05000269/LER-2003-002, Regarding Apparent Reactor Coolant System Leakage from Three Reactor Vessel Head Penetrations
| ML033090486 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/27/2003 |
| From: | Rosalyn Jones Duke Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| O-03-05965 LER 03-002-00 | |
| Download: ML033090486 (8) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2692003002R00 - NRC Website | |
text
Duke R. A.
JONES.
c kPower.
Vice President A Duke Energy Company Duke Power 29672 / Oconee Nuclear Site 7800 Rochester Highway Seneca, SC 29672 864 885 3158 864 885 3564 fax October 27, 2003 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555
Subject:
Oconee Nuclear Station Docket No. 50-269 Licensee Event Report 269/2003-02, Revision 0 Problem Investigation Process No.: 0-03-05965 Gentlemen:
Pursuant to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Event Report 269/2003-02, Revision 0, addressing the discovery of apparent reactor coolant system leakage from three reactor vessel head penetrations.
This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(i)(B) and (a)(2)(ii)(A). For this event, the overall safety significance of this event was minimal and there was no actual impact on the health and safety of the public.
V e R.
Vice President Oconee Nuclear Site Attachment www. duke-energy. corn
Document Control Desk Date: October 27, 2003 Page 2 cc:
Mr. Luis A. Reyes Administrator, Region II U.S. Nuclear Regulatory Commission 61 Forsyth Street, S. W., Suite 23T85 Atlanta, GA 30303 Mr. L. N. Olshan Project Manager U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, D.C. 20555 Mr. M. C. Shannon NRC Senior Resident Inspector Oconee Nuclear Station INPO (via E-mail)
Abstract
Oconee Nuclear Station Unit 1 (ONS-1) entered its scheduled end-of-cycle 21 refueling outage on September 20, 2003. On September 23, 2003, a visual inspection of the bare reactor vessel head was performed while bolted to the vessel in order to determine if reactor coolant system leakage had occurred during the previous operating cycle. This bare head visual inspection was'performed looking through the nine access ports in the service structure support skirt on the reactor vessel head.
Results of the visual inspection dentified two (2) control rod drive mechanism (CRDM) nozzles and one (1) thermocouple (TIC) nozzle that exhibited similar leakage'characteristics as was found from previous nozzle inspection and repair campaigns. Consequently, these nozzles were conservatively classified as leaking.
The total leakage from the nozzles did not exceed Technical Specification limits for unidentified reactor coolant system inventory loss. At no time during the operating cycle did the' reactor building or area radiation alarms actuate as a result of this event. The small amount of boric acid deposits observed around the nozzles caused no visible head material loss (wastage) from erosion or corrosion.
The apparent root cause of the CRDM nozzle leaks is most likely primary water stress corrosion cracking. The minor leakage observed around the previously repaired T/C nozzle is most likely attributed to a welding defect.
This reactor vessel head will be retired from service and replaced with a new reactor vessel head prior to unit restart. For this event, the overall safety significance of this event was minimal and there was no actual impact on the health and safety of the public.
NRC FORM 366 (72001)
(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) (17)
Figure 1 - Oconee Unit 1 reactor vessel head Map Service Structure Support Flange
.herrrcouple Nozzles (8)
(Oconee Unit I Only)
@ From 1 EOC21: CRDM Nozzles 6,16 & Thermocouple Nozzle 7 (shown as # 75 from above, found leaking and not repaired - RVH Retired)
Q From 1 EOC20: CRDM Nozzles 7 and 8 (found leaking and repaired)
@ From EOC19: CRDM Nozzle 21 (leaking/repaired) and 8 Thermocouple Nozzles (leaking/plugged)