ML20198S114

Forwards Open Items Associated W/Chapter 3.7.2,3.8.2,3.8.3 & 3.8.4 of AP600 SER

ML20198S114
Person / Time
Site:	05200003
Issue date:	12/09/1997
From:	Joseph Sebrosky NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9801260075
Download: ML20198S114 (15)

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December (9,ik997. i 1+, 4,

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Mr. Nicholas J. uperulo, "---- - .

Nuclear Safety and Regulatory AnrWs; .

Nuclear and Advanced Technology Division "

. Westinghouse Electric Corporation P.O. Box 355 '  ;

Pittsburgh, PAL 15230

SUBJECT:

OPEN ITEMS ASOCIATED WITH CHAPTER 3.7.2,3.8.2/ 3.8.3, AND 3.8.4 OF :

THE AP600 SAFETY EVALUATION REPORT (SER):

Dear Mr. Liparulo ,

The Civil Engineering and Goosbiences Branch (ECGB) of the Division of Engineering has . ,,

provided an SER for Chapter 3.7.2, 3.8.2,3.8.3, and 3.8.4. However, the SER contained some open items. These open items have been extracted from the SER and can be found in the -

. m onclosure to this letter.

You have requested that portions of the information submitted in the June 1992, application for

design certification be exempt from mandatory public disclosure. .While the staff has not completed its review of your request in accordance with the requirements of 10 CFR 2.790, that-portion of the submitted information is being withheld from public disclosure pending the staff's. ,

' final determination.c The staff concludes that these follow on questions do not contain those portions of the information for which exemption is sought. However, the staff will withhold this '

' letter from public disclosure for 30 calendar' days from the date of this letter to' allow Wes:ing-house the opportunity to verify the staffs conclusions, if, after that time, you do not request that -

all or portions of the information in the enclosures be withheld from public disclosure in accor. -

- dance with 10 CFR 2.790, this letter will be placed in the Nuclear Regulatory Commission Public i Document Room.

If you have any questions regarding this matter, you may contact me at (301) 415-1132.

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• Sincerely, -

original' signed by:

Joseph M. Sobrosky, Project Manager Standardization Project Directorate L . Division of Reactor Program Management E , 4 Office of Nuclear Reactor Regulation Docket No. 52-0031

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DISTRIBUTION.

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Mr. Nicholas J. Liparulo Docket No 52-003 Westinghouse Electric Corporation AP600 cc: Mr. B. A. McIntyre Ms. Cindy L. Haag Advanced Plant Safety & Licensing Advanced Plant Safety & Licensing Westinghouse Electric Corporation Westinghouse Electric Corporation Energy Systems Business Unit Energy Systems Business Unit P.O. Box 355 Box 355 Pittsburgh, PA 15230 Pittsburgh, PA 15230 Enclosure to be distributed to the following addressees after the result of the proprietary evaluation is received from Westinghouse:

Mr. Russ Bell Ms. Lynn Connor Senior Project Manager, Programs DOC-Search Associates Nuclear Energy Institute Post Office Box 34 1776 l Street, NW Cabin John, MD 20818 Suite 300 Washington, DC 20006-3706 Mr. Robert H. Buchholz GE Nuclear Energy Dr. Craig D. Sawyer, Manager 175 Curtner Avenue, MC 781 Advanced Reactor Programs San Jose, CA 95125 Gh Nuclear Energy 175 Curtner Avenue, MC 754 Mr. Sterling Franks San Jose, CA 95125 U.S. Department of Energy NE 50 Barton Z. Cowan Esq. 19901 Germantown Road Eckert Seamans Cherin & Mellott Germantown, MD 20874 600 Grant Street 42nd Floor Pittsburgh, PA 15219 Mr. Charles Thompson, Nuclear Engineer AP600 Certification Mr. Frank A. Ross NE 50 U.S. Department of Energy, NE-42 19901 Germantown Road Office of LWR Safety and Technology Germantown, MD 20874 19901 Germantown Road Germantown, MD 20874 Mr. Ed Rodwell, Manager PWR Design Certification Electric Power Research Institute 3412 Hillview Avenue Pelo Alto, CA 94303

$ , .S DISTRIBUTION: Letter to Mr. Nicholas J. Lloarulo. dated: December 9,1997

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Open items Associated with Chapters 3.7.2,3.8.2,3.8.3, and 3.8.4 Open item 220.112F from section 3.7.2.3

- In its letter dated January 26, igg 4, the staff raised a concem regarding the possibility of the out-of-phase interaction between the shield building, the steel containment vessel, and the '

containment air baffle. As a result of the staff's review of the su5mittal dated April 14, igg 4 and the discussion during the review meetings, Westinghouse agreed to provide, in the SSAR, (1) figures showing the rigid link connectivity of the stick model to the foundation met and the wall elements below grade, and (2) the criteria used to establish relative displacements between the

shield buhding and the steel containment vessel for the design of the air baffle. The staff identified this concem as Open item 3.7.2.3 6.

In response to this open item, Westinghouse showed the rigid link connectivity of the stick model to the foundation mat and wall elements below grade in Revision 7 of SSAR Figure 3.7.213 and provide a vertical sliding plate, as described in Revision 7 of SSAR Section 3.8.4.1.3, to accommodate the differential movement between the containment vessel and the shield building.

However, in SSAR Section 3.8.4.1.3 and Figure 3.8.4-1, Westinghouse did not show the size of the sliding plate to ensure that the displacement due to seismic will not affect the integrity of the ,

, air baffle. Therefore, Westinghouse's SSAR commitment does not satisfy this staff concem and

Open item 3.7.2.3-6 remains unresolved.

Open item 220.113F from section 3.7.2.4 .

in the seismic design of the PCCWS tank, Westinghouse assumed that the tank roof slab is rigid and the out of plane flexibility of the slab was not considered. The staff's review of Westinghouse's Calculation No.1070 S3R 010 found that the out of plane frequency of the modified roof slab is around 14 Hz which is not in the rigid range. According to the vertical floor responss spectrum at the tank roof, the out-of-plane design seismic load should increase by 30 to 40 percent. This finding implies that the assumption of a rigid tank roof slab and the existing design of the roof slab are not acceptable, Westinghouse should consider the out of plane flexibility of the slab in the design.

Open item 220.114F from section 3.7.2.4 From the results of its updated SASSI analysis, Westinghouse stated in the draft Revision 17 of SSAR Section 3.7.2.6 that the results of this analysis confirm the adequacy of the seismic

responses and the floor response spectra with the exception of the vertical response spectra for the shield building roof which is affected by the additional water mass. Based on this statement, Westinghouse decided to revise SSAR Figures 3.7.2-4 and 3.7.215 (Sheet g of g) but not the design information documented in SSAR Tables 3.7.2-1 through 3.7.2-12. This is not acceptable based on the discussion above. Westinghouse should either replace the existing results by those from the new analysis or provide new tables to document these new results in the SSAR.

4 Open item 220.118F from section 3.7.2.5

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As described in early revisions of the SSAR, floor response spectra at various elevations and locations of the Ni structures were first generated for each of the three selected site conditions:

E hard rock site with fixed base time domain modal time-history analysis (BSAP analysis), soft rock

site with frequency-domain time history analysis (SASSI analysis), and soft to-medium stiff soil:

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J 2-with frequenq44 T,mia time history analysis (SASSI analysis). Then, these floor response spectre were enveloped, peak-broadened by plus and minus fifteen percent (115 percent), and

.. smoothed to develop a set of design in structure spectrum envelopes in accordance with

. RG 1.122. A set of 3D structural stick models (models for the steel containment vessel, the

, containment intomal structures, and the combine ( shield and auxikary buildings) combined with .

. the support foundation met were used for these analyses. The effects of the spatial combination y '

of three components of the earthquake ground motion time history were considered in the .

i analysis. As such, the coupling effects have been accounted for. The stafl's evaluation of the ,

adequacy of the approach for combining responses attributable to three components of the input -

ground motion is discussed in Section 3.7.2.6. Based on the staff's review of the SSAR, the '

review of Westinghouse's November 30,1992, March 24,1994, and May 11,1994 submittal, and the discussions during the review meetings, the staff concludes that the methods used for the

- development of in-structure response spectra at different locations and the in-structure response spectrum envelopes are in conformance to the guideline of Section 3.7.2.ll.5 of the SRP and RG 1.122, except that the issues related to the combined effects of insufficient participating mass, number of design site conditions, low cut off frequency, norkconformance of 60 percent

, lim:tation of surface ground motion at foundation level, concrete cracking, and other SSI issues discussed above need to be resolved. This was Open item 3.7.2.51.

I The concems of this open Nem are also addressed in Sections 3.7.2.3 and 3.7.2,4 of this report.

On the basis of the resolution for Open items 3.7.2.21 (cut off frequency for seismic analyses),

3.7.2.3-5 (conformance of RG 1.122),3.7.2.4-12 (number of design site conditions) and 3.7.2.4-1 (60 percent limitation of the ground motion at the foundation in the free field), and other open

items related to SSI concoms, the technical concem of Open item 3.7.2.51 is considered resolved. However, because technicalissues were identified from the review of Westinghouse's seismic reanalysis as described in Section 3.7.2.4 of this report, Open item 3,7.2.5-1 will not be closed until Westinghouse resolves these issues.

Open item 220.118F from section 3.7.2.8 Westinghouse was requested to provide the basis for classifying the single story portion of the Radweste Building as noreseismic and the high bay area of the Radweste Building as SC-II. The o staff identified the concem of the seismic design of the redwaste building as Open ltem 3.7.2.8-3.

in Revision 9 of SSAR Section 3.7.2.8, Westinghouse stated that the radweste building is classified as nonseismic and is designed to the seismic requirements of the UBC Zone 2A with an importance factor of 1.25, However, Westinghouse did not make a commitment that the

collapse of this building will not impa!r the safety function of the NI structures, i .

In Revision 12 of SSAR Section 3.7.2.8, Westinghouse, based on the energy balance theory, provided the analysis procedures which are to be used for demonstrating that the collapse of the redweste building will not cause any damage of the Ni structures. Because the application of energy balance for checking potential damages of structures is consistent with the industry .

L practice, it is acceptable to the staff. Also, in the August 11 through 15,1997 meeting, the staff L reviewed the final calculation (Calculation No. 5000-S2C-002) and found that the analysis procedure described in the SSAR was property applied in the evaluation of the impact between

- the Ni and the radweste building and that the impact from the radwaste building in the event of an SSE would not impair the integrity of the Nl. This is acceptable to the staff regarding the

- potentialinteraction between the radweste building and the Nl structures. However,

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3 Westinghouse revised its commitment and stated in Revision 17 of SSAR Section 3.7.2.8.2 that the redweste buildmg is designed to the seismic requirements of USC, Zone 2A with an importance factor of 1.0. Also, the design of this building is based on the assumption that the 4

building will collapse under an SSE. However, a collapse of the redweste building has a potential to spill or release redweste and cause personnel exposure.- Consequently, a reasonable assurance is needed to ensure that this buildmg will not collapse at a level of earthquake less than the SSE. Such a design would be consistent with a design based on UE?,

Zone 3 requirements as used for the design of the turbine building by Westinghouse. The staft

- previously accepted these crtteria for other advanood reactors. On this basis, Westinghouse's response to Open item 3.7.2.8 3 is not acceptable.

Open llem 220.117F from aeotion 3.7.2.8 i if Category ll structures are designed using load factors and allowable stresses as discussed, the .

stress level can exceed yield stress (for AISC) or load demand can be equal to the ultimate load j i capacity (for concrete sections), in such a case, Westinghouse should demonstrate that the SC-il structures, designed using the load factor method and allowable stresses in accordance with AISC with a 60 percent increase permitted for the SSE, will not collapse during an SSE or these structures possess enough margin (ductility reserve) to prevent collapse. However, Westinghouse did not indicate that any such design evaluation has been performed. This was  ;

Open item 3.7.2.6 4. .

In Revision g of SSAR Section 3.7.2, Westinghouse stated that SC-Il building structures are j l designed for the SSE using the same methods as are used for SC-l structures. The acceptance i criteria are based on' ACI 34g Code for concrete structures and on AISC N6g0 for steel structures )

including the supplemental requirements described in Sections 3.8.4.4.1 and 3.8.4.5 of the SSAR.' However, Westinghouse should commit in the SSAR that the same design allowables specified in ACI 34g Code and AISC N6go Standard used for the seismic Category I structures will be used for the design of seismic Category ll structures. Therefore, Westinghouse's g response to open item 3.7.2.8 4 is not acceptable.

Open item 220.118F from section 3.7.2.18 L

l The seismic design basis earthquake for the AP600 structures, systems and components are

. essentially defined at the plant grade level in the free field by an SSE with the peak acceleration of 0.3g and the ground response spectra shown in SSAR Figures 3.7.1-1 and 3.7.1-2, The l seicmic des!gn of the NI (structuras, system and components) is based on the enveloped results .I

! from a limited number of site conditions (soft-to-medium stiff soil site, upper bound of the soft-to- ,

medium stiff soil site, soft rock site and hard rock site), it is the staff's concem that if these I design bases are not satisfied (e.g., the site condition is not within the range of site conditions committed in the SSAR) or if the seismic analysis response envelope used for the design can not .

envelop the results obtained from snms potential plant site conditions not included in the three site conditions stated above, the basis established for the design certifx:ation will no longer apply. In its letter dated March 16, igg 4, the staff requested Westinghouse to commit in the SSAR that the COL applicant should perform an analysis and evaluation using the design basis earthquake ground motion and plant specific site conditions to confirm the design adequacy of - ,

the AP600 design. This was COL Action item 3.7.2.16-1 and Open item 3.7.2.16-1.

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4 During the August 11 through 15,1997 meeting end the early review meetings, the staff reviewed the seismic analysis summary report for each of the four s;te condition and the seismic analysis summary report of the updated model, and found that the SSAR commitments for the seismic analysis of the Ni structures have been property implemented. On this basis, the staff concludes that for the reconciliation analysis by the COL applicant for sites with site parameters within the bound of those specified in SSAR Table 21 is not necessary. However, Westinghouse should commit in the SSAR that these seismic analysis summary reports are available for the future use. For sites with site parameters outside the bound of those described in SSAR Table 21, Westinghouse committed in SSAR Section 2.5.2.2 that site-specific SSI analyses must be performed by the COL applicant to demonstrate acceptability of sites that seismic and soil characteristics outside the site parameters in SSAR Table 2-1. Based on the discussion above, the technical concem of this issue is resolved. Open item 3.7.2.16-1 will not be closed until Westinghouse commits in the SSAR that the above mentioned seismic analysis summary reports are available for the future use, in addition, it should be noted that the design of the Ni structures using the site conditions outside the site parameters specified in SSAR Table 21, the standard design approval by the staff will not apply.

Open item 220.119F from section 3.8.2.4 The staff's review experience with other nuclear power plants suggests that high local stresses may occur in the vicinity of concentrated masses or discontinuities (such as the equipment hatches and personnel airlocks). Consequently, the staff requested that Westinghouse demonstrate that stresses in the vicinity of the concentrated masses calculated based on an equivalent static analysis bound the local stresses computed in the dynamic analysis. The staff identified this issue as Open item 3.8.2.4-3.

During the meeting on August 30 and 31,1995, Westinghouse stated that detailed analyses and the design of the containment vesselin the vicinity of concentrated masses are beyond the

, scope of the AP600 standard design. However, Westinghouse agreed to modify the SSAR to provide the analysis procedures. Revis;on 11 of SSAR Section 3.8.2.4.1.2 fulfills that commitment by providing the following information:

a detailed description of the methods to be used for the dynamic analysis of local masses e

the approach for analyzing the local buckling potential of the containment shell adjacent to major penetrations

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the criteria for redistributing the stress to be applied to the shell adjacent to local masses

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methc,ds for evaluating the compressive strength of the containment shellin the vicinity of major penetrations After reviewir.g this new information, the staff concludes that the analysis procedures provided in the SSAR are sufficiently detailed for the future design of containment vessel elements adjacent to concentrated masses. However, Westinghouse should commit in the SSAR that the design of containment vessel elements adjacent to concentrated masses is an action item for the COL applicant. Therefore, Open item 3.8.2.4-3 remains unresolved.

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Open itsm 220.120F from sootion 3.4.2.8 As stated in early revisions of SSAR Section 3.8.2.5, the containment vessells designed,-

fabricated, installed, and testsd socording to the requirements of ASME Code, Section lil, Subsection NE. The stress intensity limits are accolling to the ASME Code, Sechon lil, Paragraph NE 3221 and Table NE 3221 1 Critical buckling stresses are checked according to the provisions of ASME Code, Section lil, Paragraph NE-3222 or Code Case N 284, Revision 0.

The use of ASME Code, Section 111, Subsection NE for evaluating the potential buckhng of the AP600 ocntainmord vessel meets the guideline prescribed in Section 3.8.2.ll.5 of the SRP, in addition, during the staffs review of the System 80+ design, the criteria in ASME Code Case

' N 284, Revision 0, were previously found acceptable for evaluating containment shell buckling.

On this basis, the structural criteria to which Westinghouse committed in earty revisions of SSAR ,

Section 3.8.2.5 are acceptable.  !

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' However, in Revision 7 of SSAR Section 3.8.2,4.1.1, Westinghouse proposed to use Revision 1  !

of ASME Code Case N 284 for the evaluation of containment shell buckling. On February 12, j 1996, in response to the staffs request, Westinghouse submitted a comparison of Revisions 0 and 1 of Code Case N-284, including its evaluation of the differences between the two revisions. 1 The staff reviewed Revision 1 of ASME Code Case N-284 along with the submittal dated i February 12,1996, and identified a number of errors and typographical errors in Revision 1 of '

this code case. In its letter dated November 26,1gg6, and during the meeting on August 11 through 15,19g7, the staff indicated that the use of Revision 1 of ASME Code Case N-284 is not acceptable for the evaluation of containment shell buckling.

In Revision 17 of SSAR Section 3.8.2 and Appendix 3G to the SSAR (Revision 17),

Westinghouse provided criteria for evaluating the local buckling of the AP600 steel containment  !

vessel components such as the ellipsoidal head, cylindrical shell, and equipment hatch covers. I These criteria are based on the rules specified in ASME Code Case N-284, Revision 0 with

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supplemental requirements which are not provided in Revision 0. The supplemental '

L requirements revised some equations (3G.5.2.2, 3G.6.1.1.a. 3G.6.1.1.b, 3G.6.1.3.b, 3G.6.2.1.b, .

and 3G. 6.2.1.c) and added new equations (3G.3.2.1, 3G.3.2.3, 3G.4.1, 3G.4.1.1, 3G.4.1.2, and '

3G.4.1.3). However, Westinghouse did not provide any basis to demonstrate that the i

supplementa! requirements is applicable for evaluating the potential buckling of containment vessel components. On the basis discussed above, the staff concludes that this issue will not be resolved until Westinghouse submits a justifiable basis for the staff review.

Open item 220.121F from section 3.8.3.4

! The equation for bending stiffness is valid only if the steel and concrete truly behave as a composite section. Thus, because the original module design did not include any shear studs to bind together the steel plates and concrete, the staN asserted that Westinghoure needed to demonstrate the adequacy of the design based on the assumption of a composite section. The staff identified this requirement as Open item 3.8.3.4-3.

in Revision 7 of the SSAR, Westinghouse modified the configuration and design approach'for the concrete-filled well modules Specifically, the diaphragm plates, which previously connected the two faceplates, were replaced with steel trusses. In addition, the horizontal angles welded to the

= steel faceplates were replaced by a pattom of steel shear studs. (These shear studs were intended to connect the steel faceplates to the concrete fill, thereby creating composite action of l.

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6 j the steel plates and conorete.) This modified design approach treated the faceptates as reinforcing steel, and utilized ACI 349 as the basis for the wall design. This approach is backed-1 up by a series of tests performed in Japan and has been common practice in the industry, and therefore is acceptable, provided that the pattern / location and design of the studs is properly performed. Mcnm, in reviewing the sampled design calculations for the studs during the meeting on January 14 to 16,1997, the staff found that Westinghouse failed to demonstrate the adequacy of the stud design crMoria, which are needed to an ensure composite action.

Westinghouse addressed the staffs concems related to the design crMeria for the shear studs in

] Its letter dated April 10,1997. Specifically, that letter described the method used to design the shear studs, which is based on the requirements of ANSI /AISC N690 for composite construction i with concrete slabs on steel beams. The crHeria used in ANSI /AISC N690 for full composite ,

behavior is that the strength of the shear connectors over the length of the beam from the point of maximum moment to the point of zero moment is greater than the yield strength of the steel beam. This letter also described the approach for considering in-plane loadings which need to be transferred between the steel faceplates and the concrete core.

During the meeting at Westinghouse on April 14 through 18,1997, The steff raised a concem that the design method described in the submittal dated April 10,19g7, did not consider the  ;

simultaneous application of in plane and riut-of-plane loads acting on the shear studs. To address this concem, Westinghouse presented preliminary design calculations for review, during i

the review meeting on April 14 through 18,1997. In these calculations, Westinghouse expanded its design method for the shear studs by considering in-plane and out-of plane loads applied simultaneously. Westinghouse also demonstrated that, for the design of carbon steel faceplates, i the existing design of shear studs meets the limits allowed by code. However, for the stainless I steel faceplates used for the modules in contact with water, the staff noted that Westinghouse needed to consider the combined action of shear studs and the attached steel angles to meet the cocr diowable.

Nonob m, because the shear stud design approach described above follows ANSI /AISC N690 criteria and considers the simultaneous application of the other in-plane and out of plane loads, the staff found the design method acceptable, with the exception that Westinghouse needed to finalize the calculation for the staff review. Also, Westinghouse needed to modify the calculation L for the studs attached to the stainless steel plates so that H would consider a concrete strength of 27.58 MPa (4,000 psi) instead of 34.47 MPa (5,000 psi) (to determine the angle capacity), in addition, Westinghouse needed to modify the SSAR description of the trusses to reflect that the trusses are also used to develop shear load transfer between the steel faceplates and the i

concrete core. Given those modification of design calculations, this open item is considered technically resolved. However, Open item 3.8.3,4 3 will not be closed until Westinghouse

j. submits the final design calculations and the revised SSAR for the staff review.

Open item 220.122F from section 3.8.3.4 i

As stated in the SRP, the staff should review a design report in order to obtain design and construction information that is more specific than that contained in the SSAR. The design report can also assist the staff in planning and conducting a structural review. Nonetheless, Westinghouse was unable to provide a design report for the containment intemal structures L during previous review meetings. Thus, in the submittal dated June 30,1994, Westinghouse L

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7 committed to compile design summary reports using the format and attril utes described in Appendix C to Section 3.8.4 of the SRP. In addition, these design summary reports would incorporate the criteria acceptable to the staff and would be made available for staff review. This commitment was identlRed as Open item 3.8.3.4-12.

d Dudng the meeting on January 14 through 16,1997, the staff reviewed samples of the draft design summary reports for the structural modules, including " Design Summary Report - -

Containment intomal Structures," No.1100 83R-001 (Draft), dated January 1997; and Design  !

Summary Report - Auxiliary Building Structures," P.1200 83R-001, Revision 0 (Draft), dated ,

January 1997. These draft summary reports dese.oed the components of the structural modules, structuralloads, structural analysis and design, and results. Because the information included in the design summary reports is sufficiently detailed and the scope of these reports is in accordance with that described in Appendix C to Section 3.8.4 of the SRP, this issue is '

considered technically resolved.

In comp!:,g its response to this concem, Westinghouse presented two design reports for the staff's review duilng the meeting on April 14 through 18,19g7. However, neither of these reports was finalizedi Weslinghouse indicated that further information will be added to ti,e design reports, such as the drawing details for the critical structural well modules, stress / load / required steel area summary tables for the critical wall sections, and the comparison tables for the ADS pressure loading analyses. Open item 3.8.3.412 will not be closed until Westinghouse finalizes these design summary reports.

Open item 220.123F from section 3.8.3.4 A structural design review is also required for the containment intomal structures, particularly because of their unique design details and modular construction techniques. The objectives of >

the review are threefold. First, the staff willinvestigate the manner in which the structural design criteria were implemented. Second, the staff will attempt to verify that the key structural design

!. calculations have been performed in an acceptable way. Finally, the staff will identify and assess the safety significance of particular areas where the containment intemal structures were designed and analyzed using methods not covered by the SRP guidelines. Thus, the need for a structural design review was identified as Open item 3.8.3.4-13.'

During the meeting on January 14 through 16,19g7, the staff reviewed samples of design calculations for the structural modules. In general, these calculations and analyses did adhere to the commitments stated in the SSAR. However, the implemer.tation details were sometimes

- difficult to follow, severalinconsistencies were noted, and several reports did not appear to be final, in addition, Westinghouse needed to justify or revise the calculation regarding the shear

studs (see the discussion concoming Open item 3.8.3.4-3), and needed to finalize design calculations for the evaluation of AOG toads.

, _ in addressing the concems descr#aed above, Westinghouse presented its final design  ;

calculations for structural modules during the meeting on April 14 through 18,19g7. The staff then reviewed the following sample s of design calculations:

L r Calculation No.1100-EUC-101, Revision 2, " Structural Wall Modules - Containment

Intemal Structures" i

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Calculation No,1200 SUC-101, Revision 2, " Structural Module in Arecs 5 and 6 i Auxiliary Building"

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135.25' Containment intomal Strudures" Calculation No. MT03 83C 012 and 018, " Hydrodynamic and Pressure Analysis of IRWST" l Calculation No.1100 8U0A03, Revision 0, " Structural Modules - Design of Shear Studs" l

As a result of its review, the staff found that Weri.Aouse's design procedures specified in the j 2

' 88AR were not property implemented in the design calcu'stions. Thus, the staff requested that '

. Westinghouse conduct its own review of design calculations and finalize these design calculations for the staff review. Open item 3.8.3.413 remains unresolved.

Open item 220.124F from section 3.8.4.4 1 in reviewing earty design ' calculations, the staff found that the final design calculations for the

, shield building and the PCCWS tank was not available for review. The staff identified this

omission as Open item 3.8.4.4-2.

I . During meetings conducted in late 1995 and early igg 6, the staff reviewed analysis methods and models used for the design of these two strr,ctures, and raised three concems that

Westinghouse needed to address

(1) The vertical component of the earthquake ground motion tends to increase (add to) the I water pressure against the PCCWS tank walls. Westinghouse should consider this ,

pressure in designing the outer tank wall and the connection between the tank wall and the '

conical roof. However, during discussions with Westinghouse, the staff was informed that the design forces for the outer tank wall are very low. - Westinghouse should demonstrate and justify the adequacy of these design loads.

(2) Because the conical shell has a relatively shallow slope (35 degrees), a high horizontal i component of the in-plane seismic force in the conical shell (caused by vertical excitation of the tank under an SSE) should be expected to apply at the top of the tension ring beam

' - which supports the conical shell. This horizontal force will (a) induce high hoop stress and significant cracking of tension ring beam, and (b) produce a torsional moment on the tension ring beam and bending moment at the top of columns supporting the tension ring beam.

Westinghouse should considered these two effects in the tension ring beam design.

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.(3) During construction, the precast panels of the shield building roof are temporarily sup-ported on the containment vessel.- Consequently, Westinghouse calculated the maximum reaction loads applied on the containment vessel dome, but indicated that these maximum reaction loads would be reduced during construction, because of the combination of the following factors: (a) An increasing number of conical roof panels are installed.- (b) The stiffness of the overall structure increases as each panelis erected. Nonetheless, the staff.

concluded that Westinghouse should evaluate the significance of these constructio~n loads (potential of buckling) with regard to the containment vessel dome.

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During the meeting with Westinghouse on December g through 13,1996, the staff reviewed the '

final design calculations for the shield building roof structures (including the PCCWS tank), As a result of that review, the staff found that the assumptions, modeling techniques, and analysis  :

methods were reasonable and met the guidelines prescribed in the SRP Moreover, the analysis >

yielded results comparable to those obtained from the staffs confirmatory analysis, in addition, ,

Westinghouse demonstrated that the construction loads applied on the containment vessel are  ;

-insignificant and will not cause any buckimg of the vessel. However, the torsional moment calculated by Westinghouse for the tension ring beam was much lower than that obtained from the confinnatory analysis. The staff therefore concluded that in order to ensure the design adequacy of this ring beam, Westinghouse should regenerate the torsional moment on the

tension ring beam and upgrade the design as needed.

Early in 1997, Westinghouse revised the PCCWS tank structures as a result of the post 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />

, action requirements. Westinghouse also performed an updated analysis (consistent with the

- modified 3D tank model) to evaluate the impact of the revised shield building roof structures on the overall AP600 design. In the meeting on August 11 through 15,1997, the staff reviewed Westinghouse's final analysis and design calculations. As a result of this review, the staff found that Westinghouse had property incorporated the design changes in the revised model, and the analysis and design met the guideline prescribed in the SRP. Nonetheless, the staff identified the following four technical concems:

(1) The design drawings do not show the vertical reinforcement in both sides of the air inlet columns. The design drawings should also specify the length of these robars.

(2) In Section 3.8.,4,4.1 of the SSAR Westinghouse committed to meet the requirements i defined in Chapter 21 of ACI 318, which state that in order to resist shear forces, stimips

, should be provided with 135 degree hooks at both ends of the robars. However, 4

Westinghouse used double-U bars for the hoop reinforcement (or stirrups) at the air inlet columns, tension ring beam, and compression ring beam. Also, in the air inlet columns, Westinghouse did not extend the shear hoop reinforcement (stirrups) and cross-ties above

and below air inlet openings. The use of double-U bars for the shear reinforcement does not ruet the SSAR commitment.

(3) The staff identified certain inconsistencies between the design drawings and the summary table in Appendix 25 to Calculation No.1277-S3C-0')6, and design deficiencies as follows:

i (a) The design drawing of the conical shell roof at the tension ring beam shows that a bottom radial reinforcement of 45.29 cm2 /m (2.14 in?/ft)is needed at the columns, and a bottom radial reinforcement of 37,66 cm'/m (1.78 in'/ft) over the air inlet.

However, Tat.,e 11.6 of Appendix 11 in calculation No.1277-S3C-006 shows that only one #g robar is provided above the air inlet, and none at the columns. Also,

- the drawing shows the bottom reinforcement discontinued at the end of conical

, roof.

-(b) The conical roof at the compression ring beam shows that an amount of 13.16 2

cm (2.04 in') bottom radial reinforcement is needed. Table 11.6 of Appendix 11 in calculation No.1277-S3C-006 shows no reinforcement provided. Also, the drawing also shows the bottom reinforcement discontinued at the compression ring. .

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8-l (c) The conical shell roof at the intomal PCCWS tank well shows that nine #g robars were provided for the hoop reinforcement at the top and bottom faces. However, ,

the design drawing shows that 18 #g robars were provided, but they are not property distributed at the top and bottom faces, (4) As discussed in Section 3.7.2 above, Westinghouse failed to consider the out-of-plane vibration in the roof slab design.

On the basis discussed above, Westinghouse's design of the shield building roof structures is not acceptable and Open item 3.8.4.4-2 remains unresolved.

Open item 220.128F from sootion 3.8.4.4 Because a massive amount of water is to be contained in the PCCWS tank, the staff raised a concem that the COL applicant should monitor the vertical and radial deformation of the tank during initial filling, and compare the meesured values with the tank deformation predicted by  ;

calculation. The staff identified this issue as Open item 3.8.4.4 3 and COL Action item 3.8.4,4-1. -

At the meeting on June 12 through 16,1995, Westinghouse stated that the water weight is small, in comparison with the total weight of the shield building roof structure (estimated to be about 10 percent). Westinghouse also showed that the deflection of the roof structure resulting from the i- first fill of water should be negligible. On that basis, Wes*inghouse contended that there is no need to monitor the tank deflections and compare the deflections against predictions.

F During the meeting on December g through 13,1996, Westinghouse repeated its justifx:stion concoming this issue. However, the staff did not agree with Westinghouse's basis for not monitoring the vertical and radi31 deformation of the tank during initial tank filling. Moreover, the staff asserted that post construction testing is necessary to confim, the adequacy of the PCCWS

- tank. This is because the staff's review experience suggest that the excessive deformation resulting from the massive amount of water may cause cracking of the tank wall and base stab, as well as water leakage from reinforced concrete tanks with steel liners, in Revision 17 of SSAR Section 3.8.4.1.1, Westinghouse added a statement that leak chase channels are provided over the liner welds to permit monitoring for leakage and to prevent

' degradation of the reinforced concrete wall which might result from the freezing and thawing of leakage. Also, Westinghouse indicated that the exterior face of the reinforced concrete boundary of the PCCWS tank is designed to control cracking, in accordance with Paragraph 10 6.4 of ACl-

! 34g, with reinforcement steel stress based on sustained loads (including thermal effects).

However, Westinghouse still did not commit to monitor the vertical and radial deformation of the tank during initial filling and compare the measured values with the tank deformation predicted by analysis. On the basis of the above discussion, the staff concluded that Westinghouse's response to the sta*f's concem (as stated in Revision 17 of SSAR Section 3.8.4.1.1) is not

acceptable. Therefore, Open item 3.8.4.4-3 and COL Action item 3.8.4.4-1 remain unsolved, i

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Open llem 220.126F from aeotion 3.8.4.4

' As part of design and analysis procedures, Westinghouse should prepare and document design j reports for all SC-l structures, in socordance with the guidelme prescribed in Appendix C to Section 3.8.4 of the SRP, in its submittal dated June 30,19g4, Westinghouse agreed to prepare l a design report for each of the followir,g structures and buildings:

l NI foundation met auxihary bulldog

' containment intomal struc'.ures

- shield building Westinghouse also stated that these design reports will not be included in the SSAR, but will be avs,ilable for NRC audit, and will be updated during construction te incorporate as-procured and as-constructed information. The staff finds that Westinghouse's commitment to prepare the -

design reports for each of the safety-related structures meets the guidelines of Appendix C to Section 3.8.4 of the SRP and, thus, is acceptable. However, the list of components provided in Westinghouse's submittal dated June 30, igg 4, should also include the in containment refueling water storage tank (IRWST) (as part of the containment intomal structures), and (2) the air baffle (as part of shield building). The staff identified this concem as Open item 3.8.4.4-7.

In the meeting on April 25 through 27, igg 5, the staff raised several technical concems perialn-ing to the a!r baffle design. Westinghouse responded by presenting a new preliminary design for the containment air baffle. During the meeting on January 14 through 17,19g7, Westinghouse presented the design calculations for the containment air baffle. After reviewing the new information, the staff found that Westinghouse's design meets the requirements of ANSI /AISC N6go 04 and, therefore, is acceptable. However, Westinghouse's design did not consider the air flow fluctuations and the potential for flow-induced vibration / fatigue failure. In addressing these two technical concems during the meeting on April 14 through 16, igg 7, Westinghouse provided ^

preliminary design information for review. The staff's review of the draft information found that Westinghouse had, in fact, considered the effect of air flow fluctuations and the potential for flow-induced vibration / fatigue failure. On this basis, the staff concluded that the concem regarding the design of the containment air baffle is technically resolved. However, Open item 3.8.4.4-7 will not be closed until Westinghouse submits the final design calculations.

Open item 220.127F from section 3.8.4.4

- In addition to the open items discussed above from section 3.8.4.4, the sisff raised one issue during its review of the AP600 design calculations. Specifically, the SSAR stated that the -

embedded exterior (peripheral) walls of SC-l structures in the AP600 Nl are designed to resist the worst-case lateral earth pressure loads. However, during the design r6 view meetings, the staff found that the soil pressure used for the wall design was much lower than the passive soil pressure used for the Ni sliding analysis. The staff also found that the wall design did not account for the dynamic soil pressure attributable to the structure-to-structure interaction effects from the agacent structures (turbine building, annex buildings, and radweste building). In addi-

. tion, to enhance the resistance to the high shear stress attributable to the extemal earth pressure (both static and dynamic), Westir'ghouse applied heavy shear reinforcement at various locations, such as the junction between walls and the foundation mat. However, with relatively thin. walls (the wall thickness at the junction with the foundation mat is g1.44 cm (3 ft]), the congestion of

- reinforcement at these locations may cause reduction of shear resistance of the walls.

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12- l Westinghouse should consider these concems in the final design of these walls. This issue remains unresolved. I l

Open item 220.124F from section 3.8.4.4.2 Because of the complication of the coupled shield / auxiliary building structures, Westinghouse informed the staff that the completed structural design of this building will not be performed.'

(The five story auxiliary building is structurally connected with the cylindrical shell shield building at six different elevations and formed a coupled structure. The coupled shield / auxiliary building is founded, together with the containment vessel and the containment intomal structures, on a irregular shaped foundation mat.) Instead, the detailed design would be completed only for the crit! cal sections of structures. As described in revision 12 of SSAR Section 3.8.4.5.3, Westinghout,e identified g critical sections for wilch Westinghouse completed its structural design. The staff reviewed samp!es of these critical section designs and raised the following concems:

In reviewing the design calculations for the auxiliary building roof slab at Elevation 180 ft (Calculation Nos.1260-SSC-003, Revision 2, and 1260-CCC-003, Revision 3), the staff identified two issues:

(1) The design did not account for the effect of global out-of-plane seismic moments along the edge of the roof slab.

(2) Reinforcements for the concrete slao in the north-south diiection (parallel to floor steel girders) a!ong the roof edge should be designed assuming no composite action of the concrete slab with the steel girder.

The design of the shield building roof structures is not adequate as discussed under Open item 3.8.4.4-2 above.

Westinghouse should include the detailed design drawing for each of these critical sections in the SSAR.

Westinghouse needs to revise the design calculation to address the staffs concem discussed above and provide figures describing reinforcement details of critical sections in the SSAR.