ML20137U440

Requests Addl Info on Plant Amend of Cooling Water Sys Emergency Intake Design Basis

ML20137U440
Person / Time
Site:	Prairie Island
Issue date:	04/11/1997
From:	Wetzel B NRC (Affiliation Not Assigned)
To:	Richard Anderson NORTHERN STATES POWER CO.
References
TAC-M97816, TAC-M97817, NUDOCS 9704170001
Download: ML20137U440 (4)

Text

.. , . - - - - - . . .. . - -- -- .- -- --

a April 11, 1997 0

. Mr. Roger 0. Anderson, Director 1

Licensing and Management Issues Northern States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401 4

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON THE PRAIRIE ISLAND NUCLEAR

, GENERATING PLANT, UNITS 1 AND 2, AMENDMENT OF COOLING WATER SYSTEM EMERGENCY INTAKE DESIGN BASIS (TAC NOS. M97816 AND M97817)

Dear Mr. Anderson:

By letter dated January 29, 1997 Northern States Power Company (NSP) submitted a request to amend the licensing basis for the Prairie Island cooling water system emergency intake. To review the proposed changes the staff required additional information which NSP provided by letter dated March 10, 1997.

After reviewing the provided responses the staff requires further information.

Our request for additional information (RAI) is enclosed. i In order to continue our review of your submittal, please provide your response to the staff's RAI as soon as practical. If you have any questions regarding the content of the RAI, please contact me at (301) 415-1355.

Sincerely, ORIGINAL SIGNED BY Beth A. Wetzel, Project Manager Project Directorate III-I Division of Reactor Projects - III/IV Office of Nuclear Reactor Regulation Docket Nos. 50-282, 50-306

Enclosure:

As stated cc w/ encl: See next page

$$ h b l

DISTRIBUTION:

Docket Filer i 160047 PuBLIC J.Jacobson, DRP, RIII PD3-1 RF J. Roe J.Luehman EAdensam (EGA1) OGC ACRS GBagchi WLeFave DOCUMENT NAME: G:\WPDOCS\ PRAIRIE \PI97410.RAI To receive a copy of this document, indicate in the box C= Copy w/o attachment / enclosure E= Copy with attachment / enclosure N =

LJ copy 0FFICE Intern:PD31 E PM:PD31 E LA:PD31 E D:PD31 o , 7 NAME CMunson:db b BWetZel: # CJamerson(h JHann d b 5 DATE 4/ll/97 4/p /97 4//l / 4////97 0FFICIAL RECORD COPY V 9704170001 970411 PDR ADOCK 05000282 P PDR j

A

. Mr. Roger 0. Anderson, Director Prairie Island Nuclear Generating Northern States Power Company Plant cc:

J. E. Silberg, Esquire Tribal Council Shaw, Pittman, Potts and Trowbridge Prairie Island Indian Community 2300 N Street, N. W. ATTN: Environmental Department Washington DC 20037 5636 Sturgeon Lake Road Welch, Minnesota 55089 Plant Manager Prairie Island Nuclear Generating t

Plant Northern States Power Company 1717 Wakonade Drive East

> Welch, Minnesota 55089 Adonis A. Nebiett Assistant Attorney General

Office of the Attorney General 455 Minnesota Street Suite 900 St. Paul, Minnesota 55101-2127 l

U.S. Nuclear Regulatory Commission l Resident Inspector's Office '

1719 Wakonade Drive East l

Welch, Minnesota 55089-9642 Regional Administrator, Region III

, U.S. Nuclear Regulatory Commission l

801 Warrenville Road Lisle, Illinois 60532-4351

. l

Mr. Jeff Cole, Auditor / Treasurer

! Goodhue County Courthouse i j Box 408 Red Wing, Minnesota 55066-0408

?

Kris Sanda, Commissioner Department of Public Service

! 121 Seventh Place East Suite 200 l

St. Paul, Minnesota 55101-2145 Site Licensing

Prairie Island Nuclear Generating Plant Northern States Power Company 1717 Wakonade Drive East Welch, Minnesota 55089 November 1996

^^

C REQUEST FOR ADDITIONAL INFORMATION ON NORTHERN STATES POWER COMPANY'S REQUEST FOR AMENDMENT OF COOLING WATER SYSTEM EMERGENCY INTAKE DESIGN BASIS 1.

In the staff's first request for additional information (PAI), you were

' requested to explain why the Cone Penetration Tests (CPT) were not extended to the depths approximately 43 feet (EL 645) to 46 feet (El 648) below the grade, and how you are certain that there are no liquefiable soil layers below 46 feet (EL 648). You provided a reason refusal at the cone of the CPT device) during the meeting on(e.g., high24, February 1997, and indicated you are certain that there are no liquefiable soil layers below EL 648 based on the CPT. However, a figure (Drawing No. 21 6197) in the Prairie Island Final Safety Analysis Report (FSAR) shows a liquefaction level from EL 645 (West) to EL 620 (East) under the intake canal. Because of this, you installed the intake pipe line from EL 637 (West) to EL 618 (East) below the liquefaction level. Explain the bases for identifying the liquefaction level in the FSAR and indicate whether you have recently performed enough SPT borings to identify liquefiable soils below EL 648 under the intake canal and embankments.

2. In the investigation of the intake canal embankments, two Standard Penetration Tests (SPT) were performed near the two CPT locations (i.e.,

B-3/C-3A and B-7/C-7 borings). The results of N values obtained from the SPT and those calculated from the CPT data agree reasonably well for the B-7/C-7 borings although the CPI shows an unrealistically high N value at the depth of 12 feet El 682).

CPT do not agree very(well for the B-3/C-3A borings.However, Particularly, the the results o SPT results show smaller N values (i.e., 4 to 7) for the soil layer in the depth range of 10 to 20 feet (EL 684 to 674). The staff raised a concern about such low N values during the interaction meeting on February 24, 1997, because the soils may be susceptible to liquefaction.

You indicated that there would not be a liquefaction problem since the soil layer is above the water table at EL 673.5 and the soils are not saturated. However, you informed us during the conference call on March 3,1997, that the normal water elevation of the canal surface is at EL 674.5 and that you will be using that water level for a calculation of the water volume in the supplementary amendment.

The staff still has a concern about the liquefaction susceptibility of the soil layer considering: (1) the soils are already partially saturated due to the capillarity phenomenon, (2) possible f ull saturation due to the upward propagation of the pore water pressure from the bottom soil layer (below EL 674.5) during the seismic cyclic loadings, and (3) full saturation of the soil layer due to a higher water table.

Provide a rationale for using the N values calculated from the results of the CPT, using the relationship developed by Harza Engineering Company, instead of using the SPT N values actually obtained in the field, as is the commonly accepted practice (see Reference 1).

ENCLOSURE

L  ;

e  !

3. In view of the discussions above in Questions 1 and 2, indicate whether you have a plan to do additional SPT borings, possibly with a small spacing interval between the borings and near the toe of the embankments '

and/or away from the toe on the floor of the canal to identify a liquefiable soil.

4. Your submittal (Reference 2) shows that there are two submerged guide walls in the . intake canal near the screenhouse. Provide the following:  ;

a) The dimensions and the locations of the walls.

b) Discuss the functionality of the walls with respect to the flow rate.

c) The effects of the walls on the water flow if the embankment slope fails and fully or partially closes the gaps between the walls. .

5. .In the meeting on February 24, 1997, you indicated that the Prairie ,

Island design basis. ground motion is equivalent to a magnitude 4.5 '

earthquake. We have checked the relationship between earthquake intensity and magnitude which the NRC has used in licensing nuclear power ,

plants and found that the Modified Mercalli intensity VI used for determining the Prairie Island design basis ground motion is equivalent to a magnitude 5.0 and not 4.5. Does the characterization of the design ,

basis ground motion as a magnitude 4.5 earthquake rather than a magnitude  !

5.0 earthquake have an effect on your analysis?

6. Discuss how you could compensate for the entrainment of debris and/or fine silty / sandy soil particles in the water when the. embankment sluffs off and the bottom floor of the intake canal boils due to soil liquefaction, and the effect that would have on the cooling water pumps and heat exchangers.

7. With respect to the ongoing dynamic analysis for the, slope stability, you are requested to consider the following:

a) If a sin' gle artificial time history is generated from the design response spectra defined in the FSAR, demonstrate the adequacy of the artificial time history including a calculation of power spectral density function of the artificial time history.

b). If multiple (at least four) time histories are generated from.the design response spectra defined in the FSAR, develop four response '

spectra using the four artificial time histories generated and demonstrate that the response spectrum obtained from the average of the four response spectra envelopes the licensing basis design  :

response spectrum. l c) Provide the four response spectra developed from the four artificial ,

time histories, and compare with the design response spectrum of the  !

FSAR.

ENCLOSURE

_ _ __ __. _ _ .-_ _-__ ~ .. . _ . . . _ . _ _ _ _ . . . . . . . _ . . . _ _ _ _ . _ . _ _ . _ _

References:

1. EPRI Report NP-6041-SL, "A Methodology for Assessment of Nuclear Power Plant Seismic Hargin," by Electric Power Research Institute, August 1991.

2. The letter dated March 10, 1997, from Joel P. Sorenson at the Northern States Power Company to the NRC, " Supplement 3 to License Amendment Request Dated January 29, 1997, Amendment of Cooling Water System Emergency Intake Design Bases."

l l

1 ENCLOSURE i

- . .