ML052490204
| ML052490204 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 06/16/2005 |
| From: | Henrie D, Kaul M General Electric Co |
| To: | General Electric Co, Office of Nuclear Reactor Regulation |
| References | |
| -RFPFR, dkh0513, eDRF-0000-0039-4747 GE-NE-0000-0041-9435 | |
| Download: ML052490204 (9) | |
Text
ENCLOSURE 2 Attachment 9 GE Report GE-NE-0000-0041-9435, "Quad Cities 1 & 2 Steam Dryer Replacement- 4% Structural Damping for Steam Dryer Skirt FIV Analysis," dated June 16, 2005
GE NUCLEAR ENERGY
- Structural Analysis and Hardware Design
'6705 Vallecitos Road, Sunol, CA-94586-9525.
June 16,2005 cc: 'M. R. Schrag.
- dkhO5l3 M. K. Kaul.
Report No. GE-NE-0000-0041-9435 C. E. Hinds KW. Wu TO: GE Nuclear Energy DRF No.: eDRF-0000-0039-4747
- FROM: D. K. Henrie
SUBJECT:
Quad Cities I & 2 Steam Dryer Replacement - 4% °Structural 'Damping
-for Steam Dryer-Skirt FIVAnalysis.
REFERENCES:
(ij GE Nuclear Energy.L;etter Report GE-NE-0000-.0039-4i49,-from D..K. Henrie to J. Klapproth, "Exelon Steam Dryer Replacement Program-.2% structural Damping for~Seismaic and Non-Seismnic (FI.) Dynlamic- Anlyis", March'18, 2005. {(dk0503)
(2).GE Nuclear Energy, Calculation'No. eDRF-Section 0000-0034-4855, "Daping Value ,for Steam' Dryer Structural Dynamic Analysis", Richard Wu,'November
.5, 2004.
(3) GE Nuclear Energy -Generic Design Specification No. 386HA596, Rev. 0,
'ODynamic Load Meihods &.Criteria -NSSS Equipment, Piping,'RPV &
Internals", Issued July 2, 1986. '(GE Proprietay)
~(4) US Atomic-Energy Commission' Regulatory iGuide .'l61, 'Damping Values for
'Seismic'Design'.ofNuclearPowerPPlants",.October 1973.
(5) Quad Cities UFSAR.
Quad Cities &2 Dyer Replacement -.4% DampingforDrjyerSkirt FIVDynamicAnalysis 7papelg
-~ (6)-GE~NiTNFEnergy LeItRer{pWrfGE-NE;0000-0039--4768, from:D. K Henrie to DRF NoiSection: eDRF-0000-0039-4747/4768, "Quad Cities 1 & 2 Steam Dryer Replacement - 4% structural Damping for Vane Bank FIV Analysis",
April21,, 2005. (dkb0507)
(7) GE Nuclear Energy Report GE-NE-'0000-0039-5860-01-P, Rev. 1, 'Test and Analysis Report - Quad 'Cities 'New Design Steam Dryer - Dryer .#1 Experimental .Modal Analysis and Correlation -with Finite'Element:Results"',
May 2005.
(8) GE Nuclear Energy'Report .GE-NE-0000-0041-' 656-'01-P, "Test ,and Analysis Report'- Quad Cities New Design Steam Dryer -. Dryer #2 Experimental Modal Analysis and Correlation with'Finite Element Results", May 2005.
1.0 PURPOSE, This letter report provides Zthe recommendation and technical justification for the structural damping to'be utilized in the ongoing structural design adequacy evaluation of the 'Quad Cities 1 &:2 replacement dryer skirt. The recommended damping is to be used for'theFIV 'load case, direct integration, time history analyses conducted by GE Nuclear Energy forQuad Cities 1 &
2.
2.0 CONCLUSION
S Based on the.present evaluation, it is concluded that an equivalent, linear viscous damping value, corresponding to '4.0% of critical damping, can be conservatively used for the FIV structural design adequacy.analyses required for the Quad Cities '.1 &2 replacement dryer-skirts. Thie'technical basis for this conclusion is provided below.
The details of the present evaluation, as well as evidence of verification, are documented in the GE Nuclear Energy'Design Record File, DRF No. 0000-0039-4747, "Section 0000-0041-9435.
3.0 DRYER SKIRT DAMPING BASED ON TECHNICAL:LITERATURE The technical justification 'for the structural damping' used in the.overall seismic (OBE and.
SSE) and dynamic (FIV) structural integrity design adequacytevaluation for the Quad Cities 1 and 2 replacement steam 'dryers is -provided in References 1 through 3 and. 6. The. -Quad Cities structural damping, licensing requirement for all primary structure components, except the RPV and internals, is given in Reference-5 and the RPV and internals requirement in Reference`3.
.Quad Cities 1&2 Dyer Replacement -4%o DampingforDryerSkirt FJI'DynamicAnialysis . Page?2
-3.1 US NRC Regulatorv Guide 1.61 'Damping.' Table 1 of Regulatory :Guide 1.61, Reference 4, tabulates modal damping values acceptable to the US NRC for the analysis and design of nuclear power plant seismic Category I struictures, systems and components. The damping values in Table .1 are given in terms of percent of critical damping and are acknowledged to be conservative. *Referring to Subsection C.2 of the guide, "Damping values higher thanJ the ones' delineated in Table I my be used in a dynamic seismic analysis if
.documented test. data are provided to support higher values.'7 Conversely, the following caveat is also given in Subsection C.3 of the guide: "If the maximum combined stresses.due to static, seisnic andother dytiamic loading aresignificanitly lowver than thie.yield stress and-Y/ yield stressfor SSE and Y 2 SSE, respectively, in any structure or component, damping values lower than those specifled in Zable. .of this guide should be usedfor.that structure or component to avoid underestimatingthe amplitude of vibrations or dynamic stresses."
In particular, the.-damping-values contained in Table 1 of.the guide are' highly dependent on:
(i) the material and structural characteristics of the stricture or component, and '(ii) 'the dynamic excitation level to which the structure or. component is subjected (hence -the excitation level to which it responds). With regard to material and structural characteristics,.
the dryer skirt corresponds to a welded steel structure. With regard to excitation level (hence response level), damping values are provided in Table 1 for OBE and SSE levels of excitation.
Referring to Table 1 of the guide for:a welded steel structure, the conservative value of damping for the OBE level of excitation is 2% of critical and that 'for the. SSE level of excitation is 4%. From the current, ongoing'FlV analysis for the Quad Cities-2 replacement dryer skirt, -the maximum stress 'at multiple' locations in the skirt corresponding 'to 2%
damping is 14,590 psi and corresponding to 4% damping: is 10,800 psi. At 5450F, the yield stress for SS304L is '15,940'psi. It 'then fellows that in.'the,.dryer skirt the 'maximumFIlV stress, corresponding to 2% structural damping, is equal to 0.92 ofyield and for-4% structural damping,-the dryer skirt maximum stress is equal to 0.68 of the yield stress, a response that is more representative of SSE excitation.
-Based on the foregoing discussion, it then follows rom Table 1 of Regulatory Guide '1.61 that the structural damping level for'a welded steel structure subjected -to the. SSE level of
' excitation :(hence, the SSE level of response). is-appropriate for the dryer skirt FIV analysis.
-Therefore, -it is concluded that 4% structural damping is appropriate for the FIV -design adequacy evaluation of the Quad Cities '1 & 2 replacement~steam dryer skirt.
Two finally observations are now rmade. .:First, it is noted that the damping values given in Table I of the guide all correspond to the vibration of the dynamically excited structures and components in the air. The corresponding damping values if the structures are submerged in water will be significantly higher. Because .at least two'-thirds of the dryer skirt is submerged at low water level, 4% damping is even more conservative.
QuadCities 1&2 DryerReplacement- 4% .DampingforDryer Skirt FIVDynamicAnalysis -Page3
Second, it is also noted that per-the caveat quoted above, the maximum combined stress to be compared to the yield'istress is, due to static, seismic, and other dynamic loadings (i.e., FIV loadings). The istresses ited above in te'rms of the yield stress fotr 2% and 4% structural damping correspond to only FIViloading which occurs during normal plant operation.
3.2 Ouad Cities/Dresden UFSAR Damping.- The damping values provided in Tables 3.7-1 of the Quad Cities and Dresden .UFSARs correspond to design licensing basis values to be applied to all safety related structures, components and equipment in the plants except-ithe RPV internals and the RPV stabilizer. The footnote in Table 3.7-1 in the Dresden UFSAR reiterates that the design licensing basis damping values for the RPV :and internals and the RPV stabilizer are GE'Nuclear Energy proprietary and "areprovided in GENE-771-84-1194, Revision 2", prepared by GE Nuclear Energy for the Dresden shroud repairs.
3.3 GE Nuciear Enerey Methods & Criteria Document Damping. The RPV intemalsi damping values provided 'in the- above'referenc'ed GENE report are' based onrthe GE Nuclear' Energy Methods and 'Criteria 'document, Reference 3. The seismic damping values are contained inTable 5.8.11 and thenonseismic damping values in Table 5.8.2-1 ofReference
- 3. Similar to Regulatory Guide 1.61 damping, the design licensing basis damping values' contained in Reference 3 are dependent on the material and structural characteristics of the structure or component being excited as well as on the'level of the excitation (hence the level of the response). However, differing from Regulatory Guide'1.61, selected damping values contained in Reference 3 are also dependent on the direction, horizontal or vertical, in which the structure or component is excited.
Also, similar to the' OBE level of excitation in Regulatory Guide '161; 'the seismic'damping values in Table 5.8.1-1, designated as OBE, and the nonseismic damping values in Table5.8.2-l, designated as Normal or Upset, are to be-used in the structure or component dynamic analysis in which the resulting maximum stresses are at, or not significantly below, the one-half-yield stress. Again, similar to the SSE level of excitation in Regulatory Guide
'1.61,the seismic damping values inlTable 5.8.1-1, designated as SSE- and the nonseismic damping values in Table5.8.2-1, designated as Em'ergency'or Fa'ilted, are to be 'used inithe structure or component dynamic analysis if the resulting maximum stresses are significantly above the one-half the yield stress and not significantly below'the yield stress.
Referring to Table 5.8.2-1 of Reference 3, for a'welded steel structure -subjected to'the Emergency or Faulted level of excitation (hence, level of response), the appropriate structural damping is 4% of critical. Therefore, it is concluded that 4% structural damping can be conservatively applied in the FIV structural design adequacy 'evaluation of the Quad Cities i
& 2 and the Dresden 2 and'3 replacement steam dryer skirts. The result is the same as that for Regulatory Guide 1.6i
- Quad Cities 1&2 Dryer Replacement- 4% DampingforDryerSkirt FIVD.ytiamIcAnalysis Page-4
4.0 DRYER SKIRT DAMPING BASED ON HAMMER TEST DATA The.results of the.hammer tests, just completed for the Exelon replacement steam dryers I and -2,' are summarized in Referen'ces 7 and 8, respectively. The primary purpose of ;the hammer test is to identify the natural frequencies of the dryer assemblies. The 'vibration test data generated by the.hammer test can also be utilized to determine representative, lower bound values of the structural damping inherent 'to the steam dryer assemblies. The (i)
Logarithmic Decrement, (ii) Half Power Bandwidth (or equivalent), Iand (iii) Modal Curve Fitting (Individual FRFs), and (iv)'Modal -Curve Fitting (Whole Component) methods were all applied in References 7 and 8 to the hammer test data to generate approximate, lower bound structural damping values for the steam dryer hoods and skirts.
4.1 Conservatism Inherent to Dampin'2'Values Based on Hammer Tests. Typically, the hammer test is performed using a 2 lb to 3 lb soft tipped (load cell) hammer that is used to gently tap (impact) the dryer assembly. There is no metal-to-metal contact. The 'impact test should not cause local damage to the'dryer surfaces, e.g., no"dents or scratches. Furthermrore, care is taken not to damage the installed sensors and the sensor leads.
From-this description, it is clear that during the hammer test the excitation'level, deformation, strain, stress, displacement, velocity'; strain rate, etc., are all essentially zero. However as discussed in Subsections 3.1 and 3.3 above, the dampingimagnitude. irlherentto a structure or component is'highly correlated to its.excitation (hence response) level. Typically, the greater the excitation level'the greater the structural damping magnitude; however, the correlation between the two is nonlinear.
Based on the foregoing discussion, 'it is concluded that the damping coefficients generated, based on hammer test vibration data, will correspond .to very conservative, lower bound values wvhien. compared to the actual damping characteristics inherent to {he replacement steam dryer assembly during normal plant operation.
4.2 Dryer Skirt FV Response Characteristic Frequencies. The maximum strain '(stress) in the dryer skirt due to the FIV loading associated with the Quad Cities 2 post startup main.
steam line'data: taken at 2885 MWt, occurs at Node 66818 "ofthe steam' dryer. assembly'Finite Element Model (FEM). Thelfrequency content of the corresponding strain (stress) time history, that is calculated at Node'66818 ifi'the associated GE 1% structural damping, direct integration, time history analysis of the 'dryer FEM, is obtained from the FFT of that time
'history. The.dominant characteristic frequency associated with the dryer. skirt:maximum strain (stress), defined in the corresponding'strain time history'FFTIplot, is in the range 25Hz to'35Hz.
-4.3 Dryer Skirt Damping from Hammer Tests. Refening to Table '1 ofReference 7 for Dryer`#1 and Tablela o6f Referenice8 for`,Dryer.#2, it is observed that the dryer skirt hammer' test calculated damping values vary dramatically depending on: (i) the frequency at which the damping is calculated is calculated, and (ii) which of the four.methods mentioned above are
- applied in the damping calculation.
Quad Cities1&2 Dryer Replacement - 4% DampingforDryerSkirt FIY Dynamic Analysis Page5
The damping in terms of percent critical damping in Dryer #1, Reference, 7, ranged from 0.2% to 7.7% on the 90° skirt panel, with the higher frequencies generally showing lower
'daniping. The 270 'skir panel shoWed 'a'similar trend, 'with a damping range of 0.4% to 13%. In general, the skirt damping values generated based on strain gage hammer test data were slightly higher than the corresponding damping values generated based on accelerometer harmmer test data.
For Dryer #2, Reference 8, the damping in terms of percent critical damping. for the individual FRFs ranged from 0.2% to 3.7% on the 900 skirt panel, with'the higher frequencies generally showing lower damping. The 2700 skirt panel showed a similar trend, with a damping range of 0.5% to.'5.6%. In general, the skirt damping values. generated based on strain gage hammer test data were slightly higher than the corresponding damping values generated based on accelerometer hammer test data.
'The procedure consisting of the four steps 'defined below is applied to the hammer' test damping values contained in Table 1 of Reference 7Sand Table Ia of Reference 8 to obtain an appropriate damping value which can'be conservatively applied in the 'Quad Cities 1 & 2 FIV structural design adequacy evaluation of the replacement steam dryer skirt..
Step 1: Consistent 'with the conservatism inherent to damping values that are calculated based on hammer.test data (discussed in Subsection 4.1 above), when a range of damping values is calculated at a given, frequency by any one of the four methods notedat'the beginning of Section 3.0, the maximum damping value in the range is 'taken as the damping value calculated bybthat method for that frequency.
Step 2: Whenever more than-one of the four.methods are applied to calculate dryer skirt' damping value at a given frequency, the damping value at,'that frequency is :taken.as the average of the damping values calculated by the methods applied.
Step *3: Whenever 'damping values .are calculated at multiple frequencies which fall in the frequency range of the dominant characteristic frequency of the dryer maximum strain (stress); the damping value for the 'entire :frequency range can be taken as the average of the damping values calculated for each'individual 'frequency in the range.
Step 4: The dryer skirt damping can be taken -as the damping-obtained'by'applying Step I through 'Step 3 for the frequency -range which 'is equal to the dominant characteristic frequency range of the dryer skirt maximum strain (stress) as discussed in Subsection 4.2
'above.
The .dryer skirt structural damping, based ion' hammer test data, is now approximated. for
- Dryer#1 and .Dryer #:.2 by applying Steps I 'through 4 above to the hammer test .data contained in Table: of Reference. 7 and Table la of Reference 8, respedtively. Theresulting damping values are tabulated in Table I below.
QuadCities 1&2DryerReplacementt- 4% DampingforDrer Skirt FIVDyynamicAnalysis Page6
TABLEI Dryer Skirt.Structural Damping
, - (% of.Critical)
'Dryer #1 Dryer #2 900 SkirtPancl 4.76% 2.533%
.2700 Skirt Panel 5.71% 1.50%
4.4 Discussion' Drver Skirt Damping Results "from Hammer Tests. 'Because the vertical plane that contains the dryer assembly horizontal '0° - .1800 axis corresponds to a structural plane of symmetry, it.'is-expected that -the damping values on the 900 Skirt Paneis and the 2700,Skirt Panels would be the same. :Also, because the'strucitural characteristic of Dryer #1 and Dryr:#2 are essentially identical it was also expected that damping values for the two dryers would be the same.
The apparent, differences can be partly explained by cdomparing Table 1 from Reference 7 with Table la from Reference 8. In comparing the two tables, it. is observed that: (i) the damping values were not.generally calculated at the same 'frequencies for the-two 'dryers, (ii) the damping values were generally not'calcuIated using the samemethodology for the two dryers, and (iii) for the same dryer, the'damnping values were not generally'calculated 'at the same. frequencies for, the 900. and 'the'2700 skirt panels even though the -same methodology was applied. This"does not fully explain the differences because there are several cases' for which the dissimilar .damping.Values were calculated at the same time point using the same methodology for the two dryers. 'Probably there are:also some-differences in the test setup or how "the'tests were performed between the two dryers or betwveen'the two dryer skirt planes for the same dryer.
The Dryer #1,'hammer'based, damping values given in Table'l above 'for the 90 skirt panel and the 1800'skirt panel are sufficient to justify 4% structural damping for the Quad Cities 2 dryer 'skirt structural design adequacy -evaluation for the FIV load case. Based on Ahe
'foregoing discussion, the justification can also be applied to the 'Quad Cities idryer skirt.
Quad Cities1&2 DyerReplacement-'4% DampingforDryerSkirt FlVDynainicAnabysls Page 7
5.0
SUMMARY
OF EXELON REPLACEMENT DRYER ASSEMBLY DAMPING From the foregoing discussion -it is recommended that. 4% structural damping be conservatively applied for the FIV structural integrity evaluation of the dryer assembly skirt.
The FIV structural integrity of: (i) the steam dryer RPV vessel lugs, -and (ii) the dryer upper assembly (excluding the vane banks, Reference 6) will still be based on 2% structural damping for the dryer assembly, Reference l. Also,'the FIV structural integrity evaluation of all other steam dryer assembly components will be based on 1% structural darnping in the steam dryer assembly, Reference 2..
-Based on the present evaluation, it is concluded that -an equivalent linear viscous modal damping value of 4.0% of critical damping can be conservatively applied for direct integration time history analyses of the replaceinent steam dryer skirt for Quad Cities I & 2 for the FIV dynamic load case. The technical basis for this recommendation is presented above.
If there are any questions, or if I can be of additional help, please call me at (925) 8624350 or on my cell phone at (408) 204'6244.
D.K. U Technical Leader Structural Analysis & Hardware Design Seismic & Dynamic Analysis Verifiedby: _______
M. K. Kaul, Principal Engineer Structural Analysis &Hardware Design Seismic & Dynamic Analysis Quad Cities 1&2 Dryer Replacement - 4% DampingforDryer Skirt F1VDynamlcilhalya1s Page8