summary of stress analysis results for the us-apwr …

Summary of Stress Analysis Results for the US-APWR Accumulator MUAP-09012-NP (R1)

Mitsubishi Heavy Industries, LTD.

Summary of Stress Analysis Results for the US-APWR Accumulator

Non-Proprietary Version

January 2011

Ⓒ2011 Mitsubishi Heavy Industries, Ltd.

All Rights Reserved



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© 2011

MITSUBISHI HEAVY INDUSTRIES, LTD.

All Rights Reserved

This document has been prepared by Mitsubishi Heavy Industries, Ltd. (“MHI”) in connection with the U.S. Nuclear Regulatory Commission’s (“NRC”) licensing review of MHI’s US-APWR nuclear power plant design. No right to disclose, use or copy any of the information in this document, other than by the NRC and its contractors in support of the licensing review of the US-APWR, is authorized without the express written permission of MHI.

This document contains technology information and intellectual property relating to the US-APWR and it is delivered to the NRC on the express condition that it not be disclosed, copied or reproduced in whole or in part, or used for the benefit of anyone other than MHI without the express written permission of MHI, except as set forth in the previous paragraph.

This document is protected by the laws of Japan, U.S. copyright law, international treaties and conventions, and the applicable laws of any country where it is being used.

MITSUBISHI HEAVY INDUSTRIES, LTD. 16-5, Konan 2-chome, Minato-ku

Tokyo 108-8215 Japan



Abstract

This report contains the results of structural evaluation of four (4) parts of the Accumulator, referred to as the ACC, for the US-APWR plant.

The evaluations performed were based on the loading conditions defined in the US-APWR Accumulator Design Specification (Ref.11.1-1) and on the procedures of ASME Boiler & Pressure Vessel Code 2001 Edition up to and including the 2003 Addenda, referred to as the ASME Code Sec. III (Ref.11.2-2, 3, 4 and 5).

The results demonstrate that the design of ACC satisfies all of the applicable structural limits of ASME Code Sec. III.


Mitsubishi Heavy Industries, LTD. i

Table of Contents

1.0 INTRODUCTION ..................................................................................................1-1

2.0 SUMMARY OF RESULTS....................................................................................2-1

3.0 CONCLUSIONS ...................................................................................................3-1

4.0 NOMENCLATURE................................................................................................4-1

5.0 ASSUMPTIONS AND OPEN ITEMS....................................................................5-1

5.1 ASSUMPTIONS ..............................................................................................5-1

5.2 OPEN ITEMS .................................................................................................5-1

6.0 ACCEPTANCE CRITERIA ...................................................................................6-1

7.0 DESIGN INPUT ....................................................................................................7-1

7.1 GEOMETRY ...................................................................................................7-1

7.2 MATERIAL .....................................................................................................7-1

7.3 LOADS, LOAD COMBINATIONS, AND TRANSIENTS............................................7-2

7.3.1 External Load ..................................................................................7-2

7.3.2 Load Combinations..........................................................................7-3

7.3.3 Thermal and Pressure Transient Loads ..........................................7-4

8.0 METHODOLOGY .................................................................................................8-1

8.1 HEAT TRANSFER COEFFICIENTS AND THERMAL ANALYSIS ..............................8-1

8.2 SEISMIC ANALYSIS ........................................................................................8-1

8.3 FATIGUE ANALYSIS MODEL AND METHOD.......................................................8-2

9.0 STRUCTURAL EVALUATION RESULTS ............................................................9-1

9.1 SHELLS & HEADS ..........................................................................................9-1

9.1.1 Dimensions......................................................................................9-1

9.1.2 Summary of Evaluation Method ......................................................9-2

9.1.3 Stress Results .................................................................................9-3

9.2 SUPPORT SKIRT............................................................................................9-4

9.2.1 Dimensions......................................................................................9-4


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9.2.2 Analytical Method ............................................................................9-4

9.2.3 Results.............................................................................................9-4

9.3 ANCHOR BOLT ..............................................................................................9-5

9.3.1 Dimensions......................................................................................9-5

9.3.2 Method of Analysis ..........................................................................9-6

9.3.3 Stress Results .................................................................................9-6

9.4 NOZZLE ........................................................................................................9-7

9.4.1 Summary of Evaluation Method ......................................................9-7

9.4.2 Stress Results .................................................................................9-7

10.0 FRACTURE MECHANICS ASSESSMENT ........................................................10-1

11.0 REFERENCE......................................................................................................11-1

11.1 DOCUMENT.................................................................................................11-1

11.2 ASME CODE ..............................................................................................11-1


Mitsubishi Heavy Industries, LTD. iii

List of Tables

Table 2-1 Summary of Most Limiting Results 2-1 Table 6-1 Stress Limit for the Shell and Heads 6-1 Table 6-2 Stress Limit for the Support 6-2 Table 6-3 Allowable Stress for the Anchor Bolt 6-2 Table 7-1 Accumulator Basic Design Drawing List 7-1 Table 7-2 Materials of Construction 7-1 Table 7-3 Material Properties (under Design Condition) 7-1 Table 7-4 Pressures Load and Temperatures 7-2 Table 7-5 Load Combinations 7-3 Table 7-6 Accumulator Design Transients Loads 7-4 Table 8-1 NC-3219.2 Fatigue Assessment 8-2 Table 9-1 Shell and Heads Results Summary 9-3 Table 9-2 Buckling Evaluation Result of Support Skirt 9-4 Table 9-3 Anchor Bolts Results Summary 9-6 Table 9-4 Nozzle Results Summary 9-7


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List of Figures

Figure 2-1 Accumulator Evaluated Parts 2-2 Figure 9-1 Shell, Heads and Support Dimensions 9-1 Figure 9-2 Anchor Bolt Dimensions 9-5


Mitsubishi Heavy Industries, LTD. v

List of Acronyms

The following list defines the acronyms used in this document. ACC Accumulator SSE Safe Shutdown Earthquake LOCA Loss-of-Coolant Accident SRSS Square-Root-of-the-Sum-of-the-Squares


Mitsubishi Heavy Industries, LTD. 1-1

1.0 INTRODUCTION

This Technical Report provides a summary of stress analysis results for the US-APWR Accumulator (ACC) consistent with MHI’ s commitment letter (Ref. 11.1-4). The content of this report follows the ASME guidelines for design reports in ASME Code Sec. III Appendix C (Ref. 11.2-5).

This report provides structural evaluations for four ACC parts listed in Table 2-1 and shown in Figure 2-1.

The results of the detailed stress analyses summarized in this report demonstrate that the four parts of the ACC that were evaluated satisfy all of the applicable structural limits of the Design Specification (Ref. 11.1-1) and the ASME Boiler & Pressure Vessel Code 2001 Edition up to and including the 2003 Addenda.



2.0 SUMMARY OF RESULTS

The evaluated parts of the ACC are shown in Figure 2-1. The structural evaluation results for these parts are provided in Section 9. The most limiting results in each evaluation are listed in Table 2-1 below.

Table 2-1 Summary of Most Limiting Results

Section Evaluated Part Ratio Note-1 Highest Fatigue Note-2

Usage Factor

9.1 Shells Heads

9.2 Nozzle

10.1 Support Skirt

10.2 Anchor Bolt

Note-1: “Ratio” is the ratio of the calculated stress intensity to the allowable stress intensity or the ratio of the required thickness to nominal thickness. Therefore, any “Ratio” less than or equal to 1.0 is acceptable.

Intensity Stress Allowable

Intensity Stress CalculatedRatio or

Thickness Nominal

Thickness RequiredRatio

Note-2: The fatigue evaluation is not mandatory because the transient conditions of this component satisfy the requirements in ASME Sec. III NC-3219 Condition B.



Figure 2-1 Accumulator Evaluated Parts

1. Shell & Heads

3. Support Skirt

4. Anchor Bolt

2. Nozzle



3.0 CONCLUSIONS

The US-APWR ACC is designed to the requirements of the ASME Boiler and Pressure Vessel Code, 2001 Edition up to and including the 2003 Addenda for the Design, Service Loadings, Operating Conditions and Test Conditions as specified in the design specification (Ref. 11.1-1).

The results summarized in this report and a review of the component design drawings, demonstrate that the US-APWR ACC satisfies all of the requirements of the design specification (Ref. 11.1-1).



4.0 NOMENCLATURE

Symbol Unit Definition

Ratio - (See Section 2.0)

Pm ksi General Primary Membrane Stress

PL ksi Local Primary Membrane Stress

Pb ksi Primary Bending Stress

Q ksi Secondary Stress

Ftb ksi Allowable Tensile Stress

Fvb ksi Allowable Shearing Stress

ft ksi Actual Tensile Stress

fv ksi Actual Shearing Stress

Sm ksi Design Stress Intensity

Sy ksi Yield Strength

Su ksi Tensile Strength

t in. Thickness (Shell, Heads, Nozzle)

T in. Flat Cover Thickness

P - Design Pressure

1/3 SSE - Design Condition & Level B Service Loading Earthquake (i.e. OBE)

SSE - Safe Shutdown Earthquake



5.0 ASSUMPTIONS AND OPEN ITEMS

5.1 Assumptions

The basic modeling assumptions from the detailed analyses were as follows:

1. The inside diameter was taken as the drawing nominal value of the cladding per NC-3122.2 (a) (Ref. 11.2-3)

2. The wall thickness was the drawing nominal value

3. The corrosion allowance of shell and head was considered to be zero

4. The anchor bolt diameter was reduced by 0.25 inches to account for potential degradation over the specified design life (i.e. corrosion allowance).

5.2 Open Items

There are no open items in this Technical Report.



6.0 ACCEPTANCE CRITERIA

The acceptance criteria of the stress intensity for the class 2 component are specified in NC-3217 (Ref. 11.2-3). Table 6-1 lists the stress limits used in evaluation for the shell, heads and nozzle. Table 6-2 lists the stress limits used in evaluation for the support, and Table 6-3 lists the allowable stresses used in evaluation for the anchor bolts.

The rules of NF-3324.6 (Ref. 11.2-4) were used for a simplified analysis applying the Level D SSE loading to the ACC. This analysis is bounding for the Design, Levels A, B, C, D and Test Conditions.

Table 6-1 Stress Limit for the Shell and Heads

Condition Stress Category Stress Limits Reference

Pm Sm

PL 1.5 Sm

Pm (or PL) + Pb 1.5 Sm

Design and

Normal (level A) PL + Pb + Q 3 Sm

Pm 1.1 Sm

PL 1.65 Sm

Pm (or PL) + Pb 1.65 Sm Upset (level B)

PL + Pb + Q 3 Sm

Pm 1.2 Sm

PL 1.8 Sm Emergency (level C)

Pm (or PL) + Pb 1.8 Sm

Pm 2 Sm

PL 3 Sm Faulted (level D)

Pm (or PL) + Pb 3 Sm

NC-3217

(Ref.11.2-3)



Table 6-2 Stress Limit for the Support

Condition Stress

Category Stress Limits Reference

Pm Sm Design and

Normal (level A) Pm + Pb 1.5 Sm

Pm Min [Max (1.2 Sy, 1.5 Sm), 0.7 Su] Faulted (level D) Pm + Pb 1.5 Min [Max (1.2 Sy, 1.5 Sm), 0.7 Su]

Table NF-3552(b)-1 (Ref.11.2-4)

Table 6-3 Allowable Stress for the Anchor Bolt

Stress Category Stress Limits Reference

Tensile Stress Ftb 2

Su

Shearing Stress Fvb 3

S62.0 u

Combined Tensile and Shearing Stress 2

vb

2

v2

tb

2

t

F

f

F

f 1.0

Table NF-3324.6 (Ref.11.2-4)



7.0 DESIGN INPUT

7.1 Geometry

The ACC basic drawings used to supply dimensions for the calculation and analysis are listed in Table 7-1. Figures describing the detailed geometry and dimensions of the parts evaluated are provided in Section 9.

Table 7-1 Accumulator Basic Design Drawing List

No. Drawing Title Reference Number

1 The Accumulator Design Drawing N0-F000A01 Rev.0 (Ref. 11.1-2)

7.2 Material

The materials of construction and material property for the ACC parts are listed in Tables 7-2 and 7-3.

Table 7-2 Materials of Construction

Part or Assembly Material

Pressure boundary plate

Outlet nozzle

Outlet nozzle safe end

Bolted closure bolts

Table 7-3 Material Properties (under Design Condition)

Material Modulus of

Elasticity (ksi) Design Stress

Intensity Sm (ksi)Yield Strength Sy

(ksi) Tensile Strength Su

(ksi) Poisson's

Ratio



7.3 Loads, Load Combinations, and Transients

The loads, load combinations, and transients are defined in the design specification (Ref.11.1-1). The following is a summary of those used for the ACC structural evaluations. Pressure Loads and Temperature Table 7-4 shows pressure load and temperature.

Table 7-4 Pressures Load and Temperatures

Parameter Value

Design pressure 700 psig

Design temperature 300oF

Normal operating pressure 640 psig

Normal operating temperature (Ambient) 70 to 120 oF

Hydrostatic test pressure 1050 psig

Minimum hydrostatic test temperature 70oF

7.3.1 External Load

The external loads are dead weight, thermal expansion loads, seismic loads and accident loads.



7.3.2 Load Combinations

The loads combinations considered in the analysis are listed in the Table 7-5 below.

Table 7-5 Load Combinations

System Operating Condition

Service Stress Limit Service Loading Combination

Design Design

Dead Weight Loads

Design Pressure

Mechanical Loads

Normal Level A

Dead Weight Loads

Maximum Pressure

Thermal Loads*1

Mechanical Loads

Upset Level B

Dead Weight Loads

Maximum Pressure

Thermal Loads*1

Mechanical Loads

Seismic(1/3 SSE) Loads

Emergency Level C

Dead Weight Loads

Maximum Pressure

Thermal Loads*1

Mechanical Loads

Faulted Level D

Dead Weight Loads

Maximum Pressure

Thermal Loads*1

Mechanical Loads

±SRSS(Seismic(SSE) Loads + Accident Loads*2)

Test Test Dead weight Load

*1 Applied to the nozzle within the limits of reinforcement in the primary stress evaluation.

*2 If more than one Accident Load, each is to be analyzed separately.



7.3.3 Thermal and Pressure Transient Loads

The design transients are listed in the Table 7-6 below. These transients were determined based on a 60-year plant operating period. Although each transient has a plant operating condition associated with it, for the ACC the Level B, C and D plant condition transients were treated as design conditions. Because these loading conditions are so low, this report evaluates the Level D SSE acceleration and compares them to allowable limits of each design condition.

Table 7-6 Accumulator Design Transient Loads

Mark Transient Occurrence Remark

0 Pressurization / depressurization events 120 0 to 640, 640 to 0 psig, 120 oF

1-1 a) Hydrostatic pressure test 10 0 to 1050, 1050 to 0 psid, 120oF

1-2 b) Injection test 5

1-3 c) Check valve operation test 60 440 to 400 psid

2 In leak of primary water at full power (Plant: Level B) 10 120 oF

3 Out leak of N2 gas at full power (Plant: Level B) 720 695 to 586,586 to 695 psid, 120 oF

4 Large loss of coolant accident (Plant: Level D) 1 300 oF

5 Small loss of coolant accident (Plant: Level C) 10 640 psid normal operational pressure cycle for taking unit

120 oF



8.0 METHODOLOGY

The code classification of the ACC is ASME Sec. III class 2. This component functions when large flow injection is needed to refill the reactor vessel (i.e. during the postulated LOCA event) and is subject only to the loads identified in Section 7.0. Hand calculations were used to determine the structural acceptability of this component.

8.1 Heat Transfer Coefficients and Thermal Analysis

The ACC operating temperature is less than 120 oF (always less than the design temperature 300 oF) and there are no significant thermal transients.

8.2 Seismic Analysis

The seismic analysis is conducted using the beam element model. The analysis code is ANSYS ver. 11.0. The evaluated parts are the following:

- Shell

- Support Skirt



8.3 Fatigue Analysis Model and Method

Table 8-1 NC-3219.2 Fatigue Assessment NC-3219.2 Condition B Criteria Accumulator Evaluation



9.0 STRUCTURAL EVALUATION RESULTS

9.1 Shells & Heads

9.1.1 Dimensions

Figure 9-1 shows the shell and heads dimensions of the ACC.

Figure 9-1 Shell, Head and Support Dimensions



9.1.2 Summary of Evaluation Method

Structural calculation includes minimum required thickness calculation and calculation of reinforcements. The calculation is performed based on the following formulas.

(a) Shell Thickness

Thickness of Shell under Internal Pressure (NC-3224.3)

P5.0S

PRt

Thickness of Shell under External Pressure (NC-3133.3)

TDo3

B4Pa

(b) Head Thickness

Thickness of Head with Pressure on Concave Side (NC-3224.8)

1eS

Dt SP

Thickness of Head with under External Pressure (NC-3133.4 (d))

TR

BPa

(c) Flat cover thickness (NC-3225.1)

3G Sd/Wh27.1S/CPdT

(d) Nozzle Thickness (NC-3324.12)

P5.0S

PRt

(e) Reinforcement for opening in shell and head

Comparison between required area specified NC-3230 and effective area for reinforcement



9.1.3 Stress Results

The calculated stress-to-allowable Ratio (See Section 2.0) results for the most limiting locations are summarized in the Table 9-1 below.

Table 9-1 Shell and Heads Results Summary

Condition Part Stress-to-Allowable Ratio Calculated by Thickness

Design



9.2 Support Skirt

9.2.1 Dimensions

Dimensions are shown in Figure 9-1.

9.2.2 Analytical Method

Compression stress used in the buckling evaluation of the support skirt is obtained by consideration of the vertical load due to ACC weight. The compression stress is compared with the allowable stress given in ASME NF-3000 (Ref.11.2-4).

9.2.3 Results

The results for the most limiting locations are summarized in the Table 9-2 below.

Table 9-2 Buckling Evaluation Result of Support Skirt

Stress-to-Allowable Ratio

Condition Part Buckling Evaluation

Design (bounding SSE loading used)

Test (hydrostatic test pressure)



9.3 Anchor Bolt

9.3.1 Dimensions

Figure 9-2 shows the anchor bolts dimensions and layout of the ACC.

Figure 9-2 Anchor Bolt Dimensions



9.3.2 Method of Analysis

Calculation method of anchor bolt stress is the following process. This method is based on typical formulas in mechanicals of materials.

(a) Calculate the moment, horizontal force and vertical force at ACC bottom level.

(b) Anchor bolt tensile stress is obtained by load combination of moment and vertical force at ACC bottom level.

Consider loads at the ACC base, displacement balance of the anchor bolts and base concrete, and anchor bolt tensile load and base concrete compression load are calculated.

(c) Anchor bolts shear stress is obtained by horizontal force at ACC bottom level.


The calculated stress-to-allowable stress ratio for the most limiting locations are summarized in below.

Results are based on deduction of a corrosion allowance of 0.25 inches from the diameter. So the analyzed bolt diameter was 2.00”.

Table 9-3 Anchor Bolts Result Summary

Condition Stress Stress-to-Allowable stress Ratio

Design



9.4 Nozzle

9.4.1 Summary of Evaluation Method

Stresses in the shell caused by nozzle load are evaluated by the Bijlaard’s Method (Ref. 11.1-5, 6). The following nozzle is evaluated:

- Outlet nozzle

Loads to be taken into account for stress calculation are internal pressure and design nozzle forces and moments. The allowable stress is based on NC-3217.


Calculation results of Outlet nozzle are shown in Table 9-4.

Table 9-4 Nozzle Results Summary

Condition Part Stress-to-Allowable Ratio Calculated by Thickness



10.0 FRACTURE MECHANICS ASSESSMENT

A detailed fracture mechanics assessment of the ACC is not required for Class 2 component in ASME Code.



11.0 REFERENCE

The following documents, codes and standards are referred to in this report.

11.1 Document

1. N0-F000L01, Rev.2, “Accumulator Design Specification”

2. N0-F000A01, Rev.0, “Accumulator Design Drawing”

3. “Manual of Steel Construction”, Eighth Edition, American Institute of Steel Construction Inc.

4. UAP-HF-08123 “Additional Information for Design Completion Plan of US-APWR Piping and Components”

5. Bijlaard, P. P.,” Stress from Radial Loads and External moments in Cylindrical Pressure Vessels”. The Welding Journal, 34(12), Research Supplement, 1955

6. Wichman, K. R. et al.,” Local Stress in Spherical and Cylindrical Shells due to External Loadings”. Welding Research Council bulletin, March 1979 revision of WRC bulletin 107/ August 1965

11.2 ASME Code

1. ASME Boiler and Pressure Vessel Code Section II (2001 Edition through 2003 Addenda)

2. ASME Boiler and Pressure Vessel Code Section III, Subsection NCA (2001 Edition through 2003 Addenda)

3. ASME Boiler and Pressure Vessel Code Section III, Division 1, Subsection NC (2001 Edition through 2003 Addenda)

4. ASME Boiler and Pressure Vessel Code Section III, Division 1, Subsection NF (2001 Edition through 2003 Addenda)

5. ASME Boiler and Pressure Vessel Code Section III, Division 1, Appendices (2001 Edition up through 2003 Addenda)

6. ASME NQA-1 (Part II and III)-1994 Edition with 1995 Addenda, Quality Assurance Requirements for Nuclear Facility Applications

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