ML080380560
| ML080380560 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/31/2008 |
| From: | Langley D Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MD5262, TAC MD5263, TAC MD5264, TVA-BFN-TS-418, TVA-BFN-TS-431 | |
| Download: ML080380560 (121) | |
Text
{{#Wiki_filter:Tennessee Valley ALthority, Post Office Box 2000, Decatur, Adabama 35609-2000 January 31, 2008 TVA-BFN--TS-418 TVA-BFN-TS-431 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop OWFN, Pl-35 Washington, D. C. 20555-0001 Gentlemen: In the Matter of ) Docket Nos. 50-259 Tennessee Valley Authority ) 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - UNITS 1, 2, AND 3 - TECHNICAL SPECIFICATIONS (TS) CHANGES TS-431 AND TS-418 - EXTENDED POWER UPRATE (EPU) - RESPONSE TO ROUND 15 REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING STEAM DRYER ANALYSES (TAC NOS. MD5262, MD5263, AND MD5264) By letters dated June 28, 2004 and June 25, 2004 (ADAMS Accession Nos. ML041840109 and ML041840301), TVA submitted license amendment applications to the NRC for the EPU of BFN Unit 1 and BFN Units 2 and 3, respectively. The proposed amendments would change the operating licenses to increase the maximum authorized core thermal power level of each reactor to 3952 megawatts. By letter dated July 27, 2007 (ML072130371) TVA submitted the completed BFN steam dryer stress analyses for Units 1, 2, and 3. On December 14, 2007, the NRC staff issued a Round 15 RAI (ML073450725) regarding the EPU license amendment requests. TVA replied to Round 15 RAIs APLA.38/40, SRXB.71, and SRXB.72 by letter dated January 25, 2008. Enclosure 1 to
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U.S. Nuclear Regulatory Commission January 31, 2008 this letter addresses the remaining Round 15 RAIs regarding the steam dryers. Some of the RAIs require additional research and analysis to fully provide the requested information. For the affected RAIs, schedule dates for completing the responses are provided in the enclosure. Please note that the information provided in Enclosure 1 contains information that Continuum Dynamics, Inc. (CDI) considers to be proprietary in nature and subsequently, pursuant to 10 CFR 2.390(a) (4), requests that such information be withheld from public disclosure. Enclosure 2 contains the redacted version of Enclosure 1 with the CDI proprietary material removed, which is suitable for public disclosure. Enclosure 3 is an affidavit from CDI supporting this request. TVA has determined that the additional information provided by this letter does not affect the no significant hazards considerations associated with the proposed TS changes. The proposed TS changes still qualify for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c) (9). No new regulatory commitments are made in this submittal. If you have any questions regarding this letter, please contact me at (256)729-2636. I declare under penalty of perjury that the foregoing is true and correct. Executed on this 3 1 st day of January, 2008. and Industry Affairs
U.S. Nuclear Regulatory Commission Page 3 January 31, 2008
Enclosures:
- 1. Response to Round 15 Request for Additional Information (RAI) Regarding Steam Dryer Analyses (proprietary version)
- 2. Response to Round 15 Request for Additional Information (RAI) Regarding Steam Dryer Analyses (non-proprietary version)
- 3. CDI Affidavit
U.S. Nuclear Regulatory Commission Page 4 January 31, 2008 Enclosures cc (Enclosures): State Health Officer Alabama State Department of Public Health RSA Tower - Administration Suite 1552 P.O. Box 303017 Montgomery, Alabama 36130-3017 NRC Senior Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, AL 35611-6970 Branch Chief U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 Eva Brown, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9) One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739
ENCLOSURE 2 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2, AND 3 TECHNICAL SPECIFICATIONS (TS) CHANGES TS-431 AND TS-418 - EXTENDED POWER UPRATE (EPU) - STEAM DRYER ANALYSIS REVIEW RESPONSE TO ROUND 15 REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING STEAM DRYER ANALYSES (NON-PROPRIETARY VERSION) Attached is the non-proprietary version of the response to Round 15 RAIs regarding steam dryer analyses.
NON-PROPRIETARY INFORMATION RAI Round 15 EMCB Response Status and Schedule As discussed during our January 25, 2008, meeting with the NRC, some of the Round 15 RAIs require additional research, analysis, and resolution of issues to fully provide the requested information. The following table provides the status of the responses to the Round 15 RAIs related to the BFN steam dryers and the schedule for completing the remaining responses. Additionally, the stress analyses associated with the Unit 1, 2, and 3 steam dryers are being re-performed to address several aspects which were discussed during the January 25, 2008, meeting. The revisions to the steam dryer analyses will include the following.
" Revision of the Unit 1 and Unit 3 steam dryer stress analyses utilizing a load definition based on unit-specific main steam line (MSL) strain gage data. See RAIs EMCB.130/97 and EMCB.140/107.
- Correction of the finite element models (FEM) as described in the response to EMCB.133/100.
- Resolution of outstanding issues with the bias and uncertainty that should be applied. See RAIs EMCB.141/108, EMCB.142/109, and EMCB.143/110. The schedule for completing the stress analyses is based on timely resolution of these issues with the NRC.
" Elimination of plant and sensor noise based on no-flow MSL strain gage data.
Based upon anticipated timely resolution of the outstanding issues and revision of the BFN steam dryer analyses, the revised steam dryer stress analyses are currently planned to be provided by March 6, 2008 (Unit 1), March 2008 (Unit 2), and June 2008 (Unit 3). EMCB Response Schedule for Comments Provided Completed
Response
129/96 130/97 $ 6/2008 Will perform Unit 3 stress analysis using Unit 3 data 131/98 3/31/2008 132/99 1/ 133/100 V/ E2-1
NON-PROPRIETARY INFORMATION EMCB Response Schedule for Comments Provided Completed
Response
134/101 vw 3/6/2008 Provides clarification of question 135/102 V1 136/103 3/31/2008 137/104 3/31/2008 138/105 V 3/6/2008 Provides clarification of question 139/106 / 3/6/2008 Provides clarification of question 140/107 V 3/6/2008 Will perform Unit 1 stress analysis using Unit 1 data 141/108 V/ 142/109 V1 143/110 VI 144/111 3/6/2008 145/112 V 3/6/2008 Provides clarification of question 146/113 1/ 3/31/2008 Provides clarification of question 147/114 V 148/115 V/ 149/116 V/ 150/117 V 151/118 V/ 152/119 V 153/120 V1 154/121 V 155/122 3/6/2008 156/123 3/6/2008 157/124 3/6/2008 158/125 3/6/2008 159/126 3/6/2008 160/127 3/6/2008 161/128 3/6/2008 162/129 3/6/2008 163/130 3/6/2008 164/131 V 165/132 V" 3/6/2008 Will provide Unit 1 limit curves using Unit 1 data 166/133 V" Ul - 3/62008 Will provide limit curves for Units 1, 2, U2 - 3/2008 and 3 U3 - 6/2008 E2-2
NON-PROPRIETARY INFORMATION NRC RAI EMCB.129/96 The 218 hertz (Hz) tones in the Browns Ferry Nuclear (BFN) plants caused by the blind flanges were predicted prior to main steam line (MSL) measurements in Table 1 on page 23 of GENE-0000-0052-3661-01, Test Report #1, Browns Ferry Nuclear Plant, Unit 1, Scale Model Test of Enclosure 1 to a letter dated April 13, 2006. The table also shows that main steam relief valve (MSRV) tones may occur near 120 hertz Hz in Unit 1, and the report states that the MSRV tones will be strongest just below extended power uprate conditions. Strong safety relief valve (SRV) tones have been shown to be detrimental to steam dryers in nuclear power plants based on the experiences at Quad Cities. (a) Provide an assessment of whether the 120 Hz tone might also appear in Units 2 and 3. The assessment should include detailed MSL and valve specifications, along with an analysis Of the potential resonances and the MSL flow speeds at which may be excited. (b) Discuss how Tennessee Valley Authority (TVA) will address the appearance of any strong MSRV tones in any of the BFN Units that challenge dryer stress limits. This discussion should include any plant data which shows that the tones, if they appear, will not be strong enough to drive dryer stresses above the American Society of Mechanical Engineers Code fatigue limit. (c) Since the tones may appear near 120 Hz (one of the
'exclusion frequencies' used by Continuum Dynamics Incorporated (CDI) to filter electrical noise from MSL measurements), explain how the MSRV tones will be differentiated from electrical noise so they are not filtered.
TVA Response to EMCB.129/96 (a) Calculation of vortex shedding and 1/4 wave frequencies of the SRV branch connections for BFN Units 1, 2, and 3 indicate that resonance onset is possible at current licensed thermal power (CLTP) through EPU conditions at 105 Hz. Similarity between units is such that susceptibility is equal. TVA has conducted further MSL resonance testing at 1/5 scale in CDI's test facility using Unit 1 specific E2-3
NON-PROPRIETARY INFORMATION dimensional detail. Results show the SRV resonance to be at 111 Hz with onset just after CLTP. Actual SRV resonance is not present in plant testing at CLTP conditions based on MSL data on Units 1 and 2. CLTP velocities are M = 0.087 (139 ft/sec), and EPU velocities are M = 0.1 (160 ft/sec estimated). Figure EMCB.129/96-1 provides the SRV and standpipe layout on the MSLs and Figure EMCB.129/96-2 provides a schematic of the SRVs and blind flange standpipes. Component as-built locations were provided for each steam line in Table EMEB.125/92-1 in the TVA letter dated November 21, 2007, "Browns Ferry Nuclear Plant (BFN) - Units 1, 2, and 3 - Technical Specifications (TS) Changes TS-431 and TS-418 - Extended Power Uprate (EPU) - Response to Preliminary Findings on Steam Dryer Stress Analysis" (ML073330483). E2-4
NON-PROPRIETARY INFORMATION Figure EMCB.129/96-1 Schematic of the four Main Steam Lines at Browns Ferry Unit 1 Unit 1 dimensions A MSL SR Elbow 2.646' b 4.958' 0 3125' 0 6.250' 3 167' - 4 3.080' B MSL Dead Leg C MSL D MSL SR Elbow E2-5
NON-PROPRIETARY INFORMATION Figure EMCB. 129/96-2 Schematic of SRVs and Blind Flange Standpipes 6.0 19 5.185 20 +/-0.3 1 20 +/- 0.3 V 1.0 r 1.0 r SRV & Standpipe Blind Flange Standpipe Shaded area represents acoustic chamber Dimensions in inches E2-6
NON-PROPRIETARY INFORMATION (b) TVA is proceeding with further scaled testing. The purpose for the 1/5 scale tests was to determine if SRV resonance onset is possible within the EPU operating range based on the typical valve locations and flow rates. However, peak resonance is not expected until approximately 184% of CLTP. Further testing is needed to determine the relative increase due to resonance that may occur between CLTP and EPU. The next test configuration to be employed is the 1/8 scale tests that include replication of all four MSLs with all SRVs, dead legs, and de-tuned blind flanged standpipes. This testing is performed as a complete circuit utilizing a vessel and dryer replication in addition to the MSL piping to include the effects of vessel and piping resonance interaction. The purpose of the 1/8 scale test is to help predict increases in dryer stress that will be seen during power ascension testing from CLTP to EPU. (( 1] The projected EPU data will be evaluated through the Acoustic Circuit Model (ACM) and FEM analyses to predict EPU stress levels. Power ascension limit curves and published dryer stress margins will continue to be based on actual plant data and will not be affected by the "bump up" factor. Predicted EPU stresses for the Unit 1 and Unit 2/3 dryer designs will be considered in light of the available margin at CLTP and a decision will be made as to the need for additional modifications to the dryers or the steam lines to mitigate the effects of resonance. Unit 1 has already been modified and reinforced for a predominant SRV load at approximately 120 Hz derived from earlier analyses and, therefore, is less likely to be impacted. Units 2 and 3 have not received similar modifications and may be more susceptible. (c) The anticipated SRV excitation frequency is from 105 Hz to 112 Hz with the 1/5 scale tests indicating 111 Hz. Electrical noise exhibits itself in the MSL pressure data as narrow spikes centered on 60, 120 and 180 Hz. When E2-7
NON-PROPRIETARY INFORMATION these frequency spikes are processed by a Matlab function that uses a second-order stop-band Butterworth filter, the original signal is not affected outside a frequency width of +/- 1.0 Hz. The expected SRV resonance is quite removed from the electrical frequency and it would be difficult for this feature to mask a flow induced vibration signal, which has a frequency band that is typically three or four times wider based on industry experience. See for instance CDI Report No. 07-09P, Figure 6.1 (provided in Enclosure 3 of our letter dated July 27, 2007, "Browns Ferry Nuclear Plant (BFN) - Units 1, 2, and 3 - Technical Specifications (TS) Changes TS-431 and TS-418 - Extended Power Uprate (EPU) - Steam Dryer Evaluations"). Figure EMCB.129/96-2 provides examples of unfiltered and filtered data taken from the plant tests that demonstrate the narrow band of noise removal. If the actual resonance frequency is observed overlapping an electrical signal such as 120 Hz, the electrical noise spike will be manually truncated at the amplitude of the SRV response. This will prevent the filtering from affecting the magnitude of a resonance signal. E2-8
NON-PROPRIETARY INFORMATION Figure EMCB.129/96-2: MatLab comparison between an unfiltered BFN MSL signal (blue curve) and a narrow filtered signal (green curve) around 120 Hz. le
....... ... .... .. .. ... ........ .... .H -------- .... i z S..-- -...
10-ZZZ-Z----------------------------- ------- Original Signa------
........................................... ---- ..---.. . HzS p ike ---- ----
E i [ReoveH0 o -4 U) 10 CL 115 120 125 Fmqiency, I-t NRC RAI EMCB.130/97 During the upcoming Unit 3 Spring 2008 refueling outage, the eight unused standpipes in MSLs A and D, which are believed to cause strong 218 Hz tones in the plant on Unit 3, will be plugged. Additionally, the Unit 3 MSLs will be instrumented and the acoustic pressures will be measured. Provide the following information: (a) analyses or test reports that explain the nature of the 218 Hz tones, along with the proposed changes to the standpipes and a demonstration that the changes will eliminate the tones; (b) a revised stress analysis for Unit 3 based on the Unit 3 MSL strain gage measurements; and (c) limit curves for Unit 3 based on the stress results in item (b). E2-9
NON-PROPRIETARY INFORMATION TVA Response to EMCB.130/97 (a) The 218 Hz tone was previously discussed in the reply to EMEB.124/91 in the TVA submittal dated November 21, 2007. TVA has conducted further MSL resonance testing at 1/5 scale in CDI's test facility using Unit 1 specific dimensional detail. This testing provided additional substantiation that the blind flanges are the source of the resonance and that the planned modifications will eliminate the tones. Tests were conducted with and without the Acoustic Vibration Suppressors (AVS). This testing show that with the AVS installed, the resonance peak at 218 Hz is eliminated and that any new resonances created are at 331 Hz and at steam line flows far beyond EPU conditions. (b) TVA plans to install MSL strain gages and AVSs on Unit 3 during the upcoming Spring 2008 outage. MSL strain gage data will be taken following startup from the outage to provide input into a load definition for the Unit 3 steam dryer and to confirm the intended effects of the AVSs. A revised stress analysis for Unit 3 will be completed utilizing the load definition based on Unit 3 MSL strain gage data. The revised stress analysis will be performed with the same methodology used for the Unit 1 and Unit 2 stress analyses. Based on the planned outage and startup dates for Unit 3, the Unit 3 stress analysis utilizing Unit 3 MSL strain gage data is planned to be submitted in June 2008. (c) Following the completion of the Unit 3 stress analysis discussed in (b) above, Unit 3 steam dryer limit curves will be generated. The method to generate the limit curves will be the same as previously used in the generation of the limit curves submitted in TVA letter dated August 21, 2007, "Browns Ferry Nuclear Plant (BFN) - Units 1, 2, and 3
- Technical Specifications (TS) Changes TS-431 and TS-418 -
Extended Power Uprate (EPU) - Steam Dryer Limit Curves" (ML072360257). Based on the planned outage and startup dates for Unit 3, the Unit 3 steam dryer limit curves based on the revised Unit 3 stress analysis is planned to be submitted in June 2008. E2-10
NON-PROPRIETARY INFORMATION NRC RAI EMCB.132/99 Included in the TVA submittal is an MPR evaluation of BFN steam dryer analyses. MPR performed an independent third party review of reports provided to TVA by CDI. The MPR report was submitted to TVA on July 25, 2007. TVA is requested to provide the MPR report to the staff, along with any TVA responses and resolutions to the MPR questions and comments. TVA Response to EMCB.132/99 MPR reviewed draft reports prepared by CDI and generated comments which were provided to CDI for incorporation into the final reports. These comments were resolved through discussions, revisions to the reports, and MPR final review. As documented by the July 25, 2007, letter, MPR acknowledged that their comments were suitably addressed by the revised CDI reports. This letter will be made available for inspection. NRC RAIs EMCB.133/100 through EMCB.144/111 The following are associated with CDI Report No. 07-05P, "Finite Element Model for Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer to 250 Hz," which is Enclosure 1 of a letter dated July 31, 2007. NRC RAI EMCB.133/100 Identify the differences in the design and fabrication of Unit 1, 2, and 3 steam dryers including modifications. Also identify the differences in the steam systems for these three units including number of SRVs, blind flanges and elbows, their locations, and associated acoustic resonance frequencies. Also, identify the dead-ended branches that may be present in each unit and the associated acoustic resonance frequencies. Additionally specify whether verification of as-built configuration was conducted or is the information based on original design drawings. TVA Response to EMCB.133/100 Dryers: The original BFN steam dryers were all fabricated to the same design by the same vendor and fabricator. Subsequently dryer modifications have included: Welded reinforcement of the drain channels per General Electric (GE) SIL 474, "Steam Dryer Drain Channel Cracking," has been implemented on all units in the same manner. E2-11
NON-PROPRIETARY INFORMATION
" Dryer tie bars have been modified on Unit 1 and Unit 3 (center tie bars) . These modifications are different in design due to evolved improvements. Units 2 and 3 will have the latest tie bar modification design as has been installed on Unit 1 prior to EPU implementation.
- Unit 1 dryer has had the following additional modifications implemented for EPU:
o 3/8" cover plates replaced with a 1" thick cover plate o 1/2" hood face plates at 900 and 270' have been replaced with 1" thick bent and formed hood face plate. Two vertical stiffening channels have been added on each hood face as further reinforcement. o The two 1/4" vertical stiffeners behind each of the outer hood face plates were removed, such that the outer hood face plates were supported and braced only around the periphery. o The outside top vane bank plate weld has been reinforced with a revised weld design. o The support beam that runs across the dryer from the support rings, beneath the cover plates and vane banks, was modified such that the end sections beneath both the cover plates were removed.
- Units 2 and 3 dryer EPU designs currently do not incorporate the replacement of the cover plate and hood faces. Unit 2 and 3 dryer modifications currently planned include reinforcement with added weld of the cover plate to support ring/hood connection; installation of the latest tie bar design; and an increase in the cover plate manway fillet weld.
TVA's verification of the stress analysis FEM has identified discrepancies between the FEM and the actual design. Following is a listing of those discrepancies and the corrections required in subsequent analysis; Unit 1
" Cover plate was modeled as 1/2" thick; corrected FEM to 1" thick.
- Cover plate manway removed from FEM consistent with modification design.
E2-12
NON-PROPRIETARY INFORMATION
- Cover plate fillet welds to support ring changed to 3/4" in FEM, and evaluated as an undersized weld. Cover plate weld to outer hood changed to 1" thick in FEM.
- Outer hood vertical stiffeners have top covers, which were omitted from the model - corrected FEM by adding 1" thick covers welded on top.
- Dryer support restraint was modeled as a fixed restraint -
revised to a pin connection in the FEM to allow dryer appropriate degree of freedom at the four vessel lug support locations.
" The support beam was modeled as welded to the support ring
- corrected FEM to have the beam end sections removed from beneath the cover plate as was incorporated in the modification due to cracked welds.
Units 2/3
- The cover plate attachment welds were not evaluated as undersized welds in the initial analysis. TVA will reinforce these welds from 1/4" to 3/8" to remove the undersize weld configuration. Therefore, no model change is required.
- The cover plate was modeled as flat and the model has been corrected to include a 2" rise at the center of the cover plate to outer hood junction.
" Dryer support restraint was modeled as a fixed restraint -
FEM revised to a pin connection to allow dryer appropriate degree of freedom at the four vessel support locations Main Steam system configuration: Each of the three units contains thirteen SRVs and twelve blind flanged standpipes. For all three units, the A and D MSL are mirror images of each other and are the "outside lines" of the MSL piping exiting the drywell. The B and C lines are the "inside" MSLs, and also contain the piping deadlegs. B & C MSLs do not have any blind flanges in the active steam flow and also have two SRVs each installed near the ends of the dead legs (i.e., four total SRVs per unit not in the active steam flow). Figure EMCB.129/96-1 provides the Unit 1 dimensions of the SRVs, blind flanges and dead legs to the elbows and tees for each of the MSLs. Additionally, Table EMEB.125/92-1 (provided in the November 21, 2007 submittal) contains the dimensional differences for these components between each of the units. These dimensions are E2-13
NON-PROPRIETARY INFORMATION as-built dimensions taken during the NRC IE Bulletin No. 79-14, Seismic Analyses for As-built Safety-related Piping Systems, verification performed on each of the BFN units during the recovery process prior to restarting of the units. Calculations for resonance include the low frequency dead legs on the B and C MSL lines (15 Hz), the middle frequency SRVs and standpipes (105 Hz), and the high frequency blind flanged standpipes (221 Hz). NRC RAI EMCB.134/101 Describe the operating experience for each of the three units, especially the experience related to any fatigue cracking. The description should demonstrate that the frequency based approach used for the stress analysis of the steam dryer is consistent with the fatigue cracking experience. (Address whether the frequency-based approach shows peak stress locations in regions where cracking occurred.) TVA Response to EMCB.134/101 TVA has identified three locations on the Units 1, 2 and 3 steam dryers where previous damage has been observed that may be indicative of fatigue resulting from flow induced vibration. These locations are:
" Drain channel-to-skirt weld cracking
- Tie-bar fracture
" Dryer bank support beam-to-ring weld cracking TVA will evaluate the observed damage at these locations considering stresses or loads predicted by the frequency-based finite element analysis. It should be noted that the damage summarized above occurred in one or more of the BFN units during a period in time where the steam dryers reflected their original as-built configuration. Therefore, to ensure the best representation possible of the original dryer configuration, the existing Unit 2/3 model as described in CDI Report No. 07-06P (provided in Enclosure 2 of our July 27, 2007 submittal) will be used for correlation because of significant dryer modifications which have been incorporated into the finite element model for the Unit 1 dryer as described in CDI Report No. 07-05P (provided in Enclosure 1 of our July 27, 2007 submittal). In addition, the correlations will consider any modifications or repair actions that were incorporated to prevent recurrence of damage.
For example, the existing Unit 2/3 finite element model has E2-14
NON-PROPRIETARY INFORMATION incorporated a much more robust tie-bar design so the correlation will have to account for this difference to estimate stress in the original tie-bars. Stresses or structural loads used for correlation will be based on loading determined from Unit 2 data at CLTP conditions with the 218 Hz blind flange standpipe resonance included. This analysis, which is summarized in CDI Report No. 07-06P, is the best currently available representation of the loading conditions and imposed stresses under which the observed damage occurred. TVA will provide the results of this correlation by March 6, 2008. NRC RAI EMCB.135/102 Equation (6) in the CDI Report 07-05P provides estimates of stresses due to frequency shift. Provide derivation of this equation. TVA Response to EMCB.135/102 (( E2-15
NON-PROPRIETARY INFORMATION
)) Multiplication by the factor (1+X),
where X is the frequency shift, follows directly from the properties of Fourier transforms (e.g., scaling properties discussed in Press, W. H., et al., Numerical Recipes in Fortran, 2 nd Edition, Cambridge University Press, 1992, pg. 491), which states that for the transform pair h(t) <c> H(f): 1 h(at) <> --H(f /a) a Setting a = i/(l+X) proves the result. Note that what is actually done in "frequency shifting" is to stretch or compress the function in the time domain (i.e., h(t) -- h(at)) with amplitudes preserved. In the frequency domain this approach is equivalent to scaling the frequencies and amplitudes as indicated. NRC RAI EMCB.138/105 The minimum alternating stress ratio at current licensed thermal power (CLTP), according to CDI Report 07-05P is 2.0 for the Unit 1 steam dryer when the 218 Hz signals are removed from the pressure loads. Identify the top 10 frequencies that. contribute most to the minimum alternating stress ratio. TVA Response to EMCB.138/105 As discussed during the December 10, 2007, meeting with the NRC, TVA will provide accumulative power spectral density (PSD) graphs similar to Figure 20 of CDI Report No. 07-05P (provided in Enclosure 1 of our July 27, 2007 letter) for the ten steam dryer nodes exhibiting the lowest minimum alternating stress ratio. These graphs will be based upon the revised Unit 1 stress analysis being performed in response to RAI EMCB.140/107. The requested graphs will be submitted by March 6, 2008. NRC RAI EMCB.139/106 From the Units 1, 2 and 3 finite element analyses (( E2-16
NON-PROPRIETARY INFORMATION TVA Response to EMCB.139/106 As discussed in a meeting between TVA and NRC staff on January 25, 2008, PSD plots of stress as a function of frequency will be provided for five highly stressed locations on the Unit 2 dryer (( NRC RAI EMCB.140/107 Figures 1-4 of CDI Technical Memorandum No. 07-26P, Comparison of Browns Ferry Nuclear Unit 1 and Unit 2 Main Steam Line Strain Gage/Pressure Readings (proprietary version), show that Unit 1 MSL pressure spectral peaks are not bounded by Unit 2 peaks at all frequencies, particularly at low frequency peaks (examples: MSL A upper below 50 Hz; MSL A lower at selected frequencies below 80 Hz; MSL B upper, peaks below 50 Hz; MSL B lower, several peaks below 80 Hz; etc.). Provide the Unit 1 stress calculations that reflect dryer loads based on actual Unit 1 MSL measurements. TVA Response to EMCB.140/107 TVA will revise the Unit 1 steam dryer stress analysis utilizing the Unit 1 MSL strain gage data that was obtained during the unit restart from the extended outage during the last half of June 2007. As discussed with the NRC during our January 25, 2008 meeting, outstanding issues exist with the bias and uncertainty that should be applied in the steam dryer analyses currently under review with the NRC for EPUs. TVA is pursuing the closure of these issues with the NRC and will apply the appropriate changes prior to revising the stress analyses for the steam dryers. Assuming timely resolution of E2-17
NON-PROPRIETARY INFORMATION these issues, TVA believes that revision to the Unit 1 steam dryer stress analysis can be submitted by March 6, 2008. NRC RAI EMCB.141/108 Provide a more rigorous validation of the new frequency-based stress calculation approach presented in CDI Reports 07-05-P and 07-06-P. The validation should be based on (1) a prototypic steam dryer or substantial section of a steam dryer, and (2) prototypic acoustic loading of the dryer surfaces based on in-plant MSL measurements. A broad frequency range should be considered (at least a 50 percent increase in frequency, for example 100-150 Hz), along with the following: (1) One percent Rayleigh damping would be used for the transient simulations. Estimate the actual damping values at each natural frequency of the model and use them in performing new frequency based simulations. Stress and displacement time histories at high stress locations from both approaches would be compared il
)) Maximum stresses and displacements for both approaches would then be compared at several locations.
(2) Provide comparisons of Fast Fourier Transforms (FFTs) and explain any differences between peak levels. (3) Reevaluate the frequency simulations considered in (1) of this request for additional information (RAI) with 1 percent of the critical damping for all the frequencies and compare the results for high stresses, displacements and alternating stress ratios with those for the transient simulations presented in (1). Provide justification for the differences in the results. TVA Response to EMCB.141/108 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.110 by letters dated November 30, 2007 (ML073460793) and January 15, 2008. These responses by Hope Creek equally apply to the analyses performed for BFN. A comparison between the harmonic and time-domain methods is performed in Appendix B of both CDI Report No. 07-05P and Report No. 07-06P at two frequencies (15 Hz and 120 Hz). There, the applied load is the acoustic pressure field at the respective E2-18
NON-PROPRIETARY INFORMATION frequencies obtained by solving the Helmholtz equation in the steam dome. Therefore, the examples retained complexity in both the structural model (the full steam dryer was considered) and the spatial distribution of the applied load. However, the variation of the load in time was a simple sinusoid and one objective of the RAI is to establish agreement between the time-domain and harmonic approaches for a complicated time-varying loading. It is recognized that the underlying theory of the harmonic and time-domain approach is not in question, i.e., the mathematical soundness of the approach and theoretical agreement (at infinite spatial and temporal resolution, etc.) between the two approaches is accepted. Instead, the verification focuses on the implementation of the harmonic method and requests demonstration that the software embodiment of the harmonic method shows good agreement with time-domain solutions. The comparison shown in the two CDI reports noted above was undertaken on the Hope Creek steam dryer. Since the finite element model of the BFN steam dryers follows the same approach, with the same mesh spacing, element selection, etc., it follows that this comparison, and the ones discussed below, would be equally applicable to the BFN dryer model. The second objective is to evaluate the effect of using two different damping models, specifically a Rayleigh damping model and one that enforces 1% critical damping at all frequencies. Unless a complete modal decomposition is performed, the time domain method can only employ the Rayleigh damping model where 1% damping is enforced at two "pin" frequencies. Between these frequencies the damping is less than specified (and, therefore, overly conservative); elsewhere the damping is higher. The harmonic method can enforce 1% damping over the entire frequency range. The main challenge in comparing the time-domain and harmonic responses for a complete steam dryer over the typical 0-200 Hz frequency range is the time required to perform the time-domain calculation. The costs are discussed in Appendix B of both CDI Reports noted above and amount to multiple weeks of parallel computing time, terabytes of storage, and susceptibility to power interruption. These computational costs motivated a modified approach that retains complexity for the applied loading in both space and time. With this approach, the complete steam dryer is considered and subjected to an acoustic forcing function that is complex in both space and time, but limited to a frequency range of 100 Hz E2-19
NON-PROPRIETARY INFORMATION to 150 Hz. Limiting the frequency range reduces the computation time, which scales in proportion to fmax/fmin, where fmin and fmax are the smallest and highest frequencies considered in the calculation, respectively. In production steam dryer calculations fmin = 10 Hz and fmax = 200 Hz. Limiting the frequency range to fmin 100 Hz and fmax = 150 Hz reduces 1 computation time 13-fold, yet retains all of the complexities inherent in production runs. The one drawback with this option is that since the transient simulation is started from rest, lower frequency modes (i.e., less than 100 Hz) are also excited and their associated transients not fully damped by the end of the calculation. This behavior is evident, for example, in the 120 Hz simulation in Appendix B of CDI Report No. 07-05P and Report No. 07-06P, which shows the presence of a small transient for a mode whose characteristic frequency is less than 120 Hz. The following four calculations were set up and executed on the Hope Creek Unit 1 dryer model: (i) Harmonic calculation with 1% damping enforced at all frequencies; (ii) Harmonic calculation with a Rayleigh damping model with 1% damping enforced at the pin frequencies of 10 Hz and 150 Hz; (iii) Transient calculation starting from rest with the same Rayleigh damping model; and (iv) Transient calculation started with initial conditions obtained from the harmonic calculation with Rayleigh damping. This last calculation resulted after further consideration on how to reduce calculation times in the transient method, as discussed below. In all four calculations, the forcing is the same as used in the Hope Creek finite element analysis for CLTP conditions, but retaining only those frequency components in the range 100 Hz to 150 Hz. In the transient calculation, the acoustic pressure field at any time step is obtained by summing the Fourier components of the acoustic field over the 100-150 Hz frequency range. The Rayleigh damping model is the same as used in previous transient simulations for the Hope Creek steam dryer and also produces significant variation in the effective damping ratio over the frequency range considered here (0.72% at 100 Hz to 1% at 150 Hz). For the transient simulations the step size is chosen as 0.0002 seconds, which resolves the 150 Hz frequency component at 33.3 E2-20
NON-PROPRIETARY INFORMATION steps per cycle. This is higher than the 20 steps per cycle recommended by ANSYS. The simulation time interval was initially set to 1 second. (( E2-21
NON-PROPRIETARY INFORMATION Evaluations are made by comparing the time histories predicted by each calculation method. In all calculations, the stress component cxx is computed at every node in the tables (below) on one of the adjacent plates. The following measures of response amplitude and error are useful for quantitative comparison. Denoting the stress history obtained at a node using calculation, m, by uOm(t), then define: max Gmn maxl amn (t)I Cyalt = l(max{'m(t)}- min{Ym(t)}) max max - (nmax rm em.n max mx m ax (ýrTmn , C nm alt am alti _0 alt emn - alt alt/ max am~'Un E2-22
NON-PROPRIETARY INFORMATION Briefly, cmax is a measure of the maximum stress experienced during the response and 7alt measures the difference between the minimum and maximum stresses during the response and thus is max representative of an alternating stress. The error, e m,n, represents the difference in omax obtained by methods m and n, normalized by ama. ealtm,n represents a similar error measure for the alternating stress. The stress responses are compared at nodes selected on the Hope Creek steam dryer with the lowest stress factors. These nodes exhibited the strongest alternating stress intensities or maximum stress intensities at one of the frequency shifts. The excellent agreement demonstrated here between harmonic and transient solutions using the same damping models is expected to hold over other frequency ranges. In the following discussion, emphasis is placed on stress results. Generally matching stresses poses a more stringent test than comparing displacements, since stresses are derivative quantities and thus more strongly affected by discretization error. Furthermore, while stresses are of direct concern in steam dryer analysis, displacements are normally of lesser significance. Effects of Damping The influence of the damping model on the computed stresses is assessed by comparing the harmonic responses at selected nodes. Specifically, the calculations (i) and (ii) described above are compared. The Rayleigh damping varies from 0.72% to 1%, thus one expects that the stress peaks obtained with the Rayleigh model will be between 0% to 39% higher than when using a 1% damping at all frequencies. The stress and error measures defined above are recorded at the selected nodes in Table EMCB.141/108-1. The responses are compared in Figure EMCB.141/108-1. The main observation is that the predicted maximum and alternating stresses obtained with the Rayleigh damping model are everywhere higher than those obtained with 1% damping model. This is entirely consistent with expectations. The differences at these sample locations are up to 11%. Higher differences can be expected at other locations, particularly ones where the local response is dominated by a mode with natural frequency near 100 Hz. Another interesting observation is that even where stresses are very small (e.g., node 88325) the responses agree to within 9.3% error. Hence, as expected, the use of different damping models tends to scale the response rather than to introduce an additive error. E2-23
NON-PROPRIETARY INFORMATION Table EMCB.141/108-1: Maximum stresses and stress errors resulting from different damping models. Index 1 corresponds to 1% damping, and index 2 corresponds to Rayleigh damping. Node oyaxl(psi) anax2 (psi) al 1 (psi) alt 2 (psi) em-ax, 2 (%) ealt1, 2 (%) 82290 27.16 30.45 27.03 30.38 -10.8% -11% 86424 5.827 6.096 5.672 5.988 -4.4% -5.3% 82652 8.260 8.868 8.215 8.833 -6.9% -7% 88325 6.1x10- 4 6.72x10-4 5.93x10- 4 6.54X10- 4
-9.2% -9.3%
88252 23.32 23.46 23.1 23.19 -0.6% -0.4% E2-24
NON-PROPRIETARY INFORMATION Node 82290 40 30 20 10 a-
".5 2J 0
-10
-20
-30
-40 0 0.05 0.1 0.15 0.2 Time, sec Node 86424 8
6 4 a-ZCx 0
-2
-4
----I --- __]
-6 0 0.05 0.1 0.15 0.2 Time, sec Figure EMCB.141/108-1a: Comparison of harmonic solutions with Raleigh damping and flat 1% of critical damping. Dashed red line - Rayleigh damping. Solid blue line - 1% flat damping.
Nodes 82290 and 86424. E2-25
NON-PROPRIETARY INFORMATION Node 82652 10 5 a-Z, 0
-5
. ~-. . .. .. --
.. . ..--..- . . L -------
-10 0 0.05 0.1 0.15 0.2 Time, sec Node 88325 0.0008 .. . . . . . . . .. . T- "T 0.0006 0.0004 0.0002
.a CL 0
-0.0002
-0.0004
-0.0006
-0.0008 0 0.05 0.1 0.15 0.2 Time, sec Figure EMCB.141/108-lb: Comparison of harmonic solutions with Raleigh damping and flat 1% of critical damping. Dashed red line - Rayleigh damping. Solid blue line - 1% flat damping.
Nodes 82652 and 88325. E2-26
NON-PROPRIETARY INFORMATION Node 88252 30 -- -
. Raleigh damping 1%damping 20 -
10
-20
-30 - _ _ _ _ _ _
0 0.05 0.1 0.15 0.2 Time, sec Figure EMCB.141/108-1c: Comparison of harmonic solutions with Raleigh damping and flat 1% of critical damping. Dashed red line - Rayleigh damping. Solid blue line - 1% flat damping. Node 88252. Comparison of Harmonic and Time-Domain Predictions of Steady State Stresses The next comparison examines the responses obtained with the same damping model (Rayleigh damping), but using different prediction methods - the transient or time-marching approach and the harmonic analysis. In the transient analysis the initial conditions (displacements and velocities) are set from the harmonic analysis results in order to minimize the presence of transients in the response. Mathematically, identical responses are expected and the goal here is to verify whether this is reflected in the computational implementation. The results are tabulated in Table EMCB.141/108-2 and depicted in Figure EMCB.141/108-2. As expected, very good agreement is established overall. In all figures the agreement is demonstrated in both phase and amplitude and, with the exception of node 86424, the response curves are virtually indistinguishable. For node 86424 (Figure EMCB.141/108-2b), the maximum error occurs towards the end of the simulation. The difference in results for this node can be attributed to: (i) Temporal discretization errors - the transient time integration algorithm is second order accurate and thus has errors proportional to At 2 ; E2-27
NON-PROPRIETARY INFORMATION (ii) Frequency discretization errors - the frequency schedule is selected to ensure a worst case error of 5% in the response peak amplitude. This frequency schedule presumes 1% damping. Since the Rayleigh damping implies lower damping ratios in the current case (down to 0.72% damping), the worst case error is correspondingly higher (up to 5%/0.72 = 6.9%). The average error is considerably less. (iii) Initial condition errors - the initial conditions are also calculated to within the discretization accuracy afforded by the frequency domain calculation. Note too that the difference between the harmonic and transient responses for node 86424 varies periodically, peaking every seven cycles or so. This behavior is consistent with initial condition error or, possibly, excitation of a lower frequency mode in startup. For all other nodes, errors are less than 3%, which is within the maximum error bound (6.9%) given theoretically. Table EMCB.141/108-2: Comparison of harmonic and transient calculations. Index 2 corresponds to harmonic solution, and index 4 corresponds to transient calculation with adjusted initial conditions. Node oax2 (psi) eax 4 (psi) aalt 2 (psi) 0 alt 4 (psi) emax2, 4 (%) ealt 2 , 4 (%) 82290 30.45 29.58 30.38 29.58 2.9% 2.6% 86424 6.096 6.667 5.988 6.333 -8.5% -5.5% 82652 8.868 8.647 8.833 8.643 2.5% 2.2% 4 88325 6.72X10- 6.51xi0- 4 6.54X10-4 6.37x10- 4 3.1% 2.6% 88252 23.46 23.12 23.19 22.85 1.5% 1.5% E2-28
NON-PROPRIETARY INFORMATION Node 82290 40 ..... T Transient 30 Harmonic 20 10
- 4) 0
-10
-20
-30
-40 0 0.05 0.1 0.15 0.2 Time, sec Node 86424 8
6 4 0- 2 Z) CL 0
-2
-4
-6L..... I....
. L. _ __ ____ ! j 0 0.05 0.1 0.15 0.2 Time, sec Figure EMCB.141/108-2a: Comparison of harmonic and transient solution with adjusted initial conditions. Dashed red line -
transient; solid blue line - harmonic. Nodes 82290 and 86424. E2-29
NON-PROPRIETARY INFORMATION Node 82652 10 5 Zt 0
-5
-10 0 0.05 0.1 0.15 0.2 Time, sec Node 88325 0.0008 0.0006 0.0004 0.0002
.a CL 0
-0.0002
-0.0004
-0.0006
-0.0008 0 0.05 0.1 0.15 0.2 Time, sec Figure EMCB.141/108-2b: Comparison of harmonic and transient solution with adjusted initial conditions. Dashed red line -
transient, solid blue line - harmonic. Nodes 82652 and 88325. E2-30
NON-PROPRIETARY INFORMATION Node 88252 30 20 10 Z-CL 0 4o
-10
-20
-30 0 0.05 0.1 0.15 0.2 Time, sec Figure EMCB.141/108-2c: Comparison of harmonic and transient solution with adjusted initial conditions. Dashed red line -
transient; solid blue line - harmonic. Node 88252. (( E2-31
NON-PROPRIETARY INFORMATION E2-32
NON-PROPRIETARY INFORMATION Figure EMCB.141/108-3a: Comparison of transient calculations with zero initial conditions (IC) and initial conditions calculated from harmonic solution. Solid blue line - zero IC; dashed red line - adjusted (or non-zero) IC. Nodes 82290 and 86424. E2-33
NON-PROPRIETARY INFORMATION E[ 1] Figure EMCB.141/108-3b: Comparison of transient calculations with zero initial conditions (IC) and initial conditions calculated from harmonic solution. Solid blue line - zero IC; dashed red line - adjusted (or non-zero) IC. Nodes 82652 and 88325. E2-34
NON-PROPRIETARY INFORMATION (( Figure EMCB.141/108-3c: Comparison of transient calculations with zero initial conditions (IC) and initial conditions calculated from harmonic solution. Solid blue line - zero IC; dashed red line - adjusted (or non-zero) IC. Node 88252. PSD comparison The PSD of stress component o,, is calculated for two of the nodes, 82290 and 88252. Since the estimate was calculated from 0.2 sec time histories, the frequency resolution is only 5 Hz. The comparison in the frequency range from 100 Hz to 150 Hz is shown in Figure EMCB.141/108-4 for node 82290 and in Figure EMCB.141/108-5 for node 88252. The effect of damping (Figures EMCB.141/108-4a and EMCB.141/108-5a) is similar to that observed above in the stress time histories, i.e., the PSD corresponding to the Rayleigh damping model is generally larger, since the effective damping in this frequency range is smaller. From Figure EMCB.141/108-4a, the effect is seen to be frequency dependent. When using the same damping models, the PSDs extracted from the harmonic and time-marching calculations (the latter being started with transient-free initial conditions) are in excellent agreement (Figures EMCB.141/108-4b and EMCB.141/108-5b) . The small F2-35
NON-PROPRIETARY INFORMATION mismatches (recall that these results are plotted on logarithmic scales) near 100 Hz and 150 Hz are due, in part, to leakage into neighboring bins when computing the PSD. Finally, the PSDs obtained from the transient simulations initiated with the transient-free solutions and with zero initial conditions are compared in Figures EMCB.141/108-4c and EMCB.141/108-5c. These plots indicate that the presence of start up transients over this time interval can result in both under- and over-predictions of stresses. E2-36
NON-PROPRIETARY INFORMATION Node 82290 102 Raleigh damping c T 7 *
- r Id 1 Ij 101 S I I \ ii §i I,-
I anrii
, _ _ L- - _-- - \ -_ - - -
L 4:- -/- N
~~~~- . - - - -*/. - - --- - ---
( 100 - -- -- - - -
-==T7--
7----- ---- ----- --- -- - ----- -- CL (0 -1 10 U) 77 .I
-- I T- L 1____- -------
- -T-- - - _ - -
I I I I I I l~
"2 10 A _I F F A _I U -
A' =* F L U 41 4 _I. L
-t31 100 105 110 115 120 125 130 135 140 145 150 Frequency, Hz Figure EMCB.141/108-4a: PSD comparison of the harmonic solutions obtained with Rayleigh damping and constant 1% critical damping.
Dashed red line - Rayleigh damping. Solid blue line - 1% flat damping. Node 82290. Node 82290 102 Transient F T- - - - - - - - Harmonic - - - ---- - - 101 iE~~ ~~ 7! E=- _-- - --- -E-I - --- _-- -]- -,=- E I-
-__E---
-I 10
- -i-.. - - - .- .
n - .- --.-- - - - - - -- - - (L --
- ZZZEZ
-I- - - -~ -
- - Z-Z
- I
- - - i.
- -.---Z ZZ
.1. .- --
SZ - Z -- Zr ---IT 4-44-Zr-- --- . .i. . 2.f L Z VI Z
---- - Z--
10 i 1 F i A i I I------ 10.2
-- - - -h- --- - +-- - - I - - .I - -F-- F 4U-3 100 105 110 115 120 125 130 135 140 145 150 Frequency, Hz Figure EMCB.141/108-4b: Comparison of harmonic and transient solution with adjusted initial conditions. Dashed red line -
transient, solid blue line - harmonic. Node 82290. E2-37
NON-PROPRIETARY INFORMATION Node 82290 102
=
- - Non-zeroi- --- r--- ----- .-----------------
Zero No - IC -- - - r - -T Zer IC 101 1 Z 1 -_ - I 74:- - - - - - - - -
----------- -- -- -- - --. . - - -- -- . - -- I-
-I - -- - -
-I--- I
(_ 100 00 ....- 1--- -......---- I - - - - I3 C: - - I 10
- 10) T - - -I - - - - -
T L I - - - 10-2
,- _ - I- - - - - 4----- -- ----i-- - - -- - -- -
4 rt-3 100 105 110 115 120 125 130 135 140 145 150 Frequency, Hz Figure EMCB.141/108-4c: Comparison of transient calculations with zero initial conditions (IC) and initial conditions calculated from harmonic solution. Solid blue line - zero IC; dashed red line - adjusted (or non-zero) IC. Node 82290. E2-38
NON-PROPRIETARY INFORMATION 102 1 1 Node 88252 1 _ Raleigh damping _ C --- -. 1%damping . ...----- - zo z "i ý1 10 .. . . . . ..- -- -- - -- --- r 10I "i TN I - ~ i
. . - I- - ,
-'-- - 4-, - - --- - -
i - - - 2 r 1 10 10515- 1u0 1 I) -t- -T2 - - - 13- 140 - - 145- 150 S I - i .... , *:f ... requency, Hz 7 I 1I I F - I I I I Figure: EMCB141/082=: PS comarso :=: :::I: of th harmonic 100 110 115 120 125 130 135 140 145 150 line - Frequency, Hz blue - 1% fla daming Nod 88252I. Figure EMCB.141/10B-5a: PSD comparison of the harmonic solutions obtained with Rayleigh damping and constant 1% of critical damping. - - Dashed red line - Rayleigh damping. lar o i F--- - - -I --- - r- - 7 - Solid blue 10 "- -line- -- - 1% flat -damping.
-- I - -, Node 88252.
102 2 Node 85252 10 z Transient ----- - - -
---Harmonic I, L- - - -__
iI l I 1 I1 r TI . .
--------- 4----- 4 --- IZ
~
I----Z ZZ*:- 7....: i =: A- -_-- / :*
- - - - - - - - - - - 1 100 'L = -- -------
-- -- 17------I---- -- -- ---- T..I. .. I. . I I ~*~~ I I\I I I I II
- I' - -T 100 105 110 115 120 125 130 135 140 145 150 Frequency, Hz Figure EMCB.141/108-5b: Comparison of harmonic and transient solution with adjusted initial conditions. Dashed red line -
transient, solid blue line - harmonic. Node 88252. E2-39
NON-PROPRIETARY INFORMATION Node 88252 102 Non-zero IC Zero tC 101
. . - - . -I ZE : T 10o - .I F.. - - -
- 8. -
.. - .T - .. .- F-
- Ir ---
--- i T--- -- I -
10-0
- ---:ZZZ 3ZZ -I-- - .IF.. - - -T i I
_ F T -- I 10-21 10 0 105 110 115 120 125 130 135 140 145 150 Frequency, Hz Figure EMCB.141/108-5c: Comparison of transient calculations with zero initial conditions (IC) and initial conditions calculated from harmonic solution. Solid blue line - zero IC; dashed red line - adjusted (or non-zero) IC. Node 88252. Summar~y The comparisons carried out here have shown that: (i) Excellent agreement is achieved when comparing the harmonic and transient responses obtained for identical steam dryer models and damping models. This agreement is demonstrated for a load that is complex in both space and time and is established for both amplitude and phase. Remaining discrepancies can be attributed to discretization error in the time integration scheme and/or frequency schedule discretization. (ii) The effects of damping (Rayleigh vs. constant 1% damping) upon the periodic response behave as expected. In this case the Rayleigh damping model results in overpredictions of the stress response due to lower effective damping. E2-40
NON-PROPRIETARY INFORMATION The non-conservative (( )) frequency discretization error discussed above is added to the overall bias of the model over the entire frequency range. This error accounts for the use of a discrete frequency schedule. This error was not accounted for in the mesh convergence study (which accounted for spatial discretization errors associated with finite mesh spacing) nor the shaker test comparison (which assessed the error due to both finite mesh size and other modeling assumptions). (( E2-41
NON-PROPRIETARY INFORMATION F.2-42
NON-PROPRIETARY INFORMATION
)) the average bias due to the discrete frequency sampling used in the harmonic analysis is (( )) The average bias of
(( )) will be added to the hydrodynamic loads on the dryer prior to the stress analysis. NRC RAI EMCB.142/109 Appendix A of CDI Reports 07-05-P and 07-06-P, there is a description of the numerical experiments carried out using the ANSYS code applied to simple analytically tractable structures with dimensions and mesh spacing similar to the ones used for the steam dryer, ((
)) As establishing convergence of resonance frequencies is not sufficient to establish convergence of strain and stress fields and, frequency shifting loading functions does not account for lack of convergence in strain and stress fields, additionally information is needed.
Provide the mesh convergence studies in high strain and stress regions in the steam dryer to assess whether the dimensions and mesh spacing used for the model are adequate. In particular, plots of stresses near high stress regions for coarse and dense finite element meshes could be used to confirm that the dryer model used to establish that the limit curves are converged. TVA Response to EMCB.142/109 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by E2-43
NON-PROPRIETARY INFORMATION Hope Creek in responses to Hope Creek RAI 14.79 by letters dated November 30, 2007 (ML073460793) and January 25, 2008. These responses by Hope Creek equally apply to the analyses performed for BFN. Mesh refinement tests were conducted on a structure excised from the Hope Creek Unit 1 steam dryer comprising the middle hood with two hood supports, side plate, cover plates and closure plate as shown in Figure EMCB.142/109-1. Since the finite element model of the BFN steam dryers follows the same approach as the Hope Creek dryer, with the same mesh spacing, element selection, etc., it follows that the mesh refinement test discussed below would be equally applicable to the BFN dryer model. All dimensions and structural properties were kept the same as in the full model. Structural damping was prescribed at 1% of critical at all frequencies. Cantilevered supports were introduced at the edges typically coupled to heavier parts of the steam dryer such as the upper support ring and vane bank. E2-44
NON-PROPRIETARY INFORMATION 30.00 Figure EMCB.142/109-1: Substructure of a steam dryer used for mesh convergence tests. Blue lines indicate cantilevered support, red lines denote free edges, and black lines show connections between parts. The elements used in the analysis are of the same type as those used in the steam dryer calculations, namely SHELL63 in ANSYS notation. This quadrilateral shell element utilizes Discrete Kirchoff Triangles (DKT) technology, providing cubic interpolation order in the displacement component normal to the shell surface along the edges, and, therefore, quadratic stress variation. Note that contour plots produced by ANSYS are linear over the elements and, thus, are only approximately representative of the stress and displacement variation supported by this element. The structure in Figure EMCB.142/109-1 was subjected to loadings characteristic of those present in the actual analysis of the Hope Creek Unit 1 steam dryer. Specifically, the structure was loaded by its own weight for the static component and subjected to the same harmonic pressure distributions applied to the full dryer. Displacements and stresses were computed in the same way as in the full steam dryer stress evaluation. E2-45
NON-PROPRIETARY INFORMATION To investigate the mesh dependence of stresses and displacements, three different grids were considered. The coarsest mesh, labeled Mesh xl, is representative of the mesh sizing used in the full steam dryer calculation (see top figure of Figure EMCB.142/109-2a) and contains 4329 nodes and 4208 elements. A finer mesh, denoted by Mesh x2 and containing 11914 nodes and 11726 elements, is obtained by uniformly refining the coarser mesh, resulting in elements that are approximately half the size of Mesh xl. The finest mesh, labeled Mesh x4, contains 54324 nodes and 53912 elements that are approximately four times smaller than in the original Mesh xl. All three grids are shown in Figure EMCB.142/109-2. E2-46
NON-PROPRIETARY INFORMATION 0.00 50.00 (in) 25.00 Figure EMCB.142/109-2a: Mesh used in full steam dryer analysis (top figure) and the coarsest mesh, Mesh xl, used in the convergence tests (bottom figure). E2-47
NON-PROPRIETARY INFORMATION dM F.ir 6E.0o (Re
)
30.00 Figure EMCB.142/109-2b: Refined mesh, denoted Mesh x2. 7 0.00 50.00 n) 25.00 Figure EMCB.142/109-2c: Further refined mesh, denoted Mesh x4. E2-48
NON-PROPRIETARY INFORMATION Convergence in Static Analysis The deformations due to gravity were calculated on the three meshes described above. In addition, deflections and stresses were also calculated on grids refined locally using the adaptive meshing capability provided by the ANSYS Simulation module. This adaptive refinement is performed automatically by ANSYS in locations where higher discretization error is detected. This additional refinement was performed on each mesh except Mesh x4, where further adaptive refinement was not needed because the element size was already very small. The typical convergence behavior for the maximum stress intensity during adaptive mesh refinement is shown in Figure EMCB.142/109-3, where the horizontal scale ("Iteration Number") is the number of adaptive mesh refinement steps. The results of adaptive refinement for all three initial grids are summarized in Table EMCB.142/109-1. The calculated stresses did not change appreciably during adaptive local mesh refinement. Overall, the range of computed stress intensity values is within 4% of stress intensity values computed on Mesh xl. The deflected shapes and stress intensity distributions are shown in Figure EMCB.142/109-4. These results show that the static solution is indeed satisfactorily converged on the grid Mesh xl. Adaptive mesh refinement, Mesh xl
.¢ 164.6 ci) 164.4 164.2 164 I I I _ _____
0 2 4 6 8 10 Iteration No. Figure EMCB.142/109-3: Evolution of stress intensity with adaptive convergence on Mesh xl. E2-49
NON-PROPRIETARY INFORMATION Table EMCB.142/109-1: Static solution. Maximum Maximum stress Maximum stress intensity Mesh displacement, in intensity, psi after adaptive refinement, psi Mesh xl 1.58X10- 3 164.10 164.96 Mesh x2 1.58X10- 3 169.37 166.17 Mesh x4 1.58X10-3 169.37 no adaptation performed E2-50
NON-PROPRIETARY INFORMATION low Uefao,.ý tress IrVtkaty rp M 10 I 579"-o03 2OD711114 09:40 2007/11J14 0:41 5~8 i 64 ý.- 0IM o.13 73.1,'* S..' 36.m MW29 aOM 10*58 am 600610)~ 0000580 3000 TotalD 406 K.: I 6628.ý MI. 0.100+00 (086-561 Z57 t164 146? 247.736 0.121 1110.74 z W,44* 74,012 371,,5 18A1
*,0 z
1n1OI 0OO 6000oh) I00 5558s Ir014.0y 0 1.5842-pit: 2.0508O 10
.0 .141
.071111;2 l0:31 169.372 012.1 31M 0.106 112.9W3 94 187 0070 S6U94 I7.7O D0583
.030 0 D35 Uol 0258 000 Figure EMCB.142/109-4: Comparison of static deflections (left side) and stress intensities (right side) for the grids Mesh xl (top row), Mesh x2 (middle row), and Mesh x4 (bottom row).
E2-51
NON-PROPRIETARY INFORMATION Note on "Hot-Spots" In the stress convergence results, several locations are excluded from the maximum stress evaluation. These locations were identified during adaptive mesh refinement as having non-convergent stress. The typical stress intensity behavior during mesh refinement at these "hot spots" is shown in Figure EMCB.142/109-5. In Figure EMCB.142/109-6 a typical stress singularity is shown at the re-entrant corner, created by connection of the top of the closure plate to the hood. Note that several plate thicknesses from the junction, the calculated stresses are low and consistent with overall stress distribution. Such "hot spots" can occur at structural discontinuities, such as re-entrant corners, where the stress becomes infinite as the mesh is refined. For example, a re-entrant corner in a continuum element will generally develop infinite stresses. Likewise, the membrane (in-plane) stresses in a shell or plate will become infinite at re-entrant cutouts or cantilever roots when in-plane loads are applied (bending stresses in shells generally converge). Stress intensity at the "hot spot" 700 S500 400 200 i 0 2 4 6 8 10 Iteration number Figure EMCB.142/109-5: Evolution of stress intensity with adaptive convergence at "hot spot" on Mesh xl. E2-52
NON-PROPRIETARY INFORMANT ION StressIntensity psi Max: 6,883e+002 Min:4.406e+000 2007111/14 08:42 688338 612.346 536,353 460.361 384.368 308.376 232,.383 156.,91 80.39a 0 wo 3.00 n)1Z, Figure EMCB.142/109-6: Stress singularity at hood / closure plate junction. These singular behaviors are mathematically correct and consistent with analytical results. For example, the classic Williams series solution (Williams, M. L., "Stress singularities resulting from various boundary conditions in angular corners of plates in extension,"J. Appl. Mech., 74, pg. 526-528, 1952) for the 2D stress field at a corner with notch angle 2y, where y = 0 for a crack, shows that the stress behaves as O(r'_-), where X is obtained from the transcendental equation A sin(2a) + sin(2Ay) =
- 0. Since X < 1 for A > n/2, the stress field for a re-entrant notch is locally singular. The study of these singularities is well developed in crack propagation theory with applications to fatigue. The main point to note is that simply refining the mesh of a complex structure will reveal that stresses do not (and should not) converge at junctions and corners, but will continue to grow without bound. These "hot spots" are usually very localized, and stresses away from these spots converge to finite limiting values. Even so, resorting to substructuring techniques or adaptive gridding will not necessarily produce global convergence.
This behavior is well known in the structural elasticity community and is addressed in alternate ways. One option is to smooth corners and apply finite fillet radii at various locations. The drawbacks of this approach are that in real E2-53
NON-PROPRIETARY INFORMA~TION life, weld and junction geometries are usually neither known to this level of accuracy nor abide by such smooth radii idealizations (e.g., real welds are uneven and exhibit variability) . Another drawback is the huge number of elements required to model every junction and corner at mesh resolutions sufficient for converged stresses. Another option is to extrapolate stresses to junctions from points away from the junction. Popular choices for shell elements are to evaluate the stress at distances t and 2t away from the junction, where t is the thickness, and extrapolate these stresses to the junction. By fixing the extrapolation points and refining element size, convergence eventually sets in. Again, this approach is only feasible when the structure is relatively simple, so that high resolution can be achieved with manageable element counts. In the present model it is not possible to use elements with spacing on the order of the thickness, since this would produce an enormous number (10 million or more) of finite elements. Moreover, linear extrapolation through two locations is itself an approximation which adds to other approximations such as neglecting 3D effects (which dominate at junctions) and weld variability. In our approach a conservative and computationally practical approximation described in the ASME code is adopted, where the stresses at welded junctions are estimated using weld factors. These factors account for stress concentration as well as weld variability and are determined from collated experience in the design and operation of welded structures. Accordingly, the peak stresses at junctions and other discontinuities are estimated by evaluating the stresses away from the discontinuities (i.e., the nominal stresses, which will be accurately converged) and multiplying them by the weld factor. In our implementations, a more conservative approach is adopted where the "~nominal stresses" are taken as the FEA stresses~at the discontinuities rather than a small distance away. Since these junction stresses will generally be somewhat higher (and become infinite with finer mesh size) than those away from the junction, this approach will predict correspondingly higher peak stresses and, therefore, confer added conservatism. Convergence in Harmonic Analysis The full steam dryer stress analysis proceeds by calculating the harmonic structural response at a number of frequencies. The combination of these harmonics and comparison of these assembled solutions with transient simulations is addressed in RAT EMCB.141/108. Here the accuracy of the harmonic stress solutions is estimated. To this end, the grids Mesh x1, Mesh E,2-54
NON-PROPRIETARY INFORMATION x2, and Mesh x4, described above, were again used. The structure was subjected to the same harmonic pressure fields used in the full steam dryer analysis. Specifically, the pressure loading resulting from a unit mnonopole pressure at the MSL A inlet was applied to the structure. Here the harmonic stresses are examined at the following frequencies: 53.863 Hz, 101.4 Hz, and 199.61 Hz. These values were selected from the discrete frequency schedule used in the full steam dryer analysis and chosen to represent the low, medium, and high ends of the frequency range. The real parts of the associated pressure fields are shown in Figure EMCB.142/109-7. Note that both real and imaginary parts of pressure are applied to the structure. Consequently, the calculated stresses and displacements also contain both real and imaginary parts. The vibration amplitudes are given in the usual manner by taking the absolute value of the complex quantities. The stress intensity is computed here by computing the stress intensity, Sr, of the real component of the stress tensor, and the stress intensity, Si, for the imaginary component. The reported stress intensity 2 for the node is then given by S-S r+ S 2 i. Note, further, that the "hot spots" identified in the static convergence study are removed from stress evaluation. For each calculation the nodes having the largest real (Location
- 1) or imaginary (Location 2) parts in the response were considered. The amplitudes of total displacement and stress intensity were computed and compared on the different grids.
The locations of the maximum displacement and stress intensity were the same on all grids, as can be seen from comparison of real and imaginary stress distributions in Figure EMCB.142/109-8. These plots show that the stress intensity distributions are qualitatively similar on all meshes, and that maximum stresses and displacements occur at the same locations. F2-55
NON-PROPRIETARY INFORMATION NODES AN
-.0O{5olI 0 -.
-. omI*.I 8
.002821 .M-
.06¢752 .=68~3 AN
.054621 -. 021135 .0 M523 09 .045839 .01932 N
-037747 -. 004741 .020005 0o12502 .0g1o10 180080 AN 1
-. o"070 -. 089198 009320 .050000 .15010' Figure EMCB.142/109-7: Pressure distribution, real part, at 53.863 Hz (top), 101.4 Hz (middle), and 199.61 Hz (bottom).
E2-56
NON-PROPRIETARY INFORMATION AN AN
=3SOXe 1ý.046310 3C0 -so 6000 7500 900: 10501 1200i "531 1, 97 2947 5813 .. 3. 11784 W172 1'76'5 20621 21566 26512 AN AN 231428 1454 2907 4361 530 76 8 721 1 362 6 2967 8898 7268 10175 13082 118'3 14829 177g qS 2.-6 1126 2-1g AN AN
.773 2-3 5671 8506 -132 .838406 -92 "1903 11855 30 14B 42S3 I06 9924 1] 2976 .1. 14"9 03 Figure EMCB.142/109-8a: Comparison of the real (left side) and imaginary (right side) components of the stress intensity distribution at 53.863 Hz on Mesh xl (top), Mesh x2 (middle),
and Mesh x4 (bottom). E2-57
NON-PROPRIETARY INFORMATION AN AN
-2. U53230333.713 - 373 _1 -1 -. -2 2336 216, -3 AN MN oz4:
- .ýxw%
...... I.. ! i I*.. .... ... .... I -1 2 ý .ý -ý 3-H*1.71]* 1O 2i26 203S 1772 2481 l8 2-AN AN 378547 3-972 679.371 1359 2038 2711 30S59 774.987 1550 2325 3100 5 1019 6168 ý-7 3057 2e,*
162 11 113 2-1 - -7 Figure EMCB.142/109-8b: Comparison of the real (left side) and imaginary (right side) components of the stress intensity distribution at 101.4 Hz on Mesh xl (top), Mesh x2 (middle), and Mesh x4 (bottom). E2-58
NON-PROPRIETARY INFORMATION AN AN
-t.m= =
su -- I .....
" 0339402 2076 193920. 4"*361. 129 481. 492601.855 7*22.218842. 581 962. 9.4 Io.. M02 2510
.091595 313,*9_ 627. S06 -. 2141255 -15 211o 2 AN I"~
- Tu T", -11 271.064 IC86343 542.072 010 04 304.4 1100 121 11 0 3 2 510.51 406.500 617.516 194.5R. IM1 AN AN 10Dw-o-
.054720 284.353 5-631s 85's~
94'
- 1-*
302-*1 906,03, 15ý0 2114 271o Figure EMCB.142/109-8c: Comparison of the real (left side) and imaginary (right side) components of the stress intensity distribution at 199.61 Hz on Mesh xl (top), Mesh x2 (middle), and Mesh x4 (bottom). E2-59
NON-PROPRIETARY INFORMATION In Tables EMCB.142/109-2 and EMCB.142/109-3 below, quantitative comparisons of the maximum displacement and stress intensity amplitudes on the three meshes are given. Location 1 corresponds to where the real part of the corresponding solution is a maximum; Location 2 corresponds to maximum imaginary part. These tables show that the displacements and stresses are computed to within 10% uncertainty in the wide range of frequencies, except one location, namely Location 2 at 101.4 Hz where the variation in stress intensity is 15.8%. Table EMCB.142/109-2: Total displacement amplitudes of the harmonic solution on different resolution meshes. Mesh x1 Mesh x2 Mesh x4 Variation Frequency 53.863 Hz Location 1 0.5265 0.5188 0.5391 3.9% Location 2 0.6053 0.6095 0.6149 1.6% Frequency 101.4 Hz Location 1 0.0306 0.0304 0.0305 <1% Location 2 0.0241 0.0241 0.025 3.7% Frequency 199.61 Hz Location 1 0.00693 0.00688 0.00632 9.7% Location 2 0.00907 0.00896 0.00874 3.8% Table EMCB.142/109-3: Total stress intensity amplitudes of the harmonic solution on different resolution meshes. Mesh xl Mesh x2 Mesh x4 Variation Frequency 53.863 Hz Location 1 24328* 23480* 23741* 3.6% Location 2 28224* 28324* 28490* <1% Frequency 101.4 Hz Location 1 3272 3296 3255 1.3% Location 2 3017 3283 3493 15.8% Frequency 199.61 Hz Location 1 1826 1813 1728 5.7% Location 2 2880 2865 2851 1%
- Note that the large stress intensities reported in the table correspond to the pressure field resulting from a unit (1 psi)
E2-60
NON-PROPRIETARY INFORMATION pressure fluctuation at the inlet of MSL A. In actual operation, the pressure fluctuations are much smaller; here at 53.863 Hz the pressure magnitude is only 3x10-5 psi. Hence actual stresses will be correspondingly smaller also. To investigate the reason for the discrepancy at Location 2 at 101.4 Hz, additional calculations were undertaken over the 100 - 102 Hz frequency range in 0.25 Hz increments, and the amplitude at Location 2 was computed. The results are summarized in Figure EMCB.142/109-9 and show that at 101.4 Hz the frequency response is changing rapidly and that the 15.8% variation can be attributed to the slight shift in the frequency response on different meshes. Thus, rather than comparing the stress intensities at a fixed frequency, it is more useful to compare the maximum stress intensity amplitudes on each mesh. This comprises a more relevant comparison, since these maxima in the stress intensity frequency responses correspond directly to the values tabulated in the full steam dryer stress reports (and, consequently, also the stress ratios). From Figure EMCB.142/109-9, the peak response on all meshes occurs at 100.75 Hz. The associated peak stress amplitudes are plotted versus mesh size in Figure EMCB.142/109-10. The actual values are 3510.4 psi on Mesh xl, 3688.5 psi on Mesh x2, and 3790.8 psi on Mesh x4. In Figure EMCB.142/109-10 the mesh size is normalized by the average element size of Mesh xl; hence the normalized mesh sizes of Mesh xl, Mesh x2, and. Mesh x3 are 1.0, 0.5, and 0.25, respectively. It may be seen that computed peak stresses adhere closely to a linear dependence on mesh size. Therefore, one can fit the available values and reliably extrapolate to estimate the stress peak at infinite mesh resolution (i.e., mesh size = 0). From the equation of the linear fit, shown on Figure EMCB.142/109-10, the best estimate of stress intensity at the peak is 3880 psi. This implies that the error in the coarsest Mesh xl peak stress prediction (of 3510.4 psi) is (3510.4 - 3880.0)/3880.0 = 9.53%. Note that for the two other frequencies, 53.863 Hz and 199.61 Hz, the computed stresses show considerably less variation because the excitation is away from resonant peaks, so that the frequency response curves do not exhibit steep slopes about these frequencies. In conclusion, a grid with element size typical of Mesh xl, which is representative of that used in the full steam dryer evaluation, incurs errors in the peak stresses that are less than 10%. E2-61
NON-PROPRIETARY INFORMATION Frequency sweep 3800 I - -- 3600-Di h 3400 - CL Co 3200 3000 0 Mesh xl 2800 - B- Mesh x2 Mesh x4 2600 i I 99.5 100 100.5 101 101.5 102 102.5 Frequency, Hz Figure EMCB.142/109-9: Stress intensity amplitude vs. frequency for Location 2 in the 100 - 102 Hz frequency range. E2-62
NON-PROPRIETARY INFORMATION Stress intensity vs. mesh size 4000 3800 - -r
- 0. 3600 CO 2 3400 30 3200 - Linear curvefd y =3879.9- 371.34x R=:0.99938 3000 -
0 0.2 0.4 0.6 0.8 1 1.2 Mesh size Figure EMCB.142/109-10: Extrapolation of the peak stress intensity amplitudes as a function of mesh size. The peak stress amplitudes occur at 100.75 Hz in Figure EMCB.142/109-9. The mesh size is normalized by the mesh spacing on Mesh xl. E2-63
NON-PROPRIETARY INFORMATION E[
] Note that both e0 and efe were calculated on grids with mesh resolution comparable to that used in operational steam dryer analysis.
It was subsequently pointed out that peak finite element stresses do not converge at the same rate as displacements. In a finite element calculation, the displacements generally converge at a different rate than stresses since the latter is essentially a spatial derivative of the former. (( E2-64
NON-PROPRIETARY INFORMATION F2- 65
NON-PROPRIETARY INFORMATION Figure EMCB.142/109-11: Displacement amplitude vs. frequency for location 2 in the 100-102 Hz frequency range. As was also observed in the corresponding stress amplitude the displacement exhibits a peak about frequency 100.75 Hz. The associated peak values are plotted versus normalized mesh size squared in Figure EMCB.142/109-12. ((
))
E2-66
NON-PROPRIETARY INFORMATION With this result in hand, one can conclude that the total error in the stress prediction due to both finite element modeling approximations and finite mesh size is:
))
Figure EMCB.142/109-12: Extrapolation of the peak displacement amplitudes as a function of mesh size. The peak displacement amplitudes occur about 100.75 Hz in Figure EMCB.142/109-11. The mesh size is normalized by the mesh spacing on Mesh xl. E2-67
NON-PROPRIETARY INFORMATION NRC RAI EMCB.143/11O Shifting the frequency of the steam dryer loading will account for uncertainty and bias in the finite element (FE) model resonance frequencies. However, it does not account for errors in the mean and peak frequency response amplitudes due to uncertainty or bias in plate dimensions, boundary conditions (joints between plates and other members), pre-stresses within members, and friction between internal vanes and other components. Provide the uncertainty and bias in the dryer FE model frequency response function (FRF) amplitudes (not in the modal frequencies, the uncertainties of which are already handled by frequency shifting the loads). Any FRF measurements on prototypic dryers which may be available should be included for this bias and uncertainty assessment. TVA Response to EMCB.143/110 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.79 2nd follow-up by letter dated January 15, 2008. This response by Hope Creek equally applies to the analyses performed for BFN. The stress convergence study performed on a section of the Hope Creek steam dryer model (discussed in RAI EMCB.142/109) showed that the stresses calculated on a mesh representative (in terms of mesh spacing) of the one used in the finite element analysis (FEA) of the Hope Creek Unit 1 dryer were accurate to within (( )) This error was obtained by comparing the computed stress against the value one would obtain on a hypothetical mesh having zero mesh spacing (i.e., infinite resolution). This infinite-resolution stress was inferred by calculating the stress on successively finer meshes and then extrapolating the resulting stress vs. mesh spacing curve to zero mesh spacing. PSEG also conducted a shaker test of the spare Hope Creek Unit 2 dryer (CDI Report No. 07-27P, "Finite Element Modeling Bias and Uncertainty Estimates Derived From the Hope Creek Unit 2 Dryer Shaker Test," Rev. 0, December 2007 submitted by Hope Creek letter dated December 31, 2007 (ML080080579)) where the response at up to 20 accelerometer locations was measured for eight different shaker locations and between 30 to 50 different forcing frequencies in the range 10 to 200 Hz. These measurements were compared against finite element predictions obtained using the ANSYS code and a finite element mesh whose E2-68
NON-PROPRIETARY INFORMATION grid size is similar to the one used in the stress analysis of the operational Hope Creek Unit 1 dryer. This comparison resulted in an error, (( 1] expressed as the sum: et = (absolute value of bias) + uncertainty 1] NRC RAIs EMCB.145/112 through EMCB.147/114 The following are associated with CDI Report No. 07-06-P, Finite Element Model for Stress Assessment of Browns Ferry Nuclear Unit 2 and 3 Steam Dryers to 250 Hz, which is Enclosure 2 of a letter dated July 31, 2007. NRC RAI EMCB.145/112 The effect of damping due to flow (( To TVA Response to EMCB.145/II2 As discussed in the meeting between TVA and NRC staff on January 25, 2008, PSD plots of stress as a function of frequency will be provided for five highly stressed locations on the Unit 2 dryer (( E2-69
NON-PROPRIETARY INFORMATION NRC RAI EMCB.146/113 The minimum alternating stress ratio at CLTP, according to CDI Report 07-06P is 1.77 for the Unit 2 steam dryer when the 218 Hz signals are removed from the pressure loads. Identify the top ten frequencies that contribute most to the minimum alternating stress ratio. TVA Response to EMCB.146/113 As discussed during the December 10, 2007, meeting with the NRC, TVA will provide accumulative PSD graphs similar to Figure 20 of CDI Report No. 07-05P (provided in Enclosure 1 of our July 27, 2007 letter) for the ten steam dryer nodes exhibiting the lowest minimum alternating stress ratio. These graphs will be based upon the revised Unit 2 stress analysis being performed in response to RAI EMCB.140/107. The requested graphs will be submitted by March 31, 2008. NRC RAI EMCB.147/114 As discussed in the CDI Reports 07-05-P and 07-06-P, Units 2 and 3 are subjected to the same acoustic pressure loading as Unit 1, but their minimum alternating stress ratio at CLTP is smaller than the cdrresponding ratio for Unit 1. Address whether this difference in the minimum alternating stress ratios is due to difference in the structural modifications only or due to any other reasons. TVA Response to EMCB.147/114 The difference in the minimum alternating stress ratios is due to differences in the structural modifications in the steam dryers. The differences in the steam dryers are further clarified in the response to EMCB.133/100. As discussed in the responses to EMCB.130/97 and EMCB.140/107, the Units 1 and.3 stress analyses will be revised to utilize unit-specific MSL strain gage data. NRC RAIs EMCB.148/115 through EMCB.153/120 The following RAIs are associated with CDI Report 07-09-P, Methodology to Predict Full Scale Steam Dryer Loads from E2-70
NON-PROPRIETARY INFORMATION In-Plant Measurements, With the Inclusion of a Low Frequency Hydrodynamic Contribution (Rev. 1), which is Enclosure 3 of a letter dated July 31, 2007. NRC RAI EMCB.148/115 In CDI Report No. 07-09-P, ((
)) Explain why such large differences exist in the source strengths.
TVA Response to EMCB.148/115 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.111 by letter dated November 30, 2007 (ML073460793). This response by Hope Creek equally applies to the analyses performed for BFN. ((
)) So some asymmetry is to be expected.
E2-71
NON-PROPRIETARY INFORMATION Figure EMCB.148/115-1: ((
)) The colors indicate the main steam line data plotted (Figure 4.1 of CDI Report No. 07-09P).
E2-72
NON-PROPRIETARY INFORMATION Figure EMCB.148/115-2: (( I] NRC RAI EMCB.149/116 In CDI Report No. 07-09P, a new Acoustic Circuit Model (ACM) Rev. 4 is developed to improve prediction of the dryer load at low frequencies. (( TVA Response to EMCB.149/116 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.113 by letter dated November 30, 2007 (ML073460793). This response by Hope Creek equally applies to the analyses performed for BFN. E2-73
NON-PROPRIETARY INFORMATION (( NRC RAI EMCB.150/117 In the development of the hydrodynamic load contribution on page 8 of CDI Report No. 07-09-P, reference is made to pressure fluctuations p = 0.1 pU2 . Address whether this estimate is used in equation 4.1 for the source strength, and discuss the other parameters used in equation 4.1. Specifically: (a) If the estimate p = 0.1 pU2 is used in equation 4.1, validate this estimate from (( )) on the dryer, e.g. from QC2 dryer measurements; and (b) Explain the parameters (( )) and their values which are used in equation 4.1. TVA Response to EMCB.150/117 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.114 by letter dated November 30, 2007 (ML073460793). This response by Hope Creek equally applies to the analyses performed for BFN. (a) The estimate p = 0.1 PU 2 is not used for the source strength. It results from estimating the pressure E2-74
NON-PROPRIETARY INFORMATION fluctuations from turbulent buffeting from q = 1/2pU2 and assuming that U is the steady flow velocity and the velocity fluctuations are 10% of the steady flow velocity. (b) Equation 4.1 is: AP = KP-{22 } with the following variables: (1) The variable K/rj 2 is the pressure loss coefficient associated with the inlet to the main steam and has the value of 1.0 in the ACM model. (2) The variable i/ro is the normalized unsteady fluctuation in the vena contracta and is a dependent variable in the ACM model. (( (3) The variable ii/U is the normalized velocity fluctuation into the main steam line and is also a dependent variable in the model that is directly determined from the two independent pressure measurements made on each steam line. Again, no value can be prescribed for ýi since it is a dependent variable. In CDI Report No. 07-09P the subscript lower case b is a typographical error and should be dropped so that lIb = 4. NRC RAI EMCB.151/118 On page 4 of CDI Report No. 07-09P, CDI develops a new ACM code to improve the prediction of dryer load at low frequency. The E2-75
NON-PROPRIETARY INFORMATION report states that the Helmholtz and ACM analyses are driven by (( )) In the new ACM Rev. 4, it appears that (( TVA Response to EMCB.151/118 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.115 by letters dated November 30, 2007 (ML073460793) and January 15, 2008. These responses by Hope Creek equally apply to the analyses performed for BFN. The ACM modeling parameters are summarized below: E[ E2-76
NON-PROPRIETARY INFORMATION source main steam line Periodic vorticity injection into main rsteam line In the main steam line the pressures (p) in frequency space satisfy p -Aei(kx+cot) + Bei(-kx+ot) where k =- is the wave number a
- is the circular frequency x - is the coordinate measured downstream in the main steam line t - is time a - is the complex acoustic speed ar + ia1 In this analysis the main steam line convection has been omitted as it is very small and the friction damping in the pipe is E2-77
NON-PROPRIETARY INFORMATION neglected as it is small compared to the damping from the imaginary part of the complex acoustic speed. The pressures are measured in the MSL as per the schematic below Vessel r i 11x 01j4--- 1L -
- The pressures are measured at x = 0 and x = L and they are respectively P 1 (o) and P2 (W) . Some algebra shows that the pressure valid along the main steam line is E2-78
NON-PROPRIETARY INFORMATION NRC RAI EMCB.152/119 The pressure fluctuations measured by the strain gages on the MSLs contain noise signals that are not acoustic in nature. In CDI Report No. 07-09-P, the (( 1)) Provide information about these methods of noise removal. In particular, TVA should provide: (a) [L (b) ((
)) and (c) a more detailed explanation of step 3.
TVA Response to EMCB.152/119 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.116 by letters dated November 30, 2007 (ML073460793) and January 18, 2008. These responses by Hope Creek equally apply to the analyses performed for BFN. Specific exclusion frequencies that were used for BFN were provided in Table 3.2 of CDI Report No. 07-10P (Enclosure 4 of our July 27, 2007 letter). As discussed in CDI Report No. 07-09P, signal noise is removed from the data by three means: (a) (( E2-79
NON-PROPRIETARY INFORMATION Typical values of the factor may be taken from the Hope Creek main steam line data at the A upper strain gage (as an example). These values are shown below at selected frequencies, averaged from -0.5 Hz to 0.5 Hz around the frequency listed: (b) 1(( E2-80
NON-PROPRIETARY INFORMATION (c) The reference J. S. Bendat and A. G. Piersol, 1966, Measurement and Analysis of Random Data, John Wiley and Sons, Page 215, Table 5.1 (described in CDI Report No. 07-09P) gives 99% confidence limits on the coherence based on coherence estimates, as compiled in the table below). Coherence Cohestime Lower Confidence Limits Estimate 0.4 0.19 0.5 0.29 0.6 0.41 0.7 0.54 0.8 0.68 0.9 0.83 A plot of these data gives the following: 1 0 99% Confidence Limit 0.8 100% Confidence Limit - ----- - Average Confidence Limit 0.6 -------- ------- --------
-' /
0.4
-- --- -I -- -- --- --- -- :l
- ik - -- - - - - - -- - - - - - - -- - - - - - -
0.2 0 U U/ 0 0.2 0.4 0.6 0.8 1 Computed Coherence (x) where a linear curve fit through the data points (black circles) gives the line y = -0.346+1.286x (R 2 = 0.995) in black, the one-to-one curve (no correction) in blue, and the line halfway between the linear curve fit and no correction (halfway to the lower confidence limits, identified in the figure as the average confidence limit) in red. The average confidence limit recovers a corrected coherence that is more conservative (a higher value) than use of the 99% confidence limit as suggested in the data of E2-81
NON-PROPRIETARY INFORMATION Bendat and Piersol, as it follows from the equation y = -0.173+1.143x. For example, if the computed coherence between the upper and lower strain gage measurements is 0.6, no correction would leave the coherence at 0.6, use of the 99% confidence limit curve would give a corrected coherence of 0.4, while an average coherence value would give 0.5. The average values are used in the analysis. (( F.2-82
NON-PROPRIETARY INFORMATION NRC RAI EMCB.153/120 Benchmarking of the new ACM Rev. 4 against the data of QC2 dryer is presented in CDI Report No. 07-09-P. Validate the new version of ACM Rev. 4 against data from additional dryers exposed to strong low frequency loading (e.g. Susquehanna). Additionally, provide validation of this new methodology against additional dryer data where the low frequency loading is pronounced. TVA Response to EMCB.153/120 This RAI is associated with the methodology utilized by CDI in the steam dryer stress analyses performed for BFN and Hope Creek. The response to this question was previously provided by Hope Creek in response to Hope Creek RAI 14.118 by letters dated November 30, 2007 (ML073460793), January 15, 2007, and F2-83
NON-PROPRIETARY INFORMATION January 18, 2008. These responses by Hope Creek equally apply to the analyses performed for BFN. No additional data sets are available to TVA to undertake further validation of ACM Rev. 4. Comparison of prediction against the Quad Cities data is favorable. (( 1] Examining steam line data between Quad Cities and BFN (see for instance MSL C upper location on Figure EMCB.153/120-1) the low frequency pressures are generally greater on Quad Cities than on BFN's main steam line above 16 Hz. MSL C Upper 1 0.1 0.01 ('2 0.001 0.0001 10-5 0 50 100 150 200 Frequency (Hz) Figure EMCB.153/120-1: Comparison of Quad Cities (QC), Browns Ferry (BF), Hope Creek (HC), and Susquehanna (SQ) main steam line data. The Quad Cities OLTP data at 790 MWe were used to select the ACM Rev. 4.0 modeling parameters. This data set was chosen because at this power level the Mach number in the steam lines at Quad Cities, M = 0.105, is above the Mach number of BFN at EPU conditions (M = 0.100). E2-84
NON-PROPRIETARY INFORMATION Scaling laws have been developed between full-scale and subscale tests indicating that the Mach number must be preserved between scales for similitude to apply. Between two identical nuclear plants, dryer loads may not be comparable unless data are compared at the same power level, which corresponds to the same Mach number. Therefore, between two different power plants the most relevant data to examine would be data at comparable Mach number, especially if the geometries are similar. It would be desirable to benchmark the ACM Rev. 4.0 model at Quad Cities power levels below M = 0.105, say at a Mach number corresponding to CLTP conditions at BFN. Unfortunately, data below M = 0.105 do not exist, but higher Mach number data have been recorded. We have therefore selected the next data set at power conditions above Quad Cities OLTP, corresponding to 820 MWe (M = 0.110). Comparisons of the Rev. 4.0 model (CDI Report No. 07-09P) with this data set are essentially a blind benchmark, as these data have not been analyzed previously and the ACM Rev. 4.0 model has locked parameters. The results of the blind benchmark are summarized below; a detailed comparison of the pressure data taken on the dryer with ACM Rev. 4.0 predictions follows. Details are now provided for the ACM Rev. 4 model comparison at 820 MWe. Minimum and maximum pressures at the sensors are shown in Figure EMCB.153/120-2, and comparisons with QC2 data are provided in Figures EMCB.153/120-3 through EMCB.153/120-16 at E2-85
NON-PROPRIETARY INFORMATION all sensor locations. It may be noted that sensors P13, P14, P16, P23, and P27 are positioned inside the dryer, that P26 is on a mast above the dryer, and that P19 is considered inoperative by GE. Predictions of minimum and maximum peak pressures bound the QC2 dryer data except for sensors P16 and P27 (on the inside of the dryer). Bias and uncertainty for 820 MWe are computed in a manner identical to that discussed in CDI Report No. 07-09P, using six "averaged pressures" by averaging pressure sensors P1, P2, and P3; P3, P5, and P6; P7, P8, and P9; P10, P11, and P12; P18 and P20; and P19 and P21. These pressure sensors were all on the outer bank hoods of the dryer, and the groups are comprised of sensors located vertically above or below each other. Comparisons of the six averaged pressures with averaged data are shown in Figures EMCB.153/120-17 through EMCB.153/120-19. E2-86
NON-PROPRIETARY INFORMATION (( Figure EMCB.153/120-2: Summary of Rev. 4 pressure predictions at 820 MWe at the dryer pressure sensors: peak minimum (top) and peak maximum (bottom) pressure levels, with data (blue) and predictions (red). Sensors P13, P14, P16, P23, and P27 are inside the dryer, while P26 is on a mast above the dryer. E2-87
NON-PROPRIETARY INFORMATION I[ Figure EMCB.153/120-3: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P1 (top) and P2 (bottom). F2-SS
NON-PROPRIETARY INFORMATION Figure EMCB.153/120-4: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P3 (top) and P4 (bottom). E2-89
NON-PROPRIETARY INFORMATION E[ Figure EMCB.153/120-5: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P5 (top) and P6 (bottom). E2-90
NON-PROPRIETARY INFORMATION I] Figure EMCB.153/120-6: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P7 (top) and P8 (bottom). E2-91
NON-PROPRIETARY INFORMATION I[ Figure EMCB.153/120-7: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P9 (top) and P10 (bottom). E2-92
NON-PROPRIETARY INFORMATION E[
))
Figure EMCB.153/120-8: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P11 (top) and P12 (bottom). E2-93
NON-PROPRIETARY INFORMATION E[ Figure EMCB.153/120-9: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P13 (top) and P14 (bottom). E2-94
NON-PROPRIETARY INFORMATION (( Figure EMCB.153/120-10: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P15 (top) and P16 (bottom). E2-95
NON-PROPRIETARY INFORMATION Figure EMCB.153/120-11: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P17 (top) and P18 (bottom). E2-96
NON-PROPRIETARY INFORMATION E[ Figure EMCB.153/120-12: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P19 (top) and P20 (bottom). E2-97
NON-PROPRIETARY INFORMATION Figure EMCB.153/120-13: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P21 (top) and P22 (bottom). E2-98
NON-PROPRIETARY INFORMATION ((I Figure EMCB.153/120-14: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P23 (top) and P24 (bottom). E2-99
NON-PROPRIETARY INFORMATION Figure EMCB.153/120-15: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P25 (top) and P26 (bottom). E2-100
NON-PROPRIETARY INFORMATION Figure EMCB.153/120-16: PSD comparisons at 820 MWe for pressure sensor data (blue curves) and Rev. 4 model prediction (red curves), for P27. E2-101
NON-PROPRIETARY INFORMATION [1 Figure EMCB.153/120-17: PSD comparisons at 820 MWe for averaged pressure sensors P1, P2, and P3 (top) and P4, P5, and P6 (bottom): pressure sensor data (blue curves) and Rev. 4 model prediction (red curves). E2-102
NON-PROPRIETARY INFORMATION I] Figure EMCB.153/120-18: PSD comparisons at 820 MWe for averaged pressure sensors P7, P8, and P9 (top) and P10, P11, and P12 (bottom): pressure sensor data (blue curves) and Rev. 4 model prediction (red curves). E2-103
NON-PROPRIETARY INFORMATION Figure EMCB.153/120-19: PSD comparisons at 820 MWe for averaged pressure sensors P19 and P21 (top) and P18 and P20 (bottom): pressure sensor data (blue curves) and Rev. 4 model prediction (red curves). E2-104
NON-PROPRIETARY INFORMATION The values of the various ACM modeling parameters at the inlets of the MSLs are as follows: E[ These parameters were chosen for the following reasons: Acoustic Speed: an application of the ASME steam tables in subroutine form [1], used previously in examining pipe flow [2] determined that the acoustic speed at 1000 psid saturated steam conditions was 1484.3 ft/sec. Acoustic Speed Damping in Steam Dome: the steam dome is assumed to be lightly damped, as no structures, or moisture are present in the steam dome volume that can result in damping. (( E2-105
NON-PROPRIETARY INFORMATION
REFERENCES:
- 1. Indiana University Chemistry Department/Babcock and Wilcox Co. Fossil Generation Division. Subprograms of 1967 ASME Steam Tables. Quantum Chemistry Program Exchange Program No. SPHF006.
- 2. Bliss, D. B., T. R. Quackenbush, and M. E. Teske. 1982.
Computational Simulation of High-Speed Steady Homogeneous Two-Phase Flow in Complex Piping Systems. Transactions of the ASME Journal of Pressure Vessel Technology 104: 272-277. E2-106
NON-PROPRIETARY INFORMATION NRC RAIs EMCB.154/121 through EMCB.155.122 The following are associated with CDI Report 07-10-P, Acoustic and low frequency hydrodynamic loads at CLTP power level on Browns Ferry Nuclear Unit 2 steam dryer to 250 Hz, which is of a letter dated July 31, 2007. NRC RAI EMCB.154/121 In CDI Report No. 07-10P, ACM Rev. 4 is used to predict the dryer load of BFN2 from strain gage measurements on MSLs. No details, however, are given regarding the ((
)) Provide the following:
TVA Response to EMCB.154/121 (a) The PSDs are shown in Figure EMCB.154/121-1. (b) The dipole orientation is described in the response to RAI EMCB.149/116. E2-107
NON-PROPRIETARY INFORMATION (c) The ACM model parameters are summarized in the response to RAI EMCB.151/118. (d) The parameters are described in the response to RAI EMCB.150/117. Browns Ferry Entrance Source Strength 0.01 03 0.001 N U* z,, 0.0001 10.5 0 20 40 60 80 100 Frequency (Hz) Figure EMCB.154/121-1: Normalized PSD of entrance source strengths f for Browns Ferry Unit 1 CLTP conditions. The colors indicate the main steam line data plotted. (( E2-108
NON-PROPRIETARY INFORMATION I] E2-109
NON-PROPRIETARY INFORMATION Figure EMCB.154/121-2 E2-110
NON-PROPRIETARY INFORMATION 1] Figure EMCB.154/121-3 E2-111
NON-PROPRIETARY INFORMATION NRC RAI EMCB.164/131 The following RAIs are associated with CDI Technical Memorandum No. 07-26-P, Comparison of Browns Ferry Nuclear Unit 1 and Unit 2 Main Steam Line Strain Gage/Pressure Readings, is Enclosure 6 of a letter dated July 31, 2007. In calculating acoustic pressures from the MSL strain gage measurements, the variation in the MSL wall thickness at each strain gage location should be taken into account. Address whether the variation in the MSL wall thickness is considered in estimating the acoustic pressures presented in CDI TM 07-26-P. If not, then reevaluate the acoustic pressures for Units 1 and 2 considering the variation in the MSL wall thickness and discuss how that affects the conclusions made in CDI TM 07-26-P. TVA Response to EMCB.164/131 Wall thickness measurements were taken on the MSLs at the strain gage locations for both Unit 1 and Unit 2 data recordings. The measured wall thickness at each gage location was used to derive a specific strain-to-pressure conversion factor for that strain gage. The pressures computed using these conversion factors are incorporated into the PSD to Frequency graphs in CDI Technical Memorandum No. 07-26-P Figures 1, 2, 3, and 4 and compare Unit 1 to Unit 2. The intent of the above referenced report was to demonstrate that the Unit 1 MSL loads were bounded by Unit 2 MSL loads for the purpose of the Unit 1 steam dryer stress analysis; however, MSL strain gage data specific to Unit 1 will be used to revise the Unit 1 steam dryer stress analysis (see response to RAI EMCB.140/107). NRC RAIs EMCB.165/132 through EMCB.166/133 The following RAIs are associated with CDI Technical Note 07-30-P, Limit Curve Analysis with ACM Rev. 4 for Power Ascension at Browns Ferry Nuclear Unit 1, is Enclosure 1 of a letter dated August 21, 2007. NRC RAI EMCB.165/132 The submitted limit curves for Unit 1 are based on (a) Unit 2 MSL measurements, and on (b) Unit 1 dryer stresses computed using dryer loads from Unit 2 MSL measurements. Submit Unit 1 MSL strain gage limit curves that are based on Unit 1 MSL measurements, and on Unit 1 dryer stresses computed using dryer loads from Unit 1 MSL measurements. F2-1 1 2
NON-PROPRIETARY INFORMATION TVA Response to EMCB.165/132 As discussed in the response to EMCB.140/107, TVA will revise the Unit 1 steam dryer stress analysis utilizing the Unit 1 MSL strain gage data. The Unit 1 limit curves will be revised based upon the revised Unit 1 steam dryer stress analysis and submitted with that analysis. NRC RAI EMCB.166/133 Compare the revised Units 1, 2 and 3 limit curves to those for Hope Creek. For the Unit 1 limit curves, use the revised curves developed in response to RAI 165/132. For Unit 3 limit curves, use the curves developed in response to RAI 130/97. Also compare these limit curves to the MSL measurements for Quad Cities Unit 2 data at OLTP conditions prior to the installation of Acoustic Side Branches on the SRVs. TVA Response to EMCB.166/133 As discussed in the responses to EMCB.130/97 and EMCB.140/107, TVA will revise the Units 1 and 3 steam dryer analyses utilizing unit-specific MSL strain gage data. Additionally, as discussed in the RAI Round 15 EMCB Response Status and Schedule at the front of this enclosure, the Unit 2 stress analysis is being revised. The revised limit curves for Units 1, 2, and 3 will be submitted with their respective stress analyses in order to allow the NRC to perform comparisons with other utilities. E2-113
ENCLOSURE 3 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT (BFN) UNITS 1, 2, AND 3 TECHNICAL SPECIFICATIONS (TS) CHANGES TS-431 AND TS-418 EXTENDED POWER UPRATE (EPU) RESPONSE TO ROUND 15 REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING STEAM DRYER ANALYSES AFFIDAVIT Attached is CDI's affidavit for the proprietary information contained in the response to Round 15 RAIs regarding steam dryer analyses provided in Enclosure 1.
4001' Continuum Dynamics, Inc. (609) 538-0444 (609) 538-0464 fax 34 Lexington Avenue Ewing, NJ 08618-2302 AFFIDAVIT Re: Browns Ferry Nuclear Plant (BFN) - Units 1,2, and 3 - Technical Specifications (TS) Changes TS-431 and TS-418 - Extended Power Uprate (EPU) - Response to Round 15 Request for Additional Information (RAI) Regarding Steam Dryer Analyses I, Alan J. Bilanin, being duly sworn, depose and state as follows:
- 1. I hold the position of President and Senior Associate of Continuum Dynamics, Inc. (hereinafter referred to as C.D.I.), and I am authorized to make the request for withholding from Public Record the Information contained in the documents described in Paragraph 2. This Affidavit is submitted to the Nuclear Regulatory Commission (NRC) pursuant to 10 CFR 2.390(a)(4) based on the fact that the attached information consists of trade secret(s),of C.D.I. and that the NRC will receive the information from C.D.I. under privilege and in confidence.
- 2. The Information sought to be withheld, as transmitted to TVA Browns Ferry as attachments to C.D.I. Letter No. 08022 dated 31 January 2008, Browns Ferry Nuclear Plant (BFN) - Units 1, 2, and 3 - Technical Specifications (TS) Changes TS-431 and TS-418 - Extended Power Uprate (EPU) - Response to Round 15 Request for Additional Information (RAI) Regarding Steam Dryer Analyses.
- 3. The Information summarizes:
(a) a process or method, including supporting data and analysis, where prevention of its use by C.D.I.'s competitors without license from C.D.I. constitutes a competitive advantage over other companies; (b) Information which, if used by a competitor, would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product; (c) Information which discloses patentable subject matter for which it may be desirable to obtain patent protection. The information sought to be withheld is considered to be proprietary for the reasons set forth in paragraphs 3(a), 3(b) and 3(c) above.
- 4. The Information has been held in confidence by C.D.I., its owner. The Information has consistently been held in confidence by C.D.I. and no public disclosure has been made and it is not available to the public. All disclosures to third parties, which have been limited, have been made pursuant to the terms and
conditions contained in C.D.I.'s Nondisclosure Secrecy Agreement which must be fully executed prior to disclosure.
- 5. The Information is a type customarily held in confidence by C.D.I. and there is a rational basis therefore. The Information is a type, which C.D.I. considers trade secret and is held in confidence by C.D.I. because it constitutes a source of competitive advantage in the competition and performance of such work in the industry. Public disclosure of the Information is likely to cause substantial harm to C.D.I.'s competitive position and foreclose or reduce the availability of profit-making opportunities.
I declare under penalty of perjury that the foregoing affidavit and the matters stated therein are true and correct to be the best of my knowledge, information and belief. Executed on this ! day of,- -Y 2008. Alan J. Bilanin Continuum Dynamics, Inc. Subscribed and sworn before me this day:*/. cý2&&S EILEEN P. BURMEISTER NOTARY PUBLIC OF NEW JERSEY MY COMM. EXPIRES MAY 6, 2012}}