ML090760630

(BFN) - Units 1, 2, and 3 - Technical Specifications (TS) Changes TS-418 and TS-431 - Extended Power Uprate (EPU) - Steam Dryer Analyses Additional Information

ML090760630
Person / Time
Site:	Browns Ferry
Issue date:	03/11/2009
From:	West R 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: ML090760630 (10)

Text

Tennessee Valley Authority, Post Office Box 2000, Decatur, Alabama 35609-2000 March 11,2009 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) - STEAM DRYER ANALYSES ADDITIONAL INFORMATION (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. provides additional information related to previous submittals and telephone conferences with the NRC staff regarding the steam dryer analyses in support of EPU. In support of Enclosure 1, the Unit 1 stress analysis, load report, and limit curves have been completed and are enclosed. These analyses are provided in Enclosure 2, CDI Report No.08-15P, "Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer with Tie-Bar Modifications," Enclosure 3, CDI Report No.08-04P, "Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level on Browns Ferry Nuclear Unit 1 Steam Dryer to 250 Hz," and Enclosure 4, CDI Technical Note No.07-30P, "Limit Curve Analysis with ACM Rev. 4 for Power Ascension at Browns Ferry Nuclear Unit 1."

Note that Enclosures 2, 3, and 4 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 8 provides an affidavit from CDI supporting this request. Enclosures 5, 6, and 7 contain the redacted versions of the proprietary enclosures with the CDI proprietary material removed, which is suitable for public disclosure.

U.S. Nuclear Regulatory Commission Page 2 March 11, 2009 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 James Emens at (256)729-7658.

I declare under penalty of perjury that the foregoing is true and correct. Executed on this 11 1h day of March, 2009.

neely, R. G. West Site Vice President

Enclosures:

1. Steam Dryer Analysis Additional Information

2. CDI Report No.08-15P, "Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer with Tie-Bar Modifications," Revision 3 (Proprietary Version)

3. CDI Report No.08-04P, "Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level on Browns Ferry Nuclear Unit 1 Steam Dryer to 250 Hz,"

Revision 3 (Proprietary Version)

4. CDI Technical Note No.07-30P, "Limit Curve Analysis with ACM Rev. 4 for Power Ascension at Browns Ferry Nuclear Unit 1," Revision 2 (Proprietary Version)

5. CDI Report No.08-15P, "Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer with Tie-Bar Modifications," Revision 3 (Non-proprietary Version)

6. CDI Report No.08-04P, "Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level on Browns Ferry Nuclear Unit 1 Steam Dryer to 250 Hz,"

Revision 3 (Non-proprietary Version)

7. CDI Technical Note No.07-30P, "Limit Curve Analysis with ACM Rev. 4 for Power Ascension at Browns Ferry Nuclear Unit 1," Revision 2 (Non-proprietary Version)

8. CDI Affidavit

U.S. Nuclear Regulatory Commission Page 3 March 11, 2009 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 Ms. Heather J. Gepford, 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

ENCLOSURE1 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 ANALYSES ADDITIONAL INFORMATION Unit 1 Steam Dryer Stress Results with Revised Bias and Uncertainty Freauency Intervals The response to request for additional information (RAI) EMCB.204/168 in the submittal dated February 18, 2008, "Response to Round 23 RAI EMCB.204/168 Regarding Steam Dryer Analyses," (ADAMS Accession No. ML090510174) provided results of the assessment of steam dryer stress at EPU conditions with revised bias and uncertainty frequency intervals. During the telephone call with the NRC staff on February 20, 2009, additional results for current licensed thermal power (CLTP) and EPU conditions were requested. Additionally, by e-mail received March 4, 2009, the NRC staff requested revisions to Table 5.1, Figure 4.5, and Figure 4.6 of CDI Report No.08-04P and revisions to Tables 7a, 7b, 7c, 8a, 8b, 8c, 9a, 9b, and 9c of CDI Report No.08-15P.

In response to these requests, Enclosure 2 provides CDI Report No.08-15P Revision 3, "Stress Assessment of Browns Ferry Nuclear Unit 1 Steam Dryer with Tie-Bar Modifications," and provides CDI Report No.08-04P Revision 3, "Acoustic and Low Frequency Hydrodynamic Loads at CLTP Power Level on Browns Ferry Nuclear Unit I Steam Dryer to 250 Hz." These reports reflect the current steam dryer stress analyses for Unit 1 at CLTP and EPU conditions with revised bias and uncertainty frequency intervals requested by RAI EMCB.204/168.

New Unit 1 results based on the above changes indicate a minimum alternating stress ratio (SR-a) with frequency shifts of SR-a = 2.80 at CLTP and SR-a = 2.04 at EPU.

Revised Unit 1 Limit Curves During a telephone conference with the NRC staff on February 20, 2009, it was requested that the Unit 1 limit curves be prepared and submitted based upon the Unit 1 stress analysis results with revised bias and uncertainty frequency intervals utilized in the response to RAI EMCB.204/168. The requested limit curves are provided in Enclosure 4, CDI Technical Note No.07-30P Revision 2, "Limit Curve Analysis with ACM Rev. 4 for Power Ascension at Browns Ferry Nuclear Unit 1."

Unit 1 Steam Dryer Support Beam Analysis During the recent stress assessment for the Unit 1 steam dryer as presented in the submittal dated February 18, 2008, it was identified that the determination of stress associated with the weld on the support beams may not be appropriate for the installed weld configuration. The stress at the support beam welds included a weld factor of 1.8 which does not adequately E1-5

consider the actual weld configuration used to connect the support beam to the bottom of the dryer banks.

The support beams consist of two sections of 1/2 inch thick T-shaped beam running along the centerline on the dryer which are attached to the underside of the dryer vane banks and discharge plenum base plates with 1/4 inch stitch welds staggered on each side of the web.

Initially, the beam was also stitch welded to the support ring. However, as discussed in the response to RAI EMCB.169/137 in the submittal dated June 16, 2008, "Response to Round 15 Group 4 and Round 17 RAI," (ML081750080) when the Unit 1 steam dryer cover plate was removed during modifications, it was identified that the support beam stitch welds connecting the beam to the support ring had cracked at the welds. As a result, the Unit 1 dryer was modified to eliminate the outboard sections of the beams such that, now, they are only connected to the dryer banks. Similar modifications are planned for Units 2 and 3. Figure 1 shows the placement of the support beams on the bottom of the dryer banks. The support beams do not serve a structural purpose. The original purpose for the beams is believed to have been to facilitate assembly and transport.

Upper Support Ring Support Beams Nkký Figure 1: Steam Dryer Bottom Plan View of Support Beams In the assessment performed for the response to RAI EMCB.204/168, the alternating stress ratio for node 93153 at the end of a support beam (see Figure 2) was calculated to be E1-6

SR-a = 1.97 at EPU conditions. This Was calculated with the application of a 1.8 weld factor.

During examination of this node, it was recognized that the actual configuration should require the application of an additional weld factor to account for the undersized weld (1/4 inch weld on 1/2 inch plate). Examination of this weld configuration indicates that an additional undersize weld factor of 2.0 would be appropriate.

93153 Figure 2: Location of Node 93153 at end of Support Beam Accordingly, additional structural dynamic analyses have been performed to ensure that the support beams are adequately analyzed for their purpose. Since the support beams do not provide a primary structural function, they are being analyzed to ensure that they do not generate a loose part. With this approach, alternating and peak stresses were calculated while taking no credit for the welds connecting the support beams to the inner discharge plenum base plate at their inboard ends (approximately 15 inches) as shown on Figure 3. Although only the nodes associated with the innermost weld of the support beams exhibit SR-a < 2.0, it is evident from the configuration and the nature of the loading that if the welds at these nodes were not credited, the high stress condition would progress radially outward until an acceptable stress condition would be achieved. The configuration utilized in this analysis provides a conservative bound for simulating the final result.

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424 (ref)

Divider Panel (ref)

Vane Bank Sides (ref) Inner Plenum Base Plate (ref) 1" Long x 'A Leg Fillet Stitch - Web Near Side (typ)

(I Long x Leg Fillet Stitch - Web Far Side (typ)

.. ........ ~

.0 (tyvý ~ 2.0 týpJ)---

//z Rance of Assumed Stitch Wetd Disconn-ect (

Tee' /0.BeamWeb (ref -- 76 (re.f-* ,

Tee Beam Flange (ref)

Figure 3: Support Beam Illustration The analysis indicates that the high stress near the ends of the support beams are due to constraint of the inner discharge plenum base plates imposed by the support beams and that this stress is relieved when the support beams are disconnected in the region shown by Figure 3. Additionally, the stresses in the remaining support beam connections to the dryer vane banks are reduced when the welds on the inner discharge plenum base plates are not credited.

These results are presented in Table 1 for eight nodes on the support beams. The results include the application of the undersize weld factor. Four nodes (93153, 89873, 109160, and 109154) represent the inner discharge plenum base plate connections (which are not credited in the analysis) and four nodes (95791, 107676, 109155, and 110444) represent the first two nodes on each support beam which remain connected to the vane banks. The nodes that remain connected to the vane banks show reduced stresses at both CLTP and EPU conditions.

In summary, the support beams do not serve a primary structural function for the steam dryer and will remain in place on the steam dryer at EPU conditions. The results demonstrate that if no credit is taken for all welds not meeting the acceptance criteria (worst case assumes no credit for all welds on the inner plenum base plate), the remaining welds alone will maintain the support beams in place with a stress margin that exceeds the acceptance criteria.

Note that one other steam dryer location has been identified with undersize weld configurations.

The applicable undersize weld factor was incorporated in the current stress analysis results provided in Enclosure 2 and did not result in any nodes exceeding the acceptance criteria. This location is identified in Section 4.4 of CDI Report No.08-15P provided in Enclosure 2.

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Table 1: Support Beam Analysis Results Distance from Weld CLTP EPU I. T center of credited in 2 2 steam dryer final Original1 Final Original1 Final (inches) analysis? SR-a SR-a SR-a SR-a Support Beam 1 93153 0.75 No 1.34 5.43 0.98 3.82 89873 12.625 No 4.38 5.83 3.24 4.28 95791 15 Yes 3.09 3.52 2.25 2.58 107676 17.25 Yes 4.13 8.96 3.03 6.62 Support Beam 2 109160 0.75 No 1.34 5.04 0.98 3.50 109154 12.625 No 4.59 4.63 3.39 3.43 109155 15 Yes 3.20 4.86 2.36 3.56 110444 17.25 Yes 3.73 7.42 2.67 5.36 Support Beams 1 & 2 Remaining support beam nodes -- 2.7 > 2.0 1 Analysis results with all welds on support beams credited 2 Analysis results with no credit for welds connecting the support beams to the inner discharge plenum base plate at their inboard ends Summary of Unit 1 Submodel Calculations By e-mail received March 4, 2009, the NRC staff requested a summary of the submodel calculations for Locations 2, 3, and 4 in Table EMCB.204/168-1 of Enclosure 1 to the TVA letter dated February 18, 2009. It was requested that the summary include an explanation why these factors are smaller for some locations and higher for other locations. The requested information is provided in Section 4.5 of CDI Report No.08-15P (Enclosure 2).

Main Steam Line (MSL) Strain Gage Time History By e-mail received March 4, 2009, the NRC staff requested the length of the time history for the MSL strain gage measurements employed in the steam dryer stress analysis. MSL strain gage data measurements are taken for 120 seconds and provided to CDI for analysis. CDI utilizes 218 data points (at a time increment of 0.0004 seconds) for a total of 104.8576 seconds in the determination of steam dryer loads.

Comoarison of BFN and Hope Creek Steam Dryer Results During a telephone conference with the NRC staff on January 14, 2009, additional information was requested from TVA to characterize differences in the BFN and Hope Creek steam dryers relative to stress analyses results.

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The BFN steam dryer is a boiling water reactor (BWR) 4 slant hood design while the Hope Creek steam dryer is an upgraded BWR 4/5 curved hood design. Table 2 provides some dryer configuration differences relevant to steam dryer alternating stress analysis. The differences in dryer configuration cause different modal responses which combined with spectral differences in MSL unsteady pressures yield different alternating stress results.

The unsteady pressure measurements from the MSL strain gages do not significantly differ between BFN and Hope Creek. However, the specific acoustic loadings that are applied to the steam dryers are a result of the processing by the Acoustic Circuit Model (ACM) which takes into account the phasing, coherence, etc. of the signals which are processed by the ACM to determine load on the dryer. It is the coupling of these frequency specific loads with the structural response modes that determines the limiting stress nodes on the individual dryers.

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Table 2: BFN and Hope Creek Steam Dryer Design Details Detail BFN Units 1, 2, 3 EPU Dryer Design Hope Creek BWR/Dryer Design BWR 4 - Slant Hood Design BWR 4/5 - Curved Hood Design Reactor Vessel 251inches 251inches Diameter MSL Diameter 26 26 Steam Velocity at 167 EPU (feet/second)

SRV Resonance

~110 Hertz 118 Hertz Frequency MSL Dead Legs B&C None Blind flange Acoustic Vibration Suppressors standpipes installed on standpipes in flow None stream Dryer Banks 6 Parallel 6 Parallel Slanted hood hickCurved OuterHood modified tol inch hood 1/8 inch thick Outer96 5/8 inches high from bottom of 98 3/8 inches high from bottom of support ring support ring supportring Cover plate 1 inch thick 3/8 inch thick Modified to remove manway Manway 3/8 inch thick gusseted dam extends 15 1/2 inches above top Steam Dam of outer banks None Limiting locations for alternating stress 13 modified tie bars across top of Tie Bars vane 44 internal tie banks 37 tie bars across top of banks bars - 25 1/2" down No internal tie bars from the tops of the vane banks El-11