ML24213A323

Transmittal of Relief Request (RR) No. 71: Re-Submittal of RR-30

ML24213A323
Person / Time
Site:	Palo Verde   (NPF-041, NPF-051, NPF-074)
Issue date:	07/31/2024
From:	Horton T Arizona Public Service Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
102-08833-TAH/MDD
Download: ML24213A323 (1)

Text

10 CFR 50.55a A member of the STARS Alliance LLC Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek 102-08833-TAH/MDD July 31, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 Renewed Operating License Nos. NPF-41, NPF-51, NPF-74 Transmittal of Relief Request (RR) No. 71: Re-Submittal of RR-30 Pursuant to 10 CFR 50.55a(z)(1), Arizona Public Service Company (APS) requests NRC staff approval of a proposed alternative to a 10 CFR 50.55a(c), Reactor Coolant Pressure Boundary, American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section III, Code Case parameter. Specifically, APS requests approval of an alternative to ASME Section III, Sub-Section NB-3356, Code Case 1361-2, Socket Welds,Section III, to allow a diametral clearance (cMAX) of 0.062 inch between the replacement pressurizer heater sleeves and the heater sheaths, instead of 0.045 inch as specified in the Code Case. This reactor coolant pressure boundary relief request resubmittal is being tracked by APS as Inservice Inspection (ISI) Program RR-71 and is to renew existing RR-30.

Pursuant to 10 CFR 50.55a(z)(1), licensees may request authorization to implement alternative methodologies that deviate from regulatory requirements provided they achieve an acceptable level of quality and safety. The Enclosure of this letter provides the justification for the resubmitted relief request for Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3 for the period of extended operation (PEO), which begins for Unit 1 on June 1, 2025.

RR-30 was previously submitted on November 11, 2004 [Agencywide Documents Access and Management System (ADAMS) Accession No. ML043230554] and approved by the NRC on November 19, 2004 (ADAMS Accession No. ML043240213). RR-30 is applicable to each of the PVNGS Units and was originally approved for the remainder of plant life; prior to license extension in 2011. In addition to justifying the Code Case deviation, RR-71 addresses environmentally assisted fatigue that applies to wetted reactor coolant system pressure boundary components that are monitored for fatigue as part of license extension obligations. RR-71 approval is needed prior to entering the PEO.

Included within the Enclosure to this letter are the two attachments from the original RR-30 for NRC staff ease of retrieval, as they were not included with the original NRC public posting (ADAMS Accession No. ML043230554).

A pre-submittal meeting was held between APS and the NRC staff on July 12, 2024. APS requests authorization of the relief request by May 1, 2025, to facilitate adoption prior to the PEO.

Todd A. Horton Sr. Vice President Nuclear Regulatory & Oversight Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7602 Tel: 623.393.6418

102-08833-TAH/MDD 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Relief Request No. 71 Page 2 No commitments are being made to the Nuclear Regulatory Commission by this letter.

Should you need further information regarding this submittal, please contact Michael D.

DiLorenzo Department Leader Nuclear Regulatory Affairs - Licensing at (623) 393-3495.

Sincerely, Todd Horton Senior Vice President Nuclear Regulatory & Oversight MDD/WEH

Enclosure:

Relief Request No. 71 - 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter Attachments: 1. Structural Integrity Calculation Package, File No. PV-04Q-329

2. Structural Integrity Calculation Package, File No. PV-04Q-330 cc:

J. D. Monninger NRC Region IV Regional Administrator W. T. Orders NRC NRR Project Manager for PVNGS N. Cuevas NRC Acting Senior Resident Inspector for PVNGS Horton, Todd (Z10098)

Digitally signed by Horton, Todd (Z10098)

Date: 2024.07.31 12:27:35

-07'00'

Enclosure PVNGS Relief Request No. 71 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter

Relief Request No. 71 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter Page 1 of 5 Background Information Each Palo Verde Nuclear Generating Station (PVNGS) unit has a pressurizer containing 36 heater sleeves attached to the bottom head. The original Alloy 600 heater sleeves were replaced with Alloy 690 heater sleeves to address concerns with primary water stress corrosion cracking in the fall outages of 2003 (Unit 2), 2004 (Unit 3), and 2005 (Unit 3).

It was determined that the diametral clearances between the replacement Alloy 690 pressurizer heater sleeves and the heater sheaths may be as great as 0.062 inch in order to enable the insertion of the heaters into the sleeves after sleeve replacement. PVNGS UFSAR Table 5.2-3, NRC Regulatory Guide 1.84 Code Cases Used on PVNGS, identifies that ASME Section III Code Case 1361-2 was used for the original pressurizer assembly (heater sleeve to heater sheath fillet weld).

In Figure 1 of Code Case 1361-2, the cMAX diametral clearance between connecting parts is specified as 0.045 inch. Therefore, pursuant to 10 CFR 50.55a(a)(z)(1) APS proposes an alternative of 0.062 inch in lieu of the 0.045 inch cMAX diametral clearance specified in Code Case 1361-2. The other requirements specified in Code Case 1361-2 for joint configuration are met with the increased diametral clearance with no appreciable increase in stress.

As discussed in this relief request, this proposed alternative would provide an acceptable level of quality and safety and would therefore meet the requirements of 10 CFR 50.55a(a)(z)(1). Relief Request 30 previously authorized the proposed alternative at Palo Verde, Units 1, 2 and 3, for the remainder of plant life. This authorization came prior to submission of license extension, which was authorized in 2011.

I. ASME Code Component(s) Affected PVNGS Units:

1, 2 and 3 Item number:

B15.140 (previously B4.20)

==

Description:==

Pressurizer Heater Sleeve, 36 per Unit.

Code Class:

1 II. Applicable Code Addition and Addenda The Fourth 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, 2013 Edition.

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.

III. Applicable Code Requirements Sub-article NB-3356 ASME Section III 1971 Edition, and 1973 Winter Addenda states in part: Fillet welds shall not be used in vessels for joints of Categories A, B, C or D (NB-3351).

Code Case 1361-2 States in part:

Relief Request No. 71 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter Page 1 of 5 Appurtenances with outside diameter equal to that of 2-inch standard pipe size and less may be constructed using weld joints in accordance with Fig 1, provided the following requirements are met:

1. The design of the joint shall be such that stresses will not exceed the limits described in NB-3220 and tabulated in tables I-1.1 and I-1.2.

2. A fatigue strength reduction factor of not less than 4 shall be used in the fatigue analyses of the joints.

3. The finished welds shall be examined by a magnetic particle or by a liquid Penetrant method in accordance with Section V and the Acceptance Standards of NB-5000.

4. End closure connections may be made with fillet welds or partial penetration welds provided the conditions stated above are met.

Figure 1 note cMAX = diametral clearance between connecting parts cMAX =

0.045 in.

IV. Reason For Request The original replacement of the Alloy 600 heater sleeves exhibited challenges in sleeve alignment and subsequent installation of heaters. As a result, a significantly longer duration than originally projected was required for sleeve welding. In an attempt to resolve the heater insertion challenges, the inside diameter of the replacement sleeve was increased from 1.273 inch to 1.300 inch. The heater insertion challenges were essentially resolved utilizing the increased sleeve diameter. Ultimately, less radiation dose was incurred since substantially less time was spent by personnel on the working platform. This alternative has already previously been authorized and rework after two decades to restore the diametral clearance is not practical.

V. Proposed Alternative and Basis for Use Pursuant to 10 CFR 50.55a(a)(z)(1), APS proposes alternatives to Code Case 1361-2 by using a maximum 0.062 inch (0.055 inch nominal) diametral clearance between the pressurizer heater and heater sleeve in lieu of the Code Case requirement of 0.045 inch (cMax). This proposed alternative would provide an acceptable level of quality and safety and thus would meet the requirements of 10 CFR 50.55a(a)(z)(1).

The original PVNGS pressurizer stress reports prepared by Combustion Engineering (CE) evaluated the integrity of the heater sleeve-to-heater sheath fillet weld applying internal pressure and the effects of steady state temperature. The original construction for the heater sleeve was Alloy 600. The original construction for the heater sheath was either Alloy 600 or SA 213, Type 316. The materials of construction for the sleeve and heater sheath utilized in the PVNGS pressurizers for the new design now fall into two category types as follows:

1. A replacement sleeve made out of Alloy 690 material is used in combination with Alloy 600 for the heater sheath material.

2. A replacement sleeve made out of Alloy 690 material is used in combination with SA 213, Type 316 stainless steel for the heater sheath material.

The original fillet weld connected a sleeve with an ID of 1.273 inch and an OD of 1.66 inch, and a heater sheath with an OD of 1.245 inch. The resulting fillet weld had a leg of 0.1875 inch with a nominal diametral clearance between the parts of 0.028 inch.

Relief Request No. 71 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter Page 3 of 5 The new design replacement heater sleeve has an ID of 1.30 inch and an OD of 1.66 inch, with the same heater sheath OD of 1.245 inch. The fillet weld size connecting these parts is the same as the original construction, namely a 0.1875 inch leg.

However, the maximum diametral clearance is 0.062 inch (0.055 inch nominal). The reason for the increased diametral clearance is explained in section IV of this relief request.

The original stress reports from CE modeled the fillet weld with a nominal design clearance between the parts of 0.028 inch using finite element analysis (FEA) techniques. The original analysis by Structural Integrity Associates, Inc. (SI), for Relief Request 30, evaluated the same fillet weld with a maximum diametral clearance between the parts of 0.062 inch (0.055 inch nominal). The later analyses utilize the results from the original CE stress report to determine acceptability of the replacement heater sleeve/sheath weld configuration. In the SI Report, the loads and weld cross sectional properties are modified by a ratio factor that takes into account the change in diametral clearance between the parts. The results of the SI evaluation demonstrate compliance with the ASME Code NB-3220 allowables for Primary Membrane, Primary Membrane plus Bending, Primary plus Secondary and Fatigue stresses.

Subsequent analysis by SI was performed using an Environmentally Assisted Fatigue (EAF) screening (References 1 and 2). This screening identified the bounding components that must be managed for EAF during the PVNGS period of extended operation. This analysis concluded that monitoring the pressurizer heater sleeve is sufficient to ensure that all components in that thermal zone - including the heater sheath to sleeve weld - remain within EAF limits. The heater sheath to sleeve weld is bounded by the sentinel in the pressurizer heater sleeve to weld pad location for EAF considerations. The SI FatiguePro4 software shows that for each PVNGS unit, the EAF for the pressurizer heater sleeve are currently below the limit of 1.0 and are projected to remain below 1.0 through 60 years of operation.

Code Case 1361-2 was approved in March of 1972. At that time, the ASME Code did not prepare a basis document for their Code Case assumptions as it is being done presently. Thus, the basis for the diametral clearance requirement of 0.045 inch in Code Case 1361-2 is not specified. However, it is surmised that by maintaining the clearance between the parts relatively small, the amount of bending stresses that can be imparted on the fillet weld due to deflection of the parts are negligible. The manner in which the PVNGS pressurizer heaters are held in place, fixed at one end by the fillet weld and supported at the other end by two consecutive heater support plates satisfies this criterion (i.e., minimizes bending stresses at the fillet weld, see Figure 1). The clearance between the heater and heater support plates is nominally 0.037 inch (1.282 inch minus 1.245 inch).

Based on the above discussion, the reconfigured weld joint is acceptable from a stress/fatigue perspective for the period of extended operation.

VI. Duration of Proposed Alternative APS requests relaxation of the cMAX limit for the pressurizer heaters be granted for each unit and that the relaxation remain in effect for the remainder of plant life (through initial license extension).

Relief Request No. 71 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter Page 4 of 5 VII.

Conclusion 10 CFR 50.55a(a)(z) states:

Alternatives to the requirements of paragraphs (b) through (h) of this section or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation. A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate that:

(1) Acceptable level of quality and safety. The proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a compensating increase in quality and safety. 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 Section V would provide an acceptable level of quality and safety as it would meet the objectives of Code Case 1361-2 and the reconfigured weld joint is acceptable from a stress/fatigue perspective.

Analysis by SI was performed using an EAF screening. This screening identified the bounding components that must be managed for EAF during the PVNGS period of extended operation. This analysis concluded that monitoring the pressurizer heater sleeve is sufficient to ensure that all components in that thermal zone - including the heater sheath to sleeve weld - remain within EAF limits. The heater sheath to sleeve weld is bounded by the sentinel in the pressurizer heater sleeve to weld pad location for EAF considerations. The SI FatiguePro4 software shows that for each PVNGS unit, the EAF for the pressurizer heater sleeve are currently below the limit of 1.0 and are projected to remain below 1.0 through 60 years of operation. Therefore, APS requests that the proposed alternative be authorized pursuant to 10 CFR 50.55a(a)(z)(1).

The proposed alternative was originally authorized under Relief Request 30 for the remainder of plant life and expires at midnight June 1, 2025 (Unit 1), April 24, 2026 (Unit 2), and November 25, 2027 (Unit 3). APS requests NRC approval of the proposed relief by May 1, 2025, to support Unit 1 entering the Period of Extended Operation on June 1, 2025. The proposed alternative authorization would expire at midnight on June 1, 2045 (Unit 1), April 24, 2046 (Unit 2) and November 25, 2047 (Unit 3).

VIII. References

1. Letter Report JDC 24-001, Dated April 5, 2024, Relief Request 71 Support-EAF Monitoring with SIA: FatiguePro 4

2. Structural Integrity Associates Calculation No. 1301095.302, Revision 1, Additional Analysis of Screened-In Locations, Palo Verde Units 1, 2, and 3, November 2016

Relief Request No. 71 10 CFR 50.55a(a)(z)(1) Request for Alternative to a 10 CFR 50.55a(c) Reactor Coolant Pressure Boundary, ASME Section III, Code Case 1361-2 Parameter Page 5 of 5 Pressurizer Heater/Sheath 2m Support Plate 1st Support Plate Bottom Head Pressurizer Heater Sleeve cMAX Figure 1 (Simplified)

Weld

Structural Integrity Calculation Package, File No. PV-04Q-329

FILE No.: PV-04Q-329 STRUCTURAL INTEGRITY Associates, Inc.

CALCULATION PACKAGE PROJECT No.: PV-04Q PROJECT NAME: Pressurizer Heater Sleeve Repair Evaluations CLIENT: Arizona Public Service TITLE: Heater Sleeve/Sheath Weld Evaluation - Stainless Steel Sheaths Document Revision Affected Pages Revision Description Project Mgr.

Approval Signature &

Date Preparer(s) &

Checker(s)

Signatures &

Date 0

1-7 Original Issue 11/11/04 R.A. Mattson 11/11/04 R.A. Mattson 11/11/04 A.F. Deardorff Page 1 of 7 F2001R1

Revision 0

Preparer/Date RAM 11/11/04 Checker/Date AFD 11/11/04 File No.

PV-04Q-329 Page 2 of 7 Table of Contents

1.0 INTRODUCTION

...........................................................................................................................3 2.0 MATERIAL PROPERTIES............................................................................................................3 3.0 EVALUATION................................................................................................................................5

4.0 CONCLUSION

S..............................................................................................................................6

5.0 REFERENCES

................................................................................................................................7

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PV-04Q-329 Page 3 of 7

1.0 INTRODUCTION

The original configuration for the connection between the pressurizer heater sleeves and heater sheaths consisted of a nominal 1.66 outside diameter (OD) sleeve, with an inside diameter (ID) of 1.273, connected to a nominal 1.245 OD sheath. The connection was made using a 3/16 fillet weld. The preemptive repair being implemented at Palo Verde consists of a sleeve with the same OD, but with a 1.30 ID, and the same heater sheath OD. The connection weld is assumed to be a 3/16 fillet.

The original Stress Report [1] evaluated the integrity of this fillet weld for internal pressure and the effects of steady state temperature. The materials of construction were Alloy 600 for the sleeve and SA-213, Type 316 for the sheath. For the replacement sleeve, Alloy 690 material is used. The sheath is the same Type 316 stainless steel [2].

The purpose of this calculation is to determine acceptability of the current condition.

2.0 MATERIAL PROPERTIES The Type 316 material properties used in the original Stress Report will remain unchanged, and are:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E(1) 28.2 27.7 27.1 26.6 26.1 25.4 24.8 (2) 9.16 9.34 9.47 9.59 9.70 9.82 9.93 Sm (3) 20.0 20.0 20.0 19.2 17.9 17.0 16.3 Notes:

(1)

The units for the modulus of elasticity are times 106 psi.

(2)

The units for the coefficient of thermal expansion are times 10-6 inch/inch/°F.

(3)

The units for the allowable stress intensity are ksi.

For the original Alloy 600 sleeve material, the following properties were used:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E(1) 31.5 30.9 30.5 30.0 29.6 29.2 28.6 (2) 7.20 7.40 7.56 7.70 7.80 7.90 8.00 Sm (3) 23.3 23.3 23.3 23.3 23.3 23.3 23.3 Notes:

(1)

The units for the modulus of elasticity are times 106 psi.

(2)

The units for the coefficient of thermal expansion are times 10-6 inch/inch/°F.

(3)

The units for the allowable stress intensity are ksi.

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PV-04Q-329 Page 4 of 7 For the Alloy 690 replacement sleeve material, the following properties were obtained from the ASME Code [3]:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E(1) 29.5 29.1 28.8 28.3 28.1 27.6 (2) 7.76 7.85 7.93 8.02 8.09 8.16 8.25 Sm (3) 23.3 23.3 23.3 23.3 23.3 23.3 23.3 Notes:

(1)

The units for the modulus of elasticity are times 106 psi.

(2)

The units for the coefficient of thermal expansion are times 10-6 inch/inch/°F.

(3)

The units for the allowable stress intensity are ksi.

Thermal stresses are directly related to the modulus of elasticity times the coefficient of thermal expansion for the materials being welded. Below is a comparison of E times for the materials of interest:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E (Alloy 600) 226.8 228.7 230.6 231.0 230.9 230.7 228.8 E (Alloy 690) 231.6 230.8 231.0 228.9 229.3 227.7 E (Type 316) 258.3 258.7 256.6 255.1 253.2 249.4 246.3 The increase in thermal stress can be estimated by solving the following equation, assuming that the weld stress is proportional to the differential expansion between the heater sleeve and the heater sheath:

(

)

(

)

600 600 ss ss 690 690 ss ss 0

E E

E E

=

Solving the above equation for the values presented above yields stress ratios

[(Essss-E690690)/(Essss-E600600)] as follows:

200°F 300°F 400°F 500°F 600°F 700°F 0.90 0.99 1.0 1.09 1.07 1.06 Therefore, the increase in thermal stress when using Alloy 690 material in lieu of Alloy 600 material is bounded by 10%. This will conservatively be used as a multiplication factor on total pressure plus thermal stress.

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PV-04Q-329 Page 5 of 7 3.0 EVALUATION The original Stress Report evaluated the sleeve to sheath weld for general primary stress, primary membrane-plus-bending stress, primary-plus-secondary stress, and primary-plus-secondary-plus-peak stress, which is used in the fatigue evaluation. The new 3/16 fillet weld has a throat which is reduced from that originally evaluated due to the increase in gap between the heater sleeve and sheath. This increase in gap also results in an increase in stress due to internal pressure.

The throat of the fillet weld evaluated in the original Stress Report was 0.1227. For the new configuration, the throat can be calculated as follows:

throat =

(0.6225 + 0.1875 - 0.65) cos 45°

=

0.1131 The applied axial pressure force used in the original analysis was 3.182 kips, whereas the revised applied axial pressure force for the new configuration is:

F

=

()(2,500)(0.65)2

=

3.318 kips For the primary stress evaluation, the original calculated stress is 6.48 ksi, which is less than the allowable stress value of 9.78 ksi for the Type 316 material. For the new configuration, the stress is increased by the increase in force (3.318/3.182) and by the decrease in the throat of the fillet weld (0.1227/0.1131). The calculated primary stress is, therefore:

Pm =

(6.48)(3.318/3.182)(0.1227/0.1131)

=

7.33 ksi < 9.78 ksi = 0.6 Sm Therefore, primary stress criteria are maintained.

Primary membrane-plus-bending stresses were not explicitly calculated in the original Stress Report since there are no primary bending loads on the fillet weld. However, the conservative methodology used in the Stress Report [4] for the other unit will be included herein, in which the bending component of stress was conservatively assumed to be primary.

The reported maximum stress intensity [4] is 18.31 ksi, with an allowable stress intensity of 34.9 ksi for Alloy 600 material. This calculated value will be increased due to the factors cited above.

However, the throat factor will be squared in order to account for bending across the throat as opposed to pure shear.

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PV-04Q-329 Page 6 of 7 The calculated primary membrane-plus-bending stress intensity is, therefore:

PL+Pb

=

(18.31)(3.318/3.182)(0.1227/0.1131)2

=

22.5 ksi < 24.4 ksi = 1.5 Sm for Type 316 material Therefore, primary membrane-plus-bending stress criteria are maintained.

For the primary-plus-secondary stress evaluation, the reported maximum stress intensity is 30.35 ksi, with an allowable stress intensity of 48.9 ksi. This calculated value will be increased due to the factors cited above. However, the throat factor will be squared in order to account for bending across the throat as opposed to pure shear.

The calculated primary-plus-secondary stress intensity is, therefore:

PL+Pb+Q

=

(30.35)(1.10)(3.318/3.182)(0.1227/0.1131)2

=

41.0 ksi < 48.9 ksi = 3.0 Sm Therefore, primary-plus-secondary stress criteria are maintained.

The maximum calculated primary-plus-secondary-plus-peak stress intensity is 141.75 ksi, based upon the use of a stress concentration factor of 5.0. Again using the above ratio with a pressure increase factor for the trip transient of (2.55/2.50), the calculated primary-plus-secondary-plus-peak stress intensity is:

PL+Pb+Q+F =

(141.75)(2.55/2.50)(1.10)(3.318/3.182)(0.1227/0.1131)2

=

195.2 ksi The allowable number of cycles for an alternating stress of 97.6 ksi is about 1,950 cycles. For 1,050 total cycles [1], considering a 60 year life, the cumulative usage factor may be bounded by (1,050/1,950), or 0.54, which is less than the allowable value of 1.0.

4.0 CONCLUSION

S Based upon the above evaluations, the use of a 1.30 ID heater sleeve is acceptable relative to the criteria contained within the ASME Code. In addition, the tolerance on the heater sheath (maximum diametrical clearance between the components of 0.062) has been evaluated, with the following results:

Pm

= 7.49 ksi < 9.78 ksi = 0.6 Sm PL+Pb

= 23.5 ksi < 24.4 ksi = 1.5 Sm PL+Pb+Q = 42.8 ksi < 48.9 ksi = 3.0 Sm U

= 0.62 < 1.0

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PV-04Q-329 Page 7 of 7

5.0 REFERENCES

1. Combustion Engineering, Inc., Analytical Report for Arizona Unit No. 3 Pressurizer, Report Number CENC-1490, October 1981.

2. Framatome ANP, Inc. Heater Element Assembly, Drawing Number 5042376, Revision 1/

Watlow Electric Mfg. Co., Pressurizer Heater, Drawing Number WDG-3580, 8/15/80.

3. ASME Boiler and Pressure Vessel Code, 1995 Edition with 1997 Addenda.

4. Combustion Engineering, Inc., Analytical Report for Arizona Unit No. 1 Pressurizer, Report Number CENC-1336, August 1978.

Structural Integrity Calculation Package, File No. PV-04Q-330

FILE No.: PV-04Q-330 STRUCTURAL INTEGRITY Associates, Inc.

CALCULATION PACKAGE PROJECT No.: PV-04Q PROJECT NAME: Pressurizer Heater Sleeve Repair Evaluations CLIENT: Arizona Public Service TITLE: Heater Sleeve/Sheath Weld Evaluation - Alloy 600 Sheaths Document Revision Affected Pages Revision Description Project Mgr.

Approval Signature &

Date Preparer(s) &

Checker(s)

Signatures &

Date 0

1-6 Original Issue 11/11/04 R.A. Mattson 11/11/04 R.A. Mattson 11/11/04 A.F. Deardorff Page 1 of 6 F2001R1

Revision 0

Preparer/Date RAM 11/11/04 Checker/Date AFD 11/11/04 File No.

PV-04Q-330 Page 2 of 6 Table of Contents

1.0 INTRODUCTION

...........................................................................................................................3 2.0 MATERIAL PROPERTIES............................................................................................................3 3.0 EVALUATION................................................................................................................................5

4.0 CONCLUSION

S..............................................................................................................................6

5.0 REFERENCES

................................................................................................................................6

Revision 0

Preparer/Date RAM 11/11/04 Checker/Date AFD 11/11/04 File No.

PV-04Q-330 Page 3 of 6

1.0 INTRODUCTION

The original configuration for the connection between the pressurizer heater sleeves and heater sheaths consisted of a nominal 1.66 outside diameter (OD) sleeve, with an inside diameter (ID) of 1.273, connected to a nominal 1.245 OD sheath. The connection was made using a 3/16 fillet weld. The preemptive repair being implemented at Palo Verde consists of a sleeve with the same OD, but with a 1.30 ID, and the same heater sheath OD. The connection weld is assumed to be a 3/16 fillet.

The original Stress Report [1] evaluated the integrity of this fillet weld for internal pressure only, since all materials were the same. The materials of construction were Alloy 600 for the sleeve and sheath.

For the replacement sleeve, Alloy 690 material is used. The sheath is the same Alloy 600 material [2].

The purpose of this calculation is to determine acceptability of the current condition.

Since thermal steady state stress analyses were not performed for the units with the same sleeve and sheath material, materials information will be taken from another units Stress Report that has Type 316 stainless steel sheaths [3].

2.0 MATERIAL PROPERTIES The Type 316 material properties used in the original Stress Report [3] will remain unchanged, and are:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E(1) 28.2 27.7 27.1 26.6 26.1 25.4 24.8 (2) 9.16 9.34 9.47 9.59 9.70 9.82 9.93 Sm (3) 20.0 20.0 20.0 19.2 17.9 17.0 16.3 Notes:

(1)

The units for the modulus of elasticity are times 106 psi.

(2)

The units for the coefficient of thermal expansion are times 10-6 inch/inch/°F.

(3)

The units for the allowable stress intensity are ksi.

For the original Alloy 600 sleeve material, the following properties were used [1]:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E(1) 31.5 30.9 30.5 30.0 29.6 29.2 28.6 (2) 7.20 7.40 7.56 7.70 7.80 7.90 8.00 Sm (3) 23.3 23.3 23.3 23.3 23.3 23.3 23.3 Notes:

(1)

The units for the modulus of elasticity are times 106 psi.

(2)

The units for the coefficient of thermal expansion are times 10-6 inch/inch/°F.

(3)

The units for the allowable stress intensity are ksi.

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Preparer/Date RAM 11/11/04 Checker/Date AFD 11/11/04 File No.

PV-04Q-330 Page 4 of 6 For the Alloy 690 replacement sleeve material, the following properties were obtained from the ASME Code [4]:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E(1) 29.5 29.1 28.8 28.3 28.1 27.6 (2) 7.76 7.85 7.93 8.02 8.09 8.16 8.25 Sm (3) 23.3 23.3 23.3 23.3 23.3 23.3 23.3 Notes:

(1)

The units for the modulus of elasticity are times 106 psi.

(2)

The units for the coefficient of thermal expansion are times 10-6 inch/inch/°F.

(3)

The units for the allowable stress intensity are ksi.

Thermal stresses are directly related to the modulus of elasticity times the coefficient of thermal expansion for the materials being welded. Below is a comparison of E times for the materials of interest:

Property/Temperature 100°F 200°F 300°F 400°F 500°F 600°F 700°F E (Alloy 600) 226.8 228.7 230.6 231.0 230.9 230.7 228.8 E (Alloy 690) 231.6 230.8 231.0 228.9 229.3 227.7 E (Type 316) 258.3 258.7 256.6 255.1 253.2 249.4 246.3 The increase in thermal stresses, which are calculated in Reference 3, can be estimated by solving the following equation:

(

)

(

)

600 600 ss ss 690 690 600 600 0

E E

E E

=

Solving the above equation for the values presented above yields stress ratios

[(E600600- E690690)/(Essss-E600600)] as follows:

200°F 300°F 400°F 500°F 600°F 700°F

-0.10

-0.01 0.00 0.09 0.07 0.06 Since the thermal stresses due to the Alloy 600/690 property differences are very small and are less than 10% of those for the stainless steel/Alloy 600 combination, the thermal stresses due to the differences between Alloy 600 and Alloy 690 materials will not be considered further.

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Preparer/Date RAM 11/11/04 Checker/Date AFD 11/11/04 File No.

PV-04Q-330 Page 5 of 6 3.0 EVALUATION The original Stress Reports [1] evaluated the sleeve to sheath weld for general primary stress, primary membrane-plus-bending stress, and primary-plus-secondary-plus-peak stress, which is used in the fatigue evaluation. The new 3/16 fillet weld has a throat which is reduced from that originally evaluated due to the increase in gap between the heater sleeve and sheath. This increase in gap also results in an increase in stress due to internal pressure.

The throat of the fillet weld evaluated in the original Stress Report was 0.1227. For the new configuration, the throat can be calculated as follows:

throat =

(0.6225 + 0.1875 - 0.65) cos 45°

=

0.1131 The applied axial pressure force used in the original analysis was 3.182 kips, whereas the revised applied axial pressure force for the new configuration is:

F

=

()(2,500)(0.65)2

=

3.318 kips For the primary stress evaluation, the original calculated stress is 6.48 ksi in the fillet weld, which is less than the allowable stress value of 13.98 ksi for the Alloy 600 material. For the new configuration, the stress is increased by the increase in force (3.318/3.182) and by the decrease in the throat of the fillet weld (0.1227/0.1131). The calculated primary stress is, therefore:

Pm =

(6.48)(3.318/3.182)(0.1227/0.1131)

=

7.33 ksi < 13.98 ksi = 0.6 Sm Therefore, primary stress criteria are maintained.

For the primary membrane-plus-bending stress evaluation, the reported maximum stress intensity is 18.31 ksi, with an allowable stress intensity of 34.9 ksi. This is very conservative in that the bending portion of the total stress is secondary. This calculated value will be increased due to the factors cited above. However, the throat factor will be squared in order to account for bending across the throat as opposed to pure shear.

The calculated primary membrane-plus-bending stress intensity is, therefore:

PL+Pb

=

(18.31)(3.318/3.182)(0.1227/0.1131)2

=

22.5 ksi < 34.9 ksi = 1.5 Sm

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Preparer/Date RAM 11/11/04 Checker/Date AFD 11/11/04 File No.

PV-04Q-330 Page 6 of 6 Therefore, primary membrane-plus-bending stress criteria are maintained.

The maximum calculated primary-plus-secondary-plus-peak stress intensity is 81.55 ksi, based upon the use of a stress concentration factor of 5.0. Again using the above ratio with a pressure increase factor for the trip transient of (2.55/2.50), the calculated primary-plus-secondary-plus-peak stress intensity is:

PL+Pb+Q+F =

(81.55)(2.55/2.50)(3.318/3.182)(0.1227/0.1131)2

=

102.1 ksi The allowable number of cycles for an alternating stress of 51.0 ksi is greater than 20,000 cycles. For 1,050 total cycles [1], considering a 60 year life, the cumulative usage factor is (1,050/(20,000), or 0.05, which is less than the allowable value of 1.0.

4.0 CONCLUSION

S Based upon the above evaluations, the use of a 1.30 ID heater sleeve is acceptable relative to the criteria contained within the ASME Code. It is understood that any effect of thermal stress has not been considered herein. However, the effect should be small as compared to that evaluated for the Alloy 600/stainless steel junction in Reference 3, and the margins relative to acceptance criteria are large. In addition, the tolerance on the heater sheath (maximum diametrical clearance between the components of 0.062) has been evaluated, with the following results:

Pm

= 7.49 ksi < 13.98 ksi = 0.6 Sm PL+Pb

= 23.5 ksi < 34.9 ksi = 1.5 Sm U

= 0.05 < 1.0

5.0 REFERENCES

1. Combustion Engineering, Inc., Analytical Report for Arizona Unit No. 1 Pressurizer, Report Number CENC-1336, August 1978/ Combustion Engineering, Inc., Analytical Report for Arizona Unit No. 2 Pressurizer, Report Number CENC-1395, August 1979.

2. General Electric, 11/4 Dia. Pressurizer Heater-50KW, Drawing Number 24D505199, Revision J.

3. Combustion Engineering, Inc., Analytical Report for Arizona Unit No. 3 Pressurizer, Report Number CENC-1490, October 1981.

4. ASME Boiler and Pressure Vessel Code, 1995 Edition with 1997 Addenda.