ML092440374

CDI Report No. 09-24NP, Rev. 0, Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer to 110% OLTP Power Level, Chapter 5 Through End (Non-proprietary Version)

ML092440374
Person / Time
Site:	Browns Ferry
Issue date:	08/31/2009
From:	Continuum Dynamics
To:	Office of Nuclear Reactor Regulation
References
CDI Report No. 09-24NP, Rev 0
Download: ML092440374 (56)

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

5. Results at 110% OLTP The stress intensities and associated stress ratios resulting from the Rev. 4 acoustic/hydrodynamic loads [2] with associated biases and uncertainties factored in, are presented below. The bias due to finite frequency discretization and uncertainty associated with the finite element model itself, are also factored in. In the following sections the highest maximum and alternating stress intensities are presented to indicate which points on the dryer experience significant stress concentration and/or modal response (Section 5.2). The lowest stress ratios obtained by comparing the stresses against allowable values, accounting for stress type (maximum and alternating) and location (on or away from a weld), are also reported (Section 5.3). Finally the frequency dependence of the stresses at nodes experiencing the lowest stress ratios is depicted in the form of accumulative PSDs (Section 5.4).

In each section results are presented both at nominal conditions (no frequency shift) and with frequency shift included. Unless specified otherwise, frequency shifts are generally performed at 2.5% increments. The tabulated stresses and stress ratios are obtained using a 'blanking' procedure that is designed to prevent reporting a large number of high stress nodes from essentially the same location on the structure. In the case of stress intensities this procedure is as follows. The relevant stress intensities are first computed at every node and then nodes sorted according to stress level. The highest stress node is noted and all neighboring nodes within 10 inches of the highest stress node and its symmetric images (i.e., reflections across the x=O and y=0 planes) are "blanked" (i.e., excluded from the search for subsequent high stress locations).

Of the remaining nodes, the next highest stress node is identified and its neighbors (closer than 10 inches) blanked. The third highest stress node is 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 is applied. Thus the lowest stress ratio of a particular type in a 10" neighborhood and its symmetric images is identified and all other nodes in these regions excluded from listing in the table. Of the remaining nodes, the one with the lowest stress ratio is reported and its neighboring points similarly excluded, and so on until all nodes are either blanked or have a stress ratio higher than 4.

The measured CLTP 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 can lead to sizeable, but fictitious acoustic loads and resulting stresses on the dryer. One way to filter these fictitious loads is to collect data with the system maintained at operating pressure (1000 psi) and temperature, but low (less than 20% of CLTP) flow. By operating the recirculation pumps at this condition, the 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 1000# data, originate entirely from non-acoustic sources such as sensor noise and mechanical vibrations. This information is valuable since it allows one to now distinguish between the acoustic and non-acoustic content in the CLTP signal and therefore modify the CLTP loads so that only the acoustic component is retained. In previous analyses of the BFN1 dryer, these low power signals were subtracted.

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information In the present implementation however, no filtering using low power data is performed. The reason for retaining noise in this particular case is to avoid protracted review of the low power subtraction process and to thus expedite qualification of the dryer. Thus, rather than attempting to justify the use of low power noise subtraction in this case, it was decided to use the CLTP signal (and by extension the 110% OLTP and EPU signals obtained by applying bump up factors) directly without noise filtering. Therefore for all results presented herein, no noise filtering using low power data has been performed.

The applied load includes all biases and uncertainties for both the ACM (summarized in.[2])

and the FEM. For the latter there are three main contributors to the bias and uncertainty. The first is an uncertainty (25.26%) that accounts for modeling idealizations (e.g., vane bank mass model), geometrical approximations and other discrepancies between the modeled and actual dryer such as neglecting of weld mass and stiffness in the FEA. The second contributor is a bias (9.53% - note that this has been increased from the 5.72% value previously used in [8])

accounting for discretization errors associated with using a finite size mesh, upon computed stresses. The third contributor is also a bias and compensates for the use of a finite discretization schedule in the construction of the unit solutions. The frequencies are spaced such that at 1%

damping the maximum (worst case) error in a resonance peak is 5%. The average error for this frequency schedule is 1.72%.

It is significant to note that the applied loads reflect revised bias and uncertainty values 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 the limiting stresses values, but are also overly conservative.

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

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information 5.1. Results at Predicted 110% OLTP Using Bump Up Factors (3)1))

The predictions below are obtained under this third option. The resulting alternating stress ratio at 110% OLTP is SR-a=2.01 when all frequency shifts are considered.

5.2 General Stress Distribution and High Stress Locations The maximum stress intensities obtained by post-processing the ANSYS stress histories for 110% OLTP at nominal frequency and with frequency shift operating conditions are listed in Table 8. Contour plots of the stress intensities over the steam dryer structure are shown on Figure 13 (nominal frequency) and Figure 14 (maximum stress over all nine frequency shifts including 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 and incorporate results from sub-modeling (see Section 4.5). 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, structural evaluation is more accurately made in terms of the stress ratios which compare the computed stresses to allowable levels with due account made for stress type and weld factors and also account for stress 44

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information corrections obtained using high-detail solid element sub-models. Comparisons on the basis of stress ratios are made in Section 5.2.

The maximum stress intensities in most areas are low (less than 400 psi, or 5% of the most conservative critical stress). For the membrane stresses (Pm) the high stress regions tend to occur at: (i) the restraint locations for the upper support ring and (ii) the upper edges of the closure plates, particularly where they connect to the inner hood. The first location is a very localized stress location and is believed to be significantly overestimated as a 'hot-spot' in the FEA. It experiences high stresses since the entire weight of the structure is transmitted through relatively small pads to the external structure. This. stress is dominated by the static component.

The closure plates experience high stresses since they restrain any motion of the adjacent vane banks. Note that the inner hood/closure plate weld also experiences high alternating stresses, but these occur several feet below the top of this weld. Other locations with relatively high Pm include the bottoms of the hood/hood support/base plate junctions and the connections between the bottom support beam spanning the dryer, and the vane banks (see Figure 13b). Frequency shifting does not significantly alter the high Pm stress locations and comparison of Table 8a and b shows that the leading Pm stress nodes are identical with and without frequency shifting.

Again, this is due to the dominance of the static (deadweight) load.

The membrane + bending stress (Pm+Pb) distributions evidence a stronger modal response.

Modal excitations are most pronounced on the skirt and the inner hood. Stress concentrations are observed at several locations coinciding with welds. The highest stress location is the same as for the highest membrane stress and lies near the dryer supports. Note that this stress occurs in a solid element where no distinction is made between the membrane and bending stresses (this distinction is only appropriate for thin members such as shell and beam elements). The next three entries for Pm+Pb are also the same as the leading locations for membrane stresses Pm and either involve the USR support or the closure plate connections to the hoods or vane bank end plates. These stresses also appear to be dominated by the static component since alternating stresses are comparatively low. The common junction between the middle hood, its top cover and the outer closure plate shows up as the 5 t entry in both Table 8a and b. Other locations where Pm+Pb stresses exceed the 2500 psi level include the bottom corners of the outer hood, the drain channel welds, the outer panels of the inner hoods, the top tie bars and the components used to support the steam dams.

The alternating stress distributions in Figure 13 and Figure 14 indicate that these stresses are below 500 psi over most of the dryer. The submerged skirt, though not exposed to direct acoustic forcing, evidences a pronounced modal response due to coupling with the upper steam dryer structure subjected to acoustic loads. The highest alternating stress intensities at any frequency shift occur on the large middle plate spanning the dryer at its center section.

Inspection of Figure 14e and f also reveals high alternating stresses on the outer panels of the inner hood, the end plate of the outer hood, approximately mid-way on the inner hood/closure plate weld, and the top of the outer hood reinforcement channels. Also, the portion of the old bar' left in place to help support the steam dam experiences high stresses. It is planned to eventually remove these bars in preparation for EPU operation and replace them with the more effective gussets used between the old bar locations. For the middle plate when considering all frequency shifts the stress intensity increases by 38% compared to the zero shift value. Also, 45

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information when all shifts are considered two of the five leading alternating stress locations now appear on the outer panels of the inner hood. This component has a strong response at 59.5 Hz and is driven by a 61 Hz signal at the -2.5% shift (see below).

Finally, for reference the highest stress intensities at any frequency shift for the locations in Table 8b are recomputed using the CLTP loads (again, without noise removal) and reported in Table 8c. The alternating stresses are generally approximately lower at CLTP by 10% thus reflecting the velocity square scaling. The lock gusset shows a 30% alternating stress reduction at CLTP which is due to the strong steam dam response in the 100-120 Hz range where the higher bump-up factors are applied.

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 8a. Locations with highest predicted stress intensities at 110% OLTP conditions at zero frequency shift.

Stress Location Weld Location (in)(a) node(b) Stress Intensities (psi)

Category x y z Pm Pm+Pb Salt Pm Upper Support Ring (USR)/Seismic Block/Support Part No 122.1 -10 -9.5 122062 8580 8580 2649 USR part/Support/Support Part No 7 122.3 -9.5 122280 7280 7280 1983 Top Cover Inner Hood/Middle Closure Plate/Inner Hood Yes -31.5 -108.4 88.9 91141 6468 7423 1890

" Middle Closure Plate No -33.9 -108.4 88.9 7274 5885 6164 1627 Middle Base Plate/Hood Support/Inner Hood(d) Yes 39.8 -59.8 0 104843 4940 4962 2976 Pm+Pb USR/Seismic Block/Support Part No 122.1 -10 -9.5 122062 8580 8580 2649 Top Cover Inner Hood/Middle Closure Plate/Inner Hood Yes -31.5 -108.4 88.9 91141 6468 7423 1890 USR part/Support/Support Part No 7 122.3 -9.5 122280 7280 7280 1983 Middle Closure Plate No -33.9 -108.4 88.9 7274 5885 6164 1627 Top Cover Middle Hood/Outer Closure Plate/Middle Hood Yes -62.5 85 88.9 90897 4803 5365 2655 Salt Lock Gusset No 78.9 31.4 93.2 82835 3914 4190 4184 Old Bar Yes 81.5 31.4 88.9 132385 3463 3463 3411 Mid Plate No 0 -3.9 88.2 23883 203 3514 3289 Dam Plate/New Gusset Yes 77 58.2 104.4 98791 275 3380 3234

" Top Cover Middle Hood/Thin Tie Bar Base No -55.5 31.4 88.9 89960 510 3277 3183 Notes for Table 8 and Table 9.

(a) Spatial coordinates are in a reference frame with origin at the intersection of the steam dryer centerline and the plane containing the base plates (this plane also contains the top of the USR and the bottom edges of the hoods). The y-axis is parallel to the hoods, the x-axis is normal to the hoods pointing from MSL C/D to MSL A/B, and the z-axis is vertical, positive up.

(b) Node numbers are retained for further reference.

(c) Per [20], the nominal stress intensities at the drain channel/skirt junction are multiplied by 0.58.

(d) Per [20], the nominal stress intensities at the inner hood/hood support/middle base plate junction are multiplied by 0.79.

(e) For the stitch weld connecting the T-bar to the base plates an undersize weld factor of 2.0 has been applied. Also parts retention analysis has been carried out separately [25] to verify that the T-bar, which is a secondary structural member, remains attached.

(f) Other stress reduction factors apply as described in Section 4.5.

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 8b. Locations with highest predicted stress intensities taken over all frequency shifts at 110% OLTP conditions.

Stress Location Weld Location (in)(a) node(b) Stress Intensities (psi) % Freq.

Category x y z Pm Pm+Pb Salt Shift Pm USR/Seismic Block/Support Part No 122.1 -10 -9.5 122062 8797 8797 2796 7.5

" USRpart/Support/Support Part No 7 122.3 -9.5 122280 7393 7393 2414 2.5 Top Cover Inner Hood/Middle Closure Yes -31.5 -108.4 88.9 91141 6679 7633 2075 5 Plate/Inner Hood

" Middle Closure Plate No -33.9 -108.4 88.9 7274 6094 6399 1831 5 Middle Base Plate/Hood Support/Inner Hoodtd) Yes 39.8 -59.8 0 104843 5437 5460 3240 5 Pm+Pb USR/Seismic Block/Support Part No 122.1 -10 -9.5 122062 8797 8797 2796 7.5 Top Cover Inner Hood/Middle Closure Yes -31.5 -108.4 88.9 91141 6679 7633 2075 5 Plate/Inner Hood USR part/Support/Support Part No 7 122.3 -9.5 122280 7393 7393 2414 2.5 Middle Closure Plate No -33.9 -108.4 88.9 7274 6094 6399 1831 5 Top Cover Middle Hood/Outer Closure Yes -62.5 85 88.9 90897 5235 5832 3230 5 Plate/Middle Hood Salt Mid Plate No 0 -3.9 88.2 23883 214 5234 4880 -5 Lock Gusset No 78.9 31.4 93.2 82835 3914 4190 4184 0 Vane Bank Thin/Vane Bank Thick/Outer End Yes -86 85 12.1 100239 491 4316 3962 10 Wall/Outer Side Panel

" Inner Hood No 35.8 80.8 38 46479 413 4139 3925 -2.5 Middle Closure Plate/Inner Hood Yes 35.8 108.4 38 94004 898 4016 3835 -2.5 See Table 8a for notes (a)-(f).

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 8c. Highest stress intensities at any frequency shift for the nodes listed in Table 8b at CLTP conditions.

Stress Location Weld Location (in)(a) node(b) Stress Intensities (psi) % Freq.

Category x y z Pm Pm+Pb Salt Shift Pm USR/Seismic Block/Support Part No 122.1 -10 -9.5 122062 8472 8472 2522 7.5 USR part/Support/Support Part No 7 122.3 -9.5 122280 7223 7223 2205 2.5 Top Cover Inner Hood/Middle Closure Yes -31.5 -108.4 88.9 91141 6552 7496 1839 5 Plate/Inner Hood Middle Closure Plate No -33.9 -108.4 88.9 7274 5976 6272 1633 5 Middle Base Plate/Hood Support/Inner Hood(d) Yes 39.8 -59.8 0 104843 6312 6345 3630 5 Pm+Pb USR/Seismic Block/Support Part No 122.1 -10 -9.5 122062 8472 8472 2522 7.5 Top Cover Inner Hood/Middle Closure Yes -31.5 -108.4 88.9 91141 6552 7496 1839 5 Plate/Inner Hood USR part/Support/Support Part No 7 122.3 -9.5 122280 7223 7223 2205 2.5 Middle Closure Plate No -33.9 -108.4 88.9 7274 5976 6272 1633 5 Top Cover Middle Hood/Outer Closure Yes -62.5 85 88.9 90897 4994 5588 2943 10 Plate/Middle Hood Salt Mid Plate No 0 -3.9 88.2 23883 209 4752 4430 -5 Lock Gusset No 78.9 31.4 93.2 82835 2851 3008 2919 0 Vane Bank Thin/Vane Bank Thick/Outer End Yes -86 85 12.1 100239 473 3977 3563 10 Wall/Outer Side Panel Inner Hood No 35.8 80.8 38 46479 373 3654 3491 -2.5 Middle Closure Plate/Inner Hood Yes 35.8 108.4 38 94004 867 3566 3418 -2.5 See Table 8a for notes (a)-(f).

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

Pm [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 13a. Contour plot of maximum membrane stress intensity, Pm, for 110% OLTP load.

The maximum stress intensity is 8,580 psi. First view.

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

Pm [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 13b. Contour plot of maximum membrane stress intensity, Pm, for 110% OLTP load.

Second view from below.

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

Pm+Pb [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 13c. Contour plot of maximum membrane+bending stress intensity, Pm+Pb, for 110%

OLTP load. The maximum stress intensity is 8580 psi. First view.

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

Pm+Pb [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 13d. Contour plot of maximum membrane+bending stress intensity, Pm+Pb, for 110%

OLTP load. Second view from below.

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

x) y salt [psi]

4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 Figure 13e. Contour plot of alternating stress intensity, Salt, for 110% OLTP load. The maximum alternating stress intensity is 4184 psi.

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

salt [psi]

4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800 600 400 200 Figure 13f Contour plot of alternating stress intensity, Salt, for 110% OLTP load. Second view from below.

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

Pm [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 14a. Contour plot of maximum membrane stress intensity, Pm, for 110% OLTP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts. The maximum stress intensity is 8797 psi.

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

PM [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 14b. Contour plot of maximum membrane stress intensity, Pm, for 110% OLTP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts. Second view from below.

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

Pm+Pb [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 14c. Contour plot of maximum membrane+bending stress intensity, Pm+Pb, for 110%

OLTP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts. The maximum stress intensity is 8797 psi. First view.

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

Pm+Pb [psi]

8500 8000 7500 7000 6500 6000 5500 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Figure 14d. Contour plot of maximum membrane+bending stress intensity, Pm+Pb, for 110%

OLTP operation with frequency shifts. This second view from beneath reveals high stress and modal response of interior hood supports.

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

Salt [psi]

5000 4750 4500 4250 4000 3750 3500 3250 3000 2750 2500 2250 2000 1750 1500 1250 1000 750 500 250 Figure 14e. Contour plot of alternating stress intensity, Salt, for 110% OLTP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts. The maximum alternating stress intensity is 4880 psi.

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

Salt [psi]

5000 4750 4500 4250 4000 3750 3500 3250 3000 2750 2500 2250 2000 1750 1250 1000 750 500 250 Figure 14f Contour plot of alternating stress intensity, Salt, for 110% OLTP operation with frequency shifts. The recorded stress at a node is the maximum value taken over all frequency shifts. Second view from below.

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information 5.3 Load Combinations and Allowable Stress Intensities The stress ratios computed for CLTP at nominal frequency and with frequency shifting are listed in Table 9. The stress ratios are grouped according to type (SR-P for maximum membrane and membrane+bending stress, SR-a for alternating stress) and location (away from welds or on a weld). The tabulated nodes are also depicted in Figure 15 (no frequency shift) and Figure 16 (all frequency shifts included). The plots corresponding to maximum stress intensities depict all nodes with stress ratios SR-P_<4, whereas the plots of alternating stress ratios display all nodes with SR-a_<4 or SR-a_<5 as indicated.

The limiting alternating stress location on the steam dryer occurs at the inmost end of the stitch weld connecting the inner base plate to the T-bar (alternatively referred to as the middle support beam or rib). This weld is undersized and thus is subject to an undersize weld factor of 2.0 in addition to the 1.8 weld factor. However, the T-bar is a secondary structural member in that it is not required to maintain structural integrity (it is believed that the T-bar component was required for transportation and assembly of the two steam dryer halves). While secondary structural members are not required to meet stress fatigue endurance levels it must nevertheless be shown that these members do not produce or become loose parts. This analysis is conducted separately [25]. Briefly, it is shown that a failure in the stitch weld is ultimately self-arresting and that the stresses in the remaining weld fall below allowable levels and the T-bar remains connected to the steam dryer. In the present analysis, the two limiting points (one for the innermost end of each of the two T-bars) are excluded from the list of high stress locations.

If one excludes the T-bar ends from the list of high stress locations on account of its classification as a secondary member, then the limiting alternating stress ratio is SR-a=2.01 and occurs on the base of the old tie bar left in place to help support the steam dam. This limiting stress ratio occurs at the zero frequency shift so that the value with and without frequency shifting are the same. The stress is driven by a significant steam dam response at 109 Hz and reflects the additional bump-up factor in the 100-120 Hz range as well as the increased bias and uncertainty in the 109-113 Hz range added to conservatively account for possible standpipe excitation in this frequency range. At CLTP, the alternating stress ratio is SR-a=2.86 (Note that when low power noise was removed this CLTP value increased SR-a=3.80 suggesting that non-acoustic signal is a significant contributor to the local stress). Note that prior to operation at EPU it is planned to replace this remaining bar with a larger steam dam gusset and also add a half-pipe reinforcement on the steam dam to simultaneously reduce stresses induced by the steam dam vibrations and reduce the amplitude of these vibrations.

The leading alternating stress locations in Table 9b generally occur on: (i) components involving the old bar; (ii) closure plates where they connect to a hood; (iii) the bottom of the weld joining the drain channel to the skirt; (iv) the intersection between the hood, hood support and base plate; (v) the inner hood/hood support welds; (vi) front ends of the steam dam gusset pads and (vii) the ends of the vane bank end walls. In addition, the undersized stitch weld joining the T-bar to the base plates appears multiple times. All of these, locations lie on welds.

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information The minimum stress ratio due to maximum stress intensity at no frequency shift is SR-P=1.44 and occurs at the top of the middle closure plate connecting to the inner hood; it reduces to 1.39 when all frequency shifts are included.

Finally, the highest stress intensities (and lowest stress ratios) at any frequency shift for the locations in Table 9b are recomputed using the CLTP loads without noise removal and reported in Table 9c. The limiting alternating stress ratio at any frequency shift in this table is SR-a=2.33 and occurs on the bottom of the drain channel/skirt weld. To confirm that this is the limiting node on the dryer, a real time calculation is carried out where the CLTP stresses are computed at all nodes having an alternating stress ratio, SR-a<4 at 110% OLTP. There are 723 such nodes and the limiting alternating stress ratio for these nodes is indeed at node 98802 with the stresses and stress ratios listed in Table 9c. Hence the limiting alternating stress ratio at any frequency shift on the dryer at CLTP with noise retained is SR-a=2.33. This is value used to generating the limit curves. Since acoustic loads scale roughly with the square of the steam flow, another estimate of the 110% OLTP limiting stress can be obtained from SR-a=l.33/1.10=2.12. This is higher than the estimate obtained using the bump-up factors. Therefore the conservative estimate of the 110% OLTP alternating stress ratio remains SR-a=2.01 as already established above.

In summary, when excluding the T-bar ends as discussed above, the lowest alternating stress ratio at 110% OLTP occurs on the old bar left in place to support the steam dam at the 0%

frequency shift. The lowest value at any frequency shift is SR-a=2.01 indicating that stresses are below target levels. The lowest stress ratio associated with a maximum stress is SR-P=1.39.

This value is dominated by the static component and is only weakly altered by acoustic loads.

Since all the applied loads already account for all end-to-end biases and uncertainties, these values imply that the target stress levels for 110% OLTP operation are met.

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 9a. Locations with minimum stress ratios for 110% OLTP conditions with no frequency shift. Stress ratios are grouped according to stress type (maximum - SR-P; or alternating - SR-a) and location (away from a weld or at a weld). Bold text indicates minimum stress ratio of any type on the structure. Locations are depicted in Figure 15.

Stress Weld Location Location (in.) (a) node(b) Stress Intensity (psi) Stress Ratio Ratio x y z Pm Pm+Pb Salt SR-P SR-a SR-P No 1. USR/Seismic Block/Support Part 122.1 -10 -9.5 122062 8580 8580 2649 1.97 4.67

2. USR part/Support/Support Part 7 122.3 -9.5 122280 7280 7280 1983 2.32 6.24

.. .. 3. Middle Closure Plate -33.9 -108.4 88.9 7274 5885 6164 1627 2.87 7.6 SR-a No Lock Gusset 78.9 31.4 93.2 82835 3914 4190 4184 4.32 2.96 Middle Plate 0 -3.9 88.2 23883 203 3514 3289 7.21 3.76 SR-P Yes 1. Top Cover Inner Hood/Middle.Closure -31.5 -108.4 88.9 91141 6468 7423- 1890 1.44 ,4.67.

Plate/Inner Hood

2. Middle Base Plate/Tbar(e) 41.8 0 0 107661 2521 2600 1048 1.84 3.28

3. Middle Base Plate/Hood Support/Inner Hood(d) 39.8 -59.8 0 104843 4940 4962 2976 1.88 2.31

4. Top Cover Middle Hood/Outer Closure 62.5 -85 88.9 90137 4851 5111 2618 1.92 3.37 Plate/Middle Hood

5. Splice Bar/USR Part -2.2 -119 0 122330 3970 3970 541 2.34 12.69

6. Splice Bar/Straddle 6 117.8 -9.5 121881 3897 3897 723 2.39 9.49

7. Outer Base Plate/Hood Support/Middle Hood(d) 70.8 -54.6 0 101377 3760 4045 2718 2.47 2.53

. .8. Top Cover Inner Hood/Inner Hood -31.5 -110.1 88.9 91169 3578 3842 945 2.6 7.27

9. Old Bar 81.5 31.4 88.9 132385 3463 3463 3411 2.68 2.01

10. Submerged Drain Channel/Skirt(c) -91 76.7 -100.5 98024 1406 5137 2509 2.71 2.74

11. Submerged Drain Channel/Skirt -91 76.7 -98.5 98049 460 4937 1635 2.82 4.2

.. .. 12. Submerged Drain Channel/Skirt(c) -11.5 118.4 -100.5 98156 1278 4598 3126 3.03 2.2 See Table 8a for notes (a)-(f).

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This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 9a (cont.). Locations with minimum stress ratios for 110% OLTP conditions with no frequency shift. Stress ratios are grouped according to stress type (maximum - SR-P; or alternating - SR-a) and location (away from a weld or at a weld). Bold text indicates minimum stress ratio of any type on the structure. Locations are depicted in Figure 15.

Stress Weld Location Location (in.) (a) node(b) Stress Intensity (psi) Stress Ratio Ratio x y z Prn Pm+Pb Salt SR-P SR-a SR-a Yes 1. Old Bar 81.5 31.4 88.9 132385 3463 3463 3411 2.68 2.01

.. .. 2. Dam Plate/New Gusset 77 58.2 104.4 98791 275 3380 3234 4.12 2.12

3. Thick Tie Bar Base/Top Cover 80.2 30.2 88.9 97091 508 3279 3212 4.25 2.14

4. Submerged Drain Channel/Skirt(c) -11.5 118.4 -100.5 98156 1278 4598 3126 3.03 2.20

5. Hood Mod/Top Cover Outer Hood/ Thin Gusset Pad 93.5 -57.5 88.9 110494 421 4014 3085 3.47 2.23

6. Middle Base Plate/Hood Support/Inner Hood/Tbar(e) 39.8 0 0 107662 2807 3176 2102 2.72 2.29

7. Middle Base Plate/Hood Support/Inner Hood(d) 39.8 -59.8 0 104843 4940 4962 2976 1.88 2.31

8. Submerged Drain Channel/Skirt(c) 91 76.7 -100.5 98226 1183 4992 2841 2.79 2.42

9. Outer Base Plate/Hood Support/Middle Hood(d) 70.8 -54.6 0 101377 3760 4045 2718 2.47 2.53

10. Top Cover Middle Hood/Middle Hood/Shell Tie Bar -62.5 -25.2 88.9 103227 1538 2592 2505 5.38 2.74

.. .. 11. Outer Base Plate/Vane Bank Thin/Tbar(e) -77 0 0 109369 1359 3033 2417 4.6 2.84

12. Dam Plate/Lock 77 32.5 104.4 90937 353 2600 2416 5.36 2.84

.. .. 13. Top Cover Middle Hood/Outer Closure Plate/Middle Hood 62.5 85 88.9 111150 3259 3640 2831 2.85 3.12 See Table 8a for notes (a)-(f).

65

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 9b. Locations with minimum stress ratios at 110% OLTP conditions with frequency shifts. Stress ratios at every node are recorded as the lowest stress ratio identified during the frequency shifts. Stress ratios are grouped according to stress type (maximum

- SR-P; or alternating - SR-a) and location (away from a weld or at a weld). Bold text indicates minimum stress ratio of any type on the structure. Locations are depicted in Figure 16.

Stress Weld Location Location (in.) (a) node(b) Stress Intensity (psi) Stress Ratio % Freq.

Ratio x y z Pm Pm+Pb Salt SR-P SR-a Shift SR-P No 1. USR/Seismic Block/Support Part 122.1 -10 -9.5 122062 8797 8797 2796 1.92 4.42 7.5

2. USR part/Support/Support Part -6.8 -122.3 -8 121828 7393 7393 2414 2.29 5.12 2.5

3. Middle Closure Plate -33.9 -108.4 88.9 7274 6094 6399 1831 2.77 6.75 5

.. .. 4. Hood Support -37.5 59.8 0 9628 4929 4956 2928 3.43 4.22 2.5 SR-a No 1. Mid Plate 0 -3.9 88.2 23883 214 5234 4880 4.84 2.53 -5

2. Lock Gusset 78.9 31.4 93.2 82835 3914 4190 4184 4.32 2.96 0

3. Inner hood 35.8 80.8 38 46479 413 4139 3925 6.12 3.15 -2.5 SR-Pf Yesý -iiTop:Cover-Inn~erHood/Mid-dle 315-0:~8.9, !91ii'1N 0679 , 7633 17, '-

Clos re Plate/Innher'Hood .

2. Middle Base Plate/Hood Support/Inner Hood(d) 39.8 -59.8 0 104843 5437 5460 3240 1.71 2.12 5

3. Top Cover Middle Hood/Outer -62.5 85 88.9 90897 5235 5832 3230 1.78 2.73 7.5 Closure Plate/Middle Hood I I

.. .. 4. Middle Base Plate/Tbar(e) 41.8 0 0 107661 2521 2600 1048 1.84 3.28 0

5. Splice Bar/USR Part -2.2 -119 0 122330 4163 4163 688 2.23 9.98 -5

6. Splice Bar/Straddle -6 -117.8 -9.5 122087 4010 4010 862 2.32 7.96 2.5

.. .. 7. Top Cover Inner Hood/Inner Hood -31.5 -110.1 88.9 91169 3802 4080 1141 2.44 6.02 5

8. Submerged Drain Channel/Skirt(c) 91 76.7 -100.5 98226 1341 5679 2841 2.46 2.42 -2.5

.. .. 9. Outer Base Plate/Hood Support/Middle Hood(d) 70.8 -54.6 0 101377 3760 4045 2766 2.47 2.48 0

.. .. 10. Submerged Drain Channel/Skirt 91 -76.7 -98.5 98688 450 5408 2087 2.58 3.29 7.5

.. .. 11. Old Bar 81.5 31.4 88.9 132385 3463 3463 3411 2.68 2.01 0

12. Submerged Drain Channel/Skirt(c) 11.5 -118.4 -100.5 98802 1435 4909 3294 2.84 2.09 5

" 13. Submerged Drain Channel/Skirt 11.5 -118.4 -98.5 98859 387 4665 2698 2.99 2.55 5

.. .. 14. Hood Support/Inner Hood -39.8 59.8 2.5 97897 3011 3144 1910 3.09 3.6 2.5 See Table 8a for notes (a)-(f).

66

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 9b (cont.). Locations with minimum stress ratios at 110% OLTP conditions with frequency shifts. Stress ratios at every node are recorded as the lowest stress ratio identified during the frequency shifts. Stress ratios are grouped according to stress type (maximum - SR-P; or alternating - SR-a) and location (away from a weld or at a weld). Bold text indicates minimum stress ratio of any type on the structure. Locations are depicted in Figure 16.

Stress Weld Location Location (in.) (a) node(b) Stress Intensity (psi) Stress Ratio % Freq.

Ratio x y z Pm Pm+Pb Salt SR-P SR-a Shift SR-a Yes 1. Old Bar 81.5 31.4 88.9 132385 3463 3463 3411 2.68 2.01 0

.. .. 2. Submerged Drain Channel/Skirt(c) 11.5 -118.4 -100.5 98802 1435 4909 3294 2.84 2.09 5

.. .. 3. Middle Base Plate/Hood Support/Inner Hood(d) 39.8 -59.8 0 104843 5437 5460 3240 1.71 2.12 5

.. .. 4. Dam Plate/New Gusset 77 58.2 104.4 98791 275 3380 3234 4.12 2.12 0

.. .. 5. Thick Tie Bar Base/Top Cover 80.2 30.2 88.9 97091 580 3279 3212 4.25 2.14 0

.. .. 6. Submerged Drain Channel/Skirt(c) -91 76.7 -100.5 98024 1406 5425 3187 2.57 2.16 -2.5

7. Middle Cover Plate/Hood Support/Inner 39.8 0 0 107662 2936 3380 2445 2.6 2.16 5 Hood/Tbar(e) I_ I

.. .. 8. Top Cover Middle Hood/Middle Hood/Shell Tie Bar 62.5 25.2 88.9 99661 1814 3481 3138 4.01 2.19 7.5

.. .. 9. Hood Support/Inner Hood 36.6 59.8 34.3 93462 505 3198 3100 4.36 2.22 -2.5

.. .. 10. Hood Mod/Top Cover Outer Hood/Gusset Pad Thin 93.5 -57.5 88.9 110494 441 4254 3085 3.28 2.23 2.5

.. .. 11. Hood Support/Inner Hood 31.6 59.8 59.2 93481 1102 3160 3083 4.41 2.23 -2.5

12. Vane Bank Thin/Vane Bank Thick/Outer End -86 85 12.1 100239 491 4316 3962 3.23 2.23 10 Wall/Outer Side Panel

13. Mid Plate Support/Mid Plate 0 17 2 103220 420 3100 3068 4.5 2.24 -5

.. .. 14. Middle Closure Plate/Inner Hood 35.8 108.4 38 94004 898 4016 3835 3.47 2.3 -2.5

15. Hood Support/Inner Hood 33.7 59.8 48.2 95680 643 2981 2829 4.68 2.43 -2.5

16. Outer Side Panel/Vane Bank Thick/Outer End Wall 86 -85 10 100798 534 3077 2815 4.53 2.44 10

17. Outer Base Plate/Hood Support/Middle Hood(d) 70.8 -54.6 0 101377 3760 4045 2766 2.47 2.48 5

18. Submerged Drain Channel/Skirt 11.5 -118.4 -98.5 98859 387 4665 2698 2.99 2.55 7.5 See Table 8a for notes (a)-(f).

67

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 9c. Minimum stress ratios at any frequency shift for the nodes listed in Table 9b computed at CLTP conditions. Locations are depicted in Figure 16.

Stress Weld Location Location (in.) (a) node(b) Stress Intensity (psi) Stress Ratio  % Freq.

Ratio x y z Pm Pm+Pb Salt SR-P SR-a Shift SR-P No 1. USR/Seismic Block/Support Part 122.1 -10 -9.5 122062 8472 8472 2522 1.99 4.90 7.5

2. USR part/Support/Support Part -6.8 -122.3 -8 121828 7193 7193 1772 2.35 6.98 2.5

3. Middle Closure Plate -33.9 -108.4 88.9 7274 5976 6272 1633 2.83 7.57 5

4. Hood Support -37.5 59.8 0 9628 4491 4515 2612 3.76 4.73 2.5 SR-a No 1. Mid Plate 0 -3.9 88.2 23883 209 4752 4430 5.33 2.79 -5

2. Lock Gusset 78.9 31.4 93.2 82835 2851 3008 2919 5.93 4.24 0

3. Inner hood 35.8 80.8 38 46479 373 3654 3491 6.94 3.54 -2.5 SR-P'* Yes 1. Top Cover Inner Hood/Middle - , -31.5 -108.4 88:9 91141 5111, 5847, 1435 1.82 4579' ClosurePlate/Inner Hood , " .

2. Middle Base Plate/Hood Support/Inner Hood(d) 39.8 -59.8 0 104843 4986 5012 2868 1.86 2.39 5

3. Top Cover Middle Hood/Outer -62.5 85 88.9 90897 3895 4359 2296 2.39 2.99 7.5 Closure Plate/Middle Hood

4. Middle Base Plate/Tbar(e) 41.8 0 0 107661 2804' 2859 1304 1.66 2.63 -5

5. Splice Bar/USR Part -2.2 -119 0 122330 4086 4086 620 2.27 11.08 2.5

6. Splice Bar/Straddle -6 -117.8 -9.5 122087 3931 3931 783 2.36 8.78 2.5

7. Top Cover Inner Hood/Inner Hood -31.5 -110.1 88.9 91169 3717 3988 1030 2.50 6.67 5

8. Submerged Drain Channel/Skirt(c) 91 76.7 -100.5 98226 1230 5329 2523 2.62 2.72 -2.5

... .. 9. Outer Base Plate/Hood Support/Middle Hood(d) 70.8 -54.6 0 101377 3154 3565 2356 2.95 2.92 0

10. Submerged Drain Channel/Skirt 91 -76.7 -98.5 98688 429 5174 1818 2.69 3.78 7.5

.. .. 11. Old Bar 81.5 31.4 88.9 132385 2511 2511 2406 3.70 2.86 0

.. .. 12. Submerged Drain Channel/Skirt(c) 11.5 -118.4 -100.5 98802 1287 4525 2949 3.08 2.33 5

.. .. 13. Submerged Drain Channel/Skirt 11.5 -118.4 -98.5 98859 342 4467 2425 3.12 2.83 5

.. .. 14. Hood Support/Inner Hood -39.8 59.8 2.5 97897 2738 2866 1668 3.40 4.12 2.5 See Table 8a for notes (a)-(f) 68

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Table 9c (cont.). Minimum stress ratios at any frequency shift for the nodes listed in Table 9b computed at CLTP conditions.

Locations are depicted in Figure 16.

Stress Weld Location Location (in.) (a) node(b) Stress Intensity (psi) Stress Ratio % Freq.

Ratio x y z Pm Pm+Pb Salt SR-P SR-a Shift SR-a Yes 1. Old Bar 81.5 31.4 88.9 132385 2511 2511 2406 3.70 2.86 0

2. Submerged Drain Channel/Skirt(c) 11.5 -118.4 -100.5 98802 1287 4525 2949 3.08 2.33 5

3. Middle Base Plate/Hood Support/Inner Hood(d) 39.8 -59.8 0 104843 4986 5012 2868 1.86 2.39 7.5

4. Dam Plate/New Gusset 77 58.2 104.4 98791 236 2112 1989 6.60 3.45 -2.5

5. Thick Tie Bar Base/Top Cover 80.2 30.2 88.9 97091 505 2461 2330 5.66 2.95 0

6. Submerged Drain Channel/Skirt(c) -91 76.7 -100.5 98024 1289 5081 2787 2.74 2.46 -2.5 to 7. Middle Cover Plate/Hood Support/Inner 39.8 0 0 107662 2298 3060 1653 2.68 2.67 5 Hood/Tbar(e)

8. Top Cover Middle Hood/Middle Hood/Shell Tie Bar 62.5 25.2 88.9 99661 1597 3242 2881 4.30 2.38 7.5 to 9. Hood Support/Inner Hood 36.6 59.8 34.3 93462 459 2843 2744 4.90 2.50 -2.5

.. .. 10. Hood Mod/Top Cover Outer Hood/Gusset Pad Thin 93.5 -57.5 88.9 110494 370 3411 2340 4.09 2.94 0 to 11. Hood Support/Inner Hood 31.6 59.8 59.2 93481 959 2757 2652 5.06 2.59 -2.5

12. Vane Bank Thin/Vane Bank Thick/Outer End -86 85 12.1 100239 369 3102 2779 4.49 2.47 10 Wall/Outer Side Panel to 13. Mid Plate Support/Mid Plate 0 17 2 103220 387 2832 2775 4.92 2.48 -5 to 14. Middle Closure Plate/Inner Hood 35.8 108.4 38 94004 677 2781 2666 5.01 2.58 -2.5 to 15. Hood Support/Inner Hood 33.7 59.8 48.2 95680 550 2620 2476 5.32 2.77 -2.5 to 16. Outer Side Panel/Vane Bank Thick/Outer End Wall 86 -85 10 100798 469 2736 2524 5.10 2.72 10

. 17. Outer Base Plate/Hood Support/Middle Hood(d) 70.8 -54.6 0 101377 3154 3565 2356 2.95 2.92 5

.. .. 18. Submerged Drain Channel/Skirt 11.5 -118.4 -98.5 98859 342 4467 2425 3.12 2.83 7.5 See Table 8a for notes (a)-(f).

69

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

X Y SR-P 4

3.9 3.8 3.7 3.6

- 3.5 3.3 3.2 3.1 3

2.9 2.8 2.7 2.6 2.5 2.4 Figure 15a. Locations of smallest maximum stress ratios, SR-P<4A at non-welds for nominal 1 10% OLTP operation. Numbers refers to the enumerated locations for SR-P values at non-welds in Table 9a.

70

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 15b. Locations of smallest alternating stress ratios, SR-a<5, at non-welds for nominal 110% OLTP operation. Numbers refers to the enumerated locations for SR-a values at non-welds in Table 9a.

71

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 15c. Locations of smallest maximum stress ratios, SR-P<4, at welds for nominal 110%

OLTP operation. Numbers refer to the enumerated locations for SR-P values at welds in Table 9a. First view showing locations 1, 4, 5, 8 and 9.

72

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 15d. Locations of smallest maximum stress ratios, SR-P<4, at welds for nominal CLTP operation. Numbers refer to the enumerated locations for SR-P values at welds in Table 9a.

Second view showing locations 2, 3, 7 and 10-12.

73

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

Figure 15e. Locations of smallest maximum stress ratios, SR-P<4, at welds for nominal 110%

OLTP operation. Numbers refer to the enumerated locations for SR-P values at welds in Table 9a. Third view showing locations 2, 6, 10 and 11.

74

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

Y SR-a 4

3.8 3.6 3.4 3.2 3

2.8 2.6 2.4 2.2 2

2*

Figure 15f. Locations of minimum alternating stress ratios, SR-a<4, at welds for nominal 110%

OLTP operation. Numbers refer to the enumerated locations for SR-a values at welds in Table 9a. First view showing locations 1-5, 8, 10, 12 and 13.

75

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 15g. Locations of minimum alternating stress ratios, SR-a<4, at welds for nominal 110%

OLTP operation. Numbers refer to the enumerated locations for SR-a values at welds in Table 9a. Second view showing locations 4, 6-9 and 11.

76

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

Y SR-P 3.9 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.3 2.1 1.9 Figure 16a. Locations of minimum stress ratios, SR-P<4, associated with maximum stress intensities at non-welds for 110% OLTP operation with frequency shifts. The recorded stress ratio is the minimum value taken over all frequency shifts. The numbers refers to the enumerated location for SR-P values at non-welds in Table 9b. This view shows locations 1 and 4.

77

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

SR-P 3.9 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.3 2.1 1.9 Figure 16b. Locations of minimum stress ratios, SR-P<4, associated with maximum stress intensities at non-welds for 110% OLTP operation with frequency shifts. The recorded stress ratio is the minimum value taken over all frequency shifts. The numbers refers to the enumerated location for SR-P values at non-welds in Table 9b. This view shows locations 2 and 3.

78

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 16c. Locations of minimum alternating stress ratios, SR-a_<5, associated with alternating stress intensities at non-welds for 110% OLTP operation with frequency shifts. The recorded stress ratio is the minimum value taken over all frequency shifts. The numbers refers to the enumerated location for SR-a values at non-welds in Table 9b.

79

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

Figure 16d. Locations of minimum stress ratios, SR-P<4, associated with maximum stress intensities at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-P values at welds in Table 9b. This view shows locations 1, 3, 5, 7, 12 and 13.

80

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

SR-P 4

3.8 3.6 3.4 3.2 3

2.8 2.6 Y4 22 X

Figure 16e. Locations of minimum stress ratios, SR-P<4, associated with maximum stress intensities at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-P values at welds in Table 9b. This view shows locations 2, 4, 6, 8-10, 12 and 13.

81

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information AS Figure 16f. Locations of minimum stress ratios, SR-P<4, associated with maximum stress intensities at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-P values at welds in Table 9b. This view shows location 11.

82

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 16g. Locations of minimum stress ratios, SR-P<_4, associated with maximum stress intensities at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-P values at welds in Table 9b. This view shows locations 10 and 14.

83

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 16h. Locations of minimum alternating stress ratios, SR-a<4, at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-a values at welds in Table 9b. This view shows locations 1, 4, 5, 8, 10 and 16.

84

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 16i. Locations of minimum alternating stress ratios, SR-a_<4, at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-a values at welds in Table 9b. This view shows locations 2, 3, 6, 7, 17 and 18.

85

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 16j. Locations of minimum alternating stress ratios, SR-a<4, at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-a values at welds in Table 9b. This view shows locations 7, 9, 11, 14 and 15.

86

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Figure 16k. Locations of minimum alternating stress ratios, SR-a<4, at welds for 110% OLTP operation with frequency shifts. The recorded stress ratio at a node is the minimum value taken over all frequency shifts. Numbers refer to the enumerated locations for SR-a values at welds in Table 9b. This view shows locations 9 and 11-15.

87

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information 5.4 Frequency Content The frequency contribution to the stresses can be investigated by examining the power spectral density (PSD) curves and accumulative PSDs for selected nodes having low alternating stress ratios. The accumulative PSDs are computed directly from the Fourier coefficients as n

k=1 where 6 (Ok) is the complex stress harmonic at frequency, 0ok. Accumulative PSD plots are useful for determining the frequency components and frequency ranges that make the largest contributions to the fluctuating stress. Unlike PSD plots, no "binning" or smoothing of frequency components is needed to obtain smooth curves. Steep step-like rises in X(o) indicate the presence of a strong component at a discrete frequency whereas gradual increases in the curve imply significant content over a broader frequency range. From Parsival's theorem, equality between X((oN) (where N is the total number of frequency components) and the RMS of the stress signal in the time domain is established.

The selected nodes are the ones having the lowest alternating stress ratios (at a weld) in Table 9b. These are:

Node 132385 - located at the base of the old bar left in place to support the steam dam. he associated PSDs are shown in Figure 17a.

Node 98802 - located at the bottom of the drain channel/skirt weld. The associated PSDs are shown in Figure 17b.

Node 104843 - located at common junction between the bottom edge of the inner hood, the middle base plate and the inner hood support. The associated PSDs are shown in Figure 17c.

Node 98791 - located at the top of the weld connecting the steam dam and the new support gusset. The associated PSDs are shown in Figure 17d.

Node 94004 - located on the inner hood/closure plate weld. The associated PSDs are shown in Figure 17e.

In each case, since there are six stress components and up to three different section locations for shells (the top, mid and bottom surfaces), there is a total of 18 stress histories per component.

Moreover, at junctions there are at least two components that meet at the junction. The particular stress component that is plotted is chosen as follows. First, the component and section location (top/mid/bottom) is taken as the one that has the highest alternating stress. This narrows the selection to six components. Of these, the component having the highest Root Mean Square (RMS) is selected.

For the limiting node the dominant frequency is 109.2 Hz. The same frequency appears in four other stress PSDs plotted in Figure 17 and is dominant in node 98791. Both locations are on components connecting to the steam dam and the dominant frequency lies in a range where the applied loads are simultaneously increased by the bump-up factors (the range 100-120 Hz) and 88

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information bias and uncertainty associated with the onset of standpipe resonance. Node 98802 has a dominant frequency at 61.1 Hz without shifting and 48.8 Hz with frequency shifting. Since the skirt has numerous modes the strong responsiveness to frequency shifting is expected. For node 104843 the dominant frequency is about 64 Hz with a second peak around 110 Hz. The latter peak scales with the bump-up factor in this range. Finally node 94004 contains a sharp peak at 59.5 Hz which coincides with the natural frequency of a low order mode involving the outermost panel of the inner hood.

89

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Node 132385 c 600 500 400 C,)

(-

W) 300 E

E 200 100 0

0 50 100 150 200 250 Frequency [ Hz]

C, U) Node 132385, arzz 10 5

4

... o,s ~

10 0%shift 1000 (D

100 10 1

0.1 0.01 0 50 100 150 200 250 Frequency [ Hz ]

Figure 17a. Accumulative PSD and PSD of the azz stress response at node 132385.

90

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Node 98802 aYY 800 700 -- - - - - --- --Z--

CL 600 500 a-400 ........----------

E E 300 200 100 0

0 50 100 150 200 250 Frequency [ Hz ]

Node 98802, aYY 106 5

10 N

M 104 1000 C)

U) 100 U) 10 1

0.1 0.01 0 50 100 150 200 250 Frequency [ Hz ]

Figure 17b. Accumulative PSD and PSD of the cyyy stress response at node 98802.

91

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Node 104843 a 700 600 a_ 500 (D,

400 E 300 E

03 0 +5%shift 200 100 0

0 50 100 150 200 250 Frequency [ Hz]

Node 104843, a 106 105 104 1000 (n 100 U) 10 1

0.1 0.01 0 50 100 150 200 250 Frequency [ Hz ]

Figure 17c. Accumulative PSD and PSD of the cyxx stress response at node 104843.

92

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Node 98791, a YY 500 400 U) 300 (L,

E E 200 100 0

0 50 100 150 200 250 Frequency [ Hz ]

Node 98791, ar yy 10 5 10 4 1000 N) a-U_

100 C,,

10 1

0.1 0.01 0 50 100 150 200 250 Frequency [ Hz ]

Figure 17d. Accumulative PSD and PSD of the cyyy stress response at node 98791.

93

This Document Does Not Contain Continuum Dynamics, Inc. Proprietary Information Node 94404 a yy 600 500 -.

400 -- - --- -- -- -- _ - - - - --_ -_- -- -- - - - -

U)

C-0)

-5 300 E

E --- *-No shift C. 200 -2.5% sh 100 0

0 50 100 150 200 250 Frequency [ Hz ]

Node 94404, a YY 106 5

10 No shift7 N

104 1000 U,

CL 100 10 1

0.1 0.01 0 50 100 150 200 250 Frequency [ Hz ]

Figure 17e. Accumulative PSD and PSD of the ayy stress response at node 94404.

94

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

6. Conclusions A frequency-based steam dryer stress analysis has been used to calculate high stress locations and calculated / allowable stress ratios for the Browns Ferry Unit 1 steam dryer at 110% OLTP load conditions. A detailed description of the frequency-based methodology and the finite element model for the BFN1 steam dryer is presented. The CLTP loads obtained in a separate acoustic circuit model [2], including end-to-end bias and uncertainty for both the ACM [3] and FEA, were applied to a finite element model of the steam dryer consisting mainly of the ANSYS Shell 63 elements, brick continuum elements, and beam elements. The resulting stress histories were analyzed to obtain maximum and alternating stresses at all nodes for comparison against allowable levels.

For added conservatism, no low power-based signal filtering is attempted in the current analysis. The 110% OLTP stresses are estimated using two methods. The first scales the CLTP stresses by the square of the steam flow velocity ratio, (UI O/UCLTp) 2=1. 10. At CLTP the limiting alternating stress ratio is SR-a=2.33. Hence, using the first method the limiting alternating stress ratio at 110% OLTP is SR-a=2.33/1.10=2.12. The second method utilizes the bump up factors developed in [24] over the 100-120 Hz frequency interval and the velocity scaling (1.10) at all other frequencies. The stress ratios resulting from the application of 110% OLTP loads to the steam dryer are tabulated in Table 9 of this report. Using the second method the limiting alternating stress ratio is found to be SR-a=2.01. In both cases the alternating stress ratio remains above 2.0, thus qualifying the steam dryer for EPU operation with regard to stress evaluation.

On the basis of these CLTP plant loads, the dynamic analysis of the steam dryer shows that the combined acoustic, hydrodynamic, and gravity loads produces the following minimum stress ratios (with the T-bar excluded).

Frequency Minimum Stress Ratio at 110%

Shift OLTP Max. Stress, Alternating Stress, SR-P SR-a 0% (nominal) 1.44 2.01

-10% 1.47 2.77

-7.5% 1.41 2.27

-5% 1.42 2.14

-2.5% 1.40 2.16

+2.5% 1.42 2.15

+5% 1.39 2.09

+7.5% 1.39 2.13

+10% 1.40 2.19 All shifts 1.39- 1.47 2.01 -2.77 Limiting 1.39 2.01 95

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

7. References

1. Continuum Dynamics, Inc. (2005), Methodology to Determine Unsteady Pressure Loading on Components in Reactor Steam Domes (Rev. 6), C.D.I. Report No. 04-09 (Proprietary).

2. Continuum Dynamics, Inc. (2009), Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level to 110% OLTP Power Level on Browns Ferry Nuclear Unit 1 Steam Dryer to 250 Hz, Rev. 0, C.D.I. Report No.09-22P (Proprietary).

3. Continuum Dynamics, Inc. (2007), Methodology to Predict Full Scale Steam Dryer Loads from In-Plant Measurements, with the Inclusion of a Low Frequency Hydrodynamic Contribution,C.D.I. Report No.07-09P (Proprietary).

4. Continuum Dynamics, Inc. (2009), Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer with Tie-Bar Modifications,Rev. 3, C.D.I. Report No.08-15P (Proprietary),

March.

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