ML042870598
| ML042870598 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 10/12/2004 |
| From: | Gramm R NRC/NRR/DLPM/LPD4 |
| To: | Edington R Nebraska Public Power District (NPPD) |
| Honcharik M, NRR/DLPM, 301-415-1774 | |
| References | |
| TAC MC2061, TAC MC2063, TAC MC2064 | |
| Download: ML042870598 (17) | |
Text
October 12, 2004 Mr. Randy K. Edington Vice President-Nuclear and CNO Nebraska Public Power District P.O. Box 98 Brownville, NE 68321
SUBJECT:
COOPER NUCLEAR STATION - RE: REQUESTS RI-17, RI-32, AND RI-33 FOR RELIEF FROM THE REQUIREMENTS OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) BOILER AND PRESSURE VESSEL CODE (CODE) (TAC NOS. MC2061, MC2063, AND MC2064)
Dear Mr. Edington:
By letter dated February 12, 2004, as supplemented by letter dated July 22, 2004, Nebraska Public Power District (the licensee) submitted requests for the use of alternatives to certain ASME Code Section XI requirements at Cooper Nuclear Station (CNS).
Pursuant to the regulation at Section 50.55a(g)(4)(iv) of Title 10 of the Code of Federal Regulations (10 CFR), the NRC staff approves the use of a later code edition and addenda for inservice inspection items as requested in RI-17. The proposed alternatives for relief requests RI-32 and RI-33 provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the use of relief requests RI-32 and RI-33 during the licensees third 10-year inservice inspection interval for CNS. The NRC staff's safety evaluation for RI-17, RI-32, and RI-33 is enclosed.
Sincerely,
/RA by M. Webb for Mr.Gramm/
Robert A. Gramm, Chief, Section 1 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-298
Enclosure:
Safety Evaluation cc w/encl: See next page
October 12, 2004 Mr. Randy K. Edington Vice President-Nuclear and CNO Nebraska Public Power District P.O. Box 98 Brownville, NE 68321
SUBJECT:
COOPER NUCLEAR STATION - RE: REQUESTS RI-17, RI-32, AND RI-33 FOR RELIEF FROM THE REQUIREMENTS OF THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) BOILER AND PRESSURE VESSEL CODE (CODE) (TAC NOS. MC2061, MC2063, AND MC2064)
Dear Mr. Edington:
By letter dated February 12, 2004, as supplemented by letter dated July 22, 2004, Nebraska Public Power District (the licensee) submitted requests for the use of alternatives to certain ASME Code Section XI requirements at Cooper Nuclear Station (CNS).
Pursuant to the regulation at Section 50.55a(g)(4)(iv) of Title 10 of the Code of Federal Regulations (10 CFR), the NRC staff approves the use of a later code edition and addenda for inservice inspection items as requested in RI-17. The proposed alternatives for relief requests RI-32 and RI-33 provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the use of relief requests RI-32 and RI-33 during the licensees third 10-year inservice inspection interval for CNS. The NRC staff's safety evaluation for RI-17, RI-32, and RI-33 is enclosed.
Sincerely,
/RA by M. Webb for Mr.Gramm/
Robert A. Gramm, Chief, Section 1 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-298
Enclosure:
Safety Evaluation cc w/encl: See next page DISTRIBUTION:
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10/8/04 10/12/04 OFFICIAL RECORD COPY
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST NOS. RI-17, RI-32, AND RI-33 NEBRASKA PUBLIC POWER DISTRICT COOPER NUCLEAR STATION DOCKET NO. 50-298
1.0 INTRODUCTION
By letter dated February 12, 2004 (Reference 1) and supplement dated July 22, 2004 (Reference 2), Nebraska Public Power District (the licensee, NPPD) requested relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI for Cooper Nuclear Station (CNS). Relief requests RI-17, RI-32, and RI-33 are applicable to the third 10-year inservice inspection (ISI) interval, which started on March 1, 1996 and will end on February 28, 2006.
2.0 REGULATORY EVALUATION
Section 50.55a(g)(4) of Title 10 of the Code of Federal Regulations (10 CFR) requires licensees to update their ISI program plan every 10 years using the latest edition and addenda of the ASME Code for ISI of Class 1, Class 2, and Class 3 components (including supports). The regulation at 10 CFR 50.55a(a)(3) states, in part, that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the applicant demonstrates that the proposed alternatives would provide an acceptable level of quality and safety. Accordingly, in preparing for its third ISI program plan, the licensee recognized the need for relief from some of the requirements in ASME Code,Section IX, 1989 Edition, No Addenda (Reference 3) as incorporated by reference in 10 CFR 50.55a. The ISI Code of record for CNS for the third 10-year ISI interval is Reference 3. The reliefs are requested pursuant to 10 CFR 50.55a(a)(3) and 10 CFR 50.55a(g)(4).
3.0 EVALUATION OF RELIEF REQUEST RI-17, REVISION 2 Eliminate disassembling pipe clamp or restraint to examine welded attachments. Examine to maximum extent possible in accordance with applicable Code requirements.
The Items for which Relief is Requested:
This relief request applies to the following Code classes in Reference 3:
1.
Code Class 1, Table IWB-2500-1, Examination Category B-H, Item Nos. B8.10, B8.20, B8.30, and B8.40, and Examination Category B-K-1, Item Nos. B10.10, B10.20, and B10.30.
2.
Code Class 2, Table IWC-2500-1, Examination Category C-C, Item Nos. C3.10, C3.20, C3.30, and C3.40.
3.
Code Class 3, Table IWD-2500-1, Examination Category D-A, Item Nos. D1.20 through D1.60, Examination Category D-B, Item Nos. D2.20 through D2.60, and Examination Category D-C, Item Nos. D3.20 through D3.60.
Code Requirement:
Reference 3 outlines the examination requirements for Examination Categories B-H, B-K-1, C-C, D-A, D-B, and D-C. The licensee is requesting relief from the examination requirements contained in these examination categories. The specific item numbers affected by this relief request are in Section 3.0 above.
The licensee stated in Reference 2 that Reference 3 will continue to be the applicable Code of record for Examination Category D-A, Item No. D1.10, Examination Category D-B, Item No.
D2.10, and Examination Category D-C, Item No. D3.10. These components are not part of this relief request.
Licensees Proposed Alternative (as stated in Reference 1):
NPPD will use ASME Section Xl, 1995 Edition, 1996 Addenda, for the examination and acceptance of Class 1, Class 2 and Class 3 welded attachments.
Licensees Basis for Relief (as stated in Reference 1):
In Revision 0 of Relief Request Rl-17 NPPD requested relief from removing piping clamps to achieve the required 100% examination coverage for integrally welded attachments (shear lugs). The NRC staff concluded that the proposed alternative, in conjunction with the reduction in number of integrally welded attachments examinations allowed by Code Case N-509, did not provide an acceptable level of quality and safety.
The relief request was denied. In Relief Request RI-17, Revision 1, NPPD requested relief from removing pipe clamps to achieve required examination coverage for four (4) integrally welded attachments. This relief request was granted with the condition that an additional integrally welded attachment be examined.
Revision 1 of RI-17 was submitted on April 23, 1998 and approved by the NRC on March 11, 1999. At that time 10CFR50.55(a) referenced ASME Section Xl, Division 1, and included addenda through the 1988 Addenda and editions through the 1989 Edition for Class 1, 2 and 3 components. The 1989 Edition did not contain any provisions to allow examination of integrally welded attachments without removing component support members. In the 1995 Edition, 1995 Addenda, Figures IWB-2500-15, IWC-2500-5 and IWD-2500-1 for welded attachments were modified to add the following note:
"Examination of surface areas may be limited to the portions of these areas that are accessible without removal of support members". The 1995 Edition through the 1996 Addenda of ASME Section Xl was approved for use in 10CFR50.55a(b)(2) on November 22, 1999 (after relief was granted for RI-17, Revision 1). The 1995 Edition, 1995 Addenda of ASME Section XI incorporates the examination percentages as given in Code Case N-509. These provisions incorporated in the 1995 Edition, 1995 Addenda have remained in the code through the 2001 Edition, 2003 Addenda. Therefore, NPPD requests approval to use the 1995 Edition, 1996 Addenda of ASME Section XI for the examination of welded attachments. The acceptance criteria of the 1995 Edition, 1996 Addenda of Section XI will also be used since it is a related requirement.
Approval is requested under 10CFR50.55a(g)(4)(iv) to use ASME Section XI, 1995 Edition, 1996 Addenda, for the examination and acceptance of Class 1, Class 2 and Class 3 welded attachments.
Evaluation:
The Code of record for CNS is Reference 3. The applicable examination requirements are specified in Table IWB-2500-1, Examination Categories B-H and B-K-1; Table IWC-2500-1, Examination Category C-C; and Table IWD-2500-1, Examination Categories D-A, D-B, and D-C (excluding pressure testing). The licensee has proposed to use the applicable examination requirements and acceptance criteria in the 1995 Edition, 1996 Addenda, of the ASME Code,Section XI, as an alternative to the requirements in the Code of record.
A)
Class 1 components examination requirements:
The licensee stated in Reference 2 that Examination Category B-H (Integral Attachments for Vessels) in the Code of record was condensed into Item No. B10.10 in Examination Category B-K in the 1995 Edition, 1996 Addenda. Examination Category B-H was deleted in the 1995 Edition, 1996 Addenda, of the Code. Table IWB-2500-1, Examination Category B-K-1 in the Code of record was retitled in the 1995 Edition, 1996 Addenda, as: "Examination Category B-K, Welded Attachments for Vessels, Piping, Pumps, and Valves."
B)
Class 2 components examination requirements:
The subject components in Table IWC-2500-1, Examination Category C-C in the Code of record remained unchanged in the 1995 Edition, 1996 Addenda. Table IWC-2500-1, Examination Category C-C in the proposed alternative was retitled as: "Welded Attachments for Vessels, Piping, Pumps, and Valves."
C) Class 3 components examination requirements:
The licensee stated in Reference 2 that Examination Categories D-A, D-B, and D-C in the Code of record were combined into one category, Examination Category D-A, in the 1995 Edition, 1996 Addenda. The description of the components in these examination categories (under "Parts Examined") changed from support types in the Code of record to type of components (vessels, piping, pumps and valves) in the 1995 Edition, 1996 Addenda. The licensee affirmed that these changes do not alter the total number of integral attachments under the scope of Section XI of the ASME Code.
The NRC staff compared the examination requirements and acceptance standards in the 1995 Edition, 1996 Addenda, for the subject items against the respective items in the Code of record and concludes that they remained essentially unchanged. The only major changes are the notes added in Figure Nos. IWB-2500-15, IWC-2500-5, and IWD-2500-1, which state that:
"Examination of surface areas may be limited to the portions of these areas that are accessible without removal of support members." The NRC staff endorsed these notes.
The NRC staff finds the examination requirements in Table IWB-2500-1, Examination Category B-K, Table IWC-2500-1, Examination Category C-C, and Table IWD-2500-1, Examination Category D-A in the 1995 Edition, 1996 Addenda, are more stringent than the Code of record.
Specifically, the extent and frequency of examination requirements are more conservative because the 1995 Edition, 1996 Addenda, added a requirement that examination should be performed whenever component support member deformation is identified during operation, refueling, maintenance, examination, or testing.
The NRC staff finds that the related examination requirements for Examination Categories B-K, C-C, and D-A in the 1995 Edition, 1996 Addenda, meet the respective requirements in the Code of record. Therefore, the staff finds the proposed alternative for the Class 1, 2, and 3 subject components to be acceptable.
4.0 EVALUATION OF RELIEF REQUEST RI-32 CNS will use a depth sizing requirement of 0.15-inch root mean square (RMS) as an acceptance criteria in lieu of the requirement in Subparagraph 3.2(c) of Supplement 4 of Appendix VIII.
The Items for which Relief is Requested:
This relief request applies to ASME Code,Section XI, Class 1, Table IWB-2500-1, Examination Category B-F, Item No. B5.10.
Code Requirement:
Appendix VIII, Supplement 4 to the 1995 Edition, 1996 Addenda, of the ASME Code,Section XI, specifies the performance demonstration requirements for procedures, equipment, and personnel used to detect and size flaws on the clad/base metal interface of the reactor vessel. Specifically, subparagraph 3.2(c) requires that performance demonstration results reported by the candidate, when plotted on a two-dimensional plot with the depth estimated by ultrasonics plotted along the ordinate and the true depth plotted along the abscissa, satisfy the following statistical parameters:
1.
Slope of the linear regression line is not less than 0.7; 2.
The mean deviation of flaw depth is less than 0.25 inches (in.); and 3.
Correlation coefficient is not less than 0.70.
Licensees Proposed Alternative (as stated in Reference 1):
NPPD will use 0.15 inch RMS as an acceptance criteria rather than Subparagraph 3.2(c) of Supplement 4 of Appendix VIII.
Licensees Basis for Relief (as stated in Reference 1):
The linear regression line (Subparagraph 3.2(c)(1)) is the difference between measured and true value plotted along a through-wall thickness. For Supplement 4 performance demonstration, a linear regression line of the data is not applicable because the performance demonstrations are performed on test specimens with flaws located in the inner 15 percent of wall thickness. The differences between measured versus true value produce a tight grouping of results which resemble a shotgun pattern. The slope of a regression line from such data is extremely sensitive to small variations, thus making the parameter of Subparagraph 3.2(c)(1) a poor and inappropriate acceptance criteria. The second parameter, 3.2(c)2, pertains to the mean deviation of the flaw depth. The value used in the Code is too lax with respect to evaluating flaw depths within the inner 15 percent of wall thickness. Therefore, the Electric Power Research Institute Performance Demonstration Initiative Program proposes to use the more appropriate criterion of 0.15 inch Root Mean Square (RMS) of 10CFR50.55a(b)(2)(xv)(C)(1), which modifies Subparagraph 3.2(a), as the acceptance criterion. The third parameter, 3.2(c)(3),
pertains to a correlation coefficient. The value of the correlation coefficient in Subparagraph 3.2(c)(3) is inappropriate for this application since it is based on the linear regression from Subparagraph 3.2(c)(1).
Relief is requested in accordance with 10CFR50.55a(a)(3)(i).
Evaluation:
The U.S. nuclear utilities created the Performance Demonstration Initiative (PDI) to implement performance demonstration requirements contained in Appendix VIII of Section XI of the ASME Code. To this end, PDI has developed a performance demonstration program for qualifying ultrasonic testing (UT) equipment, procedures, and personnel. During the development of the performance demonstration for Supplement 4, PDI determined that the Code criteria for flaw sizing was unworkable.
PDI was aware of the inappropriateness of Subparagraph 3.2(c) early in the development of its program. It brought the issue before the appropriate ASME committee, which formalized eliminating the use of Supplement 4, Subparagraph 3.2(c) in Code Case N-622, approved on February 26, 1999. The NRC staff representatives participated in the discussions and consensus process of the Code Case.
As a result of the inappropriateness of the requirements in Subparagraph 3.2(c), NRC has proposed an amendment to the existing requirements in 10 CFR 50.55a(b)(2)(xv)(C)(1). As published in the Federal Register on January 7, 2004 (69 FR 879), the proposed amendment will revise, in part, the existing regulation to specify that the flaw depth sizing provisions in Subparagraph 3.2(c) of Supplement 4 to Appendix VIII are not applicable when Appendix VIII is implemented in accordance with the requirements outlined in 10 CFR 50.55a(b)(2)(xv). The revision is needed to correct an oversight that the flaw depth sizing provisions in Subparagraph 3.2(c) of Supplement 4 to Appendix VIII also do not apply when using the flaw depth sizing provisions specified in 10 CFR 50.55a(b)(2)(xv)(C)(1).
Based on the above, the NRC staff finds that the use of the statistical parameters outlined in Subparagraph 3.2(c) is inappropriate, and the proposed alternative to use the RMS value of 10 CFR 50.55a(b)(2)(xv)(C)(1), namely 0.15-inch RMS, which modifies the criterion of Appendix VIII, Supplement 4, Subparagraph 3.2(a), in lieu of Subparagraph 3.2(c), will provide an acceptable level of quality and safety.
5.0 EVALUATION OF RELIEF REQUEST RI-33 Alternatives are proposed to the qualification requirements for dissimilar metal piping welds of ASME Section Xl, 1995 Edition, 1996 Addenda, Appendix VIII, Supplement 10.
The Items for which Relief is Requested:
This relief request applies to ASME Code,Section XI, Class 1, Table IWB-2500-1, Examination Category B-F, Item No. B5.10.
Code Requirement:
Appendix VIII, Supplement 10 to the 1995 Edition, 1996 Addenda, of the ASME Code,Section XI specifies the performance demonstration requirements for equipment, procedures, and personnel used to detect and size flaws on dissimilar metal piping welds. The licensee requested relief from the following Supplement 10 requirements:
Item 1-Paragraph 1.1(b) states, in part, that pipe diameters within a range of 0.9 to 1.5 times a nominal diameter shall be considered equivalent.
Item 2-Paragraph 1.1(d) states that all flaws in the specimen set shall be cracks.
Item 3-Paragraph 1.1(d)(1) states that at least 50 percent of the cracks shall be in austenitic material. At least 50 percent of the cracks in austenitic material shall be contained wholly in weld or buttering material. At least 10 percent of the cracks shall be in ferritic material. The remainder of the cracks may be in either austenitic or ferritic material.
Item 4-Paragraph 1.2(b) states, in part, that the number of unflawed grading units shall be at least twice the number of flawed grading units.
Item 5-Paragraphs 1.2(c)(1) and 1.3(c) state, in part, at least 1/3 of the flaws, rounded to the next higher whole number, shall have depths between 10 percent and 30 percent of the nominal pipe wall thickness. Paragraph 1.4(b) distribution table requires 20 percent of the flaws to have depths between 10 percent and 30 percent.
Item 6-Paragraph 2.0 first sentence states that the specimen inside surface and identification shall be concealed from the candidate.
Item 7-Paragraph 2.2(b) states, in part, the regions containing a flaw to be sized shall be identified to the candidate.
Item 8-Paragraph 2.2(c) states, in part, that for a separate length sizing test, the regions of each specimen containing a flaw to be sized shall be identified to the candidate.
Item 9-Paragraph 2.3(a) states that for the depth sizing test, 80 percent of the flaws shall be sized at a specific location on the surface of the specimen identified to the candidate.
Item 10- Paragraph 2.3(b) states that for the remaining flaws, the regions of each specimen containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.
Item 11-Table VIII-S2-1 provides the false call criteria when the number of unflawed grading units is at least twice the number of flawed grading units.
Licensees Proposed Alternative (as stated in Reference 1):
The licensee proposed the following requirements to selected provisions of the ASME Code,Section XI, Appendix VIII, Supplement 10. The proposed alternative, as implemented through the PDI Program, is attached to the licensees submittal. It was incorporated in ASME Code Case N-695, which was approved by ASME on May 21, 2003.
In lieu of the requirements of ASME Section XI, 1995 Edition, 1996 Addenda, Appendix VIII, Supplement 10, the proposed alternative shall be used. A copy of the proposed alternative is contained in Table RI-33-1.
Licensees Basis for Relief (as stated in Reference 1):
Item 1 - Proposed alternative to Paragraph 1.1(b):
The specimen set shall include the minimum and maximum pipe diameters and thicknesses for which the examination procedure is applicable. Pipe diameters within 1/2 in. (13 mm) of the nominal diameter shall be considered equivalent. Pipe diameters larger than 24 in. (610 mm) shall be considered to be flat. When a range of thicknesses is to be examined, a thickness tolerance of +25% is acceptable.
Technical Basis - The change in the minimum pipe diameter tolerance from 0.9 times the diameter to within 1/2 inch of the nominal diameter provides tolerances more in line with industry practice. Though the alternative is less stringent for small pipe diameters they typically have a thinner wall thickness than larger diameter piping. A thinner wall thickness results in shorter sound path distances that reduce the detrimental effects of the curvature. This change maintains consistency between Supplement 10 and the recent revision to Supplement 2.
Item 2 - Proposed alternative to Paragraph 1.1(d):
At least 60% of the flaws shall be cracks, the remainder shall be alternative flaws.
Specimens with Intergranular Stress Corrosion Cracking (IGSCC) shall be used when available. Alternative flaws, shall meet the following requirements:
(1) Alternative flaws, if used, shall provide crack-like reflective characteristics and shall only be used when implantation of cracks would produce spurious reflectors that are uncharacteristic of service-induced flaws.
(2) Alternative flaw mechanisms shall have a tip width no more than 0.002 in. (.05 mm).
Note, to avoid confusion the proposed alternative modifies instances of the term "cracks" or "cracking" to the term "flaws" because of the use of alternative flaw mechanisms.
Technical Basis - As illustrated below, implanting a crack requires excavation of the base material on at least one side of the flaw. While this may be satisfactory for ferritic materials, it does not produce a useable axial flaw in austenitic materials because the sound beam, which normally passes only through base material, must now travel through weld material on at least one side, producing an unrealistic flaw response. In addition, it is important to preserve the dendritic structure present in field welds that would otherwise be destroyed by the implantation process. To resolve these issues, the proposed alternative allows the use of up to 40% fabricated flaws as an alternative flaw mechanism under controlled conditions. The fabricated flaws are isostatically compressed which produces ultrasonic reflective characteristics similar to tight cracks.
Item 3 - Proposed alternative to Paragraph 1.1(d)(1):
At least 80% of the flaws shall be contained wholly in weld or buttering material. At least one and no more than 10% of the flaws shall be in ferritic base material. At least one and no more than 10% of the flaws shall be in austenitic base material.
Technical Basis - Under the current Code, as few as 25% of the flaws are contained in austenitic weld or buttering material. Recent experience has indicated that flaws contained within the weld are the likely scenarios. The metallurgical structure of austenitic weld material is ultrasonically more challenging than either ferritic or austenitic base material. The proposed alternative is therefore more challenging than the current Code.
Item 4 - Proposed alternative to Paragraph 1.2(b):
Personnel performance demonstration detection test sets shall be selected from Table VIII-S10-1. The number of unflawed grading units shall be at least 1-1/2 times the number of flawed grading units.
Technical Basis - Table S10-1 provides a statistically based ratio between the number of unflawed grading units and the number of flawed grading units. The proposed alternative reduces the ratio to 1.5 times to reduce the number of test samples to a more reasonable number from the human factors perspective. However, the statistical basis used for screening personnel and procedures is still maintained at the same level with competent personnel being successful and less skilled personnel being unsuccessful.
The acceptance criteria for the statistical basis are in Table VIII-S10-1.
Item 5 - The proposed alternative to the flaw distribution requirements of Paragraph 1.2(c)(1) (detection) and 1.3(c) (length) is to use the Paragraph 1.4(b) (depth) distribution table (see below) for all qualifications.
Flaw Depth Minimum
(% Wall Thickness)
Number of Flaws 10-30%
20%
31-60%
20%
61-100%
20%
Technical Basis - The proposed alternative uses the depth sizing distribution for both detection and depth sizing because it provides for a better distribution of flaw sizes within the test set. This distribution allows candidates to perform detection, length, and depth sizing demonstrations simultaneously utilizing the same test set. The requirement that at least 75% of the flaws shall be in the range of 10 to 60% of wall thickness provides an overall distribution tolerance yet the distribution uncertainty decreases the possibilities for testmanship that would be inherent to a uniform distribution. It must be noted that it is possible to achieve the same distribution utilizing the present requirements, but it is preferable to make the criteria consistent.
Item 6 - Proposed alternative to Paragraph 2.0 first sentence:
For qualifications from the outside surface, the specimen inside surface and identification shall be concealed from the candidate. When qualifications are performed from the inside surface, the flaw location and specimen identification shall be obscured to maintain a "blind test."
Technical Basis - The current Code requires that the inside surface be concealed from the candidate. This makes qualifications conducted from the inside of the pipe (e.g.,
PWR [pressurized-water reactor] nozzle to safe end welds) impractical. The proposed alternative differentiates between ID [inside diameter] and OD [outside diameter]
scanning surfaces, requires that they be conducted separately, and requires that flaws be concealed from the candidate. This is consistent with the recent revision to Supplement 2.
Items 7 and 8 - Proposed alternatives to Paragraph 2.2(b) and 2.2(c):
"... containing a flaw to be sized may be identified to the candidate."
Technical Basis - The current Code requires that the regions of each specimen containing a flaw to be length sized shall be identified to the candidate. The candidate shall determine the length of the flaw in each region (Note, that length and depth sizing use the term "regions" while detection uses the term "grading units" - the two terms define different concepts and are not intended to be equal or interchangeable). To ensure security of the samples, the proposed alternative modifies the first "shall" to a "may" to allow the test administrator the option of not identifying specifically where a flaw is located. This is consistent with the recent revision to Supplement 2.
Items 9 and 10 - Proposed alternative to Paragraph 2.3(a) and 2.3(b):
"... regions of each specimen containing a flaw to be sized may be identified to the candidate."
Technical Basis - The current Code requires that a large number of flaws be sized at a specific location. The proposed alternative changes the "shall" to a "may" which modifies this from a specific area to a more generalized region to ensure security of samples. This is consistent with the recent revision to Supplement 2. It also incorporates terminology from length sizing for additional clarity.
Item 11 - The proposed alternative modifies the acceptance criteria of Table VIII-S2-1 as follows:
Technical Basis - The proposed alternative is identified as new Table S10-1 above. It was modified to reflect the reduced number of unflawed grading units and allowable false calls. As a part of ongoing Code activities, Pacific Northwest National Laboratory has reviewed the statistical significance of these revisions and offered the revised Table S10-1.
Pursuant to 10CFR50.55a(a)(3)(i), approval is requested to use the proposed alternative described herein and outlined in Table RI-33-1.
Evaluation:
Since 2001, PDI has been developing a program to implement Supplement 10 to Appendix VIII of Section XI of the ASME Code. During the development process, certain aspects of Supplement 10 were identified as difficult or impossible to implement. To overcome the implementation difficulties, PDI researched, tested, and demonstrated the effectiveness of an alternative to selected paragraphs of the Code. PDI representatives presented the alternative before the appropriate ASME committees, which formalized the alternative in Code Case N-695, approved on May 21, 2003. The NRC staff representatives on these committees participated in the consensus process and joined with the industry in approving Code Case N-695. The differences between the Code and the PDI program are discussed below.
Paragraph 1.1(b):
The Code requirement of 0.9 to 1.5 times the nominal diameter are equivalent was established for a single nominal diameter. When applying the Code-required tolerance to a range of diameters, the tolerance rapidly expands on the high side. Under the current Code requirements, a 5-inch nominal diameter pipe would be equivalent to a range of 4.5-inch to 7.5-inch diameter pipe. Under the proposed PDI guidelines, the equivalent range would be reduced to a range of 4.5-inch to 5.5-inch nominal diameter pipe. With current Code requirements, a 16-inch nominal diameter pipe would be equivalent to a range of 14.4-inch to 24-inch diameter pipe. The proposed alternative would significantly reduce the equivalent range to between 15.5-inch and 16.5-inch diameter pipe. The difference between the Code and the proposed PDI program for diameters less than 5 inches is not significant because of shorter metal path and beam spread associated with smaller diameter piping. The NRC staff considers the proposed alternative to be more conservative overall than current Code requirements. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 1.1(d):
The Code requires all flaws to be cracks. Manufacturing test specimens containing cracks free of spurious reflections and telltale indicators is extremely difficult in austenitic material. To overcome these difficulties, PDI developed a process for fabricating flaws that produce UT acoustic responses similar to the responses associated with real cracks. PDI presented its process for discussion at public meetings held June 12 through June 14, 2001, and January 31 through February 2, 2002, at the Electric Power Research Institute (EPRI) non-destructive examination center in Charlotte, NC. The NRC staff attended these meetings and determined that the process parameters used for manufacturing fabricated flaws resulted in acceptable acoustic responses. PDI is selectively installing these fabricated flaws in specimen locations that are unsuitable for real cracks. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 1.1(d)(1):
The Code requires that at least 50 percent of the flaws be contained in austenitic material and 50 percent of the flaws in the austenitic material shall be contained fully in weld or buttering material. This means that at least 25 percent of the total flaws must be located in the weld or buttering material. Field experience shows that flaws identified during ISI of dissimilar metal welds are more likely to be located in the weld or buttering material. The grain structure of austenitic weld and buttering material represents a much more stringent ultrasonic scenario than that of a ferritic or austenitic base material. Flaws made in austenitic base material are difficult to create free of spurious reflectors and telltale indicators. The proposed alternative of 80 percent of the flaws in the weld metal or buttering material provides a challenging testing scenario reflective of field experience and minimizes testmanship associated with telltale reflectors common to placing flaws in austenitic base material. The NRC staff considers the proposed alternative to be more conservative overall than current Code requirements. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 1.2(b) and Table VIII-S10-1:
The Code requires that detection sets meet the requirements of Table VIII-S2-1 which specifies the minimum number of flaws in a test set to be 5 with 100 percent detection. The current Code also requires the number of unflawed grading units to be two times the number of flawed grading units. The proposed alternative, as shown in Table VIII-S10-1, would follow the detection criteria of the table beginning with a minimum number of flaws in a test set starting at 10, and reducing the number of unflawed grading units to one and a half times the number of flawed grading units, while maintaining the same statistical design basis as the Code. The proposed alternative paragraphs satisfy the pass/fail objective established for the Appendix VIII performance demonstration acceptance criteria. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 1.2(c)(1) and Paragraph 1.3(c):
For detection and length sizing, the Code requires at least one third of the flaws to be located between 10 and 30 percent through the wall thickness and one third located at greater than 30 percent through the wall thickness. The remaining flaws would be located randomly throughout the wall thickness. The proposed alternative sets the distribution criteria for detection and length sizing to be the same as the depth sizing distribution, which stipulates that at least 20 percent of the flaws be located in each of the increments of 10 to 30 percent, 31 to 60 percent, and 61 to 100 percent. At least 75 percent of the flaws shall be in the range of 10 to 60 percent of the wall thickness, with the remaining flaws located randomly throughout the pipe thickness. With the exception of the 10 to 30 percent increment, the proposed alternative is a subset of the current Code requirements. The 10 to 30 percent increment would be in the subset if it contained at least 30 percent of the flaws. The change simplifies assembling test sets for detection and sizing qualifications, and is more indicative of conditions in the field. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 2.0:
The Code requires the specimen inside surface to be concealed from the candidate. This requirement is applicable for test specimens used for qualifications performed from the outside surface. With the expansion of Supplement 10 to include qualifications from the inside surface, the inside surface must be accessible while maintaining the specimen integrity. The proposed alternative requires that flaws and specimen identifications be obscured from the candidates, thus maintaining blind test conditions. The NRC staff considers this to be consistent with the intent of ASME Code requirements. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 2.2(b) and 2.2(c):
The Code requires that the location of flaws added to the test set for length sizing shall be identified to the candidate. The proposed alternative is to make identifying the location of additional flaws an option. This option provides an additional element of difficulty to the testing process because the candidate would be expected to demonstrate the skill of detecting and sizing flaws over an area larger than a specific location. The NRC staff considers the proposed alternative to be more conservative than current Code requirements. The staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
Paragraph 2.3(a) and 2.3(b):
In Paragraph 2.3(a), the Code requires that 80 percent of the flaws be sized in a specific location that is identified to the candidate. The proposed alternative allows identification of the specific location to be an option. This permits detection and depth sizing to be conducted separately or concurrently. In order to maintain a blind test, the location of flaws can not be shared with the candidate. For depth sizing that is conducted separately, allowing the test administrator the option of not identifying flaw locations makes the testing process more challenging. The NRC staff considers the proposed alternative to be more conservative than current Code requirements. The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
In Paragraph 2.3(b), the Code also requires that the location of flaws added to the test set for depth sizing shall be identified to the candidate. The proposed alternative is to make identifying the location of additional flaws an option. This option provides an additional element of difficultly to the testing process because the candidate would be expected to demonstrate the skill of finding and sizing flaws in an area larger than a specific location. The NRC staff considers the proposed alternative to be more conservative than current Code requirements.
The NRC staff finds that the proposed alternative will provide an acceptable level of quality and safety and, therefore, is acceptable.
6.0 CONCLUSION
S Based upon review of the information provided by the licensee in support of its relief request RI-17, Revision 2, the NRC staff concludes that the related examination requirements for Examination Category B-K, C-C, and D-A welded attachments set forth in the 1995 Edition, 1996 Addenda, of the ASME Code,Section XI meet the respective requirements in the Code of record. The licensee addressed the associated parts of the Code in Reference 2. The 1995 Edition, 1996 Addenda, of the ASME Code was approved for use in 10 CFR 50.55a(b)(2) on November 22, 1999. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the staff authorizes the proposed alternative for the requested components at CNS during the third 10-year ISI interval on the basis that it provides an acceptable level of quality and safety.
Based upon review of the information provided by the licensee in support of its relief request RI-32, the NRC staff concludes that the proposed alternative to Subparagraph 3.2(c) of Supplement 4 to Appendix VIII will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the staff authorizes the use of the proposed alternative at CNS during the third 10-year ISI interval.
Based upon review of the information provided by the licensee in relief request RI-33, the NRC staff concludes that the licensees proposed alternative to use Supplement 10, as administered by the EPRI PDI program, provides an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the staff authorizes the use of the proposed alternative at CNS during the third 10-year ISI interval.
All other requirements of the ASME Code,Section XI, for which relief has not been specifically requested remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
7.0 REFERENCES
1.
Letter from R. Edington (NPPD) to NRC, Inservice Inspection Relief Requests PR-03, RC-06, RC-07, RI-17, RI-31, RI-32 and RI-33, February 12, 2004. ADAMS Accession No. ML040490589.
2.
Letter from R. Edington (NPPD) to NRC, Response to Request for Additional Information Regarding Relief Request RI-17 and RI-31, July 22, 2004. ADAMS Accession No. ML042100268.
3.
Section XI of ASME Code, Rules for Inservice Inspection of Nuclear Power Plant Components, 1989 Edition, No Addenda.
Principal Contributor: R. Rodriguez Date: October 12, 2004
June 2004 Cooper Nuclear Station cc:
Mr. William J. Fehrman President and Chief Executive Officer Nebraska Public Power District 1414 15th Street Columbus, NE 68601 Mr. Clay C. Warren Vice President of Strategic Programs Nebraska Public Power District 1414 15th Street Columbus, NE 68601 Mr. John R. McPhail, General Counsel Nebraska Public Power District P. O. Box 499 Columbus, NE 68602-0499 Mr. Paul V. Fleming Licensing Manager Nebraska Public Power District P.O. Box 98 Brownville, NE 68321 Mr. Michael J. Linder, Director Nebraska Department of Environmental Quality P. O. Box 98922 Lincoln, NE 68509-8922 Chairman Nemaha County Board of Commissioners Nemaha County Courthouse 1824 N Street Auburn, NE 68305 Ms. Cheryl K. Rogers, Program Manager Nebraska Health & Human Services System Division of Public Health Assurance Consumer Services Section 301 Centennial Mall, South P. O. Box 95007 Lincoln, NE 68509-5007 Mr. Ronald A. Kucera, Director of Intergovernmental Cooperation Department of Natural Resources P.O. Box 176 Jefferson City, MO 65102 Senior Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 218 Brownville, NE 68321 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Jerry Uhlmann, Director State Emergency Management Agency P. O. Box 116 Jefferson City, MO 65101 Chief, Radiation and Asbestos Control Section Kansas Department of Health and Environment Bureau of Air and Radiation 1000 SW Jackson Suite 310 Topeka, KS 66612-1366 Mr. Daniel K. McGhee Bureau of Radiological Health Iowa Department of Public Health 401 SW 7th Street Suite D Des Moines, IA 50309 Mr. Scott Clardy, Director Section for Environmental Public Health P.O. Box 570 Jefferson City, MO 65102-0570 June 2004 Jerry C. Roberts, Director of Nuclear Safety Assurance Nebraska Public Power District P.O. Box 98 Brownville, NE 68321