ML091870432
| ML091870432 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 07/01/2009 |
| From: | Mims D Arizona Public Service Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 102-06029-DCM/SAB/RJR | |
| Download: ML091870432 (15) | |
Text
-A L A subsidiaryof Pinnacle West CapitalCorporation Dwight C. Mims Mail Station 7605 Palo Verde Nuclear Vice President Tel. 623-393-5403 P.O. Box 52034 Generating Station Regulatory Affairs and Plant Improvement Fax 623-393-6077 Phoenix, Arizona 85072-2034 102-06029-DCM/SAB/RJR July 01, 2009 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Reference:
U.S. Nuclear Regulatory Commission letter, "Final Safety Evaluation for Pressurized Water Reactor Owners Group (PWROG) Topical Report (TR)
WCAP-1 6168-NP, Revision 2, 'Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval' (TAC No. MC9768)," dated May 8, 2008.
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 Request for Relief from the American Society of Mechanical Engineers (ASME) Code, Section Xl, Reactor Vessel Weld Inspection Frequency -
Relief Request No. 40 Pursuant to 10 CFR 50.55a(a)(3)(i), Arizona Public Service Company (APS) hereby requests Nuclear Regulatory Commission (NRC) approval to increase the interval for performing the volumetric examination of certain reactor vessel pressure-retaining and full penetration welds at PVNGS Units 1, 2, and 3.
In the referenced letter, the NRC approved the Westinghouse Topical Report that provided the technical justification and regulatory basis for decreasing the frequency of volumetric examination by extending the ASME inservice inspection interval from the current 10 years to 20 years for ASME examination categories B-A and B-D reactor vessel welds. The required plant-specific information and justification to support the proposed inspection schedule is contained in the enclosure to this letter.
APS has concluded that the proposed alternative provides an acceptable level of quality and safety in accordance with 10 CFR 50.55a(a)(3)(i).
A member of the STARS (Strategic Teaming and Resource Sharing) Alliance fkC047 Callaway
- Comanche Peak 0 Diablo Canyon
- Palo Verde 0 San Onofre
- South Texas 0 Wolf Creek O
ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Request for Relief from the ASME Code,Section XI, Reactor Vessel Weld Inspection Frequency - Relief Request No. 40 Page 2 No commitments are being made to the NRC by this letter. Should you need further information regarding this relief request, please contact Russell A. Stroud, Licensing Section Leader, at (623) 393-5111.
Sincerely, DCM/RAS/RJR/gat
Enclosure:
Relief Request 40 cc: E. E. Collins Jr. NRC Region IV Regional Administrator J. R. Hall NRC NRR Project Manager R. I. Treadway NRC Senior Resident Inspector
ENCLOSURE Relief Request 40
10 CFR 50.55a Relief Request Number 40 Palo Verde Units 1, 2, and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)
--Alternative Provides Acceptable Level of Quality and Safety--
Background
On May 8, 2008, the NRC staff issued the Final Safety Evaluation (Reference 1) related to the Westinghouse Topical Report (TR) WCAP-16168-NP, Revision 2. The NRC found that WCAP-16168-NP, Revision 2, was acceptable for referencing in licensing applications for Combustion Engineering designed pressurized water reactors when requesting a decrease in frequency of inspections by extending the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code,Section XI, inservice inspection (ISI) interval from the current 10 years to 20 years for Category B-A and B-D reactor vessel welds. APS used Westinghouse Topical Report WCAP-1 6168-NP-A, Revision 2 (Reference 2) in the development of this submittal.
Previously, the Nuclear Regulatory Commission (NRC) staff approved Arizona Public Service Company's (APS') Relief Request (RR) No. 34, which deferred the volumetric examination requirement for certain reactor vessel pressure-retaining welds at Palo Verde, Units 1, 2, and 3, for one fuel cycle. The NRC's approval of RR No. 34 is documented by ADAMS Accession Nos. ML062490513, ML071140033, and ML082590556. Based upon the approved RR No. 34, the reactor vessel volumetric examinations were completed or scheduled as follows:
Unit 1 spring of 2010 (scheduled)
Unit 2 spring of 2008 (completed)
Unit 3 spring of 2009 (completed) 1.0 ASME Code Component(s) Affected The affected components are the Palo Verde Units 1, 2 and 3 reactor vessels. The following ASME BPV Code, Section Xl, examination categories and item numbers are from Table IWB-2500-1.
Code Class: 1 Examination Item No Description Category Pressure Retaining Welds in Reactor Vessel:
B-A B1 .11 Circumferential Shell Welds B-A BI.12 Longitudinal Shell Welds B-A B1.22 Meridional Shell Welds (Bottom Head only)
B-A B1 .30 Shell-to-Flange Weld Full Penetration Welded Nozzles in Vessels:
Page 1
Relief Request 40 B-D B3.90 Nozzle-to-Vessel Welds B-D B3.100 Nozzle Inner Radius Areas
2.0 Applicable Code Edition and Addenda
The third 10-year Interval Inservice Inspection (ISI) Program Plan complies with the 2001 Edition, 2003 Addenda, of the ASME BPV Code.
3.0 Applicable Code Requirement
Subarticle IWA-2432, "Inspection Program B," states, in part, that the inspection intervals shall comply with the following, except as modified by IWA-2430(d) and that inspection intervals are 10 year intervals.
Subarticle IWA-2430, "Inspection Intervals," (d) states, in part, that for components inspected under Program B, each of the inspection intervals may be extended or decreased by as much as 1 year. Adjustments shall not cause successive intervals to be altered by more than 1 year from the original pattern of intervals.
Subarticle IWB-2412, "Inspection Program B," requires volumetric examination of essentially 100% of the reactor pressure vessel pressure-retaining welds identified in Table IWB-2500-1 once every 10-year interval.
4.0 Reason for Request
APS is requesting this relief because the extension of the reactor vessel (RV) ISI interval to 20 years will prevent an estimated 2.98 man-rem of exposure and save APS considerable costs in outage duration and funding while providing an acceptable level of quality and safety.
5.0 Proposed Alternative and Basis for Use APS proposes to defer the ASME Code required subject examinations of the Palo Verde Units 1, 2, and 3 reactor vessel pressure-retaining and full penetration examination categories B-A and B-D welds.
Unit 1 The first inspection of these welds in Unit 1 was performed in 1999 with the next scheduled inspection originally due in 2009. However, the second inspection was deferred until 2010 by RR No. 34. APS is requesting deferral of the second inspection until 2016 plus or minus one refueling cycle which is consistent with the information provided to the Staff in the Pressurized Water Reactor Owners Group (PWROG) letter OG-06-356 (Reference 3).
Unit 2 The second inspection of these welds in Unit 2 was performed in 2008 with the next scheduled inspection due in 2018. APS is requesting deferral of the third Page 2
Relief Request 40 inspection until 2027 plus or minus one refueling cycle which is consistent with the PWROG letter OG-06-356.
Unit 3 The second inspection of these welds was performed in 2009 with the next scheduled inspection due in 2019. APS is requesting deferral of the third inspection until 2028 plus or minus one refueling cycle. This is a deviation from the information provided to the Staff in the PWROG letter OG-06-356.
This deviation is a result of APS complying with the requirements of RR No. 34 by performing the required examinations in 2009. Extending the Unit 3 reactor vessel volumetric weld examinations to the 2013 date proposed in PWROG letter OG 356 would have required an approved ASME relief request. APS determined that a second relief request to obtain a one fuel cycle deferral similar to the one previously obtained in RR No. 34 was not appropriate. It would, therefore, have been necessary to obtain a relief request by demonstrating that each of the Palo Verde plant specific parameters is bounded by the corresponding pilot plant parameters used in Westinghouse Topical Report WCAP-16168-NP-A, Revision 2, for Combustion Engineering Plants. This plant specific evaluation was not completed until March of 2009, which did not allow for sufficient time for APS to prepare and submit a relief request with subsequent NRC review in advance of the April 2009 Unit 3 refueling outage. Therefore, APS performed the volumetric weld examinations during the Unit 3 outage in April of 2009 and is now requesting to defer the third inspection required by the ASME Code for the reactor vessel welds in Unit 3 from 2019 to 2028.
The methodology used to demonstrate the acceptability of extending the ISI examinations for categories B-A and B-D welds based on a negligible change in risk is contained in Westinghouse Topical Report WCAP-16168-NP-A, Revision 2.
This methodology was used to develop a pilot plant analysis for Westinghouse, Combustion Engineering, and Babcock and Wilcox reactor vessel designs and is an extension of the work that was performed as part of the Nuclear Regulatory Commission Pressurized Thermal Shock (PTS) Risk Re-Evaluation (Reference 4).
The critical parameters for demonstrating that this pilot plant analysis is applicable on a plant specific basis, as identified in WCAP-16168-NP-A, Revision 2, are identified in the attached tables. By demonstrating that each plant specific parameter is bounded by the corresponding pilot plant parameter, the application of the methodology to Palo Verde reactor vessel is acceptable. The comparison of pilot plant parameters and plant specific parameters is shown in the attachment to this request.
6.0 Duration of Proposed Alternative This request proposes deferral of the volumetric examination requirement for certain Palo Verde reactor vessel pressure-retaining and full penetration welds identified in Section 1.0 of this request until 2016 for Unit 1, 2026 for Unit 2, and 2027 for Unit 3, plus or minus 1 refueling cycle.
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Relief Request 40 Last Inspection PWROG Proposed Date Scheduled Date 1 Inspection Date Palo Verde Unit 1 1999 2016 2016 Palo Verde Unit 2 2008 2008 2027 Palo Verde Unit 3 2009 2013 2028
- 1. These dates were based on information available in 2006.
7.0 Conclusion 10 CFR 50.55a(a)(3) states:
"Proposed alternatives to the requirements of paragraphs (c), (d), (e), (f), (g), and (h) of this section or portions thereof may be used when authorized by the Director of the Office of Nuclear Reactor Regulation. The applicant shall demonstrate that:
(i) The proposed alternatives would provide an acceptable level of quality and safety, or (ii) Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety."
The APS proposed extension of the inservice inspection interval for these examinations is based upon the alternative schedule being a negligible change in risk, as a result of satisfying the risk criteria in Regulatory Guide 1.174, and that the alternative schedule will continue to provide an acceptable level of quality and safety. Therefore, APS requests that the proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).
8.0 References
- 1. U.S. Nuclear Regulatory Commission letter, "Final Safety Evaluation for Pressurized Water Reactor Owners Group (PWROG) Topical Report (TR)
WCAP-1 6168-NP, Revision 2, 'Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval' (TAC No. MC9768)," dated May 8, 2008 (ADAMS Nos. ML081060051 and ML081060045).
- 2. Westinghouse Topical Report WCAP-1 6168-NP-A, Revision 2, "Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval," dated June 2008.
- 3. Pressurized Water Reactor Owners Group letter No. OG-06-356, "Plan for Plant Specific Implementation of Extended Inservice Inspection Interval per WCAP-1 6168-NP, Revision 1, 'Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval.' MUHP 5097-99, Task 2059," dated October 31, 2006.
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Relief Request 40
- 4. NUREG-1847, "Recommended Screening Limits for Pressurized Thermal Shock," dated March 2007.
- 5. SECY-07-0104, "Proposed Rulemaking - Alternative Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events (RIN 3150-AI01)," dated June 25, 2007.
9.0 Precedent Waterford Unit 3 June 12, 2009 ML091210375 Palisades Nuclear Plant February 11, 2009 ML090120896 Calvert Cliffs February 18, 2009 ML090490853 Verbal authorization for Relief Requests ISI-020 & 021 Written Approval April 8, 2009 ML090920077 DC Cook March 3, 2009 ML090720704 Verbal authorization for Relief Requests ISIR-29 & 30 Page 5
Attachment to Relief Request 40 Attachment to Relief Request 40 The following tables are taken from calculation CN-PCAM-07-1 1, Implementation of WCAP-16168-NP-A, Revision 2 for Palo Verde Units 1, 2, and 3, dated March 11, 2009.
Table 2.1-1 Critical Parameters for the Application of Bounding Analysis Palo Verde Unit 1 Pilot Plant Plant Specific Additional Basis Basis Evaluation Required Dominant Pressurized Thermal Shock (PTS) Transients in the NRC PTS Risk PTS Generalization NRC PTS Risk Study are Study Study No applicable Through Wall Cracking 3.16E-07 Events 6.82E-13 Events per No Frequency (TWCF) per year year Frequency and Severity of 13 Bounded by 13 Design Basis Transient heatup/cooldowns heatup/cooldowns per No per year year Cladding Layers Single Layer Single Layer No (Single/Multiple) SingleLayerSingleLayerNo Table 2.1-2 Additional Information Pertaining to Reactor Vessel Inspection Palo Verde Unit 1 Inspection methodology ASME Section XI and Regulatory Guide 1.150.
Number of past 1 inspection has been performed to date on the Category B-A and B-D welds inspections_____________________________________
All indications in the reactor vessel are acceptable per Section XI IWB-3500.
There is one flaw in the inner 1" of the Unit 1 reactor vessel beltline. It is Noumr owall located in the plate material and is circumferential in orientation. The through extent of this flaw provided is 0.174 in. Based on the volume of plate inspected in the beltline region for Palo Verde Unit 1, 29.83 flaws of this size are acceptable per the proposed PTS Rule in SECY-07-0104, June 25, 2007 (ADAMS Accession Number ML070570141) (Reference 5).
Proposed inspection The second inservice inspection was scheduled for 2008, but was deferred schedule for balance of until 2010 by Relief Request No. 34. Upon approval of this request, the plant life second inspection will be performed in 2016.
Page 1
Attachment to Relief Request 40 Table 2.1-3 Details of TWCF Calculation- Palo Verde Unit 1 @ 60 EFPY Inputs Reactor Coolant System Temperature, TRCS[°F]: N/A Twai [inches]: 11.19 Un- Fluence [1019 Region/Component Material Cu Ni CF F] .99 Irraated Neutron/cm 2 ,
Description /Flux Type [wt%] [wt%] [9F] Pos. RTND(U) E>1 MeV]
1 Plate M-6701-2 A 533B 0.060 0.610 37 1.1 40 2.84 2 Plate M-6701-1 A 533B 0.070 0.660 44. 1.1 30 2.84 3 Plate M-6701-3 A 533B 0.060 0.610 37 1.1 40 2.84 4 Plate M-4311-3 A 533B 0.030 0.640 20 1.1 -20 2.84 5 Plate M-4311-1 A 533B 0.040 0.650 26 1.1 -10 2.84 6 Plate M-4311-2 A 533B 0.030 0.620 20 1.1 -40 2.84 7 Axial Weld 101-124A Linde 0091 0.070 0.030 35.45 1.1 -50 1.67 8 Axial Weld 101-124B Linde 0091 0.070 0.030 35.45 1.1 -50 2.21 9 Axial Weld 101-124C Linde 0091 0.070 0.030 35.45 1.1 -50 2.21 10 Axial Weld 101-142A Linde 0091 0.040 0.040 27.8 1.1 -80 1.67 11 Axial Weld 101-142B Linde 0091 0.040 0.040 27.8 1.1 -80 2.21 12 Axial Weld 101-142C Linde 0091 0.040 0.040 27.8 1.1 -80 2.21 13 Circ. Weld 101-171 Linde 124 0.050 0.070 34.05 1.1 -70 2.84 Outputs Methodology Used to Calculate AT30: Regulatory Guide 1.99, Revision 2 Controlling Fluence [10TM Material Region RTMAx-xx Fluence AT30 ['F] TWCFO5.XX
- (From Above) [R] E>1 MeV] Factor Axial Weld - AW 1,3 544.65 2.21 1.215 44.96 3.59E-17 Circumferential Weld - CW 1,3 546.97 2.84 1.278 47.28 8.02E-28 Plate - PL 1,3 546.97 2.84 1.278 47.28 2.73E-13 TWCF9.TOTAL(aAwTWCFgAw+ aPLTWCF 95.PL+ acwTWCFw.cw): 6.82E-13 Page 2
Attachment to Relief Request 40 Table 2.2-1 Critical Parameters for the Application of Bounding Analysis Palo Verde Unit 2 Pilot Plant Plant Specific Additional Parameter Basis Basis Evaluation Required Dominant Pressurized Thermal Shock (PTS) Transients in the NRC PTS Risk PTS Generalization No NRC PTS Risk Study are, Study Study applicable Through Wall Cracking 3.16E-07 Events 7.OOE-13 Events per No Frequency (TWCF) per year year 13 Bounded by 13 Frequency and Severity of heatup/cooldowns heatup/cooldowns per No Design Basis Transient per year year Cladding Layers Single Layer Single Layer No (Single/Multiple)
Table 2.2-2 Additional Information Pertaining to Reactor Vessel Inspection Palo Verde Unit 2 Inspection methodology ASME Section Xl and Regulatory Guide 1.150.
Number of past 2 inspections have been performed to date on the Category B-A and B-D inspections welds All indications in the reactor vessel are acceptable per Section Xl IWB-3500.
Number of indications There are no flaws in the Unit 2 beltline. Therefore, the ISI results are found acceptable per the flaw limits of the proposed PTS Rule in SECY-07-0104, June 25, 2007 (ADAMS Accession Number ML070570141) (Reference 5).
Proposed inspection The third inspection is currently scheduled for 2018. It is proposed that the schedule forathird inservice inspection be performed in 2027.
plant life Page 3
Attachment to Relief Request 40 Table 2.2-3 Details of TWCF Calculation- Palo Verde Unit 2 @ 60 EFPY Inputs Reactor Coolant System Temperature, TRcs[°F]: N/A Twai [inches]: 11.19 Material R.G Un- Fluence [1019
- Region/Component /Fiux /lxCFCu Ni [°F] R.99 1.99 Irradiated ence[0 2 ,
Neutron/cm Description Type [wt%] [wt%] Pos. RTNDT(u) E>1 MeV]
1 Plate F-765-5 A 533B 0.030 0.650 20 1.1 10 3.14 2 Plate F-765-6 A 533B 0.040 0.670 26 1.1 10 3.14 3 Plate F-765-4 A 533B 0.030 0.670 20 1.1 -20 3.14 4 Plate F-773-1 A 533B 0.030 0.670 20 1.1 10 3.14 5 Plate F-773-2 A 533B 0.040 0.640 26 1.1 0 3.14 6 Plate F-773-3 A 533B 0.050 0.660 31 1.1 -60 3.14 7 Axial Weld 101-124A Linde 124 0.060 0.040 33.6 1.1 -60 1.89 8 Axial Weld 101-124B Linde 124 0.060 0.040 33.6 1.1 -60 2.46 9 Axial Weld 101-124C Linde 124 0.060 0.040 33.6 1.1 -60 2.46 10 Axial Weld 101-142A Linde 124 0.090 0.040 44.2 1.1 -80 1.89 11 Axial Weld 101-142B Linde 124 0.090 0.040 44.2 1.1 -80 2.46 12 Axial Weld 101-142C Linde 124 0.090 0.040 44.2 1.1 -80 2.46 13 Circ. Weld 101-171 Linde 124 0.030 0.070 26.55 1.1 -30 3.14 Outputs Methodology Used to Calculate AT3o: Regulatory Guide 1.99, Revision 2 Controlling Material Fluence [1019 Region # (From RTMAx-xx Neutron/cm 2, Fluence AT30 [°F] TWCF95-xx Above) [R] E> MeV]ctor Axial Weld - AW 2 501.97 2.46 1.242 32.28 3.59E-17 Circumferential Weld - CW 2 503.54 3.14 1.302 33.85 8.02E-28 Plate - PL 2 503.54 3.14 1.302 33.85 2.76E-15 TWCF9 5-TOTAL (aAwTWCF95-AW + OpLTVVCF 95-pL + acwTWCF9-cw): 7.OOE-15 Page 4
Attachment to Relief Request 40 Table 2.3-1 Critical Parameters for the Application of Bounding Analysis Palo Verde Unit 3 Pilot Plant Plant Specific Additional Basis Basis Evaluation Required Dominant Pressurized Thermal Shock (PTS) Transients in the NRC PTS Risk PTS Generalization No NRC PTS Risk Study are Study Study applicable Through Wall Cracking 3.16E-07 Events 2.27E-15 Events per No Frequency (TWCF) per year year Frequency and Severity of 13 Bounded by 13 Design Basis Transient heatup/cooldowns heatup/cooldowns per No per year year Cladding Layers Single Layer Single Layer No (Single/Multiple) SingleLayerSingleLayerNo Table 2.3-2 Additional Information Pertaining to Reactor Vessel Inspection Palo Verde Unit 3 Inspection methodology ASME Section XI and Regulatory Guide 1.150.
Number of past 2 inspections have been performed to date on the Category B-A and B-D inspections welds All indications in the reactor vessel are acceptable per Section XI IWB-3500.
Number of indications There are no flaws in the Unit 3 beltline. Therefore, the ISI results are found acceptable per the flaw limits of the proposed PTS Rule in SECY-07-0104, June 25, 2007 (ADAMS Accession Number ML070570141) (Reference 5).
Proposed inspection The third inspection is currently scheduled for 2019. It is proposed that the schedule for balance of third inspection be performed in 2028.
plant life Page 5
Attachment to Relief Request 40 Table 2.3-3 Details of TWCF Calculation- Palo Verde Unit 3 @ 60 EFPY Inputs Reactor Coolant System Temperature, TRCS[°F]: N/A Twaii [inches]: 11.19 MaeilR . Un- Fune[019 0 2
- Dsrpin/Flux Region/Component Material [w%
Cu w%
Ni CF] 1.99 R.G. RNeutron/cm Fluence [101 ,
Irradiated Description Type [wt%] [wt%] [OF] Pos. RTNDT(U) E>1 MeV]
[OF]
I Plate F-6407-4 A 533B 0.040 0.620 26 1.1 -30 3.32 2 Plate F-6407-5 A 533B 0.050 0.610 31 1.1 -20 3.32 3 Plate F-6407-6 A 533B 0.040 0.610 26 1.1 -20 3.32 4 Plate F-6411-1 A 533B 0.040 0.640 26 1.1 -40 3.32 5 Plate F-6411-2 A 533B 0.040 0.650 26 1.1 0 3.32 6 Plate F-6411-3 A 533B 0.040 0.660 26 1.1 -60 3.32 7 Axial Weld 101-124A Linde 124 0.030 0.060 25.9 1.1 -50 1.52 8 Axial Weld 101-124B Linde 124 .0.030 0.060 25.9 1.1 -50 2.70 9 Axial Weld 101-124C Linde 124 0.030 0.060 25.9 1.1 -50 2.70 10 Axial Weld 101-142A Linde 124 0.040 0.070 30.65 1.1 -50 1.52 11 Axial Weld 101-142B Linde 124 0.040 0.070 30.65 1.1 -50 2.70 12 Axial Weld 101-142C Linde 124 0.040 0.070 30.65 1.1 -50 2.70 13 Circ. Weld 101-171 Linde 124 0.050 0.070 34.05 1.1 -70 3.32 Outputs Methodology Used to Calculate AT30: Regulatory Guide 1.99, Revision 2 Controlling RTMAx-xx Fluence [219 Fluence AT30 Material Region # Neutron/cm2 , E>1 Factor [TF]
3 (From Above) [R] MeVF Axial Weld - AW 5 492.59 2.70 1.265 32.90 3.59E-17 Circumferential Weld - CW 5 493.87 3.32 1.315 34.18 8.02E-28 Plate - PL 5 493.87 3.32 1.315 34.18 8.71E-16 TWCF9-TOTAL (aAwTWCFs.Aw + aPLTWCF95 PL + acwTWCF5-cw): 2.27E-15 Page 6