ML20141M825

Forwards Contribution to SER Rev Re Effects of 860131 Earthquake.Compilation of Facility Technical Evaluation Rept Documentation Will Not Be Completed by Deadline.Telephone Discussion Requested

ML20141M825
Person / Time
Site:	Perry
Issue date:	02/26/1986
From:	Jerrica Johnson STRUCTURAL MECHANICS ASSOCIATES
To:	Hermann R Office of Nuclear Reactor Regulation
References
NUDOCS 8602280326
Download: ML20141M825 (11)

Text

g STRUCTURAL mECHRnKS

- ASSOCIRTES w- .c....c...

Two Annabel Lane. Suite 101. San Ramon. Cahf. 94583 (415) 820-6988 x

so- 19l441 February 26, 1986 Mr. Robert Hermann Division of Boiling Water Reactor Licensing Office of Nuclear Reactor Regulation US Nuclear Regulatory Commission Phillips Building 7920 Norfolk Ave.

Bethesda, Maryland 20014

Subject:

Contributions to the Revised Perry SER due to the January 31, 1986 Earthquake

Dear Bob:

Please find enclosed my contribution to the revised Perry SER subsequent to the January 31, 1986 earthquake. I am currently completing documentation of the effort I expended on Perry in a Technical Evaluation Report -- however, it could not be completed within this deadline. I hope this information is helpful.

Please give me a call to discuss it further.

Sincerely (mkA Jadies J . Jo son JJJ/jm Encls.

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r Contribution to the Revised Perry SER Five topics were identified to be discussed relative to the effect of the January 31, 1986 earthquake on the Perry Nuclear Power Plant.

1. Overview of previous SER

2. Changes since the last SER

3. Impact on applicable plant systems of the January 31, 1986 earthquake.

4. Findings and determinations.

5. Conclusions Contributions to topics 3,4, and 5 for the Perry structures (including soil-structure interaction and structure response) are contained here.

Background

' At approximately 11:47 a.m. EST on January 31, 1986, an earthquake occurred of magnitude 4.9 Mb. Its epicenter was 11 miles south of the Perry Nuclear Power Plant. The earthquake was felt at Perry and motions were recorded at several locations in the Perry structures.

Three different types of instruments recorded the event at Perry. One type of instrument is the Kinemetrics Model SMA-3 strong motion time history recording accelerograph. This

! instrument records the three orthogonal components of acceleration over the duration of the earthquake. Two of these instruments were installed at Perry -- one on the reactor building foundation mat at approximately elevation 575' and the other is mounted on the containment shell at approximately elevation 686'. Plots of the recorded acceleration time

! histories and calculated response spectra are contained in Ref. 1. These records best describe the characteristics of the

E earthquake ground motion, i.e. short strong motion duration (less than 1 sec.) and high frequency motion.

The second type of instrument is the Engdahl PSR 1200-H/V response spectrum recorder. This instrument records the response of a series of single degree-of-freedom oscillators to the motion. It generates response spectral ordinates at discrete frequencies, in this case, twelve discrete frequencies ranging from.2 Hz. to 25.4 Hz., for a fixed damping value of 2% of critical. This instrument measures response spectra in three orthogonal directions. Four instruments of this type were used

-- two on the auxiliary building foundation mat at an approximate i elevation of 568', one on the reactor building foundation mat at 4

an approximate elevation of 575', and one in the reactor building on the drywell platform at an approximate elevation of 630'.

I The third type of instrument is the Engdahl Par 400

peak accelerograph. It records three orthogonal components of peak local acceleration. Two instruments of this type were used

and were located on the auxiliary building foundation mat at an l approximate elevation of 568' and on the reactor recirculation pump at an approximate elevation of 605'. A third instrument was 1

out of service.

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3. Impact on applicable plant systems of the January 31, 1986 earthquake.

The scope of the review includes the seismic system and i subsystem analysis of the plant including Category I structures and systems. The impact of the January 31, 1986 earthquake on

[ the seismic design of structures and on the seismic analysis methods including soil-structure interaction and structure i response is reviewed.

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4. Findings and determinations The bases for this preliminary evaluation are as follows:

(i) Submittals by the utility (Refs. 1, 2 , and 3)

(ii) Follow-up and clarifying conversations with the utility and its architect-engineer.

i (iii) Recorded acceleration time history records obtained from tape.

(iv) References in the open literature concerning the effects of earthquake characteristics, such as f requency content and duration, on structures.

i (v) Independent response analyses of the Perry l reactor building.

(vi) Plant visit and inspection.

Effect of January 31, 1986 earthquake on structures The characteristics of the recorded motions on the foundations of the reactor building and the auxiliary building are judged to be similar in frequency content to the free-field ground motion. The phenomenon which could lead to different foundation motion compared to the free-field is soil-structure interaction / structure response. All category I structures except the diesel generator building and the off-gas building are f ounded on very stif f rock (shear wave velocity of 4900 ft/sec) or fill concrete of similar shear wave velocity. These very I stiff materials are generally thought to preclude significant

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soil-structure interaction effects. In addition, the reactor building was analyzed as a fixed-base structure subjected to the

recorded foundation motions (three translations) and good correlation of calculated and measured in-structure response was observed. This good correlation implies that rocking of the foundation was not significant, whereas, rocking of the foundation is an important SSI phenomenon. Hence, it is judged that the recorded foundation motions are similar to the free-field ground motion in frequency content. The earthquake motion is characterized by a very short strong motion duration (less than 1 sec) and significant frequency content at high frequencies (near 20 Hz) .

There is a vast literature which documents the low damage potential of earthquakes of short duration and high frequencies. One of the most recent investigations was that of Kennedy et al. (Ref. 4). This investigation sought scale factors by which earthquake records must be scaled to induce specified levels of nonlinear deformation. Two levels of nonlinear deformation were considered, as defined by du'ctility ratios of 1.85 and 4.27 A ductility level of about 1.85 represents a best estimate of the inelastic deformations which would occur in a shear wall designed for static lateral loads to the ACI-349 code capacity (Ref. 4). Representative stiff structures of

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fundamental frequencies ranging from 2.14 Hz. to 8.54 Hz. were considered. Recorded ground motions of varying frequency content and duration were considered. None had as short a duration or as high a high frequency content as that recorded at Perry. Two records of short duration and somewhat higher f requency content (although still less than 10 Hz.) were the Gavilan College, Hollister, 1974 record and the Melendy Ranch Barn, Bear Valley, 1972 record. For a structure of fundamental frequency of 3.20 Hz. (near that of the Perry reactor building), the two recorded motions would need to be scaled by factors of 1.6 to 2.2 to achieve deformations corresponding to the design level forces.

Alternatively, a measure of the ef fective peak ground acceleration of these records would be the instrumental peak divided by these factors. If a similar procedure were applied to the recorded foundation motions at Perry, the scale factors are expected to be significantly higher than 2 and, consequently, a measure of the effective peak ground acceleration of the Perry motions would be perhaps 1/3 of the instrumental peak acceleration or less. Excitations of this type have limited energy and, hence, little damage potential.

Soil-Structure Interaction and Structure Response The seismic analysis of the Perry Category I structures involved developing mathematical models of their dynamic behavior and analyzing them for the design ground motion. The ability of these models to predict response from the January 31, 1986 earthquake was investigated. To do so, Refs. I and 2 and a tape containing the recorded acceleration time histories on the reactor building foundation were utilized. The following steps were performed.

1. Reference 1 was reviewed wherein the utility itemized a frequency and mode shape of the containment vessel near 18 Hz. and with a significant modal participation factor. The argument was made that this mode amplified the free-field motion to obtain the measured record in the containment vessel. This model included soll springs, which although stif f, raised the question of their importance.

2. Reference 2 was reviewed and the reactor building dynamic model implemented on the LLNL computer system. Frequencies and mode shapes were extracted for this model which included soil springs and checked with those of the utility.

3. A fixed-base eigenvalue extraction was performed on the model and the moden interrogated to determine

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whether a mode of frequency near 20 Hz. had high importance to response of the containment vessel at a location near the recording. Such modes do exist in both the N-S and E-W directions and they are the second most important modes for the containment vessel's response.

4. Further verification of their ability to amplify the recorded motion was derived by performing a fixed-base time history analysis using the recorded foundation acceleration time histories as input.

Figure 1 compares response spectra for the recorded foundation motions and the calculated containment vessel response at approximately elevation 688'.

Figure 2 shows a comparison of response spectra of the recorded motions on the foundation and on the containment vessel at elevation 686'. Figure 1 shows clearly the amplification of the 20 Hz.

motion from the foundation to the point on the containment vessel. The magnitude of the amplification is less than the recorded motion, however, this preliminary analysis simply assumed a design damping value of 4% of critical which is an important factor. Also, peak spectral amplification is widely recognized to be uncertain.

Open Issues-For the diesel generator building and the off-gas building which are founded on fill rather than rock, the applicant agreed to assess the effect of the January 31, 1986 earthquake on their response.

For tha reactor building, the applicant agreed to assess the effect of the January 31, 1986 earthquake on calculated structural loads. His initial assessment for the containment shell showed them to be very low and below the design basis.

5. Conclusions The January 31, 1986 earthquake is judged to have had an insignificant effect on the Perry Nuclear Power Plant structures. Further, it is judged that the Perry seismic analysis models adequately predict the behavior of the reactor building when subjected to this event. Finally, pending resolution of the open issues, the plant design of the structures is judged to be acceptable and unaf fected by the event.

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Fig. 2 Response Spectra on the Peactor Building Foundation vs. Elev. 686' on the Ccntainment Vessel - bbasured.

I REFERENCES

1. The Cleveland Electric Illuminating Co., " Seismic Event Evaluation Report, Perry Nuclear Power Plant, Docket Nos.

50-440; 50-441," February 1986.

2. Gilbert / Commonwealth, " SAP IV Input and Output Listing - L i

Perry Reactor Building Updated Seismic Analysis," Received '

February 17, 1986.

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3. The Cleveland Electric Illuminating Co., " Seismic Event I

Evaluation, Technical Presentation, February 11, 1986,"

presented at the Perry Nuclear Power Plant, February 11, 1986.

4. Kennedy, R. P., Short, S. A., Merz, K. L., Tokarz, F. J.,

Idriss, I. M., Power, M. S., and Sadigh, K. (1984 ),

" Engineering Characterization of Ground Motion, Task I:

Effects of Characteristics of Free-Field Motion on I

Structural Response," NUREG/CR-3805, Vol. 1, Prepared for

, U.S. Nuclear Regulatory Commission.

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