ML062750371: Difference between revisions

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Safety Evaluation cc: See next page
Safety Evaluation cc: See next page


ML062750371                        *No significant change to SE input OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/APLB/BC NRR/CPNB OGC-NLO subject to edits NRR/LPL4/BC NAME    MThadani    LFeizollahi  LMrowca*      TChan*    TCampbell              DTerao DATE    10/3/06      10/3/06      10/2/06        10/2/06  10/4/06                10/5/06
ML062750371                        *No significant change to SE input OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/APLB/BC NRR/CPNB OGC-NLO subject to edits NRR/LPL4/BC NAME    MThadani    LFeizollahi  LMrowca*      TChan*    TCampbell              DTerao DATE    10/3/06      10/3/06      10/2/06        10/2/06  10/4/06                10/5/06 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RISK-INFORMED INSERVICE INSPECTION FOR SECOND 10-YEAR INTERVAL RELIEF REQUEST A-1 COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 2 TXU GENERATION COMPANY, LP DOCKET NO. 50-446
 
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RISK-INFORMED INSERVICE INSPECTION FOR SECOND 10-YEAR INTERVAL RELIEF REQUEST A-1 COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 2 TXU GENERATION COMPANY, LP DOCKET NO. 50-446


==1.0    INTRODUCTION==
==1.0    INTRODUCTION==

Latest revision as of 00:18, 14 March 2020

Relief Request A1; Extension of Risk-Informed Inservice Inspection Program Plan to Second 10-Year Interval
ML062750371
Person / Time
Site: Comanche Peak Luminant icon.png
Issue date: 10/05/2006
From: Terao D
NRC/NRR/ADRO/DORL/LPLIV
To: Blevins M
TXU Power
Thadani, M C, NRR/DORL/LP4, 415-1476
References
TAC MC9503
Download: ML062750371 (12)


Text

October 5, 2006 Mr. M. R. Blevins Senior Vice President &

Chief Nuclear Officer TXU Power Attn: Regulatory Affairs Department P. O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION, UNIT NO. 2: RELIEF REQUEST A-1; EXTENSION OF RISK-INFORMED INSERVICE INSPECTION PROGRAM PLAN TO SECOND 10-YEAR INTERVAL (TAC NO. MC9503)

Dear Mr. Blevins:

By letter dated December 15, 2005, supplemented by letters dated June 27, August 23, and September 15, 2006, TXU Generation Company, LP, the licensee for Comanche Peak Steam Electric Station (CPSES), submitted to the U.S. Nuclear Regulatory Commission (NRC) a request for relief from American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code),Section XI, examination requirements for inservice inspection (ISI) of Class 1 and Class 2 piping welds. Relief is requested for the second 10-year ISI interval of CPSES, Unit 2. The licensee had previously submitted a risk-informed inservice inspection (RI-ISI) program plan for the second 10-year interval of Unit 1 and first 10-year interval of Unit 2. As an alternative to ASME Code requirements for Class 1 and Class 2 piping, the licensee requested authorization to extend the RI-ISI program plan for CPSES, Unit 2 to the second 10-year ISI interval.

The CPSES RI-ISI program was previously submitted to the NRC by letter dated February 15, 2001, and supplemented in a letter dated July 20, 2001, and an e-mail dated August 22, 2001.

The CPSES RI-ISI program was reviewed and approved by the NRC for use during the first 10-year ISI interval of Unit 2 in a letter dated September 28, 2001.

The NRC staff has reviewed the licensees submittal. Based on the review of the information provided by the licensee, and the licensees plans to incorporate any potential future requirements of NRC-approved guidance on thermal fatigue management for assessing thermal stratification, cycling and striping, the NRC staff has determined that the proposed alternative provides an acceptable level of quality and safety.

Accordingly, the proposed alternative is authorized pursuant to paragraph 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations for the second 10-year ISI interval of CPSES,

M. R. Blevins Unit 2. All other ASME Code requirements for which relief has not been specifically requested and authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector. The NRC staffs safety evaluation is enclosed.

Sincerely,

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-446

Enclosure:

Safety Evaluation cc: See next page

ML062750371 *No significant change to SE input OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/APLB/BC NRR/CPNB OGC-NLO subject to edits NRR/LPL4/BC NAME MThadani LFeizollahi LMrowca* TChan* TCampbell DTerao DATE 10/3/06 10/3/06 10/2/06 10/2/06 10/4/06 10/5/06 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RISK-INFORMED INSERVICE INSPECTION FOR SECOND 10-YEAR INTERVAL RELIEF REQUEST A-1 COMANCHE PEAK STEAM ELECTRIC STATION, UNIT 2 TXU GENERATION COMPANY, LP DOCKET NO. 50-446

1.0 INTRODUCTION

By letter dated December 15, 2005 (Reference 1, the submittal), supplemented by letters dated June 27, August 23, and September 15, 2006 (References 10, 11, and 12, respectively), TXU Generation Company, LP ( the licensee), requested U.S. Nuclear Regulatory Commission (NRC) authorization to extend the risk-informed inservice inspection (RI-ISI) program plan for Comanche Peak Steam Electric Station (CPSES), Unit 2 to the second 10-year inservice inspection (ISI) interval. The CPSES RI-ISI program was initially submitted to the NRC by letter dated February 15, 2001 (Reference 2). The program was supplemented in a letter dated July 20, 2001 (Reference 3), and by an e-mail dated August 22, 2001 (Reference 4).

The CPSES RI-ISI program was reviewed and approved by the NRC for use during the first 10-year ISI interval in a letter dated September 28, 2001 (Reference 5).

The licensee considered relevant information since the development of the original program and reviewed and updated the RI-ISI program, reflecting the new information. The licensees current submittal proposes to extend the updated RI-ISI program to the second 10-year ISI interval of CPSES, Unit 2.

2.0 REGULATORY EVALUATION

Title 10 of the Code of Federal Regulations (10 CFR), paragraph 50.55a(g) specifies that ISI of nuclear power plant components shall be performed in accordance with the requirements of the American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code (Code),

Section XI, except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Paragraph 50.55a(a)(3) of 10 CFR 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.

The licensees RI-ISI program plan, as outlined in References 2, 3, and 4, was developed in accordance with the methodology contained in the Electric Power Research Institutes (EPRIs) report EPRI TR-112657, Revision B-A, (Reference 6, the topical) which was reviewed and approved by the NRC staff. The CPSES RI-ISI program is an alternative pursuant to 10 CFR 50.55a(a)(3)(i). In the submittal, the licensee requests NRC authorization to continue the implementation of an RI-ISI piping program for the second 10-year ISI interval at CPSES, Unit 2. The scope of the RI-ISI program is limited to the inspection of ASME Code Class 1 and 2 piping welds (ASME Code,Section XI Categories B-F, B-J, C-F-1, and C-F-2).

3.0 TECHNICAL EVALUATION

The licensee is requesting relief to use the proposed RI-ISI program plan in the second 10-year ISI interval instead of the ASME Code,Section XI, program for piping. An acceptable RI-ISI program plan is expected to meet the five key principles discussed in Regulatory Guide (RG) 1.178 (Reference 7), Standard Review Plan (SRP) 3.9.8 (Reference 8), and EPRI TR-112657 (Reference 6); as stated below.

1. The proposed change meets the current regulations unless it is explicitly related to a requested exemption or rule change.
2. The proposed change is consistent with the defense-in-depth philosophy.
3. The proposed change maintains sufficient safety margins.
4. When proposed changes result in an increase in Core Damage Frequency (CDF) or risk, the increases should be small and consistent with the intent of the Commissions Safety Goal Policy Statement.
5. The impact of the proposed change should be monitored by using performance measurement strategies.

The first principle is met in this relief request because an alternative ISI program may be authorized pursuant to 10 CFR 50.55a(a)(3)(i) and, therefore, an exemption request is not required. The second and third principles require assurance that the alternative program is consistent with the defense-in-depth philosophy and that sufficient safety margins are maintained, respectively. Assurance that the second and third principles are met is based on the application of the approved methodology and not on the particular inspection locations selected.

As described in Reference 2 and approved by the NRC staff in Reference 5, the CPSES RI-ISI program is a living program that requires periodic updating, and that, at a minimum, risk ranking of piping segments will be reviewed on an ASME-period basis. In its submittal, the licensee describes the aspects considered during the program update review, in accordance with Nuclear Energy Institute (NEI) 04-05, Living Program Guidance To Maintain Risk-Informed Inservice Inspection Programs For Nuclear Plant Piping Systems (Reference 9), and the

results of the review. The licensees use of NEI 04-05, which provides guidance for a living program, is consistent with the defense-in-depth philosophy.

The licensee also describes three significant changes resulting from applying the aforementioned methodology to the program applicable to the second 10-year ISI interval:

1. A 2004 update to the probabilistic risk assessment (PRA) caused a change in the consequence rank of four consequence segments comprising at least six pipe segments in the safety injection system (SIS) from Medium to High (specifically from Risk Category 6a to Risk Category 4 (no degradation mechanisms)). In Reference 12 the licensee further explains that this increase in consequence rank for these segments constitutes an increase of 142 SIS elements in Risk Category 4. Because the topical report requires inspection of at least 10 percent of a population of Risk Category 4 (Medium Risk) elements, the required number of RI-ISI inspections for SIS Risk Category 4 was increased by 15. This increase in RI-ISI-required inspections is reflected in Table 1 of the submittal, page 4 of 6, and enhances defense-in-depth.
2. This same PRA update also caused a change in the consequence rank of four consequence segments in the feedwater system (FWS) from Medium to High, resulting in a re-categorizing of the overall risk of a number of FWS segments from Risk Category 6a to Risk Category 4. Although the precise number of pipe segments included within the four consequence segments is not given, the licensee states that the combined total of SIS and FWS pipe segments that were re-ranked is 14. Table 1 of the submittal indicates that this increase in consequence rank for these FWS segments constitutes an increase of 112 FWS elements in Risk Category 4. (There were previously none of these elements in Risk Category 4.) The table also indicates that there will be 12 required RI-ISI inspections of FWS Risk Category 4 elements in the second interval, which complies with the required 10 percent sampling rate. The increase in consequence ranking and inspections provide enhanced defense-in-depth.
3. The code of record for the second 10-year ISI interval is being changed from the 1986 Edition to the 1998 Edition through 2000 addenda of ASME Code,Section XI. This change reduces the inspection exemption for Class 2 AFW piping from 4 nominal pipe size (NPS) to 11/2 NPS. As a result, the 4-NPS Class 2 AFW piping from the outboard isolation valves to where they connect to the four main feedwater lines was added to the scope of the CPSES, Unit 2, ISI program, and consequently to the RI-ISI program. As indicated in Table 1 of the submittal, this resulted in 81 elements in the AFW system being included in the RI-ISI program for the first time. The four piping segments that comprise these elements were found to be of High Consequence, but susceptible only to the flow-accelerated corrosion (FAC) degradation mechanism. Because the licensee manages FAC under an augmented inspection program, these segments were placed in Risk Category 4 (Medium), requiring a 10 percent inspection sampling rate. Hence, Table 1 of the submittal reflects that nine of these welds were selected for examination.

Maintaining the FAC program under an augmented inspection program enhances the defense-in -depth and ensures sufficient safety margins.

The locations for the 21 inspections noted in paragraphs (2) and (3) above to be added to the RI-ISI program for the second interval were described as being susceptible to the FAC degradation mechanism. The licensee states in Reference 12 that it does not intend to credit the examinations performed for the CPSES, Unit 2, FAC augmented inspection program toward the RI-ISI inspection count, but will instead perform separate ultrasonic examinations, noting that the purpose of FAC examinations is to monitor for wall thinning. Provision of a separate ultra-sonic program enhances the defense-in-depth, and ensures sufficient safety margins.

In addition, the licensee indicates in Reference 12 that it will follow through with its deviation from the topical reports guidance for assessing the thermal stratification, cycling, and striping (TASCS) degradation mechanism by reviewing and incorporating, after completion of the assessment of thermal fatigue and TASCS in accordance with the requirements of EPRI Materials Reliability Program (MRP-146), the results into the CPSES, Unit 2, ISI Program Plan.

The NRC staff expects the licensee to incorporate the requirements of NRC-approved guidance on thermal fatigue management for assessing TASCS, regardless of the issued document, into the CPSES, Unit 2, ISI Program Plan. Addressing the deviations from topical report will ensure that sufficient safety margin will be maintained.

The NRC staff finds the licensees positions and the licensee-described re-evaluation of its RI-ISI program to be consistent with the methodology approved for use in the first 10-year inspection interval. Therefore, the second and third principles are met.

The fourth principle requires an estimate of the change in risk, which is dependent on the location of inspections in the proposed ISI program compared to the location of inspections that would be inspected using the requirements of ASME Code,Section XI. The licensee reports in the submittal that a new risk impact analysis was performed, and the revised program continues to represent a risk reduction when compared to the last deterministic Section XI inspection program. The licensee indicates that the original RI-ISI program provided a reduction of 9.73E-09/yr in regards to CDF and 3.91E-09/yr in regards to large early release frequency (LERF), while the revised program for the second interval will provide a reduction of 6.91E-09/yr in regards to CDF and 4.26E-09/yr in regards to LERF. The smaller reduction in CDF, despite the substantial increase in required inspections for the upcoming interval, is due primarily to a decreased upper bound CDF in the revised PRA. The previous upper bound value was 1.16E-02/yr, while the revised value is 7.52E-03/yr.

The topical report requires that a change in risk measurement must consider the discontinuance of ASME Code-required inspections, as well as any new inspections resulting from the application of its methodology. Because of the inclusion of new AFW piping within the ASME Code,Section XI, scope in the second ISI interval, the number of required inspections under a traditional ASME Code,Section XI, program would have increased. However, there is a corresponding increase in the number of required inspections under the RI-ISI program, as discussed in paragraph (3) above. Because the risk categorization of this piping placed it within a 10% sampling scheme, and because this same (ASME Class 2) piping would be under a 7.5% sampling scheme under the traditional ASME Code,Section XI, program, the number of required inspections for this incremental scope of piping under RI-ISI exceeds that under the traditional ASME Code,Section XI, program. Hence, the difference in the number of required inspections for the second interval between the traditional ASME Code,Section XI, and RI-ISI programs has, in all likelihood, decreased, which would imply a negative influence on the

change of risk between the two programs (i.e., RI-ISI, relative to the traditional ASME Code,Section XI, ISI program, provides for increased safety in the second interval as compared with the first interval).

The licensee states in Reference 12 that all major issues (i.e., Level A and B Facts and Observations (F&Os)) from the Westinghouse Owners Group (WOG) Peer Review of 2002, which was conducted after the original RI-ISI evaluation, have been addressed and incorporated into the current CPSES PRA model. In addition, the licensee also notes that since Revision 2 of the model (which addressed most of the Level A and B F&Os) was issued, it has performed yet another periodic update to the CPSES PRA model, completing this project in 2005. This update also included other significant changes and revised methodologies, based on a gap assessment using the ASME PRA Standard (Reference 13) for guidance. The remaining outstanding WOG Peer Review Level A and B F&Os were addressed during this update. Following this latest update (i.e., Revision 3 to the CPSES PRA model) the licensee, in accordance with Reference 13 guidance for PRA upgrades, initiated another independent industry peer review with a team of four highly-experienced PRA practitioners. The licensee states that this team identified no new Level A or B F&Os. The licensee also indicates that this current (Revision 3B) model was submitted in support of the Mitigating Systems Performance Indicators (MSPI) initiative. It notes that while some candidate outliers based on monitored equipment Birnbaum values were identified, the licensee was able to provide adequate rationale for them, and successfully defended the current model as technically adequate for the generation of risk-based MSPI metrics. The NRC staff reviewed the WOG Peer Review Level A and B F&Os and their resolutions, provided to the staff in Reference 12, and concluded that the licensee did adequately address them.

The licensee states in Reference 12 that this current version (Revision 3B) of the PRA model is used in support of the RI-ISI process. Hence, the NRC staff concludes that changes in CDF and in LERF were re-calculated using a revision of the licensees PRA that has received scrutiny such that any remaining errors or inappropriate assumptions are of a minor nature and will not invalidate the general results or conclusions of a change in risk evaluation.

Given the above considerations, and considering that estimates of the change in CDF and LERF are calculated in the final phase of the RI-ISI methodology, and are intended only to provide additional assurance that aggregate changes in risk will be acceptable (Reference 6),

the needed accuracy of the change in risk calculations does not warrant developing a new ASME program for the new code of record simply to be used as a new baseline and then discarded. Therefore, the NRC staff finds that the change of risk estimate between the RI-ISI program proposed for the second interval and the ASME program based on the code of record from which relief was granted in Reference 5 is appropriate and acceptable. The licensee reports in the submittal (and further substantiates with the above CDF/LERF change values) that the RI-ISI program continues to meet EPRI TR-112657 and RG 1.174 risk acceptance criteria. Hence, no deviation from the risk acceptance criteria was identified, and the NRC staff finds that the licensees process provides assurance that the fourth key principle is met.

With regard to the fifth principle, Section 3.6.6.1 of the topical report states, in part, that the service history and susceptibility review and ongoing industry events reviews assure that the industry trends are being monitored to assure that if an unexpected or new mechanism is identified, or a new component is identified as susceptible to an existing degradation

mechanism, the RI-ISI program will be updated to reflect that change. The program update will incorporate any additional inspections mandated by the NRC, as well as those inspections deemed appropriate by the industry groups addressing the specific issues.

In addition to monitoring industry experience, the licensee states that the RI-ISI program will be subject to the review and update guidance of NEI 04-05 (Reference 9).

Due to recent and ongoing issues related to degradation due to pressurized-water stress corrosion cracking (PWSCC) in components that contain alloy 600/82/182, the NRC staff requested that the licensee provide information related to welds containing alloy 82/182. The licensee participated in a teleconference to discuss this issue, the results of which are documented in a letter dated August 23, 2006 (Reference 11), which states that 10 of the 14 welds containing alloy 82/182 material will be inspected under the RI-ISI program. These welds include eight reactor vessel safe-end to reactor vessel nozzle hot/cold leg welds, and two pressurizer safe-end to pressurizer nozzle welds. The remaining four pressurizer safe-end to pressurizer nozzle welds will be addressed in an augmented inspection program for CPSES, Unit 2. The licensee also states in Reference 11 that all examinations of the welds will follow the requirements of MRP-139 and will be treated like ASME Code,Section XI, examinations, with regards to procedures used, personnel qualifications, and coverage requirements. The licensee states that PWSCC will be considered as a degradation mechanism for dissimilar metal welds, and will be addressed in the next RI-ISI evaluations/updates for Units 1 and 2, which are scheduled for 2007.

Based on the licensees description of its processes to review service history and industry events and issues, and given the above example where the licensee is conducting additional inspections in response to a recent industry issue, the NRC staff concludes that the RI-ISI program continues to be a living program, and that the fifth key principle is met.

Based on the above discussion, the NRC staff finds that the five key principles of risk-informed decisionmaking are ensured by the licensees proposed second 10-year RI-ISI interval program plan and, therefore, the proposed program for the second 10-year ISI inspection interval is acceptable.

4.0 CONCLUSION

S Based on the information provided by the licensee, and the licensees incorporation of any potential future requirements of NRC-approved guidance on thermal fatigue management for assessing TASCS, the NRC staff concludes that the proposed alternative provides an acceptable level of quality and safety.

Accordingly, the requested alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the second 10-year ISI interval of CPSES, Unit 2. All other ASME Code requirements for which relief has not been specifically requested and authorized herein by the NRC staff remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

5.0 REFERENCES

1. Letter from Mike Blevins, TXU Power, dated December 15, 2005, to the U.S. Nuclear Regulatory Commission, Comanche Peak Steam Electric Station (CPSES) Docket No. 50-446 Relief Request A-1 for the Unit 2 Inservice Inspection for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds (Interval Start Date - August 3, 2004, Second Interval), Agencywide Documents Access and Management System (ADAMS)

Accession No. ML053630046.

2. Letter from C. Lance Terry, TXU Power, dated February 15, 2001, to the U.S. Nuclear Regulatory Commission, Comanche Peak Steam Electric Station (CPSES) Docket Nos. 50-445 and 50-446 Relief Request for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds, ADAMS Accession No. ML010520269.
3. Letter from C. Lance Terry, TXU Power, dated July 20, 2001, to the U.S. Nuclear Regulatory Commission, Comanche Peak Steam Electric Station (CPSES) Docket Nos. 50-445 and 50-446 Response to Request for Additional Information Regarding Relief Request for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Cl Class 1 and 2 Piping Welds (TAC Nos. MB1201 and MB1202), ADAMS Accession No. ML012050350.
4. E-mail from Obaid Bhatty to Jack Donohew, Project Manager, U.S. Nuclear Regulatory Commission, dated August 22, 2001, Re: Additional Questions on CPSES RI-ISI Application, ADAMS Accession No. ML012360194.
5. Letter from the U.S. Nuclear Regulatory Commission, dated September 28, 2001, to C. Lance Terry, TXU Power, Comanche Peak Steam Electric Station (CPSES), Units 1 and 2 - Approval of Relief Request for Application of Risk-Informed Inservice Inspection Program for American Society of Mechanical Engineers Boiler and Pressure Vessel Code Class 1 and 2 Piping (TAC Nos. MB1201 and MB1202), ADAMS Accession No. ML012710112.
6. EPRI TR-112657, Revision B-A, Revised Risk-Informed Inservice Inspection Evaluation Procedure, Final Report, December 1999.
7. NRC RG 1.178, An Approach for Plant-Specific Risk-Informed Decisionmaking for Inservice Inspection of Piping, September 2003.
8. NRC NUREG-0800, Chapter 3.9.8, Risk-Informed Inservice Inspection of Piping, September 2003.
9. NEI 04-05, Living Program Guidance To Maintain Risk-Informed Inservice Inspection Programs For Nuclear Plant Piping Systems, April 2004.
10. Letter from Mike Blevins, TXU Power, dated June 27, 2006, to the U.S. Nuclear Regulatory Commission, Comanche Peak Steam Electric Station (CPSES) Docket No. 50-446 Response to Request for Additional Information, Relief Request A-1 for the

Unit 2 Inservice Inspection for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds (Interval Start Date - August 3, 2004, Second Interval) TAC Number MC9503, ADAMS Accession No. ML061990400.

11. Letter from Mike Blevins, TXU Power, dated August 23, 2006, to the U.S. Nuclear Regulatory Commission, Comanche Peak Steam Electric Station (CPSES) Docket No. 50-446 Revised Response to Request for Additional Information, Relief Request A-1 for the Unit 2 Inservice Inspection for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds (Interval Start Date - August 3, 2004, Second Interval) TAC Number MC9503, ADAMS Accession No. ML062420238.
12. Letter from Mike Blevins, TXU Power, dated September 15, 2006, to the U.S. Nuclear Regulatory Commission, Comanche Peak Steam Electric Station (CPSES) Docket No. 50-446 Response to Request for Additional Information Regarding Relief Request A-1 for the Unit 2 Inservice Inspection for Application of an Alternative to the ASME Boiler and Pressure Vessel Code Section XI Examination Requirements for Class 1 and 2 Piping Welds (Interval Start Date - August 3, 2004, Second Interval) TAC Number MC9503, ADAMS Accession No. ML062650133
13. American Society of Mechanical Engineers,Standard for Probabilistic Risk Assessment for Nuclear Power Plant Applications, April 5, 2002.

Principal Contributors: M. Melnicoff T. Lupold Date: October 5, 2006

Comanche Peak Steam Electric Station cc:

Senior Resident Inspector Mr. Richard A. Ratliff, Chief U.S. Nuclear Regulatory Commission Bureau of Radiation Control P. O. Box 2159 Texas Department of Health Glen Rose, TX 76403-2159 1100 West 49th Street Austin, TX 78756-3189 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Mr. Brian Almon 611 Ryan Plaza Drive, Suite 400 Public Utility Commission Arlington, TX 76011 William B. Travis Building P. O. Box 13326 Mr. Fred W. Madden, Director 1701 North Congress Avenue Regulatory Affairs Austin, TX 78701-3326 TXU Generation Company LP P. O. Box 1002 Ms. Susan M. Jablonski Glen Rose, TX 76043 Office of Permitting, Remediation and Registration George L. Edgar, Esq. Texas Commission on Environmental Morgan Lewis Quality 1111 Pennsylvania Avenue, NW MC-122 Washington, DC 20004 P. O. Box 13087 Austin, TX 78711-3087 County Judge P. O. Box 851 Terry Parks, Chief Inspector Glen Rose, TX 76043 Texas Department of Licensing and Regulation Environmental and Natural Boiler Program Resources Policy Director P. O. Box 12157 Office of the Governor Austin, TX 78711 P. O. Box 12428 Austin, TX 78711-3189 December 2004