05000529/LER-2004-001, Regarding Steam Generator Tube Leak
| ML041600565 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/01/2004 |
| From: | Danni Smith Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 192-01142-DMS/SAB/DJS LER 04-001-00 | |
| Download: ML041600565 (7) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown |
| 5292004001R00 - NRC Website | |
text
L-PS A sub~sidiat rl'qPinnacte IHi-st Capital Corpo~ration 1 OCFR50.73 Palo Verde Nuclear Generating Station David M. Smith Plant Manager Nuclear Production Tel.
623-393-6116 Fax.
623-393-6077 e-mail: DSMITH1Oapsc.com Mail Station 7602 P.O. Box 52034 Phoenix, AZ 85072-2034 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 192-01142-DMS/SAB/DJS June 1, 2004
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS) Unit 2 Docket No. STN 50-529 License No. NPF-51 Licensee Event Report 2004-001-00 Attached please find voluntary Licensee Event Report (LER) 50-529/2004-001-00 that has been prepared and submitted pursuant to 10CFR50.73. This voluntary LER reports findings related to actions taken upon discovery of a small steam generator tube leak in the number 1 steam generator, located in Palo Verde Generating Unit 2.
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, DMS/SAB/DJS/kg Attachment cc:
B. S. Mallett M. B. Fields N. L. Salgado NRC Region IV Regional Administrator NRC NRR Project Manager + (send electronic and paper)
NRC Senior Resident Inspector for PVNGS 7 7z,
De-Cab
APPROVED BY OMB NO. 3150-0104 EXPIRES 7-31-2004 NRC FORM 386 U.S. NUCEAR REGULATORY
, the NRC may not conduct or sponsor, and a person is not required to respond to, the Information collection.
l3. PAGE Palo Verde Nuclear Generating Station Unit 205000529 1 1OF 6
- 4. TITLE Steam Generator Tube Leak
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILmES INVOLVED SEQUENTIAL MOT A
ER FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR IN REV NO MONTH DAY YEAR
_05000 02 19 2004 2004 -
001 00 06 01 2004 FACILITY NAME DOCKET NUMBER
_05000
- 9. OPERATING 1 1. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
MODE 1 _
20.2201(b)
_ 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(B) 50.73(a)(2)(ix)(A)
- 10. POWER 100 20.2201(d) 20.2203(a)(4) 50.73(a)(2)(iii) 50.73(a)(2)(x)
LEVEL 20.2203(a)(1) 50.36(c)(1 )(i)(A) 50.73(a)(2)(iv)(A) 73.71 (a)(4) 20.2203(a)(2)(I)
=
50.36(c)(1)(ii)(A)
_ 50.73(a)(2)(v)(A) 73.71 (a)(5)
_'i i _
___20.2203(a)(2)(ii) 50.36(c)(2) 50.73(a)(2)(v)(B)
OTHER - Voluntary 20.2203(a)(2)(iii) 50.46(a)(3)(ii) 50.73(a)(2)(v)(C)
Specify in Abstract below or 20.2203(a)(2)(iv) 50.73(a)(2)(i)(A)
_ 50.73(a)(2)(v)(D) in
Abstract
At 15:22 Mountain Standard Time (MST) on 2119/04, the Control Room staff received ALERT radiation level alarms from the Main Steam Line N-16 Radiation Monitors, RU-142, channels 1 and 2 indicating there was primary to secondary leakage in Steam Generator #1, and entered the Excessive RCS Leakrate procedure. At 15:38 MST, the ALERT radiation level alarm was received from the Condenser Air Removal System Radiation Monitor, RU-1 41, channel 2 indicating primary to secondary leakage at a rate of approximately 11 Gallons Per Day (GPD). At 16:00 MST, Plant Management determined they would shutdown Unit 2 in response to the apparent increase in steam generator primary to secondary leakage. Preliminary results of grab samples from the Condenser Air Removal System confirmed that primary-to-secondary leak rate had increased from the pre-event leak rate of 0.4 to 0.7 GPD to approximately 3 to 5 GPD. At 16:31 MST, a plant shutdown was commenced. The reactor was manually tripped from approximately 21% power. The Steam Generator primary to secondary leak rate did not exceed the Technical Specification limit of 150 GPD (LCO 3.4.14), the EPRI guidelines that would require a plant shutdown or the Station Administrative shutdown limit of 50 GPD.
In situ testing was performed on the leaking tube and met the criteria of retaining a margin of 3.0 against burst under normal steady state full power operation and a margin of 1.4 against burst under the limiting design basis accident concurrent with a safe shutdown earthquake. The tube was plugged during the subsequent mid-cycle outage.
In the past three years, Palo Verde Nuclear Generating Station has not experienced a Steam Generator tube leak that required a Unit shutdown.
NHU FOHM 366 7-2001)
I (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 Forn 366A)
- 6.
CAUSE OF THE EVENT
APS has concluded that the direct cause of the tube leak was a through wall defect of the tube wall for the affected tube, that either immediately created a minute leak at that location or that weakened a tiny area of tube material such that leakage occurred. The evidence that was collected established that deformation occurred during packaging of the tubes, prior to their installation in the steam generator. The package construction utilized spacer and cross brace materials that were assembled as the tubes were loaded using common wood screws.
The design of this packaging placed the wood screws in close proximity to specific locations on some tubes. The tube involved in this event and the location, shape and size of the deformation in that tube are consistent with damage that would occur if the packaging were assembled incorrectly such that a wood screw penetrated completely through the packaging materials and came in contact with the tube.
Root causes for this condition were:
(1) Human error on the part of the person(s) assembling the packaging for the Unit 2 SGI tube bundles at the tube manufacturer's (Sandvik) facility; and (2) Less than adequate transportability review by the fabricator (Ansaldo) and follow-up by APS for a prior nonconformance report identifying a similar incident.
No unusual characteristics of the work location (e.g., noise, heat, poor lighting) directly contributed to this event.
NRC FORM 36A (7-2001)
WC (If more space is required, use additional copies of NRC Form 366A)
- 7.
CORRECTIVE ACTIONS
Corrective actions to address the direct and root causes include:
(1) The leaking tube has been plugged.
(2) Pre-service eddy current results for all tubes in both of the Unit 2 steam generators have been reviewed to ensure that no other tubes exhibiting an examination signature consistent with the identified puncture damage are in-service.
(3) APS will request information from the SG fabricator to identify the Unit 2 steam generator tubes that were shipped in package locations where packaging screw damage was possible.
(4) Tube locations where damage was possible will be evaluated for inclusion of NDE examinations as deemed necessary under the Steam Generator Management program.
(5) A Vendor Corrective Action Report (VCAR) to Ansaldo will be prepared to address improvements to the tube packing processes.
(6) APS will establish a formal review process for nonconformance reports generated at the tubing manufacturer's and steam generator fabricator's facilities.
(7) Damaged tubes from the original Unit 2 shipment that were discovered at the fabricator's facility on 3/18/2004 and 3/22/2004 will be provided to APS for additional testing.
- 8.
PREVIOUS SIMILAR EVENTS
In the past three years, Palo Verde Nuclear Generating Station has not experienced a Steam Generator tube leak that required a Unit shutdown.
- 9.
ADDITIONAL INFORMATION
Palo Verde in conjunction with EPRI is developing an acceptance review process for pre-service eddy current examination results that are intended to improve capabilities to detect indications with similar characteristics to the indication found in the failed Unit 2 steam generator tube.