ML19171A094
| ML19171A094 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 03/21/2019 |
| From: | Southern Nuclear Operating Co |
| To: | Office of New Reactors |
| Shared Package | |
| ML19171A096 | List:
|
| References | |
| ND-19-0665 AP1000RCP-06-009-NP, Rev 3 | |
| Download: ML19171A094 (29) | |
Text
Southern Nuclear Operating Company ND-19-0665 Vogtle Electric Generating Plant (VEGP) Units 3 and 4 AP1 OOORCP-06-009-NP, "Structural Analysis Summary for the AP1000 Reactor Coolant Pump High Inertia Flywheel," Revision 3 (Public Version)
(Enclosure 6 consists of 28 pages, plus this cover page)
Attachmen 2 svP _svo_oos413 CURTISS--
WRIGHT Structural Analysis Summary for the AP1000 Reactor Coolant Pump High Inertia Flywheel November 22, 2016 AP1 OOORCP-06-009-NP Revision 3 March 5, 2019 Page 2 of 29
© 2016 Curtiss-Wright Electro-Mechanical Corporation. All Rights Reserved.
Attachmen 2 SVP _SV0_005413 RECORD OF REVISIONS Revision Revision Content No.
0 Original - Issued for the preliminary flywheel design containinQ tunQsten heavv alloy versus depleted uranium.
Revised to reflect the following design changes:
- Increased length of lower flywheel to increase inertia.
- Changed end plate and shell material from Alloy 690 to Alloy 625
- Retainer ring material changed from 18Ni Maraging steel to 18Cr-18Mn Alloy Steel
- Increased the thickness and shrink fit of retainer ring to compensate for the lower 18Cr-18Mn strength and higher thermal expansion material properties.
The following sections were revised:
- Update Table of Contents
- Changed 18Ni Maraging Steel to 18Cr-18Mn Alloy Steel throughout.
- Added second paragraph in Executive Summary
- Section 2.0 - update shrink fit and fracture mechanics evaluation 1
- Figure 3-1, updated to current configuration
- Section 5.1, updated calculated primary stress and fracture mechanics evaluation results
- Section 5.1.1, updated materials and properties
- Figure 5-1, updated ROT
- Section 5.1.2, updated shrink fit
- Section 5.1.3, updated primary stress calculations
- Section 5.1.4, updated hoop stress results and shrink fit
- Included fatigue evaluation results for enclosure welds
- Section 5.1.6, updated fracture mechanics analysis results
- Section 5.2, updated missile penetration results to reflect flywheel design changes and final RCP configuration
- Section 6.0, updated reference 1 and changed reference 12 The following changes were made:
- Updated Table of Contents
- Improved quality of Figure 3-1
- Added second paragraph of section 4.2.2 which was 2
inadvertently omitted
- Table 5-1, changed "18Ni maraging steel" to "18Cr-18Mn Alloy Steel"
- Section 5.1.6, changed "0.780" to "0.870" in next to last sentence due to error
- Sixth bullet in section 5.2.1, added last sentence 3
The following changes were made:
Clarified wordinq is Section 4.2.3 Page ii AP1 OOORCP-06-009-NP Written By J. R. Finegan March 5, 2019 Page 3 of29 Revised By J. R. Finegan J. R. Finegan R.R. Klein
Attachmen 2 SVP _SV0_005413 TABLE OF CONTENTS March 5, 2019 Page 4 of 29 Page RECORD OF REVISIONS...................................................................................................................... ii TABLE OF CONTENTS......................................................................................................................... iii LIST OF TABLES................................................................................................................................... iv LIST OF FIGURES.................................................................................................................................. v EXECUTIVE
SUMMARY
....................................................................................................................... vi
1.0 INTRODUCTION
.................................................................................................................... 1-1 2.0
SUMMARY
OF RESULTS..................................................................................................... 2-1
3.0 DESCRIPTION
OF COMPONENTS...................................................................................... 3-1 4.0 DESIGN REQUIREMENTS................................................................................................... 4-1 4.1 LOADING CONDITIONS.......................................................................................... 4-1 4.2 CRITERIA.................................................................................................................. 4-2 4.2.1 American Society of Mechanical Engineers Code....................................... 4-2 4.2.2 Regulatory Guide 1.14................................................................................. 4-2 4.2.3 Standard Review Plan................................................................................. 4-3 5.0 ANALYTICAL METHODS AND RES UL TS...............................................*............................ 5-1 5.1 FLYWHEEL CALCULATIONS.................................................................................. 5-1 5.1.1 Analytical Model........................................................................................... 5-2 5.1.2 Concentric Ring Model Geometry and Shrink-Fit........................................ 5-5 5.1.3 Outer Retainer Cylinder Rotational Primary Stresses................................. 5-5 5.1.4 Concentric Ring Elastic Hoop Stresses....................................................... 5-8 5.1.5 Flywheel Enclosure Welds........................................................................... 5-9 5.1.6 Fracture Mechanics of Outer Retainer Cylinder.......................................... 5-9 5.2 MISSILE PENETRATION....................................................................................... 5-11 5.2.1 Assumptions............................................................................................... 5-11 5.2.2 Energy Analysis......................................................................................... 5-12 5.2.3 Missile Containment Analysis Results....................................................... 5-13 5.2.4 Conclusion................................................................................................. 5-13
6.0 REFERENCES
....................................................................................................................... 6-1 Page iii AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 Table 5-1 Table 5-2 Table 5-3 Table 5-4 LIST OF TABLES March 5, 2019 Page 5 of 29 Mechanical Properties................................................................................. 5-3 AP1000 Motor Cavity Flywheel Hoop Stresses.......................................... 5-8 Pump Containment Thicknesses Analyzed in Missile Analysis................. 5-12 Pressure Boundary Capacity for Missile Containment.............................. 5-13 Page iv AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SVO_D05413 Figure 3-1 Figure 5-1 LIST OF FIGURES March 5, 2019 Page 6 of 29 AP1000 Canned-Motor Reactor Coolant Pump........................................... 3-2 Flywheel Assembly Dimensions.................................................................. 5-4 Pagev AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 EXECUTIVE
SUMMARY
March 5, 2019 Page 7 of29 This report summarizes the evaluation of the high inertia flywheel assembly for the AP1000 reactor coolant pump. The AP1000 reactor coolant pump is a single-stage, hermetically sealed, high-inertia, centrifugal canned-motor pump. The pump motor and all rotating components are contained inside a pressure vessel.
Revision 1 of this report is issued to incorporate changes to the flywheel design. As a result of progress in the detailed design efforts and an increase in the required inertia, there have been significant changes to the high-inertia flywheel design. The flywheel changes include both configuration changes and a change from depleted uranium to tungsten heavy alloy as the high density flywheel material.
The pump design includes flywheel assemblies in two locations to provide the inertia required for pump coastdown. Each flywheel assembly consists of a cylindrically shaped set of heavy metal inserts held against a Type 403 stainless steel inner hub by an 18Cr-18Mn Alloy Steel outer retainer cylinder and hermetically sealed on the ends by nickel-chromium-iron alloy (Alloy 625) plates and on the outside diameter by a thin shell of nickel-chromium-iron alloy (Alloy 625).
Flywheel evaluations have been completed to determine the component shrink-fit requirements, the outer retainer cylinder primary stress, and the outer retainer cylinder critical flaw sizes. Also, missile penetration calculations were performed to evaluate the capacity of the pressure boundary structures to absorb the energy of the heavy metal inserts in the unlikely event of a flywheel fracture.
The flywheel structure was evaluated to ensure calculated stresses of all structural components (inner hub, heavy metal inserts, and outer retainer cylinder) are less than the applicable stress limits at assembly and all operating conditions.
The calculated stresses in the outer retainer cylinder during both normal operating conditions (1800 rpm) and design conditions (2250 rpm) are less than the applicable stress limits.
Results of a fracture mechanics evaluation show that the critical flaw size is well within ultrasonic inspection technique capability.
Page vi AP 1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 8 of 29 Missile penetration calculations show that in the unlikely event of a flywheel fracture, the flywheel heavy metal inserts.will not have sufficient energy to penetrate the pump pressure boundary structures.
Page vii AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413
1.0 INTRODUCTION
March 5, 2019 Page 9 of29 This report summarizes the evaluation of the revised design of the high inertia flywheel assembly for the AP1000 reactor coolant pump. The geometry analyzed is based on the overall lengths and diameters derived from the pump outline drawing (Reference 1). The flywheel assembly design consists of a cylindrically shaped set of heavy metal inserts held against a Type 403 stainless steel inner hub by an 18Cr-18Mn Alloy Steel outer retainer cylinder and hermetically sealed on the ends by nickel-chromium-iron alloy (Alloy 625) plates and on the outside diameter by a thin shell of nickel-chromium-iron alloy (Alloy 625). Radial shrink fits are imposed at assembly to prevent slippage between the shaft, the inner hub, the heavy metal inserts, and the outer retainer cylinder during pump operation. This study derives and compares stress values consistent with the non-local primary stresses reported for the depleted uranium flywheel for the AP600 evaluation (Reference 2) and the previous AP1000 evaluation in earlier revisions of this report.
The reactor coolant pump in the AP1000 design is a single-stage, hermetically sealed, high-inertia, centrifugal canned-motor pump. A canned-motor pump contains the motor and all rotating components inside a pressure vessel. The reactor coolant pump design is illustrated in
- Figure 3-1.
The reactor coolant pump pressure boundary shields the balance of the reactor coolant pressure boundary from theoretical_ worst-case flywheel failures. The reactor coolant pump pressure boundary (stator shell, flange, and casing) is analyzed to demonstrate that a fractured flywheel cannot breach the reactor coolant pump pressure boundary and impair the operation of safety-related systems and components. This meets the requirements of General Design Criteria 4. The reactor coolant pump flywheel is designed, manufactured, and inspected to minimize the potential for the generation of high-energy fragments (missiles) under any anticipated operating or accident condition consistent with the intent of the guidelines set forth in Standard Review Plan Section 5.4.1.1 and Regulatory Guide 1.14. Each flywheel is tested at an overspeed condition to verify the flywheel design and construction.
Page 1-1 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 2.0
SUMMARY
OF RES UL TS March 5, 2019 Page 10 of 29 The calculations and evaluations contained in this report show that the results of the AP 1000 flywheel stress and missile containment studies are comparable to those of the AP600 and those of the AP1000 analyses contained in earlier revisions of this report.
The applicable stress limits are derived from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section Ill (Reference 4); the Standard Review Plan, NUREG-0800 Section 5.4. f 1 (Reference 5); and Regulatory Guide 1.14 (Reference 6). Both normal operating conditions (1800 rpm) and design conditions (125% overspeed = 2250 rpm)
. were evaluated. The following summarizes the results of the evaluation.
A total radial shrink fit of [
]a,b inches was calculated for assembly of the outer retainer cylinder, which ensures maintenance of the shrink fit during all operating conditions.
The calculated primary stresses in the outer retainer cylinder, due to pump rotation for both normal and design conditions, are less than the allowable stress limits for the respective operating condition.
The fracture mechanics evaluation of the outer retainer cylinder indicates that for assembly plus design conditions, the critical flaw size was a corner flaw having a depth of 0.290 inches and surface length of 0.870 inches. This size is compatible with ultrasonic inspection capabilities.
The flywheel heavy metal inserts that contain the maximum kinetic energy were shown to not have sufficient energy to penetrate the adjacent pressure boundary components.
The details of the evaluations are provided in Section 5.
Page 2-1 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413
3.0 DESCRIPTION
OF COMPONENTS March 5, 2019 Page 11 of 29 The reactor coolant pump in the AP1000 design is a single-stage, hermetically sealed, high-inertia, centrifugal canned-motor pump. A canned-motor pump contains the motor and all rotating components inside a pressure vessel. The pressure vessel consists of the pump casing, stator closure, stator main flange, stator shell, stator lower flange, and stator cap, which are designed for full reactor coolant system pressure. Two flywheel assemblies provide the required pump coastdown time. The larger of the two flywheel assemblies is located between the motor and pump impeller. This flywheel assembly is protected from direct exposure to the hot primary water by the thermal barrier/stator closure. The smaller assembly is located within the canned motor at the thrust bearing, between the upper and lower thrust runner.
Surrounding the larger flywheel assembly are the heavy walls of the casing, thermal barrier, and stator closure, and surrounding the smaller flywheel assembly is the heavy wall of the stator lower flange. The reactor coolant pump concept is shown in Figure 3-1.
The flywheel assembly design consists of a cylindrically shaped set of heavy metal inserts held against a Type 403 stainless steel inner hub by an 18Cr-18Mn Alloy Steel outer retainer cylinder and hermetically sealed on the ends by nickel-chromium-iron alloy (Alloy 625) plates and on the outside by a thin shell of nickel-chromium-iron alloy (Alloy 625). Radial shrink fits are used at assembly to prevent slippage due to motor torque between the shaft, the inner hub, the heavy metal inserts, and the outer retainer cylinder during pump operation. The outer retainer cylinder has the same axial length as the heavy metal inserts while the inner hub and thin outer shell are axially longer to provide weld joints for securing and hermetically sealing the end plates to the inner hub and the outer thin shell.
Page 3-1 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 APIOOO RCP CONFIGURATION FOR PROTOTYPE TEST APR IL 15, 2009 PR !MARY WATER PIPING (FLOW TO EXTERNAL HEAT EXCHANGER)
EXTERNAL HEAT EXCHANGER SUPPORT -
EXTERNAL HEAT EXCHANGER UPPER RACIAL BEAR ING COOL ING WATER INLET __ __,,,_.,__,
STATOR COILS COOLING WATER OUTLET UPPER
___ __::~:!:/i:=::::::::::::!:;.~~
THRUST BEAR ING LOWER FLYWHEEL ASSEMBLY - -----iti-----...f~
~~~?Jo SLEEVE - -----t+t--- --...<...'.,
~~~;T BEAR ING - ----1-H-------r,.,;
LOWER SEAL R IHO------H:!-----;:.:;;:;:---j~
SENSOR WELL SPEED SENSOR \\JELLS March 5, 2019 Page 12 of29 BOLT OIFFUSER FL Y'JHEEL LOCK NVT THERMAL BARRIER CLOSURE COOL ING TERM !HAL GLAND LOWER RADIAL BEAR ING r---- TERM !HAL BOX THRUST RUNNERS BOLT SPEED SENSOR JUNCTION BOX Figure 3-1 AP1000 Canned-Motor Reactor Coolant Pump Page 3-2 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 4.0 DESIGN REQUIREMENTS March 5, 2019 Page 13 of 29 The design requirements for the flywheel are based on the AP1000 RCP Design Specification (Reference 7) and the requirements outlined in the AP1000 Design Control Document (DCD)
(Reference 3).
4.1 LOADING CONDITIONS The loading conditions applicable to the flywheel are summarized below:
Design Pressure Design Temperature Design Speed,
Operating Pressure Operating Temperature Normal Operating Speed Transients 2500 psia 650°F for primary coolant water 550°F estimated maximum for upper flywheel 300°F estimated maximum for lower flywheel 2250 rpm 2250 psia 537.2°F for primary coolant water 400°F estimated maximum for upper flywheel 200°F estimated maximum for lower flywheel 1800 rpm The flywheels operate in the bearing water environment that is thermally isolated from the primary coolant by the reactor coolant pump thermal barrier. With the exception of the startup and shutdown transients, it is assumed that the primary coolant transients will have a negligible affect on the flywheel. The design specification requires that 3,000 startup/shutdown cycles will be considered.
Design Mechanical Loads The AP1000 reactor coolant pump motor synchronous speed is 1800 rpm. It is required that the pump be capable of speeds up to 1.25 times the nor.mal operating speed or 2250 rpm. There is an external applied force on the flywheel assembly enclosure due to the pump internal pressure. In addition, there are loads associated with the shrink fits between the flywheel and the shaft, and between the outer retainer ring and the heavy metal inserts and inner flywheel hub.
Page 4-1 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 4.2 CRITERIA March 5, 2019 Page 14 of 29 The design criteria for the flywheel assembly are given in the AP1000 RCP Design Specification (Reference 7) and are outlined in subsection 5.4.1 of the AP10000 DCD (Reference 3). The applicable stress limits are derived from the ASME Code, Section Ill (Reference 4), Standard Review Plan, subsection 5.4.1.1 (Reference 5), and Regulatory Guide 1.14 (Reference 6).
These limits are addressed in the following subsections.
In addition to the previous criteria, the flywheel complies with the requirement of GDC 4, which requires that components important to safety be protected against the effects of missiles. l~is demonstrat~d in section 5.2 that in the event of a potential worst-case failure, the energy of the flywheel heavy metal inserts is contained by the casing, thermal barrier, stator closure, and stator lower flange.
4.2.1 American Society of Mechanical Engineers Code The Level A stress limits of the ASME Code, Section Ill, Subsection NG (Reference 4) are used as evaluation criteria for the components of the flywheel assembly. Subsection NG rules and limits apply to reactor core support structures. The use of core support limits is considered appropriate for the flywheel assembly components since both the core supports and flywheel assembly operate in the reactor water environment and neither is a reactor coolant pressure boundary. An additional acceptance criterion is a limit of Sy for the primary plus secondary membrane plus bending stress intensities in the main shrink-fit areas. This ensures that the flywheel will remain elastic in these areas and prevent a loss of shrink fit due to tensile yielding.
4.2.2 Regulatory Guide 1.14 The application of the guidance of Regulatory Guide 1.14 for the analysis of the flywheel is addressed in the AP1000 DCD (Reference 3). As outlined in the DCD, the flywheel assembly is evaluated for three critical flywheel failure modes. This report demonstrates that the failure modes of ductile fracture, non-ductile fracture, and excessive deformation will not occur at the design speed (125-percent normal speed). The design speed envelopes all expected and postulated overspeed conditions, including overspeeds due to postulated pipe ruptures.
The analysis performed to evaluate the failure by ductile fracture uses the failed stress limits in Appendix F of Section II I of the ASME Code as acceptance criteria.
Page 4-2 AP 1 OOORCP-06-009-N P
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 15 of29 The enclosure is evaluated at normal operating and design speeds using the ASME Code, Section Ill, Subsection NG limits. The enclosure components of the flywheel assembly (Alloy 625 end plates and thin outer shell) are not evaluated for critical failure speed. The function of the enclosure is to prevent contact of reactor coolant with the heavy metal inserts and outer retainer cylinder of the flywheel assembly. No credit is taken in the evaluation of missiles from a postulated flywheel fracture for the containment of fragments by the enclosure components. In addition, the enclosure components contribute only a small portion of the total energy in the rotating assembly.
The analysis performed to evaluate the potential for nonductile fracture of the outer retainer cylinder (18Cr-18Mn Alloy steel) considers the estimate of the flaw size, location, and values of fracture toughness assumed for the material. An evaluation of nonductile fracture for the outer retainer cylinder, summarized in section 5.1, determines critical flaw size.
Failure by excessive deformation is defined as any deformation, such as enlargement of the bore, which could cause separation directly or could cause an unbalance of the flywheel. The evaluation of excessive deformation verifies that the components of the flywheel assembly remain in contact at the design speed.
4.2.3 Standard Review Plan The heavy metal alloy flywheel is evaluated using the stress limits given in paragraphs 4.a and 4.c of the Standard Review Plan, subsection 5.4.1.1 (Reference 5) for normal and design speed. Paragraph 4.a recommends that at normal operating speed, the combined stresses due to centrifugal forces and interference fits should not exceed 1/3 of the minimum yield strength.
Paragraph 4.c recommends that at design overspeed (125 percent of normal speed), the combined stresses due to centrifugal forces and interference fit should not exceed 2/3 of the minimum specified yield strength. For the AP1000 flywheel, these stress limits are applied to the primary stress in the flywheel outer retainer cylinder. The Standard Review Plan limits do not apply to the enclosure components.
Page 4-3 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 5.0 ANALYTICAL METHODS AND RESULTS March 5, 2019 Page 16 of 29 This section describes the components involved in the analysis, the methods of analyses for the studies, and the results.
The flywheel scoping calculations focus on determining the component shrink-fit requirements, the outer retainer cylinder primary stress, and the outer retainer cylinder critical flaw size. The AP1000 flywheel location within the thermal barrier/stator closure is similar to the AP600 design.
The AP1000 has a second, shorter flywheel located within the canned motor between the thrust runners within the stator lower flange. In both locations, the basic design concept of the flywheels has been changed to replace the shrunk-fit depleted uranium disks considered in the AP600 design with tungsten heavy metal alloy segments that are held against a Type 403 stainless steel inner hub by an 18Cr-18Mn Alloy Steel outer retainer cylinder. The AP1000 flywheel has the same primary stress limits as those defined for the AP600. The heavy metal alloy and outer retainer cylinder are sealed from the reactor coolant by an enclosure (inner hub, end plates, and outer thin shell) that also must satisfy the stress requirements of Subsection NG of the ASME Code, Section Ill.
The missile penetration calculations evaluate the capacity of the pressure boundary structures to absorb the energy of the heavy metal inserts. The missiles are not to penetrate the pressure boundary wall, so containment is preserved. This AP1000 study uses the same missile containment calculation procedure as AP600.
5.1 FLYWHEEL CALCULATIONS The flywheel primary stress analyses are performed by hand calculations assuming that the assembly consists of a cylindrically shaped set of heavy metal inserts held against a Type 403 stainless steel inner hub by an 18Cr-18Mn Alloy Steel outer retainer cylinder in an enclosure and shrunk onto the shaft (Figures 5-1 and 3-1). Using simplified methods, normal operating speed (1800 rpm) at steady-state operating temperature (400°F) and design overspeed (2250 rpm) at steady-state design temperature (550°F) of the motor cavity flywheel are investigated.
The analyses conservatively neglect the effects of system pressure. The results of these analyses are summarized as follows:
Page 5-1 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 17 of 29 The calculated primary stresses in the outer retainer cylinder due to pump rotation are:
50.9 ksi for normal speed (1800 rpm) 79.5 ksi for design speed (2250 rp,m)
These calculated stresses are less than the allowable stress limits for 18Cr-18Mn Alloy Steel (ASTM A-289, Grade 8).
Based on a material yield stress of 157.0 ksi at 400°F, the normal condition primary stress limit is Sy/3 = 52.3 ksi.
Based on a material yield stress of 150.0 ksi at 550°F the design condition primary stress limit is 2Sy/3 = 100.0 ksi.
A preliminary fracture mechanics evaluation of the AP1000 outer retainer cylinder for sudden rupture indicates that for the maximum hoop stress at the cylinder inside surface, which occurs for assembly plus 125-percent overspeed, the critical flaw size is 0.290 inches deep with a surface length of 0.870 inches. This flaw size compares favorably with ultrasonic inspection capability.
5.1.1 Analytical Model The calculations for the AP1000 motor cavity flywheel assembly are performed via hand calculations considering a series of concentric rings shrunk fit together to make the assembly.
These rings and pertinent geometrical properties for both flywheels are illustrated in Figure 5-1.
The only difference in the two flywheels is the length, which is 15.50 inches for the larger flywheel and 10.50 inches for the smaller flywheel. The enclosure thin shell is illustrated and serves as a sealing membrane but does not contribute structurally except for a vertical seismic event. For the present analysis, the material for the rotor shaft and inner hub are 403 stainless steel (ASTM A336, Grade F6), the heavy metal alloy segments are tungsten heavy alloy (ASTM 8777, Class 4), the outer retainer cylinder is 18Cr-18Mn Alloy Steel (ASTM A-289, Grade 8),
and the enclosure components (end plates and outer thin shell) are nickel-chromium-iron alloy (Alloy 625, ASTM 8443, UNS N06625). The outer retainer cylinder ring is conservatively evaluated for shaft rotations at 1800 and 2250 rpm and steady-state temperatures of 400°F and 550°F respectively while conservatively neglecting the effects of system pressure.
Page 5-2 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 18 of29 The mechanical properties for the flywheel are presented in Table 5-1. The properties for Type 403 stainless steel are taken from ASTM A336, Grade F6 with modified chemistry and property requirements, the Tungsten Heavy Alloy properties are from ASTM B777 and the 18Cr-18Mn Alloy Steel properties are from ASTM A-289, Grade 8 and Reference 12. The properties for Alloy 625 are taken from the ASME Code.
Table 5-1 Mechanical Properties Mean Expansion Yield Strength Coefficient Density Component (ksi)
(in./in.-°F)
(lb/in 3
)
Shaft and Inner Hub (Type 403 stainless 40 5.9x10-6 0.280 steel)
Tungst~n Heavy 75 2.5 X 10-6 PT= 0.67 Alloy Outer Retainer 195 (ci) 70°F Cylinder (18Cr-18Mn 157 @400°F 9.2 X 10-6 PR= 0.278 Alloy Steel) 150 550°F End Plates and Thin Shell 55 6.7 X 10-6 0.305 (Alloy 625)
Page 5-3 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 Shaft 403 SST Ros Outer Retainer Cylinder Enclosur,e Thin Shell Inner Hub 403 SST Heavy Metal Inserts Tungsten Heavy Alloy p1 = the interface pressure between the shaft and the inner hub p2 = the interface pressure between the inner hub and the heavy metal inserts March 5, 2019 Page 19 of 29 p3 = the interface pressure between the heavy metal inserts and the outer retainer cylinder Ros= the shaft outer radius and the inner hub inner radius=
[
]8'b inches R01 = the inner hub outer radius and the heavy metal inner radius =
[
]8'b inches Ror = the heavy metal outer radius and the retainer cylinder inner radius =
[
]a,b inches RoR = the retainer cylinder outer radius and the can inner radius =
[
]8'b inches Roe = the enclosure can outer radius =
[
J8'b inches Figure 5-1 Flywheel Assembly Dimensions Page 5-4 AP1 OOORCP-06-009-NP
Attachmen 2 svP _svo_oo5413 5.1.2 Concentric Ring Model Geometry and Shrink-Fit March 5, 2019 Page 20 of 29 The flywheel assembly will be manufactured by shrink fitting the outer retainer cylinder onto the outside diameter of the heavy metal inserts, which have been fitted to the outside diameter of.
the inner hub, with [
r,b inches of radial interference. Enclosure completion, for the purpose of sealing the heavy metal alloy inserts and 18Cr-18Mn Alloy Steel outer retainer cylinder from the reactor coolant, is accomplished by assembling and welding end plates (Alloy 625) to the inner hub and then assembling and welding the outer thin shell (Alloy 625) to the end plates.
The shaft fit bore of the flywheel inner hub is machined to final size after completing the flywheel fabrication to achieve a [
]a,b inch radial interference on the rotor shaft.
To preclude possible slippage between components that could change the balance of the flywheel, the shrink fit and outer retainer cylinder thickness are sized to maintain a shrink fit at all possible conditions. In addition to the shrink fit, the heavy metal inserts are keyed to the inner hub axially at mid-height and circumferentially at the intersection of each heavy metal insert with pins designed to carry the maximum torque of the motor and seismic loads. The total radial interference of [
]a,b inches in the assembly of the flywheel was selected to maintain an interference fit at the heavy metal insert to inner hub interface under the worst.case with the flywheel at 125-percent overspeed and ambient conditions (zero external pressure and 70°F).
Unlike the uranium insert flywheel design, the enclosure components (end plates and outer thin shell) have a negligible impact on the shrink fit of the outer retainer cylinder on the heavy metal inserts and inner hub and are not relied upon structurally except for a vertical seismic event.
5.1.3 Outer Retainer Cylinder Rotational Primary Stresses Per the AP1000 RCP Design Specification (Reference 7), the design speed of the flywheel is defined as 125% of the normal speed of the motor. At normal speed the calculated maximum primary stresses in the outer retainer cylinder shall be limited to less than 1/3Sy. At the design speed the calculated maximum primary stress in the outer retainer cylinder shall be limited to less than 2/3Sy. The calculations for these primary stresses due to rotation consider only the heavy metal, alloy and outer retainer cylinder portion of the flywheel assembly and do not include any of the stresses due to component shrink fits or the shrink fit of the flywheel assembly onto the shaft.
Page 5-5 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 21 of 29 The maximum primary stress in the outer retainer cylinder, due to the centrifugal forces of the heavy metal inserts and the outer retainer cylinder inertia, is the hoop stress at the inner radius of the outer retainer cylinder. The calculations for the hoop stress are given as follows:
Outer retainer cylinder inner radius hoop stress due to centrifugal acceleration of heavy metal inserts and the outer retainer cylinder Hoop stress in outer retainer cylinder due to centrifugal acceleration of heavy metal inserts Pressure exerted by heavy metal inserts on the outer retainer cylinder Centrifugal acceleration of heavy metal inserts G _a/. 2sin(a) *(R R ~ R0 T
- ROI J m -
OT+
OJ g
3a R0 T +ROI Where g = 386.4 in/sec2 Outer retainer cylinder inner radius hoop stress due to centrifugal acceleration of outer retainer cylinder.
2 cr ero = PR co [(3 + v)RtR + (1-v)RtT]
4g Where v (Poisson's ratio) is conservatively assumed as 0.3 Page 5-6 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 Outer retainer cylinder normal operation inner radius hoop stress CY ee (Ror) R = (42,643.9 psi+ 8,208.8 psi)= 50,852.7 psi CY
= 3,829.6psi x[]°'bin = 42 643.9 si eP
([f'b in-[]a,b in)
P 0.67.1~ *l,292.2*(co 0*bin)2-(D 0*bin) 2
)
Par =
zn b
= 3,829.6 psi 2 *([]a, in)
March 5, 2019 Page 22 of29
(
J 2
188.5 rad G =
s~c
. 2 sin(0.261 &rad). ([]a,b in+ []a,b i~ _ []°'bin* [t°b in ) = l,292_2 386.4~
3*0.26l8rad
[]°*hin+[]°'hin sec2 0.278.1~ (188.5 radJ 2
CYew =
m sec
[(3+0.3)([]°'bin) 2 +(l-0.3)([t*bin) 2 ]=8,208.8psi in 4x386.4--
2 sec Outer retainer cylinder design condition inner radius hoop stress CY88 (Rar)R = (66,631.lpsi + l2,826.3psi) = 79.457.4 psi CY =
5,983.8 psi x []°*bin
= 66 631.1 si ep
([18.l 725] 0 'b in-[]a,b in) p lb 0.67-. -3
- 2,019'. (ma,b in) 2 - (D a,b in) 2 )
Par =
zn b
= 5,983.8psi 2*(0°' in)
(1.25
- 188.5 rad) 2 G =
sec
. 2 sin(0.261 &rad). [ua,b in+ []a,b in- []
0
- b in* []
0
- b in) = 2,019 386.4~
3*0.26l8rad
[]°*bin+[]°*bin sec2 Page 5-7 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 23 of29 0.278 _zh3 (1.25
- 188.5 radr a-em =
m sec
[(3 + 0.3)([t'b in)2 + (1- 0.3)([]a,b in)2] = 12,826.3 psi in 4x386.4--
2 sec The outer retainer cylinder is 18Cr-18Mn Alloy Steel and the yield stress for this material is 157,000 psi at 400°F and 150,000 psi at 550°F. Per the design specification, the 1/3Sy is 52,333 psi at 400°F and 2/3Sy is 100,000 psi at 550°F. For normal operation at a rotational speed of 1800 rpm and a steady-state temperature of 400°F, the maximum primary hoop stress is 50,852.7 psi, which is less than 52,333 psi. Additionally, for a design rotational speed of 2250 rpm and a steady-state temperature of 550°F, the maximum primary hoop stress is 79,457.4 psi, which is less than 100,000 psi. Since the maximum primary stresses due to rotation for the outer retainer cylinder are less than the prescribed allowable stresses, the requirements of the design specification are satisfied.
5.1.4 Concentric Ring Elastic Hoop Stresses In Table 5-2, the hoop stresses at the inner and outer diameter of each of the concentric rings in the model are presented for assembly conditions and 125-percent overspeed at 70°F. From Table 5-2, it is noted that the maximum compressive stresses of 18.3 ksi in the inner hub and 16.9 ksi in the shaft are less than the yield stress for Type 403 stainless steel, which is 40 ksi at 70°F. In addition, the maximum hoop stresses of 127.1 ksi at the inner radius of the outer retainer cylinder is less than the yield stress for 18Cr-18Mn Alloy Steel, which is 195 ksi at 70°F.
Table 5-2 AP1000 Motor Cavity Flywheel Hoop Stresses Shaft Inner Hub Outer Retainer Cylinder Outer Inner Outer Inner Outer Radius Radius Radius Suso Sun Su10 Radius Radius (psi)
(psi)
(psi)
SuR1 (psi)
SuRo(psi)
Assemblv1 ')
-16,867
-17,737
-18,329 121,805 110,990 125-Percent Overspeed at
-4,359
-5,241
-6,609 127,180 116,270 70°F
- 1.
Assembly radial shrink fits:
Flywheel assembly to rotor shaft = [ r,b inches Outer retainer cylinder to Heavy Metal Alloy = [
]8'b inches Page 5-8 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 5.1.5 Flywheel Enclosure Welds March 5, 2019 Page 24 of 29 The flywheel is analyzed using finite elem,ent in order to evaluate its endurance throughout the thermal transients to which they will be subject. The model is a two-dimensional axi-symmetric model where each component of the flywheel (inner hub, heavy metal inserts, outer retainer cylinder, enclosure end plates and enclosure thin shell) is discreetly modeled.
The fatigue results are shown below:
Flywheel Fatigue Results Component Outer Cylinder End Plates Can Can Welds End Plate Welds Hub Shaft Retaining Nut
- Allowable Usage Factor ~1.00 5.1.6 Fracture Mechanics of Outer Retainer Cylinder Usage Factor*
0.193 0.026 0.002 0.171 0.001 0.106 0.121 0.000 An estimate of the critical flaw size in the outer retainer cylinder of the flywheel was made using fracture mechanics technology. The most limiting situation for fracture is for a flaw emanating from the inside surface of the cylinder and subjected to the stresses at the 125% speed condition. This flaw is assumed to be in the radial-axial plane and thus perpendicular to the hoop stress direction, which is the most severe orientation. Further, the flaw is conservatively assumed to have a semi-elliptical shape with a surface length to depth ratio of 6: 1, as in Section XI of the ASME Code, when remote from the cylinder ends. In the present analysis, the flaw is also assumed to be at the most detrimental position along the length of the cylinder, where it becomes a corner flaw with a surface length to depth (length along the other cylinder surface) ratio of 3: 1. The hoop stress at the 125% speed condition at the cylinder inside surface is 144,000 psi including the stress concentration effect of the gap between the heavy metal Page 5-9 AP1 OOORCP-06-009-NP
Attachmen 2 svP _svo_oo5413 March 5, 2019 Page 25 of 29 inserts. This stress was assumed to be uniform across the cylinder wall. Values of K1 (mode I plane strain stress intensity factor) were computed as a function of crack depth with the NASCRAC fracture mechanics software (NASA Crack Analysis Code, Version 3, Failure Analysis Associates, Menlo Park, California). The room temperature fracture toughness (KIC) of the 18Cr-18Mn Alloy Steel material was taken as 136,000 psi-in112,which is the lower bound value in Reference 12 at a conservatively assumed yield strength of 210,000 psi, 15,000 psi above the minimum specified. The critical flaw size was for a corner flaw having a depth of 0.290 inches and surface length of 0.870 inches. A flaw of this size is detectable with ultrasonic inspection techniques and can be used to support fracture toughness and inspection requirements for the 18Cr-18Mn Alloy Steel outer retainer cylinder.
Page 5-10 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 5.2 MISSILE PENETRATION March 5, 2019 Page 26 of29 This analysis (reference 11) follows the same procedure used for turbine disk fractures in Reference 1 O and previous analysis (references 8 and 9) for the depleted uranium flywheel.
Although no significant flaws are expected in the 18Cr-18Mn Alloy Steel outer cylinder of the flywheels that completely contain the twelve (12) heavy metal blocks, this analysis assumed a fracture of the 18Cr-18Mn Alloy Steel outer cylinder has occurred and shows that the energy of the fragments is insufficient to penetrate the pressure boundary. No other effects of a flywheel failure were considered in this evaluation.
5.2.1 Assumptions The method of analysis of Reference 10, which was developed from scale tests of turbine disks, is considered applicable herein with the following conservative assumptions used.
The outer 18Cr-18Mn Alloy Steel retainer cylinder and outer thin shell of the flywheel were neglected. In reality the outer retainer cylinder and outer thin shell would need to be breached in the unlikely event of an outer retainer cylinder fracture before the pressure boundary being impacted by the heavy metal alloy. This analysis completely ignored the 18Cr-18Mn Alloy Steel outer retainer cylinder and outer thin shell components.
The Alloy 625 end plates/welds and the surrounding water were also neglected from the energy absorption calculations.
The minimum ASME material strength properties at temperature were used for the pressure boundary (containment closure). The pressure boundary material is taken to be CF8 or F304 SS at a design temperature conservatively estimated to be 550°F.
All heavy metal segments were considered to impact the pressure boundary.
No secondary effects of the shrink fit of the flywheel assembly were considered.
The shell containment in line with the flywheel heavy metal segments Wal? the only containment material considered. For the lower flywheel, the thinner shell section Page 5-11 AP1 OOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413 March 5, 2019 Page 27 of29 above the flywheel was conservatively used rather than the thicker section adjacent to the flywheel.
The design speed of 125 percent times the operating speed of 1800 rpm was used.
5.2.2 Energy Analysis The containment of disk fragments by a cylinder shell is a two-stage process, per Reference 10.
The first stage involves inelastic impact and transfer of momentum to the containment cylinder.
If the energy dissipated in plastic compression and shear strain is sufficient to accommodate the loss of kinetic energy of the flywheel, there is no shear perforation of the shell. The process th~n enters Stage 2, which involves dissipation of energy in plastic tensile strain in the shell.
For containment, the energy dissipated in plastic tensile strain must accommodate the residual kinetic energy of the flywheel. Note the procedure has experimental verification of the analytical techniques (Reference 10). The kinetic energy of a fragment is:
t MV 2
, where M = mass of fragment and V = fragment velocity after rupture Fragment rotational considerations can be neglected per Reference 10. The flywheel heavy metal alloy is assembled into a cylindrical ring using individual wedge shaped segments arranged in keystone fashion and retained against the inner hub by the outer retainer cylinder.
Therefore, in the unlikely event of a fracture in the outer retainer cylinder of the flywheel assembly, it has been conservatively assumed that all individual heavy metal alloy segments simultaneously strike the pressure boundary.
Two cases of the containment shell model are considered. Case A, for the upper flywheel, is conservatively assumed to be through the thermal barrier material and the adjacent stator closure. Case 8, for the lower flywheel, is through the stator lower flange. The analysis model gives the containment thickness of the two cases in Table 5-3.
Table 5-3 Pump Containment Thicknesses Analyzed in Missile Analysis Case Inner Radius Outer Radius Thickness A - Upper (larger) 18.775" 25.23" 6.455" Flywheel B - Lower (smaller) 20.505" 27.735" 7.23" Flywheel Page5-12 AP1 OOORCP-06-009-NP
Attachmen 2 svP _svo_oo5413 5.2.3 Missile Containment Analysis Results March 5, 2019 Page 28 of 29 The pressure boundary sections contain the kinetic energy of all heavy metal alloy segments simultaneously. The verified semi-empirical method of Reference 1 O shows that any improbable flywheel fracture would not penetrate the thermal barrier/stator closure walls that surround the upper larger flywheel assembly nor the stator lower flange closure walls that surround the smaller lower flywheel.
The following Table 5-4 compares the heavy metal energy to the energy available for the Stage 1 (shear) penetration and for the Stage 2 (tensile) penetration. The ratio of the two gives the third column of results that is presented as margin.
5.2.4. Conclusion The analysis shows that even in the unlikely event of the flywheel failure, any loose parts (missiles) will be contained within the primary pressure boundary.
Table 5-4 Pressure Boundary Capacity for Missile Containment Fragment Energy Required for Energy Penetration Case (in-lb)
(Boundary Capacity) (in-lb)
Margin Main Flywheel - Stage 1 36,550,000 250,850,000 6.9
- Stage 2 52,496,000 102,390,000 2.0
- Total 89,046,000 353,240,000 4.0 Lower Flywheel - Stage 1 31,580,000 323,810,000 10.3
- Stage 2 28,760,000 88,880,000 3.1
- Total 60,340,000 412,690,000 6.8 Page 5-13 AP1 dOORCP-06-009-NP
Attachmen 2 SVP _SV0_005413
6.0 REFERENCES
March 5, 2019 Page 29 of 29
- 1. APP-MP01-V2-001, Rev. 3; APP-MP01-V2-002, Rev. 2 and APP-MP01-V2-003 thru 008, Rev. 1, "AP1000 Reactor Coolant Pump - Outline."
- 2. WCAP-13734, "Structural Analysis Summary for the AP600 Reactor Coolant Pump High Inertia Flywheel." May 1993.
- 3. APP-GW-GL-700, "AP1000 Design Control Document," subsection 5.4.1.
- 4. ASME Boiler and Pressure Vessel Code, Section Ill, Subsection NG and Appendices, 1998 Edition, American Society of Mechanical Engineers, New York, N.Y.
- 5. NUREG-0800, "Standard Review Plan," Revision 1, Section 5.4.1.1, U.S. Nuclear Regulatory Commission, Office of Nuclear Regulation, Washington, D.C., July 1981.
- 6. Regulatory Guide 1.14, Revision 1, "Reactor Coolant Pump Flywheel Integrity," U.S.
Nuclear Regulatory Commission, Office of Standard Development, Washington, D.C.,
August 1975.
- 7. APP-MP01-M2-001,Rev. 1, "AP1000 RCP Design Specification"
- 8. Dietrich, D. E., "AP1000 RCP Concept Design Flywheel Scoping, Missile Containment, and Rotor Critical Speed Calculations,", Westinghouse Government Services Company LLC, Electro-Mechanical Division, Analytical Technologies Letter AT/S-02-17, Revision 1, May 21, 2002.
- 9. Brose, W. R. and Dietrich, D. E., "Updated Analysis of Missile Containment for AP1000 RCP Concept Design Flywheel," Curtiss-Wright Electro-Mechanical Corporation, Analytical Technologies Letter AT/S-02-40, November 21, 2002.
- 10. Hagg, A. C., and Sankey, G. 0., "The Containment of Disk Burst Fragments by Cylindrical Shells," ASME Paper 73-WA-Pwr-2, 11/73; also in ASME Journal of Engineering for Power, 4/74, pg. 114-123.
- 11. Casamassa, J. and Brose, W.R., "Pressure Boundary Containment of a Burst Tungsten Flywheel", Curtiss-Wright Electro-Mechanical Corporation, Analytical Technologies Letter ET/S-06-31, Rev. 3, May 11, 2009.
- 12. Orita, K. et al "Development and Production of 18Mn - 18Cr Non-Magnetic Retaining Ring with High Yield Strength," ISIJ International, Vol. 30 (1990), No. 8, pp. 587-593.
- The information reveals the distinguishing aspects of a process or component, structure, tool, method, etc., and the prevention of its use by competitors of Curtiss-Wright Electro-Mechanical Corporation, without license from Curtiss-Wright Electro-Mechanical Corporation, gives Curtiss-Wright Electro-Mechanical Corporation a competitive economic advantage.
b The information, if used by a competitor, would reduce the competitor's expenditure ofresources or improve the competitor's advantage in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product.
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