ML20134B761
| ML20134B761 | |
| Person / Time | |
|---|---|
| Site: | 05200003 |
| Issue date: | 01/28/1997 |
| From: | Diane Jackson NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| NUDOCS 9701310071 | |
| Download: ML20134B761 (5) | |
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January 28, 1997 1
APPLICANT: Westingh:use Electric Corporatien FACILITY:
AP600
SUBJECT:
SumARY OF MEETING TO DISCUSS WESTINGHOUSE AP600 SEISMIC MARGINS ANALYSIS The subject meeting was held at the Westinghouse Electric Corporation (West-inghouse) office in Rockville, Maryland, on January 9, 1997. The purpose of i
the meeting was to review Westinghouse preliminary calculations and discuss
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pertinent open items related to the AP600 seismic margins analysis. Attach-1 ment 1 is a list of meeting participants. Attachment 2 is a summary of the reviewed documents and issues discussed at the meeting. The meeting summary was prepared with input from the Nuclear Regulatory Commission consultants.
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i The staff reviewed calculations in several sensitive areas and discussed the 1
procedure of applying the high confidence in low probability of failure (HCLPF) methodology with Westinghouse. Many of the staff's questions were answered by Westinghouse, however, the staff raised several concerns that i
require additional information. The staff also requested that Westinghouse include part of Chapter 55, the HCLPF methodology and values, in the standard safety analysis report. Westinghouse stated that this would be considered.
This item will be tracked as meeting open item 1.
original signed by:
Diane T. Jackson, Project Manager j
Standardization Project Directorate-j Division of Reactor Program Management Office of Nuclear Reactor Regulation i
Docket No.'52-003 1 Attachments: As stated cc w/ attachments:
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Westinghouse Electric Corporation Docket No.52-003 cc: Mr. Nicholas J. Liparulo, Manager Mr. Frank A. Ross Nuclear Safety and Regulatory Analysis U.S. Department of Energy, NE-42 Nuclear and Advanced Technology Division Office of LWR Safety and Technology Westinghouse Electric Corporation 19901 Germantown Road P.O. Box 355 Germantown, MD 20874 Pittsburgh, PA 15230 Mr. Ronald Simard, Director Mr. B. A. McIntyre Advanced Reactor Program Advanced Plant Safety & Licensing Nuclear Energy Institute Westinghouse Electric Corporation 1776 Eye Street, N.W.
Energy Systems Business Unit Suite 300 Box 355 Washington, DC 20006-3706 Pittsburgh, PA 15230 Ms. Lynn Connor Mr. John C. Butler Doc-Search Associates Advanced Plant Safety & Licensing Post Office Box 34 Westinghouse Electric Corporation Cabin John, MD 20818 Energy Systems Business Unit Box 355 Mr. James E. Quinn, Projects Manager Pittsburgh, PA 15230 LMR and SBWR Programs GE Nuclear Energy Mr. M. D. Beaumont 175 Curtner Avenue, M/C 165 Nuclear and Advanced Technology Division San Jose, CA 95125 Westinghouse Electric Corporation One Montrose Metro Mr. Robert H. Buchholz 11921 Rockville Pike GE Nuclear Energy Suite 350 175 Curtner Avenue, MC-781 Rockville, MD 20852 San Jose, CA 95125 Mr. Sterling Franks Barton Z. Cowan Esq.
U.S. Department of Energy Eckert Seamans Cherin & Mellott NE-50 600 Grant Street 42nd Floor 19901 Germantown Road Pittsburgh, PA 15219 Germantown, MD 20874 Mr. Ed Rodwell, Manager Mr. S. M. Modro PWR Design Certification Nuclear Systems Analysis Technologies Electric Power Research Institute Lockheed Idaho Technologies Company 3412 Hillview Avenue Post Office Box 1625 Palo Alto, CA 94303 Idaho Falls, ID 83415 3
Mr. Charles Thompson, Nuclear Engineer AP600 Certification NE-50 19901 Germantown Road Germantown, MD 20874
)
s WESTINGHOUSE / NUCLEAR REGULATORY COMMISSION MEETING SEISMIC MARGINS ANALYSIS MEETING PARTICIPANTS JANUARY 9, 1997 H8ME ORGANIZATION G. BAGCHI NRC/NRR/DE/ECGB S. LEE NRC/NRR/DE/ECGB D. JACKSON NRC/NRR/DRPM/PDST 4
R. KENNERLLY NRC/RES Y. PARK NRC CONSULTANT /BNL J. BRAVERMAN NRC CONSULTANT /BNL W. LAPAY WESTINGHOUSE C. HAAG WESTINGHOUSE Attachment I J
s 1
I WESTINGHOUSE / NUCLEAR REGULATORY COMMISSION MEETING SEISMIC MARGINS ANALYSIS JANUARY 9, 1997 l.
Overview by W. LaPay A table of updated fragility parameters, i.e., median, p, S, and HCLPF values, was presented together with a list of available documents for review.
The final report on the seismic margin analysis (SMA) methodology will be provided in Chapter 55 of the AP600 probabilistic risk assessment (PRA) report 4
in 9 A y March. Westinghouse stated that the floor response spectra used for th:. fragility analysis were the envelope of four spectra of different soil conditions. However, the spectra for a rock site dominate for almost the entire frequency range. Westinghouse stated that the time history analysis results for a rock site were used to represent the enveloping response values for components.
Meeting Open Item 2: The staff requested Westinghouse to provide an explana-tion demonstrating that the use of the time history analysis for the rock site was bounding for all AP600 soil sites.
2.
Review of Motor Control Center (MCC)
The HCLPF calculations for an MCC were reviewed based on a document, SM96-9 Class IE Equipment.
The HCLPF values were determined based on the estimated lower bound of qualification test results.
Information regarding critical failure modes (e.g., relay chatter) was not made available during the meeting.
Variability values of B, ; 0.05 and B, ; 0.10 were used to establish the relationship between the median and HCLPF values. The staff considered these variability values to be too low, and it seems that the calculation procedure 3
does not follow the acceptable SMA methodologies (deterministic or j
probabilistic). Another concern is the calculation of the ratio of Test Response Spectra to Required Response Spectra. This ratio, which was deter-mined only at 4.6 Hz, should be calculated throughout the frequency range of i
interest.
Meeting Open Item 3: Westinghouse responded by proposing to eliminate all the median and B-values from the fragility table, and to calculate HCLPF values deterministically for electric equipment.
t 3.
Review on Reactor Vessel Support Structure i
The fragility calculations for the reactor vessel support structures were reviewed based on documents, SM96-1 (support structure), SM96-3 (nozzles), and several design drawings.
In the fragility calculations, an inelastic energy absorbing factor of F,, - 4.0 was used for the support structure based on the estimated ductility factor of p - 10.0 for a plate bending failure. During a phone conversation with a Westinghouse engineer who performed the stress analysis for the support structure, it was found that the critical stress condition was a localized shear stress rather than an overall bending stress.
. i The estimated ductility factor of p - 10.0 is considered to be too high by the staff for such a stress condition. Moreover, the " local" ductility factor was directly used to estimate the inelastic energy absorption factor for the I
reactor vessel.
In a fragility evaluation of a system which consists of several sub-components, e.g., anchor bolts and support structures, the deformation of each sub-system contributes only partially to the overall i
deformation of the system. As a result, the combined ductility factor for the j
whole system is usually much lower than the maximum ductility factor due to a localized deformation.
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Meeting Open Item 4: Westinghouse responded to eliminate the inelastic energy 1
absorbing factor altogether for the reactor vessel in an updated calculation.
i Meeting Open Item 5: Westinghouse was requested to include the failure modes that were considered in each calculation and provide the staff a written explanation of the process Westinghouse uses to identify the possible critical failure modes.
i Meeting Open Item 6: Westinghouse was requested explain how they consider local and system ductility in their calculations.
i 4.
Other Issues l
Almost all the estimated variabilities are considered to be too low, and the i
methodologies to evaluate the p-values are not consistent with the acceptable SMA evaluation practice.
For example, in evaluating the building response factor, the variability of the damping value was ignored. According to l
Westinghouse, it was done so because a conservative damping value of 5 percent was used in the response analysis rather than a higher median-centered value (e.g., 7 percent). This was considered to be not acceptable, because the use l
of a slightly lower damping value does not guarantee a HCLPF margin.
It was observed that both deterministic and probabilistic methods were somehow mixed together in the fragility estimate of a single component.
The ratio of median to the HCLPF values calculated by Westinghouse were found to be low in i
comparison to the past SPRA (seismic probabilistic risk assessment) studies in j
which the ratios are 2.5 to 3.0.
Meeting Open Item 7: Westinghouse was requested to provide the rational for i
using lower bound median values and if the values was used in the PRA.
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