ML12312A255

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Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for the Repair of Control Rod Drive Housing Penetrations - Response to NRC Request for Additional Information
ML12312A255
Person / Time
Site: Nine Mile Point Constellation icon.png
Issue date: 10/31/2012
From: Swift P
Constellation Energy Nuclear Group, EDF Group, Nine Mile Point
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME5789
Download: ML12312A255 (34)
v • d • e


Text

This letter forwards proprietary information in accordance with 10 CFR 2.390. The balance of this letter may be considered non-proprietary upon removal of Attachment 4.

C ENG .

a joint venture of P.O. Box 63 Lycoming, NY 13093 0 Constflation Energ 'eDf NINE MILE POINT NUCLEAR STATION October 31, 2012 U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTENTION: Document Control Desk

SUBJECT:

Nine Mile Point Nuclear Station Unit No. 1; Docket No. 50-220 Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for the Repair of Control Rod Drive Housing Penetrations - Response to NRC Request for Additional Information (TAC No. ME5789)

REFERENCES:

(a) Letter from J. E. Pacher (NMPNS) to Document Control Desk (NRC), dated March 25, 2011, Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for the Repair of Control Rod Drive Housing Penetrations for the Remainder of the License Renewal Period of Extended Operation (b) Letter from P. M. Swift (NMPNS) to Document Control Desk (NRC), dated September 29, 2011, Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for the Repair of Control Rod Drive Housing Penetrations -

Response to NRC Request for Additional Information (TAC No. ME5789)

(c) Letter from P. M. Swift (NMPNS) to Document Control Desk (NRC), dated April 9, 2012, Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for the Repair of Control Rod Drive Housing Penetrations - Response to NRC Request for Additional Information (TAC No. ME5789)

(d) Letter from B. Vaidya (NRC) to K. Langdon (NMPNS), dated September 13, 2012, Nine Mile Point Nuclear Station, Unit No. 1, Request for Additional Information (RAI) Re: Request No. 1ISI-004, Request to Utilize an Alternative for the Repair of Control Rod Drive Housing Penetrations (TAC No. ME5789)

Nine Mile Point Nuclear Station, LLC (NMPNS) hereby transmits supplemental information requested by the NRC in support of a previously submitted request for alternative (No. 1ISI-004) under the provision of 10 CFR 50.55a(a)(3). This 10 CFR 50.55a request, initially submitted in Reference (a), describes an I This letter forwards proprietary information in accordance with 10 CFR 2.390. The balance of this letter may be considered non-proprietary upon removal of Attachment 4.

Document Control Desk October 31, 2012 Page 2 alternative repair strategy for Nine Mile Point Unit 1 Control Rod Drive (CRD) housing penetrations that includes a variation of the CRD housing penetration welded repair geometry specified in Boiling Water Reactor Vessel and Internals Project (B WRVIP) report BWRVIP-58-A and variations from the requirements of the American Society of Mechanical Engineers (ASME) Code,Section XI, and ASME Code Case N-606-1. NMPNS responded to NRC requests for additional information (RAls) by letters dated September 29, 2011 (Reference b) and April 9, 2012 (Reference c). The supplemental information, provided in Attachment 1 to this letter, responds to the RAI documented in the NRC's letter dated September 13, 2012 (Reference d) that was discussed in a telephone conference call between NRC and NMPNS staff members on September 6, 2012. is considered to contain proprietary information exempt from disclosure pursuant to 10 CFR 2.390. Therefore, on behalf of AREVA NP, Inc. (AREVA), NMPNS hereby makes application to withhold this attachment from public disclosure in accordance with 10 CFR 2.390(b)(1). The affidavit from AREVA detailing the reasons for the request to withhold the proprietary information is provided in . This submittal contains no new regulatory commitments.

Should you have any questions regarding the information in this submittal, please contact John J. Dosa, Director Licensing, at (315) 349-5219.

Very truly yours, Paul M. Swift Manager Engineering Services PMS/DEV Attachments: 1. Nine Mile Point Unit 1 - Response to NRC Request for Additional Information Regarding 10 CFR 50.55a Request Number 1ISI-004

2. AREVA Document No. 32-9157438-000, NMP-1 LAS SCC/SICC Evaluation (Non-Proprietary)
3. Affidavit from AREVA NP Inc. Justifying Withholding Proprietary Information (Document No. 32-9146818-000)
4. AREVA Document No. 32-9146818-000, NMP-1 LAS SCC/SICC Evaluation (Proprietary) cc: Regional Administrator, Region I, NRC Project Manager, NRC Resident Inspector, NRC

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 i

Nine Mile Point Nuclear Station, LLC October 31, 2012

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 By letter dated March 25, 2011, Nine Mile Point Nuclear Station, LLC (NMPNS) submitted 10 CFR 50.55a request number IISI-004 pursuant to 10 CFR 50.55a(a)(3). This 10 CFR 50.55a request describes an alternative repair strategy for Nine Mile Point Unit 1 (NMP1) Control Rod Drive (CRD) housing penetrations that includes a variation of the CRD housing penetration welded repair geometry specified in Boiling Water Reactor Vessel and Internals Project (BWRVIP) report BWRVIP-58-A and variations from the requirements of the American Society of Mechanical Engineers (ASME) Code,Section XI, and ASME Code Case N-606-1. NMPNS responses to NRC requests for additional information (RAIs) were previously provided in letters dated September 29, 2011 and April 9, 2012.

This attachment responds to the RAI documented in the NRC's letter dated September 13, 2012 that was discussed in a telephone conference call between NRC and NMPNS staff members on September 6, 2012.

Each individual NRC request is repeated (in italics), followed by the NMPNS response.

References (from the NRC letterdated September 13, 2012)

1. Nine Mile Point, Unit 1, Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g) for the Repair of Control Rod Drive Housing Penetrationsfor the Remainder of the License Renewal Period of Extended Operation, March 25, 2011 (ADAMS Accession No ML110950307)
2. BWRVIP-58-A: BWR Vessel and Internals Project, CRD Internal Access Weld Repair, EPRI, PaloAlto, CA: 2005,1012618
3. Nine Mile Point, Unit 1, Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g)for the Repair of Control Rod Drive HousingPenetrations- Withdrawal of the Portion of the Request RegardingRotary Peening (TAC No. ME5789) June 7, 2012 (ADAMS Accession No. NIL12160A349)
4. Nine Mile Point Nuclear Station, Unit], 10CFR50.55a Request Number IlSI-004, Revision 1, Attachment 2 to Nine Mile Point, Unit I - Request to Utilize an Alternative to the Requirements of 10 CFR 50.55a(g)for the Repairof ControlRod Drive Housing Penetrations- Response to NRC Follow-up Request for Additional Information, April 9, 2012 (ADAMS Accession No. ML 12102A.112)

RAIA Table 1 to Attachment 2 of the submittal dated March 25, 2011 (Ref 1) notes that abrasive waterjet machining is specified for the severing, weld prep forming and final machining, under the repair methodology approved in [Boiling Water Reactor Vessel and Internals Project Topical Report] B WR VIP-58-A: BWR Vessel and Internals Project,[Control Rod Drive] CRD InternalAccess Weld Repair (Ref 2).

A variationto allow conventional machining,followed by rotarypeening, was requestedfor the Nine Mile Point, Unit I (NMP1) specific repairmethodology. By letter dated June 7, 2012, (Ref 3), the request to perform rotary peening was withdrawn. The variation to use conventional machining versus abrasive waterjet machining was linked to the use of peening. Therefore, the staff requests the licensee to clarify 1 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 which machining technique is planned. If conventional machining is planned, provide a revised justificationfor the variationconsideringthat peening will no longer be performed.

Response

The use of conventional machining is not linked to rotary peening. Conventional machining was qualified independently of rotary peening, was demonstrated in full scale mockups, and will be used for severing, weld prep machining, and final weld crown machining. BWRVIP-58-A does not include a surface remediation step to remove surface tensile stresses. The use of rotary peening was included in the March 25, 2011 submittal as an enhancement to BWRVIP-58-A to include remediation efforts for intergranular stress corrosion cracking (IGSCC) resistance. Therefore, removal of rotary peening is consistent with the previously approved BWRVIP-58-A document in which no remediation step is performed. Additionally, various stress analyses performed in support of the weld repair design conservatively do not take credit for the favorable compressive stresses induced on the ID surface by rotary peening.

Conventional machining is considered an improvement over abrasive waterjet machining as it produces a cleaner machined finish for welding, requires less setup (thereby reducing dose exposure to personnel),

and minimizes risk of damage to the reactor vessel. The conventional machining mill tool to be used for this repair has been designed with several distinct advantages over abrasive waterjet machining, including a camera monitoring system, a mill bit removal system in the case of tool failure, and hard stops to prevent over-machining. Advancements in technology over the last 14 years since the original issuance of BWRVIP-58 in 1998 have resolved the conventional machining issues described in Section 3.2 of BWRVIP-58-A. The conventional machining tools used for the NMP1 repair are of the same design as tools used previously by AREVA on multiple pressurized water reactor (PWR) reactor vessel head control rod drive mechanism (CRDM) penetration weld repairs.

RAIB For Proposed Alternative 2, 48-hour hold, the Basisfor Relief in Section 2B of lISI-004 (Ref. 4) states, "EPRI [Electric Power Research Institute] Report 1013558, Repair and Replacement Applications Center: Temperbead Welding Applications 48-Hour Hold Requirements for Ambient Temperature Temperbead Welding, provides justificationfor starting the 48-hour hold after completion of the third temperbead weld layer rather than waitingfor the weld overlay to cool to ambient temperature." The EPRI report provides information to address issues associated with allowance of a 48-hour hold following completion of the third temperbead weld layer as applied to low alloy steel SA-508, Class 2 reactorvessel (R V) nozzle materials as an alternative to the provisions in Code Case N-638 and N-740.

The reactor vessel bottom head and CRD housingpenetrationmaterialsare not SA-508, Class 2. Provide a technical basis for the applicability of this report to the materials listed in Table 1 of the March 25, 2011 submittal (Ref 1). In addition, whereas the EPRI report discusses American Society of Mechanical Engineers Boiler & Pressure Vessel Code (ASME Code) Code Case N-638 and N-740, the applicable ASME Code requirementfor the CRD bottom head penetrations is Code Case N-606-1. Provide a technical basisfor the applicabilityof this reportto Code CaseN-606-1.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004

Response

SA-508, Class 2 vs. SA-302 Grade B EPRI Report 1013558 provides information to address issues associated with allowance of a 48-hour hold following completion of the third temperbead weld layer as applied to P-No.3 low alloy steels, utilizing examples involving SA-508, Class 2 material. The objective of the EPRI report, stated on page 1-1, is

"...to provide technical justification to allow for the 48-hour hold delay to begin following completion of the third temperbead layer weld layer applied to P-3 low allow steel pressure vessel component," with no mention of the specific grade of material qualified. Code Cases N-638 and N-740 cover temperbead welding and allow starting the 48-hour hold after completing the third tempering layer as applied to P-No.

1, P-No. 3, and P-No. 12A, 12B, and 12C materials, even though the EPRI report only cites examples of SA-508, Class 2 materials.

The NMP1 reactor vessel material (SA-302 Grade B) and the material cited in the EPRI report (SA-508, Class 2) are both P-No. 3, Group Number 3 base materials. The ASME Code,Section IX, QW-420 states, "... [F]errous base metals have been assigned Group Numbers creating subsets of P-Numbers that are used when WPSs [welding procedure specifications] are required to be qualified by impact testing by other Sections or Codes. These assignments are based essentially on comparable base metal characteristics, such as composition, weldability, brazeability, and mechanical properties, where this can logically be done." The 48-hour delay between completion of welding and cooling to ambient temperature and the final non-destructive examination (NDE) of the weld and weld zone is provided so that any delayed cold cracking that may occur will take place prior to the final NDE. The delayed cold cracking mechanisms are identical for all low alloy and carbon steels and are: (a) the presence of diffusible hydrogen; (b) susceptible microstructure; and (c) sustained tensile stress (residual or applied).

Each of these mechanisms is discussed below for the NMP1 reactor vessel SA-302 Grade B material.

(a) Sources for Hydrogen The machine Gas Tungsten-Arc Welding (GTAW) process is inherently a low-hydrogen process.

The GTAW process utilizes dry inert gases that shield the molten weld pool and increase the relative partial pressure between atmospheric elements and the molten weld pool. Furthermore, in the GTAW process, any moisture on the surface of the component being welded is vaporized ahead of the welding. Additionally, austenitic weld materials are being used for the proposed repair as directed by Code Case N-606-1. Austenite has a higher solubility for hydrogen than ferrite, and therefore acts as a sink for any existing diffusible hydrogen. After the third tempering layer, no path exists for additional hydrogen to diffuse into the ferritic base material.

(b) Microstructure Upon welding, a small region of the heat affected zone in SA-302 Grade B material is increased to above the upper transformation temperature. Due to the rapid heating and relatively low ambient temperature of the surrounding base material, cooling rates are high in this area and result in a microstructure of primarily martensite intermixed with small amounts of bainite, pearlite, and ferrite. As subsequent passes are welded, as in the temperbead repair outlined in Code Case N-606-1, the martensite is tempered to a high strength / high toughness microstructure that exceeds the toughness of the unwelded base material as required by ASME Section I1, NB-4335.2 (c)-4. The 3 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 ambient temperature temperbead process used for this repair (as directed by Code Case N-606) is proven to produce high toughness tempered martensite in the procedure qualification (see ASME Section III, NB-4335.2 (c)-4), and is extremely resistant to hydrogen cracking. No microstructure changes occur to the ferritic base material after the third tempering layer.

(c) Tensile Stress and Temperature The proposed repair plan consists of a groove weld joining the reactor vessel material to the roll expanded CRD housing 304 SS material. Since the upper portion of the weld does not tie in to the upper section of the CRD housing, residual stresses are reduced from typical groove weld geometries. Additionally, the EPRI report's discussion on "Tensile Stress and Temperature" includes all P-No. 3 steels (including SA-302 Grade B), and therefore applies to this discussion.

Code Case N-606-1 Applicability Code Case N-606 was written specifically for the purpose of the CRD housing penetration repair being proposed. EPRI Report 1013558 is applicable to Code Case N-606 for the reasons discussed above under the "SA-508, Class 2 vs. SA-302 Grade B" heading. Additionally, the technical aspects of Code Case N-638 (specifically mentioned in EPRI Report 1013558) and Code Case N-606 were identical in Revision 1 of both Code Cases. While Code Case N-638 has been revised to include the revised 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> hold requirement, Code Case N-606 has not been updated with the same frequency as Code Case N-638.

However, since the technical details discussed in Item 1 apply to all P-No. 3 base materials, the technical basis for applying the modified 48-hour hold allowance is equally applicable for a Code Case N-606 repair.

RAIC Section 1 A of IISI-004 (Ref 4) states that "the nondestructive examination (NDE) volumes and areas will be similarto those described in B WR VIP-58-A, as discussedin Attachment 2, "and references Figure 2 [of IISI-004] which depicts the areasfor PT and UT examinations of the modified CRD penetration.

BWRVIP-58-A, consistent with FigureIWB-2500-18 of the ASME Code,Section XI, requires the surface examination area to extend /2 inch beyond the upper and lower weld toe. However, Section JA and the figure do not provide any dimensionsfor the examination area/volumefor the PT or UT examinations.

As such, the staff requests the following information:

1. Clarify the ASME Code required exam volumes/surfaces for ultrasonic testing (UT) and penetrant testing (PT)that apply for the CRD housingpenetration welds at NMP1 by providing a description of the examination volumes and areas that includes dimensions. The description should indicatethe dimensionfrom the weld toe to the end of the examination area/volume.
2. Revise Figure 2 accordingly with the dimensions of these areas/surfacesclearly marked and to ensure that the figure depicts both the requiredexam and the coverage that is achievable.
3. In addition,please clarify the weld extent as shown by Figure 2; it appears that there is a thin layer of weld materialthat extends down from the primary weld area.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004

Response

Item C. 1 The intended examination volumes and surfaces are defined on Figure Cl below. The ultrasonic testing (UT) examination volume will be performed from a-b-c-d-e-f-g-a, and the penetrant testing (PT) examination surface will be performed from a-b-c-d. Though not depicted on Figure C1, the PT procedure requires that the repair weld plus 1/2 inch on both the top and bottom sides of the weld be examined. See Figure C3.

..25 MAX .

Kd

.87 MAX o .063 MIN (410),

s' [ , ,e l , .

. = fb L 1.-.

F Figure C1 5 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 The volumes requiring UT examination, illustrated on Figure C2 below, are:

0 Weld material, S Head low alloy steel base material heat affected zone beneath the weld material, 0 Control Rod Drive (CRD) housing to weld interface, and S CRD housing base material beneath the weld material plus 1/2 inch. (Note: The UT examination procedure requires parent material (axially oriented) plus 1.0 inch minimum.)

Weld material Head low alloy steel base material heat affected zone beneath weld material (Depth below interface - 1/4 in)

Control Rod Drive (CRD) housing to weld interface CRD housing base material beneath the weld material plus 2 in.

1/291 Figure C2 6 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 The surfaces requiring PT examination, illustrated on Figure C3 below, are:

" CRD housing base material 1/2 inch beyond the lower weld toe, and

" RPV and CRD housing base material 1/2 inch beyond the upper weld toe.

1/29 Figure C3 7 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 Item C.2 Required examination volumes and surfaces, including dimensions, are provided in the response to Item C. 1 above. Figure C4 below illustrates the estimated achievable coverage values that were provided in the March 25, 2011 NMPNS submittal, Attachment 2, Table 3.

I

/

d Figure 04 8 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 Item C.3 There is a thin layer of weld material that extends down from the primary weld area, as more clearly depicted on Figure C I above. The UT transducer requires a continuous smooth surface for optimum scan results. Since the potential for "step" transitions between the ground weld / rolled region and the original CRD housing inside diameter (ID) could introduce gaps in, or shift, the scan results, the weld is extended down to cover the roll transition region. The length of the thin layer of weld material varies from 1 to 2.5 inches based on the length of the roll-expanded surface at each bottom head penetration location.

RAID The basisfor reliefin Section 1 B of 1ISI-004 (Ref 4) states that the UT exam is "qualifiedto detectflaws in the new weld and base metal interface beneath the new weld." The basis for relieffor Proposed Alternatives 1 and 3 in Section ]A and 3A of 1ISI-004 (Ref 3), describe the nondestructive examination (NDE) volumes and areas, and the NDE technique,for the proposed UT techniquefor the NMPJ repair, as similar to those specified in BWRVIP-58-A. However, the staff notes that the UT technique described in BWRVIP-58-A was only demonstratedon two stub tube mock-ups with implantedflaws, and of the four fatigue cracks in these mock-ups, three were documented as "not detected" by the UT technique. It is therefore not clear how the results presented in Table 4-3 on page 4.12 of BWRVIP-58-A show that "satisfactoryperformancefor detection of the flaws was accomplished."

Therefore, the staff requests the licensee to clarify and provide details on how the UT technique described in 1ISI-004 has been qualified.

Response

Introduction In the spring of 2009, AREVA completed a project to evaluate and compare the effectiveness of ultrasonic inspection of three component forms:

" Control Rod Drive (CRD) Housing Roll Repair (not relevant to this repair)

This work was performed after the publication date for BWRVIP-58-A, and the results were independent of those published in the BWRVIP-58-A report. The following paragraphs describe the results of that project.

Background

The general weld repair concept developed by EPRI, as described in BWRVIP-58-A, was for the IDTB repair to access the inside surface of the CRD housing and to machine a weld groove in the housing, penetrating into the vessel material below the original stub tube and weld, thus sealing the housing with a new weld. The BWRVIP-58 repair mockups (designated Y1 and Y2) were built to represent this repair 9 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 configuration. An AREVA modification to this approach, as proposed for NMP1, was to install the BWRVIP-58 repair with a gap that "disassociates" the weld from the remaining tube in the reactor bottom head. The modified BWRVIP-58 repair mockups (designated 9087374 and 9087375) were built to represent this configuration. In both of these repairs, the repair weld is the new pressure boundary and provides structural support for fuel related structural components.

1. BWRVIP-58 Repair Mockups (Y1 and Y2)

The mockups were designed to simulate the condition of the BWRVIP-58 IDTB repair containing fabrication type flaws that simulate typical lack of fusion, horizontal dis-bond and cracking. The mockups, built by FlawTech, were composed of flat-bottomed holes, axial and circumferentially oriented fatigue cracks, and lack of fusion flaws (see Figures DI and D2). As shown in Figure D5, these mockups contained an "as-welded" surface finish.

2. Modified BWRVIP-58 Repair Mockups (9087374 and 9087375)

The mockups were designed to simulate the condition of a modified (or "dissociative")

BWRVIP-58 IDTB repair configuration containing fabrication type flaws that simulate typical lack of fusion and dis-bond flaws. The mockups, built by FlawTech, were composed of lack of fusion flaws oriented in both a horizontal and tilted orientation to simulate planar lack of fusion, and horizontal dis-bond (see Figures D3 and D4). As shown in Figure D6, these mockups contained a machined surface finish, which represents the actual surface condition of the proposed NMP 1 weld repair prior to performance of final NDE.

Ultrasonic Examination Technique The conventional ultrasonic examination required the use of several search unit beam angles and scanning directions as shown below. The transducers selected for the IDTB repairs (both BWRVIP-58 and modified BWRVIP-58 configurations) are those used successfully in the repair of PWR reactor vessel closure head (RVCH) penetrations, as follows:

0 00 search unit, used for weld profiling and detection.

  • 450 refracted longitudinal (RL) search unit, scanned axially "up" and "down," used for detection of flaws parallel to the weld.
  • 70' RL search unit, scanned axially "up" and "down," used for detection of flaws parallel to the weld.
  • 450 RL search units, clockwise and counterclockwise, used for detection of flaws perpendicular to the weld.

The results from the UT examinations of all mockup standards are presented in Table Dl. This table lists the detection results for each flaw and for each method in all mockups inspected. The results shown in Table DI are colored coded according to estimated signal-to-noise ratio (SN) for each indication. The SN was determined by the ratio of the maximum peak of the reflector and the surrounding material noise in the immediate volume around the reflector. Each flaw-related signal was analyzed to determine SN in order to provide a basic understanding of the ease at which the reflector was detected. An SN of eight (8) or greater (indicated by the color green in Table DI) signifies indications that are typically very easy to detect in the ultrasonic images. In contrast, indications with an SN of 4 or less (indicated by the color 10 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 yellow in Table Dl) are much more difficult to differentiate from surrounding geometric reflectors or material/system noise. The last column in Table Dl indicates a final detectability determination.

In addition to the data provided in Table D1, the proposed CRD housing penetration IDTB repair weld is subject to ASME Inspection and Repair/Replacement Plan criteria. The inspection requirements of ASME Code Cases N-606-1 and N-638-1, as modified by Regulatory Guide (RG) 1.147, are applicable to this weld repair. Code Cases N-606-1 and N-638-1 state that the weld shall be examined in accordance with Section XI, Appendix I. RG 1.147, Revision 15 (in effect at the time of the March 25, 2011 submittal of the request for alternative) identifies both Code Cases N-606-1 and N-638-1 as "conditionally acceptable." While the condition associated with Code Case N-606-1 is not NDE related, the condition associated with Code Case N-638-1 is specific to NDE and is as follows:

"UT volumetric examinations shall be performed with personnel and procedures qualified for the repaired volume and qualified by demonstration using representative samples which contain construction type flaws. The acceptance criteria of NB-5330 in the 1998 Edition through 2000 Addenda of Section III (Ref. 7) apply to all flaws identified within the repaired volume."

The acceptance criteria stated in ASME Section III, NB-5330, are as follows:

All Imperfections which produce a response greater than 20% of the reference level shall be investigated to the extent that the operator can determine the shape, identity, and location of all such imperfections and evaluate them in terms of the acceptance standards given in (a) and (b) below.

(a) Imperfections are unacceptable if the indications exceed the reference level amplitude and have lengths exceeding:

(1) 1/4 in. (6 mm) for t up to 34 in. (19 mm), inclusive.

[Items (2) and (3) are beyond the applicable thickness range for the NMP1 repair]

where t is the thickness of the weld being examined; if a weld joins two members having different thicknesses at the weld, t is the thinner of these two thicknesses.

(b) Indications characterized as cracks, lack of fusion, or incomplete penetrations are unacceptable regardless of length.

Table D2 provides the analysis results for the UT examinations performed on both the BWRVIP-58 and modified BWRVIP-58 IDTB repair mockups. The UT procedure met the ASME Code requirements for IDTB repair examination. With the exception of flaws A, B, C, K, M, and N (all within the Y1 and Y2 mockups), all IDTB implanted fabrication defects were detected at levels that exceed the recording criteria as specified in the ASME Code. These results are further discussed below.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 BWRVIP-58 Repair Mockups (Y1 and Y2) UT Examination Results All circumferential flaws in the Y2 mockup, with the exception of Flaw C, were detected by the UT technique. Flaw C was a circumferential reflector with the smallest through-wall dimension. A phased array probe was used to see if a specific angle could be used to detect Flaw C. Closer examination indicated that the phased array technique required a 350 longitudinal wave to detect this reflector. It is likely that this flaw was missed since the conventional probes did not produce a longitudinal wave at this optimum angle. Also missed were all axial flaws contained in this block (Flaw A and Flaw B). The missed conventional technique detections of Flaws A, B, and C are consistent with past project detection results. Although it is possible these flaws were missed due to the highly attenuative weld material, it is not probable this was the case. Visual examination of the ID surface indicated that the weld was left in an as-welded condition on both the Y1 and Y2 mockups. Figure D5 is a photograph of this surface.

Detection of axial flaws required scanning on the weld ID surface. An as-welded surface like that shown creates problems for ultrasonic inspection since it tends to scatter the sound entering the component as well as partially decouple the probe through the introduction of excessive water gaps under the wedge.

Detection of small flaws with the probe coupled to this surface is difficult and the most probable cause for missed detections. The test results for mockup Y1 supported this hypothesis. Only two flaws were detected in this mockup. Flaw N is a 0.25 inch diameter flat bottomed hole and Flaw L is a 0.094 inch diameter flat bottom hole. These flaws are actually the largest and smallest flat bottom holes in the Y1 sample set. The remaining reflectors fell within this range but were not detected. It was clear that the surface roughness prevented detections in the weld region.

The results described above for the 2009 AREVA evaluation project were similar to the results reported in BWRVIP-58-A, in that three of the four fatigue cracks in the EPRI stub tube mockups were documented as "not detected" in BWRVIP-58-A. The results differed in the detection results for the flat bottom holes, in that BWRVIP-58-A reported that all four reflectors were detected whereas the 2009 AREVA evaluation project detected only two.

Modified BWRVIP-58 Repair Mockups (9087374 and 9087375) UT Examination Results The modified BWRVIP-58 repair mockups contained welds with a smooth machined ID surface along with a groove machined adjacent to the weld, as shown in Figure D6. The presence of the groove limited the amount of surface available for inspection when inspecting with the beam directed down the tube (or away from the groove). Unlike the BWRVIP-58 repair mockups (Y1 and Y2), the modified repair mockups had machined ID surfaces that did not present coupling problems when inspecting over the top of the weld. The conventional probes were capable of detecting all flaws, both axial and circumferential, with good signal-to-noise ratios.

Conclusion The results from the 2009 AREVA evaluation project have demonstrated that the proposed UT techniques for post-weld examination of the NMPl CRD housing penetration modified BWRVIP-58 IDTB weld repair have adequate sensitivity to detect unacceptable flaws when the weld ID has a smooth surface. The procedures utilized to accomplish the NMP1 weld repair assure that a smooth ID surface will be attained prior to performing the post-weld UT examination.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER IISI-004 Table D1 - Detection Summary for All Flaws (Signal to Noise Ratio) 13 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER IISI-004 Not Not Detected Not Detected K

Y1L M Not Detected Not Detected N Not Detected Not Detected A Not Detected Not Detected Not Detected B Not Detected Not Detected Not Detected CNot Detected Not Detected Not Detected BWRVIP2D Not Detected FNot Detected Not Detected Not Detected H Nt Dteced Not Detected Not Detected ModifiediP5 2 9087374 4*

6 Blank space indicates that a detection is not expected for a specific flaw with the given transducer.

"Not Detected" indicates that a detection is expected for a specific flaw with the given transducer.

Table D2 - Detection Result Summary for IDTB Weld Repairs in Accordance with ASME Recording Criteria for Conventional Transducers 14 of 31

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 FLAW A A C D F G~ H c 45 W 135* 1 MA 2 its-4 FLAWd'E' FT 7 FLAWd F LAW C'D XHgo.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 Figure D3 - Modified B1RVIP-58 Repair Mockup 9087374 17 of 31

ATTACHMENT 1 NINE MILLE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 Figure D4 - Modified BWRVIP-58 Repair Mockup 9087375 18 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 Figure D5 - BWRVIP -58 Repair Mockup (Y1 and Y2) Showing "As-Welded" ID Surface Condition Figure D6 - Modified BWRVIP-58 Repair Mockup (9087374 and 9087375) Showing Machined ID Surface Condition 19 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 RAI E Request No. 1ISI-004 (Ref 4) states that UT exam acceptance criteriaare in accordance with NB-5331 as modified by BWRVIP-58-A. Please explicitly explain how the acceptance criteria are modified by BWRVIP-58-A. Providejustificationfor any modifications to the acceptance criteria.

Response

BWRVIP-58-A modifies the acceptance criteria by excluding the triple point anomaly from the requirements of NB-5331. As noted in the response to RAI D, NB-5331 defines the following as unacceptable: (1) any indications whose amplitude is greater than the reference level for a length greater than 1/4 inch; and (2) indications characterized as cracks, lack of fusion, or incomplete penetrations regardless of length.

Due to a combination of factors, the triple point region of the CRD penetration housing repair configuration is not likely to contain a 360 degree anomaly. This anomaly is analyzed independently and is considered benign when sized at less than 0.1 inch in the through-thickness direction. It is assumed for analytical conservatism that a 0.1 inch indication could exist in the through-thickness direction of the nozzle even though indications of this size have not been observed. The analysis of this 0.1 inch triple point anomaly is conservative as the indication is analytically treated as a flaw. The environment to which the triple point anomaly is exposed is benign and does not include exposure to the primary coolant; therefore, the time dependent crack growth rates for IGSCC are not applicable regardless of residual stresses. Additionally, weld mockup testing has shown that the residual stress fields are not sufficient to promote ductile tearing. Furthermore, the weld material is crack tolerant when exposed to a benign environment and has proven to be resistant to fatigue growth and net section failure by Section XI analysis.

See the response to RAI F for details concerning the UT examination of the triple point anomaly. All other detected indications will be subject to the requirements of NB-5331 without modification.

RAIF Provide details of how it was determined that the UT is able to detect and size the triple point anomaly such that, should a rejectable anomaly be present (>0.1 "), the UT would be able to detect and size it appropriately.

Response

The creation of a welding anomaly is common to both the BWRVIP-58 and modified BWRVIP-58 IDTB repairs. The introduction of a weld in the CRD stub tube creates a "triple point" where three different materials are joined; the weld material (Alloy 309), stainless steel CRD tube material, and carbon steel (CS) vessel material. A mockup was developed with artificial flaws that simulate weld solidification anomalies like that shown in Figure Fl. The Triple Point mockup (3794-01) represents this condition.

The Triple Point mockup was constructed to simulate the typical signal responses for triple point solidification anomalies. The mockup, built by Sonospection, is composed of the CRD housing (304SS),

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 IDTB weld (ERNiCr-3), and lower reactor vessel head (CS). The basic mockup form represents the modified BWRVIP-58 IDTB repair. The reflectors used to simulate the triple point anomaly are a series of EDM notches with differing depths that have been squeezed shut via hot isostatic pressing (HIP).

Details of this mockup are provided in Figure F2.

UT Examination Results All flaws in this mockup were detected using one or more of the conventional probes scanned. The results from the UT examinations of the Triple Point mockup block are presented in Table Fl. This table lists the detection results for each flaw and for each method. The results shown in Table F1 are color coded according to estimated SN for each indication. The SN was determined by the ratio of the maximum peak of the reflector and the surrounding material noise in the immediate volume around the reflector. Each flaw related signal was analyzed to determine SN in order to provide a basic understanding of the ease at which the reflector was detected. An SN of eight (8) or greater (indicated by the color green in Table Fl) signifies indications that are typically very easy to detect in the ultrasonic images. In contrast, indications with an SN of 4 or less (indicated by the color yellow in Table Fl) are much more difficult to differentiate from surrounding geometric reflectors or material/system noise. The last column in Table F1 indicates the final detectability determination.

The results indicated that both the 45° and 70' longitudinal wave probes performed well with beam directions directed axially up the sample toward the weld, with the 70L lP exhibiting superior performance. Flaw A was not detected using the 45' L-wave probe in either direction. Table F2 provides the sizing results (length and depth) from the Triple Point mockup. The sizing results are used to define the accuracy of the technique for UT uncertainty values to be considered during the analytical acceptance evaluation for any detected (i.e., reported) triple point anomaly.

The tests also indicated the capability of the 0' L-wave probe to detect solidification flaws found in the triple point region. Since the 0' L-wave propagated in a direction parallel to the EDM flaw plane, all signals were tip diffracted signals originating from the EDM notch tips. Since all notches were oriented vertically in this block, no reflected energy off the flaw face was possible. All notch signals were weak, as would be expected for tip diffracted signals, but discernable. However, all flaws except for Flaw J were detected using the 0' L-wave probe. Flaw J was the deepest notch present with the notch tip approximately 0.057 inch below the ID surface. Having such a shallow depth placed this flaw outside the zone for detection for this transducer. This test did demonstrate good detection abilities for this probe in the triple point region.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 Table FL - Detection Summary for All Flaws (Signal to Noise Ratio) - Triple Point Mockup 22 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER IISI-004 DELTAS Raw CONVENTIONAL SIZING CONVENTIONAL SIZING Flaw Flaw Flaw Depth Flaw Flaw Width Flaw Depth Flaw Width Flaw Depth Mock ID Number Type Orion. (Triple Point) Width (inch) (inch) (inch) (inch)

Raw A HFIEDM arc. 0.050 0.500 0.391 0.053 -0.109 0.003 Flaw B HI-FB)V arc. 0.110 0.500 0.459 0.108 -0.041 -0.002 Raw C I-IP-EM arc. 0.075 0.500 0.387 0.077 -0.113 0.002 Raw D HFIEDM Orc. 0.200 0.500 0.519 0.341 0.019 0.141 Triple Point Flaw E HFIE)M arc. 0.080 0.500 0.541 0.065 0.041 -0.015 Mockup Raw F HP-)EM arc. 0.400 0.500 0.344 0.464 -0.156 0.064 (3794-01) Raw G IP-)EDM arc. 0.095 0.500 0.461 0.102 -0.039 0.007 Raw H HF-II)EM arc. 0.450 0.500 0.472 0.525 -0.028 0.075 Raw I HP-EDM arc. 0.349 0.500 0.280 0.378 -0.220 0.029 Flaw J HI-EDM arc. 0.500 0.500 0.397 0.292 -0.103 -0.208 Raw K I-F-EDM arc. 0.300 0.500 0.571 0.347 0.071 0.047 LL--I I'ULM.

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0.088 0.086 Table F2 - Length and Depth Sizing Results - Triple Point Mockup 23 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 Figure Fl - Typical Weld Solidification Anomaly Formed Where the Carbon Steel, Weld, and Tube Materials Meet; i.e., the "Triple Point" 24 of 31

ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 RAIG ASME Code,Section III acceptance criteriarequire discriminationofflaw type such that cracks, lack of fusion (LOF), and incomplete penetration (ICP) > 20% distance amplitude curve (DAC) are rejected.

How isflaw type determinedby the UT proceduresuch that this criterionmay be applied?

Response

The analysis section of the UT procedure provides guidance (via procedural steps) to the data analyst based on reflector features (i.e., echo-dynamic profiles, depth location, position with respect to weld, etc.)

for flaw classification. Guidance from the procedure includes the following:

General

  • Flaw indications usually exhibit themselves as localized areas of target motion (at least 3 consecutive scan lines) and peak amplitudes greater than background noise levels.
  • Cracks are typically surface connected and may appear as isolated indications or multiple related indications within the examination region.

" Lack of fusion flaws are planar flaws occurring in the weld or along the fusion line of the weld and do not exist in the base metal.

  • Inclusions are a welding imperfection located in the weld volume.

Specific

" When performing single sided examinations, ultrasonic data from all search units shall be evaluated.

" If data from two or more of the search units confirm the non-geometric indication, it should be considered a flaw if the location of the indication cannot be correlated with geometric features of the component.

  • The beam plot extends beyond the design crevice transition area and a scan looking in the opposite direction also detects the same reflector at the same location.
  • The same angle detects and plots the reflector in the same location but from the opposite direction.
  • A different angle detects and plots the reflector in the same location from the opposite direction.
  • A circumferential scan detects a reflector determined to be an axial component in an area adjacent to a suspect circumferential indication.
  • There may be evidence of flaw tip signals as displayed in the B-scan image.
  • A shear wave response may be present along with the longitudinal wave response of the suspected flaw image.

" There may be indications that occur at or near the ID surface with coherent target motion. This signal is typically observed with the shear wave signal.

  • Flaws that are surface connected may appear as isolated indications or multiple related indications within the examination region. Near surface initiated flaw indications will usually exhibit target motion that extends through the inside surface of the component if the movement of the transducer is not compromised by geometric conditions. When a flaw indication is coincident with a high amplitude surface geometric response the target motion of the flaw response will normally extend through the geometric response.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 Since the procedure requires that analysis of reflector features defines characterization of flaws, data analysis personnel are certified to Level II or Level III in the UT method in accordance with AREVA or an approved contractor's written practice, and have received training in the UltraVision automated UT application. A valid EPRI Personnel Demonstration Qualification Summary (PDQS) for an automated UT procedure using TomoView or UltraVision may be used in lieu of this training. In this use, the PDQS indicates successful completion of the requirements set forth in EPRI report 1019478, "Nondestructive Evaluation: Program Description for Performance Demonstration of Pressurized Water Reactor Upper Head Penetration Examination," latest revision. The intent of the PDQS is to show demonstrated competence with the analysis display program.

RAI H At least two vendors in the United States have performance demonstration initiative (PDI)qualified UT techniquesfor inspecting upper head control rod drive mechanism (CRDM) nozzles in pressurizedwater reactors (PWRs). As noted in Table 1 on page 7 of 13 of Attachment 2 to the March 25, 2011 submittal (Ref 1), "The CRDM nozzle penetration repair configuration is very similar to the dissociated configurationfor NMP1; therefore the same beam angles will be used. " In addition to using the same beam angles, will the personnel, procedures, and equipment used for the qualified PWR upper head exams be usedfor NMP1 CRD housings repairs?

Response

The procedures and equipment for performing the UT examinations will be the same as those used in PWR inner diameter temper bead (IDTB) upper head examinations (as of October 2012). Approximately 70% of the AREVA NDE analysis staff who are eligible for deployment possess the PWR upper head CRDM PDQS. Though not required for this examination, the examination personnel involved with the NMP1 CRD housing repair will possess the PWR upper head CRDM PDQS or an equivalent BWR bottom head PDQS, should one become available in the future.

RAIl As noted in Table 1 on page 8 of 13 of Attachment 2 to the March 25, 2011 submittal (Ref 1), UT examination at the end of the defined inservice inspection (ISI) interval will confirm acceptancefor the subsequent interval. However, IS1 NDE qualifications were not addressed in this relief request or BWRVIP-58A. Pleaseprovide a detaileddescription of the UT that will be usedfor ISI.

Response

The UT examination used for inservice inspection will be equivalent to the technique used for the preservice inspections to be performed following completion of the weld repair. The inservice inspection NDE qualification process will be in accordance with the ASME Code,Section V, Article 14, for an Intermediate Rigor (Limited Performance Demonstration) level of qualification rigor. This is consistent with the inspection philosophy for PWR upper head CRDM IDTB repairs (prior to the incorporation of ASME Code Case N-729-1, as modified by 10 CFR 50.55a).

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 RAIJ In Item 4 of Table 1 of Attachment 2 to the March 25, 2011 submittal (Ref 1), as part of the justification for the reduced UT coverage of the modified weld configuration, an evaluation of a postulatedflaw in the area of reduced UT coverage is referenced (Reference 18 to Attachment 2 of the March 25, 2011 submittal). Provide Reference 18 to Attachment 2 to the March 25, 2011 submittal (Ref 1) for staff review.

Response

Reference 18 cited in Attachment 2 to the March 25, 2011 submittal is AREVA Document No. 32-9146818-000, "NMP-1 LAS SCC/SICC Evaluation." A copy of this document is provided in Attachment 2 (non-proprietary) and Attachment 4 (proprietary). The affidavit from AREVA detailing the reasons for the request to withhold proprietary information is provided in Attachment 3.

The purpose of the low alloy steel (LAS) stress corrosion cracking (SCC) evaluation is to provide a conservative estimation of the IDTB repair life. According to BWRVIP-60-A, "The results of this study reveal that low alloy steel RPVs are extremely tolerant to postulated SCC cracks emanating from attachment welds or weld metal cladding. The field and laboratory data illustrate that crack initiation and growth is extremely difficult and that no SCC induced damage has been observed in BWR vessel components. All cracking observed has been in cladding and most of the cracking was the result of a manufacturing or fabrication defect. Even when limited environmentally assisted corrosion has been observed in vessel cladding, it has arrested at the vessel-clad interface. This result indicates that the consideration of possible SCC growth into the LAS is, in fact, conservative."

Although the initiation and propagation of SCC cracks in the LAS is not likely to occur, the analysis assumed that a 0.1 in flaw forms due to the IDTB welding process. The most probable propagation path for such a flaw is in the heat affected zone (HAZ) region due to high residual stresses from welding.

Potential flaw propagation paths in other directions emanating from the same point are less likely based on the findings of BWRVIP-60-A and are not a concern for the integrity of the weld repair.

In addition, NMPNS has previously performed an evaluation of a postulated flaw in the Alloy 182 stub tube-to-reactor vessel weld that included consideration of the flaw penetrating into the reactor vessel base metal (reference NMPNS letter to the NRC dated May 14, 2009 - ADAMS Accession No. ML091410447). The evaluation concluded that, even if cracking were to continue into the vessel, the postulated flaw does not pose any structural concerns for the reactor vessel. The NRC agreed with this conclusion in their letter to NMPNS dated August 3, 2009 (ADAMS Accession No. ML091980454).

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 The following questions are related to AREVA Document No. 32-9138065-002, "NMP1 CRD Housing IDTB Weld Anomaly Analysis" (Proprietary), (ADAMS Accession No. ML110950319), hereafter referred to as "theflaw evaluation." References to the ASME Code,Section XI, are to the 2004 Edition, No Addenda.

RAI K Table 4-2 of the flaw evaluation lists the load combinations and cycles used to calculatefatigue crack growth for the postulatedflaws. Tables 5-2, 5-5, and 5-7 through 5-10 show the contributionsof these transients to fatigue crack growth various postulatedflaw types and propagationpaths. However, for the end-of-life stability evaluations of the three flaw types postulated (continuous external circumferentialflaw and external axialflaw in the repairweld. cylindricalflaw in repairweld or low-alloy steel), it is not clear which of these loads were considered and which loads were considered limiting. Two AREVA internal documents, References 5 and 7 to the flaw evaluation are referenced as the source of the transientsconsidered.It is not clear how these transientswere derivedfrom the NMP1 design basis.

For the evaluations of the circumferentialand axialflaws in the weld metal summarized in Table 5-3 and 5-6, only the safety factorfor Service Level A (normaloperating)conditions is given, implying that only Service Level A conditions were considered,or were determined to be limiting.

For the cylindricalflaws, the margins for normal, upset, faulted and emergency conditions were calculated in accordance with the ASME Code,Section XI, IWB-3612. However, it is not clear which transientconditions and loadings were used to determine the appliedstress intensityfactors (K)for these evaluations.

The staff therefore requests the following information:

1. Explain which transientsand load combinations were usedfor the end-of-life evaluationfor each type offlaw, and how these transientsand load combinations were determinedto be limiting.
2. Identify which Service Levels the limiting loads provided in the response to item 1 represent. If the end-of-life flaw stability evaluation did not consider each Service Level (A, B, C, and D),

justify why only certain service level conditions were considered.

3. Identify the source in the NMP1 design basisfor the transientsand loading combinations used to determine fatigue crack growth and to evaluate end-of-life flaw stability. Describe how the transients listed were derivedfrom the plantdesign basis.

Response

Items K.1 and K.2 For the evaluations of the circumferential and axial flaws in the weld metal summarized in Tables 5-3 and 5-6, the applicable loads for the flaw evaluations are due to pressure only for the axial flaw case and due to pressure and external piping loads for the circumferential flaw case.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 11SI-004 For the circumferential flaw, the analysis shown in Table 5-3 uses the highest pressure of all the transients identified as applicable for the flaw evaluation, as reported in References 5, 6, and 7. Also, the external axial loads considered are due to dead weight (DW), stuck control rod load, and seismic. Per References 5 and 6, the axial loads considered are actually Service Level B. The analysis considered the safety factor for Service Level A, which is the highest safety factor, to ensure that the most conservative flaw evaluation margins are obtained.

For the axial flaw case, the analysis shown in Table 5-6 uses the highest pressure of all the transients identified as applicable for the flaw evaluation, as reported in References 5, 6, and 7. Again, the safety factor for Service Level A (normal operating) conditions was used to ensure that the most conservative results were obtained.

For the cylindrical flaws, the margins for normal, upset, faulted and emergency conditions were calculated in accordance with the ASME Code,Section XI, IWB-3612. The stress intensity factors were calculated for every time point for all the transients reported in Reference 6. Reference 6 provides thermal and pressure stresses along the path lines for the cylindrical flaw at every time point. A summary of the maximum and minimum stress intensity factors for cylindrical flaw is reported in Tables 5-7, 5-8, 5-9, and 5-10. The controlling time points (when the minimum and maximum stress intensity factors occur) are tracked during the calculation. At the final flaw length for each path line, the linear elastic fracture mechanics (LEFM) margin is estimated based on the final flaw size and the most limiting temperature and transient stresses. The limiting margins are summarized in Table 5-12. Column 2 of Table 5-12 shows the limiting transient for each case. The limiting transient is based on the maximum applied stress intensity factor and fracture toughness, which is dependent on temperature.

Item K.3 The NMP1 reactor vessel design transients and CRD water temperature variations presented in the original General Electric (GE) cycle loading diagram for the NMP1 reactor vessel were used as the primary basis for the analysis design transients. In addition, previous NMP1 vessel, CRD penetration, and nozzle stress analyses were reviewed to determine if the thermal transients used in those analyses are more conservative than those in the GE cycle loading diagram. Additionally, BWRVIP-55-A, "BWR Vessel and Internals Project Lower Plenum Repair Design Criteria," was used as guidance. The final design transients used in the analyses presented in AREVA document 32-9138065-002 conservatively envelope the design transients presented in the GE cycle loading diagram, those used in previous stress analyses, and the BWRVIP-55-A recommended guidance.

RAIL For the normal startup and shutdown transients, the number of occurrences listed in Table 4-2 differs from the number of occurrences of these transients listed in Table V-2 of the Nine Mile Point, Unit 1 (NMP1) Updated FinalSafety Analysis Report (UFSAR). Explain this discrepancy.

Response

The use of 119 cycles for the Normal Shutdown (100°F/hr Cooldown) transient and 120 cycles for the Normal Startup (100°F/hr Heatup) transient are adequate for the calculation's stated 40-year design life.

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ATTACHMENT 1 NINE MILE POINT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION REGARDING 10 CFR 50.55a REQUEST NUMBER 1ISI-004 These numbers of cycles were based on the original number of cycles for a 40-year plant life that were specified in the original GE cycle loading diagram for the NMP1 reactor vessel. Since the weld repair is not yet installed and the remaining plant design life is less than 40 years, the number of cycles is conservative relative to the remaining years of plant operation. This conclusion is based on a projection of the actual number of normal startups and shutdowns that may occur over a 40-year period (by considering the past 10 years of operating history), which indicates that the expected number of cycles will be well below the number of cycles used in the calculation.

RAIM Clarify whether the end-of-life evaluationsfor the continuous external circumferentialflaw and external axial flaw, summarized in Tables 5-3 and 5-6 and described as "limit load" analyses, should be characterized as "Elastic-PlasticFracture Mechanics (EPFM)" evaluations since the procedures of Article C-6000 of the ASME Code,Section XI were usedfor these evaluations.

Response

It is understood that the titles of Tables 5-3 and 5-6 use the term "limit load," which is misleading since an elastic-plastic fracture mechanics (EPFM) analysis was actually performed. Based on Figure C-4210-1 of Article C-4210 of Section XI of the ASME Code, the appropriate flaw evaluation procedure for nonflux welds is provided in Article C-5000 of the ASME Code, which is based on limit load analysis; however, the analysis used the flaw evaluation procedure of Article C-6000 instead, which is appropriate for flux welds. The flaw evaluation in Article C-6000 is based on the limit load analysis (in Article C-5000) with an additional application of the Z-factor multiplier. The Z-factor, which is estimated based on EPFM concepts, is a load multiplier applied to the limit load analysis to account for ductile crack extension. The use of the Z-factor from Article C-6000 results in a more conservative flaw evaluation.

RAIN Figure C-4210 of the ASME Code,Section X, Appendix C, "Flowchartfor Selecting Analysis Method for Austenitic Piping," indicatesfor a weld metal flaw in a nonflux weld, the procedures of C-5000 should be used. Therefore, the staff requests that the licensee explain why the procedures of C-6000 were usedfor the evaluations of the continuous external circumferentialflawand external axialflaw in the repairweld, since the gas-tungsten arc welding (GTA W9 process usedfor the repairweld does not involve flux.

Response

It is acknowledged that the gas-tungsten arc welding (GTAW) process does not involve flux and does not require the Z-factor (per Article C-6000) to be considered in the flaw evaluation. Nonetheless, the flaw evaluation has included the Z-factor, which results in a more conservative evaluation. See also the response to RAI M.

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