ML083250114
| ML083250114 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/14/2008 |
| From: | Emens J Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC MD5262, TAC MD5263, TAC MD5264, TS-418, TS-431, TVA-BFN-TS-418, TVA-BFN-TS-431 | |
| Download: ML083250114 (27) | |
Text
Tennessee Valley Authority, Post. Office Box 2000, Decatur, Alabama 35609-2000 November 14, 2008 TVA-BFN-TS-418 10 CFR 50.90 TVA-BFN-TS-431 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop OWFN, P1-35 Washington, D. C. 20555-0001 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-418 AND TS-431 - EXTENDED POWER UPRATE (EPU) - SUPPLEMENTAL RESPONSE TO ROUNDS 19 AND 22 REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING STEAM DRYERS (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 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 by approximately 14 percent to 3952 megawatts.
On August 12, 2008, NRC staff issued a Round 19 RAI (ML082340002) regarding the EPU steam dryer analyses. By letters dated September 2, 2008 (ML082490169),
October 3, 2008, (ML082810471), and October 31, 2008, TVA provided responses to the Round 19 RAI and the draft Round 22 RAI. Enclosure 1 provides the completed responses for Round 19 RAI EMCB.147 and draft Round 22 RAIs EMCB.200/157 and EMCB.160 regarding the steam dryer analyses for EPU. This completes the response to the Round 19 RAIs and the Round 22 RAIs associated with the steam dryers.
In order to standardize the analysis and design of the BFN steam dryers, TVA has decided to perform additional modifications to the Unit 2 steam dryer to replicate the Unit 1 steam dryer design. This approach demonstrates the acceptability of the steam dryer design for the loadings that are experienced by both Units 1 and 2. As discussed in , the steam dryer stress analysis for Unit 2 has been re-performed to reflect these modifications and to include stress results at EPU conditions. The Unit 2 steam dryer stress analysis is provided in Enclosure 2, CDI Report No.08-20P, "Stress akBD
U.S. Nuclear Regulatory Commission Page 2 November 14, 2008 Assessment of Browns Ferry Nuclear Unit 2 Steam Dryer with Outer Hood and Tie-Bar Reinforcements."
Note that Enclosures 1 and 2 contain information that Continuum Dynamics, Inc. (CDI) considers to be proprietary in nature and subsequently, pursuant to 10 CFR 2.390(a)(4),
CDI requests that such information be withheld from public disclosure. Enclosure 5 provides an affidavit from CDI supporting this request. Enclosures 3 and 4 contains the redacted versions of the proprietary enclosures with the CDI proprietary material removed, which are suitable for public disclosure.
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 1 4 th day of November, 2008.
Sincerely, James E. Emens, Jr.
Licensing Supervisor
Enclosures:
- 1. Supplemental Response to Rounds 19 and 22 Request for Additional Information (RAI) Regarding Steam Dryers (Proprietary Version)
- 2. CDI Report No.08-20P, "Stress Assessment of Browns Ferry Nuclear Unit 2 Steam Dryer with Outer Hood and Tie-Bar Reinforcements" (Proprietary Version)
- 3. Supplemental Response to Rounds 19 and 22 Request for Additional Information (RAI) Regarding Steam Dryers (Non-proprietary Version)
- 4. CDI Report No. 08-20NP, "Stress Assessment of Browns Ferry Nuclear Unit 2 Steam Dryer with Outer Hood and Tie-Bar Reinforcements" (Non-proprietary Version)
U.S. Nuclear Regulatory Commission Page 3 November 14, 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 Ms. Eva Brown, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Eugene F. Guthrie, Branch Chief U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 NRC Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, Alabama 35611-6970
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)
SUPPLEMENTAL RESPONSE TO ROUNDS 19 AND 22 REQUEST FOR ADDITIONAL INFORMATION (RAI) REGARDING STEAM DRYERS (NON-PROPRIETARY VERSION)
Attached is the non-proprietary version of the Supplemental Response to Rounds 19 and 22 RAI Regarding Steam Dryers.
NON-PROPRIETARY INFORMATION SUPPLEMENTAL RESPONSE TO ROUND 19 RAI NRC RAI EMCB.147 (Unit 2 only)
Provide analysis and plots for Unit 2 similar to those provided for Unit 1 in response to RAI EMCB. 172. Provide an explanation why the 19-percent power data shown in Figures 3.2 through 3.5 in CDI Report No.08-05P, Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level on Browns FerryNuclear Unit 2 Steam Dryer to 250 Hz, are higher than the data at CLTP for frequencies above about 120 Hz. Provide justification for removing any signal from the Unit 2 CLTP source strengths without reliable background noise signals. TVA should include stress and stress ratio tables in CDI Report 08-16P, Stress Assessments of Browns FerryNuclear Unit 2 Steam Dryer with Tie Bar and Hood Modifications, using unfiltered MSL signals.
Supplemental Response to EMCB.147 (Unit 2 only)
As discussed in the response to RAI EMCB.147 in the October 3, 2008, submittal, "Supplemental Response to Round 19 RAI and Response to Rounds 20 and 21 RAI" (ML082810471), the Unit 2 steam dryer stress analysis is being re-performed with newly acquired low flow (LF) and companion electrical interference check (EIC) signals taken at 5%
power. The new LF signal replaces the previous 19% power signal which was determined to be atypical of the plant operating state. The current licensed thermal power (CLTP) signals have not been changed. The signals used in the Unit 2 stress analysis is illustrated in Figures 3.2 through 3.5 of CDI Report No.08-05P, "Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level on Browns Ferry Nuclear Unit 2 Steam Dryer to 250 Hz," which was provided as Enclosure 4 of the submittal dated October 31, 2008, "Supplemental Response to Round 19 RAI and Response to Round 22 RAIs Regarding Steam Dryers."
In order to standardize the analysis and design of the BFN steam dryers, TVA has decided to perform additional modifications to the Unit 2 steam dryer to replicate the Unit 1 steam dryer design. This approach demonstrates the acceptability of the steam dryer design for the loadings that are experienced by both Units 1 and 2. These modifications will include:
" Replacement of the 3/8 inch thick cover plates with 1 inch cover plates
" Replacement of the 1/2 inch thick hood face plates at 900 and 2700 with 1 inch hood face plates
- Removal of the two 1/4 inch vertical stiffeners behind each of the outer hood face plates and addition of two vertical stiffening channels on each hood face
- Removal of support beam ends
- Tie bar modifications
" Addition of steam dam support gussets The completed Unit 2 steam dryer stress analysis is provided in Enclosure 2, CDI Report No.08-20P, "Stress Assessment of Browns Ferry Nuclear Unit 2 Steam Dryer with Outer Hood and Tie-Bar Reinforcements." The revised Unit 2 stress analysis includes the following changes:
0 Utilized a new LF signal and companion EIC signal as discussed above.
E3-1
NON-PROPRIETARY INFORMATION
" Included modifications that result in a similar design for the Units 1 and 2 steam dryers as discussed above.
" Incorporated the results of submodel analyses as was previously used on the Unit 1 steam dryer analysis.
- Incorporated the results of submodel analysis as described in Appendix A of CDI Report No. 20P.
- Evaluated stress results at EPU conditions by the use of bump-up factors as described in the response to RAI EMCB.192/150 in the October 31, 2008 submittal.
New Unit 2 results based on the above changes indicate a minimum alternating stress ratio with frequency shifts of SR-a = 3.39 at CLTP and SR-a = 2.16 at EPU.
Analysis and Plots Similar to Unit 1 RAI EMCB.172 The power spectral densisty (PSD) plots of the (( )) signals at each of the main steam line (MSL) entrances are reproduced below in Figures EMCB.147-2a through 2h.
Since the noise floor is shown to be significantly lower than the low power signal, the spectral subtraction strategy can be applied. The noise removal scheme is described in CDI Report No.08-20P, specifically the paragraph containing equations (8) and (9). This is represented in the following equation:
P(f) =Po(f)*maxj31,I -&(
where the signal cannot be reduced to less than 13times it's original (i.e., with noise) amplitude.
Previously, the noise removal scheme allowed the signal to be reduced to zero (this corresponds to setting 13= 0). More recently, the practice was to limit signal reduction to no less than 50% of its original value (13 = 0.5) which corresponds to an amplitude reduction of 3 decibels (dB) or less. The results presented here utilized 13= 0.5. The low power data was obtained at 5% power. For comparative consistency, coherence filtering has not been applied to these signals. Coherence filtering is used when generating stress results.
As was observed for the Unit 1 loads, these plots show that at low frequencies, the CLTP signals with and without noise filtering are in good agreement. At higher frequencies, the noise increases producing a stronger reduction in the amplitudes. The filtered (( )) PSD plots are in close agreement with the unfiltered CLTP signals. The filtered (( )) signals differ from the unfiltered ones in the higher frequency range since the low power non-acoustic signals are more significant (relative to the acoustic signals) in this range. The 5% power signal is generally below or comparable to the CLTP signal at higher frequencies. When the 5% and CLTP signals are of equal amplitude, one would expect that pipe vibrations or other non-acoustic sources dominate and that the acoustic signal strength are negligible - on the order of 30% or less. However, with 13= 0.5 filtering, the filtered signal amplitude is never less than one half the unfiltered signal, adding conservatism to the overall filtering process.
The reduction in signal amplitude peaks as a function of frequency is shown for the ((
)) in Figure EMCB.147-3. These reductions in peak amplitude are obtained by:
(1) identifying the peaks in the PSDs for the CLTP signals with no noise reduction, (2) locating the nearest peak in the CLTP signal with noise reduction, and then (3) calculating the amplitude E3-2
NON-PROPRIETARY INFORMATION reduction. For the (( )) signals, only those PSD peaks (without noise filtering) higher than 2x 104 psi 2/Hz are plotted. For the (( )), peaks higher than 5x 10-5 psi 2/Hz are plotted. Since P = 0.5, several points fall on the 50% line since limiting has occurred. The general trend is a growing amplitude reduction with frequency in the 0-100 hertz (Hz) range. At higher frequencies, the amplitude reductions can be anywhere between the 0-50% range as one might expect when the signal is dominated by a non-acoustic component (e.g., mechanical noise) that does not scale directly with power. For the (( )) peaks, the effects of noise reduction are restricted to the 0-60 Hz range. The amplitude reductions are small in this range.
Tables EMCB. 147-1a and 1 b are provided to provide quantitative measures of the reductions in MSL pressure signals after noise filtering (here with P = 0.5) is applied at the frequencies with the strongest contributions to the stress response. For each MSL (( )), the ten highest PSD peaks identified in the 0-250 Hz range without noise filtering are listed. For each such peak, the nearest peak with noise filtering is identified and the relative amplitude reduction is calculated. The (( )) are listed in the same manner except that all PSD peaks above 5x 10-5 psi 2/Hz are listed. With few exceptions, the peaks below 100 Hz (non-shaded) experience percentage amplitude reductions that are in the single digit range or mid-teens. At higher frequencies, stronger amplitude reductions occur as already discussed.
The effects of filtering noise on the basis of the 5% power signal upon stress are examined for the limiting nodes on the Unit 2 steam dryer. The limiting nodes are obtained using the latest steam dryer model with all modifications such as tie bar modifications, added steam dam gussets, and replacement of the outer hood.by a thicker hood with external reinforcement channel assemblies instead of interior hood supports. The limiting nodes are obtained from Table 8b of CDI Report No.08-20P and are identified by subjecting the dryer to the filtered (with P = 0.5) MSL inlet pressure signals at CLTP and searching for the nodes with the lowest alternating stress ratios. The same nodes are then re-processed using the unfiltered signal with values of P = 0.5. The limiting nodes and the effects of noise reduction upon the computed stress ratios are summarized in Table EMCB.147-2. The listed frequency shifts indicate at what shift the smallest alternating stress intensity is produced. For the listed nodes, the limiting frequency shifts are identical for both the filtered and unfiltered signals. In order to quantify the frequency-dependent effect of noise reduction on computed stresses, the accumulative PSDs with and without noise reduction are compared for the same eight nodes in Figures EMCB.147-4a through 4d.
E3-3
NON-PROPRIETARY INFORMATION Table EMCB.147-1a: Reductions in (( )) amplitude peaks due to noise filtering (P = 0.5)
MSL Frequency PSD Frequency PSD (P=0.5) % Amplitude
[Hz] [psi 2/Hz ] x 10 4 (P=0.5) [Hz] [psi 2/Hz] x 104 Change A 217.06 10.37 217.06 4.09 -37.2 i 228.19 8.32 228.19 2.08 -50.0 224.24 7.,32 224.24 1.83 -50.0 202.59 6.48 202.63 2.19 -41.9 110.39 6.34 110.38 3.20 -29.0 199.87 6.08 199.86 1.98 -42.9 189.30 5.14 189.30 1.28 -50.0 231.63 4.76 231.63 1.19 -50.0 94.94. 3.77 194.94 0.96 -49.7 240.37 3.51 240.37 0.88 -50.0 B 27.22 3.97 27.22 3.33 -8.4 246.26 3.48 246.26 0.87 -50.0 201.99 3.48 201.99 1.27 -39.5 199.93 3.03 199.92 1.06 -40.8 15.21 2.88 15.21 2.67 -3.7 110.28 2.68 110.23 1.26 -31.3 64.28 2.64 64.28 1.90 -15.0 186.41 2.62 186.41 0.65 -50.0 217.12 2.39 217.10 0.96 -36.5 94.82 2.30 94.83 1.38 -22.5 C 27.36 9.49 27.36 8.48 -5.4
" 15.20 9.47 15.20 9.11 -1.9 246.18 5.96 246.18 1.49 -50.0 34.47 4.54 34.47 3.99 -6.3 93.70 4.19 93.70 2.89 -17.0 64.89 3.73 64.88 2.54 -17.5 86.94 3.49 86.94 2.37 -17.6 186.70 3.38 186.72 1.74 -28.3 241.86 3.29 241.86 0.82 -50.0 117.57 3.21 117.58 2.17 -17.8 D 93.10 4.59 93.11 3.47 -13.0 113.29 4.15 113.34 2.55 -21.6 100.52 '3.59 100.51 2.63 -14.4
" 21.54 3.41 21.54 3.14 -4.1 29.92 3.33 29.92 2.95 -5.9
" 111.19 3.27 111.16 1.67 -28.5 187.81 2.78 187.81 1.51 -26.4 179.74 2.63 179.74 0.66 -50.0 37.52 2.61 37.52 2.35 -5.1 246.19 2.50 246.19 0.63 -50.0 E3-4
NON-PROPRIETARY INFORMATION Table EMCB.147-1b: Reductions in (( )) amplitude peaks due to noise filtering (I = 0.5)
MSL Frequency PSD 4 Frequency PSD (13=0.5) 4 % Amplitude
[Hz] [psi /Hz ] x 2 10 (13=0.5) [ Hz] [psi 2/Hz ] x 10 Change A 11.41 9.19 11.41 8.23 -5.3
" 7.11 1.23 7.11 0.88 -15.4 o 29.22 1.14 29.22 0.73 -19.8 14.07 0.96 14.13 0.79 -9.2 31.95 0.95 31.95 0.68 -15.6 19.12 0.91 19.12 0.76 -8.6 36.94 0.73 36.96 0.58 -11.1 16.81 0.68 16.81 0.54 -11.4 21.46 0.61 21.46 0.51 -9.1 B 15.24 2.89 15.24 2.65 -4.2
" 34.02 1.79 34.03 1.44 -10.2 5.33 1.74 5.33 1.44 -9.1 27.26 1.69 27.27 1.23 -14.6 29.42 1.11 29.42 0.67 -22.3 8.18 0.86 8.18 0.69 -10.5 12.77 0.75 12.79 0.66 -6.2 24.74 0.52 24.73 0.34 -18.8 C 15.19 11.14 15.19 10.65 -2.2 34.47 2.78 34.47 2.30 -9.2 27.35 2.46 27.34 2.00 -9.9 5.68 1.56 5.69 1.16 -13.7 29.39 1.19 29.38 0.82 -16.7 24.19 0.88 24.18 0.70 -10.7 31.76 0.71 31.76 0.46 -19.2 9.55 0.70 9.55 0.49 -16.3 21.45 0.65 21.45 0.55 -7.9 D 11.60 2.28 .11.61 2.04 -5.4 21.50 1.81 21.50 1.66 -4.3 29.94 1.78 29.95 1.42 -10.5 37.49 1.31 37.49 1.15 -6.3 5.16 1.18 5.16 0.96 -10.0 15.39 1.05 15.38 0.92 -6.5 26.13 0.87 26.12 0.67 -12.0 19.06 0.84 19.07 0.73 -6.4 34.79 0.75 34.81 0.61 -9.6
" 7.20 0.71 7.20 0.56 -11.6 9.56 0.68 9.56 0.50 -14.2 E3-5
NON-PROPRIETARY INFORMATION Table EMCB.147-2: List of nodes on welds in the Browns Ferry Unit 2 dryer having the lowest alternating stress ratios at CLTP.
Location Node Filtering with 5% power, 3=0.5 No filtering SR-P SR-a Freq. SR-P SR-a Freq.
Shift (%) Shift (%)
- 1. Top Cover Middle Hood/Middle 101376 6.44 3.39 -7.5 5.85 3.04 -7.5 Hood/Tie Bar
- 2. Dam Plate/New Gusset 92392 7.02 3.74 2.5 6.43 3.39 2.5
- 3. Dam Plate/New Gusset 104386 7.69 3.88 2.5 7.06 3.54 2.5
- 4. Dam Plate/New Gusset 104715 7.75 3.95 2.5 7.10 3.59 2.5
- 5. Old Hood Overlap/Top Cover 92842 5.95 3.95 5 5.67 3.59 5 Outer Hood/Thin Gusset Pad
- 6. Submerged Drain Channel/Skirt 104136 4.42 4.06 -10 4.18 3.60 -10
- 7. Top Thick Plate/Dam Plate/Tie 93568 6.82 4.20 -10. 6.31 3.84 -10 Bar/Top Cover Outer Bank
- 8. Top Cover Middle Hood/Outer 106443 2.4 4.22 2.5 2.20 3.50 2.5 Closure Plate/Middle Hood E3-6
NON-PROPRIETARY INFORMATION Figure EMCB.147-2a: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL A (( ))
pressure signals at CLTP E3-7
NON-PROPRIETARY INFORMATION Figure EMCB.147-2b: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL B (( ]
pressure signals at CLTP E3-8
NON-PROPRIETARY INFORMATION I]
Figure EMCB.147-2c: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL C (( ]
pressure signals at CLTP E3-9
NON-PROPRIETARY INFORMATION Figure EMCB.147-2d: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL D (( ]
pressure signals at CLTP E3- 10
NON-PROPRIETARY INFORMATION Figure EMCB.147-2e: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL A (( ]
pressure signals at CLTP E3-11
NON-PROPRIETARY INFORMATION Figure EMCB.147-2f: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL B (( ]
pressure signals at CLTP E3-12
NON-PROPRIETARY INFORMATION 1]
Figure EMCB.147-2g: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL C (( ]
pressure signals at CLTP E3-13
NON-PROPRIETARY INFORMATION Figure EMCB.147-2h: PSD curves for the low power (LP) unfiltered (CLTP) and filtered (CLTP-LP) MSL D (( ]
pressure signals at CLTP E3-14
NON-PROPRIETARY INFORMATION 0f
- -10 - . -
U1) gO S 0 S 0 -2 0 ----- ----- -- --
zS E
< -40 ......... - -_
0)) :
50 --- - _----
050 100 150 200 250 Frequency [ Hz ]
)) Amplitude Reduction C - 1 ---- -- -------
.U)
-...... I * ........ ..........
50 0 z 40 ------ o ---------
.(0' CU)
~-30 .
E 20 10 20 3 0 0 6
-40 0)
- -50 _ _1_ _ __ _i_ _ _ _ I__
0 10 20 30 40 50 60 Frequency [ Hz]
(( )) Amplitude Reduction Figure EMCB.147-3: Change in MSL pressure signal amplitude after noise reduction using the 5% power data E3-15
NON-PROPRIETARY INFORMATION Node 101376, azz (-7.5% shift) 400 -r_ ! 7 350 300 -
cc 250 75 200 L E 150
-.- Unfiltered i
..--. Filtered with 5% power data 100 50 0
0 50 100 150 200 2 50 Frequency [ Hz ]
Node 92392, a (+2.5% shift) 350 300 7.
250 200 ci U)
E 150 -
E 100 50 Unfiltered
Filtered with 5% power data 0
0 50 100 150 200 250 Frequency [ Hz ]
Figure EMCB.147-4a: Accumulative PSD curves for nodes 101376 and 92392 with and without noise reduction E3-16
NON-PROPRIETARY INFORMATION Node 104386, a (+2.5% shift) 350 300 -
0~
v1 250 -
ci C,)
0~
a) 200 Cu
-3 E 150 E
C.)
C.) 100 -
50 0
0 50 100 150 200 250 Frequency [ Hz ]
Node 104715, a (+2.5% shift) 500 400 C,)
300 E 200 E
100 0
0 50 100 150 200 250 Frequency [ Hz ]
Figure EMCB.147-4b: Accumulative PSD curves for nodes 104386 and 104715 with and without noise reduction E3-17
NON-PROPRIETARY INFORMATION Node 92842, axx (+5% shift) 350 300 W~
250 E~ 200 150 E
100 50 0 50 10 10 2-----
0 50 100 150 200 250 Frequency [ Hz ]
Node 104136, oya (4100%6 shift) 500 - TI --I-400 0-300 --
75 E 200 E
100
- Unfiltered
Filtered with 5% power data 0 5010____
0 50 100 150 200 250 Frequency [ Hz ]
Figure EMCB.147-4c: Accumulative PSD curves for nodes 92842 and 104136 with and without noise reduction E3-18
NON-PROPRIETARY INFORMATION Node 93568, az (-10% shift) 300 -T 250 75 200 E
Ei 150 100 50 ý_
0 I 50 10 100 I
Unfiltered Filtered with 5% power data I 0 150 200 250 Frequency [ Hz ]
Node 106443, axx (+2.5% shift) 250 200 Cl) a) 150 E 100 E
50 0
0 50 100 150 200 250 Frequency [ Hz ]
Figure EMCB.147-4d: Accumulative PSD curves for nodes 93568 and 106443 with and without noise reduction E3-19
NON-PROPRIETARY INFORMATION RESPONSE TO DRAFT ROUND 22 RAI NRC RAI EMCB.2001157 (Units I and 2)
As part of the presentation provided during the October 14, 2008, public meeting, TVA provided the following equation for the steam line unsteady pressure at CLTP:
PCLTP=CCLTp(CLTP-EICCLTP)-CLF(LF-EICL=),
where P is the steam line unsteady pressure, C is the coherence factor between upper and lower locations, LF is the low flow signal, and EIC is the signal taken with zero excitation voltage.
The equation implies that the coherence factors between the upper and lower strain gage locations are the same for both the CLTP signal and the corresponding EIC signal. However, it appears to the staff that the equation may not be conservative in all cases. In the event the coherence between the EIC signals on the upper and lower arrays is 0, it appears that the coherent portion of the signals at CLTP or LF already excludes the incoherent EIC signals.
Therefore, it appears that subtracting the EIC autospectra from the individual CLTP and LF signals and then multiplying by the coherence removes the EIC noise twice.
Address whether the EIC noise reduction procedure proposed removes the EIC noise twice. If the proposed does, provide the means to more appropriately account for the coherence of the EIC signals.
TVA Response to EMCB.2001157 (Units 1 and 2)
E3-20
NON-PROPRIETARY INFORMATION I]
NRC RAI EMCB.160 (Unit 2)
On slide 10 of the presentation provided during the October 14, 2008, public meeting, TVA provided graphs of the MSL EIC signals. For example, the variable frequency drive (VFD) spectral peaks are sometimes up to 4 orders of magnitude higher than the EIC signals used in the noise removal process. The EIC signals are, therefore, a very small fraction of the total dynamic input range of the measuring system. For example, if it is assumed that the measuring system is accurate within 0.1 percent of the dynamic input range, this error level is already about 10 times higher than the broadband level of the EIC signal, which is used for noise removal. Address the uncertainties in the EIC signals while it is removing the noise from the Unit 2 CLTP signals.
TVA Response to EMCB.160 (Unit 2)
Slide 10 of the presentation provided during the October 14, 2008 meeting showed PSD plots to illustrate unfiltered noise on BFN Unit 2. The PSD plot for MSL A Upper from Slide 10 is reproduced in Figure EMCB.160-1. The magnitude shown on the plot represents the square of the measured signal. Figure EMCB.160-2 is the same data with the Y-axis re-scaled to show the magnitude of the peaks. It can be seen that the peaks are two to three orders of magnitude above the nominal signal when considering the square root. The maximum peak signal is approximately 60 pounds per square inch (psi). The data acquisition equipment is scaled for a maximum range of 150 psi peak for all data collection at BFN, which is typical of other BWR steam dryer monitoring efforts. This avoids saturation of the instrumentation.
E3-21
NON-PROPRIETARY INFORMATION For the BFN Unit 2 steam dryer load definition, the uncertainty assigned to pressure measurement is 4.04% as discussed in the response to RAI EMCB.155/122 provided in the March 6, 2008, submittal, "Response to Round 15 RAI Regarding Steam Dryer Analyses, Group 2." Because the pressure measurements used for load definition are changes in strain relative to mean rather than absolute values, the uncertainty associated with the data acquisition equipment is determined by the sensitivity. Based upon a 150 psi peak maximum range, the minimum sensitivity of the measurement is 300pSi 2316 p -p- 0.O046psi for the 16-bit Analog to Digital converter. The nominal EIC signal is on the order of 0.01 psi and is well above the minimum resolution. The accuracy of the measurement system is 0.12% of the reading; consequently, the resolution is the most important factor in the uncertainty.
E3-22
NON-PROPRIETARY INFORMATION BFN2 A Upper EIC 0 .1 ---- ---
@5%Pove/15HzVFD (401 AU L-2EC
- L EC @83%Ported35 Hz VFD (22B) AU L02]C @1%Pover45 HzVFD (41D)AU 0.01 z 0.001 __
C4,
- 0. 0.00 0.00001 0.00001m________________
0 50 100 150 200 250 Frequency (Hz)
Figure EMCB.160-1: BFN Unit 2 MSL A Upper PSD Plot BFN2 A Upper EIC 100 10 0.1 0.01 a- 0.001 11 0.0001 0.00001 0.000001 0 50 100 150 200 250 Frequency (Hz)
Figure EMCB.160-2: Re-scaled BFN Unit 2 MSL A Upper PSD Plot E3-23