ML15112A410
| ML15112A410 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Mcguire, Catawba, McGuire  |
| Issue date: | 03/04/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML15112A409 | List: |
| References | |
| NUDOCS 9903100018 | |
| Download: ML15112A410 (5) | |
Text
eptRE04 UNITED STATES NUCLEAR REGULATORY COMMISSION S
&WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST 98-GO-007 FROM ASME SECTION XI REQUIREMENT DUKE ENERGY CORPORATION MCGUIRE NUCLEAR STATION, UNITS 1 AND 2 CATAWBA NUCLEAR STATION, UNITS 1 AND 2 OCONEE NUCLEAR STATION, UNITS 1. 2. AND 3 DOCKET NOS. 50-369, 50-370, 50-413, 50-414, 50-269, 50-270, AND 50-287
1.0 INTRODUCTION
Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(g) requires that 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 ASME Code,Section XI, except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Pursuant to 10 CFR 50.55a(b) and (g), inservice inspection of containment must meet the requirements of the 1992 Edition, 1992 Addenda of Section XI, Subsections IWE and IWL. Pursuant to 10 CFR 50.55a(g)(6)(ii)(B), the first period containment examinations must be completed by September 9, 2001. Alternatives to the requirements of 10 CFR 50.55a(g) may be authorized under 10 CFR 5q.55a(a)(3), if (i) the proposed alternative provides an acceptable level of quality and safety, or (ii) compliance with the specific requirement of the Code would result in hardship or undsual difficulty without a compensating increase in the level of quality and safety.
By letter dated October 19, 1998, Duke Energy Corporation (DEC) requested that the NRC staff approve a proposed alternative to the examination requirement of the ASME Code,Section XI, Subsection IWE, 1992 Edition with the 1992 Addenda for the McGuire Nuclear Station, Units 1 and 2, Catawba Nuclear Station, Units 1 and 2, and Oconee Nuclear Station, Units 1, 2, and 3.
Specifically, DEC requested approval of the use of a sampling plan for augmented examination of surface areas of metal containment and liners of concrete containment (Class MC components), as specified in the ASME Code, Subsection IWE-2500(c)(4) and Table IWE-2500-1.
2.0 EVALUATION Code Requirement and Relief Request Relief is requested from the requirements of IWE-2500(c)(4) and Table IWE-2500-1, Examination Category E-C, Containment Surfaces Req pliring Augmented Examination. An alternative is provided for the ultrasonic thickness measurement requirements of IWE-2500(c)(4) and Table IWE-2500-1.
9903100018 990304 PDR ADOCK 05000269 P
-2 Basis for Requesting Relief:
IWE-2500(c)(4) requires the following:
(4) Ultrasonic measurements shall be used to determine the minimum wall thickness within each grid, and that the location of the minimum wall thickness shall be marked such that periodic reexamination of that location can be performed in accordance with the requirements f Table IWE-2500-1, Examination Category E-C.
Table IWE-2500-1, Examination Category E-C, Item E4.12 requires ultrasonic thickness measurement of 100 percent minimum wall thickness locations during each inspection period, established in accordance with IWE-2500(c)(3) and IWE-2500(c)(4). The extent of examination shall be 100 percent for each inspection period until the areas remain essentially unchanged for three consecutive inspection periods. Such areas no ionger require augmented examination in accordance with IWE-2420(c).
DEC has interpreted the ASME Code to require 100 percent of areas subject to ultrasonic thickness measurement be examined in accordance with Table IWE-2500-1, Category E-C, Item E4.12. Because IWE-1241 is applicable to areas that not only have experienced accelerated degradation and aging, but also to areas that could experience such degradation and aging, potentially large areas of containment surfaces may require ultrasonic thickness measurement. DEC has stated that the requirement to perform examinations on 100 percent of these areas is excessive and may expose personnel to increased radiological exposure, with no compensating increase in quality and safety. A 100 percent examination is unwarranted if an appropriate sampling plan is established for these examinations that provides an equivalent level of assurance that potential degradation can be detected.
Alternative Examination In lieu of the requirements of IWE-2500(c)(4), the licenee is proposing the following alternative:
(4) Ultrasonic thickness measurements shall be used to determine the minimum wall thickness within each grid selected for examination. The location of the minimum wall thickness shall be recorded or marked so that periodic reexamination of that location can be performed in accordance with Table 1, Examination Category E-C, Containment Surfaces Requiring Augmented Examination.
In lieu of the requirements of Table IWE-2500-1, Examination Category E-C, Containment Surfaces Requiring Augmented Examination, the attached table (from Ref. 1) is proposed. The table describes the sampling plan proposed in lieu of the Code requirement.
-3 Staff Evaluation The staff finds that implementation of the 100 percent examination requirement of Table IWE 2500-1, Category E-C, Item E4.12 would entail an unnecessary burden, and in some cases could subject the examining personnel to unnecessary radiation exposure. The proposed alternative sampling plan is based on Table 1, "Sample Size Required to Satisfy the 95/5 Criterion," of draft Regulatory Guide DG-1070 (Ref. 2). Though the draft guide is applicable to commercial grade items in nuclear power plants, the sampling plan in Table 1 is applicable to surface areas to be examined, as long as the lots and lot sizes are properly defined. DEC has defined the lots as grids of uniform size not exceeding one foot square. The licensee will use the sample size corresponding to zero defects in the sample. The staff considers the sampling plan reasonable and acceptable, and that it will provide reasonable assurance of structural integrity.
3.0 CONCLUSION
DEC has provided an alternative to the ASME Code requirements from which the relief is requested. The staff concludes that compliance with the ASME Code requirements would impose unnecessary hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, the proposed alternati ve is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) for McGuire Nuclear Station, Units 1 and 2, Catawba Nuclear Station, Units 1 and 2, and Oconee Nuclear Station, Units 1, 2, 1 nd 3.
Attachment:
Table 1 Principal Contributor: H. Ashar Date:
March 4, 1999 REFERENCES
- 1.
Letter from M. S. Tuckman (DEC) to NRC, "Request to Use an Alternative to the Requirements of Section XI of ASME Boiler and Pressure Vessel Code,Section XI in accordance with 10 CFR 50.55a(a)(3)(i). Duke Energy Corporation Serial Number 98-GO-007," dated October 19, 1998.
- 2.
Draft Regulatory Guide DG-1070, "Sampling Plans Used for Dedicating Simple Metallic Commercial Grade Items for Use in Nuclear Power Plants," September 1997.
TABLE 1 EXAMINATION CATEGORY E-C, CONTAINMENT SURFACES REQUIRING AUGMENTED EXAMINATION Item Parts Examination Examination Acceptance Extent and Frequency of Deferral of No.
Examined Requirements/
Method Standard Examination Inspection Fig. No.
(See Notes 1, 2) to End of Interval 1st Successive Inspection Inspection Interval Intervals E4.10 Containment Surface Areas E4.11 Visible IWE-2500(c)
- Visual, IWE-3512.1 100% of 100% of Not Surfaces VT-1 IWE-3512.2 Surface Surface Permissible Areas Areas Identified Identified by by IWE-1242 IWE-1242 E4.12 Surface Area IWE-2500(c)
Ultrasonic IWE-3512.3 100% of 100% of Not
- Grid, Thickness Minimum Wall Minimum Wall Permissible Minimum Wall Measurement Thickness Thickness Thickness Locations Locations Locations during each during each Inspection Inspection Period Period (See Notes (See Notes 3,
4,
- 5) 3, 4,
- 5)
NOTES:
(1) Containment surface areas requiring augmented examination are those identified in IWE-1240.
(2) Except as permitted in Note 4, the extent of examination shall be 100% for each inspection period until the areas remain essentially unchanged for three inspection periods. Such areas no longer require augmented examination in accordance with IWE-2420(c).
(3) Examinations need not be performed on portions of grids obstructed by structures, components, or permanent plant equipment. If more than 75% of any selected grid is obstructed, an alternate grid shall be selected at random for examination.
TABLE 1 EXAMINATION CATEGORY E-C, CONTAINMENT SURFACES REQUIRING AUGMENTED EXAMINATION (4) The following sampling plan may be used for surface areas requiring ultrasonic thickness measurement:
(a) Surface areas shall be divided into lots.
Each lot shall consist of areas subject to similar service conditions which have caused, or could cause, accelerated degradation and aging. Grids of uniform size not exceeding one foot square shall be selected at random from within; each lot.
The lot size shall be equal to the total number of grids within 100% of the lot area.
(b) The sample size shall be defined as the number of grids within each lot to be selected for examination. The sample size shall comply with Table 1 of U. S. NRC.Draft Regulatory Guide DG 1070 (September 1997) using a maximum number of defectives in sample equal to zero.
(c)
If the minimum wall thickness within each selected grid remains essentially unchanged for three consecutive inspection periods, the lot from which the sample was drawn no longer requires augmented examination in accordance with IWE-2420(c).
(5) If an ultrasonic thickness measurement of a selected grid within a lot reveals wall thickness loss exceeding the acceptance standard of IWE-3512.3, the entire lot shall be unacceptable, unless the remaining grids within the lot are examined and the entire lot accepted in accordance with IWE 3120.