IR 05000260/1989021

Insp Rept 50-260/89-21 on 890123-24.Two of Three Items Reviewed During Insp Considered Closed.Major Areas Inspected:Responses to Three Open Items Identified in Insp Rept 50-260/88-38,including CSG-14,CSG-23 & CSG-26

ML20246N277
Person / Time
Site:	Browns Ferry
Issue date:	06/14/1989
From:	Cheng T, Terao D Office of Nuclear Reactor Regulation
To:
Shared Package
ML20246N275	List: IR 05000260/1989021 ML20246N270
References
50-260-89-21, IEB-79-14, NUDOCS 8909080075
Download: ML20246N277 (9)

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UNITED STATES NUCLEAR REGULATORY C0tiMISSION OFFICE OF NUCLEAI.' REACTOR REGULATION TVA PROJECTS DIVISION l Report No.: 50-260/89-21 Docket No.: 50-260 Licensee: Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, Tennessee <37402-2801 Facility Name: Browns Ferry Nuclear Plant, Unit 2 Inspection At: Stone & Webster Engineering Corporation (SWEC) Cherry Hill, New Jersey Inspection Conducted: January 23-24, 1989 Inspector: I [dfh9 Date ThomasM.Cheng,Teampder

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David Terao, Chief Date Enginecing Branch l; TVA Projects Divirsion Office of Nuclear Reactor Regulation

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Speciel Inspection Relating To Design Calculations for the Seismic Desien Program 1.0 INTRODUCTION AND BACKGROUND As documented in NRC Inspection Report (IR) 50-260/88-38 dated April 19, 1989 (Reference 5.1) the staff conducted an inspection of Browns ferry Nuclear Plant Unit 2 (BFN-2) Seismic Design Program. A total of 32 items were identified as sumarized in Enclosure 3 of IR 50-260/88-38. As a result of a follow-up inspection, six additional concerns were closed and the status of open items was sumarized in the IR 50-260/88-39 dated Junt- 14, 1989 (Reference 5.2).

IVA is required to resolve the remaining open items before restart of BFN- .0 PURPOSEANDSCofE The purpose of this special inspection was to review TVA'sThese responses to three three open of the open items identified in the NRC IR 50-260/88-3 'tems are: CSG-14 (Thermal Effects on Drywell Platforms), CSG-23 (Definition

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of Zero Period Acceleration of New Amplified Resp,onse Spectra), and CSG-26

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(Allowable Stress for Aluminum Conduit).

3.0 REVIEW FINDINGS dn January 23 and 24, 1989, the staff and its consultant conducted the third inspection of the bfN-2 seismic design program at Stone & Webster Engineering Corporation ef fice in Cherry Hill, New Jersey. The exit meeting was held on January 24, 1989 and the attendees are listed in Ericlosure The following subsections document the inspection findings, conclusion, and TVA's verbal comitments made during the exit meeting. An updated status sumary of all the open items identified in IR 50-260/68-38 is provided in Enclosure .1 (3.2.4)* Themal Effects on Drywell Platforms As discussed in IR 50-260/88-38, the review of TVA calculations B41-860612-006 and B22-881015-123 for the platform at Elevation 563'-0 found that the thermal loads on the radial beams due to the expansion of the diaphragm beams were not considered in the platform evaluation. This concern applies to all platforms inside drywell,

"A Ine number in the parenthesis denotes the section number in Reference _ _ _ - _ _ - _ _ _ _

. _ . _ _ _ _ _ _ i ? To address this concern, TVA performed additional calculations taking into

&ccount the effects of thermal exr m ion due to normal and accident temper-  '

atures. For the worst case, TVA r cted the radial beam (at azimuth 171 degrees) of the platform located a .l.563'-0" for the evaluation. TVA's calculation B22 890126 111 showed that the additional stresses due to The these staff two loading condi'. ions on the radial beam did not cause overstres consultant revi u ed TVA's calculation package and found that since the plat-form can expand freely in the radial direction, the resulting beam stresses under the two loading conditions are relatively small and the combined stresses are within code allowable. The staff considered this item closed. (CSG-14) 3.2 (3.5.8) Definition of Zero Period. Acceleration of New ARS As documented in IR 50-260/P8-38, the staff fcund that TVA calculated the new amplified response spectra (ARS) only up to 20Hz (the rigid frequency of buildings as defined in the BFN FSAR) and used the peak of floor acceleration time history as the zero-period acceleration (ZPA) of new ARS. TVA was required to demonstrate the adequacy of its ZPA definition for all new AR As discussed in IR 50-260/88-39, TVA planned to address this concern in two wayr; 1.e., (1) comparison of ARS, and (2) sample piping analysis. The staff review of the two appro ches is sumarized below:

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3.2.1 Comparfson of ARS For the study of ARS outside drywell in the reactur building, TVA presented a comparison of the horizontal (North-South and East-West) and vertical 0.5'. damped ARS. The first set of ARS was calculated up to 50 Hz and the building - analysis included the cumulative modal mass as high as 90% of the totr, mas 'cond set was obtained based on the 20 Hz cutoff frequencv for tha cild-

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The ing. A single-stick lumped-mass reactor building raodel censistent with he BFN FSAR and time history anal / sis technique were used to generate both hcri-zontal and vertical ARS. The comparison showed that the differences between the spectral accelerations of the two sets of ARS at 20 ht were very smal In addition, the differences between the spectral accelention at 20 Hz and the peak of the floor acceleration time history were shown to be ine.ignifican For the study of ARS inside the drywell TVA used a refined multi-stick lumped-m:ss model which included the recctor building structure, drywell, bio-logical shield wall pedestal, and reactor pressure vessel. Damping values and time history analysis technique fourd acceptable to the staff were used to generate both horizontal and vertical ARS. The comparison of the two sets of corresponding vertical ARS showed that the spectral accelerations in the fre-ra quency(e.nge cases between 20 Hz to 50 Hz calculated based on 50 Hz cutoff at 20 Hz. As for the horizontal ARS, TVA concluded and the staff agreed that there is no need to have a similar comparison as done for the vertical ARS tecause TVA demonstrated that the horizontal analysis based on the 20 Hz building frequency cutoff has already included the cumulative modal mass up to 90% of the total mass as required by the Standard Review Plan (SRP). To assess the impact of the difference identified in the vertical ARS comparison,

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i s TVA selected a sample piping systim attached at locations where the comparison showed significant differences and m.alyzed the system considering the dynamic modes'.up to 50 Hz.- The effects of these differences to the overall subsystem responses were found to be relatively smal The details of- the sample analyses for piping inside and outside drywell are-discussed further in Section 3.2.2 belo .2.2 Sample Piping Analysis 0 'The significance of TVA's ZPA definition, was evaluated by Stone and Webster Engineering Corporation (SWEC) in TVA Calculation CD-Q0999-686698, Revision 1 dated Janaary 25, 1989. The calculation included three sample analyses of piping systen.s outside drywell in the reactor building. . According to SWEC, these problems were selected to represent piping systems at elevations within the reactor building where the' maximum differences between the spectral accel-

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erstion at the cutoff frequency, 20 Hz, and the peak floor acceleration time history (ZPA definition) occurred. The problems were analyzed by two method The first method involved a time history analysis using a 20 Hz cutoff fre-quency and the ZPA, as defined by TVA, summed by SRSS. The second method involved a time history analysis using a cutoff frequency of 50 HZ with the ZPA sumed by SRSS. The results.of these analyses weire compared for each proble The comparison showed that in most cases the support loads were within 10t.

[E In some casas, the support loads for the 20 Hz cutoff case were higher than the 50 Hz cutoff case. In one case, the 50Hz cutoff case showed a component of an anchor load 24% higher than the 20 Hz case. However, this load component wes small compared to the other components of the anchor load and was not significant in the overell anchor design. Based on the results of these studies, it was concluded that.TVA's definition of the IPA was adequate for the piping analyses inside drywel For ARS inside the drywell, the most significant differences between TVA's IPA definition and the actual spectral accelerations above 20 Hz occurred at the shield wall. To evaluate the ARS at locations on the shield wall, one piping I problem was evaluated using the same two methods discussed above. The piping problem selected (problem N1-275-4RA) was considered to represent the worst case piping problem inside the drywell in terms of spectral accelerations of the vertical ARS above 20 Hz. This evaluation resulted in lower support loads for the analysis using 50 Hz as a cutoff frequency. According to SWEC, this was a result of the modal combinations having opposite signs in the 20-50 Hz frequency range of the ARS. Although this result may be attributed to the piping geometry, this sample evaluation was considered adequate to represent piping systems inside the drywell because the ARS plots show that the differ-ences in the spectral accelerations between 20 and 50 Hz at the elevations of the remaining piping system attachments are relatively insignificant. The staff considers this item closed. (CSG-23) \ l; -3- l

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3.3 (3.4.2) Allowable Stress For Aluminum Conduit As described in the staff's Safety Evaluation (SE) of the seismic design pro-gram interim criteria lated July 26,1980 (Reference 5.3), TVA proposed to use 2.0 Fy/(0.75 x 2.3) as the interim allowable bending stress for aluminum con-duit evaluatfun at BFH-2. This allowable stress was not consistent with the allowable stress used for the Sequoyah Nuclear Plant aluminum conduit restart evaluation, i.e., 1.0 Fy/(0.75 x 2.3).

Subsequently, TVA proposed to use 1.16 Fy for the conduit allowable stress and 2.0 Fy/(0.75 x 2.3) for the allowable stress at locations with threaded coup-lings connecting two pieces of aluminum conduit. The staff and its consultant reviewe* TVA's justification for using the proposed allowable values including some test data. The staff concluded that the use of 1.16 Fy as an allowable i stress for conduit at locations without couplings was acceptable. However, 1.16 Fy/(0.75 x 2.3) as an allowable stress at locations with couplings is required. TVA agreed to select the worst case conduit samples based on the existing analysis results and evaluate these sample conduit systems using the allowables defined by the staff. The eva bation results will be reviewed by the staff at the next inspection of the BFN seismic design program. This item remains ope (CSG-26) ..- 4.0 CONCLUSION As discussed in Section 3.0 of this Inspection Report, two out of three items reviewed during this inspection are considered closed. For the remaining l open item, (i.e., allowable stress for aluminum conduit), TVA agreed to com/ ete its sample evaluations, based on the allowables accepted by the staff, by the next inspectio .0 REFERENCES 5.1 NRC Inspection Report 50-260/88-38, dated April 19, 198 .2 NRC Inspection Report 50-260/88-39, dated June 14, 198 .3 Letter from S. Black (NRC) to S. A. White (TVA), " Interim Operability Criteria for the Seismic Design Program for the Browns Ferry Nuclear Plant, Unit 2," dated July 26, 198 (, .

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ENCLOSURE 1 t, BFN CIVIL / SEISMIC OPEN ISSUES CIVIL / STRUCTURAL ITEMS

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  " TECHNICAL MEETING - JANUARY 23-24, 1989

' CHERRY HILL, NEW JERSEY TVA-BFN Site Licensing W.-A. Massie TVA/ Chief Civil Engineer

 'J. McCall   SWEC Alan Chan   NRC/TVA Projects Tom Chen NRC Consultant Ahmet Unsal J. R. Rupert   TVA/ Civil Structural R. D. Cutsinger  TVA/ Civil Structural J. J. Hughes   TVA/CEB Knoxville TVA/ Coordinating H. R. Gavankar
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ENCLOSURE 2 STATUS OF SEISMIC DESIGN PROGRAM OPEN ITEMS Inspection Inspection Inspection Report Report Report 50-260/88-38 50-260/88-39 50-260/89-21 CSG-1 (Closed) Review of IEB ~79-14 Program . Comparison of New ARS end 3. .1 CSG-2 (Closed) Original Design ARS Damping Values for Steel 3.5.2- ' CSG-3.(Closed) Structural Mem W s Inside Drywe11 Soil Amplification Factors 3. .3 CSG-4'-(Closed) for Soil-Supported Strsttures Soil Spring Constants for 3. .4 CSG-5_ (Closed) Soil-Supported Structures Coupling of Horizontal and 3. .5 CSG-6 (Closed) Vertical. Responses of Soil-Supported Structures CSG-7 (0 pen) Design Criteria and Percent 3. of Work Completed CSG-8 (0 pen) Clarification of Design 3. Criteria Used CSG-9 (0 pen) Impact of New ARS 3. .6 CSG-10(0 pen) Assumption of Rigid Lower 3. Platforms in the Horizontal Direction CSG-11(0 pen) Equivalent Static Analysis 3. of Drywell Platforms CSG-12(0 pen) Damping Values for Platform 3. Evaluation Thernal Effects on Drywell 3. .1

.CSG-14(Closed)

Platforms CSG-15(0 pen) Load Interface 3. _ _ - - _ _ _ _ _ _ _ _ _ _ _ - _ _ - = _ _ _ _ _ -

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. Inspection Inspection Inspection Report Report Report 50-260/88-38 50-260/88-39 50-260/89-21

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Percentage of Mass Participa- 3. .7 CSG-16(Closed) tion in the Vertical Seismic Analysis CSG-17(Closed) End Moments on Platform 3. Radial Beams CSG-18(0 pen) Evaluation of Embedment Plate 3. Anchors of Radial Beams CSG-19(0 pen) Platform Clip Angie Criteria 3. CSG-20(0 pen) List of Beam Modifications _

    ,3. CSG-21(Closed) Superseded Pages of Platfom 3. Design Calcu',ation
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CSG-22(0 pen) Design Criteria BFN-50-C-7100 through 7300 Definition of Zero Period 3. .8 CSG-23(Closed) Acceleration (ZPA)ofNewARS CSG-24(0 pen) Buckling of HVAC Ductwork 3. CSG-25(0 pen) Suckling of Aluminum Conduit 3. CSG-26(0 pen) Allowable Stress for Aluminum 3. .3 Conduit CSG-27(0 pen) Flexible Conduit Program CSG-28(0 pen) Use of Factor "1.33" to 3.2.10 Increase Stress Allowable CSG-29 (0 pen) Modeling of HVAC Supports 3. CSG-30(Closed) Welding A110wab1rs for HVAC 3. Supports CSG-31 (0 pen) Buckling of Conduit Rod 3. Supports CSG-32 (0 pen) Evaluation of Support Rod 3. Hangers CSG-33(0 pen) Evaluation of Conduit Supports 3. _ _ - _ _ _ _ _ _ - _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ - - -

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