ML15218A255
| ML15218A255 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/22/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML15218A254 | List: |
| References | |
| NUDOCS 9207300286 | |
| Download: ML15218A255 (4) | |
Text
FsREGj UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 SAFETY EVALUATION REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST NO. 92-04 FROM ASME SECTION XI REQUIREMENTS DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNIT 2 DOCKET NO. 50-270
1.0 INTRODUCTION
By letter dated February 4, 1992, Duke Power Company (the licensee) submitted a request (No. 92-04) for relief from article IWC-2430(a) of the ASME Boiler and Pressure Vessel Code Section XI, 1980 Edition (with Addenda through Winter 1980).
This article requires additional weld examinations when a weld defect is found during the examination of the audited sample of welds in an inspection. A flaw was detected by radiography in weld 2-OIA-5-33 in the Second Ten Year Interval Inservice Inspection (ISI).
This weld (ISI Class B) connects the steam pipe to the elbow on the Main Steam Discharge from B Steam Generator.
The basis for the requested relief is that the indication found during this inspection was not a service-induced failure but a previously undetected slag inclusion present in the weld when it was initially made. Since the detected indication was not a service-induced failure, the licensee maintains that it should not be the basis for requiring additional examinations of an enlarged sample. The corrective measures proposed were to remove the slag inclusion by grinding, to repair the weld and to perform a new baseline radiographic examination.
2.0 DISCUSSION The information provided by the licensee in support of the request for relief from impractical requirements has been evaluated and the bases for granting relief from those requirements are documented below.
Relief Request No. 92-04, Additional Examinations Due to Detection of an Original Fabrication Defect Code Requirement: Section XI, 80W81, IWC-2430(a), Additional Examinations Examinations that detect indications exceeding the allowable standards of IWC-3000 shall be extended to include an additional number of components (or areas), within the same examination category, approximately equal to the number of components (or areas) examined initially during the inspection.
9207300286 920722 PDR ADOCK 05000270 P
-2 Licensee's Code Relief Request:
For an indication found in weld 2-O1A-5-33, pipe to elbow joint on main steam discharge from steam generator "B", relief is requested from the required additional examinations of IWC-2430(a).
Licensee's Proposed Alternative: The indication will be removed and weld repaired. A new baseline radiographic examination (RT) will be performed.
Licensee's Basis for Requesting Relief: The indication found during this inspection is not a service induced failure but a slag inclusion present in the weld when the weld was initially fabricated. Since this flaw is not a service induced failure, it should not require additional examinations of an enlarged sample.
Staff Evaluation: The staff has reviewed and evaluated the request for relief with particular attention to confirming that the detected indication was a slag inclusion in the initial weld with no signs of change of character in subsequent inspections. The licensee provided additional information relating to these concerns in a letter dated March 3, 1992, and in a telephone conversation with the NRC staff on March 4, 1992.
The licensee stated that after locating the flaw indication in the latest radiographic examination, a very faint indication of the flaw could be discerned in the initial radiograph and in the first Ten-Year Inspection Interval ISI radiograph. The licensee ascribed the cleaner, more distinct indication of the flaw in the latest radiograph to a slightly different positioning of the radiographic source, so that the slag inclusion was not partially obscured by an adjacent metallic ring.
The licensee was not able, by examination of the three radiographs, to detect any change in the size or character of the defect. In the March 4, 1992 telephone conversation, the licensee stated that the slag inclusion was ground out and a radiograph of the rewelded area showed no defect present.
The results of previous inspections by the licensee have not had a similar situation. Slag inclusions in manual welds are a function of the welder's skill and rarely caused by the procedure or metallurgy. If the procedure was the cause, this type defect would have had an established history at this plant before this time. The staff regards the finding of this defect a unique, one time situation and not a general, frequent or pervasive situation.
On site inspections by NRC Region II have found that the licensee has a good inservice inspection program and has been conducting its examinations in accordance with the code with few exceptions, none of which are related to this situation. The present inservice inspection program has demonstrated adequate assurance that the plant had been constructed to an acceptable level of quality and assurance.
-3 Examination of additional welds in this one situation would provide very little increase in safety and quality in comparison to the other examinations and tests which have been accomplished in previous outages and those being accomplished this outage under the inservice inspection program.
3.0 CONCLUSION
Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee has determined that conformance with certain Code requirements is impractical for its facility and submitted supporting information. The staff has reviewed the licensee's submittal and has concluded, pursuant to 10 CFR 50.55a(a)(3)(i), that the proposed alternative provides a reasonable assurance of quality and safety.
We, therefore, further conclude that the licensee's proposed alternative to the Code requirements may be authorized as stated in Relief Request No. 92-04.
Principal Contributor: S. S. Kirslis, PDII-3 D. E. Smith, EMCB
OCONEE RELIEF REQUEST 92-04 DATED:
July 22, 1992 DISTRIBUTION:
11ocket-File6 NRC/Local PDRs PDII-3 READING Oconee READING SVarga GLainas DMatthews SKirsl is
[Wiens LBerry OGC, 15B18 JWiggins, 704 EJordan, MNBB3701 ACRS, P-315 (10)
LReyes, RII DSmith, 7D4