ML20136G023

Forwards Review of Westinghouse Response to Staff Position Ltrs Dtd 970131 & 0210.Evaluation of Westinghouse Response to NRC Position Ltrs Encl

ML20136G023
Person / Time
Site:	05200003
Issue date:	03/13/1997
From:	Bagchi G NRC (Affiliation Not Assigned)
To:	Quay T NRC (Affiliation Not Assigned)
References
NUDOCS 9703170166
Download: ML20136G023 (8)

Text

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t March 13, 1997 s

MEMORANDUM T0: Theodore R. Quay, Director Standardization Project Directorate Division of Reactor Program Management FROM: GohtamBdhc~h'i,C}Nf Civil Engineering and Geosciences Branch Division of Engineering

SUBJECT:

REVIEW 0F WESTINGH0USE'S RESPONSE TO THE STAFF POSITION LETTERS DATED JANUARY 31 AND FEBRUARY 10, 1997 OD 9

References:

1. Letter from T. R. Quay, NRC to N. J. Liparulo, Westinghouse, "Three Major Issues Resulting from the Civil Engineering and Geosciences Branch (ECGB) Review of the Westinghouse AP600 Advanced Reactor Design," dated November 4, 1996.

2. Letter from T. T. Martin, NRC to N. J. Liparulo, Westinghouse, "AP600 Advanced Reactor Desita site Parameters for Seismic Design and Nuclear Island Foundation Mat Adequacy," dated January 31, 1997.

3. Letter from B. A. McIntyre, WestingMrse to T. R. Quay, NRC, " Site Conditions - Shallow Soil Sites," da'fd January 28, 1996.

4. Letter from B. A. McIntyre, Westinghouse to T. T. Martin, NRC,

" Structural Key Issues," dated February 10, 1997.

The Civil Engineering and Geosciences Branch has completed its review of Westinghouse's responses (References 3 and 4) to the staff position letters (References 1 and 2). Our evaluation report is attached. If you have any questions, please contact Thomas Cheng at 415-2770.

Attachment:

As stated cc: B. W. Sheron Distributiogge ME CENTER @

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NAME TChe[h Gdgch i DATE 3 //O /97

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NUCLEAR REGULATORY COMMISSION i WASHINGTON, D.C. 20656-0001 o% ,,,,./ March 13, 1997 MEMORANDUM T0: Theodore R. Quay, Director Standardization Project Directorate Division of Reactor Progr anageynt FROM: Goutam Bagchi, Chief ,M '

Civil Enginee An nd Geos ences Branch 4

Division of neering

SUBJECT:

REVIEW 0F WESTINGHOUSE'S RESPONSE TO THE STAFF POSITION LETTERS DATED JANUARY 31 AND FEBRUARY 10, 1997

References:

i

1. Letter from T. R. Quay, NRC to N. J. Liparulo, Westinghouse, "Three Major Issues Resulting from the Civil Engineering and Geosciences Branch

(ECGB) Review of the Westinghouse AP600 Advanced Reactor Design," dated November 4, 1996.

2. Letter from T. T. Martin, NRC to N. J. Liparulo, Westinghouse, "AP600 Advanced Reactor Design site Parameters for Seismic Design and Nuclear Island Foundation Mat Adequacy," dated January 31, 1997. l l

3. Letter from B. A. McIntyre, Westinghouse to T. R. Quay, NRC, " Site Conditions - Shallow Soil Sites," dated January 28, 1996.

4. Letter from B. A. McIntyre, Westinghouse to T. T. Martin, NRC,

" Structural Key Issues," dated February 10, 1997.

The Civil Engineering and Geosciences Branch has completed its review of Westinghouse's responses (References 3 and 4) to the staff position letters (References 1 and 2). Our evaluation report is attached. If you have any questions, please contact Thomas Cheng at 415-2770.

Attachment:

As stated cc: B. W. Sheron G. C. Lainas D. Jackson

EVALUATION OF WESTINGHOUSE RESPONSE TO i NRC POSITION LETTERS i

e I. Site Conditions - Shallow Soil Sites k

i By its letters dated January 28,1997, (Reference 3) and February 10, 1997, (Reference 4) Westinghouse responded to the staff's concern regarding the

inclusion of shallow soil sites in the design of AP600 nuclear island (the first issue addressed in the staff November 4, 1996, and January 31, 1997, position letters, References 1 and 2). The staff's evaluations of j Westinghouse's responses are as follows

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, Backaround i for siting the AP600, Westinghouse chose four site conditions that would envelope soil locations for the AP600 standard plant. These four site j conditions are hard rock, soft rock, soft-to-medium soil, and upper bound of 4 soft-to-medium soil. The staff clearly articulated in the DSER that shallow l soil sites are outside the envelope of these four site conditions. In a June j '1995 meeting, Westinghouse agreed to exclude shallow soil sites from the AP600. In order to allow the AP600 nuclear island to be founded on potential i shallow sites, Westinghouse now proposes to allow the COL applicant to perform l

4 site-specific soil-structure interaction analysis based on the site-specific soil condition and site-specific safe shutdown earthquake, and demonstrate the i design adequacy of the standard plant. In doing this, it would allow deviation from the standard design. According to 10 CFR 52.47(a)(1)(1), the application for design certification must contain the technical information that is relevant to the design and is not site-specific. Also, 10 CFR 52.47(a)(1)(iii) requires that the application for design certification contain the site parameters postulated for the design, and an analysis and evaluation of the design in terms of such parameters. On this basis, the staff believes that Westinghouse has misinterpreted the requirements of the regulation. None of the previous two standard design applicants has misinterpreted the 10 CFR Part 52 regulation.

General Comment In order to comprehend the staff's real concern cited in its November 4, 1996 letter, Westinghouse ought to read and understand the whole letter instead of picking out specific sentences and commenting on it. Westinghouse needs to demonstrate that the AP600 standard plant design is in compliance with the full range of site conditions based on its chosen site parameters. At this time, Westinghouse has not demonstrated that its seismic design of the nuclear Attachment 1

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1 l island is valid for shallow soil sites. Therefore, Westin30use should either  !

exclude the shallow soil sites from the AP600 design, or consider the soil  ;

parameters corresponding to the shallow soil sites as a new set of design soil parameters and include them in the AP600 design. To consider the shallow soil

! sites as a COL issue and delay the seismic analysis review and approval does

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not meet the standard design rule of 10 CFR Part 52.47 and is not acceptable.

Soecific Comments

! 1. The staten.ent made in Westinghouse's response letter (Reference 3), that i

the AP600 design as documented in the SSAR satisfies the NRC staff i

i position regarding establishing design capacity, is true only for those sites for which the soil parameters fall inside the range of design soil i

parameters identified in the SSAR. For these sites, Westinghouse i defined the ground motion as shown in SSAR Figures 3.7.1-1 and 3.7.1-2, L and used these ground motion as input to perform seismic analyses and to generate seismic responses (member forces and floor response spectrum envelopes) for the design of the AP600 nuclear island structures, systems and components. These seismic responses which have been reviewed and accepted by the staff were used for the seismic design, and j are to be used by the COL applicants for qualifying site-specific safety

! related items. However, in the case of shallow soil sites, the AP600 i

~ design has not been demonstrated to be adequate for the standard seismic design ground motion as required by the regulation.

2. In its letter (Reference 3), Vestinghouse quoted the staff position that {

" suitability of a future site vould then have to be established by I demonstrating that the seismic demand spectra for the site are lower than the capacity spectra." In response to this staff position,  ;

Westinghouse, in Reference 3, stated that: (1) the suitability of a future site, including any shallow soil site, is established by the COL 1 applicant as described in SSAR Section 2.5, and (2) for sites where the l soil characteristics are outside the range considered in Appendix 2A.2 '

and Appendix 2B.2, site-specific soil-structure interaction analyses may be performed by the COL applicant to demonstrate the acceptability by comparison of floor response spectra at specified key locations. Also in SSAR Section 2.5.4.5.5, Westinghouse stated that these analyses would use the site-specific soil conditions and site-specific safe shutdown earthquake. On this basis, Westinghouse concludes that Westinghouse has complied exactly with the written staff position.

Westinghouse is right within the narrow sense that a comparison of site-specific seismic demand must be enveloped by the standard seismic design capacity. But Westinghouse's response does not recognize that the staff position requires the use of the necessary and sufficient set of design response spectra which established the seismic capacity of the standard design. In this context, a set of sufficient response spectra is necessary in order to meet the provision of the regulation requiring a standard design parameter'(modified Regulatory Guide 1.60 response spectra anchored to 0.3g) for the full range of design site parameters.

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i 3. In response to the statement made in the staff's position letter dated November 4, 1996 (Reference 1), "as with other design acceptance l criteria, the result will be non-standard seismic design for certain j system (e.g. piping)," Reference 3 states that Westinghouse has i established only a single set of in-structure response spectrum envelopes and has designed the systems, buildings and equipment using this envelope. Therefore, site-specific piping design is not required l when the response spectrum envelope is satisfied. Westinghouse is right j in the narrow sense that they do not intend to allow piping design using

! site-specific soil properties. But Westinghouse misses the requirement of the regulation that the standard seismic design capacity must be established through response spectrum envelopes over a full range of j site conditions.

3 As stated in the NRC draft safety evaluation report (DSER) issued in

November 1994 (0 pen Item 3.7.2.4-3), based on its review of the SSAR and related documents, and confirmatory analysis results, it was found that

} Westinghouse's design based on the site conditions committed in the SSAR j are not adequate for shallow soil sites. Therefore, the shallow soil

! sites should be excluded for the AP600 design. Also, during the June 12-16, 1995, meeting,-Westinghouse agreed to exclude shallow soil sites

! -from the AP600 design and to provide basis for excluding the " shallow soil sites" in the SSAR, because the design adequacy of the AP600 could not be demonstrated for these site conditions. From the discussion i above, it is clear that the piping design based on the single set of in-l structure response spectrum envelopes specified in the SSAR will not be j adequate for the AP600. founded on a shallow soil site.

i 4. For the three options provided in its position letter (Reference 1), the staff's comments on Westinghouse's responses are as follows:

a. For sites other than shallow soil sites, the Westinghouse position is that the suitability of the future site would be established-through a comparison of the site specific _ ground response spectrum and the AP600 design response spectra. Again, Westinghouse's proposal to compare the site specific seismic demand with the standard seismic capacity is acceptable only when the standard design parameter is met which was established from a full range of site conditions. Shallow soil sites are outside of the current range of design site conditions,

b. For the second option, Westinghouse responded that the AP600 has not been analyzed specifically for shallow soil sites. There are shallow soil sites where AP600 would not be acceptable. However, there are shallow soil sites where the AP600 could be demonstrated acceptable by site specific analyses and comparison against the floor response spectra at four key locations. As stated in (a) above, Westinghouse *s approach is not acceptable. A necessary and sufficient set of response spectrum envelopes based on a full range of site conditions must be developed to establish the AP600 design capacity.

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c. The staff understands Westinghouse's reason for rejecting this

option.

j II. Desian of Containment Foundation Mat l

Backaround As documented in the SSAR, Westinghouse chose to use a six foot thick mat foundation (117 ft wide and 256 ft long) in the auxiliary building area of the nuclear island. During its review meetings conducted in 1994, the staff identified design errors in the structural calculations. Consequently, Westinghouse incorporated shear reinforcements into the basemat to accommodate the design errors; whereas the original basemat detail had no shear  !

l reinforcements. The staff also identified the need to consider variation of  !

soil stiffness across different parts of the basemat. In addition, Westinghouse did not fully investigate the constructability of such a thin and large basemat; therefore, it became necessary that there be a strict adherence to a detailed geotechnical site investigation and a specific construction sequence.

Evaluation Westinghouse responded to the staff's concern regarding the design adequacy of the AP600 nuclear island foundation mat (the second issue addressed in the November 4, 1996, and January 31, 1997, position letters, References 1 and 2) through. its letter dated February 10, 1997, (Reference 4). In Reference 4,  ;

Westinghouse decided to choose the first option stated in the position letter i dated November 4,1996, (Reference 1) and tried to demonstrate the design j adequacy of the six foot thick foundation mat. Westinghouse's approach is to  :

either demonstrate the foundation mat design can accommodate the effects of soil stiffness variations of hard and soft spots underneath the basemat, or {

1 exclude sites with extreme soil variability by using site interface criteria  ;

during the COL stage.

The approach proposed by Westinghouse for the foundation design is not l

acceptable, because the design of the foundation is not completed based on a i full range of site conditions (certain sites could to be excluded as a result j of the COL site investigation), and a significant amount of work needs to be  ;

done by the COL applicant. In demonstrating the completeness of the AP600 '

design, according to 10 CFR Part 52.47(b)(2)(1)(A)(4) that "the certification of a standard design which ...... will be granted only if the scope of the design is complete except for site-specific elements such as the service water i inbake structure and the ultimate heat sink," Westinghouse should complete the basemat design so that it can be located at sites with a full range of site  !

condition of soil stiffness variability. On this basis, the staff concluded in its January 31, 1997, position letter (Reference 2) that the basemat ,

thickness should be changed to demonstrate its acceptability over a full range '

of soil stiffness variability.

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References

NRC Position Letters:

1. Letter from T. R. Quay, NRC to N. J. Liparulo, Westinghouse, "Three Major Issues Resulting from the Civil Engineering and Geosciences Brat ch (ECGB) Review of the Westinghouse AP600 Advanced Reactor Design," datod l November 4, 1996.

2. Letter from T. T. Martin, NRC to N. J. Liparulo, Westinghouse, "AP600 Advanced Reactor Design site Parameters for Seismic Design and Nuclear j

Island Foundation Mat Adequacy," dated January 31, 1997.

. Westinahouse Response Letters:

3. Letter from B. A. McIntyre, Westinghouse to T. R. Quay, NRC, " Site Conditions - Shallow Soil Sites," dated January 28, 1996.

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. 4. Letter from B. A. McIntyre, Westinghouse to T. T. Martin, NRC,

" Structural Key Issues," dated February 10, 1997. l l

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