05000528/LER-2002-001, Regarding Reactor Trip Due to Core Protection Calculators Generating a CEA Deviation Trip Signal
| ML030140389 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 01/07/2003 |
| From: | Overbeck G Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 192-01113-GRO/SAB/DJS LER 02-001-00 | |
| Download: ML030140389 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 5282002001R00 - NRC Website | |
text
LAFS 1 OCFR50.73 Gregg R. Overbeck Mail Station 7602 Palo Verde Nuclear Senior Vice President TEL (623) 393-5148 PO Box 52034 Generating Station Nuclear FAX (623) 393-6077 Phoenix, AZ 85072-2034 192-01113-GRO/SAB/DJS January 7, 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 1 Docket No. STN 50-528 License No. NPF-41 Licensee Event Report 2002-001-00 Attached please find Licensee Event Report (LER) 50-528/2002-001-00 that has been prepared and submitted pursuant to 10CFR50.73(a)(2)(iv)(A). This LER reports a condition where Unit 1 experienced a reactor trip from approximately 64% power.
During a planned shut-down, a control element assembly (CEA) deviation within a subgroup of greater than 9.0 inches was detected and penalty factors were generated which led to a Core Protection Calculator (CPC) reactor trip. The corrective actions described in this LER are not necessary to maintain compliance with regulations.
In accordance with 10CFR50.73(d), 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.
Sincerely, GRO/SAB/DJS/kg Attachment cc:
E. W. Merschoff N. L. Salgado J. N. Donohew
APPROVED BY OMB NO 3150-0104 EXPIRES 7-31-2004
Abstract
On November 10, 2002 at approximately 2250 MST, Palo Verde Unit 1 was in Mode 1 (POWER OPERATION), operating at approximately 64 percent power when an automatic reactor trip occurred on low Departure from Nucleate Boiling Ratio (DNBR). The four Core Protection Calculators (CPC) generated a reactor trip on low DNBR due to the misalignment of a Control Element Assembly (CEA) from its subgroup. The misalignment occurred due to a failed optical isolation card in the control system for the CEA. The reactor was stabilized in Mode 3 (HOT STANDBY), and the Shift Manager classified the event as an uncomplicated reactor trip. No engineered safety feature actuations occurred during the event and none were required.
The cause of the reactor trip was a hardware failure that caused a CEA position deviation. Based on the CEA deviation, a large penalty factor was generated in both control element assembly calculators (CEAC1 and CEAC2), that resulted in an automatic reactor trip to occur on low DNBR.
In the past three years, there have been no previous similar events reported pursuant to 1 OCFR50.73.
NH(R FOHM 366 (7-2001)
(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 (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A)
The CEAC upgrade modification expected to be first installed during the fall 2003 Unit 2 outage will also permit all CEA RPS Trip positions to be displayed and monitored.
- 8.
PREVIOUS SIMILAR EVENTS
In the past three years, there have been no previous similar events reported pursuant to 1 OCFR50.73.
- 9.
ADDITIONAL INFORMATION
The reactor trip was a single actual initiating event that affected only the initiating event cornerstone in the regulatory oversight and assessment process. The event was tabulated as an Unplanned Scram in the performance indicator cornerstone of initiating events.