ML15112A397
| ML15112A397 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/16/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML15112A396 | List: |
| References | |
| NUDOCS 9902180312 | |
| Download: ML15112A397 (7) | |
Text
RE u UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST FROM ASME CODE SECTION XI REQUIREMENTS FOR TENDON INSPECTION DUKE ENERGY CORPORATION OCONEE NUCLEAR STATION, UNITS 1. 2. AND 3 DOCKET NOS. 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
The Technical Specifications (TS) for the Oconee Nuclear Station (Oconee), Units 1, 2, and 3, state that the inservice inspection of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code), Class 1, 2, and 3 components shall be performed in accordance with the ASME Code,Section XI and applicable addenda as required by Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Section 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if: (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that the inservice inspection (ISI) of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for Oconee's third 10-year ISI interval is the 1989 Edition.
By letter dated May 6, 1998 (Reference 1), Duke Energy Corporation (Duke/the licensee),
submitted Request for Relief No. 98-ONS-0002 seeking relief from the requirements of the ASME Code,Section XI, Subsection IWL, for Oconee, Units 1, 2, and 3. By letter dated September 16, 1998, the licensee responded to the NRC's Request for Additional Information.
This relief request was submitted during the third 10-year ISI interval for IWL examinations.
Enclosure
-9902180312 990216 PDR ADOCK 05000269.
__ P PDR
- g 0
-2 Report (TER), prepared by the staff's contractor, the Idaho National Engineering and Environmental Laboratory.
2.0 EVALUATION Request for Relief No. 98-ONS-0002, Paraqraph IWL-2522, Post-Tensioning Systems of Class CC Components A. Code Requirements:
IWL-2420 requires that unbonded post-tensioning systems be examined in accordance with IWL-2520 at 1, 3, and 5 years following the completion of the containment structural integrity test and every 5 years thereafter. Selection of tendons to be examined is in accordance with IWL-2521 and Table IWL-2521 -1.
IWL-2421 allows sites with two plants to modify the examination requirements for the concrete containments if (a) both containments use the same prestressing system and are essentially identical in design, (b) post-tensioning operations for the two containments were completed not more than 2 years apart, and (c) both containments are similarly exposed to or protected from the outside environment.
B. Systems/Components for which Alternative is Requested:
Unbonded post-tensioning systems of concrete containments (Class CC components).
C. Alternative Examination(s) Proposed by Licensee:
In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to implement a modified examination schedule that evenly distributes the examination of unbonded post-tensioning systems throughout the three plants at Oconee. The licensee stated:
An alternative is requested to the requirements of IWL-2421 and Table IWL-2521-1 to permit a modified examination program for IWL-2522 examinations of concrete containment post-tensioning systems at Oconee.
In lieu of the examination plan detailed in Table 1 (in Reference 1), Duke proposes an alternative to use the examination plan listed in Table 2 (in Reference 1) for all tendon examinations. This will enable Oconee to distribute these examinations equally among all three units.
D. Justification and Basis for Proposed Alternative:
The licensee's basis for the proposed alternative and its evaluation is discussed in the attachment to this evaluation.
-3 E. Staff Evaluation:
As stated in the attached TER, the proposed alternative to distribute the examinations among all three units represents a sound engineering approach for the examination of unbounded post-tensioning systems. The licensee has also stated that the proposed alternative includes an evaluation of any questionable conditions (i.e., exam results that do not meet IWL-31 00) found in one unit for their applicability to the other two units to ensure the integrity of the post-tensioning tendon system in all units (Reference 3). Therefore, the staff finds that the proposed alternative provides an acceptable level of quality and safety.
3.0 CONCLUSION
Based on the review of the information provided in the licensee's submittals, the staff finds the alternative proposed in lieu of IWL-2421 of Subsection IWL of Section XI of the ASME Code acceptable for the ISI of the three units of Oconee. Therefore, the use of the alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Attachment:
Technical Evaluation Report Principal Contributor: Hansraj G. Ashar Date:
February 16, 1999
-4 References
- 1.
Letter from W. R. McCollum, Jr. (Duke) to the NRC "Request to Use an Alternative to the Requirements of Section XI of the ASME Code, as endorsed by 10 CFR 50.55a,"
dated May 6,1998.
- 2.
Letter from W. R. McCollum, Jr. (Duke) to the NRC "Response to Staff's RAI on Use of an Alternative to the Requirements of Section XI of the ASME Code, as endorsed by 10 CFR 50.55a," dated September 16, 1998.
- 3.
Letter from W. R. McCollum, Jr. (Duke) to the NRC dated January 21, 1999.
TECHNICAL LETTER REPORT ON IWE/IWL CONTAINMENT INSPECTION REQUEST FOR RELIEF NO. 98-ONS-0001 sic, 00021 FOR DUKE POWER COMPANY OCONEE NUCLEAR STATION, UNITS 1. 2. AND 3 DOCKET NUMBERS: 50-269, 50-270 AND 50-287
- 1.
INTRODUCTION By letter dated May 6, 1998, the licensee, Duke Energy Corporation, submitted Request for Relief No. 98-ONS-0001 [sic, should be 0002] seeking relief from the requirements of the ASME Code,Section XI, Subsection IWL, for the Oconee Nuclear Station, Units 1, 2, and 3. By letter dated September 16, 1998, the licensee responded to the NRC request for additional information. This relief request was submitted during the third 10 year inservice inspection (ISI) interval for IWL examinations. The Idaho National Engineering and Environmental Laboratory (INEEL) staff's evaluation of the subject request for relief is in the following section.
- 2.
EVALUATION The information provided by Duke Energy Corporation in support of the request for relief from Code requirements has been evaluated and the basis for disposition is documented below. The containment inspections (Subsection IWE/IWL) for the Oconee Nuclear Station, Units 1, 2, and 3, were developed in accordance with the requirements of the 1992 Edition, 1992 Addenda of Section XI of the ASME Boiler and Pressure Vessel Code, as required by 10 CFR 50.55a(g)(6)(ii)(B).
Request for Relief No. 98-ONS-0001 [sic. should be 00021, Paraqraph IWL-2522, Post Tensioning Systems of Class CC Components Code Requirement: IWL-2420 requires that unbonded post-tensioning systems be examined in accordance with IWL-2520 at 1, 3, and 5 years following the cnompletion of the containment Structural Integrity Test and every 5 years thereafter. Selection of tendons to be examined is in accordance with IWL-2521 and Table IWL-2521 -1.
IWL-2421 allows sites with two plants to modify the examination requirements for the concrete containments if a) both containments use the same prestressing system and are essentially identical in design, b).post-tensioning operations for the two containments were completed not more than 2 years apart, and c) both containments are similarly exposed to or protected from the outside environment.
Licensee's Proposed Alternative: In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposed to implement a modified examination schedule that evenly distributes the examination of unbonded post-tensioning systems throughout the three plants at Oconee Nuclear Station, Units 1, 2, and 3. The licensee stated:
Attachment
-2 "An alternative is requested to the requirements of IWL-2421 and Table IWL-2521 1 to permit a modified examination program for IWL-2522 examinations of concrete containment post-tensioning systems at Oconee.
"In lieu of the examination plan detailed in Table 1, Duke Energy proposes an alternative to use the examination plan listed in Table 2 for all tendon examinations. This will enable Oconee to distribute these examinations equally between all three units.'"
Licensee's Basis for Proposed Alternative (as stated):
"Oconee has reactor containments that meet the requirements of IWL-2521 -1(a),
except that there are three containments at the site.
"Because IWL-2421 does not provide an alternative examination schedule for a site with three plants, Duke Energy has determined that the modified schedule permitted by IWL-2421 can be applied only to Oconee units 1 and 2. The Unit 3 post-tensioning system examinations would comply with the requirements of IWL 2420 and IWL-2520, and would not utilize a modified examination schedule. This approach is consistent with the position stated by the NRC in SECY-96-080,, for IWL Comment 2.8 submitted by Duke Power.
"The completion dates for initial post-tensioning operations at Oconee are as follows:
Unit 1 November 1970 Unit 2 December 1971 (13 months after Unit 1)
Unit 3 June 1973 (18 months after Unit 2)
... As Table 11 shows, the required number of tendons subject to IWL-2522 examinations during any ten year period is not equal for each unit.
"The proposed alternative plan for the unbonded post-tensioning system examinations provides an improved level of quality and safety because IWL-2522 examinations would be performed every five years on each unit, allowing earlier detection of potential conditions that could adversely affect the structural integrity of the containment. This alternative will allow for a better distribution of randomly selected tendons throughout all three units, improving the statistical quality of the sample, and will result in nearly the same number of tendons being examined as that required by Subsection IWL."
Evaluation: Paragraph IWL-2420 specifies schedule requirements for examination of unbonded post-tensioning systems for concrete containments. Paragraph IWL-2421 allows sites with two plants to modify the examination requirements if the following' conditions exist;
- 1)
Both containments use the same prestressing system
- 2)
Containments are essentially identical in design
- 1. Tables in the licensee's submittal are not included in this report.
-3
- 3)
Post-Tensioning operations for the two containments were completed not more than 2 years apart
- 4)
Both containments are similarly exposed to or protected from the outside environment.
The three plants at Oconee Station meet these criteria. The Code does not address the circumstances encountered at the Oconee Nuclear Station where three similar units exist on one site. The licensee's proposal, to distribute the examinations between all three units, appears to represent a sound engineering approach for the examination of unbonded post-tensioning systems.
10 CFR 50.55a(g)(6)(B)(2) requires that all licensees implement the inservice examinations that correspond to the number of years of operation that are specified in Subsection IWL of the 1992 Edition, 1992 Addenda. In the case of the Oconee Nuclear Station, the examinations for the twenty-fifth year apply. The licencee's proposed alternative includes examination of a larger sample of the unbonded post-tensioning components than would be required if the licensee performed the examinations in accordance with Paragraph IWL-2421 for Units 1 and 2, and included Unit 3 as a singular unit. The tables provided in the licensee's submittal show that 97 tendons would be examined using the Code requirements, as written, and 146 tendons would be examined using the proposed alternative. The proposal distributes these examinations evenly throughout the three plants. For these reasons, the proposed alternative provides an acceptable level of quality and safety.
It should be noted that, because the aggregate population of all three plants is being used to select a tendon sample at each plant, the licensee should apply a similar approach to any related Code requirements. For example, if examination results do not meet the acceptance standards of IWL-3200 during the inspection of tendons at one unit, the licensee should include all three Oconee units in the scope of additional examinations.
- 3.
CONCLUSION The INEEL staff evaluated the licensee's submittal and concluded that the licensee's proposed alternative provides an acceptable level of quality and safety at the Oconee Nuclear Station, Units 1, 2, and 3, and should be authorized pursuant to 10 CFR 50.55a(a)(3)(i).