ML20141C903
| ML20141C903 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 05/13/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20141C892 | List: |
| References | |
| NUDOCS 9705190265 | |
| Download: ML20141C903 (7) | |
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.octog 21 UNITED STATES a.
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NUCLEAR REGULATORY COMMISSl')N l
'2 WASHINGTON, D.C. 30666 0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACT)R REGULATION OF THE SECOND TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN RE0 VESTS FOR RELIEF 151-10 AND ISI-11 UNION ELECTRIC COMPANY CALLAWAY PLANT. UNIT NO. 1 DOCKET NO. 50-483
1.0 INTRODUCTION
The Technical Specifications (TS) for Callaway Plant 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) of Title 10 of the Code of Federal Regulations states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2 and 3 components (including supports) shall meet the requirements, except the design and access provisions and the 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 S0.55a(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 Callaway Plant, second ten-year inservice inspection (ISI) interval is 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 alternative requirements that are determined to be i
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. 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.
By letter dated December 6,1996, Union Electric Company (the licensee),
submitted to the NRC its Second Ten-Year Inservice Inspection Interval Program Plan Requests for Relief 151-10 AND 151-11 for Callaway plant.
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 support of its Second Ten-Year Inservice Inspection Interval Program Plan Requests for Relief ISI-10 and 151-11 for Callaway Plant.
Based on the information submitted, the staff adopts the contractor's conclusfons and recommendations presented in the attached Technical Letter Report (TLR).
In Request for Relief ISI-10 the licensee has requested relief from Code volumetric examination requirements for pressurizer nozzle-to-safe end butt welds 2-TBB03-3-A-W and 2-TBB03-3-B-W.
Based on a review of the information provided, it has been determined that the configuration of the nozzle-to-safe end welds limits volumetric examination to the extent required by Code. The staff determined that compliance with Code requirements is impractical.
To provide access for performing the Code-required examinations, a design change and modification would be required.
Imposition of this requirement would cause a burden on the licensee.
The licensee is examining the subject nozzle-to-safe end welds to the extent practical, obtaining cumulative coverages of 88 percent and 85 percent respectively.
The licensee obtained 100 percent coverage with circumferent'ial scans of the weld and adjacent base metal.
In addition, the licensee performed scans for the detection of flaws parallel to the weld to the extent practical and obtained 100 percent coverage from one direction and 54 percent and 40 percent coverage respectively, in two directions.
Based on the examination technique being employed and the percent of volumetric examination coverage obtained by the circumferential and axial scans in combination with the 100 percent surface examinations, the staff determined that, degradation, if present, would have been detected.
Furthermore, the staff determined that the licensee's examinations of the subject welds to extent practical provides reasonable assurance of structural integrity. Therefore, the staff has determined that relief is granted for Request for Relief ISI-10 as requested pursuant to 10CFR50.55a(g)(6)(1).
In Request for Relief ISI-11 the licensee has requested relief from Code volumetric and surface examination requirements for the valve-to-pipe weld 2-EP-01-F007 in the Accumulator Safety Injection System.
Based on the information provided, the staff has determined that Code requirements are impractical because of the configuration of the valve-to-pipe weld and because
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l l a permanent obstruction (welded energy absorption chamber that obstructs nine inches of the circumferential weld) limits the volumetric and surface j
examinations. To provide access for-performing the Code-required examination, a design change and modification would be required.
Imposition of the Code requirement would be a burden on the licensee.
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The licensee utilized a 1/2V technique for-the ultrasonic examination, scanning from both sides of the weld where' unrestricted. The licensee obtained 75 percent volumetric and 73 percent surface examination coverage of the subject weld and of the area examined, and no flaws were detected.
Based on the percent of combined coverages obtained for the subject weld, and the area examined being free of flaws, the staff determined that degradation, if occurring, would have been detected.
Furthemore, the staff determined that the licensee's examinations of the subject welds to extent practical provides reasonable assurance of structural integrity.
Therefore, the staff has determined that relief is granted for Request ior Relief ISI-11 as requested pursuant to 10CFR50.55a(g)(6)(i).
3.0 CONCLUSION
The staff concluded that performing Code required examinations for Requests for Relief ISI-10 and 151-11 are impractical for the Callaway Plant and that the licensee performed the Code-required examinations on each of the subject 1
welds to the extent practical.
Furthermore, the staff concluded that the licensee's examinations of the subject welds to the extent practical provides i
reasonable assurance of structural integrity. Therefore, the staff concludes that pursuant to 10 CFR 50.55a(g)(6)(1), requests for relief ISI-10 and ISI-11 are authorized by law and will not endanger life or 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 imposed on the facility.
Attachment:
Technical Letter Report Principal Contributor:
T. McLellan Date: May 13, 1997 l
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ATTACHMENT l
TECHNICAL LETTER REPORT ON THE SECOND 10-YEAR l
INSERVICE INSPECTION INTERVAL i
RE0UESTS FOR RELIEF ISI-10 AND 151-11 l
UNION ELECTRIC CALLAWAY PLANT DOCKET NUMBER 50-483
1.0 INTRODUCTION
By letter dated December 6,1996, the licensee submitted Relief Requests 151-10 and 151-11 to the Callaway' Plant, second interval inservice inspection
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program.
The Idaho National Engineering and Environmental Laboratory (iNEEL) staff has evaluated the subject request for relief in the following section.
2.0 EVALUATION The licensee submitted the subject requests for the second 10-year interval which began on August 1, 1995.
The Code of record for the second interval is the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 1989 Edition.
The information provided by the licensee in support of the request has been evaluated and the bases for disposition are documented below.
2.1 Relief Reauest 151-10.Section XI. Table IWB-2500-1. Examination Cateaory B-F. Item B5.40. Examination of Pressurizer Nozzle-to-Safe End Butt Welds Code Reauirement:
Section XI, Table IWB-2500-1, Examination Category B-F, Item 85.40, requires 100% volumetric and surface examination of pressurizer nozzle-to-safe end butt welds as by defined Figure IWB-2500-8.
Licensee's Code Relief Reauest:
Pursuant to 10 CFR 50.55a(g)(5)(iii),
1 the licensee requested relief from performing the volumetric examination to the extent required.by the Code for Welds 2-TBB03-3-A-W and 2-TBB03-3-B-W.
i Licensee's Basis for Reauestina Relief (as stated):
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" Weld 2-TBB03-3-A-W achieved a composite coverage of 88% of the weld volume when including the axial exam from the safe end side and the circumferential exam. Weld 2-TBB03-3-B-W achieved a composite coverage of 85% of the weld volume based on the axial exam from the safe end side i
i and the circumferential exam.
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'. "The limitation to the axial scan performed on the nozzle side is due to OD geometry to the nozzle limiting the scan path of the weld coupled with the beam redirection from the Inconel buttering on the safe end side.
Actual coverage achieved in each direction is listed below.
2-TBB03-3-A-W Axial Scan Coverage in one direction 100%
Axial Scan Coverage in both directions 54%
Circumferential Coverage in Both directions 100%
2-TBB03-3-B-W Axial Scan Coverage in one direction 100%
Axial Scan Coverage in both directions 40%
Circumferential Coverage in both directions 100%
"The code required surface exams were also performed on these welds at this time and yielded no indications with 100% coverage. A 60*
longitudinal wave scan was performed on the nozzle side of the welds to compensate for the beam redirection. The estimated coverage achieved is conservatively based on this nominal 60* angle. With beam redirection, the actual examination angle.is estimated to be closer to 45' and thus yields a greater weld volume examined than was recorded.
"These components were granted relief based on 80% coverage in the first ten year interval under submittal SLNRC 84-0061 Attachment E dated April 9, 1984. The increased coverage coupled with no recordable indications adds assurance to the weld integrity.
"It is impractical to achieve any additional weld coverage, therefore relief is requested pursuant to 10CFR50.55a(g)(5)(iii)."
Licensee's Proposed Alternative Examination (as stated):
"None. The best possible examination was performed using a combination of contoured dual refracted longitudinal and shear wave transducers. The extent of this ultrasonic examination, the liquid penetrant surface examination, the Section XI VT-2 (visual) examination for leakage performed once every refueling outage, and the reactor coolant leakage detection system verify weld integrity."
Evaluation: The licensee has requested relief from Code volumetric examination requirements for the subject pressurizer nozzle-to-safe end l
butt welds.
Based on a review of the information provided, it has been i
determined that the configuration of the nozzle-to-safe end welds, limits i
volumetric examination to the extent required by Code. As a result, it is concluded that compliance with Code requirements is impractical. To provide access for performing the Code-required examinations, a design change and modification would be required.
Imposition of this requirement would cause a burden on the licensee.
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.* The licensee is examining the subject nozzle-to-safe end welds to the extent practical, obtaining cumulative coverages of 88% and 85%
respectively.
The licensee obtained 100% coverage with circumferential scans of the weld and adjacent base metal.
These scans provide detection capability of flaws lying transverse to the weld.
In addition, the licensee performed scans for the detection of flaws parallel to the weld to the extent practical. Scans for detection of flaws parallel to the welds obtained 100% coverage from one direction and 54% and 40% coverage respectively, in two directions.
Because of the potential of beam redirection caused by the safe-end material, the licensee optimized the coverage and flaw detection capabilities by utilizing a 60' refracted longitudinal ultrasonic wave from the nozzle side.
Considering the examination technique being employed and the percent of volumetric examination coverage obtained by the circumferential and axial scans in combination with the 100% surface examinations, it is reasonable to conclude that, degradation, if present, would have been detected. As a result, reasonable assurance of structural integrity is provided.
Therefore, pursuant to 10 CFR 50.55a(g)(6)(i), it is recommended that relief be granted.
2.2 Relief Reauest ISI-11.Section XI. Table IWB-2500-1. Examination Cateaory B-J. Item B9.11. Examination of the Safety In.iection System Valve-to-Pioe Efld Code Reauirement:
Section XI, Table IWB-2500-1, Examination Category B-J, Item B9.11, requires 100% volumetric and surface examination of piping butt welds as defined by Figure IWB-2500-8.
Licensee's Code Relief Reauest:
Pursuant to 10 CFR 50.55a(g)(5)(iii),
the licensee requested relief from performing the volumetric examination to the extent required by Code for Weld 2-EP-01-F007.
Licensee's Basis for Reauestina Relief (as stated):
"A composite coverage of 75% of the weld volume was achieved for weld 2-EP-01-F007 for both the axial and circumferential exams.
The surface exam was able to cover 73% of the required surface area.
"The limitation is due to a permanently welded energy absorption chamber that completely obstructs 9" of the circumference of the weld.
It is impractical to remove a permanent obstruction. A 1/2V volumetric exam was performed from both sides utilizing both a 45' and 60* transducer where accessible. No indications were found.
The surface exam.was performed to the extent possible with the obstruction in place.
"This weld was approved for relief in the first ten year interval under Callaway ISI Relief Request M submitted June 28, 1991. At that time 65%
of the weld was calculated to be examined.
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" Based on the increased coverage percentage and the fact that no indications were detected, the weld integrity has been assured.
It is
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impractical to achieve any additional weld coverage at this time, therefore relief is requested pursuant to 10CFR50.55a(g)(5)(iii)."
t Licensee's Proposed Alternative Examination (as stated):
'None. The maximum possible volume and surface were examined as i
practical.
The extent of this ultrasonic examination and liquid i
- penetrant surface examination, the Section XI VT-2 (visual) examination for leakage perfor' ed once every refueling outage, and the reactor m
coolant leakage detection system verify weld integrity."
i Evaluation: The licensee has requested relief from Code volumetric and surface examination requirements for the subject valve-to-pipe weld in 4
the Accumulator Safety Injection System.
Based on a review of the
% formation' provided, it has been determined that the configuration of valve-to-pipe weld and a permanent obstruction (welded energy
..,orption chamber that obstructs 9" of the circumferential weld), limit the volumetric and surface examinations. As a result, it is concluded that compliance with Code requirements is impractical.
To provide access
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for performing the Code-required examination, a design change and modification would be required. -Imposition of this requirement would cause a burden on the licensee.
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The limiting factor for the subject examination is an energy absorption chamber. The chamber is a permanently welded obstruction that completely 4
-restricts 9 inches of the circumferential weld from both volumetric and surface examination. The licensee utilized a 1/2V technique for the-ultrasonic examination, scanning from both sides of the weld where unrestricted. Of the area examined, no flaws were detected.
The licensee is examining the accessible portion of the subject valve-to-pipe weld obtaining 75% volumetric and 73% surface examination coverage.
Based on the percent of combined coverages obtained for the subject weld, and the area examined being free of flaws, it is reasonable to conclude that, degradation, if occurring, would have been detected. As a result, reasonable assurance of structural integrity is provided. Therefore, pursuant to 10 CFR 50.55a(g)(6)(1), it is recommended that relief be granted.
3.0 CONCLUSION
Performing the subject examinations to the extent required by Codo is impractical for the Callaway Plans. Union Electric performed the Code-required examinations on each of the subject welds to the extent practical, providing reasonable assurance of structural integrity.
Therefore, it is recommended that pursuant to 10 CFR 50.55a(g)(6)(1),
relief be granted for Requests for Relief ISI-10 and 1S1-11.
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