ML20216J779
| ML20216J779 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 04/15/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20216J772 | List: |
| References | |
| NUDOCS 9804210482 | |
| Download: ML20216J779 (12) | |
Text
r3 u n g
p UNITED STATES NUCLEAR REGULATORY COMMISSION f
WASHINGTON, D.C. 20566-0001 o,,s...../
l SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FIRST AND SECOND TEN YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN REQUESTS FOR RELIEF 11R-49 THROUGH 11R-49 AND 12R-21 WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NO. 50-482
1.0 INTRODUCTION
The Technical Specifications (TS) for the Wolf Creek Generating Station, state that the inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel (B&PV) Code and applicable addenda as required by 10 CFR 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 attematives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed attematives 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 pre-service 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 inservice examination of components and system pressure tests conducted during the first ten-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) twelve 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 the Wolf Creek Generating Station, first ten-year inservice inspection (ISI) interval is the 1980 Edition through Winter 1981 Addenda and for the second ISI intervals of the 1989 Edition.
Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose attemative 9804210482 980415 PDR ADOCK 05000402 O
. requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
l By letter dated May 23,1997, the licensee submitted Requests for Relief Nos.11R-46 through
' 11R-49 associated with its First 10-Year Interval inservice inspection (ISI) Program Plan and Request for Relief No.12R-21 associated with its Second 10-Year interval ISI Program Plan for Wolf Creek Generating Station.
2.0 EVALUATION
' The staff, with technical assistance from its contractor, the Idaho National Engineering and Environmental Laboratory (INEEL), has evaluated the information provided by the licensee in l
support of its First 10-Year interval inservice inspection (ISI) Program Plan Requests for Relief l
Nos.11R-46 through 11R-49 and Second 10-Year interval ISI Program Plan Request for Relief i
No.12R-21 for Wolf Creek Generating Station. Based on the results of the review, the staff adopts the contractor's conclusions and recommendations presented in the attached Technical Letter Report (TLR).
Request for Relief 11R 46: Section XI, Examination Category B-J, item B9.11, Accumulator l
Safety injection Valve-to-Pipe Circumforential Weld (First interval) requires 100% surface and volumetric examination, as defined by Figure IWB-2500-8, for Class 1 circumferential welds 4-inch nominal pipe size (NPS) atJ larger.
The licensee requested pursuant to 10 CFR 50.55a(g)(5)(iii), relief from the volumetric examination coverage requirements defined in ASME Section XI, Figure IWB-2500-8, i.
i Examination Volume C-D E-F for the Class 1 Accumulator Safety injection Valve-to-pipe Weld -
As stated below the licensee has not proposed an altemative, but intends to maximize the examination through best effort:
"None. Extended angle beam path ultrasonic techniques and higher angled beams (70*)
were utilized to obtain the maximum coverage possible."
l The Code requires 100% surface and volumetric examinations of Class 1 circumferential pressure-retaining pipe wolds greater than or equal to 4-inch NPS. However, geometry, weld configuration, and metallurgical properties restrict coverage and preclude 100% volumetric examination of accumulator safety injection valve-to-6-inch pipe Wold EP-02-F021. The volumetric examination is, therefore, impractical to perform to the extent required by the Code.
To meet the Code requirements, the weld joint would have to be redesigned and modified.
Imposition of this requirement would result in a burden on the licensee.
The licensee performed the Code-required two-direction axial scan on approximately 28.6% of the required weld volume. Seventy-two percent of the required weld volume received an axial scan in at least one direction. In addition, the weld volume was examined with circumferential scans in both beam directions and the Code-required 100% surface examination was performed.
The combination of the volumetric examination to the extent practical, complete surface examination, VT-2 visual examination as required by the Code, and examination of other Examination Category B-J welds assures that existing pattoms of degradation would have been
3 detected. As a result, reasonable assurance of the structuralintegrity of the subject weld has been provided. Therefore, the licensee's Request for Relief No.11R-46 is granted pursuant to 10 CFR 50.55a(g)(6)(i).
Request for Relief 11R 47: Section XI, Examination Category C-F, item C5.21, Accumulator Safety injection Valve-to-Pipe Wold (First Interval) requires volumetric and surface examination, as defined by Figure IWC-2500-7, for Class 2 circumferential pipe welds greater than %-inch nominal wall thickness.
The licensee requested pursuant to 10 CFR 50.55a(g)(5)(iii), relief from performing the volumetric exam'5ation to the extent required by the Code for accumulator safety injection valve to 10-inch pipe Wold EP-02-FW303.
As stated below the licensee has not proposed an attemative, but intends to maximize the examination through best effort:
"None. Extended angle beam path ultrasonic techniques and higher angled beams (70')
were utilized to obtain the maximum coverage possible."
The Code requires 100% surface and volumetric examination of the subject pressure-retaining Class 2 circumferential pipe weld. However, geometry, weld configuration, and metallurgical properties restrict coverage and preclude 100% volumetric examination of accumulator safety injection valve-to-10-inch pipe Weld EP-02-FW303. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the weld joint would have to be redesigned and modified. Imposition of this requirement would result in a burden on the licensee.
The licensee performed the Code-required two-direction axial sca,n on approximately 34.4% of the required weld volume. The remaining portion of the wold volume received an axial scan in at i
least one direction. In addition, the wold received full volumetric examination from the i
circumferential scans in both beam directions and the Code-required 100% surface examination.
The combination of the volumetric examination to the extent practical, complete surface examination, VT-2 visual examination as required by the Code, and examination of other Examination Category B-J welds assures that existing pattems of degradation would have been detected. As a result, reasonable assurares of the structuralintegrity of the subject weld has been provided. Therefore, the licensee's Request for Relief No. IR-47 is granted pursuant to 10 CFR 50.55a(g)(6)(i).
Request for Relief 11R 48: Section XI, Examination Category B-A, items B1.21 and B1.22 I
requires 100% volumetric examination of the accessible length of all circumferential and meridional head welds, as defined by Figure IWB-2500-3.
NOTE: This request was submitted, pursuant to 10 CFR 50.55a(g)(5)(iii), in regard to the ASME Section XI requirements for Examination Category B-A, item B1.12, RPV longitudinal shell welds.
However, while a request under 10 CFR 50.55a(g)(5)(iii) is acceptable for ASME requirements deemed impractical, it is not allowed under 10 CFR 50.55a(g)(6)(ii)(A), Augmented examination of reactor vessel. Furthermore, since all existing requests for relief were revoked by the i
augmented rule, it is not appropriate to address the current request prior to the augmented rule being satisfied. Therefore, evaluation of the item B1.12 welds (Weld Nos.1-RV-101-122A, B, C, and D) in this relief request will be deferred until the licensee has satisfied the regulations for the augmented reactor vessel examination.
. Pursuent to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code on the following RPV welds, included in the table below is an estimate of the composite Code-required volume (CRV) examined.
B1.12 1-RV-101-122B 69.9 %
B1.12 1-RV-101-122C 74.4 %
B1.21 1-RV-101-141*
65.3 %
i B1.21 1-RV 102-151*
48.2 %
B1.22 1-RV-101-154A 74.8 %
t i
B1.22 1-RV-101-154B 74.8 %
B1.22 1-RV-101-154C 74.8 %
1 B1.22 1-RV-101-154D 74.8 %
i l
- in the SER dated November 9,1987, relief was granted for Wolds 1-RV-101-141 and 1-RV 102-151 based on j
the licensee's assumphon that approximately 90% of the CRV could be exammed. As indcated by this relief request, actual exammaton volumes achieved are less then ongmeNy anecipated.
As stated below the licensee has not propsed an altomative, but intends to maximize the examination through best effort:
"No additiona! volumetric examinations will be performed. The RPV welds have been examined to the maximum extent practical."
"An additional 70' angle beam examination was performed for near surface (ID) l l
coverage."
The Code requires 100% volumetric examination of the accessible length of all RPV head welds during the first inspection interval. However, physical limitations inside the RPV restrict coverage and preclude 100% volumetric examination of the RPV bottom head circumferential and meridional welds listed above. For circumferential head Wold 1-RV-101-141 (item B1.21), six core support lugs obstruct examination. For circumferential head Wold 1-RV-102-151 (Item B1.21),29 of the 58 bottom mounted instrumentation (BMI) tubes interfere with scan coverage.
For meridional head Welds 1-RV-101-154A, B, C, and D (item B1.22), limitations include the core support lugs and BMI tubes. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To satisfy the Code requirements, design modifications to the l
RPV are necessary to allow access for complete examination. Imposition of this requirement j
would result in a burden on the licensee.
. The licensee examined a significant portion of these RPV welds. A composite Code-required examination of 48.2% of the weld volume for circumferential head Weld 1-RV-102-151,65.3% for circumferential head Wold 1-RV-101-141, and 74.8% for each of the four meridional head Welds 1-RV-101-154A, B, C, and D has been completed. The licensee also performed an additional
' 70' angle beam examination for near-surface inside diameter coverage. These examinations would have detected existing pattoms of degradation and have provided reasonable assurance of the RPV's structuralintegrity.
Based on the impracticality of meeting the Code requirements, and the reasonable assurance of structural integrity provided by the examinations that are being performed, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the first 10-year interval examinations on item B1.21 and B1.22 welds. For item B1.12 circumferential shell welds, the evaluation of any relief request will be deferred until the augmented RPV examination requirements in the regulations are satisfied.
Request for Relief 11R-49: Section XI, Examination Category B-D, item B3.90 requires 100%
volumetric examination of all RPV nozzle-to-vessel welds as defined by Figure IWB-2500-7(a).
Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code for RPV inlet nozzle-to-vessel Welds 1-RV-105-121A, B, C, and D.
As stated below the licensee has not proposed an attemative, but intends to maximize the examination through best effort:
"No additional volumetric examinations will be performed. The RPV welds have been examined to the maximum extent practical.
"An additional 70' angle beam examination was utilized for near surface (ID) coverage, up to a depth of 1" or 1/4t, whichever is greater."
The Code requires 100% volumetric examination of all Class 1 RPV nozzle-to-vessel welds.
However, the nozzle radius configuration restricts coverage and precludes 100% volumetric exarnination of the inlet nozzle welds. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the RPV nozzles would have to be redesigned and modified. Imposition of this requirement would result in a burden on the licensee.
The licensee has achieved a composite Code-required examination of 73.2% of the volume for each of the four subject nozzle-to-vessel welds. This composite percentage includes 81.9%
volumetric examination coverage for reflectors lying parallel to the weld seam. Due to the weld design, the most likely direction for inservice flaw initiation would be parallel to the weld seam. A 70' angle beam examination for near-surface inside diameter flaws has also been performed.
The combination of these examinations would have detected existing pattoms of degradation, and reasonable assurance of the RPV nozzle weld's structural integrity has been provided.
Thorofore, relief is granted pursuant to 10 CFR 50.55s(g)(6)(i).
Request for Relief 12R-21: Section XI, Examination Category B-D, item B3.90 requires 100%
volumetric examination of all RPV nozzle-to-vessel welds as defined by Figure IWB-2500-7(a).
. Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code for RPV outlet nozzle-to-vessel Welds 1-RV-107-121 A, B, C, and D.
l As stated below the licensee has not proposed an altemative, but intends to maximize the examination through best effort:
"None. Extended angle beam path ultrasonic techniques and higher angled beams (70 )
were utilized to obtain the maximum coverage possible."
The Code requires 100% volumetric examination of all Class 1 RPV nozzle-to-vessel welds.
l However, the nozzle radius configuration restricts coverage and precludes 100% volumetric examination of the outlet nozzle welds. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the RPV nozzles l
would have to be redesigned and modified. Imposition of this requirement would result in a l
burden on the licensee.
l The licensee has examined a composite Code-required volume of 71.5% for each of the four subject nozzle-to-vessel welds. This composite percentage includes 99.7% volumetric l
examination coverage for reflectors lying parallel to the weld seam. Due to the weld design, the l
most likely direction for inservice flaw initiation would be parallel to the weld seam. A 70* angle beam examination for near-surface inside diameter coverage has also been performed. The combination of these examinations will detect existing pattems of degradation and provide l
reasonable assurance of the RPV nozzle welds' structural integrity. Therefore, Request for Relief No.12R-21 is granted pursuant to 10 CFR 50.55a(g)(6)(i).
3.
CONCLUSION l
The staff evaluated the licensee's submittal and concluded that certain inservice examinations cannot be performed to the extent required by the Code at the Wolf Creek Generating Station. In Requests for Relief 11R-46 through 11R-49 (first inspection interval) and Request for Relief 12R-21 (second interval), the licensee has provided information to support the determination that the Code's volumetric examination coverage requirements are impractical. It is also concluded that reasonable assurance of component structural integrity has been provided by the examinations l
that have been performed. Therefore, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for Requests for Relief Nos.11R-46 through 11R-49 (first inspection interval) and Request for Relief 12R-21 (second interval), with the exception of Relief Request 11R-48, (with respect to Examination Category B-A, item B1.12, RPV shell welds). The relief granted will not endanger life, property, or the common defense and security and is otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were i
imposed on the facility. Relief for Examination Category B-A, item B1.12, RPV shell welds is deferred until the licensee has satisfied the regulations for augmented reactor vessel examination.
l j
Attachment:
Technical Letter Report
)
f Principal Contributor: T. McLellan 1
Date: April 15,1998
TECHNICAL LETTER REPORT ON THE FIRST 10-YEAR INTERVAL INSERVICE INSPECTION HERVESTS FOR RELIEF 11R-46 THROUGH 11R-49 AND SECOND 10-YEAR INTERVAL REQUEST FOR RELIEF 12R-21 EQB WOLF CREEK NUCLEAR OPERATING CORPORATION WOLF CREEK GENERATING STATION DOCKET NUMBER: 50482
1.0 INTRODUCTION
By letter dated May 23,1997, the licensee, Wolf Creek Nuclear Operating Corporation, submitted Relief Requests 11R-46 through 11R-49 and Relief Request 12R-21, seeking relief from the requirements of the ASME Code,Section XI, for the Wolf Creek Nuclear Station. Relief Requests 11R-46 through 11R-49 are for the first 10-year inservice inspection (ISI) interval, and 12R-21 is for second 10-year interval. The Idaho National Engineering and Environmental Laboratory (INEEL) staff has evaluated the subject requests for relief in the following section.
2.0 EVALUATION 1
The Code of record for Wolf Creek Nuc' ear Station's first 10-year ISI interval, which began September 1985, is the 1980 Edition through Winter 1981 Addenda of Section XI of the ASME Boiler and Pressure Vessel Code. The Code of record for the second 10-year ISI interval is the 1989 Edition. The information provided by the licensee in support of these requests for relief from Code requirements has been evaluated and the bases for disposition are documented below.
2.1 Reauest for Relief 11R-46. Examination Categorv B-J. Item B9.11. Accumulator Safetv Iniection Valve-to-Pioe Circumferential Weld (First Intervan Code Reauirement: Section XI, Examination Category B-J, item B9.11 requires 100%
surface and volumetric examination, as defined by Figure IWB-2500-8, for Class 1 circumferential welds 4-inch nominal pipe size (NPS) and larger.
ATTACHMENT f
i
l 2
I I
Licensee's Recuest for Relief: Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from the volumetric examination coverage requirements defined in ASME i
Section XI, Figure JWB-2500-8, Examination Volume C-D-E-F for the Class 1 Accumulator Safety injection Valve-to-pipe Weld EP-02-F021.
Licensee's Procosed Alternative Examination (as stated):
"None. Extended angle beam path ultrasonic techniques and higher angled beams (70*)
were utilized to obtain the maximum coverage possible."
Licensee's Basis for Recuestino Relief (as stated):
"As a result of geometry and metallurgical properties, the piping configuration does not provide an adequate examination surface to allow a complete examination from two directions (i.e., pipe to valve). 28.6% of the weld required volume received coverage from the axial scans in both beam directions and 28% of the weld required volume did not receive any coverage in either direction from the axial scans (Reference Figure 1').
Extended angle beam path ultrasonic techniques and higher angled beams (70') were utilized to obtain the maximum coverage possible. The subject weld did receive full coverage from the circumferential scans in both beam directions. A significant portion of the required volume was examined which provides for detection of significant pattems of degradation. In addition, the required surface examination was performed satisfactorily and the ASME Section XI visual examination VT-2 was performed as required.
" Based on this information, reasonable assurance of the continued inservice structural integrity of the subject weld is achieved without performing a complete Code examination.
Compliance with the applicable Code requirements can not be achieved."
Evaluation: The Code raquires 100% surface and volumetric examinations of Class 1 circumferential pressure-retaining pipe welds greater than or equal to 4-inch NPS.
However, geometry, weld configuration, and metallurgical properties restrict coverage and preclude 100% volumetric examination of accumulator safety injection valve-to inch pipe Weld EP-02-F021. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the wold l
joint would have to be redesigned and modified. Imposition of this requirement would result in a burden on the licensee.
The references are included in the original submittal by the licensee but not in this report.
i l
e 3
The licensee performed the Code-required two-direction axial scan on approximately 28.6% of the required weld volume. 72% of the required weld volume received an axial scan in at least one direction. In addition, the weld volume was examined with circumferential scans in both beam directions and the Code-required 100% surface examination was performed. The combination of the volumetric examination to the extent practical, complete surface examination, VT-2 visual examination as required by the Code, and examination of other Examination Category B-J welds assures that existing patterns of degradation would have been detected. As a result, reasonable assurance of the structural integrity of the subject weld has been provided. Therefore, it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i).
2.2 Reauest for Relief 11R-47. Examination Cateaorv C-F. Item C5.21. Accumulator Safety iniection Valve-to-Pioe Weld (First Interval)
Code Reauirement: Section XI, Examination Category C-F, item C5.21 requires volumetric and surface examination, as defined by Figure IWC-2500-7, for Class 2 circumferential pipe welds greater than %-inch nominal wall thickness.
Licensee's Reauest for Relief: Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code for accumulator safety injection valve to 10-inch pipe Weld EP-02-FW303.
Licensee's Prooosed Altemative (as stated):
"None. Extended angle beam path ultrasonic techniques and higher angled beams (70')
L were utilized to obtain the maximum coverage possible."
l Licensee's Basis for Reauestina Relief (as stated):
i "As a result of geometry and metallurgical properties, the piping configuration does not provide an adequate examination surface to allow a complete examination from two directions (i.e., pipe to valve). 34.4% of the weld required volume received coverage
l
)
4 from the axial scans in both beam directions (Reference Figure 1 ). The remaining 2
portion of the weld required volume received coverage from the axial scans in one beam direction. Extended angle beam path ultrasonic techniques and higher angled beams (70*) were utilized to obtain the maximum coverage possible. The subject weld did receive full coverage from the circumferential scans in both beam directions. A significant
{
portion of the required volume was examined which provides for detection of significant 1
patterns of degradation. In addition, the required surface examination was performed I
satisfactorily and the ASME Section XI visual examination VT-2 was performed as required.
l i
" Based on this information, reasonable assurance of the continued inservice structural integrity of the subject weld is achieved without performing a complete Code examination.
Compliance with the applicable Code requirements can not be achieved."
Evaluation: The Code requires 100% surface and volumetric examination of the subject pressure-retaining Class 2 circumferential pipe weld. However, geometry, weld j
)
configuration, and metallurgical properties restrict coverage and preclude 100%
j volumetric examination of accumulator safety injection valve-to-10-inch pipe Weld EP FW303. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the weld joint would have to be redesigned and modified. Imposition of this requirement would result in a burden on the l
licensee.
j The licensee performed the Code-required two-direction axial scan on approximately 34.4% of the required weld volume. The remaining portion of the weld volume received an axial scan in at least one direction. In addition, the weld received full volumetric examination from the circumferential scans in both beam directions and the Code-required 100% surface examination. The combination of the volumetric examination to the extent practical, complete surface examination, VT-2 visual examination as required by the Code, and examination of other Examination Category B-J welds assures that existing patterns of degradation would have been detected. As a result, reasonable assurance of the structuralintegrity of the subject weld has been provided. Therefore, it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i).
The references are included in the original submittal by the licensee but, not 2
included in this report.
P.
5 2.3 Reauest for Relief 11R-48. Examination Categorv B-A. Items B1.12. 81.21. and B1.22.
Class 1 Reactor Pressure Vessel Longitudinal Shell and Bottom Head Circumferential l
and Meridional Welds (First Interval) l NOTE: This request was submitted, pursuant to 10 CFR 50.55a(g)(5)(iii), in regard to the ASME Section XI requirements for Examination Category B-A, item B1.12, RPV longitudinal shell welds. However, while a request under 10 CFR 50.55a(g)(5)(iii)is acceptable for ASME requirements deemed impractical, it is not allowed under 10 CFR 50.55a(g)(6)(ii)(A), Augmented examination of reactor vessel. Furthermore, since all existing requests for relief were revoked by the augmented rule, it is not appropriate to address the current request prior to the augmented rule being satisfied.
Therefore, evaluation of the item B1.12 welds (Weld Nos.1 PV-101-122A, B, C, and D) in this relief request will be deferred until the licensee has satisfied the regulations for the augmented reactor vessel examination.
Code Reauirement: Section XI, Examination Category B-A, items B1.21 and B1.22 require 100% volumetric examination of the accessible length of all circumferential and meridional head welds, as defined by Figure IWB-2500-3.
Licensee's Reauest for Relief: Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code on the following RPV welds. Included in the table below is an estimate of the composite Code-required volume (CRV) examined.
l COM E
ITEM NUMBER WELD IDENTIFICATION ED B1.12 1-RV-101-122A 66.7 %
B1.12 1-RV-101-122B 69.9 %
B1.12 1-RV-101-122C 74.4 %
B1.21 1-RV-101-141
- 65.3 %
B1.21 1-RV-102-151' 48.2 %
i
]
6 l
B1.22
.1-RV-101-154A 74.8 %
B1.22 1-RV-101-154B 74.8 %
L B1.22 1-RV-101-154C 74.8 %
l l.
. B1.22 1-RV-101-154D 74.8 %
- In the SER dated November 9.1987, relief was granted for Welds 1-RV-101 141 and 1-RV-102-151 based on the licensee's assumption that approximately 90% of the CRV could be examined. As indicated by this re!ief request. actual examination volumes achieved are less than originally anticipated.
Licensee's Prooosed ? !temative (as stated):
l "No additional volumetric examinations will be performed. The RPV welds have been examined to the maximum extent practical."
"An additional 70* angle beam examination was performed for near surface (ID) coverage."
Licensee's Basis for Reauestina Relief (as stated 8):
" Reactor Vessel design and configuration prevents 100% ultrasonic (UT) examination of the code required volume (CRV) for the subject welds. The specific limitations for each weld examination are discussed below and detailed on the applicable attachments and figures. Calculation of the CRV Achieved Percentages is based on a conservative approach which employs the UT central ray data only; beam spread was agi taken into account.
"1.
B1.12 Longitudinal Welds 1-RV-101-122A, B & C Limitations
" Physical limitations for all three welds are due to nozzle geometry and location in -
the upper shell course relative to the longitudinal weld location as well as flange to shell weld ID taper as shown on Figure 1. Composite coverage of the UT scans j
was calculated to be 66.7%,69.9%, and 74.4% for Weld A, B, and C, respectively.
Attachments 1,2, & 3 provide a summary.of the inspection coverage.
"2.
B1.21 Circumferential Weld 1-RV-101-141 Limitations "Physicallimitations of the UT scans of this circumferential weld were due to the six (6) core support lugs as depicted on Figure 2 attached. Composite coverage of the UT scans was calculated to be 65.3% Attachment 4 provides a summary of the
-l inspection coverage.
I "3.
' B1.21 Circumferential Weld 1-RV-102-151 Limitations i
Attachments and figures that were in the original submittal are not included in
-8 this report.
i
7 "Physicallimitations of the UT scans of this bottom head circumferential weld were due to bottom mounted instrumentation (BMI) tubes. Fifty-eight total; of which, approximately 29 interfere with scan coverage as shown on Figures 3 & 4 attached.
Composite coverage of the UT scans was calculated to be 48.2% Attachment 5 provides a summary of the inspection coverage.
"4.
B1.22 Meridional Welds 1-RV-101-154A, B, C & D "Physicallimitations of the UT scans of the four bottom head meridional welds were due to the location of BMI tubes and the core support lugs as shown on Figures 1, 3 & 4. Composite coverage of the UT scans was calculated to be 74.8% provides a summary of the inspection coverage.
"The Reactor Vessel was designed and fabricated in accordance with the stringent quality controls of ASME Section Ill; subsequent volumetric and surface examinations as well as pressure testing was performed on these welds with acceptable results. A significant portion of the required volume was examined which provides for detection of significant I
patterns of degradation, i
" Based on this information, reasonable assurance of the continued inservice structural integrity of the subject welds is achieved without performing a complete Code examination. Compliance with the applicable Code requirements can only be accomplished by redesigning and refabricating the Reactor Vessel. WCNOC deems this course of action impractical."
Evaluation: The Code requires 100% volumetric examination of the accessible length of all RPV head welds during the first inspection interval. However, physical limitations inside the RPV restrict coverage and preclude 100% volumetric examination of the RPV bottom head circumferential and meridional welds listed above. For circumferential head Weld 1-RV-101-141 (Item B1.21), six core support lugs obstruct examination. For circumferential head Weld 1-RV-102-151 (Item B1.21),29 of the 58 bottom mounted l
instrumentation (BMI) tubes interfere with scan coverage. For meridional head Welds 1-i i
RV-101-154A, B, C, and D (Item B1.22), limitations include the core support lugs and BMI tubes. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To satisfy the Code requirements, design modifications to the RPV are necessary to allow access for complete examination, imposition of this requirement would result in a burden on the licensee.
I The licensee examined a significant portion of these RPV welds. A composite Code-required examination of 48.2% of the weld volume for circumferential head Weld 1-RV-i
o 8
102-151,65.3% for circumferential head Weld 1-RV-101-141, and 74.8% for each of the four meridional head Welds 1-RV-101-154A, B, C, and D has been completed. The licensee also performed an additional 70' angle beam examination for near-surface inside diameter coverage. These examinations would have detected existing patterns of degradation and have provided reasonable assurance of the RPV's structuralintegrity.
Based on the impracticality of meeting the Code requirements, and the reasonable assurance of structural integrity provided by the examinations tnat are being performed, it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i) for the first 10-year interval examinations on item B1.21 and B1.22 welds. For item B1.12 circumferential shell welds, it is recommended that the evaluation of any relief request be deferred until the augmented RPV examination requirements in the regulations are satisfied.
2.4 Reauest for Relief 11R-49. Examination Cateoorv B-D. Item B3.90. Class 1 RPV inlet Nozzle Welds (First Interval)
Code Reauirement: Section XI, Examination Category B-D, item B3.90 requires 100%
volumetric examination of all RPV nozzle-to-vessel welds as defined by Figure IWB-2500-7(a).
Licensee's Reauest for Relief: Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code for RPV inlet nozzle-to-vessel Welds 1-RV-105-121 A, B, C, and D.
Licensee's Prooosed Attemative (as stated):
"No additional volumetric examinations will be performed. The RPV welds have been examined to the maximum extent practical.
"An additional 70' angle beam examination was utilized for near surface (ID) coverage, up to a depth of 1" or 1/4t, whichever is greater."
4 3
9 Licensee's Basis for Reauestino Relief (as statedd):
. Reactor Vessel design and configuration prevents 100% ultrasonic (UT) examination of the code required volume (CRV) for the subject welds. The specific limitations for each weld examination are discussed below and detailed on the applicable attachments and figures. Calculation of the CRV achieved percentages is based on a conservative -
approach which employs the UT central ray data only; beam spread was D91 taken into account.
" Physical limitations of the UT scans of the inlet Nozzle to Vessel Welds were due to the nozzle radius configurations which prevented full coverage as shown on Figures 1 and 2.
' Composite coverage of the UT scans was calculated to be 73.2% for each weld.
. provides a summary of the inspection coverage.
"The Reactor Vessel was designed and fabricated in accordance with the strident quality controls of ASME Section lil; subsequent volumetric and surface examinations as well as
}
pressure testing was performed on these welos with acceptable results. A significant portion of the required volume was examined which provides for detection of significant
}
pattems of degradation.
" Based on this information, reasonable assurance of the continued inservice structural integrity of the subject weld is achieved without performing a complete Code examination.
Compliance with the applicable Code requirements can only be accomplished by redesigning and refabricating the Reactor Vessel. WCNOC deems this course of action -
impractical."
Evaluation The Code requires 100% volumetric examination of all Class 1 RPV nozzle-to-vessel welds. However, the nozzle radius configuration restricts coverage and precludes 100% volumetric examination of the inlet nozzle welds. The volumetric examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the RPV nozzles would have to be redesigned and modified. Imposition of this requirement would result in a burden on the licensee.
The licensee has achieved a composite Code-required examination of 73.2% of the volume for each of the four subject nozzle-to-vessel welds. This composite perr.,0tage includes 81.9% volumetric examination coverage for reflectors lying parallel to the weld Attachments and figures that were in the original submittal are not included in this report.
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O O
10 seam. Due to the weld design, the most likely direction for inservice flaw initiation would be parallel to the weld seam. A 70* angle beam examination for near surface inside diameter flaws has also been performed. The combination of these examinations would have detected existing patterns of degradation, and reasonable assurance of the RPV nozzle weld's structural integrity has been provided. Therefore, it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i).
2.5 Reauest for Relief 12R-21. Examination Categorv B-D. Item B3.90 RPV Outlet Nozzle-to-Vessel Welds (Second Interval)
Code Reauirement: Section XI, Examination Category B-D, item B3.90 requires 100%
1 volumetric examination of all RPV nozzle-to-vessel welds as defined by Figure IWB-2500-7(a).
Licensee's Reauest for Relief: Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing the volumetric examination to the extent required by the Code for RPV outlet nozzle-to-vessel Welds 1-RV-107-121 A, B, C, and D.
Licensee's Pronosed Altemative (as stated):
"None. Extended angle beam path ultrasonic techniques and higher angled beams (70')
were utilized to obtain the maximum coverage possible."
i Licensee's Basis for Reauestina Relief (as stated 5):
" Reactor Vessel design and configuration prevents 100% ultrasonic (UT) examination of the code required volume (CRV) for the subject welds. The specific limitations for each weld examination are discussed below and detailed on the applicable attachments and figures. Calculation of the CRV achieved percentages is based on a conservative approach which employs the UT central ray data only; beam spread was nQ1taken into account.
"Physicallimitations of the UT scans of the Outlet Nozzle to Vessel Welds were due to the outlet nozzle protrusion on configurations which prevented full coverage as shown on l
Figures 1 and 2. Composite coverage of the UT scans was calculated to be 71.5% for each weld. Attachment 1 provides a summary of the inspection coverage.
Attachments and figures that were in the original submittal are not included in 5
this report.
I 1.
e la; 11 l
"The Reactor Vessel was designed and fabricated in accordance with the stringent quality controls of ASME Section lil; subsequent volumetric and surface examinations as well as pressure testing was performed on these welds with acceptable results. A significant portion of the required volume was examined which provides for detection of significant pattems of degradation.
" Based on this information, reasonable assurance of the continued inservice structural integrity of the subject weld is achieved without performing a complete Code examination.
Compliance with the applicable Code requirements can only be accomplished by redesigning and refabricating the Reactor Vessel. WCNOC deems this course of action impractical."
i Evaluation: The Code requires 100% volumetric examination of all Class 1 RPV nozzle-to-vessel welds. However, the nonle radius configuration restricts coverage and precludes 100% volumetric examination of the outlet nonle welds. The volumetric I
examination is, therefore, impractical to perform to the extent required by the Code. To meet the Code requirements, the RPV nozzles would have to be redesigned and modified. Imposition of this requirement would result in a burden on the licensee.
The licensee has examined a composite Code-required volume of 71.5% for each of the four subject nozzle-to-vessel welds. This composite percentage includes 99.7%
volumetric examination coverage for reflectors lying parallel to the weld seam. Due to the weld design, the most likely direction for inservice flaw initiation would be parallel to the weld seam. A 70* angle beam examination for near-surfaco inside diameter coverage has also been performed. The combination of these examinations will detect existing patterns of degradation and provide reasonable assurance of the RPV nozzle welds' structuralintegrity. Therefore,it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i).
3.0 CONCLUSION
The INEEL staff evaluated the licensee's submittal and concluded that certain inservice examinations cannot be performed to the extent required by the Code at the Wolf Creek Nuclear Station. In Requests for Relief 11R-46 through 11R-49 (first inspection interval) and Request for Relief 12R-21 (second interval), the licensee has provided information to l
e F
r a
12 support the determination that the Code's volumetric examination coverage requirements 4
are impractical. It is also concluded that reasonable assurance of component structural integrity has been provided by the examinations that have been performed. Therefore,it is recommended that relief be granted pursuant to 10 CFR 50.55a(g)(6)(i). However, _
evaluation of Relief Request 11R-48. Examination Category B-A, item B1.12, RPV shell welds has been deferred until the licensee has satisfied the regulations for augmented reactor vessel examination.
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