CP-201700120, Relief Request 2B3-1 Third Ten Year Inservice Inspection Interval from 10 CFR 50.55a Inspection Requirements Due to Geometric Limitations
| ML17054C361 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/14/2017 |
| From: | Sewell S Luminant Power |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| CP-201700120, TXX-17023 | |
| Download: ML17054C361 (12) | |
Text
II Steven K. Sewell Senior Director of Engineering & Regulatory Affairs Steven.Sewell@Luminant.com Luminant Power P 0 Box 1002 Luminant 6322 North FM 56 Glen Rose, TX 76043 CP-201700120 T:XX-17023 Ref:
T 254 897 6113 c 817 776 0798 F 254 897 6652 10CFRS0.55a(z)(l)
February 14, 2017 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Director, Office of Nuclear Reactor Regulation Washington, DC 20555-0001
SUBJECT:
COMANCHE PEAK NUCLEAR POWER PLANT DOCKET NO. 50-446 RELIEF REQUEST 2B3-1 FOR THE UNIT 2 THIRD TEN YEAR INSERVICE INSPECTION INTERVAL FROM 10 CFR 50.55a INSPECTION REQUIREMENTS DUE TO GEOMETRIC LIMIT A TIO NS THIRD INTERVAL START DATE: AUGUST 3, 2014 THIRD INTERVAL END DATE: AUGUST 2, 2023
REFERENCES:
- 1. Letter logged T:XX-12002 dated January 5, 2012, from Rafael Flores to the NRC submitting Relief Request No. A-2 for the Unit 2 Second 10 Year ISi Interval from 10CFR50.55a Inspection Requirements due to Geometric Limitations
- 2. Letter logged T:XX-12080 dated June 13, 2012, from Rafael Flores to the NRC submitting Response to Request for Additional Information for Relief Request No. A-2
- 3. NRC Letter dated August 16, 2012 from Michael T. Markley to Rafael Flores concerning Comanche Peak Nuclear Power Plant Unit 2-Request for Relief A-2 from Inspection Requirements on Reactor Pressure Vessel Head Penetration Nozzles due to Geometric Limitations for the Second 10-Year Inservice Inspection Interval
Dear Sir or Madam:
Pursuant to 10 CFR 50.55a(z)(l), Vistra Operations Company LLC ("Vistra OpCo") hereby submits Relief Request 2B3-1 for Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 for the third ten year inservice inspection interval (see Enclosure). Vistra OpCo has determined that certain inspection requirements of ASME Code Case N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration Welds,Section XI, Division l," are impractical due to geometric limitations.
Specifically, relief is requested from the minimum coverage requirements for ultrasonic examination provided by American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),
Code Case N-729-1, Alternative Examination Requirements for PWR [Pressurized-Water Reactor]
Reactor Vessel Upper Heads with Nozzles Having Pressure-Retaining Partial-Penetration Welds, Section ftDLt7 r0 f.l-
U. S. Nuclear Regulatory Commission TXX-17023 Page 2 of 2 02/14/2017 XI, Division l," for control rod drive mechanism nozzles 74 through 78. The proposed alternative provides an acceptable level of quality and safety.
A similar relief request was submitted for the Unit 2 second ten year inservice inspection interval via References 1 and 2. Reference 3 documented the NRC review of the previous relief request.
No undue risk to the public health and safety is presented by this request.
Vistra OpCo requests approval of this relief request by April 7, 2017, to support the upcoming CPNPP Unit 2 refueling outage.
This communication contains no new licensing basis commitments regarding CPNPP Unit 2.
Should you have any questions, please contact Mr. Jack Hicks at (254) 897-6725 (email:
jack.hicks@luminant.com).
Sincerely, Vistra Operations Company LLC Steff.-s.!f4 Senior Director of Engineering & Regulatory Affairs Enclosure - Request for Relief from Requirements for Limited Examination of Reactor Vessel Head Penetration Welds for Comanche Peak Unit 2, 2B3-1 c-William M. Dean, Director, Office of Nuclear Reactor Regulation Kriss Kennedy, Region IV Margaret M. Watford, NRR Resident Inspectors, Comanche Peak Brandon Kneupper, ANII, Comanche Peak Mr. Robert Free Environmental Monitoring & Emergency Response Manager Texas Department of State Health Services Mail Code 1986 P. 0. Box 149347 Austin TX, 78714-9347
ENCLOSURE TO TXX-17023 Request for Relief from Requirement for Limited Examination of Reactor Vessel Head Penetration Welds for Comanche Peak Unit 2, 2B3-l
Enclosure to TXX-17023 Page 2of10 2/14/17 Request for Relief from Requirement for Limited Examination of Reactor Vessel Head Penetration Welds for Comanche Peak Unit 2, 2B3-1
- 1. ASME Code Component(s) Affected Code Class:
1
Reference:
ASME Code Case N-729-1I10CFR50.55a(g)(6)(ii)(D)
Item Number: B4.20 (UNS N06600 nozzles and UNS N06082 or UNS W86182 partial penetration welds in head)
2. Applicable Code Edition and Addenda
The current Code of record for Comanche Peak Units l and 2 is ASME Boiler and Pressure Vessel Code Section XI, 2007 Edition with 2008 addenda, as augmented by ASME Code Case N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration WeldsSection XI, Division l" (Federal Register 73 FR 52730 September 10, 2008). 1 OCFR50.55a(g)(6)(ii)(D)(6) requires prior NRC approval to implement Appendix I ofN-729-1. Unit 2 ISi Third Interval start date: August 3, 2014, Unit 2 ISi Third Interval end date: August 2, 2024.
3. Applicable Code Requirement
10CFR50.55a(g)(6)(ii)(D)(l) requires that examinations of the reactor vessel head be performed in accordance with ASME Boiler and Pressure Vessel Code Case N-729-1 with the conditions specified in 1 OCFR50.55a(g)(6)(ii)(D)(6)(2) through (6).
For examinations in general (and specifically with reference to limited examinations), N-729 2500 states:
Components shall be examined as specified in Table 1. Volumetric and surface examinations shall be qualified in accordance with the low rigor requirements of Article 14 of Section V1* If obstructions or limitations prevent examination of the volume or surface required by Fig. 2 for one or more nozzles, the analysis procedure of Appendix I shall be used to demonstrate the adequacy of the examination volume or surface for each such nozzle. If Appendix I is used, the evaluation shall be submitted to the regulatory authority having jurisdiction at the plant site.
Figure 2 in N-729-1 (reproduced here as Figure 1) requires that the volumetric examination of nozzle penetrations with an incidence angle less than or equal to 30 degrees has a required coverage length of 1.5 inches. Volumetric examination of nozzle penetrations with an incidence angle greater than 30 degrees has a required coverage length of 1.0 inch.
Enclosure to TXX-17023 Page 3of10 2/14/17 1 The referenced rulemaking changed the volumetric examination qualification requirements.
Only the examination coverage extent is addressed in this request.
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- g I Figure 1: Examination Volume for Nozzle Base Metal and Examination Area for Weld and Nozzle Base Material (from N-729-1) [1]
Table 1 provides the incidence angles of the various nozzles at Comanche Peak Unit 2. The bolded values are the nozzles of interest for this relief request. The other 73 nozzles meet the applicable requirements ofN-729-1. Table 2 summarizes the examination coverage length requirement for the nozzles at Comanche Peak Unit 2. Table 3 provides the dimensions for nozzles 74 through 78 for both the designed and as-built scenarios.
Enclosure to TXX-17023 Page 4of10 2/14/17 Table 1: Comanche Peak Unit 2 head Penetration Nozzles with Intersection Angles Identified (Vent Line Not Included1 21 Nozzle Angle Nozzle Angle Nozzle Angle Nozzle Angle Number (Degrees)
Number (Degrees)
Number (Degrees)
Number (Degrees) 1 0
21 24.8 41 33.9 61 38.6 2
11.4 22 26.2 42 35.1 62 44.3 3
11.4 23 26.2 43 35.1 63 44.3 4
11.4 24 26.2 44 35.1 64 44.3 5
11.4 25 26.2 45 35.1 65 44.3 6
16.2 26 26.2 46 35.1 66 45.4 7
16.2 27 26.2 47 35.1 67 45.4 8
16.2 28 26.2 48 35.1 68 45.4 9
16.2 29 26.2 49 35.1 69 45.4 10 18.2 30 30.2 so 36.3 70 45.4 11 18.2 31 30.2 51 36.3 71 45.4 12 18.2 32 30.2 52 36.3 72 45.4 13 18.2 33 30.2 53 36.3 73 45.4 14 23.3 34 30.2 54 36.3 74 48.7 15
. 23.3 35 30.2 55 36.3 75 48.7 16 23.3 36 30.2 56 38.6 76 48.7 17 23.3 37 30.2 57 38.6 77 48.7 18 24.8 38 33.9 58 38.6 78 48.7 19 24.8 39 33.9 59 38.6 20 24.8 40 33.9 60 38.6 Table 2: Comanche Peak Unit 2 Nozzle Penetrations and Inspection Coverage Requirements from N-729-1 Penetration Incidence Angle Required Coverage Number 0 (De2rees)
"a" (Inches) 1to29
~30 1.5 30 to 78
>30 1.0 Table 3: Penetrations with Alternate Examination Volumes (Less than 1 Inch) (10]
Nozzle Number Weld As-Desirned Weld As-Built 74 1.46" 1.56" 75 1.46" 2.13" 76 1.46" 1.61" 77 1.46" 2.06" 78 1.46" 1.68"
Enclosure to TXX-17023
4. Reason for Request
Page 5of10 2/14/17 During the 2RF08 outage in 2005 [4], 76 of the 78 CROM nozzles were inspected. The coverage limitations for the extent below the weld were addressed in relaxation request TXX-06204 (Accession Number ML063630152) [3] for nozzles 74 through 78. During that inspection, two other nozzles could not be inspected (63 and 65) due to a unique sleeve design that precluded ID inspection at the elevation of the weld due to a centering ring on the sleeve. These two nozzles were inspected during the 2RF09 [5]
outage after temporary removal of the sleeve. Modified sleeves were installed in nozzles 63 and 65 following Ultrasonic (UT) examinations.
During the 2RF12 outage in 2011 [6], 76 of the 78 CROM nozzles were inspected. The coverage limitations for the extent below the weld were addressed in relief request A-2 (Accession Number ML12017A126) [1 O] for nozzles 74 through 78. During that inspection, two other nozzles could not be inspected (63 and 65) due the modified sleeves which precluded access. Nozzles 63 and 65 were inspected during the 2RF13 outage [7]. There were no relevant indications from the CROM Ultrasonic examinations (UT) during 2RF12 or 2RF13. [7] [8]
During 2RF16 the Comanche Peak Reactor Vessel Head Penetration welds for Unit 2 are scheduled to be inspected. It is expected that nozzles 74, 75, 76, 77, and 78 will not meet the minimum coverage provided by N-729-1 [ 1] (of 1.0" for nozzles at an angle greater than 30°) due to geometric limitations. The examination coverage meets the criteria for acceptability as prescribed by Appendix I of N-729-1 [ 1 ], [2].
The data provided in Table 4 is from the previous examination of the nozzles in spring 2005 [9].
Table 4: Penetrations with Alternate Examination Volumes (Less than one inch)
Penetration Nozzle Intersection N-729-1 [1]
Actual Scan 20 ksi Line (Inches Number Angle Required Length below J-groove Inspection Len2th Weld) 74 48.7° 1.0" 0.81" 0.29" 75 48.7° 1.0" 0.30" 0.29" 76 48.7° 1.0"
- 0. 73" 0.29" 77 48.7° 1.0" 0.33" 0.29" 78 48.7° 1.0" 0.36" 0.29" ASME Code Case N-729-1 requires inspection of the penetration nozzle to a distance "a" below the lowest point of the J-groove weld. This exam coverage can be attained by UT, surface examination or a combination of the two. Estimated radiological dose for performing a surface examination of nozzles 74-78 is 500-700 mRem per penetration. This would equate to an estimated range of 2.5-3.5 Rem to inspect the five penetration OD surfaces. Additionally, the OD surface in the region of interest is threaded and the PT results would be of limited value and are likely to result in false positives due to the thread geometry.
Resolution of geometric indications could easily cause a doubling of the personnel exposure.
The coverage reported in the previous reliefrequest is based on the as-built dimensions as determined by ultrasonic measurements from the bottom (toe) of the weld to the lower extent of coverage using the circumferentially oriented tip diffraction (TOFD) probes for detecting axial flaws [8]. The coverage with the axially oriented TOFD probes for detection of circumferential flaws is nominally 0.6" less. For flaw growth calculations below the weld, only axial flaws are of a concern, as documented in WCAP-16397-P
[2]. Eddy current test data was also acquired over this same region on the ID of the penetration. Also, the UT Leak Path (UTLP) was performed on all nozzles to address inspection of the J-weld. Table 5 lists the
Enclosure to TXX-17023 Page 6of10 2/14/17 actual UT and ET coverage along with the calculated required coverage for the region with >20 ksi weld stress.
Table 5: UT Examination Distance below lowest point of the as-built J-groove weld toe.
Penetration Nozzle Weld Intersection Scan Coverage Below 20 ksi Line below Number Angle Weld for Axial Flaws JGroove Weld 74 48.7° 0.81" 0.29" 75 48.7° 0.30" 0.29" 76 48.7° 0.73" 0.29" 77 48.7° 0.33" 0.29" 78 48.7° 0.36" 0.29" (Note: The previous flaw growth calculation was based on a flaw just below the credited inspection volume. With the required UT qualification results, the EPRI Performance Demonstration Qualification Sheet, PDQS-001, specifies a limitation that flaws <0.050U deep were not detected in regions with OD threads, which is the case here.
The earlier flaw analysis did not assume this flaw.)
The flaw growth analysis in WCAP-16397-P [2] is based on the as designed dimensions of the. J groove weld, which assumed a smaller weld throat than the as-built condition. The size of the weld plays an important role in the welding residual stress analysis. Often, the fillet weld on the downhill side of the nozzle is larger than design because of access issues during fabrication. When a weld extends further below the head inside radius due to a larger than design fillet, it does not negatively affect the distance below the weld required for coverage.
Analysis results of larger as-built welds for CRDM nozzles have shown that lesser distance is required below the weld bottom for a transition to below 20 ksi. An assessment was performed on a plant with identical CRDM design and configuration to show that larger welds have a reduced stress profile relative to smaller welds. The cases of 1.46", 2.35", and 2.97" were analyzed to determine their stress profiles.
The 20 ksi criterion is reached in shorter distance for the larger length welds, therefore, the 1.46" design value bounds the as-built dimensions of the CRDM nozzles for the current analysis.
(Note: The WCAP analysis assumed the nozzle was a right cylinder 0.625" thick and did not consider the actual geometry with the relief, threaded section or chamfer. The threaded region has a wall thickness of0.389". The actual geometry will have a small change in the stress.distribution. OD flaws typically have started at the toe of the weld, where the stresses are 3.5-4x the value at the lower extent of the inspected region. So covering some distance below the toe of the weld is sufficient to preclude the existence of cracking. The exception to this only occurred with B&W tubular product material which had cold worked regions along the length of the nozzle, but cracks not connected to the weld toe have not been observed with the material. Alloy 600, used at Comanche Peak.)
Using the RIY equation in N-729-1-2410 (b) [1] reproduced here (and a head temperature of 561°F), the Comanche Peak Unit 2 time period of 2.25 RIY will be reached in 6.2 EFPY of operation.
5. Proposed Alternative and Basis for Use
As an alternative to the volumetric and surface examination coverage requirements shown as dimension "a" in Figure 2 of N-729-1 [ 1) (reproduced here as Figure 1 ), Comanche Peak proposes the use of
Enclosure to TXX-17023 Page 7of10 2/14/17 attainable ultrasonic examination distances shown in Table 3 of this reliefrequest for those head penetrations listed in Table 1. Pursuant to 10CFR50.55a(z)(l) the proposed alternative provides an acceptable level of quality and safety. The required examination coverage dimension for all other penetrations will be met or exceeded.
Appendix I of ASME Boiler and Pressure Vessel Code Case N-729-1 [1] provides an analysis procedure for evaluating an alternative examination area or volume to what is specified in Figure 2 ofN-729-1 if impediments or obstructions prevent the examination of the complete inspection area. 1-1000 ofN-729-1
[1] requires that for eliminating portions of the Figure 2 examination zone below the J-groove weld for alternate inspection zones, the analyses shall be performed using at least the stress analysis method (provided in 1-2000) or the deterministic fracture mechanics analysis method (provided in 1-3000) to demonstrate satisfaction of the applicable criteria. To support this reliefrequest, the techniques of these sections were validated using Westinghouse Report, WCAP-16397-P, [2].
An assumed flaw of0.2 inch below the weld will grow to the bottom of the weld toe after 6.6 EFPY, greater than the 6.2 EFPY that is equivalent to 2.25 RIY at Comanche Peak Unit 2. The assumed flaw is also conservative because the minimum actual inspection coverage is 0.30 inch [8].
5.1 Stress Analysis in Accordance with ASME Code Case N-729-1 Appendix 1-2000 I-2000 of ASME Code Case N-729-1 [l] requires that a plant-specific analysis demonstrate that the hoop and axial stresses remain below 20 ksi (tensile) over the entire N-729-1 examination region (excluding the alternate examination region) as defined by N-729-1, Figure 2. Analyses were performed for the CRDM geometry of a nozzle in an angular position from the reactor vessel centerline at 48.7 degrees. The nozzles bounded by the analysis are provided in Table 6. [8]
T bl 6 C a e :
h P k U "t 2 B d"
N I A I
omanc e ea DI oun me ozz e na1yses Analyzed Penetration Nozzle Penetration Nozzle Numbers Incidence Anele 0 (Deerees)
Bounded by the Analyzed Nozzle 0
1 to 21 26.2 22 to 61 44.3 62 to 65 45.4 66 to 73 48.7 74 to 78 The distance below the J-groove weld that needs to be examined, as determined by the point at which the CRDM penetration hoop stress distribution for the operating stress levels is less than 20 ksi (tension), was analyzed in WCAP-16397-P [2] (in Appendix A).
The stress analysis methodology is provided in Sections 3 and 5 ofWCAP-16397-P.[2]; the summary is provided in Section 7 of WCAP-16397-P [2]. Hoop stresses are provided in Figure 2 of this reliefrequest.
The hoop stress distribution plots in these figures indicate that the minimum achievable inspection coverage below the bottom of the J-groove weld ensures that stresses remain below 20 ksi (tensile) over the entire region outside the alternative examination zone defined by Figure 2 ofN-729-1 [l]. The hoop stresses were used to prepare crack growth prediction to demonstrate that obtaining at least 0.29 inch below the J-groove weld is sufficient to allow for a minimum of 6.2 EFPY (at least four 18-month cycles between examinations).
Enclosure to TXX-17023 Page 8of10 2/14/17 The inspection coverage obtained and the corresponding alternative coverage requested by Comanche Peak Unit 2 is greater than 0.29 inch, as shown in Table 3. The deterministic fracture mechanics analysis is presented in Section 5.2.
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5.2 Deterministic Fracture Mechanics Analysis for Code Case N-729-1 1-3200, Method 1 [1]
In addition to t~e stress analysis detailed above, a fracture mechanics analysis was performed that meets the requirements ofN-729-1 Appendix I, Method 1 ofl-3200 [1] to demonstrate that a potential axial crack in the unexamined zone will not grow to the toe of the J-groove weld prior to the next scheduled examination.
The complete fracture analysis, provided in Sections 3 and 6 of WCAP-16397-P [2], was performed using input from the stress analysis from Section 5 of WCAP-16397-P [2] from the bounding nozzle penetration geometries, and is discussed in Section 5.1 of this reliefrequest. The results of the analysis are shown as a flaw tolerance chart. This chart can be used to determine the minimum required inspection coverage to ensure that any flaws that could initiate below the J-groove weld in the uninspected region will not reach the bottom of the weld before the next inspection. This chart, reproduced as Figure 3, is further discussed and described in WCAP-16397-P [2].
In accordance with Method 1 of 1-3200 [1 ], the crack growth calculations performed to produce the flaw tolerance chart assume that the initial extremity of the through-wall flaw is at or within the bottom edge of 2.5
Enclosure to TXX-17023 Page 9of10 2/14/17 the alternative examination zone. Furthermore, it is assumed that the lower extremity is located on either the inner or outer surface where the hoop stress becomes compressive. The average of the inside and outside hoop stresses was applied along the entire length of the assumed through-wall crack, and the stress intensity factor was calculated using the standard expression for an axial through-wall crack in a cylinder. The crack growth rate determination used in WCAP-16397-P [2] meets the requirements of Appendix 0 of ASME Boiler and Pressure Vessel Code Section XL The resulting flaw tolerance chart demonstrates that a postulated through-wall flaw at the bottom edge of the proposed alternative examination zone wil l not grow to the toe of the J-groove weld within an inspection interval of four refueling cycles. In all cases, the crack growth predictions show greater than 6.2 EFPY of operation required to grow the postulated flaw to the toe of the weld. Additionally, the assumed initial upper extremity locations of axial through-wall flaws are conservative based on a review of the achievable inspection coverage zone in this request (minimum coverage of0.30 inch) because the assumed upper crack extremities are located within the achievable inspection zone.
Examination of portions of the nozzle significantly below the J-groove weld is not pertinent to the phenomena of concern, which includes leakage through the J-groove weld and circumferential cracking in the nozzle above the J-groove weld. In all cases, the measured coverage is adequate to allow Comanche Peak Unit 2 to continue to operate prior to the hypothetical flaws reaching the I-groove weld. Jn accordance with I OCFR50.55a(g)(6)(ii)(D) requirements (1) through (6), the next examination required for these units would be completed prior to flaw propagation into the J-groove welds. The flaw propagation studies are aligned with the examination interval at Comanche Peak Unit 2.
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Figure 3: Crack Growth Prediction for Comanche Peak Units 1 and 2, for Through-wall Longitudinal Flaws (48.7° Penetration Nozzle Downhill Side) [2J
Enclosure to TXX-17023
6. Duration of Proposed Alternative
Page 10of10 2/14/17 The duration of the proposed alternative is for the remainder of the Comanche Peak Unit 2 10-year ISi interval which will end on August 2, 2024.
- 7. Precedent Precedence for relief from the requirements of examination coverage exists because Beaver Valley Unit 2 (ML041950374), San Onofre Unit 2 and 3 (ML040840128), and Indian Point Unit 2 (ML102590213) have all been granted relief for the same issue.
- 8. References
- 1.
ASME Boiler and Pressure Vessel Code Case, N-729-1, "Alternative Examination Requirements for PWR Reactor Vessel Upper Heads With Nozzles Having Pressure-Retaining Partial-Penetration WeldsSection XI, Division l,"March 28, 2006.
- 2.
Westinghouse Report, WCAP-16397-P, Rev. 0, "Structural Integrity Evaluation of Reactor Vessel Upper Head Penetrations to Support Continued Operation: Comanche Peak Units 1 and 2," June 2005. ADAMS Accession Number ML063630186
- 3.
TXU Generation Co. Relaxation Request, TXX-06204 (Accession Number ML063630152),
"Comanche Peak Steam Electric Station (CPSES) Docket Nos. 50-445 and 50-446 Update to 60-Day Response to Revision 1 ofNRC Order EA-03-009, "Issuance of First Revised NRC Order (EA-03-009) Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors"," December 18, 2006.
- 4.
2005 Final Inspection Report, WSJ-PJF-1303011-FSR-001 (2RF08)
- 5.
2006 Final Inspection Report, WDI-PJF-1303310-FSR-001 (2RF09)
- 6.
2011 Final Inspection Report, WDI-1305292-FSR-001 (2RF12)
- 7.
2012 Final Inspection Report WDI-1308102-FSR-001 (2RF13)
- 8.
Westinghouse Report, WPT-17553 "Request for Relief from Requirement for limited Examination of Reactor Vessel Head Penetration Welds" November 2, 2011.
- 9.
TXX-12080 "Response to Request for Additional Information for Relief Request A-2 (TAC NO.
ME7789)".
- 10.
TXX-12002 "Relief Request A-2 for Unit 2 Reactor Vessel Head Penetration Inspections" (ML 12017 Al26)