BYRON 2006-0116, Inservice Inspection Program Relief Request 13R-09 and 13R-10
| ML063480268 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 10/26/2006 |
| From: | Hoots D Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BYRON 2006-0116 | |
| Download: ML063480268 (25) | |
Text
10 CFR 50.55a October 26, 2006 LTR:
BYRON 20060116 File:
1.10.0101 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. 50-454 and 50-455
Subject:
Inservice Inspection Program Relief Request l3R-09 and 13R-10 In accordance with 10 CFR 50.55a, Codes and standards, paragraph (a)(3)(i), Exelon Generation Company, LLC (EGC), is requesting relief from certain requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, on the basis that alternative methods will provide an acceptable level of quality and safety.
Specifically, Attachment A contains the basis for a proposed alternative to the requirements for class 1 pressure retaining welds examinations and Attachment B contains the basis for a proposed alternative to the requirements for dissimilar metal piping welds examinations.
EGC requests approval of this request by the Unit 2 Spring 2007 refuel outage currently scheduled for April 2007. If there are any questions or comments, please contact William Grundmann at (815)406-2800.
Respectfully,
/
/,
I
~ ~,
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I David M.Hoots Plant Manager Byron Nuclear Generating Station DMH/JEL/rah Attachments A.
Byron Station Relief Request 1 3R-09 B.
Byron Station Relief Request 13R-10
Attachment A Byron Station Relief Request 13R-09
IS! Program P/an Unit 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-09 Revision 0 (Page 1 of 3)
Request for Relief in Accordance with 10 CFR 50,55a(a)(3)(i)
Alternative Requirements to ASME Section XI Class 1 Pressure Retaining Welds When Examined from the Inside Surface Use of Alternative Through-Wall Sizing Requirements for Implementation of Appendix VIII, Supplement 10 1.
ASME CODE COMPONENT(S) AFFECTED:
Code Class:
1 Examination Categories:
Category R-A (Risk Informed lSl)
Item Numbers:
R1.15 (Risk Informed ISI)
Component Numbers:
See Table 1 Drawing Numbers:
See Table 1 2.
APPLICABLE CODE EDITION AND ADDENDA:
The current inservice inspection program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, 2001 Edition through the 2003 Addenda. Ultrasonic examination of applicable Class 1 and 2 components is governed by Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, of the ASME Code,Section XI, 1995 Edition with the 1996 Addenda.
3.
APPLICABLE CODE REQUIREMENTS:
The examination of Class 1 and 2 piping welds are required to be performed using procedures, personnel, and equipment qualified to the criteria of the ASME Code,Section XI, 1995 Edition 1996 Addenda, Appendix VIII, Supplement 10, Qualification Requirements for Dissimilar Metal Pipe Welds.
In addition, Paragraph 3.2 Sizing Acceptance Criteria, subparagraph (b) states that the examination procedures, equipment, and personnel are qualified for depth sizing when the root mean square error (RMSE) of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125-inch (3.2mm).
4.
REASON FOR THE REQUEST:
Exelon Generation Company, LLC. (EGC) has been informed that WesDyne International, the inspection vendor performing examinations at Byron Station, has been unsuccessful at achieving the 0.125-inch RMSE depth-sizing criterion for the procedure and personnel qualifications for dissimilar metal examinations performed from the inside surface of the pipe and instead has achieved an accuracy of 0.189-inch RMSE. To date, there has not been a vendor who has met the RMSE Code requirement for dissimilar metal weld examinations performed from the inside surface.
IS! Program P/an____ _____________________
Unit 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-09 Revision 0 (Page2of3)
This relief is being requested as a contingency in the event detectable indications, requiring depth sizing, are identified during upcoming inservice inspections in the Byron Station, Unit 2 April 2007 refueling outage.
5.
PROPOSED ALTERNATIVE AND BASIS FOR USE:
Pursuant to 10 CFR 50.55a(a)(3)(i), relief is requested for an alternative requirement that will provide an acceptable level of quality and safety. EGO requests relief to consider examination procedures, equipment, and personnel qualified for depth sizing when the RMSE of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.189-inch for the ultrasonic examination of dissimilar metal welds performed from the inside surface of the pipe at Byron Station, Unit 2. The RMSE of 0.189-inch is based on actual vendor demonstrated, in-process, field qualifications and is the optimum value that could be achieved.
The proposed procedure to address sizing of the flaws that may be detected during the examination is to add the difference between the 0.189-inch achieved sizing error and the 0.125-inch RMSE Appendix VIII, Supplement 10 acceptance criteria to the measured flaw size. EGC considers the use of this difference (0.064-inch), as an adjustment to the measured flaw will ensure a conservative bounding flaw depth value for dissimilar metal welds at Byron Station, Unit 2.
6.
DURATION OF PROPOSED ALTERNATIVE:
This relief request will be implemented during the remainder of the Byron Station, Unit 2 Third ten-year inservice inspection interval, which ends July 15, 2016.
7.
PRECEDENTS:
In a Gene Y. Suh to Christopher M. Crane, (Exelon Generation Company, LLC) letter dated February 25, 2005; the NRC authorized the same relief for Byron Unit 1, Docket No. 50-454 Relief Request 12R-50 (ML050450576).
8.
ATTACHMENTS None
IS!_Program P/an Unit 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-09 Revision 0 (Page3of3)
TABLE 1: APPLICABLE COMPONENTS WELD NUMBER DESCRIPTION WIN NUMBER FORMER ASME XI ITEM NUMBER CURRENT RJ-ISI ITEM NUMBER Unit 2 2RC-01-R/RPVS-A/F1 RPV Nozzle Safe-End Hot Leg Loop D 2RPV-1 B5.10 R1.15 2RC-01-R!RPVS-B/F1 RPV Nozzle Safe-End Cold Leg Loop D 2RPV-1 B5.10 R1.15 2RC-O1-R/RPVS-C/F1 RPV Nozzle Safe-End Cold Leg Loop C 2RPV-1 B5.1O Ri.15 2RC-Oi-R/RPVS-D/F1 RPV Nozzle Safe-End Hot Leg Loop C 2RFV-i B5.1O R1.15 2RC-Oi-R/RPVS-E/F1 RPV Nozzle Safe-End Hot Leg Loop B 2RPV-i B5.1O R1.15 2RC-0i-R/RPVS-F/Fi RPV Nozzle Safe-End Cold Leg Loop B 2RPV-1 B5.10 Ri.15 2RC-Oi-R/RPVS-G/F1 RPV Nozzle Safe-End Cold Leg Loop A 2RPV-i B5.10 Ri.15 2RC-Oi-R/RPVS-H/F1 RPV Nozzle Safe-End Hot Leg Loop A 2RPV-1 B5.10 Ri.15
Attachment B Byron Station Relief Request 13R-1O
10 CFR 50.55a October 26, 2006 LTR:
BYRON 20060116 File:
1.10.0101 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. 50-454 and 50-455
Subject:
Inservice Inspection Program Relief Request l3R-09 and 13R-10 In accordance with 10 CFR 50.55a, Codes and standards, paragraph (a)(3)(i), Exelon Generation Company, LLC (EGC), is requesting relief from certain requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section Xl, Rules for Inservice Inspection of Nuclear Power Plant Components, on the basis that alternative methods will provide an acceptable level of quality and safety.
Specifically, Attachment A contains the basis for a proposed alternative to the requirements for class 1 pressure retaining welds examinations and Attachment B contains the basis for a proposed alternative to the requirements for dissimilar metal piping welds examinations.
EGC requests approval of this request by the Unit 2 Spring 2007 refuel outage currently scheduled for April 2007. If there are any questions or comments, please contact William Grundmann at (815)406-2800.
Respectfully,
/
/,
I
~ ~,
/~*-~
I David M.Hoots Plant Manager Byron Nuclear Generating Station DMH/JEL/rah Attachments A.
Byron Station Relief Request 1 3R-09 B.
Byron Station Relief Request 13R-10
Attachment A Byron Station Relief Request 13R-09
IS! Program P/an Unit 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-09 Revision 0 (Page 1 of 3)
Request for Relief in Accordance with 10 CFR 50,55a(a)(3)(i)
Alternative Requirements to ASME Section XI Class 1 Pressure Retaining Welds When Examined from the Inside Surface Use of Alternative Through-Wall Sizing Requirements for Implementation of Appendix VIII, Supplement 10 1.
ASME CODE COMPONENT(S) AFFECTED:
Code Class:
1 Examination Categories:
Category R-A (Risk Informed lSl)
Item Numbers:
R1.15 (Risk Informed ISI)
Component Numbers:
See Table 1 Drawing Numbers:
See Table 1 2.
APPLICABLE CODE EDITION AND ADDENDA:
The current inservice inspection program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, 2001 Edition through the 2003 Addenda. Ultrasonic examination of applicable Class 1 and 2 components is governed by Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, of the ASME Code,Section XI, 1995 Edition with the 1996 Addenda.
3.
APPLICABLE CODE REQUIREMENTS:
The examination of Class 1 and 2 piping welds are required to be performed using procedures, personnel, and equipment qualified to the criteria of the ASME Code,Section XI, 1995 Edition 1996 Addenda, Appendix VIII, Supplement 10, Qualification Requirements for Dissimilar Metal Pipe Welds.
In addition, Paragraph 3.2 Sizing Acceptance Criteria, subparagraph (b) states that the examination procedures, equipment, and personnel are qualified for depth sizing when the root mean square error (RMSE) of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125-inch (3.2mm).
4.
REASON FOR THE REQUEST:
Exelon Generation Company, LLC. (EGC) has been informed that WesDyne International, the inspection vendor performing examinations at Byron Station, has been unsuccessful at achieving the 0.125-inch RMSE depth-sizing criterion for the procedure and personnel qualifications for dissimilar metal examinations performed from the inside surface of the pipe and instead has achieved an accuracy of 0.189-inch RMSE. To date, there has not been a vendor who has met the RMSE Code requirement for dissimilar metal weld examinations performed from the inside surface.
IS! Program P/an____ _____________________
Unit 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-09 Revision 0 (Page2of3)
This relief is being requested as a contingency in the event detectable indications, requiring depth sizing, are identified during upcoming inservice inspections in the Byron Station, Unit 2 April 2007 refueling outage.
5.
PROPOSED ALTERNATIVE AND BASIS FOR USE:
Pursuant to 10 CFR 50.55a(a)(3)(i), relief is requested for an alternative requirement that will provide an acceptable level of quality and safety. EGO requests relief to consider examination procedures, equipment, and personnel qualified for depth sizing when the RMSE of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.189-inch for the ultrasonic examination of dissimilar metal welds performed from the inside surface of the pipe at Byron Station, Unit 2. The RMSE of 0.189-inch is based on actual vendor demonstrated, in-process, field qualifications and is the optimum value that could be achieved.
The proposed procedure to address sizing of the flaws that may be detected during the examination is to add the difference between the 0.189-inch achieved sizing error and the 0.125-inch RMSE Appendix VIII, Supplement 10 acceptance criteria to the measured flaw size. EGC considers the use of this difference (0.064-inch), as an adjustment to the measured flaw will ensure a conservative bounding flaw depth value for dissimilar metal welds at Byron Station, Unit 2.
6.
DURATION OF PROPOSED ALTERNATIVE:
This relief request will be implemented during the remainder of the Byron Station, Unit 2 Third ten-year inservice inspection interval, which ends July 15, 2016.
7.
PRECEDENTS:
In a Gene Y. Suh to Christopher M. Crane, (Exelon Generation Company, LLC) letter dated February 25, 2005; the NRC authorized the same relief for Byron Unit 1, Docket No. 50-454 Relief Request 12R-50 (ML050450576).
8.
ATTACHMENTS None
IS!_Program P/an Unit 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-09 Revision 0 (Page3of3)
TABLE 1: APPLICABLE COMPONENTS WELD NUMBER DESCRIPTION WIN NUMBER FORMER ASME XI ITEM NUMBER CURRENT RJ-ISI ITEM NUMBER Unit 2 2RC-01-R/RPVS-A/F1 RPV Nozzle Safe-End Hot Leg Loop D 2RPV-1 B5.10 R1.15 2RC-01-R!RPVS-B/F1 RPV Nozzle Safe-End Cold Leg Loop D 2RPV-1 B5.10 R1.15 2RC-O1-R/RPVS-C/F1 RPV Nozzle Safe-End Cold Leg Loop C 2RPV-1 B5.1O Ri.15 2RC-Oi-R/RPVS-D/F1 RPV Nozzle Safe-End Hot Leg Loop C 2RFV-i B5.1O R1.15 2RC-Oi-R/RPVS-E/F1 RPV Nozzle Safe-End Hot Leg Loop B 2RPV-i B5.1O R1.15 2RC-0i-R/RPVS-F/Fi RPV Nozzle Safe-End Cold Leg Loop B 2RPV-1 B5.10 Ri.15 2RC-Oi-R/RPVS-G/F1 RPV Nozzle Safe-End Cold Leg Loop A 2RPV-i B5.10 Ri.15 2RC-Oi-R/RPVS-H/F1 RPV Nozzle Safe-End Hot Leg Loop A 2RPV-1 B5.10 Ri.15
Attachment B Byron Station Relief Request 13R-1O
IS! Program Plan Units 1 & 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-10 Revision 0 (Page 1 Of 19)
Request for Relief for Alternative Requirements for Dissimilar Metal Piping Welds Subject to Examination Using Procedures, Personnel, and Equipment Qualified to ASME Section Xl, Appendix VIII, Supplement 10 Criteria In Accordance with 10 CFR 50.55a(a)(3)(i)
ASME CODE COMPONENTS AFFECTED:
Code Class:
1
Reference:
ASME Section Xl, Appendix VIII, Supplement 10 Criteria Examination Category:
All Item Number:
All
==
Description:==
Alternative Requirements for Dissimilar Metal Piping Welds Subject to Examination Using Procedures, Personnel, and Equipment Qualified to ASME Section XI, Appendix VIII, Supplement 10 Criteria.
Components Dissimilar Metal Piping Welds APPLICABLE CODE EDITION AND ADDENDA:
The current inservice inspection program is based on the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code,Section XI, 2001 Edition through the 2003 Addenda.
Ultrasonic examination of applicable Class 1 and 2 components is governed by Appendix VIII, Performance Demonstration for Ultrasonic Examination Systems, of the ASME Code,Section XI, 1995 Edition with the 1996 Addenda.
APPLICABLE CODE REQUIREMENT:
The following paragraphs or statements are fromASME Section XI, Appendix VIII, Supplement 10 and identify the specific requirements that are included in this relief request.
Item 1
- Paragraph 1.1(b) states in part
- 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 - All flaws in the specimen set shall be cracks.
Item 3 - Paragraph 1.1 (d)(1) states - At least 50% of the cracks shall be in austenitic material. At least 50% of the cracks in austenitic material shall be contained wholly in weld or buttering material. At least 10% 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
- The numberof unflawed grading units shall be at least twice the number of flawed grading units.
Item 5 - Paragraph 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% and 30% of the nominal pipe wall thickness. Paragraph 1.4(b) distribution table requires 20% of the flaws to have depths between 10% and 30%.
Item 6 - Paragraph 2.0 first sentence states - 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.
Exelon Byron Station
IS! Program Plan Units 1 & 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-10 Revision 0 (Page 2 of 19)
Item 8 - Paragraph 2.2(c) states in part - 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 - For the depth sizing test, 80% 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 - 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-52-1 provides the false call criteria when the number of unflawed grading units is at least twice the number of flawed grading units.
REASON FOR REQUEST:
Relief is requested to use the following alternative requirements for implementation of Appendix VIII, Supplement 10 requirements. They will be implemented through the Performance Demonstration Initiative (PDI) Program.
As provided by the PDI, a copy of the proposed revision to Supplement 10 is attached (Attachment 2). It identifies the proposed alternatives and allows them to be viewed in context. It also identifies additional clarifications and enhancements for information.
PROPOSED ALTERNATIVE AND BASIS FOR USE:
Pursuant to 10 CFR 50.55a(a)(3)(i), in lieu of the requirements of ASME Section XI, 1995 Edition with the 1996 Addenda, Appendix VIII, Supplement 10, the proposed alternative discussed below shall be used. Compliance with the proposed alternatives will provide an adequate level of quality and safety for examination of the affected welds.
Item 1 - The proposed alternative to Paragraph 1.1(b) states:
The specimen set shall include the minimum and maximum pipe diameters and thicknesses for which the examination procedure is applicable. Pipe diameters within a range of 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 the nominal diameter minus 0.5 inch 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 - The proposed alternative to Paragraph 1.1(d) states:
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval 10 CFR 50.55a RELIEF REQUEST 13R-10 Revision 0 (Page 3 of 19)
At least 60% of the flaws shall be cracks, the remainder shall be alternative flaws. Specimens with IGSCC shall be used when available. Alternative flaws, if used, shall provide crack-like reflective characteristics and shall be limited to the case where implantation of cracks produces spurious reflectors that are uncharacteristic of actual flaws. Alternative flaw mechanisms shall have a tip width of less than or equal to 0.002 in. (.05 mm).
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.
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.
Item 3-The proposed alternative to Paragraph 1.1(d)(1) states:
At least 80% of the flaws shall be contained wholly in weld or buttering material. At least one and a maximum of 10% of the flaws shall be in ferritic base material. At least one and a maximum of 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. 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 - The proposed alternative to Paragraph 1.2(b) states:
Detection sets shall be selected from Table VIII-S10-1. The number of unflawed grading units shall be at least one and a half times the number of flawed grading units.
Technical Basis New Table VIII-S10-1 provides a statistically based ratio between the number of unflawed grading units and the number of flawed grading units. Based on information provided by the PDI, the proposed alternative reduces the ratio to 1.5 times to reduce the number of test samples to a more reasonable number. 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 VlII-S10-1.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval 10 CFR 50.55a RELIEF REQUEST I3R-10 Revision 0 (Page 4 of 19)
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 - The proposed alternative to Paragraph 2.0 first sentence states:
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 nozzle to safe end welds) impractical. The proposed alternative differentiates between ID and OD scanning surfaces, requires that they be conducted separately, and requires that flaws be concealed from the candidate.
Items 7 and 8 - The proposed alternatives to Paragraph 2.2(b) and 2.2(c) state:
... 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). 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.
Items 9 and 10 - The proposed alternative to Paragraph 2.3(a) and 2,3(b) states:
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.
Item 11
- The proposed alternative modifies the acceptance criteria of Table VIIl-S2-1 as follows:
Exelon Byron Station
ISI Program Plan Units 1 & 2~Third Interval 10 CFR 50.55a RELIEF REQUEST 13R-10 Revision 0 (Page 5 of IQ\\
10 1 TABLE VIlI-S7-1 PERFORMANCE DEMONSTRATION DETECTION TEST ACCEPTANCE CRITERIA Detection Test Acceptance Critera False Call Test Acceptance Criteria No. of Maximum No. of Flawed Minimum Unflawed Number Grading Units Detection Criteria Grading Units of False Calls 5
6 5
10 12 0
1
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6 14 1
8 7
16 2
9 7
16 2
10 11 12 13 14 15 16 17 18 19 20 8
9 9
10 10 11 12 12 13 13 14
~
15
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~
~27
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~30 46 32 33 3.-3 4_3 5...._3
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~-_-4
~4 t__4 75 8
Technical Basis - The proposed alternative adds new Table VIII-S10-1 above.
It is a modified version of Table Vlll-S2-1 to reflect the reduced number of unflawed grading units and allowable false calls. As provided by the PDI, as part of ongoing Code activities, Pacific Northwest National Laboratories has reviewed the statistical significance to this new Table VIII-Si0-1.
DURATION OF PROPOSED ALTERNATIVE:
Relief is requested for the Third Inspection Interval for Byron Station Units 1 and 2.
PRECEDENTS:
In a James W. Clifford, to John L. Skolds, (Exelon Generation Company, LLC) letter dated July 16, 2003; the NRC authorized the same relief for the entire Exelon Fleet (ML031970111).
For Byron Units 1 and 2, Docket No.s 50-454 and 50-455, this was identified as Relief Request l2R-45 for the Second Inspection Interval.
Exelon Byron Station
ISI Program Plan Units 1 &2, Third Interval 10 CFR 50.55a RELIEF REQUEST l3R-10 Revision 0 (Page 6 of 19)
ATTACHMENT SUPPLEMENTAL INFORMATION PROVIDED BY THE PERFORMANCE DEMONSTRATION INITIATIVE (PDI)
Exelon Byron Station
ISI Program Plan Units 1 & 2, ThirdInterval ATTACHMENT Page 7 of 19 SUPPLEMENT 10- QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING 1.0 SCOPE Supplement 10 is applicable to dissimilar metal piping welds examined from either the inside or outside surface. Supplement 10 is not applicable to piping welds containing supplemental corrosion resistant clad (CRC) applied to mitigate lntergranular Stress Corrosion Cracking (IGSCC).
A scope statement provides added clarity regarding the applicable range of each individual Supplement. The exclusion of CRC provides consistency between Supplement 10 and the recent revision to Supplement 2 (Reference BC 00-755).
Note, an additional change identifying CRC as in course of preparation is being processed separately.
1.0 SPECIMEN REQUIREMENTS 2.0 SPECIMEN REQUIREMENTS Renumbered Qualification test specimens shall meet the Qualification test specimens shall meet the No Change requirements listed herein, unless a set of requirements listed herein, unless a set of specimens is designed to accommodate specimens is designed to accommodate specific specific limitations stated in the scope of the limitations stated in the scope of the examination examination procedure (e.g., pipe size, weld procedure (e.g., pipe size, weld joint joint configuration, access limitations). The configuration, access limitations). The same same specimens may be used to demonstrate specimens may be used to demonstrate both both detection and sizing qualification, detection and sizing qualification.
1.1 General. The specimen set shall conform 2.1 General. The specimen set shall conform to Renumbered to the following requirements.
the following requirements.
(a) The minimum number of flaws in a test set shall be ten.
New, changed minimum number of flaws to 10 so sample set size for detection is consistent with length and depth sizing.
(a) Specimens shall have sufficient volume to (b) Specimens shall have sufficient volume to Renumbered minimize spurious reflections that may interfere minimize spurious reflections that may interfere with the interpretation process.
with the interpretation process.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 8 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (b) The specimen set shall include the minimum and maximum pipe diameters and thicknesses for which the examination procedure is applicable. Pipe diameters within a range of 0.9 to 1.5 times a nominal diameter (c) The specimen set shall include the minimum and maximum pipe diameters and thicknesses for which the examination procedure is applicable. Pipe diameters within a range of 1/2 in. (13 mm) of the nominal diameter shall be Renumbered, metricated, the change in pipe diameter tolerance provides consistency between Supplement 10 and the recent revision to Supplement 2 (Reference BC 00-755).
shall be considered equivalent. Pipe diameters considered equivalent. Pipe diameters larger larger than 24 in. shall be considered to be flat.
than 24 in. (610 mm) shall be considered to be When a range of thicknesses is to be flat. When a range of thicknesses is to be examined, a thickness tolerance of +/-25%is examined, a thickness tolerance of +/-25%is acceptable.
acceptable.
(c) The specimen set shall include examples of (d) The specimen set shall include examples of Renumbered, changed condition to the following fabrication condition:
the following fabrication conditions:
conditions.
(1) geometric conditions that normally require discrimination from flaws (e.g., counterbore or weld root conditions, cladding, weld buttering, remnants of previous welds, adjacent welds in (1) geometric and material conditions that normally require discrimination from flaws (e.g.,
counterbore or weld root conditions, cladding, weld buttering, remnants of previous welds, Clarification, some of the items listed relate to material conditions rather than geometric conditions. Weld repair areas were added as a result of recent field experiences.
close proximity);
adjacent welds in close proximity, and weld repair areas);
(2) typical limited scanning surface conditions (e.g., diametrical shrink, single-side access due (2) typical limited scanning surface conditions (e.g., weld crowns, diametrical shrink, single-Differentiates between ID and OD scanning surface limitations. Requires that ID and OD to nozzle and safe end external tapers).
side access due to nozzle and safe end external tapers for outside surface examinations; and internal tapers, exposed weld roots, and cladding conditions for inside surface examinations). Qualification requirements shall be satisfied separately for outside surface and inside surface examinations.
qualifications be conducted independently (Note, new paragraph 2.0 (identical to old paragraph 1.0) provides for alternatives when a set of specimens is designed to accommodate specific limitations stated in the scope of the examination procedure).
(d) All flaws in the specimen set shall be Deleted this requirement, because new cracks.
paragraph 2.3 below provides for the use of alternative flaws in lieu of cracks.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 9 of 19 SUPPLEMENT 10- QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENTREQUIREMENT PROPOSED CHANGE REASONING (1) At least 50% of the cracks shall be in austenitic material. At least 50% of the cracks in austenitic material shall be contained wholly in weld or buttering material. At least 10% of the cracks shall be in ferritic material. The remainder of the cracks may be in either austenitic or ferritic material.
2.2 Flaw Location. At least 80% of the flaws shall be contained wholly in weld or buttering material. At least one and a maximum of 10%
of the flaws shall be in ferritic base material. At least one and a maximum of 10% of the flaws shall be in austenitic base material, Renumbered and re-titled. Flaw location percentages redistributed because field experience indicates that flaws contained in weld or buttering material are probable and represent the more stringent ultrasonic detection scenario.
(2) At least 50% of the cracks in austenitic base material shall be either IGSCC or thermal fatigue cracks. At least 50% of the cracks in ferritic material shall be mechanically or thermally induced fatigue cracks.
2.3 Flaw Type.
(a) At least 60% of the flaws shall be cracks, the remainder shall be alternative flaws.
Specimens with IGSCC shall be used when available. Alternative flaws, if used, shall provide crack-like reflective characteristics and shall be limited to the case where implantation of cracks produces spurious reflectors that are uncharacteristic of actual flaws. Alternative flaw mechanisms shall have a tip width of less than or equal to 0.002 in. (.05 mm).
Renumbered and re-titled. Alternative flaws are required for placing axial flaws in the HAZ of the weld and other areas where implantation of a crack produces metallurgical conditions that result in an unrealistic ultrasonic response. This is consistent with the recent revision to Supplement 2 (Reference BC 00-755).
The 40% limit on alternative flaws is needed to support the requirement for up to 70%
axial flaws. Metricated.
(3) At least 50% of the cracks shall be coincident with areas described in (c) above, (b) At least 50% of the flaws shall be coincident with areas described in 2.1(d) above.
Renumbered. Due to inclusion of alternative flaws, use of cracks is no longer appropriate.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 10 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENTREQUIREMENT PROPOSED CHANGE REASONING 2.4 Flaw Depth. All flaw depths shall be greater than 10% of the nominal pipe wall thickness.
Flaw depths shall exceed the nominal clad thickness when placed in cladding. Flaws in the sample set shall be distributed as follows:
Flaw DeDth Minimum
(% Wall Thickness) Number of Flaws 10-30%
20%
31-60%
20%
61-100%
20%
At least 75% of the flaws shall be in the range of 10 to 60% of wall thickness.
Moved from old paragraph 1.3(c) and 1.4 and re-titled. Consistency between detection and sizing specimen set requirements (e.g., 20% vs. 1/3 flaw depth increments, e.g., original paragraph 1.3(c)).
1.2 Detection Specimens. The specimen set Renumbered and re-titled and moved to shall include detection specimens that meet the paragraph 3.1(a). No other changes.
following requirements.
(a) Specimens shall be divided into grading Renumbered to paragraph 3.1(a)(1). No units. Each grading unit shall include at least 3 other changes.
in, of weld length. If a grading unit is designed to be unflawed, at least 1 in, of unflawed material shall exist on either side of the grading unit. The segment of weld length used in one grading unit shall not be used in another grading unit. Grading units need not be uniformly spaced around the pipe specimen.
(b) Detection sets shall be selected from Table Moved to new paragraph 3.1(a)(2).
VIII-S2-1. The number of unflawed grading units shall be at least twice the number of flawed grading units.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 11 of 19 SUPPLEMENT 10- QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (c) Flawed grading units shall meet the Flaw depth requirements moved to new following criteria for flaw depth, orientation, and paragraph 2.4, flaw orientation requirements type.
moved to new paragraph 2.5, flaw type requirements moved to new paragraph 2.3, Flaw Type.
(1) All flaw depths shall be greater than 10% of Deleted, for consistency in sample sets the the nominal pipe wall thickness. At least 1/3 of depth distribution is the same for detection the flaws, rounded to the next higher whole and sizing.
number, shall have depths between 10% and 30% of the nominal pipe wall thickness.
However, flaw depths shall exceed the nominal clad thickness when placed in cladding. At least 1/3 of the flaws, rounded to the next whole number, shall have depths greater than 30% of the nominal pipe wall thickness.
(2) At least 30% and no more than 70% of the 2.5 Flaw Orientation.
Note, this distribution is applicable for flaws, rounded to the next higher whole (a) At least 30% and no more than 70% of the detection and depth sizing. Paragraph number, shall be oriented axially. The flaws, rounded to the next higher whole number, 2.5(b)(1) requires that all length-sizing flaws remainder of the flaws shall be oriented clrcumferentlally.
shall be oriented axially. The remainder of the flaws shall be oriented circumferentially.
be oriented circumferentially.
1.3 Length Sizing Specimens. The specimen Renumbered and re-titled and moved to new set shall include length sizing specimens that paragraph 3.2.
meet the following requirements.
(a) All length sizing flaws shall be oriented Moved, included in new paragraph 3.2(a).
circumferentially.
(b) The minimum number of flaws shall be ten.
Moved, included in new paragraph 2.1 above.
Exelon Byron Station
ISI Program Plan Units 1 & 2~Third Interval ATTACHMENT Page 12 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (c) All flaw depths shall be greater than 10% of Moved, included in new paragraph 2.4 the nominal pipe wall thickness. At least 1/3 of above after revision for consistency with the flaws, rounded to the next higher whole detection distribution.
number, shall have depths between 10% and 30% of the nominal pipe wall thickness.
However, flaw depth shall exceed the nominal clad thickness when placed in cladding. At least 1/3 of the flaws, rounded to the next whole number, shall have depths greater than 30% of the nominal pipe wall thickness.
1.4 Depth Sizing Specimens. The specimen Moved, included in new paragraphs 2.1, 2.3, set shall include depth sizing specimens that 2.4.
meet the following requirements.
(a) The minimum number of flaws shall be ten.
Moved, included in new paragraph 2.1.
(b) Flaws in the sample set shall not be wholly Moved, potential conflict with old paragraph contained within cladding and shall be 1.2(c)(1); However, flaw depths shall distributed as follows:
exceed the nominal clad thickness when placed in cladding. Revised for clarity and included in new paragraph 2.4.
Flaw Depth Minimum
(% Wall Thickness)
Number of Flaws Moved, included in paragraph 2.4 for consistent applicability to detection and sizing samples.
10-30%
20%
31 -60%
20%
61-100%
20%
The remaining flaws shall be in any of the above categories.
(b) Sizing Specimen sets shall meet the following requirements.
(1) All length-sizing flaws shall be oriented circumferentially.
Added for clarity.
Moved from old paragraph 1.3(a).
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 13 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (2) Depth sizing flaws shall be oriented as in 2.5(a).
Included for clarity. Previously addressed by omission (i.e., length, but not depth had a specific exclusionary statement).
2.0 CONDUCT OF PERFORMANCE 3.0 CONDUCT OF PERFORMANCE Renumbered DEMONSTRATION DEMONSTRATION The specimen inside surface and identification For qualifications from the outside surface, Differentiate between qualifications shall be concealed from the candidate. All the specimen inside surface and conducted from the outside and inside examinations shall be completed prior to identification shall be concealed from the surface.
grading the results and presenting the results candidate. When qualifications are to the candidate. Divulgence of particular performed from the inside surface, the flaw specimen results or candidate viewing of location and specimen identification shall be unmasked specimens after the performance obscured to maintain a blind test. All demonstration is prohibited.
examinations shall be completed prior to grading the results and presenting the results to the candidate. Divulgence of particular specimen results or candidate viewing of unmasked specimens after the performance demonstration is prohibited.
2.1 Detection Test. Flawed and unflawed 3.1 Detection Qualification.
Renumbered, moved text to paragraph grading units shall be randomly mixed 3.1(a)(3)
(a) The specimen set shall include detection specimens that meet the following requirements.
Renumbered, moved from old paragraph 1.2.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 14 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (1) Specimens shall be divided into grading units, Each grading unit shall include at least 3 in. (76 mm) of weld length. If a grading unit is designed to be unflawed, at least 1 in. (25 mm) of unflawed material shall exist on either side of the grading unit, The segment of weld length used in one grading unit shall not be used in another grading unit. Grading units need not be uniformly spaced around the pipe specimen.
(2) Detection sets shall be selected from Table VIII-S10-1. The number of unflawed grading units shall be at least one and a half times the number of flawed grading units.
~~~flawed and unflawed grading units shall be randomly mixed.
Renumbered, moved from old paragraph 1.2(a). Metricated. No other changes.
Moved from old paragraph 1.2(b). Table revised to reflect a change in the minimum sample set to 10 and the application of equivalent statistical false call parameters to the reduction in unflawed grading units.
Human factors due to large sample size.
Moved from old paragraph 2.1.
(b) Examination equipment and personnel are qualified for detection when personnel demonstrations satisfy the acceptance criteria of Table VIII Sb-i for both detection and false calls.
Moved from old paragraph 3.1. Modified to reflect the 100% detection acceptance criteria of procedures versus personnel and equipment contained in new paragraph 4.0 and the use of 1.5X rather than 2X unflawed grading units contained in new paragraph 3.1(a)(2). Note, the modified table maintains the screening criteria of the original Table Vlll-S2-1.
2.2 Length Sizing Test 3.2 Length Sizing Test Renumbered (a) The length sizing test may be conducted (a) Each reported circumferential flaw in the Provides consistency between Supplement separately or in conjunction with the detection detection test shall be length sized.
10 and the recent revision to Supplement 2 test.
(Reference BC 00-755).
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 15 of 19 SUPPLEMENT 10- QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (b) When the length sizing test is conducted (b) When the length sizing test is conducted in conjunction with the detection test, and less than ten circumferential flaws are detected, additional specimens shall be provided to the candidate such that at least ten flaws are sized. The regions containing a flaw to be sized may be identified to the candidate. The candidate shall determine the length of the flaw in each region.
Change made to ensure security of samples, consistent with the recent revision to Supplement 2 (Reference BC 00-755).
Note, 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.
in conjunction with the detection test, and less than ten circumferential flaws are detected, additional specimens shall be provided to the candidate such that at least ten flaws are sized. The regions containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the length of the flaw in each region.
(C) For a separate length sizing test, the (c) For a separate length sizing test, the regions of each specimen containing a flaw to be sized may be identified to the candidate. The candidate shall determine the length of the flaw in each region.
(d) Examination procedures, equipment, and personnel are qualified for length sizing when the RMS error of the flaw length measurements, as compared to the true flaw lengths, is less than or equal to 0.75 in. (19 mm).
Change made to ensure security of samples, consistent with the recent revision to Supplement 2 (Reference BC 00-755).
Moved from old paragraph 3.2(a) includes inclusion of when as an editorial change.
Metricated.
regions of each specimen containing a flaw to be sized shall be identified to the candidate. The candidate shall determine the length of the flaw in each region.
2.3 Depth SizinQ Test 3.3 Depth Sizing Test Renumbered (a) For the depth sizing test, 80% of the flaws (a) The depth sizing test may be conducted Change made to ensure security of samples, shall be sized at a specific location on the separately or in conjunction with the consistent with the recent revision to surface of the specimen identified to the detection test. For a separate depth sizing Supplement 2 (Reference BC 00-755).
candidate.
test, the regions of each specimen containing a flaw to be sized may be identified to the candidate. The candidate shall determine the maximum depth of the flaw in each region.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 16 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENT REQUIREMENT PROPOSED CHANGE REASONING (b) For the remaining flaws, the regions of each (b) When the depth sizing test is conducted Change made to be consistent with the specimen containing a flaw to be sized shall be in conjunction with the detection test, and recent revision to Supplement 2 (Reference identified to the candidate. The candidate shall less than ten flaws are detected, additional BC 00-755).
determine the maximum depth of the flaw in specimens shall be provided to the candidate each region.
such that at least ten flaws are sized. The regions of each specimen containing a flaw to be sized may be identified to the candidate.
The candidate shall determine the maximum depth of the flaw in each region.
(c) Examination procedures, equipment, and personnel are qualified for depth sizing when the RMS error of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125 in. (3 mm).
Changes made to ensure security of samples, consistent with the recent revision to Supplement 2 (Reference BC 00-755).
Moved from old paragraph 3.2(b).
Metricated.
3.0 ACCEPTANCE CRITERIA Delete as a separate category. Moved to new paragraph detection (3.1) and sizing 3.2 and 3.3.
3.1 Detection Acceptance Criteria.
Moved to new paragraph 3.1(b), reference Examination procedures, equipment, and changed to Table S10 from S2 because of personnel are qualified for detection when the the change in the minimum number of flaws results of the performance demonstration and the reduction in unflawed grading units satisfy the acceptance criteria of Table Vlll-S2-from 2X to 1.5X.
1 for both detection and false calls.
3.2 Sizing Acceptance Criteria Deleted as a separate category. Moved to new paragraph on length 3.2 and depth 3.3.
(a) Examination procedures, equipment, and Moved to new paragraph 3.2(d), included personnel are qualified for length sizing the word when as an editorial change.
RMS error of the flaw length measurements, as compared to the true flaw lengths, is less than or equal to 0.75 inch.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 17 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENTREQUIREMENT PROPOSED CHANGE REASONING (b) Examination procedures, equipment, and Moved to new paragraph 3.3(c).
personnel are qualified for depth sizing when the RMS error of the flaw depth measurements, as compared to the true flaw depths, is less than or equal to 0.125 in.
4.0 PROCED URE QUALIFICATION New Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACHMENT Page 18 of 19 SUPPLEMENT 10 QUALIFICATION REQUIREMENTS FOR DISSIMILAR METAL PIPING WELDS CURRENTREQUIREMENT PROPOSED CHANGE REASONING Procedure qualifications shall include the following additional requirements.
(a) The specimen set shall include the equivalent of at least three personnel sets.
Successful personnel demonstrations may be combined to satisfy these requirements.
(b) Detectability of all flaws within the scope of the procedure shall be demonstrated.
Length and depth sizing shall meet the requirements of paragraph 3.2 and 3.3.
(c) At least one successful personnel demonstration has been performed.
(d) To qualify new values of essential variables, at least one personnel qualification set is required.
New.
Based on experience gained in conducting qualifications, the equivalent of 3 personnel sets (i.e., a minimum of 30 flaws) is required to provide enough flaws to adequately test the capabilities of the procedure. Combining successful demonstrations allows a variety of examiners to be used to qualify the procedure. Detectability of each flaw within the scope of the procedure is required to ensure an acceptable personnel pass rate.
The last sentence is equivalent to the previous requirements and is satisfactory for expanding the essential variables of a previously qualified procedure.
Exelon Byron Station
ISI Program Plan Units 1 & 2, Third Interval ATTACH~~
Page 19 of 19 jlO TABLE VIII-S,Z-1 PERFORMANCE DEMONSTRATION DETECTION TEST ACCEPTANCE CRITERIA Detection Acceptance Test Critera False Call Test Acceptance Criteria No. of Maximum No. of Flawed Minimum Unflawed Number Grading Detection Grading of False Units Criteria Units Calls 5
6 7
8 9
10 5
é 6
7 7
8 10 12 14 16 18 ao 15
-0 1
~1 2
2 32 11 9
~.17 33 12 9
~-_18 33 13 10
~~20 4.....3 14 15 16 17 18 10 11 12 12 13
~.21 3~23
~
~27
~~29 5_3
~3
~
~4 19 13 38-30 20 14 4 8 Exelon Byron Station