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WCAP-17311-NP, Revision 1, Structural Analysis Report for STP Units 3 & 4 New Fuel Storage Rack Baseline Design, Attachment 1 to U7-C-STP-NRC-100260
ML103490741
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Site: 05200012, 05200013
Issue date: 12/31/2010
From: Albert B, Dee A
Westinghouse
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Office of New Reactors
References
U7-C-STP-NRC-100260, STI 32796076, +reviewedgfw WCAP-17311-NP, Rev 1
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U7-C-STP-NRC-100260 Westinghouse Non-Proprietary Class 3 WCAP-17311-NP December 201 Revision 1 Structural Analysis Report for STP Units 3 & 4 New Fuel Storage Rack Baseline Design Westinghouse 0

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 WCAP-17311-NP Revision 1 Structural Analysis Report for STP Units 3 & 4 New Fuel Storage Rack Baseline Design Authors:

Allison L. Dee*

Major Reactor Component Design and Analysis I Brian M. Albert*

Mechanical/Civil Design & Analysis I December 2010 Reviewer:

Byounghoan Choi*

Major Reactor Component Design and Analysis I Charles A. Mance*

Mechanical/Civil Design & Analysis II Approved:

Carl Gimbrone*, Manager Major Reactor Component Design and Analysis I

  • Electronically approved records are authenticated in the electronic document management system.

Westinghouse Electric Company LLC 1000 Westinghouse Drive Cranberry Township, PA 16066

© 2010 Westinghouse Electric Company LLC All Rights Reserved

U7-C-STP-NRC-100260 WESUNGHOUSE NON-PROPRIETARY CLASS 3 TABLE OF CONTENTS I

IN TRO D UCTIO N.......................................................................................

1-1 2

TECH N ICA L BA CK G RO UN D............................................................................

2-1 3

D ESIGN................................................................................................

3-1 4

M ETH OD O LO GY.......................................................................................

4-1 4.1 A CCELER ATIO N RESPON SE SPECTRA...........................................................

4-1 4.2 M O D ELIN G M ETH O D O LO G Y....................................................................

4-1 4.2.1 G eneral Considerations...................................................................

4-1 4.2.2 SpeciPic M odeling D etails for a Single Rack.................................................

4-1 4.2.3 Sim ulation and Solution M ethodology......................................................

4-4 4.2.4 Conservatism s Inherent in M ethodology.....................................................

4-4 4.3 KINEMATIC AND STRESS ACCEPTANCE CRITERIA.............................................

4-5 4.3.1 Introduction.............................................................................

4-5 4.3.2 K inem atic Criteria.......................................................................

4-5 4.3.3 Stress Lim it Criteria:......................................................................

4-5 4.3.4 Stress Limits for Various Conditions per ASME Code....................................

4-6 4.4 A SSUM PTION S..................................................................................

4-6 5

IN PU T D ATA...........................................................................................

5-1 5.1 RA CK D ATA....................................................................................

5-1 5.2 M ATERIA L D ATA................................................................................

5-1 6

CO M PU TER CO D ES....................................................................................

6-1 7

AN A LY SES.............................................................................................

7-1 7.1 A CCEPTA N CE CRITER IA........................................................................

7.-1 8

RESU LTS O F A N A LY SES................................................................................

8-1 8.1 IM PA CT LO AD S.................................................................................

8-1 8.1.1 Fuel-to-Cell W all Im pact Loads............................................................

8-1 8.2 RA CK STRU CTU R AL EVA LU ATIO N.............................................................

8-2 8.2.1 Cell W all Stresses........................................................................

8-2 8.2;2 W eld Stresses............................................................................

8-3 8.2.3 Leveling Screw Evaluation................................................................

8-5 8.3 DROPPED FUEL ASSEMBLY EVALUATION.......................................................

8-5 8.3.1 D rop O rientations........................................................................

8-6 8.3.2 D rop Locations..........................................................................

8-10 8.3.3 D ropped Fuel A ssem bly A nalysis Results...................................................

84 0 8.4 STU CK FU EL A SSEM BLY EVA LU ATION.........................................................

8-11 9

CON CLU SION S........................................................................................

9-1 10 REFEREN CES.....................

10-1 WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 1-1 INTRODUCTION This report documents the structural analyses of the baseline new fuel storage rack design for South Texas Project Units 3 & 4 (STP 3 & 4). Revision 1 includes supplemental information added as a result of the U.S. Nuclear Regulatory Commission (NRC) Requests for Additional Information (RAI). The racks are designed to store new fuel assemblies in the new fuel vault, which is located near the refueling floor elevation of the plant. The vault is designed to hold four stainless steel storage racks, which are made up of uniformly-sized storage cells. The racks are each 1 Ox 10 arrays capable of storing up to 100 fuel assemblies. The bases for the analyses are the design requirements specified by the COLA in Part 2, Tier 2, Section 9.1, Revision 4 [1] and Tier 2, Appendix 3A, Revision 4 of the DCD [2]. As Revision 1 of this WCAP is a complete re-write, change bars have not been used. Revision 1 is the original issue of the non-proprietary (NP) version of this WCAP.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-1 2

TECHNICAL BACKGROUND This report demonstrates the structural adequacy of the proposed STP 3 & 4 new fuel storage racks under postulated loading conditions. Analyses and evaluations follow the NRC Standard Review Plan 3.8.4, Revision 2 [5]. The analysis uses a finite element modeling code that was used in previous fuel rack licensing efforts. This report discusses the method of analyses, modeling assumptions, key evaluations, and results obtained to establish that the new fuel rack meets all structural integrity requirements.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-1 3

DESIGN The layout of the new fuel storage racks in the new fuel vault is shown in Figure 3-1. The capacity of the vault is four 10xl0 racks, with a total capacity of 400 new fuel assemblies. The storage racks are composed of individual storage cells made of [

c thick austenitic stainless steel sheets. For this analysis, the cells have a center-to-center cell pitch of

] a 'and an inside dimension of [

I". The storage cells are 190 inches tall. They are welded to a base support assembly and to one another to form an integral structure.

The base support assembly consists of a 1.5-inch thick stainless steel baseplate that is supported by leveling block assemblies. The stainless steel leveling block assemblies allow the height of the support feet to be adjusted to level the rack during installation. The top of the baseplate is located 8.1 inches above the new fuel vault floor.

The neutron absorbing material Borall is attached along the length of the cell walls through the use of thin gauge stainless steel wrapper plates. The wrapper plates are formed to create a small cavity. Then they are welded to the cell walls. Next, the Boral plates are inserted into the cavity formed between the wrapper plates and the cell walls. The Boral plates are [

I a, c thick and completely cover the active fuel region of the fuel. The tops of the Boral plates are located I

] a c below the top of the cells. Geometric details of the racks are shown in Figure 3-2 and Figure 3-3. An overview of the construction and materials used in the STP 3 & 4 new fuel storage rack is presented in Table 3-1 through Table 3-3.

The new fuel racks are anchored to the floor of the new fuel vault at each support foot location.

The new fuel racks incorporate support bands at three elevations to transmit lateral loads between racks and from the racks to the new fuel vault walls. The locations of the floor anchors are shown in Figure 3-4; the elevations of the support bands are shown in Figure 3-5. The design and qualification of the floor anchors and support bands will be completed later as part of the detailed design.

'BORAL is a registered trademark of Ceradyne Inc. in the United States or other countries. All other brand, product, service and feature names or trademarks are the property of their respective owners.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-2 a,c Figure 3-1: New Fuel Vault Layout WCAP-1731 1-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-3 a.c Figure 3-2: Rack Geometry WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-4 a.c Figure 3-3: Rack Geometry WCAP-17311-NP December 2010 Revision 1I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-5 X=LOATIN OFSUPORT EETSUPPRTSTHAT TRANSFER LOADS x=LcATIN OF SUPPORT-FEET BETWEEN ADJACENT RACKS AND ANCHORED TO THE VAULT; FLOOR TRANSFER LOADS FROM THE RACKS TO THE VAULT WALLS "C7 \\ý7 \\ý7 "ý7 "ý7 "ý7 7 7

VVVVVV

  • 3DDDDF3EF1DDD-Z-DDDDDDDDDD*IIII LII I IDEZiiZ]ID*DI2F DDDDDDDDDDI**F-III DDDDI I IX*zDDIDDF DD-177DD
  • F]DDDD DDDDDDDDDDIZNI-I-DDI-EI DDDDFll-ID--

DDDHi__/_I_!

  • DDDD K

K K

K K

K ZN ZN ZN ZN ZN ZN ZN ZN ZN ZN Figure 3-4: Locations of Rack Support Feet and Floor Anchors WCAP-1731 1-NP December 2010 Revision 1

U7-C-STP-NRC-100260 3-6 WESTINGHOUSE NON-PROPRIETARY CLASS 3 167.5" ABOVE THE FLOOR 159.8" ABOVE THE FLOOR 99.9" ABOVE THE FLOOR 91.1" ABOVE THE FLOOR 47.5" ABOVE THE FLOOR 38.8" ABOVE THE FLOOR SUPPORT BAND SUPPORT BAND SUPPORT BAND Ii L

VAULT FLOOR Figure 3-5: Elevations of Rack Support Bands WCAP-1731 1-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-7 Table 3-1: STP 3 & 4 New Fuel Storage Rack Storage Cell Description a.c i

Table 3-2: STP 3 & 4 New Fuel Storage Rack Module and Fuel Data a.c

[

4

.4 Table 3-3: Material Data (ASME - Section II)

Young's Modulus Yield Strength Ultimate Strength Material E

Sy Su (ksi)

(ksi)

(ksi)

Rack Material Data (70'F)

SA-240, Type 304L 28.3x10 3 25.0 70.0 SA-564, Te e630 28.3x10' 115.0 140.0 WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-1 4

METHODOLOGY 4.1 ACCELERATION RESPONSE SPECTRA Seismic acceleration response spectra for the horizontal and vertical directions are provided in DCD Tier 2, Appendix 3A, Revision 4 [2] for use in the seismic analysis of the new fuel rack, in accordance with Regulatory Guide 1.60 [11]. For the safe shutdown earthquake (SSE) analysis, 4% damping was used, in accordance with Regulatory Guide 1.61 [12].

4.2 MODELING METHODOLOGY 4.2.1 General Considerations A finite element representation of the new fuel rack module was developed. Reliable assessment of the stress field and kinematic behavior of the rack module requires a conservative model incorporating all key attributes of the actual structure. This means that the model must possess the capability to effect momentum transfers that occur due to the rattling of fuel assemblies inside storage cells. Since the new fuel storage rack is not placed in water, there is no contribution from water mass in the interstitial spaces around the rack model and within the storage cells. Because the new fuel rack is anchored to the vault floor and has supports at three elevations, it is only necessary to evaluate a fully loaded storage rack, not partially loaded cases.

4.2.2 Specific Modeling Details for a Single Rack The rack analysis is performed using a three-dimensional finite element model created in ANSYS1 and shown in Figure 4-1. The rack cellular structure is modeled by shell elements; the fuel consists of a beam model. The lateral supports are modeled by restraining the nodes at the support locations in their respective lateral degrees of freedom. The bottoms of the support feet are restrained in all degrees of freedom to represent the bolted connection between the new fuel rack and the vault floor.

The fuel is represented with a beam model located at the centers of each of the 100 cells. The beam model is generated in [

I The fuel is connected to the cell walls by gap elements. Each fuel assembly is connected to the center of each of the four walls of its respective cell at 13 different elevations, including the top and bottom of the fuel. This is shown in Figure 4-2 and Figure 4-3. The bottom of the fuel is also coupled vertically to the baseplate.

'ANSYS, ANSYS Workbench, Ansoft, AUTODYN, CFX, EKM, Engineering Knowledge Manager, FLUENT, HFSS and any and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are trademarks or registered trademarks of ANSYS, Inc. or its subsidiaries located in the United States or other countries. ICEM CFD is a trademark used by ANSYS, Inc. under license. CFX is a trademark of Sony Corporation in Japan. All other brand, product, service and feature names or trademarks are the property of their respective owners.

WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-2 I

IKLEHEWS AN 10:09 2010 10:06:20 Figure 4-1: ANSYS Fuel Rack Model Isometric View WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-3

_P

IRE, P

P N

~E~Jd Shell Element (Cell Wall)

Gap Element Pipe Element w

Fuel Beam i

Figure 4-2: Fuel-to-Cell Connection Shell Element (Cell Wall)

Pipe Element Gap Element Fuel Beam Figure 4-3: Schematic Diagram of Finite Element Model WCAP-173 1 1-NP December 2010 WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-4 4.2.3 Simulation and Solution Methodology Since the analytical work effort must address stress criteria, the sequence of model development and analysis steps that are undertaken are:

a. Prepare a three-dimensional finite element model of the new fuel storage rack.
b. Perform analyses and archive results for post-processing appropriate load outputs from the model.
c.

Perform a stress analysis of high stress areas. Demonstrate compliance with American Society for Mechanical Engineers (ASME) Code Section III, Subsection NF [8] limits on stress, as amended by the requirements of Paragraphs c. 2, 3, and 4 of Regulatory Guide 1.124 [10].

The fuel rack was loaded by static accelerations using the equivalent static analysis method to account for the seismic forces acting on the structure. The accelerations' magnitudes were taken from the spectra provided in DCD Tier 2, Appendix 3A, Revision 4 [2]. To determine the response of the rack due to seismic input, the peak spectral accelerations are taken from the horizontal and vertical acceleration response spectra and are multiplied by a factor of 1.5 (according to the static coefficient methodology in IEEE Standard 344-1975 [9]). Then, these accelerations are simultaneously applied to the fuel rack model. In general, for a simple structure like the new fuel rack, the equivalent static analysis method provides conservative results, as compared to other dynamic analysis methods. Therefore, it is an acceptable analytical approach to evaluate the new fuel storage racks. Use of IEEE Standard 344-1975 [9] is in accordance with Regulatory Guide 1.100 [13] and Standard Review Plan 3.7.2, pages 3.7.2 through 3.7.7 [5]. In addition to the static seismic accelerations, the fuel rack was also loaded by static fuel impact loads that were calculated in accordance with Appendix D of Standard Review Plan Section 3.8.4

[5] as shown in Section 8.1.1. Stresses in the racks were checked against ASME design limits, as amended by the requirements of Paragraphs c. 2, 3, and 4 of Regulatory Guide 1.124 [10] to ensure structural adequacy of the design. Details of the seismic analysis and stress qualifications are provided in [

]a,c 4.2.4 Conservatisms Inherent in Methodology The following items are built-in conservatisms:

" All fuel is assumed to move as a unit, thus maximizing rack response.

" The equivalent static analysis (static coefficient methodology), as described in IEEE Standard 344-1975 [9], leads to more conservative results than a dynamic analysis.

WCAP-17311 -NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-5 4.3 KINEMATIC AND STRESS ACCEPTANCE CRITERIA 4.3.1 Introduction The STP 3 & 4 new fuel storage rack is designed as seismic Category 1. The U.S. NRC Standard Review Plan 3.8.4 [5] states that the ASME Code Section 111, Subsection NF [8], as applicable for Class 3 Components and as amended by the requirements of Paragraphs c. 2, 3, and 4 of Regulatory Guide 1. 124 [10], is an appropriate vehicle for design. In the following subsections, the ASME limits are set down.

4.3.2 Kinematic Criteria The new fuel storage rack should not exhibit rotations to cause the rack to overturn (i.e., ensure that the rack does not slide off the bearing pads, or exhibit a rotation sufficient to, bring the center of mass over the comer pedestal). This requirement is fulfilled by the fact that the new fuel storage rack is laterally supported by the vault walls at three elevations and anchored to the floor of the vault.

4.3.3 Stress Limit Criteria For thoroughness, the Standard Review Plan Section 3.8.4 [51 load combinations were used, accounting for the amendments as required by Paragraphs c. 2, 3, and 4 of Regulatory Guide 1.124 [101; see [5, Note 3]. Stress limits must not be exceeded under the required load combinations.

The fuel storage racks were evaluated for the load conditions specified in Table 4-1. As stated in Section 4.4, there is no temperature differential in the new fuel rack due to heat from the fuel.

Therefore, thermal loads are insignificant and are not included in the stress combinations.

Operating basis earthquake (OBE) is not a design basis for STP 3 & 4. Also, as described in the COLA Part 2, Tier 2, Section 9. 1, Revision 4 [ I ] and as stated in Section 8.4, the stuck fuel assembly load combination does not need to be considered for STP 3 & 4.

WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-6 Table 4-1: Loading Combinations for STP 3 & 4 New Fuel Storage Rack Loading Combination Service Level D+L D + L + To Level A (Note 2)

D + L + To +E D + L + Ta + E Level B (Note 1, Note 2)

D + L + To +Pf D + L + Ta +E' Level D (Note 2)

D + L + Fd Functional Capacity According to Standard Review Plan 3.8.4 [5]

Notes:

1.There is no OBE for the STP 3 & 4 plant.

2. The new fuel rack is not subject to the effects of thermal loads (see Section 4.3.4)

D

=

deadweight-induced loads (including fuel assembly weight)

L

=

live load (not applicable to fuel racks since there are no moving objects in the rack load path)

E

=

OBE E'

=

safe shutdown earthquake (SSE)

T0

=

differential temperature-induced loads based on the most critical transient or steady-state condition under normal operation or shutdown conditions Ta

=

differential temperature-induced loads based on the postulated abnormal design conditions Pf

=

upward force on the rack caused by postulated stuck fuel assembly Fd

=

force due to dropped fuel assembly 4.3.4 Stress Limits for Various Conditions per ASME Code Stress limits for normal conditions are derived from ASME Code,Section III, Subsection NF [8],

as amended by the requirements of Paragraphs c. 2, 3, and 4 of Regulatory Guide 1.124 [ 10].

Parameters and terminology are in accordance with the ASME Code. Material properties for the analysis and stress evaluation are provided in Table 3-3.

4.4 ASSUMPTIONS

" It is assumed that the new fuel vault walls are rigid and that the seismic accelerations do not vary along the elevation of the vault walls.

For the purpose of this analysis, the racks' support bands are assumed to behave rigidly with the vault walls. The detailed design of the support bands will incorporate this behavior.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-7 The structural effects of the neutron-absorbing material and wrapper are considered insignificant, and only their mass effects are included in the rack model.

It is conservatively assumed that all of the fuel impact force will be taken by the cell walls at the elevation of the top of the fuel. This leads to a maximum local impact effect by concentrating all of the load at one elevation.

The stresses in the new fuel racks due to operating thermal loads (TO) and accident thermal loads (Ta) are insignificant. The changes in temperature from the installed temperature of the rack to T. and Ta are minor, and the racks area free to expand/contract with the vault.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 5-1 5

INPUT DATA 5.1 RACK DATA Section 3 contains information regarding the STP 3 & 4 new fuel storage rack module and fuel data that was used in the analysis.

5.2 MATERIAL DATA The necessary material data is shown in Table 3-3. This information is taken from ASME Code Section II [8]. The values listed in Table 3-3 correspond to a temperature of 70'F, which is appropriate since new fuel does not release heat.

WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 6-1 6

COMPUTER CODES Computer codes used in this analysis are presented in Table 6-1.

Table 6-1: Computer Codes Used for Analysis Code Version Description ANSYS [14]

11.0 General purpose commercial finite element analysis code.

LS-DYNA3 971 LS-DYNA is an industry accepted explicit dynamic finite element analysis computer code. LS-DYNA has the capability to solve the finite element model generated using ANSYS in this calculation. The verification problems performed by Westinghouse when the code is configured support the use of ANSYS for this purpose.

3 LS-DYNA and LS-PREPOST are registered trademarks of Livermore Software Technology Corporation.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 7-1 7

ANALYSES 7.1 ACCEPTANCE CRITERIA The stress interaction ratios must be less than 1.0. Additionally, welds and base metal stresses must remain below the allowable stress limits corresponding to the material and load conditions, as discussed in greater detail in following sections.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-1 8

RESULTS OF ANALYSES The following subsections contain the results for the STP 3 & 4 new fuel storage rack under the new fuel floor response spectra.

8.1 IMPACT LOADS Impact loads are discussed below. Due to the design and construction of the STP 3 & 4 new fuel storage rack (fuel assemblies are separated by a cell wall and an air gap), fuel-to-fuel impacts are unable to occur.

8.1.1 Fuel-to-Cell Wall Impact Loads The most significant load on the fuel assembly arises from rattling during the seismic event. The magnitude of the fuel impact force is calculated by pinning both ends of the fuel beam model in the x, y, and z degrees of freedom. The kinetic energy of the fuel due to the effect of seismic is calculated according to the following equation:

KE = 0.5mv 2

a 0)

In the preceding equation:

m= mass of fuel=[

]a, c a = spectra acceleration at the natural frequency of the fuel = [

a, co= natural frequency of fuel multiplied by 2n = [

] a, c The natural frequency of the fuel is [

a, c, as stated in [

a, c Using the preceding equation, the total kinetic energy to be absorbed is [

a,. A uniform acceleration of 4.3g was applied to the fuel, resulting in a total strain energy of [

] a, c. The impact load at the top is equivalent to the resulting reaction load at the top of the fuel beam under this acceleration condition. Using this methodology, the fuel impact load was calculated to be [

] a, c.

As shown in [

] a, c, the first mode dominates the response of the fuel. As a result, the fundamental frequency and mode shape were used to calculate the impact load of the fuel. Finally, this impact load is applied to the rack full model as a pressure equivalent to the impact load divided over the elements where the top of the fuel impacts the sides of the rack.

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-2 8.1.2 Rack-to-Wall Impacts Because the new fuel storage rack has lateral supports at three elevations connecting the racks to the vault wall, rack-to-wall impacts will not occur.

8.2, RACK STRUCTURAL EVALUATION 8.2.1 Cell Wall Stresses The summary of the stress interaction ratios for the cell walls is provided in Table 8-1. All new fuel rack interaction ratios are less than the required limit of 1.0 for the governing faulted condition examined. The most heavily stressed section in the rack structure satisfies the interaction ratio criteria, ensuring that the overall structural criteria are met. Therefore, the STP 3

& 4 new fuel storage rack is able to maintain its structural integrity under the worst loading conditions.

Allowable cell wall stresses are calculated as:

A. Material:

B. Physical Properties:

C. Allowable Stress:

D. Stress Limits:

ASME SA-240, Type 304L Sy = 25.0 ksi at ambient Su = 70.0 ksi at ambient E = 28,300 ksi at ambient S = 15.7 ksi at ambient a(1 _ 1.0(S)(SLF) a 1 + a2 < 1.5(S)(SLF) a1 = membrane stress a2 = bending stress SLF = stress limit factor Level A= 1.0 Level D = Appendix F The Level D stress limits for a plate-type analysis, a shell-type analysis, and a primary membrane stress are taken from ASME Code,Section III [8, Table NF-3552(b)-l and Appendix F, F-1332],

as amended by the requirements of Paragraphs c. 2, 3, and 4 of Regulatory Guide 1.124 [10].

The greater of 1.2(Sy) = 1.2(25.0 ksi) = 30 ksi or 1.5(Sm) = 1.5(16:7 ksi) = 25.05 ksi.

Not to exceed 0.7(Su) = 0.7(70 ksi) = 49 ksi... This result is acceptable.

In the preceding equations, Sm = 16.7 ksi at ambient.

The primary membrane plus bending is 1.5(membrane) = 1.5(30) = 45 ksi.

In this analysis, the following will be used for the cell wall stress for the D + L load combination.

(This is a membrane stress only.)

CrI = (A)(density)(length)/(area)

WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 8-3 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 8-1: Summary of Cell Wall Stresses Combination Stress Code Summed Allowable Stress Interaction Equation Type Level Actual (ksi)

Ratio (9 1.0)

Stress (ksi)

Membrane A

0.05 15.70 0.003 D + L + To Membrane +

D_+_L_+_T._Mendine A

0.05 1.5(15.70) = 23.55 0.002 Bending Membrane D

22.6 30 0.753 D + L + Ta + E' Membrane+

D 44.8 D____44.8_Bedig45 0.996 Bending 8.2.2 Weld Stresses Weld locations in the STP 3 & 4 new fuel storage rack that are subjected to significant seismic loading are at the cell-to-cell connections, the cell-to-baseplate connection, and at the cell-to-coverplate connections. Bounding values of resultant loads are used to qualify the connections.

a. Cell-to-Cell Welds Cell-to-cell connections are made by a series of connecting welds along the cell height. Stresses in storage cell-to-cell welds develop due to fuel assembly impacts with the cell wall. The D + L loading stresses in the cell-to-cell welds are negligible. Su weld is assumed to be 70 ksi (the same as the base metal). Therefore, the allowable weld stresses are calculated as:

Level A [8, NF-3324.5, Table 3324.5(a)-i]:

Fv = 0.3(Suw)(0.707) = 0.3(70 ksi)(0.707) = 14.847 ksi weld metal Fv = 0.4(Sy) = 0.4(25 ksi) = 10 ksi base metal +- governs Level D [8, Appendix F, 1332.4]

Twaii = 0.1 inches base metal Twela = (0.12)(0.707) = 0.085 inches weld metal <- governs Therefore:

F, = 0.42(Suw)(0.707) = 20.8 ksi The Level A and Level D allowables are multiplied by a factor of 0.707 to account for the fillet weld throat. Table 8-2 shows that the maximum cell-to-cell weld stresses are acceptable and have interaction ratios less than 1.

Table 8-2: Summary of Cell-to-Cell Weld Stresses Combination Code Summed Actual Allowable Stress Interaction Equation Level Stress (ksi)

(ksi)

Ratio (5 1.0)

D + L + To A

0.0 10 0.0 D + L + Ta + E' D

15.3 20.8 0.736 WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-4

b.

Cell-to-Baseplate Welds The allowable stress for the cell-to-baseplate weld is the same as the allowable for the cell-to-cell welds. Table 8-3 summarizes the results, showing that interaction ratios are less than 1.

Table 8-3: Summary of Cell-to-Baseplate Welds Combination Code Summed Actual Allowable Stress Interaction Equation Level Stress (ksi)

(ksi)

Ratio (< 1.0)

D+L+To A

0.0 10 0.0 D+L+Ta+E' D

14.7 20.8 0.707

c.

Cell-to-Coverplate Welds The welds are assumed to be continuous fillet welds along the length of the coverplate. The cell-to-coverplate weld stresses are reported in Table 8-4, and show that interaction ratios are less than 1.

Table 8-4: Summary of Cell-to-Coverplate Welds Combination Code Summed Actual Allowable Stress Interaction Equation Level Stress (ksi)

(ksi)

Ratio (< 1.0)

D+L+T.

A 0.0 10 0.0 D+L+Ta+E' D

11.2 20.8 0.538 WCAP-1731 1-NP December 2010 WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-5 8.2.3 Leveling Screw Evaluation The dead load condition is not a governing condition for the new fuel storage rack because the general level of loading is far less than the SSE load condition (maximum compressive reaction load of 65.091 kips). This is shown in Table 8-5 through Table 8-7.

Table 8-5: Level A Maximum Leveling Screw Load Weight of lOx 10 Rack + 100 Fuel Assemblies 75,342 Lbf Number of Leveling Screws 12 Load per Leveling Screw 6,278.5 Lbf Table 8-6: Summary of Leveling Screw Stresses Combination Axial Stress (ksi)

Bending Stress (ksi)

Shear Stress (ksi)

Equation D + L + To 6.2785/8.55 = 0.734 0.0 0.0 D + L+T,+E' 65.091/8.55 =7.61 50.91/3.53 = 14.42 25.181/6.41 = 3.93 Table 8-7: Leveling Screw Combined Axial, Bending, and Shear Stresses Shear Combination Axial + Bending Interaction Ratio Snea r

f. / F.:5 0.15 Interaction Ratio Equation

(* 1.0) f, F,:5 1.0 D + L + To 0.734/51.9 = 0.014 0.734/51.9 = 0.014 0.0 D + L + Ta + E' 7.61/73.73 = 0.103 (7.61/73.73) + (14.42/98.0) = 0.250 3.93/58.8 = 0.067 8.3 DROPPED FUEL ASSEMBLY EVALUATION The assumed fuel assembly is a representative fuel assembly plus the handling tool, having a total maximum dry weight of 572 Kg (1,263 lbs). It was postulated to be dropped from a height of 1.8 m (5.9 ft) above the top of the rack, as described in the COLA Part 2, Tier 2, Section 9.1, Revision 4 [1]. The fuel drop analysis was performed on a representative 1 lxI 1 fuel rack that was intended to bound both the 10xl0 new fuel rack and the various sizes of the spent fuel racks.

As such, the analysis considered a fuel assembly dropped through the air and loading a dry fuel rack, which is the most limiting condition. Details of the analysis are provided in

]a,*c WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-6 8.3.1 Drop Orientations Three drop orientations were considered:

  • The drop of a fuel assembly onto the top of a rack with the assembly in a vertical position.
  • The drop of a fuel assembly onto the top of a rack with the assembly in an inclined position.
  • The drop of a fuel assembly through an empty rack cell to the bottom of the rack.

These orientations are shown in Figure 8-1, Figure 8-2, and Figure 8-3, respectively. These figures are intended to illustrate the orientations of the dropped fuel assembly only. The rack shown is an 8x12 rack, and is not the actual rack evaluated for this report.

WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-7 1MIPACJ AREA STPRAI Figure 8-1: Fuel Assembly Drop on Top of Rack, Vertical Orientation WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-8 VU&

1 OM M~ AKA FWRAM Figure 8-2: Fuel Assembly Drop on Top of Rack, Inclined Orientation WCAP-1731 1-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-9 STORAE RACK Figure 8-3: Fuel Assembly Drop through to Bottom of Rack WCAP-17311-NP December 2010 Revision 1

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-10 8.3.2 Drop Locations The fuel assembly was dropped at seven different locations to find the location with maximum effect. The locations are depicted in Figure 8-4.

610101010(0 1~I~I 6 10 I 1 0!o0oQ1 o o 0o0?M b~o 010 MO(00(Ov 00100 100 00(010 O

1 100 0TO 00 Ct:'l 000-10, 0000,0 00"00000N"00 0 0 O0 0 0o 0 0 0o ElC o

m1 0

0 1 0F06M F,:ý71 L :7 J, a

Support Pad Location Drop Case Location Figure 8-4: Support Pad and Fuel Assembly Drop Locations 8.3.3 Dropped Fuel Assembly Analysis Results It must be demonstrated that the fuel racks will retain functional capability after being loaded by a dropped fuel assembly. Explicit dynamic drop analyses of fuel assemblies impacting the fuel rack were performed using the dynamic simulation code LS-DYNA in [

I, c to ensure that the integrity of the rack is maintained and to determine the forces transferred to the vault floor. A fuel assembly dropped in the vertical position was judged to be the most limiting condition.

For the various fuel assembly drops onto the top of the fuel rack cell, the maximum plastic deformation is a depth of 6.05 inches. Since the distance from the top of the fuel rack cell to the top of the neutron absorber is 31 inches, the active fuel region of the cell remains undamaged.

For a fuel assembly that drops through a cell and hits the baseplate, the maximum force imparted to the new fuel vault floor from the rack support feet is 95,490 pounds.

WCAP-1731 1-NP December 2010 WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 8-11 8.4 STUCK FUEL ASSEMBLY EVALUATION COLA Part 2, Tier 2, Section 9. 1, Revision 4 [ I ] states that, for spent fuel racks, the loads experienced under a stuck fuel assembly condition are typically less than those calculated for the seismic conditions. Therefore, a separate load combination is not required. The loads associated with a stuck fuel assembly in a new fuel rack are very similar to the loads associated with a stuck fuel assembly in a spent fuel rack. The seismic loads associated with the new fuel racks are larger than the seismic loads associated with the spent fuel racks due to the effects of water on the spent fuel racks stored in the spent fuel pool. Therefore, the loads acting on a new fuel rack due to a stuck fuel assembly are also typically less than those calculated for the seismic conditions, and a separate load combination is not required.

WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 9-1 9

CONCLUSIONS From the single-rack analyses performed based on the loading combinations listed in Table 4-1, the following conclusions are made regarding the design and layout of the STP 3 & 4 new fuel storage rack:

All rack cell wall and leveling screw stress factors are significantly below the allowable stress factor limit of 1.0.

  • All weld stresses are below the allowable limits.
  • The racks are able to withstand the dropped fuel assembly impact without losing functional capability or damaging the neutron absorbing material.

Therefore, the design of the STP 3 & 4 new fuel storage rack is considered to meet the requirements for structural integrity for the postulated Level A and Level D conditions defined.

Table 9-1 summarizes the significant results.

Table 9-1: Summary of New Fuel Rack Stresses Component Load Case Stress Type Interaction Ratio Membrane 0.003 D + L + To Membrane + Bending 0.002 Cell Wall Membrane 0.753 D + L + Ta + E' Membrane + Bending 0.996 Combined Axial and D + L + To Bending Shear 0

Leveling Screw Combined Axial and 0.250 D + L + Ta + E' Bending Shear 0.067 D+L+To Shear 0

Cell-to-Cell Weld Stress D + L + Ta + E' Shear 0.736 Cell-to-Baseplate Weld D + L + To Shear 0

Stress D + L + Ta + E' Shear 0.707 Cell-to-Coverplate Weld D + L + To Shear 0

Stress D + L + T, + E' Shear 0.538 WCAP-17311-NP December 2010 Revision I

U7-C-STP-NRC-100260 WESTINGHOUSE NON-PROPRIETARY CLASS 3 10-1 10 REFERENCES

1.

Combined Operating and Licensing Application Part 2, Tier 2, Section 9.1 "Fuel Storage and Handling," Revision 4.

2.

Design Control Document Part 2, Tier 2, Appendix 3A, "Seismic Soil Structure Interaction Analysis," U.S. ABWR Design Control Document, GE Nuclear Energy, Revision 4, March 1997.

3. E

]axc

4. E
5.

NUREG-0800, Rev. 2, U.S. Nuclear Regulatory Commission Standard Review Plan, March 2007 (SRP 3.8.4 and 3.7.2).

6.

Not Used

7. E a.c
8.

ASME Boiler and Pressure Vessel Code, 1989 Edition.

9.

The Institute of Electrical and Electronics Engineers, Inc., IEEE Std 344-1975, "IEEE Recommended Practices for Seismic Qualification of Class 1 E Equipment for Nuclear Power Generating Stations," 1975.

10.

Regulatory Guide 1.124, "Service Limits and Loading Combinations for Class 1 Linear-Type Supports."

11.

Regulatory Guide 1.60, "Design Response Spectra for Seismic Design of Nuclear Power Plants."

12.

Regulatory Guide 1.61, "Damping Values for Seismic Design of Nuclear Power Plants."

13.

Regulatory Guide 1.100, "Seismic Qualification of Electric and Mechanical Equipment for Nuclear Power Plants."

14.

Westinghouse Letter, LTR-SST-09-35, Rev. 0, "ANSYS 11.0 for XP64 Released Letter," July 6, 2009.

WCAP-17311-NP December 2010 Revision 1

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