ML20135F744

Suppl 3 to Application for Amends to Licenses DPR-42 & DPR-60 Re Cooling Water Sys Emergency Intake Design Bases

ML20135F744
Person / Time
Site:	Prairie Island
Issue date:	03/07/1997
From:	Sorensen J NORTHERN STATES POWER CO.
To:
Shared Package
ML20135F742	List: ML20135F739 ML20135F744 ML20135F748
References
NUDOCS 9703130404
Download: ML20135F744 (4)

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UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET Nos. 50-282 50-306 REQUEST FOR AMENDMENT TO OPERATING LICENSES DPR-42 & DPR-60

LICENSE AMENDMENT REQUEST DATED January 29,1997 Amendment of Coolina Water System Emeraency intake Desian Bases l

Northern States Power Company, a Minnesota corporation, by this letter dated l March 7,1997, with Attachment 1, provides supplemental information in support of the subject license amendment request dated January 29,1997. Attachment 1 j contains the Prairie Island seismic time histories for use in analysis of the plant I i intake canal slopes.

This letter and its attachments contain no restricted or other defense information. )

NORTHERN STATES POWER COMPANY By _

i Jog. Sorensen'

Plant Manager

Prairie Island Nuclear Generating Plant On this day of before me a notary public in are for said County, 'perschattydppeared, Joel P.' Sorensen, Plant Manager, Prairie Island Nuclear Generating Plant, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief t statements mad in it are true and that it is nfnterposed for delay, 0)m 9703130404 970307

. PDR ADOCK 05000282

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! NOTARY PUBUC MINNEMMR ' ,

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4 ATTACHMENT 1 SUPPLEMENT 3 to LICENSE AMENDMENT REQUEST DATED January 29,1997 Amendment of Coolina Water System Emeraency intake Desian Bases Generation of Artificial Time Histories for Use in the 2-D Finite Element Dynamic Seismic Analysis of Prairie Island intake Canal Slopes Pages 1 through 7

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, GENERATION OF ARTIFICIAL TIME HISTORIES FOR USE IN THE 2-D FINITE ELEMENT DYNAMIC SEISMIC ANALYSIS OF PRAIRIE ISLAND INTAKE CANAL SLOPES The Prairie Island Nuclear Generating Plant (PINGP) is licensed to an Operating Basis Earthquake (OBE) ground acceleration level of 0.06g with the horizontal ground acceleration response spectral shapes given in the FSAR, Appendix A, Plate H4.5. The corresponding Design Basis Earthquake (DBE) response spectra (0.12g ZPA) are scaled up from the OBE spectra by a factor of two. This licensing basis will be

used in the development of the input motion for the dynamic analysis of the intake canal slope.

Six (6) independent (OBE - 0.06g ZPA) time histories are developed from the Prairie Island OBE horizontal ground response spectrum for 5 percent damping given in the FSAR, Appendix A, Plate H4.5.

The details of their derivation are described below. The corresponding horizontal DBE time history is obtained by scaling an entire OBE time history by a factor of 2. The vertical DBE time history is simulated by scaling a second independent OBE time history by a factor of 1.33 (two-thirds of the horizontal x factor of two from OBE to DBE).  !

The 2-D finite element program, OUAD4M, will be utilized for the dynamic finite element analysis. This i prograrn requires as input motion a set of two acceleration-time histories representing the horizontal and

vertical earthquake motions at the base of the model. To obtain the input time history at the base of the finite element model, it is assumed that the DBE time histories are applied as rock outcrop motions. The 4

time histories are then propagated up to the base of the finite element model using the SHAKE program.

Thic procedure was discussed at the NRC-NSP meeting held at the NRC office in Rockville, MD on February 24,1997.

The details of the model, dynamic properties of the layers, the finite element model base time histories, and the QUAD 4M results are currently being developed.

Time History Development i i Six OBE time histories are developed using the 5% damped response spectrum in FSAR, Appendix A Plate H4.5. Each time history consists of 1024 points at a time step of 0.01 seconds, with a ramp-up time of 2 seconds, a strong motion time of 6 seconds, and a ramp-down time of 2 seconds. The time histories are plotted in Figures 1a - f. The correlation coefficients are shown below. All of the off-diagonal terms are less than 0.30, as recommended in Reference 1, Section 2.3.1(d).

1 1.00

-0.04 1.00

-0.19 0.01 1.00 0.22 0.03 -0.18 1.00 0.02 0.10 0.11 -0.02 1.00

-0.04 0.00 -0.10 -0.09 0.00 1.00 in Figures 2a - f, the response spectra generated from these time histories are compared to the target response spectrum (5% damped response spectrum in FSAR Plate H4.5). The average of the six response spectra is shown in Figure 3. The average envelopes the target at all frequencies.

Power Content of the PINGP Time Histories During the NRC-NSP meeting of February 24, power spectral density shapes of artificially generated time histories especially in the low frequency range were discussed. Specifically, the issue of lack of power in the low frequency range was raised. Figure 5 shows the power spectral density curves (PSDs) for the six time histories from Figure 1. It can be seen from Figure 5 that the power is roughly constant and highest in the low frequency range from 0.2 Hz up to about 2 Hz - 3 Hz, then drops off approximately proportionally to f . This shows that the time histories of Figure 1 have adequate power content in the entire frequency range and do not show lack of power in the frequency range of interest.

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Validation of the Artificial Time History Generation Process To demonstrate the validity of this time history generation process, a sample time history was generated utilizing the 5% Reg. Guide 1.60 horizontal response spectrum anchored to ig. This spectrum was selected because a corresponding target power spectral density (PSD) formulation is available in Appendix A of the Reg. Guide. The artificial time history, generated by using the same process as that used for the Figure 1 histories, is shown in Figure 4a. The comparison of the corresponding response spectrum to the Reg Guide spectrum is shown in Figure 4b. The comparison of the corresponding PSD to the target PSD is shown in Figure 4c. It can be seen that computed PSD curve envelopes the target PSD, except at one frequency value, and the computed response spectrum envelopes the Reg. Guide spectrum. This shows that the procedure used to generate the PINGP time histories is validated and it produces time histories with adequate spectral and power content.

Conclusion Based on the above evaluation, the artificial time histories generated herein, envelope the PINGP licensing basis spectrum for 5% damping and have adequate power content in the entire frequency range.

Therefore, these time histories are appropriate for use as basic input motions for the dynamic analysis of the PINGP intake canal slopes.

References

1. ASCE," Seismic Analysis of Safety-Related Nuclear Structures and Commentary on Standard for Seismic Analysis of Safety-Related Nuclear Structures", ASCE Standard 4-86, September 1986.

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