ML050950358

10CFR50.55a(a)(3)(i) Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 660 Small-Bore Nozzles (Relief Request 31)

ML050950358
Person / Time
Site:	Palo Verde
Issue date:	03/25/2005
From:	Mauldin D Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-05237-CDM/SAB/RJR
Download: ML050950358 (18)

Text

i-44 - l; 10 CFR 50.55a(a)(3)(i)

David Mauldin Vice President Mail Station 7605 Palo Verde Nuclear Nuclear Engineering Tel: 623-393-5553 PO Box 52034 Generating Station and Support Fax: 623-393-6077 Phoenix, Arizona 85072-2034 102-05237-CDM/SAB/RJR March 25, 2005 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 2 Docket No. STN 50-529 10 CFR 50.55a(a)(3)(i) Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles (Relief Request 31)

Pursuant to 10 CFR 50.55a(a)(3)(i), Arizona Public Service Company (APS) is proposing alternatives to the requirements of American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, 1992 Edition, 1992 Addenda, Section Xl, 'Rules for Inservice Inspection of Nuclear Power Plant Components."

Specifically, APS is proposing alternatives to the required flaw characterization (IWA-3300) and successive inspections (IWB-2420). This relief references the methods and bases of Westinghouse Topical Report WCAP -15973-P, Revision 01, dated May 2004, and is being tracked by APS as Inservice Inspection (ISI) Program Relief Request 31.

This request pertains to the 10 Palo Verde Nuclear Generating Station (PVNGS) Unit 2 Alloy 600 small-bore reactor coolant system (RCS) hot leg nozzles as described in the enclosure to this letter and currently scheduled for replacement during the spring 2005 refueling outage. Details of the 10 CFR 50.55a request are contained in the enclosure to this letter. Attachment 1 of the enclosure addresses the conditions of the final safety evaluation for Westinghouse Topical Report WCAP-1 5973-P, issued January 12, 2005. of the enclosure lists the regulatory commitments made to support this request and to address previously repaired/replaced nozzles using the methods described in the Westinghouse Topical Report.

APS is requesting approval of this relief prior to Unit 2 entering Mode 2 (currently scheduled for the week of April 25, 2005), in order to support the restart from the spring 2005 refueling outage.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway 0 Comanche Peak 0 Diablo Canyon 0 Palo Verde

• South Texas Project

• Wolf Creek

U. S. Nuclear Regulatory Commission Page 2 ATTN: Document Control Desk 10 CFR 50.55a(a)(3)(i) Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles (Relief Request 31)

If you have any questions, please contact Thomas N. Weber at (623) 393-5764.

Sincerely, CDM/SAB/RJR

Enclosure:

Relief Request 31 - Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles : APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 : Regulatory Commitments Related to Relief Request 31 cc: B. S. Mallett NRC Region IV Regional Administrator M. B. Fields NRC NRR Project Manager G. G. Wamick NRC Senior Resident Inspector for PVNGS

Enclosure Relief Request 31 Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles

ISI Relief Request No. 31 Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles Background Information On May 20, 2004, the Westinghouse Owners Group (WOG) submitted Topical Report (TR) WCAP-1 5973-P, Revision 01, "Low-alloy Steel Component Corrosion Analysis Supporting Small-diameter Alloy 600/690 Nozzle Repair/Replacement Program" to the NRC staff for review. The WOG was seeking the staffs approval of the TR in order that licensees seeking relief to use half-nozzle or mechanical nozzle seal assembly (MNSA) repair/replacement techniques may reference the TR as part of their basis for using the alternate repair methods on leaking Alloy 600 nozzles in the reactor coolant pressure boundary (RCPB).

On January 12 , 2005, the NRC staff issued a final safety evaluation (SE) that found WCAP-1 5973-P, Revision 01, acceptable for referencing in licensing applications for Combustion Engineering-designed pressurized water reactors to the extent specified and under the limitations delineated in the TR and in the associated SE. The SE defines the basis for acceptance of the TR and in Section 4.4 requires licensees proposing to use the half-nozzle and MNSA repairs submit the required information contained in the TR by the conditions of the SE, to the NRC, as a relief request in accordance with 10 CFR 50.55a.

This request pertains to the 10 Palo Verde Nuclear Generating Station (PVNGS) Unit 2 Alloy 600 small-bore reactor coolant system (RCS) hot leg nozzles currently scheduled for replacement during the spring 2005 refueling outage and provides the justification that the plant specific analysis performed to support the repair/replacements are bounded by the TR and provides an acceptable level of quality and safety. Attachment 1 to this enclosure contains APS' response to the questions contained in Section 4.0

'Conclusion and Conditions," of the SE. Attachment 2 of the enclosure lists the regulatory commitments made to support this request.

I. ASME Code Component(s) Affected PVNGS Unit: 2 Component numbers: B9.32

Description:

RCS Hot Leg Instrument and Sampling Nozzles Code Class: 1 II. Applicable Code Addition and Addenda The Second 10-year inservice inspection interval code for Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3 is the American Society of Mechanical Engineers (ASME) Code, Section Xi, 1992 Edition, 1992 Addenda.

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ISI Relief Request No. 31 Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles The construction code for PVNGS Units 1, 2, and 3 is ASME Section III, 1971 Edition, and 1973 Winter Addenda.

The installation code for PVNGS Units 1, 2, and 3 is ASME Section III, 1974 Edition, and 1975 Winter Addenda.

Ill. Applicable Code Requirements Sub-article IWA-4310 of ASME Section Xl, 1992 Edition, 1992 Addenda states in part that the "defects shall be removed or reduced in size in accordance with this Paragraph." Furthermore, IWA-4310 allows, "...the defect removal area and any remaining portion of the flaw may be evaluated and the component accepted in accordance with the appropriate flaw evaluation rules of Section Xi or the design rules of either the Construction Code, or Section III, when the Construction Code was not Section MII."

The evaluation of the remaining portion of the flaw further requires successive examination as stated in IWB-2420, "Successive Inspections".

IV. Reason For Request During fabrication of the reactor coolant system (RCS) piping, Alloy 600 small-bore nozzles were welded to the interior of the RCS hot leg. Industry experience has shown that cracks may develop in the nozzle or in the weld metal joining the nozzles to the reactor coolant pipe and lead to leakage of the reactor coolant fluid.

The cracks are caused by primary water stress corrosion cracking (PWSCC).

The original design of each PVNGS unit RCS contained a total of 27 Alloy 600 small-bore hot leg penetrations. These penetrations include pressure taps, sampling line and RTD thermowell nozzles. During the Unit 2 12t refueling outage, APS has scheduled the replacement of 10 Alloy 600 small-bore hot leg nozzles.

The total removal of all Alloy 600 small-bore nozzle and/or Alloy 82/182 weld material would require accessing the internal surface of the reactor coolant piping and grinding out the attachment weld and any remaining nozzle. Such an activity would result in high radiation exposure to the personnel involved. Grinding within the pipe also exposes personnel to other safety hazards such as confined space.

The analysis in the TR has shown that any cracks in the nozzle or attachment weld and vessel/piping carbon steel base metal will not affect structural integrity or propagate through the reactor coolant pressure boundary; therefore, there is no 2

ISI Relief Request No. 31 Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles increase in the level of quality or safety as a result of removing the nozzle or the attaching weld metal.

V. Proposed Alternative and Basis for Use Pursuant to 10 CFR 50.55a(a)(3)(i), APS is proposing alternatives to the required flaw characterization (IWA-3300) and successive inspections (IWB-2420). APS will not be removing the remnant sleeve or its attachment weld.

In lieu of fully characterizing/sizing the existing cracks, APS assumed worst case cracks in the alloy 600 base and weld material and used the methodology presented in Westinghouse WCAP-1 5973-P for determining the following:

1. Determining the overall general/crevice corrosion rate for the internal surfaces of the low-alloy or carbon steel materials that will now be exposed to the reactor coolant and for calculating the amount of time the ferritic portions of the vessel or piping would be acceptable if corrosive wall thinning had occurred.

2. Calculating the thermal-fatigue crack-growth life of existing flaws in the Alloy 600 nozzles and/or Alloy 82/182 weld material into the ferritic portion of the vessels or piping.

3. Providing an acceptable bases and arguments for concluding that unacceptable growth of the existing flaw by stress corrosion into the vessel or piping is improbable.

APS has reviewed the bases and arguments presented in the TR for the overall general/crevice corrosion rate, thermal-fatigue crack-growth life of existing flaws, and the bases for concluding that growth of the existing flaw by stress corrosion into the vessels or piping is improbable. APS finds that these bases and arguments apply to the replacement of the Unit 2 hot leg small-bore nozzles. APS has evaluated these assumptions using appropriate flaw evaluation rules of Section Xl and determined that the results demonstrate compliance with ASME Section Xl criteria for the expected 40 years of plant life. As a result, APS is also requesting relief from the successive inspections required by IWB-2420.

APS has determined that the proposed alternatives will provide an acceptable level of quality and safety and are within the analysis boundaries provided in WCAP-15973-P, Revision 1. APS' responses to the conditions of the final safety evaluation are included in Attachment 1 to this enclosure.

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ISI Relief Request No. 31 Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles VI. Duration of Proposed Alternative APS has confirmed, as stated in response to Question 4.1-2 of the attachment, that from the time of half nozzle implementation until now, that the plant percentage of time during the start-up and cold shutdown conditions do not exceed the TR analysis values.

APS requests that this relief be granted for PVNGS Unit 2 and that the relief remain in effect for the remainder of plant life. Commitment 1 below requires APS to track the time at cold shutdown to assure the allowable bore diameter is not exceeded over the life of the plant.

VII. Conclusion 10 CFR 50.55a(a)(3) states:

"Proposed alternatives to the requirements of paragraphs (c), (d), (e), (f), (g), and (h) of this section or portions thereof may be used when authorized by the Director of the Office of Nuclear Reactor Regulation. The applicant shall demonstrate that:

(i) The proposed alternatives would provide an acceptable level of quality and safety, or (ii) Compliance with the specified requirements of this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety."

The proposed alternative discussed in this relief request and supported by the TR provides an acceptable level of quality and safety. Therefore, APS requests that the proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(3)(i).

APS requests approval of this relief prior to entering Mode 2 (currently scheduled for the week of April 25, 2005, in order to support the restart of PVNGS Unit 2 from the spring 2005 refueling outage.

VIII. Commitments APS makes the following commitment to assure that the overall general/crevice corrosion rate does not exceed the rate presented in WCAP 15973-P, Revision 1.

1. APS commits to continue to track the time at cold shutdown conditions against the assumptions made in the corrosion analysis to assure that the allowable 4

ISI Relief Request No. 31 Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-Bore Nozzles bore diameter is not exceeded over the life of the plant. If the analysis assumptions are exceeded, APS shall provide a revised analysis to the NRC and provide a discussion on whether volumetric inspection of the area is required.

APS makes the following commitment to address previously repaired/replaced Alloy 600 small-bore nozzles.

2. APS will reconcile the Westinghouse WCAP 15973-P Rev. 01 analysis with the non-Westinghouse analysis used to support the previous repairs of RCS hot leg Alloy 600 small-bore nozzles. When completed, APS will provide a relief request to support the previously replaced RCS hot leg nozzles in all three PVNGS units.

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-1 5973-P, Issued January 12, 2005

Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 The safety evaluation issued for the Westinghouse topical report stated that the staffs review of the methods in Topical Report (TR) WCAP-15973-P, Revision 01, indicates that the Westinghouse Owners Group's (WOG) methods and analyses in the TR are generally acceptable. To use the Westinghouse TR as a reference, the safety evaluation required the following information be addressed:

4.1 General Corrosion Assessment Licensees seeking to use the methods of the TR will need to perform the following plant specific calculations in order to confirm that the ferritic portions of the vessels or piping within the scope of the TR will be acceptable for service throughout the licensed lives of their plants (40 years if the normal licensing basis plant life is used or 60 years if the facility is expected to be approved for extension of the operating license):

NRC Question:

1. Calculate the minimum acceptable wall thinning thickness for the ferritic vessel or piping that will adjoin to the MNSA repair or half-nozzle repair.

APS Response:

Section 2.4 of the TR, determined the maximum allowable hole size relative to (1) the reduction in the effective weld shear area, and (2) the required area of reinforcement for the nozzle bore holes.

The maximum corroded hole diameter identified in the TR has been verified to apply to Palo Verde Unit 2. As for the second hole size, Palo Verde Unit 2 was used in the TR as one of the limiting hot leg pipe nozzles.

NRC Question:

2. Calculate the overall general corrosion rate for the ferritic materials based on the calculational methods in the TR, the general corrosion rates listed in the TR for normal operations, startup conditions (including hot standby conditions), and cold shutdown conditions, and the respective plant-specific times (in-percentage of total plant life) at each of the operating modes.

APS Response:

The assumptions in the TR analysis, regarding times at each of the operation modes, are as follows:

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005

• Normal Operation: 88%,

• Startup Condition - 2%,

• Cold Shutdown Condition - 10%

APS has reviewed the operating history for PVNGS Unit 2 from when the first hot leg nozzle repair was implemented and has determined the percentage of total plant time spent at each of the operating modes as follows:

• Normal Operations - 90.22%,

• Startup Conditions - 1.33%,

• Cold Shutdown Conditions - 8.44%

(PVNGS Technical Specifications Table 1.1-1 defines Cold Shutdown as a cold leg temperature of <2100 F)

The most limiting operating conditions identified by the TR analysis are Cold Shutdown (10%) and Start-up (2%). The expected percentages of plant time for U2 in these limiting conditions are 8.44% and 1.33% respectively, which are lower than the TR analysis values. Using the U2 percentages and Equation No.1 of the TR, the calculated corrosion rate (CR) for PVNGS Unit 2 is shown below:

• CR = (0.9022)(0.4 mpy) + (.01 33)(19.0 mpy) +( 0.0844)(8.0 mpy) = 1.290 mpy mpy = mills per year Thus, the projected corrosion rate for PVNGS Unit 2 does not exceed the TR corrosion rate of 1.53 mpy. Since the assumptions stated in the TR are not exceeded, a revised analysis is not required.

NRC Question:

3. Track the time at cold shutdown conditions to determine whether this time does not exceed the assumptions made in the analysis. If these assumptions are exceeded, the licensees shall provide a revised analysis to the NRC, and provide a discussion on whether volumetric inspection of the area is required.

APS Response:

APS has confirmed, as stated in response to Question 4.1-2, that from the time of half nozzle implementation until now, the plant percentage times during the start-up and cold shutdown conditions do not exceed the TR analysis values.

APS has committed to tracking this parameter (see Attachment 2).

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 NRC Question:

4. Calculate the amount of general corrosion-based thinning for the vessels or piping over the life of the plant, as based on the overall general corrosion rate calculated in Step 2 and the thickness of the ferritic vessel or piping that will adjoin to the MNSA repair or half-nozzle repair.

APS Response:

The Unit 2 corrosion rate (1.290 mpy) is used to calculate the amount of general corrosion over a 60-year period.

Corrosion = (0.001290 inch/year) (60 years)

= 0.0774 inch (radially, relative to penetration)

= 0.1548 inch (diametrically, relative to penetration)

NRC Question:

5. Determine whether the vessel or piping is acceptable over the remaining life of the plant by comparing the worst case remaining wall thickness to the minimum acceptable wall thickness for the vessel or pipe.

APS Response:

Diameter of penetration in 60 years = (0.1548 inch) + (1.120 inch) = 1.275 inch Allowable diameter in 60 years = 1.280 inch Allowable bore diameter will not be exceeded over the remaining life of the plant including life extension. Note that 60 years is considered to begin from original plant life, not at the time of repair.

4.2 Thermal-Fatigue Crack Growth Assessment Licensees seeking to reference this TR for future licensing applications need to demonstrate that:

NRC Question:

1. The geometry of the leaking penetration is bounded by the corresponding penetration reported in Calculation Report CN-CI-02-71, Revision 01.

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 APS Response:

The geometry of the leaking penetration identified in the referenced calculation (page 17) and the PVNGS nozzle geometry is compared below.

Calc PVNGS Base metal thickness: 3.75 in 3.75 in Inside radius to base metal: 21 in 21 in Cladding thickness 0.25 in 0.19 in Westinghouse has provided APS a plant specific calculation using PVNGS geometry. This calculation evaluates the crack growth for the APS specific hot leg borehole geometry and concludes that the final crack sizes computed for Palo Verde specific dimensions do not impact the conclusions of the original referenced calculation.

Table 1: Hot Leg Piping Crack Dimensions from CN-CI-02-71 Rev 01 (Borehole Diameter Used Is 0.997")

Depth Or Initial Axial Axial Circumferential Circumferential Length (in) Final (in) Allowable Final (in) Allowable (in)

Depth 0.938 0.984 > 1.3 1.001 > 1.3 Length 0.762 0.791 > 1.1 0.802 > 1.1 Table 2: Hot Leg Piping Crack Dimensions using PVNGS Dimensions (Borehole Diameter Used Is 1.120")

Depth Or Initial Axial Axial Circumferential Circumferential Length (in) Final (in) Allowable Final (in) Allowable (in)

(in)

Depth 0.950 0.999 > 1.3 1.017 > 1.3 Length 0.762 0.793 1 > 1.1 0.805 > 1.1 I It can be seen by comparing the final crack sizes in Tables 2 with those in Table 1 and those reported in References 1 and 2 that the effect of the change in the initial flaw depth from 0.938" to 0.950" and in the borehole diameter from 0.997" to 1.120" on the final crack sizes is very small and considered insignificant. Final crack sizes computed with the Palo Verde specific dimensions do not impact the conclusions made in References 1 and 2. The symbol > used under the maximum allowable crack sizes in the above tables is to be interpreted as the crack sizes which are still stable under the hot leg applied loading.

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 NRC Question:

2. The plant-specific pressure and temperature profiles in the pressurizer water space for the limiting curves (cooldown curves) do not exceed the analyzed profiles shown in Figure 6-2 (a) of Calculation Report CN-CI-02-71, Revision 01, as stated in Section 3.2.3 of the SE.

APS Response:

APS is not requesting relief from the ASME requirements for the pressurizer in this request.

NRC Question:

3. The plant-specific Charpy USE data shows a USE value of at least 70 ft-lb to bound the USE value used in the analysis. If the plant-specific Charpy USE data does not exist and the licensee plans to use Charpy USE data from other plants' pressurizers and hot-leg piping, then justification (e.g., based on statistical or lower bound analysis) has to be provided.

APS Response:

The request of USE data is not applicable to PVNGS Unit 2 since elastic-plastic fracture mechanics was not applied to the hot leg nozzles in the TR.

Furthermore, Palo Verde Unit 2 is bounded by the linear elastic fracture mechanics analysis in Calculation Report CN-CI-02-71, Revision 01, since the Unit 2 hot leg pipe RTndt is 200 F versus the 300 F value used in the TR.

4.3 Stress Corrosion Crack Growth Assessment Licensees seeking to implement MNSA repairs or half-nozzle replacements may use the WOG's stress corrosion assessment as the bases for concluding that existing flaws in the weld metal will not grow by stress corrosion if they meet the following conditions:

NRC Question:

1. Conduct appropriate plant chemistry reviews and demonstrate that a sufficient level of hydrogen overpressure has been implemented for the RCS, and that the contaminant concentrations in the reactor coolant have been typically maintained at levels below 10 ppb for dissolved oxygen, 150 ppb for halide ions, and 150 ppb for sulfate ions.

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 APS Response:

A review of plant chemistry records show that the halide /sulfate concentrations levels have been maintained below 150 ppb for chloride and sulfate and below 100 ppb for fluoride over the last two operating cycles. Oxygen levels are maintained below 10 ppb during power operation and below 100 ppb during plant startups [RCS temperature >250F]. There is no oxygen limit when the RCS temperature is below 250F.

During startup, hydrogen overpressure is established when the RCS is > 400 degrees F for crud management. An RCS hydrogen overpressure of > 15 cc/kg is established prior to criticality (hard hold point) and is maintained in a range of 25 to 50 cc/kg in Modes 1 and 2. In Modes 1 and 2, RCS hydrogen is a Control Parameter with Action Level 1 outside the range of 25 - 50 cc/kg, an Action Level 2, less than 15 cc/kg, and an Action Level 3 less than 5 cc/kg. Chemistry administrative control procedures do not allow critical reactor operation with the RCS hydrogen concentration less than 15 cc/Kg without immediate corrective action. The nominal operating band for RCS hydrogen is 25 to 50 cc/Kg.

Thus the conclusion reached in the TR with respect to stress corrosion cracking, applies to PVNGS.

NRC Question:

2. During the outage in which the half-nozzle or MNSA repairs are scheduled to be implemented, licensees adopting the TR's stress corrosion crack growth arguments will need to review their plant-specific RCS coolant chemistry histories over the last two operating cycles for their plants, and confirm that these conditions have been met over the last two operating cycles.

APS Response:

The review identified in the response above was completed in March 2005, prior to the upcoming U2 outage.

4.4 Other Considerations The WOG's general corrosion rates for normal operations, startups, and cold shutdown conditions, as applied in Equation 1 of the TR, are considered by the staff to be acceptable, as long as the existing corrosion data used to determine the bounding rates is applicable. If additional laboratory or field data becomes available that invalidates the TR's general corrosion rate values for normal operations, startups, and cold shutdown conditions, the WOG should send in an addendum to the TR that evaluates the impact of the new data of the corrosion rate 6

Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 values for normal operations, startups, and cold-shutdown conditions, and that provides a new overall general corrosion rate assessment for the ferritic components under assessment. The WOG's thermal fatigue crack growth analysis is only applicable to the evaluation of a single flaw. Should the WOG desire to extend the scope of its thermal-fatigue crack growth analysis to the analysis of multiple cracks in near proximity to one another, the WOG is requested to submit an appropriate addendum to the TR that provides the new thermal-fatigue crack growth assessment for the multiple flaw orientation. The scope of WCAP-1 5973-P, Revision 01, does not address any welding considerations for the MNSA or half-nozzle designs. Licensees seeking to implement half-nozzle replacements or MNSA repairs of their Alloy 600 nozzles will need to assess the welding aspects of the design and may need to submit a relief request to implement the alternatives to the requirements of the ASME Code, Section Xl as required by 10 CFR 50.55a.

The staffs review of the corrections to the flaw evaluation, changes in corrosion rate and clarification of the stress corrosion cracking in carbon and low alloy steels to WCAP-1 5973-P, Revision 01, indicates that the changes in the evaluation and analyses are generally acceptable. The requirements addressed in Section 4.0 of this SE must be addressed, along with the following, when this TR is used as the basis for the corrosion and fatigue crack growth evaluation when implementing a half-nozzle or MNSA repair:

NRC Question:

1. Licensees using the MNSA repairs as a permanent repair shall provide resolution to the NRC concerns addressed in the NRC letter dated December 8, 2003, from H. Berkow to H. Sepp (ADAMS Accession No. ML033440037) concerning the analysis of the pressure boundary components to which the MNSA is attached, and the augmented inservice inspection program.

APS Response:

APS is not currently planning on using a MNSA as a permanent repair.

NRC Question:

2. Currently, half-nozzle and MNSA repairs are considered alternatives to the ASME Code, Section Xl. Therefore, licensees proposing to use the half-nozzle and MNSA repairs shall submit the required information contained in WCAP-15973-P, Revision 01, by the conditions of this SE, to the NRC as a relief request in accordance with 10 CFR 50.55a.

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Attachment I APS' Response to the Conditions of the Final Safety Evaluation for Topical Report WCAP-15973-P, Issued January 12, 2005 APS Response:

This letter provides APS' response to the conditions of the SE as a relief request in accordance with 10 CFR 50.55a.

References:

1. Westinghouse Report CN-CI-02-71, Rev.1, "Summary of Fatigue Crack Growth Evaluation Associated with Small Diameter Nozzles in CEOG Plants", dated 3/31/04.

2. Westinghouse Report WCAP-1 5973-P, Rev.1, "Low-Alloy Steel Component Corrosion Analysis Supporting Small-Diameter Alloy 600/690 Nozzle Repair/Replacement Programs", dated May 2004.

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Attachment 2 Regulatory Commitments Related to Relief Request 31 The following table identifies those new actions committed to by APS in this document.

Any other statements in this submittal are provided for information purposes and are not considered to be regulatory commitments. Please direct questions regarding these commitments to Thomas N. Weber at (623) 393-5764.

REGULATORY COMMITMENT DUE DATE Tracking #

APS commits to continue to track the time at cold shutdown conditions against the assumptions made in the corrosion analysis to assure that the allowable bore diameter RCTSAI is not exceeded over the life of the plant. If Active - ongoing the analysis assumptions are exceeded, (no due date) 2782964 APS shall provide a revised analysis to the NRC and provide a discussion on whether volumetric inspection of the area is required.

APS will reconcile the Westinghouse WCAP 15973-P Rev. 01 analysis with the non-Westinghouse analysis used to support RCTSAI the previous repairs of RCS hot leg Alloy July 29 2005 600 small-bore nozzles. When completed, J 2782958 APS will provide a relief request to support the previously replaced RCS hot leg nozzles in all three PVNGS units.

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