the overpressure protection limits for the primary or secondary systems. The intended function of the MSSVs is to lift and relieve steam pressure when pressure within the steam line is within 3% of setpoint. The valve did not respond until steam line pressure was simulated to exceed +3% (3.3%).
- 7.
CORRECTIVE ACTIONS
Unit 3's MSSV PSV0578 was discovered to have a high as-found lift pressure outside of the technical specification limit during surveillance testing. The MSSV was adjusted and re-tested in accordance with the approved site procedure and returned to service.
NRC; FORM 3jA (7-2UU1)
(f more space is required, use additional copies of NRC Form 366A)
- 8.
PREVIOUS SIMILAR EVENTS
Previous similar events were reported in LER 50-529/2000-002, LER 50-529/2000-009, LER 50-529/2001-001 and LER 50-529/2002-001.