L-MT-1 5-056Enclosure 2

ENCLOSURE 2

AREVA CALCULATION 11042-0204, REVISION 3

ALLOWABLE FLAW SIZE EVALUATIONIN THE INNER TOP COVER PLATE CLOSURE WELD

FOR DSC #16

10 pages follow

CONTROLLED COPY E-203

Y

AARE EVA

Form 3.2-1Calculation Cover Sheet

Revision 10

11042-0204

3

Page 1 of 10JPROJECT NAME:

DCR NO (if applicable) : NUHOMS® 61 BTH Type 111042-022 Rev.0 IDSCs for Monticello Nuclear

_________________________ Generating PlanPROJECT NO: 11042 CLIENT: Xcel EnergyCALCULATION TITLE:Allowable Flaw Size Evaluation in the Inner Top Cover Plate Closure Weld for DSC #16

SUMMARY DESCRIPTION:1) Calculation SummaryAn allowable flaw size of 0.15 inch is calculated for a 0.25 inch Inner Top Cover Plate (ITCP) weld inDSC # 16. Limit load analysis per ASME Code, Section XI, Appendix C is used to determine theallowable flaw size.

2) Storage Media LocationRev.0: Secure network drive initially, then redundant tape backup.Rev.1, 2 and 3 - No additional software files.

If original issue, is licensing review per TIP 3.5 required?Yes LI No LI (explain below) Licensing Review No.: N/A

Software Utilized (subject to test requirements of TIP 3.3): Software Software LogANSYS Version: Revision:

14.0.3 Not applicablewhen Rev.0 wasissued.

Calculation is complete:2015.09.10

/ 113:52:13Originator Name and Signature: Veeresh Sayagavi. • 04'00' Date: 0/021Calculation has been checked for consistency, completeness andcorrectness:

HAROON Raheel4--201 5.09.10

15:07:27 -04'00' Date: 9110/2015

Checker Name and Signature: Raheel HaroonCalculation is approved for use:

SHI H Digitaly signed bySHlH Yueh-9/02 1DN: o-AREVA GROUP.

Project Engineer Name and Signature: IU~IaI~Date:

ACalculation No. 11042-0204Revision No. _ __ _

A R E VA Calculation Page 2 of 10

REVISION SUMMARY

Affected AffectedRev. Desc ri pti on Pag es Dis ks

0 Initial issue All All

I Excel Energy comments incorporated. 1-11 134on

Correct editorial error on Table 4 and Table 6. The nodal2 force reported should be "lbs" instead of "kips". Add I1,2, 13 and Nn

clarification about nodal force and force/in in Table 4 14through Table 7 per OCR 11042-020, Rev. 0.

Files relatedRevised such that this calculation only evaluates the As indicated to Outer Topcritical flaw size in the Inner Top Cover Plate (ITCP) and by the Cover Plateincreased the weld size to 0.25 inch from 3/16 inch revision Weld (OTCP)evaluated earlier. bars. are

____________________________________________ _________ removed.

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TABLE OF CONTENTS

Page

1.0 PURPOSE .................................................................................................... 42.0 CONSERVATISM /ASSUMPTIONS........................................................................ 43.0 DESIGN INPUT/DATA....................................................................................... 4

3.1 Bounding Load Combinations ........................................................................ 44.0 METHODOLOGY ............................................................................................ 4

4.1 Allowable Flaw Evaluation ............................................................................ 44.2 Limit Load Analysis.................................................................................... 5

5.0 REFERENCES............................................................................................... 66.0 NOMENCLATURE ........................................................................................... 67.0 COMPUTATIONS............................................................................................ 7

7.1 Allowable Flaw Size Evaluation....................................................................... 77.1.1 Weld Post-Processing and Stress Calculation .............................................. 77.1.2 Determination of Allowable Weld Flaw Size................................................. 7

8.0 RESULTS ..................................................................................................... 89.0 CONCLUSIONS.............................................................................................. 810.0 LISTING OF FILES .......................................................................................... 8

LIST OF TABLES

Page

Table 1 Safety Factors for Circumferential Flaw (Ref. [5.1]) ..................................................... 9Table 2 Weld Stress Results of Inner Top Cover Plate Welds for Individual Loads............................ 9Table 3 Load Combination Weld Membrane Stress (o-', ) Result for Inner Top Cover Plate Weld ........... 9

LIST OF FIGURES

Page

Figure 1 Subsurface Crack Model for ITCP Welds.............................................................. 10Figure 2 Surface Crack Model for ITCP Welds.................................................................. 10

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1.0 PURPOSE

The calculation calculates the NUHOMS® 61BTH Type 1 DSC allowable flaw size for increased Inner TopCover Plate (ITCP) closure weld size of 0.25 inch.

2.0 CONSERVATISM/IASSUMPTIONS

1. The weld allowable flaw size is based on radial tensile membrane force acting on the weld; howeverit is conservatively evaluated based on SRSS method excluding the compressive stresses in theweld.

2. ASME Code, Section Xl, Appendix C Limit Load evaluation uses only primary stresses. Residualstress being a secondary stress are not considered.

3.0 DESIGN INPUTIDATA

Per Ref. [5.9], the distance between the weld root and crown at the canister wall ranges from 0.25 inches to0.4 inches for ITCP lid weld. Thus, the ITCP weld size is modified to 0.25 inch in lieu of 3/16 inches perdesign.

3.1 Bounding Load Combinations

All bounding normal, off-normal and accident load combinations are taken from Ref. [5.2].

4.0 METHODOLOGY

4.1 Allowable Flaw Evaluation

The allowable flaw evaluation is based on flaw evaluation methodology per ASME Code, Section XI,Appendix C Ref. [5.1]. Although the affected component is not subject to in-service inspection activities, themethodology of Section XI is deemed appropriate for this application. Determination of the allowablesurface and sub-surface flaw depth is accomplished by means of the methodology, outlined below. Figure 1shows the possible circumferential flaw for ITCP Welds. It is stipulated that the allowable flaw configurationis a circumferential weld flaw exposed to the tensile component radial stress. Conservatively the weld flawis evaluated for all the component stresses except the compressive stresses onto the weld.

Safety factors used to determine the allowable flaw size are taken from Appendix C, Section C-2621 of Ref.[5.1]. All bounding normal, off-normal and accident load combinations are taken from Ref ([5.2], Table 52).

The following are basic steps that are performed in order to determine the allowable flaw depth:

1) Identification of bounding load and load combinations analyzed in Ref. [5.2].

2) Calculate the resultant force acting on the weld ignoring the compressive load. Evaluate membranestresses occurring at the ITCP weld.

3) Determine limiting membrane stresses in the ITCP weld for all load combinations.

4) Multiply limiting stresses with safety factors S~m for the corresponding Service Levels (Ref. [5.1]) aspresented in Table 1.

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5) Since ITO3P weld is GTAW (Non-Flux weld), thus according to ASME Code Sec XI, Division 1, Fig (C-4210-1, Ref. [5.1] maximum allowable flaw depth is estimated using Limit Load criteria.

4.2 Limit Load Analysis

The relation between the allowable membrane stress and flaw depth at incipient stress is taken from Ref.[5.7], Table 12.28, which is given as

3af(-a. . . ................. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (1)2 + 422+ 9(1- a) 2

where:

-',= The allowable membrane stress, which is the applied membrane stress times the differentservice factors, SFm determined from Appendix C, Section C-2621 of Ref. [5.1].

'f= the flow stress, defined as (Gf = (Sy, + S,,)/2, where S, and Su are yield and ultimate strengths,

respectively.

= -- and2, ---- 0, for no bending stress on the weld.tW Oam

a = half crack length for center cracked plate,= crack depth for single edge cracked plate

t = half plate thickness for center cracked plate,= plate thickness for single edge cracked plate

for a 3600 circumferential flaw, c = w, hence equation (1) reduces to

Using equation (2) the allowable flaw depth (a) is obtained as

a = (oaf-a'm .SFm )-•L ........................................................................... (3)

Equation (3) can be applied for both surface and subsurface crack (center-cracked plate and single edgecrack plate model), respectively.

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5.0 REFERENCES

5.1 ASME Boiler and Pressure Vessel Code, Section XI, Division 1, Appendix C, 2004 edition through2006 Addenda.

5.2 TN Calculation NUH61 BTH-0200, Rev.0, "NUHOMS®-61 BTH Type 1 Dry Shielded Canister ShellAssembly Structural Analysis".

5.3 ANSYS Computer Code and User's Manual, Release 14 (used only for post processing results).5.4 ISG-15, Rev. 0, "Materials Evaluation".5.5 ASME Boiler and Pressure Vessel Code, Division 1, Subsection NG, 1998 edition through 2000

Addenda.5.6 TN Calculation No. NUH61 BTH-0403, Rev. 2, "NUHOMS%-61 BTH DSC Thermal Evaluation for

Storage and Transfer Conditions".5.7 T.L. Anderson, "Fracture Mechanics, Fundamentals and Applications", Second Edition.5.8 TN Engineering Evaluation No. 11 042-EE-001, "Monticello Nuclear Generating Plant: Engineering

Evaluation of Spent Fuel Storage Canisters with Nonconforming Closure Welds".5.9 Design Input Document DI-1 1042-02 Rev.0, AREVA Document Number 180-9236022-000, NDE

Services Final Report, Monticello, DSC-16, Phased Array UT Examination Results of the Inner andOuter Top Cover Lid Welds.

6.0 NOMENCLATURE

ITCP: Inner Top Cover PlateDSC: Dry Shielded CanisterDWH: Horizontal Dead WeightPI1: Internal PressureFwe~d : Resultant weld load (excluding compressive load)R : Radius of the ITCP weldTweld : Weld sizeWeld Stress: The weld stress for the ITCP.a-',,,: Weld membrane stress at limit load for ITCP.SRSS: Square root of sum of squares.

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7.0 COMPUTATIONS

7.1 Allowable Flaw Size Evaluation

7.1.1 Weld Post-Processing and Stress Calculation

All the controlling load combinations for ITCP weld are listed in Ref. [5.2, Table 54]. It is evident from theseresults that the critical cases are 75g side drop and 25g corner drop load cases.

Weld nodal forces for ITCP weld nodes are post-processed using ANSYS. The compressive radial forceson the welds would have no impact on the allowable weld flaw evaulation. Thus, these forces are excludedfrom the weld flaw evaluation.

The weld membrane stress (o",~,) at limit load for ITCP is calculated using SRSS method, for a 0.25 inch

ITCP weld, while excluding the compressive loads onto the weld. Weld membrane stress for individual loadcases and the bounding load combinations are listed in Table 2 and Table 3 respectively for ITCP.

The top cover plate welds are evaluated assuming the shear load on the top cover plate welds due to a 25gcorner drop. The outer top cover plate of the DSC is assumed to be unsupported by the cask in the axialdirection. ITCP welds resist the load such that the stress can be calculated based on the total weld area ofboth ITPC and OTCP welds. The allowable is based on a maximum temperature of not more than 3000 Ffor any transfer condition (Ref. [5.6]).

For the corner drop the total shear load on the welds is 9,437 lb/in (Ref. [5.2], Section 10.2). The loadshared by the ITCP weld (1/4") and OTCP weld (0.50") are calculated below.

PlTcp (.(1/4-+-0.50)' x9,437=3,146 lb/in

These shear loads are used in calculating the load combinations for the 25g corner drop. Weld membranestress (o",,) for individual load cases are calculated for ITCP.

7.1.2 Determination of Allowable Weld Flaw Size

Table 3 lists the bounding load combinations to specify limiting depth of weld flaw for ITCP weld. The yieldstrength (ar) and ultimate tensile strength (au) for SA-240 Type 304 at 300 °F are 22.4 ksi and 66.2 ksi (Ref.[5.2]). So flow stress (Or) as per Section 4.3 is

Of = (22.4+66.2)/2 = 44.3 ksi

The allowable flaw depths, calculated by means of the methodology described in Section 4.0.

Note that in the case of subsurface flaws, the 't' and 'a' in equation (1) are half-width and half-crack depth,respectively, whereas for surface flaws 't' and 'a' respectively represent the weld thickness and the crackdepth.

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ITCP Allowable Weld Flaw

The weld membrane stress (o-',n) are listed in Table 3. The bounding weld membrane stress is 17.08 ksi.The allowable flaw size for a 3600 weld flaw is calculated below.

a=(c-j -o",,.SF,7 ,

= (44.3 - 17.08) 0.25 /44.3 = 0.15" (Using a single edge cracked plate model)

For center crack plate model (used for a subsurface flaw), the half-crack length a, is 0.15/2 =0.075". The

total allowable crack length is 2*a = 0.15".

8.0 RESULTS

The ITPC closure welds for individual and combination load cases are listed in Table 2 and Table 3respectively. The allowable flaw for surface (crack depth =a) and subsurface (half-crack length =a, totalcrack length =2a) flaws for ITCP is 0.15 inch and 360° along the circumference.

9.0 CONCLUSIONS

The evaluations performed in this calculation indicate that the minimum allowable flaw size for the ITCP is0.15" for a full 3600 weld flaw.

10.0 LISTING OF FILES

Below is the listing of all files used in the ANSYS for Finite Element Analysis. All the nodal forces have been extractedusing ANSYS Release 14.0.3 Ref. [5.3].

Load Case DateN.File Name TieDescription

12/09/1 999 20 psi internal pressure evaluation, Ref. [5.2, Table 22].4 Q61 IP~b ad .st12:40a These files are not part of the archived files.

05/27/2000 75g side drop acceleration, Ref. [5.2, Table 22]. These4 T1 BD~b ad .st2:40a files are not part of the archived files.

Weldjforces_QT6IBIP, inp and.ot,1 W9PFQK~L.err, 05/22/2014 Post processing files for 20psi internal pressure.

1 QT6BIP_weld_20psi lTCP.txt 14:14:34

Weld_forces_T61BSD, inp and 05/22/2014 Ps rcsigflsfr7gsd rp1.out, WT35B3~E.err,140:5 Psprcsigfesor7giddo.

T61 BSD_weld_ITCP.txt 1:93

Note: For the above listed files, date is reported by the OS on the report issue date and time, these valuesmay be changed by windows depending on time of the year (e.g., daylight savings time) and time zones

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Table 1 Safety Factors for Circumferential Flaw (Ref. [5.1])Circumferential Flaws

Servel Membrane StressLevelSF=

A 2.7

B 2.4

C 1.8

D 1.3

Table 2 Weld Stress Results of Inner Top Cover Plate Welds for Individual Loads

LodDsrpion Loa.Cse F'm F'm Force (2) o",m (3)Step DsrpinLaCse Nodal Force (lbs/in) (ksi)

(Ibs)( 1)20 psi internal pressure on inner pressure PI(20) 277 139 05

4 boundary4 75g side drop acceleration Side Drop 5495 2761 11.05

Notes(1) The .db and .rst files are taken from Ref. [5.2] and are listed in Section 9.0.(2) The element size of ANSYS elements is 1.99 inch Ref. [5.2]. Hence, the F'm Force = F'= Nodal force /1.99(3) The weld throat size is 1/ in., hence the o-',, = F'rm Force/1(1/4)

Table 3 Load Combination Weld Membrane Stress (o",,) Result for Inner Top Cover Plate Weld

Load Service Stress Safety Factor o",Case Level Category Loads o-m, (ksi) SFm (ksi) x

TR-9 D P P1(20) + 25g Corner Drop (1) 13.14 1.3 17.08TR-10 D P P1(20) + 75g Side Drop 11.61 1.3 15.09

Notes(1) The corner drop load combination is calculated by adding 3,146 lbs/in of shear load to the individual loadsfor PI(20) load case obtained from Ref. [5.2].

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I--

T--t -•--ti--

Figure 1 Subsurface Crack Model for ITCP Welds

--- I----I I .1

Figure 2 Surface Crack Model for ITCP Welds