ML041610373

Requesting Use of an Alternative to ASME Code Section XI for Installation of Mechanical Nozzle Seal Assemblies on Pressurizer Heater Penetration Nozzles

ML041610373
Person / Time
Site:	Millstone
Issue date:	06/03/2004
From:	Hartz L Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
04-140, NL&OS/PRW, Rev 3 RR-89-35, Rev. 1
Download: ML041610373 (20)

Text

Dominion Nuclear Connecticut, Inc. J D minion Millstone Power Station D ominion Rope Ferry Road Waterford, CT 06385 June 3, 2004 U. S. Nuclear Regulatory Commission Serial No.: 04-140 Attention: Document Control Desk NL&OS/PRW Rev 3 Washington, DC 20555 Docket No.: 50-336 License No.: DPR-65 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

MILLSTONE POWER STATION UNIT 2 REQUEST RR-89-35, REV. 1, USE OF AN ALTERNATIVE TO ASME CODE SECTION Xi FOR INSTALLATION OF MECHANICAL NOZZLE SEAL ASSEMBLIES (MNSAS) ON PRESSURIZER HEATER PENETRATION NOZZLES Pursuant to the provisions of 10 CFR 50.55a(a)(3)(i), Dominion Nuclear Connecticut, Inc.

(DNC) requests U.S. Nuclear Regulatory Commission (NRC) approval for the use of Mechanical Nozzle Seal Assemblies (MNSAs) in the repair of degraded Reactor Coolant System (RCS) pressurizer heater penetration nozzles as documented in Attachment 1.

Specifically, DNC proposes the following alternative regarding the use of MNSAs on pressurizer heater sleeves and nozzles:

As an alternative to removing previously installed MNSAs and performing welded repairs, DNC requests NRC authorization to use previously installed MNSAs as permanent repairs.

Installation of MNSAs is an alternative to certain requirements of Section Xl of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) that have been demonstrated by industry experience to provide an acceptable level of quality and safety for restoring structural integrity and leak tightness to the RCS.

Currently, DNC has four MNSA Type is (MNSA-1s) installed on four degraded pressurizer heater penetration nozzles at MPS2. Two of these MNSA-1s were installed in the Spring 2002 refueling outage and two were installed in the Fall 2003 refueling outage.

DNC requested and was granted temporary Code relief (i.e., RR-89-35 and RR-89-43) in support of these MNSA-1s installations. In each case the Code relief was limited to no more than two cycles of operation from the initial installation date. The temporary approval for the two MNSA-1 s installed at MPS2 in 2002 will expire at the end of the next refueling outage scheduled for the spring of 2005. The temporary approval for the remaining two MNSA-1s installed in 2003 will expire at the end of the refueling outage scheduled for Fall 2006. DNC is requesting approval of the two MNSA-1s installed in 2002 at MPS2 as acceptable repairs beyond the period for which temporary approval was previously granted based on the justification contained in Attachment 1. The inservice inspection program for the MNSA-1s is described in Attachment 1. Authorizations currently limit the use of the MNSA-1s to two operating cycles. Therefore, a request is needed to address the two MNSA-1s currently installed at MPS2 for use beyond the period for which temporary approval has already been granted. DNC is intending to replace the MPS2 pressurizer in the Fall 2006 refueling outage which will eliminate the

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Serial No.04-140 Relief Request RR-89-35, Rev. 1 Page 2 continued need for the installed MNSA-1 s. The replacement of the pressurizer is part of a long-term plan to mitigate concerns with primary water stress corrosion cracking (PWSCC) of Alloy 600 and the associated weld metals 82 and 182 at MPS2.

DNC requests review and approval by March 1, 2005, of the revised Code Relief Request RR-89-35, Rev. 1, provided in Attachment 1, in order for DNC to meet its outage schedule.

In a letter dated December 5, 2003, the NRC directed DNC to provide a justification to support the approval of the MNSA as a permanent repair should DNC decide to keep a MNSA in service beyond the period for which temporary approval has already been granted. This information has been incorporated into RR-89-35, Rev. 1. DNC has also provided in Attachment 2 specific responses to each of the items in the NRC December 5, 2003 correspondence.

In a letter dated March 15, 2002,1 DNC provided Westinghouse Design Report DAR-Cl-02-3, Rev. 0, Addendum to CENC-1 180, Analytical Report for Northeast Utilities Service Company, Millstone Point Station Unit 2 Pressurizer to assist the staff with its review of RR-89-35. This document is also applicable to RR-89-35, Rev. 1. Westinghouse considered the material provided in the March 15, 2002, letter to be proprietary information, and as such it was requested to be exempt from public disclosure for commercial reasons. Since this information continues to be considered proprietary, was previously provided, and is accessible by the NRC, it is not being resubmitted with the current request.

If you should have any questions regarding this submittal, please contact Mr. Paul R.

Willoughby at (804) 273-3572.

Very truly yours, Leslie N. Hartz Vice President - Nuclear Engineering I J. A. Price letter to U. S. Nuclear Regulatory Commission, "Millstone Nuclear Power Station, Unit 2, Request RR-89-35, Modifications Regarding Use of Mechanical Nozzle Seal assemblies for Pressurizer Heater Penetration Nozzles (TAC No. MB4039)"

Serial No.04-140 Relief Request RR-89-35, Rev. 1 Page 3 Attachments

1) RR-89-35, Rev. 1, Request to Use an Alternative to ASME Code Section XI for Installation of Mechanical Nozzle Seal Assemblies on Pressurizer Heater Penetration Nozzles

2) NRC Analysis and Inspection Criteria Commitments contained within this letter: None cc: U. S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 Mr. V. Nerses Senior Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8C2 Rockville, MD 20852-2738 Mr. S. M. Schneider NRC Senior Resident Inspector Millstone Power Station

r ATTACHMENT 1 USE OF AN ALTERNATIVE TO ASME CODE SECTION XI FOR INSTALLATION OF MECHANICAL NOZZLE SEAL ASSEMBLIES (MNSAS) ON PRESSURIZER HEATER PENETRATION NOZZLES REQUEST RR-89-35, REV. 1 DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

MILLSTONE POWER STATION, UNIT 2

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 1 of 10 REQUEST RR-89-35, REV. 1. USE OF AN ALTERNATIVE TO ASME CODE SECTION Xl FOR INSTALLATION OF MECHANICAL NOZZLE SEAL ASSEMBLIES (MNSAS) ON PRESSURIZER HEATER PENETRATION NOZZLES CONTENTS 1.0 ASME CODE COMPONENT(S) AFFECTED ............................................. 2 2.0 CODE REQUIREMENTS ............................................. 2 2.1 Applicable Code Edition and Addenda .............................................. 2 2.2 Applicable Code Requirement(s) ............................................... 2 3.0 REASON FOR REQUEST ............................................. 3 4.0 PROPOSED ALTERNATIVE ............................................. 3 4.1 Mechanical Nozzle Seal Assembly (MNSA) Details .......................... 3 5.0 BASIS FOR ALTERNATIVE .......................... 5 5.1 Potential for Corrosion or Material Stress Issues ................................. 5 5.1.1 Erosion/Corrosion of Low Alloy Steel Components . 5 5.1.2 "J"-Weld Cracking .6 5.1.3 Grafoil Seal Corrosion .6 5.1.4 Hardware Corrosion .6 5.1.5 Design Stress Report .7 5.2 Installation, Inspection, and Testing of the MNSAs .............................. 7 6.0 DURATION OF PROPOSED ALTERNATIVE ............................................. 9 7.0 PRECEDENTS ............................................. 9

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 2 of 10 REQUEST RR-89-35, REV. 1, USE OF AN ALTERNATIVE TO ASME CODE SECTION XI FOR INSTALLATION OF MECHANICAL NOZZLE SEAL ASSEMBLIES (MNSAS) ON PRESSURIZER HEATER PENETRATION NOZZLES ProposedAlternative in Accordance with 10 CFR 50.55a(a)(3)(i)

- Alternative Provides Acceptable Level of Quality and Safety -

1.0 ASME CODE COMPONENT(S) AFFECTED System: Reactor Coolant System (RCS)

Component: Pressurizer Heater Penetration Nozzles Code Class: Pressurizer heater penetration nozzles are in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) Class 1 portions of the RCS.

2.0 CODE REQUIREMENTS

2.1 Applicable Code Edition and Addenda

The ASME Code Section XI repair and replacement program at Millstone Unit No. 2 is in accordance with the 1998 Edition, no Addenda. Millstone Unit No. 2 is currently in the Third Ten-Year Interval of the Inservice Inspection (ISI) Program, which began on April 1, 1999.

2.2 Applicable Code Requirement(s)

Existing flaws in ASME Code Class components must be removed by mechanical means, or the components be repaired or replaced to the extent necessary to meet the acceptance standards in ASME Code Section Xl, Article IWB-3000. Detection of leaks in the structural portion of an ASME Code Class 1, 2, or 3 component is direct evidence of a flaw in a component.

Paragraphs IWA-4220 of Section XI require that repairs and the installation of replacements to the RCS pressure boundary be performed and reconciled in accordance with the Owner's Design Specifications and Original Code of Construction for the component or system. The RCS pressurizer was designed and constructed to the rules of ASME Section III, 1968 Edition with Addenda through summer 1969 (hereinafter referred to as the Construction Code).

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 3 of 10 3.0 REASON FOR REQUEST This request is submitted in support of inspection activities required during future refueling outages that involve on-going inspections of the pressurizer heater penetrations. Dominion Nuclear Connecticut, Inc. (DNC) requests approval to use the installed Mechanical Nozzle Seal Assemblies (MNSAs) as permanent repairs.

During the spring 2002 refueling outage at Millstone Unit No. 2, evidence of Primary Water Stress Corrosion Cracking (PWSCC) was detected and temporary repairs were made in two pressurizer heater penetration nozzles. These nozzles are welded to the pressurizer bottom head with internal J-groove welds. DNC requested and was granted Code relief to use the MNSAs specifically for the temporary repairs on both nozzles.

MNSAs are an alternative to certain requirements of Section Xl of the ASME Code that have been demonstrated by industry experience to provide an acceptable level of quality and safety for restoring structural integrity and leak tightness to the RCS. Based on experience with Alloy 600 nozzles at MPS2 and throughout the industry, DNC believes a reasonable potential exists for future degradation from PWSCC in other pressurizer heater penetration nozzles as the service life of these components increases. To address the potential degraded condition of the pressurizer, DNC is intending to replace the MPS2 pressurizer in the fall 2006 refueling outage, which will eliminate the continued need for the installed MNSA-1s. The replacement of the pressurizer is part of a long-term plan to mitigate concerns with primary water stress corrosion cracking (PWSCC) of Alloy 600 and the associated weld metals 82 and 182 at MPS2.

4.0 PROPOSED ALTERNATIVE Pursuant to the provisions of 10 CFR 50.55a(a)(3)(i), DNC requests U.S. Nuclear Regulatory Commission (NRC) authorization to use MNSAs as a permanent alternative repair method to ASME Code Section Xl requirements for the repair of pressurizer heater penetration nozzles. DNC is intending to replace the MPS2 pressurizer in the fall 2006 refueling outage, which will eliminate the continued need for the installed MNSA-1s. The proposed use of MNSAs is intended to address identified leaks attributed to PWSCC that have been detected while performing inspections during refueling outages, and to maintain the heater penetration nozzle pressure boundary integrity.

4.1 Mechanical Nozzle Seal Assembly (MNSA) Details The pressurizer heater penetration nozzles consist of a sleeve made of SB-167, (Inconel 600) and an internal diameter J-Groove weld (Inconel) joining the sleeve to the bottom head of the pressurizer made of SA533-Gr. B CL1 (Alloy Steel). The Inconel J-Groove weld provides the primary system

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 4 of 10 pressure boundary. Figure 1 shows the typical concept of the MNSA replacement for a pressurizer heater penetration nozzle.

suLr THREADER PM IFPPRTOPUNTWAsCR LOWETA:R f LATE TOP SEfATER SLEEYE- M EO4&NIL NOZL cSS SeAEoAL wsOSCEET ICADSOFTOBELLRVUEREW ItalsoactAsLto RE an t o f the Therefore, MNSA eLAcE bOARD)t th sE and s integrit WIATER SLEEVE MXE04A.MrAL NOZZLE SEAL ASSY D 5SOCKET HEAD3XttlLDR SCREW Fiur 1: Typca Aseml0 Drwn of a MNS Replacemen____t 0-C fo a SECTION

/ - _LCKEtl HEAD Figure 1: Typical Assembly Drawing of a MNSA Replacement for a Pressurizer Heater Penetration Nozzle fucton ofA the exsiged The MNSA is a mechanical device that acts as a complete replacement of the "J" weld between an Inconel 600 nozle and the pressurizer bottom head, to prevent leakage from cracks caused by Stress Corrosion Cracking.

It also acts to restrain the nozzle from ejecting if the "J" weld or the heater penetration sleeve completely fails (360 degree circumferential crack).

Therefore, the MNSA replaces both the sealing and structural integrity functions of the existing weld.

The seal is created by compressing the Grafoil Split Packing against the nozzles at the nozzle to head Outside Diameter (OD) interface. The compression collar transmits the load to the Grafoil split packing, while the packing is retained within the seal retainer and compression collar. The compressive load is generated when the hex head bolts are threaded into the pressurizer bottom head and torqued. The installation of the hex head bolts does not violate the primary system pressure boundary. The compressive load is then transmitted to the compression collar through the upper flange. No additional load is imparted on the existing J-weld by application of the MNSA.

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 5 of 10 The nozzle is held from ejecting by the top plate that is anchored to the upper flanges through tie rods, and secured in place by hex nuts. The top plate is installed with a small gap between the nozzle and its bottom surface. Only if the nozzle-to-bottom head weld completely fails will the top plate act as a restraint; otherwise, it is subject to no load during operating conditions.

5.0 BASIS FOR ALTERNATIVE The typical repair methods for degraded pressurizer heater penetration nozzles are extremely difficult to implement on an emergent basis due to the system conditions required to perform the work and the limited time in which those conditions exist during an outage. These repairs would require the unplanned extension of drained down or defueled conditions and a significant increase in worker radiation exposure to perform the work on an emergent basis. The continued use of MNSAs will provide DNC with an acceptable level of quality and safety for maintaining structural integrity and leak tightness to the RCS while not requiring the scheduled drained down or defueled work window to be challenged unnecessarily.

The MNSAs are designed, fabricated, and constructed using approved ASME Code materials in accordance with the applicable rules of ASME Section IlIl. The MNSAs are designed to prevent separation of the joint under all service loadings.

This is supported by technical analysis and tests that meet the design criteria specified in the ASME Code Section IlIl. Additionally, MNSA installations would be accessible for inspection, maintenance and removal.

5.1 Potential for Corrosion or Material Stress Issues There are no potential corrosion or material stress issues associated with the application of the MNSAs to the pressurizer bottom head at Millstone Unit No. 2. Degradation mechanisms for the intended service period were considered and addressed in the design of the MNSA as follows:

5.1.1 Erosion/Corrosion of Low Alloy Steel Components A through-wall crack in the nozzle could be a source of erosion/corrosion. However, the borated water will stagnate in the annulus between the Inconel 600 nozzle sleeve and the low alloy steel component. In the absence of a replenishment mechanism, the boric acid and available oxygen will be consumed, and eventually the corrosion process will stop.

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 6 of 10 5.1.2 "J"-Weld Cracking The design of the MNSA-1 provides a method to replace the sealing function of the J-groove weld as well as the inherent anti-ejection feature of the weld. The long-term stability of a flaw in the J-groove weld that will be left in place has been demonstrated by calculation.

5.1.3 Grafoil Seal Corrosion The Grafoil seal material that is used in nuclear applications is composed of 99.5% graphite, with the remaining 0.5% made up of ash, halides, and sulfur (concerns for corrosion of low alloy steel).

The Grafoil seal itself is chemically resistant to attack from nearly all organic and inorganic fluids, and is very resistant to borated water.

Galvanic corrosion can occur between two materials that are electrically connected and have a measurable voltage potential difference as noted by the two materials positions in the electromotive series. Graphite is very high on the electromotive series (cathode) and carbon steel is much lower on the electromotive series (anode). However the conductivity of primary water is quite low so that there is not enough of a current flow to cause galvanic corrosion. Graphite gaskets and seals are used extensively in both the primary and secondary systems of PWRs without galvanic corrosion.

5.1.4 Hardware Corrosion All the components of the MNSA are fabricated from corrosion resistant materials. Most components are 300 series stainless steel.

Fasteners and tie rods are made from SA-453 Grade 660 (a precipitation hardened austenitic stainless steel). Boric acid corrosion of the materials of construction for the MNSA and the outer surfaces of the vessel has been assessed by Combustion Engineering Owners Group (CEOG) and through other testing and analysis. With the current ASME Section Xl required inspections, a leaking MNSA would be detected before significant corrosion of the pressurizer bottom head occurs. Ifthe MNSA device leaks, the bolts may be exposed to borated water or steam under conditions in which deposits or slurries will develop. At stress levels present in the MNSA application, these bolts will operate satisfactorily for more than one fuel cycle. The leaking MNSA will be discovered and repaired as part of the Boric Acid Corrosion Control Program walk-

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 7 of 10 down inspections, limiting the exposure to these conditions to a cycle or less.

5.1.5 Design Stress Report The MNSA is designed as a "safety-related" primary pressure boundary component in accordance with the rules of NB-3200.

Modification of the RCS pressurizer for MNSA installation has been analyzed in accordance with the Original Construction Code. In a letter dated March 15, 2002,(') DNC submitted a Design Stress Report(2) that was prepared by Westinghouse Electric Company for the pressurizer as an 'Addendum to the Pressurizer Analytical Stress." The Design Stress Report demonstrates that the use of the MNSA on the pressurizer heater penetration nozzles will comply with the ASME Code Section III requirements. The Design Stress Report considered criteria that are bounding for the spectrum of pressurizer heater penetration nozzles at Millstone Unit No. 2 and included the following items:

a. analysis of the component being built to a later edition of the Code;

b. analysis of fatigue to demonstrate that the Code prescribed cumulative usage factor of 1.0 is not exceeded;

c. analysis that there is adequate reinforcement in the wall of the pressurizer bottom head for the bolt holes;

d. analysis that stresses under all service conditions do not exceed allowable values as stated in the ASME Code Section III.

5.2 Installation, Inspection, and Testing of the MNSAs In preparation for the MNSA repairs, DNC performed a visual examination of any leaking nozzles. An informational ultrasonic test (UT) was performed to determine a thickness measurement near the nozzles. A comparison of the data was made between the leaking and non-leaking penetrations to evaluate if any measurable corrosion damage was present around a leaking nozzle.

1) DNC letter, "Request RR-89-35 Modifications Regarding Use of Mechanical Nozzle Seal Assemblies for Pressurizer Heater Penetration Nozzles (TAC No. MB4039)," dated March 15, 2002, Accession No. ML020850718.

(2) Westinghouse Electric Company, Design Report No. DAR-CI-02-3, Rev. 0, dated 03/05/2002.

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 8 of 10 The installation procedure for the MNSAs has a step to check that the surface of the pressurizer around the nozzle is suitable for the Grafoil seal.

The technicians were instructed on what constitutes an acceptable surface.

Remedial action to improve surface conditions was not necessary. This guidance was demonstrated to be effective for successful installations of the MNSAs at MPS2.

Millstone performed system leak checks and bolting checks in accordance with ASME Section Xl requirements. These checks included the following:

a. As required by IWA-4600, Section Xl, 1989 Edition, DNC performed a VT-1, preservice inspection, on all MNSA installations in accordance with IWB-2200.

b. During plant startup (Mode 3), after initial MNSA installation and during subsequent plant restarts following a refueling outage, the pressurizer heater penetration nozzle MNSAs are pressure tested and inspected for leakage. To ensure quality of the installation and continued operation with the absence of leakage, a pressure test with VT-2 visual examination will be performed on each of the installed MNSAs with insulation removed. The test will be performed as part of plant re-start and will be conducted at normal operating pressure with the test temperature determined in accordance with the MPS2 pressure and temperature limits as stated in the MPS2 Technical Specifications. Additionally, VT-3 exams will be performed to verify general structural and mechanical condition of the MNSAs.

These examinations are performed in accordance with the 1989 Edition of ASME Section Xl under the current third 10-year ISI program and as such meet the personnel qualification requirements and acceptance criteria of the Code. The VT-2 visual examination also meets the plant's boric acid inspection program requirements and will be enhanced to specify that the examination shall include visual access to at least 3600 of bare metal around each MNSA. In addition to these examinations, DNC considers the bolting of the MNSAs as an Examination Category B-G-2 item and the requirements for this bolting state that a VT-1 visual examination at least once each inspection interval shall be performed. This VT-1 visual examination may be performed with the bolting (a) in place under tension; (b) when the connection is disassembled; or (c) when the bolting is removed. Later Editions of NRC approved ASME Section Xl recognized that in order to perform a useful VT-1 visual examination, bolting must be disassembled, and thus require this examination only when the connection is disassembled. For purposes of this justification, MPS2 proposes to perform a VT-1 visual examination only if a

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 9 of 10 connection is disassembled. Finally, one aspect of this VT-1 visual examination that is not covered in the Code requirements is the threaded area of the bolt holes in the base metal of the pressurizer. These bolt holes will receive a VT-1 visual examination any time the connection is disassembled.

ASME is currently developing a Code Case to provide ISI requirements for MNSAs. In the future, these requirements may ultimately be different than what DNC has proposed within this request for use at MPS2. DNC has determined the proposed requirements provide an adequate level of quality and safety by addressing the requested type of inspections (e.g., a visual examination VT-2 with insulation removed), inspection scope, periodicity of inspections, inspection qualification, and inspection criteria necessary to ensure the structural integrity of the MNSA bolting and threaded holes in the pressurizer to which the MNSA is attached for the licensed life of the facility.

6.0 DURATION OF PROPOSED ALTERNATIVE The proposed alternative for the use of MNSAs is as an acceptable repair for leakage from cracking between the alloy 600 penetrations and the J-welds to the base material. DNC requests that the staff approve their use as permanent repairs, contingent on acceptable visual inspection results of the MNSAs, conducted in accordance with ASME Code, Section Xl. DNC is intending to replace the MPS2 pressurizer in the fall 2006 refueling outage, which will eliminate the continued need for the installed MNSA-1 s.

7.0 PRECEDENTS This request is a revision to a previously approved request that established the precedent for the use of MNSAs at MPS2. During the spring 2002 refueling outage, DNC requested and was granted Code relief for this type of installation on two leaking pressurizer heater penetration nozzles. (3)(41 This relief request proposes to expand the applicability of the previously approved use of the MNSA at MPS2 to permit the continued use of the MNSAs as permanent repairs. DNC is intending to replace the MPS2 pressurizer in the fall 2006 refueling outage, which will eliminate the continued need for the installed MNSA-1s. In a Safety Evaluation (3) NRC letter, "Safety Evaluation of Relief Request RR-89-35, Temporary Installation of Mechanical Nozzle Seal Assemblies on Pressurizer Heater Penetration Nozzles, Millstone Nuclear Power Station, Unit No. 2 (TAC No. MB4039)," dated March 22, 2002, Accession No. ML020730271.

(4) NRC letter, "Correction to Safety Evaluation and Review of Design Stress Report Related to Relief Request RR-89-35, Temporary Installation of Mechanical Nozzle Seal Assemblies on Pressurizer Heater Penetration Nozzles, Millstone Nuclear Power Station, Unit No. 2 (TAC No. MB4039 and MB4655)," dated June 19, 2002, Accession No. ML021500433.

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 1 Page 10 of 10 dated October 28, 2003, the NRC approved a similar request for the temporary repair of pressurizer heater sleeves using MNSAs at MPS2. In addition, in a Safety Evaluation dated October 1, 2001, the NRC approved a similar request for the temporary repair of pressurizer heater sleeves using MNSAs at Palo Verde Nuclear Generating Station.

(5) NRC letter, "Palo Verde Nuclear Generating Station Units 1, 2 and 3 - Request for Code Alternative for the Use of Mechanical Nozzle Seal Assemblies - Relief Request No. 17 (TAC Nos. MB1618, MB1619, and MB1620)," dated October 1, 2001, Accession No. ML012680076.

ATTACHMENT 2 USE OF AN ALTERNATIVE TO ASME CODE SECTION Xi FOR INSTALLATION OF MECHANICAL NOZZLE SEAL ASSEMBLIES (MNSAS) ON PRESSURIZER HEATER PENETRATION NOZZLES NRC ANALYSIS AND INSPECTION CRITERIA DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

MILLSTONE POWER STATION, UNIT 2

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 2 Page 1 of 5 NRC ANALYSIS AND INSPECTION CRITERIA

1.0 INTRODUCTION

In a letter to Dominion Nuclear Connecticut, Inc. (DNC) dated December 5, 2003, the NRC informed DNC of its position in the event a licensee decides to keep a MNSA in service beyond the period for which temporary approval has been granted. This period is two operating cycles for Millstone Power Station Unit 2 (MPS2). The information specified by the NRC to justify continued use of the MNSA has been provided in this request. To aid the staff in its review of this request, DNC has provided the information below:

2.0 ANALYSIS OF PRESSURE BOUNDARY COMPONENT NRC Requirement: 'The qualification by analysis of the pressure boundary component to which the mechanical nozzle seal assembly (MNSA) is attached by threaded bolts or tie-rods should be based on the calculation of the primary and secondary membrane, bending and shear stresses calculated from a detailed 3-D finite element analysis. The finite element model should encompass the instrument or heater nozzle through-wall hole and the adjacent tapped holes, and for MNSA-2, the machined counterbore within the nozzle hole."

Response: The MPS2 Design Stress Report, [Design Report No. DAR-C1-02-3, Rev 0, "Addendum to CENC-1180, Analytical Report for Northeast Utilities Service Company Millstone Point Station Unit 2 Pressurizer," dated 3/05/02], referred to here-in as the "Design Report" for the component (pressurizer) to which the MNSA-1s are attached, was supplied by Westinghouse and previously submitted to the NRC by DNC in support of relief request RR-89-35 on March 15, 2002.(6) This Design Report contains the qualification analysis discussed above. The current response to the statement supplied in the Westinghouse letter of February 18, 2004 (7)also applies to MPS2 with the exception that MPS2 does not have counterbores within the nozzle hole because MPS2 has only MNSA-1s installed. Westinghouse notes in their response, and DNC concurs, that the MNSA-1 is designed and analyzed to Section III of the ASME Code and meets all applicable requirements. The MNSA-1 itself and the portion of the vessel affected by the installation of a MNSA-1 have been analyzed using both three dimensional (3-D) finite element models and classical methods. The detailed 3-D analyses were used to confirm the conservatism of the ASME Code design analysis methodology for the MNSA-1 installation. All applicable stress limits are met. The qualification by analysis of the pressure boundary component to which the MNSA-1 is (6) J. A. Price letter To U. S. Nuclear Regulatory Commission, "Millstone Nuclear Power Station, Unit No. 2, Request RR-89-35 Modifications Regarding Use of Mechanical Nozzle Seal Assemblies for Pressurizer Heater Penetration Nozzles (TAC No. MB4039)," Accession No. ML020850718.

7)Westinghouse letter LTR-NRC-04-13, Ian C. Rickard To Dr. Brian Sheron, "Comments Relating to Mechanical Nozzle Seal Assemblies," dated February 18, 2004.

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 2 Page 2 of 5 attached by threaded bolts or tie rods is based on the calculation of the primary and secondary membrane, bending, and shear stresses. The analysis model encompasses the instrument or heater nozzle through-wall hole and the adjacent tapped holes, and for the MNSA-2, the machined counterbore within the nozzle hole.

3.0 QUALIFICATION ISSUES AND RESPONSES Response (general): As MNSA designer and the supplier of the MPS2 Design Report Westinghouse confirmed, and DNC agrees, that most of the NRC-recommended actions are standard elements of the design analysis of the component and the MNSA installation. Only one of the analysis requirements applicable to MPS2, Item 3.6, addressed below and recommended in the December 5, 2003, NRC letter to DNC, imposes requirements that are either in addition to or conflict with those of the ASME Code. The following responses are provided to the specific items identified and recommended by the NRC to be included in the qualification by analysis for the MNSA:

The qualification should include and be based on the following:

3.1 A list of all plant -unique pressure boundary design conditions and operating transients showing operating pressure, mean wall temperature, and wall temperature gradient, for the pressure boundary component.

Response: All plant-unique pressure boundary design conditions and operating transients, including operating pressure, mean wall temperature, and wall temperature gradient, for the pressure boundary component are addressed in the design analysis for the MNSA installation in Attachment B, Sections 6.2 and 6.3, of the Design Report.

3.2 Detailed calculation of the load in the highest-loaded bolts or tie rods, resulting from preloading, maximum operating loads, including seismic loads, and accounting for non-linear loading and unloading load-deformation characteristics of the gasket and Belleville washer packs.

Response: A detailed loading calculation was performed for the highest-loaded bolts or tie-rods, resulting from preloading and maximum operating loads, including seismic loads. The non-linear loading and unloading load-deformation characteristics of the Belleville washer packs was considered in the Design Report. This information is contained in Section 2.0 and Attachments A and B of the Design Report. The gasket seal material for the MNSA-1 is not in the load path of the assembly bolting and is not part of the design analysis used at MPS2.

3.3 Demonstration that the primary and secondary stresses resulting from the finite element analysis meet the ASME Section III NB-3200 stress intensity

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 2 Page 3 of 5 limits and appropriate special stress limits, under all design loading and service condition mechanical and thermal transients, including the effects on the tapped holes due to the highest bolt or tie-rod loads, and demonstration the Class 1 fatigue analysis of the pressure boundary will not exceed the Code prescribed cumulative usage factor limit of 1.0 for the life of the plant.

Response: The primary and secondary stresses resulting from the analysis are demonstrated to meet the ASME Section III NB-3200 stress intensity limits and appropriate special stress limits under all design loading and service condition mechanical and thermal transients, including the effects on the tapped holes due to the highest bolt or tie-rod loads. Demonstration that the Class 1 fatigue of the pressure boundary is shown not to exceed the Code prescribed cumulative usage factor limit of 1.0 for the life of the plant. This information is contained in Section 2.0 and Attachment B of the Design Report 3.4 Demonstrate that there is no interaction between adjacent pressure boundary regions where MNSAs are mounted.

Response: The MPS2 analysis is bounded by the Westinghouse analyses performed to demonstrate that adequate separation exists between MNSAs mounted on adjacent pressure boundary regions, and between the tapped holes for the MNSA and the nozzle penetration hole.

There is no interaction between adjacent pressure boundary regions where MNSAs are mounted since the required area of reinforcement is within the confines of each individual MNSA installation. These evaluations have been performed for both the upper-limit and lower-limit bounding configurations of C-E NSSS pressurizer heater nozzle arrangements. This information is contained in Section 2.0 and Attachment B of the Design Report.

3.5 Conformance with ASME Section Ii minimum wall thickness requirements at the deepest point in the counterbore should be met.

Response: MPS2 has only MNSA-1s installed and does not employ a counterbore for installation.

3.6 Demonstration that the ASME Section 111 NB-3300 area reinforcement requirements are met.

Response: Heater penetration area reinforcement requirements were addressed in the Design Report on page 8. Because the MNSA-1 does not require a counterbore, the impact of its installation on area available

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 2 Page 4 of 5 for reinforcement is minimal. The requirements for reinforcement of a MNSA-1 installation are bounded by those requirements for the MNSA-2.

All required reinforcement is integral with the vessel. Although not required when performing NB-3200 design by analysis, ASME Section III, NB-3300 area reinforcement requirements have been shown to be satisfied for the bore in a component where a MNSA was to be installed on a nozzle, both with and without, the counterbore configuration.

3.7 Reconciliation of the Owner's Construction Code and the replacement Code.

Response: Code reconciliation between the Construction Code and the replacement Code has been performed in accordance with Section Xl requirements under the MPS2 Repair and Replacement Program and was previously submitted as Attachment "C"to the Design Report.

4.0 INSERVICE INSPECTION NRC Requirement: Identify what inservice inspection program will be implemented to ensure that the structural and leakage integrity of the MNSA will be maintained throughout the licensed life of the facility. The proposed program should include consideration of the potential for leakage from the MNSA, as well as the potential for leakage from other sources which could impact the integrity of the MNSA. The proposed program should address the type of inspections (e.g., a visual examination with insulation removed), inspection scope, periodicity of inspections, inspection qualification, and inspection acceptance criteria.

Response: Currently, the ISI inspection requirements for installed MNSA-ls at MPS2 meet the requirements outlined in Relief Requests RR-89-35 and RR-89-43, and their safety evaluations. The requirements are as follows:

"During plant startup (Mode 3), after initial MNSA installation and during subsequent plant restarts following a refueling outage, the pressurizer heater penetration nozzle MNSAs will be pressure tested and inspected for leakage. To ensure quality of the installation and continued operation with the absence of leakage, a pressure test with VT-2 visual examination will be performed on each of the installed MNSAs with the insulation removed. The test will be performed as part of plant restart and will be conducted at normal operating pressure and temperature limits as stated in the MPS2 Technical Specifications. Additionally, VT-3 exams will be performed to verify general structural and mechanical condition of the MNSAs."

These examinations are performed in accordance with the 1989 Edition of ASME Section Xl under the current third 10-year ISI program and as such meet the personnel qualification requirements and acceptance criteria of the Code. The VT-2 visual

SN 04-140 Relief Request 89-35, Rev. 1 Attachment 2 Page 5 of 5 examination also meets the plant's boric acid inspection program requirements and will be enhanced to specify that the examination shall include visual access to at least 3600 of bare metal around each MNSA. In addition to these examinations, DNC considers the bolting of the MNSAs as an Examination Category B-G-2 item and the requirements for this bolting state that a VT-1 visual examination at least once each inspection interval shall be performed. This VT-1 visual examination may be performed with the bolting (a) in place under tension; (b) when the connection is disassembled; or (c) when the bolting is removed. Later Editions of NRC approved ASME Section Xl recognized that in order to perform a useful VT-1 visual examination, bolting must be disassembled, and thus require this examination only when the connection is disassembled. For purposes of this justification, MPS2 proposes to perform a VT-1 visual examination only if a connection is disassembled. Finally, one aspect of this VT-1 visual examination that is not covered in the Code requirements is the threaded area of the bolt holes in the base metal of the pressurizer. These bolt holes will receive a VT-1 visual examination any time the connection is disassembled.

ASME is currently developing a Code Case to provide ISI requirements for MNSAs. In the future, these requirements may ultimately be different than what DNC has proposed within this request for use at MPS2. DNC has determined the proposed requirements provide an adequate level of quality and safety by addressing the requested type of inspections (e.g., a visual examination VT-2 with insulation removed), inspection scope, periodicity of inspections, inspection qualification, and inspection criteria necessary to ensure the structural integrity of the MNSA bolting and threaded holes in the pressurizer to which the MNSA is attached for the licensed life of the facility.