ML100190075

CDI Report No. 09-26NP, Stress Assessment of Nine Mile Point, Unit 2 Steam Dryer at CLTP and EPU Conditions, Cover to Page 62, Revision 1

ML100190075
Person / Time
Site:	Nine Mile Point
Issue date:	12/31/2009
From:	Teske M Continuum Dynamics
To:	Constellation Energy Group, Nine Mile Point, Office of Nuclear Reactor Regulation
References
TAC ME1476 09-26NP, Rev 1
Download: ML100190075 (68)

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• ATTACHMENT ATTACHMENT 5 CDI REPORT REPORT 09-26NP 09-26NP (NON-PROPRIETARY),

(NON-PROPRIETARy), STRESS ASSESSMENT ASSESSMENT OF NINE MILE POINT UNIT 2 STEAM DRYER DRYER AT CLTP AND EPU CONDITIONS, CONDITIONS, REV.l REV.1 (LAR ATTACHMENT ATTACHMENT 13.7)

Certain information, infonnation, considered proprietary by CDI, considered proprietary CD I, has been deleted from this Attachment. The deletions brackets..

are identified by double square brackets

• Nine Mile Point Nuclear Nuclear Station, LLC December December 23, 2009 LLC

Document Does Not Contain This Document Contain Continuum Dynamics, Inc. Proprietary Continuum Dynamics, Proprietary Information Information

• Stress Assessment of Nine Mile Point Stress Assessment Report No. 09-26NP CDI Report 09-26NP Steam Dryer Unit 22 Steam CLTP and EPU Conditions Dryer at CLTP Revision 1 Prepared by Prepared by Continuum Continuum Dynamics, Inc.

34 Lexington Avenue Ewing, NJ 08618 08618 Prepared Prepared under Purchase Order No. 7708631 for Purchase Order Constellation Energy Group Constellation Nuclear Station, LLC Nine Mile Point Nuclear

• P. 0.

O. Box 63 Lycoming, NY 13093 Approved by Approved 13093 Alan J. Bilanin Reviewed by Milton E. Teske December 2009 December This report complies with Continuum Dynamics, Inc. Nuclear Quality Assurance Program currently in effect.

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• Executive Executive Summary The finite element model and analysis methodology, used to assess stresses flow of steam through the steam dryer at Nine Mile Point Unit 2 (NMP2), are described stresses induced by thethe described and applied to obtain stresses at CL CLTP TP conditions. consistent with those carried out conditions. The analysis is consistent out in the U.S. for prior dryer qualification to EPU conditions and the resulting stresses are assessed assessed for compliance with the ASME B&PV Code 2007 [1],Section III, subsection NG, NO, for the load corresponding to normal combination corresponding operation (the Level A Service normal operation Service Condition).

The analysis is carried out in the frequency domain, which confers confers a number number of useful computational advantages computational advantages over a time-accurate time-accurate transient analysis including the ability to assess the effects of frequency frequency scaling in the loads without the need for additional finite element element calculations. (( ((

(3))) The analysis (3))) The analysis develops develops a series of of unit stress solutions corresponding to the application of a unit pressure at a MSL at specified frequency, f.f. Each unit solution is obtained by first calculating the associated acoustic pressure field using a separate separate analysis that solves the damped Helmholtz equation equation within the steam dryerdryer

[2]. This pressure field is then applied to a finite element structural structural model of the steam dryer and the harmonic stress response response at frequency, f,f, is calculated using the commercial commercial ANSYS 10.0 10.0 finite element element analysis analysis software. This stress response response constitutes constitutes the unit solution and is stored stored as a file for subsequent subsequent processing. Once all unit solutionssolutions have been computed, computed, the stress response response for any combination combination of MSL pressure spectrums (obtained(obtained by Fast Fourier Fourier Transform Transform of the pressure histories in the MSLs) is determined determined by a simple matrix multiplication of these spectrums with the unit solutions.

Results obtained from application application of the methodology to the NMP2 steam dryer show that at nominal CLTPCLTP operation (no frequency shift) the minimum alternating alternating stress ratio (SR-a) anywhere anywhere on the steam dryer is SR-a=3.00.

SR-a=3.00. The loads used to obtain this value account for all the end-to-end end-to-end biases and uncertainties uncertainties in the loads model [3] and finite element element analysis. It is is noted that:

(i) The signals account for the revised revised biases and uncertainties uncertainties in the 60-70 Hz and 70-100 Hz frequency ranges. For various reasonsreasons the ACM was not recalibrated recalibrated over the new frequency ranges (such a recalibration is resource-intensive recalibration resource-intensive and would lead to a new new revision of the ACM). As a result, the biases and uncertainties in the new intervals are overly conservative and higher than they would otherwise overly conservative otherwise be, had such a recalibration of recalibration of the ACM been performed.

(ii) It is known that the signals used to estimate (ii) estimate acoustic loads contain significant non-acoustic acoustic contributions referred referred to collectively collectively as plant noise (e.g., (e.g., pipe vibrations).

However, to expedite qualification, no noise removal removal has been performed for the analysesanalyses contained contained herein.

Both of these load details increase conservatism conservatism in the analysis. Moreover, to account for uncertainties in the modal frequency predictions of the finite element model, the stresses are also

• computed for loads that are shifted in the frequency domain by +2.5%,

i

+5%, +/-7.5% and +/-10%.

+/-2.5%, +/-5%, +/-1O% .

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• The minimum alternating stress ratio encountered at any frequency shift is found to be minimum alternating SR-a=2.89 occurring at the -5% shift. The stress ratio due to maximum stresses (SR-P) (SR-P) is dominated by static loads and is SR-P=1.34 SR-P=1.34 both with and without without frequency shifts.

Since flow-induced acoustic resonances are not anticipated anticipated in the steam dryer, the alternating alternating operation can be obtained stress ratios at EPU operation obtained by scaling the CLTP CL TP values values by the steam flow flow 2

velocity squared, (UEPulUcLTPi=1.1782=1.388.

(UEPu/UcLTp) =1 .1782=1.388. Under this approach, approach, the limiting alternating alternating stress ratio becomes SR-a=2.89/1.388=2.08. Given that the alternating becomes SR-a=2.89/1.388=2.08. alternating stress ratio SR-a obtained at EPU remains above 2.08 at all frequencyfrequency shifts together together with the comparatively small dependence dependence of SR-P upon acoustic loads, acoustic loads, the Unit 2 dryer is expected to qualify at EPU conditions.

In order to achieve these stress ratios, the closure plate requires modification modification and welds on on the lifting rod braces require require reinforcement. For the closure plates reinforcement reinforcement strips are added added to stiffen the closure plates. Also, the top 18 inches of the welds connecting the closure closure plates to the vane banks and to the hoods hoods are reinforced reinforced by adding a weld on the inner side of the closure plate. For the lifting rod braces, increasing the weld size from 114 braces, increasing 1/4 in to 1/2 112 in meets the target target stress ratio.

ratio .

• ii

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• Summary of Changes Changes from Revision 0 to Revision 1 The sole change made from Revision 0 of C.D.!.

elimination of the reference:

C.D.I. Report 09-26P 09-26P to the current Revision 1 is EPR! (2008), B EPRI WRVIP-194: BWR Vessel and BWRVIP-194: andInternals Project.Methodologies Internals Project: for Methodologiesfor Demonstrating Demonstrating Steam Dryer Dryer Integrity Integrity for Power Power Uprate, Uprate, Palo Alto, CA: 2008. 1016578 1016578..

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• Section Table of Contents Page Executive SumSummarym ary .........................................................................................................................

......................................................................................................................... i Sum m ary of Changes from Revision Summary Revision 0 to Revision 11....................................................................

.................................................................... iii iii Table of Contents ...........................................................................................................................

........................................................................................................................... iv

1. Introduction

1. Introduction and Purpose ............................................................................................................

........................................................................................................ 11

2. M ethodology ..............................................................................................................................

Methodology .............................................................................................................................. 33 2.1 Overview Overview ......... ..............................................

............................................................................................................................... 33 2.2 [(

([ ......................................................................

(3))) .....*...**..*....***............****..*.*..*.........*....*.....***.*

(3))) 55 Com putational Considerations 2.3 Computational Considerations ..................................

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

3. Finite Element Element M odel D escription ..........................................................................................

Model Description .............................................................................................. 9 3.1 Steam D ryer Geometry Dryer Geom etry .....................................................................................................

......................................................................................................... 9 Material Properties ...........................................................................................................

3.2 Material .............................................................................................................. 12 12 Model Simplifications 3.3 Model Sim plifications ........................................................................................................

................................................................................................... .,. 12

,. 12 3.4 Perforated Plate M odel ...................................................................................................

Model ....................................................................................................... 13 13 Vane Bank Model 3.5 Vane M odel ..........................................................................................................

............................................................................................................... 15 15 W ater Inertia Effect 3.6 Water Effect on Subm Submerged erged Panels .........................................................................

.................................................................... 16 16 3.7 Structural Damping Dam ping .............................................................................................................

........................................................................................................ 16 16 3.8 M esh Details Mesh Details and Element Element Types .......................................................................................

.................................................................................. 16 16

• 3.9 Connections Between Between Structural Com ponents ....................................................................

Components ................................................................

3.10 Pressure Loading ...........................................................................................................

4. Structural A

............................................................................................................... 28 nalysis ....................................................................................................................

Analysis ....................................................................................................................

4.1 Static Analysis ....................................................................................................................

4.2 Harmonic Harm onic A Analysis nalysis ..............................................................................................................

4.3 Post-Processing ...................................................................................................................

16 16 28 31 31 31 31 31 31 37 37 4.4 Computation 4.4 Com putation of of Stress Stress Ratios Ratios for for Structural A ssessment ...................................................

Assessment ............................................... 37 37 4.5 Finite Elem Element ent Sub-modeling Sub-m odeling .........................................................................................

..........................................................................................'... 40

5. Results .......................................................................................................................................

5. ....................................................................................................................................... 48 5.1 General Stress D istribution and High Distribution H igh Stress Locations ......................................................

................................................. 49 5.2 Load Com binations and Allowable Combinations A llow able Stress Intensities ...................................................

Intensities ........................................................ 63 5.3 Frequency Content and Filtering ofthe of the Stress Signals ...................................................

....................................................... 85 85

6. Conclusions Conclusions ....................................................................................................................................

,............................................................................................................... ~ ......... 92 References .................................................................................................................................

7. References ................................................................................................................................. 93 Appendix A Sub-modeling Sub-modeling and Modification of Closure Plates ............................................

................................................. 95 Sub model Sub m odel N ode 101175 Node 101175 .........................................................................................................

......................................................................................................... 100 100 Sub m odel node 91605 ............................................................................................................

model ............................................................................................................ 107 107 Sub m odel model node 95172 ............................................................................................................

............................................................................................................ 115 115 m odel node 100327 Sub model 100327 ..........................................................................................................

.......................................................................................................... 124 124

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• Introduction and Purpose

1. Introduction Plans to qualify the Nine Mile Point nuclear plant for operation (EPU) operating condition require an assessment of the the.

operation at Extended Power Uprate steam dryer stresses experienced experienced under the increased loads. The steam dryer loads due to pressure fluctuations in the main steam lines (MSLs) are potentially damaging damaging and the cyclic stresses stresses from these loads can produce fatigue cracking if loads are sufficiently high. The industry industry has addressed addressed this problem problem with physical modifications modifications to the dryers, as well as a program to define steam dryer loads and their resulting stresses. The purpose of the stress analysis discussed here is to calculate the maximum and alternating stresses generated during Current Licensed Licensed Thermal Thermal Power (CLTP) and Extended Power Uprate (EPU) and to determine the margins that exist when compared to stresses that comply with the ASME Code (ASME B&PV Code,Section III, subsection NG).

The stress analysis of the modified NMP2 steam dryer establishes whether the existing existing and proposed modifications are adequate for sustaining structural integrity proposed modifications integrity and preventing preventing future weld cracking cracking under planned EPU operating operating conditions. The load combination considered considered here corresponds corresponds to normal operation (the Level A Service Condition) and includes fluctuating pressure loads developed developed from NMP2 main steam line data, and weight. The fluctuating fluctuating pressure pressure loads, induced by the flowing steam, are predicted using a separate acoustic circuit circuit analysis of the steam dome and main steam lines [4]. Level B service Level service conditions, which include seismic loads, are not included in this evaluation.

evaluation .

• ((

(3))) This approach also affords a number of (3))) This approach also affords of additional computational computational advantages advantages over transient simulations simulations including:

including: ((

(3)))

(3)))

This last This last advantage advantage is realized through the use of "unit" "unit" solutions representing the stress distribution resulting from the application of a unit fluctuating pressure at one of the MSLs at a particular frequency. rr ýý)

(3)))

This report describes the overall methodology used to obtain the unit solutions in the frequency domain and how to assemble them into a stress response for a given combination of of

• pressure signals in the MSLs. This is followed by details of the NMP2 steam dryer finite 1

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• element model including the elements used and overall resolution, treatment of connections connections between elements, the hydrodynamic hydrodynamic model, the implementation of structural structural damping and key idealizations/assumptions inherent to the model. Post-processing idealizations/assumptions Post-processing procedures are also reviewed reviewed including the computation computation of maximum and alternating stress intensities, identification identification of high adjustments to stress intensities at welds and evaluation of stress ratios used to stress locations, adjustments establish compliance compliance with the ASME Code. The results in terms of stress intensity distributions and stress ratios are presented next together with PSDs of the dominant dominant stress components.

In order to meet target EPU stress levels (i.e., an alternating alternating stress ratio of 2.0), two components required modification: the closure plate welds and the lifting rod support braces. In required modification:

the former case, case, stiffening strips or ribs are added to the closure plate to simultaneously simultaneously increase the frequency and lower stresses [5]; also the closure plate attachment weld is strengthened strengthened by placing an additional weld on the interior side of the junction where the closure plate meets the hood or vane bank. For the lifting rod braces, the existing 114 1/4 in weld is increased to 1121/2 in.

Both modifications modifications involve the use of highly detailed solid element-based sub-models element-based sub-models of these accurately assess the local stresses locations to accurately stresses..

• 2

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• 2.1 Overview Based on Methodology

2. Methodology undertaken at previous analysis undertaken on previous Quad Cities Units 1 and 2, at Quad the steam 2, the steam dryer can can experience strong experience acoustic loads due to the fluctuating strong acoustic pressures in the fluctuating pressures the MSLs connected to the MSLs connected C.D.1. has developed containing the dryer. C.D.I.

steam dome containing developed an acoustic circuit model (ACM) that, acoustic circuit given a collection collection of strain strain gage gage measurements of measurements [6] of the the fluctuating pressures in the MSLs, pressures predicts the predicts the acoustic acoustic pressure pressure field anywhere inside inside the dome and on the steam dryer the steam dome dryer [2-4].

[2-4].

The ACM formulated in ACM is formulated space and contains two major frequency space in frequency components that are directly major components directly relevant to the ensuing relevant ensuing stress here. ((

concern here.

stress analysis of concern

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Computational Considerations 2.3 Computational Considerations Focusing on the structural computational computational aspects of the overall approach, there are a number of numerical numerical and computational computational considerations considerations requiring attention. The first concerns the transfer of the acoustic forces onto the structure, particularly the spatial and frequency resolutions. The ANSYS finite element program inputs general general distributed pressure pressure differences using a table format. This consists of regular 3D rectangular (i.e., (i.e., block) nxxnyxnz nxxnyxn z mesh where na nu is the number of mesh points in the i-th Cartesian Cartesian direction and the pressure difference is is provided at eacheach mesh point (see Section 3.10). These tables are generated separately using a generated separately program that reads the loads provided from the ACM software, software, distributes these loads onto the finite element element mesh using a combination of interpolation interpolation procedures procedures on the surface and simple diffusion schemes (off-surface loads are required by ANSYS to ensure proper schemes off the surface (off-surface interpolation interpolation of forces), and written to ASCII files for input to ANSYS. A separate separate load file is written at written at each each frequency frequency forfor the the real real and imaginary component of the complex force.

The acoustic field is stored at 5 Hz intervals from 0 to 250 Hz. While a 5 Hz resolution resolution is sufficient to capture sufficient capture frequency dependence dependence of the acoustic field (i.e., the pressure at a point varies gradually with frequency), it is too coarse for representing representing the structural response especially at low frequencies. For 1% critical structural damping, one can show that the especially 1%

frequency spacing needed to resolve a damped resonant peak at natural frequency, fn, fn' to within within 10 5% accuracy accuracy is Llf==O.0064xf Af=0.0064xfn.n

• Thus for fn= fn==10 Hz where the lowest structural structural response response modes occur, a frequency interval interval of 0.064 Hz or less is required. In our calculations we require that 5% maximum 5 maximum error be maintained maintained over the range from ffn= n==5 Hz to 250 Hz resulting in a finest frequency interval of 0.0321 Hz at the low frequency end (this adequately adequately resolves all structural modes up to 250 Hz). Since there are no structural structural modes between between 0 to 5 Hz, a 0.5 Hz spacing is is

~

used over this range with minimal (less than 5%) error. The unit load, fn(w,R), fn(w,R), at any frequency, wk, cOk, is obtained by linear interpolation interpolation of the acoustic acoustic solutions at the two nearestnearest frequencies, frequencies, wi oi and o~i+1, wi+ 1, spaced 5 Hz apart. Linear interpolation interpolation is sufficient sufficient since the pressure load varies slowly over the 5 Hz range (linear (linear interpolation of the structural response would not be acceptable acceptable over this range since it varies much more rapidly over the same interval). Details regarding the frequency resolution have been provided in [7]. [7].

Solution Management Solution Management

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(3)j]

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(3)))

StructuralDamping Structural Damping harmonic analysis one has a broader selection In harmonic selection of damping models than in transient simulations. A damping factor, z, of 11%

simulations. structural analysis. In

% critical damping is used in the structural In.

exactly at two frequencies (where the enforced exactly transient simulations, this damping can only be enforced damping model is "pinned").

"pinned"). Between damping factor can by frequencies the damping Between these two frequericies by considerably smaller, for example 0.5%

considerably 0.5% or less depending on the pinning frequencies.

frequencies. Outside frequencies, damping is higher. With harmonic analysis the pinning frequencies, analysis it is straightforward straightforward to

% damping over the entire frequency range. In this damping model, enforce very close to 11% model, the

• damping matrix, D, is set to D= 2z K (0

0) where K is the stiffness matrix and co the forcing frequency. When comparing obtained with this model against that for a constant comparing the response constant damping ratio, the maximum difference 100% or higher response smaller than the 100%

any frequency is less than 0.5%, which is far smaller difference at variation response variation (7)

(7) obtained when using the pinned model required in transient simulation.

Load Frequency Rescaling Frequency Rescaling One way to evaluate the sensitivity of the stress results to approximations in the structural rescale the frequency content of the applied loads. In this modeling and applied loads is to rescale procedure the nominal frequencies, cok, are shifted to (1 procedure (l+X)cok, frequency shift, X,

+A)COk, where the frequency A, .

ranges between +/-10%, and the response between +10%, recomputed for the shifted loads. The objective response recomputed objective of the frequency shifting can be explained by way of example. Suppose that in the actual dryer a strong coupling exists at a particular frequency, co structural-acoustic coupling structural-acoustic *. This means that the following co*.

contains a significant signal at co conditions hold simultaneously: (i) the acoustic signal contains co*; (ii) the

• (ii) structural model contains resonant mode of natural frequency, con' contains a resonant con, that is near co*; (iii) the co *; and (iii) associated structural mode shape is strongly coupled to the acoustic load (i.e., (i.e., integrating the product of the mode shape and the surface pressure product pressure over the steam dryer surface surface produces a Suppose now that because significant modal force). Suppose discretization errors and modeling because of discretization modeling idealizations that the predicted resonance frequency differs from co predicted resonance co** by a small amount (e.g.,

1.5%). Then condition 1.5%). (ii) will be violated and the response amplitude therefore condition (ii) therefore significantly significantly condition (ii) when (1+ k)co*

re-establishes condition diminished. By shifting the load frequencies one re-establishes A)CO

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• near ron'

%,. The other two requirements requirements also hold and a strong structural acoustic acoustic interaction is is restored.

((

(3)]

Evaluationof Maximum and Alternating Evaluation Alternating Stress Intensities Intensities Once the unit solutions solutions have been obtained, the most intensive computational computational steps in the generation of stress intensities are: (i) the FFTs to evaluate generation evaluate stress time histories from (5); and (ii) the calculation of alternating (ii) ((

alternating stress intensities. ((

(3)))

The high computational computational penalty incurred in calculating the alternating stress intensities is due

• to the fact that this calculation calculation involves comparing the stress tensors at every pair of points in the stress history. This comparison comparison is necessary vary during the response, necessary since in general the principal stress directions can response, thus for N samples in the stress history, there will be (N-1)N/2 such pairs or, for N=64K (the number required to accurately 0.01 Hz intervals), 2.1 a cubic polynomial. ((

9 9

accurately resolve the spectrum up to 250 Hz in x 10 calculations per node each requiring 2.1x10 requiring the determination of the roots to (3)))

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• Description

3. Finite Element Model Description A description of the ANSYS model of the nine Mile Point Unit 2 steam dryer follows.

3.1 Steam Dryer Geometry A geometric representation representation of the Nine Mile Point Unit 2 steam dryer was developed developed from available drawings available drawings (provided by Constellation Energy Group and included included in the design record DRF-C-279C) within the Workbench file, DRF-C-279C) Workbench module of ANSYS. The completed model is shown in Figure 1.

1. This model includes on-site modifications modifications to the Nine Mile Point Unit 2 steam dryer.

These are as follows.

On-Site Modifications On-Site Modifications (i) The top tie rods are replaced with thicker ones.

(ii)

(ii) Inner side plates are replaced replaced with thicker ones.

(iii) Middle hoods are reinforced reinforced with additional strips.

(iv)

(iv) Lifting rods are reinforced reinforced with additional gussets.

(v) Per FDDR KG1-0265 KG 1-0265 the support support conditions are adjusted adjusted to ensure that the dryer is 100% on the seismic blocks.

supported 100%

These additional modifications modifications have been incorporated incorporated into the NMP2 steam dryer model

• and are reflected in the results presented in this report. The affected areas are shown shown in Figure 2.

ModificationsPlannedfor Modifications Plannedfor EPUEPUOperation Operation To meet the target stress ratio at EPU, reinforcement of the closure plates and increases in in selected weld sizes are recommended.

recommended. Analysis shows that the original closure plates experience experience a strong response from forcing of one of its structural structural modes. These structures structures have been modified using stiffening strips to simultaneously reinforce them and shift their frequencies frequencies away from significant acoustic acoustic loads [5]. Analysis Analysis of these components is summarized in Appendix A.

Modifications analyzed using sub-models Modifications to welds are analyzed sub-models to minimize computational computational cost. These analyses are performed performed at the following locations locations as discussed further in Section 4.5: (i) (i) the lifting rod support braces; (ii) (ii) closure plate welds and (iii)(iii) the ends of selected tie bars. In addition, previous analyses of geometrically geometrically identical and similarly loaded locations locations have been been reinforcements are implemented.

locations and in the locations where reinforcements applied at these locations Reference Frame Frame The spatial coordinates used herein to describedescribe the geometry geometry and identify limiting stress locations are expressed expressed in a reference frame whose origin is located at the intersection of the steam dryer centerline centerline and the plane containing containing the base plates (this plane plane also contains contains the top of of the upper support ring and the bottom edges of the hoods). The y-axis is parallel parallel to the hoods, the x-axis is normal to the hoods pointing from MSL C/D CID to MSL AlB,A/B, and the z-axis is vertical, vertical, positive up up..

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0.00 100.00 (in) 50.00 Overall geometry of the Nine Mile Point Unit 2 steam dryer model.

1. Overall Figure 1.

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Continuum Dynamics, Inc. Proprietary Information Information Figure 2.

2. Modify Modify the figure to eliminate eliminate inner hood strips. On-site modifications modifications accounted accounted for in the model and associated geometrical geometrical details.

details .

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• 3.2 Material Properties The steam dryer is constructed from Type 304 stainless temperature temperature of 550°F.

stainless steel and has an operating 550'F. Properties used in the analysis are summarized below below in Table Table 1.

Material properties.

Table 1. Material Young's Modulus Density Poisson 3

(10 6 psi)

(106 psi) (Ibm/in (Ibm/in3) ) Ratio Ratio stainless steel 25.55 0.284 0.3 structural steel with added water 25.55 0.856 0.3 inertia effect inertia effect The structural structural steel modulus is taken from Appendix Appendix A of the ASME Code for Type 304 Stainless Steel at an operating operating temperature 550'F. The effective temperature 550°F. properties of perforated effective properties perforated plates and submerged submerged parts are discussed in Sections Sections 3.4 and 3.6. Note that the increased increased effective density submerged components density for submerged components is only used in the harmonic analysis. When calculating calculating the stress distribution distribution due to the static dead weight load, the unmodified unmodified density of steel (0.284 lbm/in 33) is used throughout.

Ibm/in Inspections of the NMP Unit 2 dryer have revealed IOSCC IGSCC cracks cracks in the upper upper support ring (USR) and skirt. A separate analysis analysis of these cracks cracks [8] has been performed performed to determine whether: (i)

(i) they will propagate propagate further into the structure and (ii) (ii) their influence upon structural response frequencies frequencies and modes must be explicitly accounted for. To establish (i) the stress calculated in the global stress analysis is used in conjunction with the crack geometry to calculated calculate calculate the stress intensity intensity factor which is then compared compared to the threshold stress intensity. For5 0 5 the USR and skirt cracks cracks the highest stress intensity highest stress intensity factors 1.47 ksi-in are 1.47 factors are 2.75 ksi-in° and 2.75 ksi-in°.5. and ksi-in°.5 respectively; respectively; both values values are below the threshold value (3 (3 ksi-in° s 5

ksi-ino. ) implying implying that fatigue crack crack growth will not occur.

To determine determine (ii) (ii) the change in modal response frequencies due to the presence of a flaw is predicted predicted by analytical analytical means (in the case of the USR) or using finite element analysis (for the skirt). In each each case, the flaw size used in these calculations is increased to ensure conservative conservative estimates estimates (for example, in the case of the skirt flaws extending extending up to Y2 1/22 the panel width are considered). For the USR, the change in modal frequencies due to the presence of the cracks is less than 0.5%. For the skirt, using a conservative conservative estimate for the crack to panel width of 0.3 (the measured value is less than 0.17) the change change in modal frequency is also less than 0.5%. In In both cases such small changes in modal frequencies frequencies are considers negligible considers negligible and are readily accounted accounted for when performing frequency shifting.

Simplifications 3.3 Model Simplifications The following simplifications simplifications were were made to achieve reasonable model size while maintaining maintaining good modeling fidelity for key structural properties:

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• ** Perforated plates were approximated as continuous plates using modified elastic properties properties designed to match the static and modal behaviors of the perforated plates. The perforated plate structural

• " The drying vanes structural modeling is summarized in Section 3.4 and Appendix vanes were replaced replaced by point masses Appendix C of [9].

masses attached to the corresponding trough

[9].

bottom plates and vane bank top covers covers (Figure (Figure 4). The bounding perforated plates, vane bounding perforated bank end plates, and vane bank top covers covers were explicitly explicitly modeled (see (see Section 3.5).

3.5).

• " The added mass properties properties of the lower lower part of the skirt below the reactor reactor water level were obtained hydrodynamic analysis (see Section 3.6).

obtained using a separate hydrodynamic

• ((

(3)))

• Four steam dryer support brackets brackets that are located located on the reactor vessel and spaced at 90° 90' intervals were explicitly modeled (see Section 3.9).

• Most welds were node-to-node connections; were replaced by node-to-node interconnected parts share connections; interconnected common nodes along the welds. In other other locations locations the constraint constraint equations equations between nodal degrees degrees of freedom were introduced as described in Section 3.9.

• 3.4 Perforated Perforated Plate Model The perforated properties.

perforated plates were modeled as solid plates with adjusted properties. Properties of the perforated perforation. Based on [10],

perforated plates were assigned

[10], for an equilateral effective moduli of elasticity the effective elasticity were adjusted elastic and dynamic assigned according equilateral square pattern were found.

dynamic according to the type and size of pattern with given hole size and spacing, of The adjusted adjusted properties for the perforated plates are shown in Table 2 as ratios to material properties of structural steel, steel, provided in Table 1. 1. Locations of perforated plates are classified by steam entry / exit vane bank side and vertiCal vertical position.

Tests were carried out to verify that this representation representation of perforated perforated plates by continuous ones with modified elastic properties preserves the modal propertiesproperties of the structure. These These tests are summarized summarized in Appendix C of [9]and compare compare the predicted first modal frequency for a cantilevered cantilevered perforated perforated plate against an experimentally experimentally measured measured value. The prediction prediction was obtained obtained for 40%

40% and 13%

13% open area plates (these are representative representative of the largest and lowest lowest open area ratios of the perforated plates at NMP2, as seen in Table Table 2) using the analytical formula for a cantilevered cantilevered plate and the modified Young's modulus and Poisson's ratio given by O'Donnell O'Donnell[10].[10]. The measured and predicted predicted frequencies are in close agreement, differing differing by less than 3%.

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(3)))

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• ((

Table 2. Material properties properties of perforated plates.

(3)))

3.5 Vane Bank Model The vane bank assemblies consist of many vertical angled plates that are computationally computationally expensive to model explicitly, explicitly, since a prohibitive prohibitive number of elements would be required. These parts have significant weight which is transmitted transmitted through the surrounding structure, so it is important important to capture capture their gross inertial properties. Here the vane banks are modeled as a collection of point masses located collection located at the center of mass for each vane bank section (Figure 4). 4) .

The following masses were used for the vane bank sections, based on data found on provided drawings:

inner banks, 1618 Ibm, 4 sections per bank; middle banks, 1485 Ibm, total 4 sections per bank; and outer banks, 1550 Ibm, 3 sections per bank.

These masses masses were applied to the base plates and vane top covers using the standard ANSYS point mass modeling point modeling option, element MASS21. ANSYS automatically element MASS21. automatically distributes the point mass inertial loads to the nodes of the selected structure.

structure. The distribution algorithm minimizes the sum of the squares of the nodal inertial forces, while ensuring that the net forces and moments are conserved. Vane banks are not exposed to main steam lines directly, but rather shielded by the hoods.

the hoods.

The The collective collective stiffness of the vane banks is expected to be small compared compared to the surrounding support structure and is neglected surrounding support neglected in the model. In the static case it is reasonable to expect that this constitutes constitutes a conservative conservative approach, since neglecting the stiffness of the vane banks implies that the entire weight is transmitted through the adjacent adjacent vane bank walls and supports. In the dynamic dynamic case the vane banks exhibit only a weak response since (i) (i) they have large inertia so that the characteristic characteristic acoustically-induced acoustically-induced forces divided by the vane masses masses and inertias yield small amplitude motions, velocities and accelerations; accelerations; and (ii)

(ii) they are shielded from acoustic loads by the hoods, which which transfer dynamic loads to the rest of the structure. compared to the hoods, less motion is anticipated structure. Thus, compared anticipated on the vane banks so that 15 15

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.' approximating approximating their inertial properties with equivalent point masses is justified. Nevertheless, the bounding parts, such as perforated plates, side panels, and top covers, are retained model, modeL Errors associated with the point mass representation for by frequency shifting of the applied loads.

Nevertheless, retained in the representation of the vane banks are compensated compensated 3.6 Water Inertia Effect on Submerged Submerged Panels Water inertia inertia was modeled by an increase increase in density of the submerged submerged structure structure to account for the added hydrodynamic hydrodynamic mass. This added mass was found by a separate hydrodynamic hydrodynamic 2

analysis (included (included in DRF-C-279C DRF-C-279C supporting this report) to be 0.143 lbm/in Ibm/in on the submerged submerged skirt area. This is modeled by effectively effectively increasing the material density for the submerged submerged portions of the skirt. Since the skirt is 0.25 inches thick, the added mass is equivalent to a increase by 0.572 Ibm/in 33 . This added water mass was included density increase included in the ANSYS model by appropriately modifying the density of the submerged appropriately structural submerged structural elements when computing computing harmonic response. For the static stresses, the unmodified density of steel is used throughout.

3.7 Structural Structural Damping Structural damping was defined as 11%  % of critical damping for all frequencies.

frequencies. This damping is consistent consistent with guidance given on pg. 10 of NRC RG-l.20 RG-1.20 [11].

3.8 Mesh DetaiJs Details and Element Types Shell elements elements were were employed employed to model the skirt, hoods, perforatedperforated plates, side and end plates, trough bottom plates, reinforcements, reinforcements, base plates and cover plates. Specifically, Specifically, the four-node, Shell Element SHELL63, SHELL63, was selected to model these structural components. This element models bending and membrane stresses, but omits transverse shear. The use of shell elements is appropriate appropriate for most of the structure structure where the characteristic characteristic thickness is small compared to the other plate dimensions. For thicker structures, such as the upper and lower support rings, solid brick elements were used to provide the full 3D stress. The elements SURF 154 are used to assure proper application of pressure pressure loading to the structure. Mesh details and element element types are shown in Table 3 and Table 4.

The mesh is generated generated automatically automatically by ANSYS with refinement near edges. The maximum allowable allowable mesh spacing is specified specified by the user. Here a 2.5 inch maximum allowable spacing is is specified with refinement refinement up to 1.5 inch in the following areas: drain pipes, tie rods, the curved curved portions of the drain channels and the hoods. Details of the finite element element mesh are shown in Figure 5. Numerical experiments experiments carried carried out using the ANSYS code applied to simple analytically tractable analytically tractable plate structures structures with dimensions and mesh spacings similar to the ones used used for the steam dryer, confirm that the natural frequencies are accurately recovered (less than 11%  %

errors for the first modes). These errors are compensated compensated for by the use of frequency shifting.

3.9 Connections Between Structural Components Between Structural Most connections connections between parts are modeled modeled as node-to-node node-to-node connections. This is the correct manner (i.e.,

(i.e., within the finite element element framework) of joining joining elements elements away from discontinuities. At joints between shells, this approach omits the additional stiffness provided by the extra extra weld material. Also, locally 3D effects are more pronounced. pronounced. The latter effect is accounted for using weld factors. The deviation in stiffness stiffness due to weld material is negligible, negligible, since weld dimensions are on the order of the shell thickness. The consequences consequences upon modal 16

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• frequencies and amplitude are, to first order, proportional characteristic shell length. The errors committed characteristic small and readily compensated compensated for by performing proportional to tIL committed by ignoring performing frequency shifts.

When joining shell and solid elements, t/L where t is the thickness and L a ignoring additional weld stiffness stiffness are thus elements, however, the problem arises of properly constraining constraining the rotations, since shell element nodes contain both displacement displacement and rotational degrees of degrees of freedom at every node whereas solid elements model only the translations. translations. A node-to-node effectively appear to the shell element connection would effectively element as a simply supported, rather than (the restraint and significantly alter the dynamic response cantilevered restraint correct) cantilevered response of the shell structure.

To address this problem, constraint constraint equations are used to properly connect connect adjacent shell- and solid-element modeled solid-element modeled structures. Basically, Basically, all such constraints constraints express the deflection deflection (and rotation for shell elements) of a node, RI, R 1 , on one structural component component in terms of the deflections/rotations of the corresponding deflections/rotations corresponding point, P 2 , on the other connected P2, connected component.

component.

Specifically, the element containing Specifically, P2 is identified containing P2 identified and the deformations at P2 P2 determined determined by interpolation between interpolation between the element nodes. The following types of shell-solid element connections connections are used in the steam dryer model including the following:

1. Connections of shell faces to solid faces (Figure 6a). While only displacement

1. displacement degrees of of freedom are explicitly constrained, this approach also implicitly constrains the rotational degrees of freedom when multiple shell nodes on a sufficiently dense grid are connected connected to the same solid face.

2. Connections (e.g., connection Connections of shell edges to solids (e.g., connection of the bottom of closure plates with the upper ring). Since solid elements do not have rotational degrees of freedom, the coupling approach consisted of having the shell penetrate penetrate into the solid by one shell thickness and then constraining both the embedded embedded shell element nodes (inside the solid) and the ones located on the surface of the solid structure (see Figure 6b). NumericalNumerical tests involving simple structures structures showed that this approach approach and penetration penetration depth reproduce both the deflections and stresses of the same structure structure modeled using only solid elements or ANSYS' bonded contact technology. Continuity of rotations and displacements displacements is achieved.

The use of constraint conditions conditions rather than the bonded contacts advocatedadvocated by ANSYS for connecting independently connecting independently meshed components confers meshed structural components confers better accuracy accuracy and useful numerical advantages numerical advantages to the structural analysis of the steam dryer including better conditioned conditioned and smaller smaller matrices. The smaller size results from the fact that equations equations and degrees of of freedom are eliminated rather than augmented augmented (in Lagrange multiplier-based Lagrange multiplier-based methods) by additional degrees degrees of freedom. Also, the implementation implementation of contact elements relies on the use of of very high stiffness elements (in penalty function-based function-based implementations) implementations) or results in indefinite matrices (Lagrange multiplier implementations) implementations) with poorer convergence convergence behavior compared compared to positive definite matrices.

The steam dryer rests on four support blocks which resist vertical and lateral displacement.

The support blocks contact contact the seismic blocks welded welded to the USR so that 100% 100% of the dryer weight is transmitted through the seismic blocks per the FDDR KGl-265. Because Because the contact contact

• region between the blocks and steam dryer is small, the seismic blocks are considered free to 17 17

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• rotate about the radial axis. Specifically way halfway to the Specifically nodal constraints (zero relative displacement) imposed over the contact area between between the seismic blocks and block surface facing the vessel and the other node is 0.5" steam dryer, half nearest upper support ring node. This arrangement displacement) are the support blocks. Two nodes on andthe each support block are fixed as indicated in Figure 7. One node is at the center of the support 0.5" offset inside the block towards the arrangement approximates approximates the nonlinear nonlinear contact condition where the ring can tip about the block.

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• U CE CE Point masses Masses are connected connected to top and bottom supports Gussets Gussets to lifting rods connections A --

Skirt to support support rings connections connections Simply supported restraints

/

• Figure 4. Point masses representing and nodes and ((

representing the vanes. The pink shading represents equations between nodes are applied (generally represents where constraint (generally between solid and shell elements, fl).

(3)))).

constraint elements, point masses masses Table Table 3. FE Model Model Summary.

Summary.

Description I Quantity Description Nodes11 1 159,793 Total Nodes 159,793 I Total Total Elements 1 124,496 1

1. Not including including additional additional damper damper nodes and elements.

Table 4. Listing of Element Types.

Generic Element Element TTypee Name Element Name ANSYS ANSYSName Name 20-Node Quadratic uadratic Hexahedron Hexahedron SOLID 186 SOLID186 20-Node Hexahedral Structural Solid 10-Node Quadratic 10-Node uadratic Tetrahedron Tetrahedron SOLID 187 SOLID187 10-Node Tetrahedral 10-Node Tetrahedral Structural Solid 4-Node Elastic Shell SHELL63 SHELL63 4-Node 4-Node Elastic Shell Shell Element Mass Element MASS21 Structural Structural Mass Pressure Surface Surface Definition SURF SURF 154 I 54 3D Structural Surface Effect Damper Dam er element element COMBIN14 COMBIN14 Spring-Damper

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• 5a. Mesh overview.

Figure Sa. overview .

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• Figure 5b. Close up of mesh showing on-site modifications.

modifications .

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• supports..

5c. Close up of mesh showing drain pipes and hood supports Figure 5c.

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• Figure Figure 5d. Close up of mesh showing showing node-to-node node-to-node connections connections between between various plates plates..

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• Figure Figure 5e. Close up of mesh showing channels; channels; hood showing node-to-node hood supports and hoods; and other parts.

parts .

connections between the skirt and drain node-to-node connections drain

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• 5f. Close up view of tie bars.

Figure Sf. bars .

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• Shell nodes DOF are related to solid element shape functions Shell elements Surface of solid element element Figure 6a. Face-to-face Face-to-face shell to solid connection.

Shell nodes DOF are related to solid element shape functions Additional shell elemen Surface of solid element element Figure 6b. Shell edge-to-solid edge-to-solid face connection. connection .

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Information This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Upper support ring Free rotation axis Seismic block Support block Fixed displacement nodes conditions. Inside node is half way between outer surface Figure 7. Boundary conditions. block surface of support block and upper support ring.

support ring .

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• 3.10 Pressure Loading Loading The harmonic loads are produced by the pressures acting steam dryer. At every X-, y- and z-directions) acting on the exposed surfaces of the every frequency and for each MSL, the pressure distribution corresponding z-diredions) that is superimposed corresponding to a unit pressure at the MSL inlet is represented on a three-inch grid lattice grid (i.e., a mesh whose lines are aligned with the x-, superimposed over the steam dryer dryer surface. This grid is compatible with the 'Table' format used by ANSYS to 'paint' general pressure pressure distributions upon structural surfaces. The pressures pressures are obtained obtained from the Helmholtz solver routine in the acoustic analysis [2]. .

In general, the lattice nodes do not lie on the surface, so that to obtain the pressure differences at the surface it is necessary to interpolate interpolate the pressure differences differences stored at the lattice nodes. This is done using simple linear interpolation interpolation between the 8 forming nodes of the

. lattice cell containing the surface point of interest. Inspection Inspection of the resulting pressures pressures at selected nodes shows that these pressures vary in a well-behaved well-behaved manner between the nodes with prescribed prescribed pressures. Graphical depictions depictions of the resulting comparisons between resulting pressures and comparisons between the peak pressures in the original original nodal histories and those in the final surface load distributions produced in ANSYS, all confirm that the load data are interpolatedinterpolated accurately accurately and transferred transferred correctly correctly to ANSYS.

The harmonic harmonic pressure pressure loads are only applied to surfaces above the water level, as indicated in Figure 8. 8. In addition to the pressure load, the static loading inducedinduced by the weight of the steam dryer is analyzed analyzed separately. The resulting static and harmonic harmonic stresses are linearly linearly combined to obtain total values which are then processed to calculate calculate maximum and alternating alternating stress intensities for assessment in Section 5.5.

((

(3)))

(3)))

This is This is useful useful since since revisions in the revisions in loads the loads model do not necessitate necessitate recalculation stresses..

recalculation of the unit stresses

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• NODE S NODES PRES-NORM PRE S-NOPIA J\N Sq

~z

• -. 101592 .000 030301

.040 99 668738 397447

. 397114 7

.1168738 .540029

. 540029 Figure 8a. Real part of unit pressure loading MSL A (in psid) on the steam dryer at 50.1 Hz. No loading is applied to the submerged surface and lifting rods rods..

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• NODE S NODES PRES-NORM PRES-NORM AN J\N

~z 3493

• Figure 8b. Real part of unit pressure loading MSL A (in

. 2956 71

.295671

. 394932

. 992.494193

.4 941 93 at 200.45 dryer at (in psid) on the steam dryer 200.45 Hz.Hz.

No loading is applied to the submerged surface and lifting rods rods..

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• The solution is decomposed the stress stress field induced induced by solution accounts for the harmonic the

4. Structural supported Structural Analysis decomposed into static and harmonic parts, structure supported structure subjected harmonic stress field due to the subjected parts, where the static to its own static solution produces weight weight the unit pressure of given and the given frequency produces harmonic frequency in one of the main main steam steam lines. All solutions solutions are linearly linearly combined, with amplitudes amplitudes provided provided by signal measurements measurements in each each steam line, to obtain obtain the final displacement displacement and stress stress time time histories.

histories. This decomposition decomposition facilitates facilitates the prescription prescription of the added mass mass model model accounting for hydrodynamic hydrodynamic interaction interaction and allows one to compare compare the stress stress contributions contributions arising from static static and and harmonic harmonic loads separately. Proper evaluation separately. Proper evaluation of the maximum membrane membrane and membrane+bending membrane+bending stresses stresses requires requires that the static loads loads due to weight weight be accounted accounted for. Hence Hence both static and harmonic harmonic analyses are carried carried out.

4.1 Static Analysis The results of the static analysis are shown in Figure Figure 9. The locations with highest stress include the inner inner vane vane bank connection to inner base plate bank connection plate near support brackets brackets with stress stress intensity 9,598 psi. ThereThere are four locations locations with artificial stress singularity, singularity, which are excluded excluded from the analysis. The static stresses stresses one node away are used at these locations locations as more realistic estimate of locai local stress. These locations are at the connections connections of the inner end plate to the inner inner base base plate at the ends of the cut-out, as shown in Figure 9c.

4.2 Harmonic Analysis

• The harmonic described harmonic pressure loads were applied to the structural described in Section 3.10. 3.1 O. Typical stress intensity Figure 10. Stresses were calculated for each calculations calculations were combined.

evaluate maximum stresses, the stress harmonics To evaluate structural model at all surface nodes intensity distributions over the structure harmonics including nodes structure are shown in each frequency, and results from static and harmonic including the static component are transformed transformed into a time history using FFT, and the maximum maximum and alternating stress intensitiesintensities for the response, evaluated.

response, evaluated., According to ASME B&PV Code, Section III, Subsection Subsection NG-3216.2 the following procedure was established to calculate alternating alternating stresses. For every node, the difference tensors, O'~

stress difference (16 = O'n(n -O'm

-(m, , are considered considered for all possible pairs of the stresses O'n a, and O'm am at different time levels, 1n tn and tm.tin. Note that all possible pairs require consideration since there are no "obvious" extrema in the stress responses. However, in order to contain computational cost, extensive screening of the pairs pairs takes place (see Section 2.3) 2.3) so that pairs known to produce alternating alternating stress intensities less than 500 psi are rejected. For each remaining stress difference tensor, the principal stresses S\, S1, SS2,2, S3 are computed computed and the maximum absolute value among principal stress differences, Srun Snm=max{ISI-S21,ISl-S31,1S2-S31},

=max {lSI - S21, lSI - S31, IS2 - s31}, obtained. The alternating stress at the node is then one-half the maximum value of Snm taken over all combinations (n,m), i.e., Salt = tmax{Srun}.

salt = lmax{S.}. This alternating 2

alternating stress is compared compared against allowable n,m n,m values, depending on the node location with respect to welds welds..

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• NODAL SOLUTION STEP=1 STEP=l SUB =1 TIME=l TIME=1 USUM USUM (AVG)

(AVG)

AN J\N RSYS=O RSYS=0 DMX =.068847

=.068847 SMN SMN =.505E-03

=.505E-03 SMX =.068847

=.068847

• .553. 008099

.505E-03 Figure 9a. Overview

.008099 Overview of static R 607.05366 static calculations showing displacements displacement (DMX) is 0.069". Note that displacements

.05366

.061254

.624.068847

.068847 displacements (in inches). Maximum displacements are amplified for visualization.

visualization .

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• AN J\N

• o 01000 Figure 9b. Overview of static calculations showing stress intensity (SMX) stress intensities (in (SMX) is 9,598 psi. Note that displacements 4000 (in psi). Maximum 5000 5000 Maximum stress displacements are amplified for visualization

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• Figure 9c. Stress singularities. Model is shown in wireframe clarity..

wireframe mode for clarity

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• NODAL NODAL SOLUTION STEP=1185 STEP=1185 SUB =1 J\N FREQ=50.418 FREQ=50.418 REAL ONLY SINT (AVG)

(AVG)

DMX =.195193

=.195193 SMN SMN =.081579

=.081579

=11642 SMX =11642 z

• .081579

.081579 1294 1294 2587

,9055 9055 10348 10348 11642 11642 10a. Overview of harmonic Figure lOa. harmonic calculations (in psi) calculations showing real part of stress intensities (in along with displacements. Unit loading MSL A at 50.1 Hz (oriented to show high stress locations displacements. Unit locations at the hoods).

hoods) .

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• NODAL SOLUTION NODAL STEP=305 SUB SUB =1 FREQ=200.

SOLUTI ON STEP= 30 5 4466 FRE Q=20 0.44 REAL REAL ONLY ONLY J\N SINT (AVG)

(AVG)

DMX =.021716 DMX =. 02 171 6 SMN =.

SMN 177944

= .17 7 9 44 SMX =5801

=580 1

~z

• Figure lOb.

.177944 644. 744 displacements. Unit loading MSL A at 200.5 Hz along with displacements. Hz..

4512 4 5157 5801 5801 calculations showing real part of stress intensities (in psi) 10b. Overview of harmonic calculations

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• 4.3 Post-Processing Post-Processing The static and transient stresses computed files for subsequent subsequent post-processing.

software to compute computed at every post-processing. These every node with ANSYS were exported exported into These files were then read into separate customized compute the maximum and alternating stresses at every node. The maximum stress stress was defined for each node as the largest largest stress intensity occurring occurring during the time history.

Alternating stresses stresses were calculated according were calculated according to the ASME standard described above. For shell elements the maximum stresses stresses were calculated calculated separately separately at the mid-plane, where only only membrane stress is present, and at top/bottom top/bottom of the shell, where bending stresses are also present.

For For nodes that are shared between several components or lie on junctions, several structural components junctions, the maximum and alternating alternating stress calculated as follows. First, the nodal stress stress intensities are calculated stress tensor is computed separately computed separately for each individual component individual component by averaging averaging over all finite elements meeting meeting at the node and belongingbelonging to the same structural component. The time histories of these stress tensors tensors are then processed to deduce the maximum and alternating stress intensities for each structural structural component.

component. Finally for nodes shared across multiple components components the highest of the component-wise component-wise maximum maximum and alternating stresses is recorded as the "nodal" stress. This approach approach prevents averaging of stresses across components and thus yields conservative estimates for nodal stresses conservative stresses at the weld locations where several several components components are joined together.

The maximum stresses are compared allowable values which depend upon the stress compared against allowable type (membrane, membrane+bending, alternating - Pm, Pm+Pb, Salt) and location (at a weld or (membrane, membrane+bending, or away from welds). These allowables allowables are specified in the following following section. For solid elements the most conservative allowable for membrane conservative allowable stress, Pm, is used, although bending stresses are membrane stress, nearly always present also. The structure structure is then assessed in terms of stress ratios formed by dividing allowables allowables by the computed computed stresses stresses at every node. Stress ratios less than unity imply imply that the associated associated maximum and/or alternating stress intensities exceed exceed the allowable levels.

Post-processing tools calculate the stress ratios, identifying the nodes with low stress ratios and generating generating files formatted for input to the 3D graphics program, TecPlot, which provides more general general and sophisticated plotting options than currently available available in ANSYS.

4.4 Computation of Stress Ratios for Structural Assessment Assessment The ASMIE ASME B&PVB&PV Code, Section III, subsection subsection NG provides different allowable stresses for different different load combinations and plant conditions. The stress levels of interest interest in this analysis are for the normal operating operating condition, which is the Level A service condition. The load combination combination for this condition is:

Normal Operating Operating Load Combination = = Weight + Pressure + Thermal The weight and fluctuating pressure contributions have been calculated in this analysis and are included in the stress stress results. The static pressure differences differences and thermal expansion expansion stresses are small, since the entire steam dryer is suspended small; suspended inside the reactor vessel and all surfaces surfaces are exposed exposed to the same conditions. Seismic Seismic loads only occur in Level Level B and C cases, and are not Band considered considered in this analysis analysis..

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• Allowable Stress Intensities maximum allowable Intensities The ASME B&PV Code,Section III, subsection NG shows the following (Table allowable stress intensity (Sm) and alternating stress intensity service condition. The allowable stress service intensity (Sa) stress intensity values for type 304 stainless for the (Table 5) for (Sa) for the Level A stainless steel at operating operating temperature 5507F 550°F are taken from Table 1-9.2.2 of Appendix Table 1-1.2 and Fig. 1-9.2.2 Appendix I of Section Section III, in the ASME B&PV Code. The calculation calculation for different stress categories is performed performed in accordance accordance with Fig. NG-3221-1 of Division I, SectionSection III, III, subsection NG.

Table 5. Maximum Allowable intensity and Alternating Allowable Stress Intensity Alternating Stress Intensity for all areas other than welds. The notation Pm represents represents membrane membrane stress; Pb represents stress secondary stresses (from thermal effects and gross due to bending; Q represents secondary structural structural discontinuities, discontinuities, for example); and FF represents represents additional stress increments (due to local structural discontinuities, for example).

Type TYl2e Notation Service Service Limit Allowable Value {ksQ (ksi)

Maximum Stress Allowables:

Membrane General Membrane Pm Sm 16.9 16.9 Membrane + Bending Pm + Pb Pm+Pb 1.5 Sm 25.35 25.35 Primary Primary + Secondary Secondary Pm + Pb + Q Pm+Pb+Q 3.0 Sm 3.0Sm 50.7 50.7 Alternating Stress Allowable:

Alternating Stress Peak == Primary + Secondary Secondary + F Salt Sa 13.6 13.6

• When evaluating welds, either the calculated or allowable stress was adjusted, to account for stress concentration concentration factor and weld quality. Specifically:

Specifically:

• • For maximum allowable allowable stress intensity, intensity, the allowable allowable value is decreased by multiplying its value in Table Table 5 by 0.55.

0.55.

• • For alternating alternating stress intensity, intensity, the calculated calculated weld stress intensity is multiplied multiplied by a weld stress intensity (fatigue) factor of 1.8, before comparison to the Sa value given above.

The weld factors of 0.55 and 1.8 were selectedselected based on the observable observable quality of the shop shop welds and liquid penetrant NDE testing of all welds (excluding (excluding tack and intermittent intermittent welds, which were were subject subject to 5X visual inspection) during fabrication. These factors are consistent consistent with fatigue strength reduction reduction factors recommended recommended by the WeldingWelding Research Council, [12], and Research Council,[12],

stress concentration concentration factors at welds, provided provided in [13] and [14]. In addition, critical welds are subject to periodical periodical visual inspections inspections in accordance accordance with the requirements of GE SIL 644 SIL and BWR VIP-139 VIP-139 [15]. Therefore, for weld stress intensities, the allowable values are shown in

[15]. Therefore, Table 6.

These factors (0.55 and 1.8) 1.8) also conservatively conservatively presume presume that the structure is joined joined using fillet welds unless specified specified otherwise. Since fillet welds correspond correspond to larger stressstress concentration factors than other types of welds, this assumption concentration assumption is a conservative conservative one.

one .

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• Type T~Ee Maximum Stress Allowables:

General Membrane

(}eneral~embrane Table 6. Weld Stress Intensities.

Notation Pm Intensities.

Service Limit Allowable 0.55 Sm Allowable Value {ksQ 9.30 9.30 (ksi)

~embrane + Bending Membrane Pm + Pb Pm+Pb 0.825 Sm 13.94 13.94 Primary Primary + Secondary Secondary Pm + Pb + Q Pm+Pb+Q 1.65 Sm 27.89 27.89 Alternating Stress Allowables:

Alternating Stress Allowables:

Secondary + F Peak = Primary + Secondary Peak Salt Sa 13.6 13.6 Comparison Calculatedand Allowable Stress Comparison of Calculated Stress Intensities Intensities The classification classification of stresses into general general membrane or membrane + bending types was made according to the exact location, where the stress intensity was calculated; namely, general membrane, membrane, Pm, for middle surface of shell element, and membrane membrane + bending, bending, Pm + Pb, for other locations. For solid elements the most conservative, conservative, general membrane, membrane, Pm, allowable is used.

The structural structural assessment assessment is carried out by computing stress ratios between the computed maximum and alternating stress intensities, and the allowable levels. Locations where any of the stresses exceed allowable allowable levels will have stress ratios less than unity. Since computation computation of of stress ratios and related related quantities time-consuming and awkward, a separate quantities within ANSYS is time-consuming separate

• FORTRAN FORTRAN code was developed to compute the necessary intensities, intensities, Pm, Pm+Pb, and Salt, computed at every node:

quantities were computed quantities

1. The maximum membrane 1.

necessary maximum and alternating stress Salt' and then compare it to allowables. Specifically, the following allowables. Specifically, membrane stress intensity, Pm (evaluated (evaluated at the mid-thickness mid-thickness location for shells),

2. The maximum membrane+bending membrane+bending stress intensity, Pm+Pb, (taken as the largest of the maximum stress intensity values at the bottom, top, and mid thickness locations, for shells),

3. The alternating

3. alternating stress, Salt' Salt, (the maximum value over the three thickness locationslocations isis taken).

4. The stress ratio due to a maximum stress intensity assuming the node lies at a non-weld location location (note that this is the minimum ratio obtained considering both membrane membrane stresses stresses and membrane+bending membrane+bending stresses):

SR-P(nw) = min{ Sm/Pm, SR-P(nw) SmlPm, 1.5

• Sm/(Pm+Pb) }.

5.

5. The alternating stress ratio assuming the node lies at a non-weld non-weld location, (1.1 ** Salt),

SR-a(nw) = Sa / (1.1

6. The same as 4, but assuming the node lies on a weld, SR-P(w)=SR-P(nw)

• 0.55 SR-P(w)=SR-P(nw)

7. The same as 5, but assuming the node lies on a weld, SR-a(w)=SR-a(nw) / 1.8 SR-a(w)=SR-a(nw) 1.8..

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• Note that in steps 4 and 6, The allowables allowables listed in 6, the minimum of the stress ratios based on Pm and Pm+Pb, is taken.

Table 6, Sm=16,900 psi and Sa=13,600 are the weld factors discussed above. The factor of 1.1 accounts moduli for the steel used in the steam dryer and the values allowable. According to NO-3222.4 NG-3222.4 in subsection NG subsection NO Sa=13,600 psi. The factors, 0.55 and 1.8, of accounts for the differences in Young's values assumed in alternating stress Section III of the ASME Code [1], [1], the effect of elastic modulus upon alternating alternating stresses stresses is taken into account by multiplying alternating stress Salt at all locations by the ratio, E/Emodel=l.

ElEmodeJ= 1.1,1, where:

E= = 28.3 101066 psi, as shown on Fig. 1-9.2.2. ASME BP&V Code Emodel == 25.55 10 1066 psi (Table 1)

The appropriate maximum and alternating stress ratios, SR-P and SR-a, are thus determined and a final listing of nodes having the smallest stress ratios is generated.

generated. The nodes with With stress ratios lower than 4 are plotted in TecPlot (a 3D graphics engineering graphics plotting program widely used in engineering tabulated and depicted in the following Results Section.

[16]). These nodes are tabulated communities [16]).

Finally, at a limited number of weld locations (specifically (specifically the vertical hood reinforcement reinforcement strip), estimates of the 'nominal' membrane membrane+bending stresses is taken by finding membrane and membrane+bending the maximum stress at all of the surrounding surrounding non-weld element nodes. This stress is then then multiplied by a weld factor of f=4.0 in accordance mUltiplied accordance with the ASME code (Table NG-3352-1). NO-3352-1).

This is the appropriate weld factor for nominal stresses stresses evaluated near, but off the weld and is to be distinguished from the 1.8 (fillet welds) or 1.4 (full penetration welds) weld factors applied to linearized stresses evaluated evaluated on the weld. This processing processing of weld stresses is consistent with prior approaches in industry (e.g., [17], [17], specifically specifically Figure 6-46, pg. 112). 112). (Note that the definition of 'nominal' characteristic stress in the plate or shell stress is here understood as the characteristic

'nominal'stress without the localized influence of reinforcements without reinforcements or other discontinuities.

discontinuities. This definition is not explicitly given in the ASME code which was originally originally assembled assembled before finite element element modeling methods were routinely used and simplified or textbook calculation calculation methods were normative. However, these simplified calculations generally generally predicted predicted stresses that are in good agreement with the finite element stresses away from junctions. Using neighboring node off-agreement off-weld stresses to represent the nominal stresses is thus reasonablereasonable for engineering application).

4.5 Finite Element Sub-modeling Sub-modeling In order to meet target stress levels at EPU in the NMP2 steam dryer modifications are needed. These consist of stiffening the closure plates (see (see Appendix A) and reinforcing reinforcing welds at two locations: (i) the top 18" of the welds connecting connecting the closure plates to the hoods and vane banks and (ii)

(ii) the weld between the vane bank side plates and lifting rod support brace. These weld reinforcements reinforcements are developed using high resolution solid element-based element-based sub-models sub-models of of these locations. The use of localized localized sub-models is motivated motivated by the need to maintain computational costs at a feasible level. To this end the global steam dryer model is computational is predominantly comprised comprised of shell elements. These elements are well suited for structures such as the steam dryer consisting consisting of shell-like components components and tend to produce conservative conservative estimates estimates of the stresses. In some cases however, such as welded junctions junctions involving multiple components, components, shell element element models can overestimate overestimate the nominal stress intensities in the vicinity of the junctions. In such cases a more refined analysis analysis using solid elements to capture capture the complete 3D stress distribution, is warranted. Therefore, Therefore, to efficiently complex efficiently analyze complex 40 40

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• structures such as steam dryers, a standard engineering using a shell-based model. Locations Locations solid elements to obtain a more definitive with engineering practice is to first analyze the structure high stresses are examined in greater detail using 3D definitive stress prediction.

The solid element-based sub-modeling sub-modeling follows the procedure outlined in Appendix A (also Appendix A of [19])

[18] and AppendixAof [19]) and validated in against both high resolution resolution solid models of the full structure and sub-structuring sub-structuring results in [20] and [21]. [21]. Based on these models, the nominal stress intensities computed computed by the 3D solid element model are lower than those obtained obtained with the shell-based FEA used to analyze the complete shell-based complete steam dryer by the stress reduction factors (SRFs) summarized in Table 7. Note that the SRFs vary according summarized according to location being being dependent dependent on the individual geometry and also the general loading characteristics.

characteristics. They are generally generally less than unity due to conservative conservative stress estimates estimates in the shell-based shell-based weld stresses. For example the discontinuity stresses stresses computed in a shell model at a weld joint between between two orthogonal members are often quite conservative conservative because the shell element depiction does not provide any credit for the stress distribution associated with the specific specific weld geometry. Once the SRFs are obtained, the stress stress intensities predicted predicted by the global shell element-based element-based analysis at these locations are first multiplied by these SRFs to obtain more accurate accurate estimates of the nominal stresses. These are then multiplied by the 1.8 weld factor before comparing against allowable before comparing*

stress limits to obtain the alternating stress ratios.

Detailed 3D solid element sub-models sub-models are applied at both the weld reinforcements reinforcements and additional locations locations (see Table 77 for a complete complete list). For the closure plate the welds connecting connecting the closure plate to the vane banks and hoods experience experience significant significant vibratory vibratory stresses due to a plate response in the 125-135 Hz frequency frequency range. Though stresses remainremain well above above allowable allowable levels for all frequency frequency shifts at both CLTP and EPU, the margin is below the target level (i.e.,

(i.e., a stress ratio of SR-a=2.0 SR-a=2.0 at EPU). Therefore, Therefore, the closure plate was reinforced reinforced and a sub-model sub-model developed for each of the locations on the closure plates where stresses exceeded exceeded target levels.

On each closure plate there are four such locations. The first two are on the vertical weld joining the closure plate to the vane bank. The first node is at the top of this weld and the second one 13.5" below it. The other two locations are on the curved weld connecting the closure plate lies 13.5" to the curved hood. Again Again the first location is at the top of this weld and the second second one lies 14.5" below it. In both cases, 14.5" cases, the stresses at the top location location result from a combination of of membrane and bending stresses whereas the stresses at the lower locations locations are predominantly predominantly due to bending. The stresses are induced by a closure plate response dominated dominated by a (1,2)

(1,2) mode (i.e.,

(i.e., the mode shape resembles the first mode of a beambeam in the horizontal direction and the second mode in the vertical sense) which explains explains the high stress at the lower locations on the welds. Sub-model Sub-model calculations calculations at these locations locations show that to achieve achieve the required required target stress levels, an interior interior weld must be added along the top 18" 18" of each weld thus effectively converting converting it from a single-sided single-sided to a double-sided double-sided fillet weld along this length. Additional details are given in Appendix A.

Sub-modeling is also applied to analyze the stresses in the lifting rod support brace where it Sub-modeling connects connects to the vane bank side plate [22]. A sub-modeling sub-modeling analysis analysis of the high stress location location shows that for the current 11/4" current 1,4" double-sided fillet weld the stress reduction reduction is minimal. Repeating the sub-model analysis with an increased increased weld of 112" 1/2" resulted in a stress reduction reduction factor of of 0.60. To meet EPU target stress levels it is recommended recommended to increase the weld to this size size..

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• The other locations where sub-modeling was performed performed are listed as locations 6-9 in Table 7 and involve hood/hood support weld and the bottom of this weld where it meets the base plate junction as well as two locations near tie bar ends involving large welds that are not accounted for in the shell model. The locations of all sub-models sub-models are depicted depicted in Figure 11.

accounted

11. Additional details of sub-models evaluated evaluated for locations away from the closure plate are given in [22]

[22]..

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• Table 7.

7. Summary Summary of stress reduction factors obtained using sub-model Location Location sub-model analysis.

+

Factor Factor Reduction Stress Reduction

1. Top of vertical closure plate/vane bank weld I. 0.62 (Appendix A)

(Appendix A)

2. 14.5" 14.5" below below location 3 on the same weld 0.71 (Appendix A)

L 3. Top of closure plate/hood platelhood weld (Appendix A) 0.86 0.86 (Appendix (Appendix A)

4. 13.5" 13.5" below below location 1 on the same weld 0.88 (Appendix A)

5. Lifting rod support brace/vane

5. brace/vane side plate junction 0.60 [22]

(assuming (assuming an increased 1/2" weld) increased 112" hood/hood support weld at junction 0.79 [18]

6. Bottom of hoodlhood with base plate

-4 i_______________

7. Hoodlhood

7. Hood/hood support 0.77 [19]

8. Side plate/top plate 0.70 [22]

9. Tie bar/top vane bank plate. 0.71 [22]

Note: For locations 1-4 it is assumed that an inner weld has been to the top 18" 18" of the welds welds joining the closure closure plate to the hoods or vane banks, thereby replacing the existing single-sidedsingle-sided fillet weld by one that is double sided.

sided. Also, an increased V2"

\12" weld is assumed for location 55..

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This Document Does Not Contain Document Does Dynamics, Inc.

Contain Continuum Dynamics, Proprietary Information Inc. Proprietary Information associated attachment welds examined with sub-model in 1 a. Closure plates and associated Figure lla.

Appendix A (note lifting rods and other components modeled with solid elements are omitted for clarity). Sub-models on the perimeter are locations 1-4 in Table 77..

• 44

Information Continuum Dynamics, Inc. Proprietary Information This Document Does Not Contain Continuum 11 b. Location of node on inner hood/hood support/middle Figure II analyzed with plate weld analyzed support/middle base plate with sub-model in [22]. Sub-model corresponds to location 5 in Table 7.

7.

• ft-x y

c. Location of node on hoodlhood 1 Ic.

Figure 11 hood/hood supportlbase sub-model in support/base plate weld analyzed with sub-model corresponds to location 6 in Table 77..

[18]. Sub-model corresponds

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This Document Document Does Not Contain Continuum Dynamics, Dynamics, Inc. Proprietary Information Proprietary Information Figure lId.

lId. Location Location of node on hoodlhood hood/hood support weld analyzed with sub-model analysis procedure in [19]. Sub-model procedure Sub-model corresponds corresponds to location 7 in Table 77..

Figure 11lIe.

e. Location of node on side plate/top plate weld analyzed with sub-model sub-model analysis analysis procedure procedure in [22]. Sub-model corresponds to location Sub-model corresponds location 8 in Table 7.

7.

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• Figure 11 f.

f. Location of node on tie bar/top vane bank plate weld analyzed with sub-model analysis procedure procedure in [22]. Sub-model Sub-model corresponds to location 9 in Table 77..

sub-model

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• The The stress stress intensities intensities and and associated acoustic/hydrodynamic loads [3] with associated acoustic/hydrodynamic presented below. The bias due to finite frequency presented

5. Results associated stress stress ratios ratios resulting resulting from the associated biases and uncertainties Rev. 4 the Rev.

uncertainties factored in, are discretization and uncertainty frequency discretization associated with uncertainty associated model the finite element model itself, are also factored factored in. In In the following sections the following sections the highest highest maximum and alternating alternating stress intensities are presented stress intensities indicate which points on the dryer presented to indicate dryer experience experience significant concentration and/or modal significant stress concentration modal response (Section 5.1). The response (Section The lowest lowest stress ratios ratios obtained comparing the obtained by comparing the stresses against allowable values, stresses against values, accounting accounting for stress stress type (maximum alternating) and location (on or away from a weld), are also reported (maximum and alternating) reported (Section 5.2).

(Section Finally the frequency dependence 5.2). Finally dependence of the stresses nodes experiencing stresse~ at nodes experiencing the lowest lowest depicted in the form of accumulative stress ratios is depicted accumulative PSDs (Section 5.3).

(Section 5.3).

In each section results are presented both at nominal conditions conditions (no frequency shift) and with specified otherwise, frequency shifts are generally performed frequency shift included. Unless specified performed at 2.5% increments.

2.5% increments. The tabulated stresses stresses and stress stress ratios are obtained obtained using a 'blanking' procedure that is designed to prevent procedure prevent reporting a large number of high stress nodes nodes from from essentially the same location on the structure. In the case of stress intensities intensities this procedure procedure is as stress intensities are first computed at every node and then nodes sorted follows. The relevant stress highest stress node is noted and all neighboring according to stress level. The highest neighboring nodes within 10 10 inches of the highest stress symmetric images (i.e.,

stress node and its symmetric (i.e., reflections across the x=0 x=O and and y=0 planes) y=O "blanked" (i.e., excluded from the search for subsequent planes) are "blanked" subsequent high stress locations).

• Of the remaining highest stress node is identified and its neighbors (closer than remaining nodes, the next highest inches) blanked. The third highest stress node is similarly 10 inches) similarly located and the search continued in this fashion until all nodes are either blanked or have stresses less than half the highest value on the structure. For stress ratios, an analogous blanking procedure particular type in a 10" neighborhood stress ratio of a particular procedure is applied. Thus the lowest neighborhood and its symmetric symmetric images is identified and all other nodes in these regions excluded from listing in the table. Of the remaining nodes, the on reported and its neighboring points similarly one with the lowest stress ratio is reported similarly excluded, and so so blanked or have a stress ratio higher than 4.

on until all nodes are either blanked The measured CL CLTP significant contributions TP strain gage signals contain significant contributions from non-acoustic sources such as sensor noise, MSL turbulence and pipe bending vibration that contribute to the hoop strain measurements. The ACM analysis does not distinguish between the acoustic and non-acoustic fluctuations in the MSL signals that could lead to sizeable, but fictitious acoustic non-acoustic loads and resulting stresses on the dryer. One way to filter these fictitious loads is to collect data with the system maintained maintained at operating pressure (1000 (1000 psi) and temperature, but low power operating the recirculation pumps at this condition, the background

[23]. By operating background plant noise and vibrations remain present. At these conditions the acoustic loads are known to be negligible so that collected data, referred to as the low power data, originate entirely from non-acoustic sources such as sensor noise and mechanical vibrations. This information is valuable since itit allows one to now distinguish between the acoustic and non-acoustic content in the CL CLTP TP signal and therefore modify the CL CLTP TP loads so that only the acoustic component is retained. In previous analyses of the similar dryers, these low power signals were subtracted subtracted..

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• In the present implementation reason for retaining implementation however, no filtering using low power retaining noise in this particular particular case is to avoid protracted subtraction process and to thus expedite to justify power data is performed. The protracted review of the low power qualification of the dryer. Thus, rather than attempting expedite qualification justify the use of low power noise subtraction in this case, it was decided to use the CL signal (and by extension the EPU signals) directly without noise filtering. Therefore power CLTP Therefore for all TP results presented presented herein, no noise filtering using low power data has been performed. performed.

The applied load includes includes all biases and uncertainties uncertainties for both the ACM (summarized in [3])

and the FEM. For the latter there are three main contributors contributors to the bias and uncertainty.

uncertainty. The first is an uncertainty uncertainty (25.26%) that accounts for modeling idealizations idealizations (e.g.,

(e.g., vane bank mass model), geometrical geometrical approximations approximations and other discrepancies discrepancies between between the modeled and actual dryer such as neglecting of weld mass and stiffness in the FEA. The second second contributor contributor is a bias of 9.53% accounting for discretization 9.53% accounting discretization errors associated associated with using a finite size mesh, upon computed computed stresses. The third contributor contributor is also a bias and compensates compensates for the use of a finite discretization discretization schedule in the construction construction of the unit solutions. The frequencies frequencies are spaced such such that at 11%% damping the maximum maximum (worst case) error in a resonance resonance peak is 5%. The average error for this frequency schedule is 1.72%.

1.72%.

It is significant significant to note that the applied loads reflect revised revised bias and uncertainty values over over new frequency intervals: 60-70 Hz and 70-100 Hz. The higher bias and uncertainty values in the 60-70 Hz range strongly influence influence the limiting stresses values, but are also overly conservative.

conservative.

This is because when specifying new frequency intervals the ACM should be recalibrated over recalibrated over these intervals before calculating the bias and uncertainty before calculating uncertainty values. BecauseBecause it is resource-resource-intensive and would constitute constitute further revisions to the ACM model (to Rev. 5) this model re-calibration calibration was not performed. Consequently Consequently the revised biases and uncertainties uncertainties are higher than they would be if the ACM had been matched matched to data over the new intervals.

5.1 General Stress Distribution and High Stress Locations. Locations The maximum maximum stress intensities obtained by post-processing post-processing the ANSYS stress histories for CLTP CL TP at nominal frequency and with frequency shift operating operating conditions conditions are listed in Table 8. 8.

Contour plots of the stress intensities over the steam dryer structure are shown on Figure 12 12 (nominal frequency) and Figure 13 (maximum stress over all nine frequency shifts including nominal).

nominal). The figures are oriented to emphasize the high stress regions. Note that these stress intensities do not account for weld factors but include end-to-end bias and uncertainty. Further, it should be noted that since the allowable stresses vary with location, stress intensities do not necessarily correspond to regions of primary structural concern. Instead, necessarily correspond Inste!ld, structural evaluation evaluation is is more accurately accurately made in terms of the stress ratios which compare compare the computed computed stresses to allowable levels with due account account made for stress type and weld. ComparisonsComparisons on the basis of of stress ratios are made in Section 5.2.

The maximum stress intensities in most areas are low (less than 500 psi). For the membrane membrane stresses (Pm) the high stress regions tend to occur at: (i) (i) the bottom of the central vertical side plate that joins the innermost vane banks (stress (stress concentrations concentrations occur where this plate is welded to the inner base plates resting on the upper support ring); (ii) (ii) the welds joining the tie bars to the top cover piates plates on the vane banks; (iii)

(iii) the seismic blocks that rest on the steam dryer supports; and (iv) junctions connecting the bottoms of the hood supports. Except for the last location, the junctions connecting 49 49

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• stresses are dominated by the static contribution contribution as can be inferred deadweight is transmitted, the closure plates connecting deadweight banks, and various localized localized concentrations inferred from the small alternating stress intensities (Salt) tabulated in Table 8 for the high Pm locations. From Figure 12a and Figure 13a 13a higher Pm regions are seen to be in the vicinity alternating vicinity of the supports where all of the dryer connecting the inner hoods to the middle vane concentrations such those along the bottom of the outer hood.

dryer The membrane membrane + bending stress (Pm+Pb) distributions evidence a more pronounced pronounced modal response especially especially on the hood structures. The two locations with the highest stress intensities intensities of this type are the same pair having the highest membrane stress and are dominated by deadweight. High stress concentration concentration is also recorded on the top edge of this vertical plate where it joins to the inner vane bank. Other areas with high Pm+Pb stress concentrations concentrations include: (i) include: (i) the tops of the closure plates where they are welded to a hood or vane bank end plates; (ii) the skirt/drain channel welds; (iii) (iii) the outer cover plates connecting to the upper upper support ring and bottom of the outer hoods; and (iv) the common junction between each hood, its hood support (or stiffener), and the adjoining base plate (see Figure 13c). 13c).

The alternating alternating stress, Salt, distributions are most pronounced pronounced on the outer hoods directlydirectly exposed exposed to the MSL inlet acoustics, and on welds involving the closure plates. All hoods exhibit exhibit a strong response (e.g., Figure 13d). The highest stress intensity response (e.g., intensity at any frequency frequency shift occurs occurs at the middle hood. Though not exposed directly to the MSL acoustic sources, the interior hoods are thinner and their response is driven mainly by structural structural coupling rather than direct forcing.

Numerous weld locations also show significant stress including the bottoms of drain channels channels

• and the junctions junctions between the hoods, hood supports and base plates. These locations are characterized characterized by localized stress concentrations high stress locations intensities include include the tietie bar/top concentrations as indicated in Figure 13e and have emerged bar/top cover cover plate plate weld and welds welds involving involving the closure plate.

Comparing the nominal results (Table 8a) and results with frequency shifting it can be seen Comparing emerged as steam-dryers also. Other locations with high alternating stress locations in other steam-dryers that maximum stress intensities, Pm and Pm+Pb, do not differ significantly. significantly. The highest alternating alternating stress is approximately approximately 4.2%4.2% higher when frequency shifts are considered. For other nodes however the variations are higher. As shown shown in the next section, section, all stresses are well within allowable levels levels..

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• Table Sa. predicted stress intensities for CL CLTP TP conditions with no frequency frequency shift.

Stress Location Weld Location (inf)

(in) node(a) node(a) Stress Intensities Intensities (psi)

(psi)

Category x y z Pm Pm+Pb Salt Salt Pm Inner Inner Side Plate No 3.1 119 0.5 37229 7475 8836 8836 460

" Side Plate Ext/Inner Base Plate Yes 16.3 119 0 94143 94143 6913 9809 9809 438

" Upper Upper Support Ring/Support/Seismic Block Support Ring/Support/Seismic Yes -6.9

-6.9 -122.3

-122.3 -9.5 113554 6238 6238 911 911

" Tie Bar Yes 49.3 108.1 88 141275 5962 5962 807 807

" Hood Support/Middle Support/Middle Base Plate/Inner Plate/Inner Yes 39.9 -59.5 0 101435 5352 5488 1638 1638 Backing Bar/Inner Backing Bar/Inner Hood Hood Pm+Pb Pm+Pb Side Plate Ext/Inner Base Plate Yes 16.3 119 0 94143 94143 6913 9809 9809 438 438

" Inner Inrier Side Plate No 3.1 119 0.5 37229 7475 8836 8836 460

" Side Plate/Top Plate Yes 49.6 108.6 88 93256 93256 2505 8542 8542 1129 1129

" Middle Middle Base Plate/Inner Plate/Inner Backing Bar Out/Inner Yes -39.9 -108.6

-108.6 0 84197 84197 441 7227 1433 1433 Backing Backing Bar/Inner Hood Bar/Inner Hood

" Side Plate/Top Plate Yes 17.6 119 88 91215 91215 898 7174 1337 1337 Salt Salt Middle Middle Hood No -68.9 69.6 41.6 31054 1717 2759 2728 2728

" Hood Support/Inner Hood Support/Inner Hood Yes Yes 36.2 0 50.8 99529 975 2316 2290 2290

" Outer Hood Hood No -97.3 -50.7 62 78572 770 2160 2116 2116

"" Middle Middle Hood No -67.1 70.9* 54.5 70.9- 31441 1517 2099 2016

"" Hood Support/Inner Support/Inner Hood Yes 39.1 0 23 99515 842 2064 1977 1977 Notes.

(a) Node numbers are retained for further reference.

(1-9) Appropriate stress reduction factor for the welds and modifications (1-9) Appropriate modifications listed in Table 7 have been applied. The number refers to the particular location particular corresponding stress reduction factor in Table 7.

location and corresponding 51 51

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• Table 8b. Locations Locations with highest predicted predicted stress intensities taken taken over all frequency shifts CL CLTPTP conditions.

Stress Location Location Weld Location Location (in)

(in) node(a) Stress Intensities (psi) % Freq.

Category x y z Pm Pm Pm+Pb Salt Salt Shift Shift Pm Inner Inner Side Plate No 3.1 119 0.5 37229 7490 7490 9003 634 10

" Side Plate Ext/Inner Base Plate Yes 16.3 119 0 94143 94143 6918 9809 478 5

" Upper Upper Support Ring/Support/Seismic Block Support Ring/Support/Seismic Yes -6.9 -122.3 -9.5 113554 113554 6688 6688 1342 5

" Tie Bar Yes -49.3 -108.1 88 143795 6077 6077 877 5

" Hood Hood Support/Middle Support/Middle Base Plate/Inner Plate/Inner Yes 39.9 -59.5 0 85723 5495 5819 1815 -10

-10 Backing Backing Bar/Inner Bar/Inner Hood Pm+Pb Side Plate Ext/Inner Base Plate Yes 16.3 119 0 94143 94143 6918 9809 478 0

" Inner Inner Side Plate No 3.1 119 0.5 37229 7490 7490 9003 634 5

" Side Plate/Top Plate Yes 49.6 108.6 108.6 88 93256 93256 2526 2526 8571 1215 5

" Middle Middle Base Plate/Inner Plate/Inner Backing Backing Bar Yes -39.9 -108.6 0 84197 470 7712 1683 5 Out/Inner Backing Bar/Inner Hood Backing Bar/Inner Hood

" Side Plate/Top Plate Yes 17.6 17.6 119 88 91215 91215 920 7332 1585 5 Salt Salt Middle Middle hood No -68.6 69.6 43.7 31149 1717 2953 2914 2.5 2.5

" Outer hood No -97.3 -50.7 62 78572 969 2674 2622 5

" Closure plate No 46.2 -108.6 88 16192 3697 3697 5410 2561 10

" Hood Hood Support/Middle Support/Middle Base Plate/Inner Plate/Inner Backing Yes -39.9 0 0 85723 4695 4849 2378 -5 Hood( 6 )

Bar/Inner Hood(6)

Bar/Inner

"" Closure Closure plate No -70.8 85.2 71.9 17691 17691 271 2394 2355 -10

-10 Notes.

(a) Node numbers are retained for further reference.

reference.

(1-9)

(1-9) Appropriate stress reduction factor for the welds and modifications listed in Table 7 have been applied. The number refers to the Appropriate particular particular location and corresponding corresponding stress reduction factor in Table 7.

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Inc. Proprietary Proprietary Information Information

• Iz y X Pm [psi]

[psij 7500 6750 6750 6000 5250 4500 3750 3000 2250 1500 750 0o Figure 12a. Contour plot of maximum membrane stress intensity, intensity, Pm, for CLTP load. The maximum stress intensity is 7475 psi psi..

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• y411 z

X (psi]

Pm+Pb [psi]

9000 8000 7000 6000 6000 5000 4000 3000 3000 2000 1000 1000 o0 Figure 12b. Contour plot of maximum membrane+bending membrane+bending stress intensity, Pm+Pb, for CLTP load. The maximum stress stress intensity is 9809 psi. First view.

view .

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Continuum Dynamics, Inc. Proprietary Proprietary Information Information y

Y

~xX

/

Pm+Pb [psi]

9000 9000 8000 8000 7000 7000 6000 6000 5000 5000 4000 4000 3000 3000 2000 1000 1000 0o intensity, Pm+Pb, for CLTP membrane+bending stress intensity, Figure 12c. Contour plot of maximum membrane+bending load. This second view from below shows the high stress intensities intensities at the hood/stiffenerlbase plate junctions hood/stiffener/base welds..

channel/skirt welds junctions and drain channel/skirt

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• y41-z X

Salt [psi]

2750 25M0 2500 2250 2000 2000 1750 1500 1250 1000 750 500 250 alternating stress intensity, Figure 12d. Contour plot of alternating intensity, Salt' CL TP load. The maximum Salt, for CLTP maximum alternating stress intensity is 2728 psi. First view.

alternating view .

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Inc. Proprietary Proprietary Information Information Yy

~x Salt [psi]

2750 2500 2250 2000 1750 1750 1500 1500 1250 1250 1000 1000 750 500 250 12e. Contour plot of alternating Figure 12e. intensity, Salt, for CLTP load.

alternating stress intensity, Second view showing details of the outer hood and closure plate plate..

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• y4 z

,-, X Pm [psi]

7500 6750 6000 5250 4500 3750 3000 2250 2250 1500 1500 750 0o Figure 13a. Contour plot of maximum maximum membrane stress intensity, intensity, Pm, for CLTP CL TP operation with frequency shifts. The recorded recorded stress at a node is the maximum value taken over all frequency shifts. The maximum stress intensity is 7490 psi.

psi .

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• z Y X Pm+Pb [psi]

9000 9000 8000 8000 7000 7000 6000 6000 5000 5000 4000 4000 3000 3000 2000 2000 1000 1000 0o 13b. Contour plot of maximum membrane+bending Figure 13b. membrane+bending stress intensity, Pm+Pb, for CLTPCLTP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts.

shifts. The maximum stress stress intensity is 9809 psi.

view..

First view

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• z yY

~x Pm+Pb [psi]

[psi]

9000 8000 7000 6000 5000 4000 3000 2000 1000 1000 o

0 Figure 13c. membrane+bending stress intensity, Pm+Pb, for CLTP l3c. Contour plot of maximum membrane+bending operation with frequency shifts. This second view from beneath reveals stresses on support/base plate junctions, the hood support/base junctions, outer cover plate and drain channel/skirt channel/skirt welds..

welds

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• y z

X Salt [psi]

[psi]

3000 2750 2500 2250 2000 1750 1750 1500 1500 1250 1250 1000 1000 750 500 250 Figure 13d.

13d. Contour plot of alternating stress intensity, Salt, CLTP Salt, for CL TP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts. The maximum alternating shifts. alternating stress intensity is 2914 psi. First view.

view .

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• zz y

Ax X Salt [psi]

3000 2750 2500 2250 2000 1750 1500 1500 1250 1000 750 500 250 250 Figure 13e. Contour plot of alternating stress intensity, intensity, Salt, for CLTP operation operation with frequency frequency shifts. The recorded stress at a node is the maximum maximum value value taken over all frequency shifts. Second view from below.

below .

• 62