ML16342B288
| ML16342B288 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 03/23/1987 |
| From: | Schierling H Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TAC-59662, NUDOCS 8703310250 | |
| Download: ML16342B288 (26) | |
Text
March 23, 1987 Docket No. 50-275 50-323 LICENSEE:
FACILITY:
SUBJECT:
Pacific Gas and Electric Company (PGIIE)
Diablo Canyon Nuclear Power Plant, Units 1 and 2
NRC AUDIT ON MARCH 4-5, 1987 OF PIPEWAY ANALYSES AND CALCULATIONS BACKGROUND:
The staff and its consultant, Brookhaven National Laboratory (BNL), had reviewed the analyses for the Unit 1 and Unit 2 pipeway structures in 1984/1985.
The results of that evaluation were reported in Supplements 29 and 32 to the Safety Evaluation Report (SSER 29 - March 1985, SSER 32 - July 1985).
The staff had concluded that the analyses performed were, in general, acceptable;
- however, a
confirmatory analysis for the DE and DDE should be performed.
This requirement was included in the Unit 2 full power license (August 26, 1985) as license condition 2.C. (10):
Pi ewa Structure DE and DDE Anal sis (SSER 32, Section 4)
Prior to start-up following the first refueling outage PGRE shall complete a confirmatory analysis for the pipeway structure to further demonstrate the adequacy of the pipeway structure for load combinations that include the design earthquake (DE) and double design earthquake (DDE).
By letter of April 10, 1986 (DCL-86-095)
PGSE submitted its final report on the pipeway structure, "Comfirmatory Analysis of the Unit 2 Pipeway Structure f'r the DE and DDE."
The staff consultant reviewed the report and it was determined that an audit of the models, analyses and calculations was needed to complete the review.
AUDIT:
NRC staff and Dr. A. J. Philippacopoulos, consultant from the Brookhaven National Laboratory (BNL), audited the PG8E models,
- analyses, and calculations for the Diablo Canyon Unit 2 pipeway structure at the PG8E Offices at 45 Freemont Street in San Francisco, California.
Members of the PGSE staff who assisted in the audit and NRC staff and consultant are listed in Enclosure 1.
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audit was requested by the staff in order to complete its eva1uation of the Unit 2 pipeway structure. In preparation for the audit, the staff consultant requested PGKE to make available for the audit the following info+ation: l. Seismic model of pipeway structure for DE and DDE calculations. 2.
Response
calculations including computer printouts for both horizontal and vertical seismic inputs. 3. Details of composite damping calculations. 4. Calculations of stress ratios for load combinations considered. 5. Detailed comparisons between new stress ratios (confirmatory analysis) and previous ones (approximate analysis). 6. Extrapolation of Unit 2 pipeway analysis results to Unit I pipeway structure. Following an introduction and su+nary of the past efforts on the pipeway structure by PG&E the staff and its consultant audited the documentation requested (see above) and made available by PGKE. The following are the preliminary findings of this audit. The seismic analysis of the pipeway structure performed by PGSE prior to the issuance of SSER 32 (July 1985) was based on an equivalent static method. Using that approach, stress ratios were derived in critica1 members of the pipeway using spectral ratios of the DE/DDE to the Hosgri spectra. The confirmatory seismic analysis of the pipeway structure, submitted by letter of April IO, 1986 (DCL-86-095), was based on a rigorous time history analysis of the pipeway structure using the acceleration time histories. This audit focused on the rigorous time history analysis of the pipeway structure and in particular on: seismic model, 2. response calculations, 3. composite damping calculations, 4. evaluation of stress
- ratios, 5.
comparison between the confirmatory and the approximate analysis results, and 6. applicabi1ity of Unit 2 results to Unit l. During the audit the licensee stated that the seismic model used in the DE/DDE confirmatory analysis is the same as the model used in the Kosgri analysis of the pipeway structure. Since the latter model is of the fixed-base
- type, the staff reauested the licensee to,iustify the appropriateness of the Hosgri model for use in the DE/DDE seismic calculations.
Further, it was observed that the stress ratios derived in the confirmatory analysis are based on new dead load stresses which were obtained by performing a new static analysis. PGSE was requested to justify this analysis and in particular to determine what fraction of the difference between the stress ratios from the approximate
1 II
and the confirmatory analyses is due to the new dead load analysis.
- Finally, issues relating to the damping associated with the seismic input were raised and satisfactorily resolved during the audit.
CONCLUSION: Following a staff/consultant caucus the above three items were identified to PGSE who briefly addressed them. The staff requested PGRE to document the responses and provide further information on the first two items, namely {1) the applicability of the Hosgri model to the DE/DDE Seismic evaluation and (2) the input of the new dead load static analysis on the stress ratios at critical members reported in the April 10, 1985 submittal. The staff stated that the information will be included in this meeting summary and will be considered in the staff final evaluation. The audit was completed in the afternoon of March 5, 1987. [On March 16, 1987 PGSE provided the requested information including the damping related issue, by telefax to the Diablo Canyon Project Manager. The information is attached as Enclosure 2].
Enclosures:
As stated Hans Schierli g, Project Manager Project Directorate P3 Division of PWR Licensing-A cc: See next page PDg3 CVogart" 3/i> /87 PDg3 HSchier ing:pds 3/p+87
, ~ 4'H I ~ Hy 4 4 r, I I 4 4 4 F' I V 4 II
Mr. J. D. Shiffer Pacific Gas and Electric Company Diablo Canyon CC: Richard F. Locke, Esq. Pacific Gas & Electric Company Post Office Box 7447 San Francisco, California 94120 Janice E. Kerr, Esq.. California Public Utilities Commission 350 McAllister Street San Francisco, California 94102 Ms. Sandra A. Silver 660 Granite Creek Road Santa Cruz, California 95065 Mr. W. C. Gangloff Westinghouse Electric Corporation P. 0. Box 355 Pittsburgh, Pennsylvania 15230 Managing Editor San Luis Obispo County Telegram Tribune 1321 Johnson Avenue 1726 M Street, N.W. Suite 1100 Washington, DC 20036-4502 Mr. Leland M. Gustafson, Manager Federal Relations Pacific Gas and Electric Company 1726 M Street, N. W. Washington, DC 20036-4502 Dian M. Grueneich,
- Esq, Edwin F. Lowry, Esq.
Grueneich & Lowry 345 Franklin Street San Francisco, California 94102 NRC Resident Inspector Diablo Canyon Nuclear Power Plant c/o U.S. Nuclear Regulatory Commission P. 0. Pox 369 Avila Beach, California 93424 Mr. Dick Blakenbura Editor & Co-Publisher South County Publishing Company P. 0. Box 460 Arroyo Grande, California 93420 Bruce Norton, Esq. c/o Richard F. Locke, Esq. Pacific Gas and Electric Company Post Office Box 7442 San Francisco, California 94120 Dr. R. B, Ferguson Siera Club - Santa Lucia Chapter Rocky Canyon Star Route Creston, California 93432 Chairman San Luis Obispo County Board of Supervisors Room 220 County Courthouse Annex San Luis Obispo, California 93401 Director Energy Facilities Siting Division Energy Resources Conservation and Development Commission 1516 9th Street Sacramento, Cali forni a 95814 Ms. Jacquelyn Wheeler 2455 Leona Street San Luis Obispo, California 93400
4
Pacific Gas 8 Electric Company 2 - Diablo Canyon CC: Ms. Laurie McDermott, Coordinator Consumers Organized for Defense of Environmental Safety 731 Pacific Street, Suite 42 San Luis Obispo, California 93401 Mr. Joseph
- 0. Ward, Chief Radioloqical Health Branch State Department of'ealth Services 714 P Street, Office Building fS Sacramento, California 95814 Ms. Nancy Culver 192 Luneta Street San Luis Obispo, California 93401 President California Public Utilities Comnission California State Buildin9 350 McAllister Street San Francisco, California 94102 Regional Administrator, Region V
U.S. Nuclear Regulatory Commission 1450 Maria Lane Suite 210 Walnut Creek, California 94596
ENCLOSURE 1 NPC AUDJT PIPEWAY STRUCTURE MARCH 4-5, 1987 S. Bhattacharya K. Mandaai J. NcCall N. Patel H. Phi lippacopoulos 0. Ogden H. Schierling W. White PGfiE PGSE/Bechtel PGGE PG&E NRC/BNL P GEE NRC PG4E/Bechtel
0
~t ~ ENCLOSURE 2 y$ ~ INFORMATION PROVIDED BY PG&E AFTER UDIT ON MARCH 4-5, 1987 URRtJIIII. Provide justification for not including the rock-structure inte'raction effect in the confirmatory DE/DDE analysis of the pipeway structure. R n N. 1 The confirmatory analyses o'f the pipeway structure for the DE and DDE cases were performed using the "fixed-based" boundary condition of the containment structure. Selection of this boundary condition was determined to be adequate based on the following: Consideration of the rock-structure interaction would reduce the fundamental frequency of the containment structure from 4.5 Hertz to approximately 4 Hertz which results in a reduction in ground spectral acceleration. Since the DE and DDE are not the major contributors of the governing structural loads (see Tables 1 and 2 in Response to Question 2) and the stress ratios due to DE and DDE are low, a slight shift in frequencies is judged not to be critical for structural
- beams, piping, and other commodities.
2. Bhsed on parametric
- studies, Dr. H.
B. Seed and Dr. 3. Lysmer concluded in 1978 that consideration of the rock-structure interacti.on does not significantly alter the response of the containment, except for small increases in rocking which affect the containment response at higher elevations. Since the pipeway structure is located at a low elevation, any possible effects of foundation rocking will be minimum. 3. The NRC determined that the "fixed-based" analysis is adequate for the Hosgri evaluation. Therefore, a similar boundary condition was also used 'or this new model for predicting the DE and DDE results. As indicated in the FSAR Update, the approximate static analysis of the pipeway structure is the analysis of record. That analysis used the DE and DDE spectra of the containment wall developed from the rock-structure interaction study. Since this confirmatory study is not the analysis of
- record, the FSAR criteria related to the rock-structure interaction was not followed entirely.
Furthermore, based on the above discussion, the rock-structure interaction was determined not to be critical for the containment wall at lower elevations. aR~~fr ~n: H. Bolton Seed and John Lysmer,, "Analysis of Soil-Structure Interaction Effect During Earthquakes for the Diablo Canyon Nuclear Power Station," July 7, 1978.
V
inN.2 The dead load stresses used for the confirmatory analysis are based on a different structural model than the one previously used by PGandE. Discuss the significance of the new structural model. n N, The dead load (DL) stresses reported in the approximate analysis (1985) were based on a model (identified as DLH1) which included all structural beams including the platforms. The piping DL was applied at the appropriate support locations. The DL model (identified as DLH2) used for the confirmatory analysis (1986) is. similar to the earlier model (DLHl) except for the following: ~ Loads due to large bore piping were more precisely calculated since they are included as part of the model. A few secondary beams (such as platform members) were replaced by tributary masses to make the model consistent with the dynamic model used in the confirmatory analysis. The DL stresses based on DLH2 are, in general, less than the corresponding DL stresses previously calculated using the model DLHl. At the request of the NRC Staff, Tables 1 and 2, originally submitted in PGandE letter DCL-86-095 dated April 10,
- 1986, have been revised to include the DL stresses based on DLHl.
This revision was requested to assess the adequacy of PGandE's approximate DE and DDE analysis (1985) without taking credit for reduction of the DL stresses. The comparison of the revised stress ratios demonstrates that the stress ratios from the confirmatory analysis are either less or only slightly higher than the values obtained from the approximate analysis. In those cases where increases are noted, the conclusions drawn from the approximate analysis are still applicable.
0
Table 1 Stress Ratios for the Governing Unit 2 Hembers Load Combinations II b Element Shear Bending Shear Bending Shear Bending Shear Bending 297D 0.35 297S 1.00 310D 0.02 310S 0.04 311D 0.14 311S 0.16 328D 0.04 328S 0.06 329D 0.04-329S 0.06 0.36 0.31 0.31 0.62 0.91 0.52 0.06 0.03 0.04 0.06 0.03 0.05 0.07
- 0. 15 0.08 0.06 0.13 0.03 0.17 0.05 0.12 0.32 0.16 0.20 0.24 0.03 0.17 0.32 0.11 0.27 1.0 0.90 0.94 0.69 1.0 0.80 0.94 0.69 0.24 0.60 0.13 0.50 0.35 1.00 0.13 0.50 0.50 0.59 0.40 0.52 0.72 1.00 0.40 0.52 0.39 0.55 0.36 0.43 0.55 0.91 0.36 0.43 0.39 0.61 0.36 0.43 0.50 0.98 0.36 0.43 330D 0.02 330S 0.05 331D 0.05 331S 0.14 405D 0.22 405S 0.29 0.18 0.23 0.19 0.39 0.40 0.63 0.02 0.13 0.11 0.19 0.04 0.14 0.16 0.23 0.17 0.31 0.26 0.52 0.38 0.52 0.36 0.43 0.50 0.90 0.36 0.43 0.53 0.612 0.51 0.49 0.70 1.00 0.51 0.49 0.47 0.97 0.35 0.71 0.55 0.80 0.35 0.71 Note:
D and S after the element numbers denote results from the dynamic analysis and approximate static analysis, respectively. The dead load components for the dynamic stress ratios are taken from the approximate static analysis. The results of the approximate static analysis and the values of Yr are reproduced from page 4 of Attachment E to Reference 4.
Table 2 Stress Ratios for the Governing Unit 1 Hembers f Load C o m b i n a t i o n s Element Number 4 Unit 1 Unit 2 Shear Bending Shear Bending Shear Bending Shear Bending 496D 615D 0.36 0.59 0.44 0.70 496S 615S 0.53 0.96 0.65 0.97 0.32 0.58 0.26 0.54 0.46 0.97 0.34 0.72 1310D 20D 0.05 0.25 0.06 0.25 1310S 20S 0.20 0.91 0.22 0.92 0.04 0.21 0.16 0.77 0.03 0.15 0.13 0.62 974D 282D 0.02 0.30 0.02 0.25 974S 282S 0.10 '.97 0.11 0.85 0.02 0.31 0.02 0.27 0.09 0.82 0.08 0.69 961D 279D
- 0. 01
- 0. 01 961S 279S
- 0. 18 0.15 0.01 0.01 0.27 0.17 0.01 0.04 0.01 0.04 0.16 0.15 0.21 0.13 962D 280D 962S 280S 0.01 0.01 0.28 0.18 0.01 0.01 0.32 0.17 0.01 0.04 0.01 0.04 0.23 0.15 0.19 0.13 971D 281D 0.01 0.16 0.01 0.17 971S 281S 0.13 0.94 0.14 0.85 0.02 0.31 0.02 0.27 0.12 0.82 0.10 0.69 972D 652D 0.02 0.18 0.02 0.18 972S 652S 0.13 0.93 0.15 0.83 0.01 0.11 0.01 0.10 O.ll 0.69 0.09 0.57 Notes:
D and S after the element numbers denote results from the dynamic analysis and the approximate static analysis, respectively. The dead load components for the dynamic stress ratios are taken from the approximate static analysis. The bending stress ratios of the approximate static analysis are reproduced from page 8 of Appendix 5 to Reference 4.
The FSAR Update documents the adequacy of the DDE time-histories based on a comparison with the target spectra at 5 percent damping. The confirmatory analysis uses damping values of 2 percent for the structure and 0!5 percent for the piping. Discuss the effects of the differences in the damping values. The DDE time-histories are described in the FSAR Update and the adequacy of the time-histories are primarily confirmed based on a comparison of the resulting spectra with the target spectra at 5 percent damping. NRC',s acceptance of the time-histories 1s documented in Sect1on 3.7 of "Safety Evaluation of Diablo Canyon Nuclear Power Station Units l and 2," October 16, l974. The FSAR Update also allows'use of 5 percent damping for the containment
- concrete, 2 percent damping for the structural steel, and l/2 percent for piping for the DDE analysis.
PGandE's confirmatory analysis uses 2 percent damping for both containment concrete and structural steel and l/2 percent for piping. 1t, is PGandE's judgment that use of the lower damping for containment concrete for DDE analysis 1s conservative. To confirm this )udgment, PGandE has completed a parametric study in which the nine-mass beam model of the containment was analyzed using the two structural damping values (2 percent and 5 percent). Since the containment represents approximately 94 percent of the total mass, 1t was determined that use of the containment alone to represent the'superstructure was sufficient for this study. Figure 1 shows the comparison of the two spectra at elevation 109 (Node point 9) for the DDE input time-histories. The comparison demonstrates that the use of 2 percent structural damping in con)unction with the DDE analysis is conservative.
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aespanse Spectra I El. >09'~ Mass aantaU110-nt ~> Pique 1 5% Sttottural Danying 2% StXIX.'ttttlD Ipillg IXE Ttme-Hi.story (Bori.nntal) 1.OO .01 ~ 10 OD <.SEtl) 1 ~ 00
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