ML20212D959

Forwards Request for Addl Info Re 870113 Proposed Response to NRC Question Re multi-rack Behavior During Seismic Event

ML20212D959
Person / Time
Site:	Byron
Issue date:	02/25/1987
From:	Olshan L Office of Nuclear Reactor Regulation
To:	Farrar D COMMONWEALTH EDISON CO.
References
NUDOCS 8703040243
Download: ML20212D959 (4)

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F bruary 25, 1987 Docket Nos. STN 50-454 DISTRIBUTION STN 50-455 Docket; File. NRC PDR Local-PDR"" PD#3 Rdg.

T. Novak OGC

- Mr. Dennis L. Farrar E. Jordan B. Grimes Director or Nuclear Licensing J. Partlow N. Thompson Commonwealth Edison Company L. Olshan C. Vogan Post Office Box 767 ACRS (10)

. Chicago, Illinois 60690

SUBJECT:

BYRON SPENT FUEL P0OL EXPANSION On January 13, 1987, you -telecopied a proposed response to our question on multi-rack behavior during a seismic event (Enclosure 1). Enclosure 2 is a request for addditional information that we need to satisfy our concerns regarding multi-rack behavior.

The reporting and/or recordkeeping requirements of this letter affect fewer

, than ten respondents; therefore, OMB clearance is not required under PL 96-511.

Sincerely, Leonard N. Olshan, Project Manager Project Directorate #3 Division of PWR Licensing-A

Enclosure:

As stated cc: See next page PD#3 PD#3 g L01shan CVocan 2/25/87 2/25/87

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8703040243 870225 PDR ADOCK 05000454 P

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E2 Mr. Dennis L. Farrar Byron Station Commonwealth Edison Company Units I and 2 cc:

Mr. William Kortier Ms. Diane Chavez Atomic Power Distribution 528 Gregory Street Westinahouse Electric Corporation Rockford, Illinois 61108

-Post Office Box 355 Pittsburgh, Pennsylvania 15230 Regional Administrator, Region III U. S. Nuclear Regulatory Commission Michael Miller 799 Roosevelt Road Isham, Lincoln & Beale Glen Ellyn, Illinois 60137 One First National Plaza 42nd Floor Joseph Gallo, Esq.

Chicago, Illinois 60603 Isham, Lincoln & Beale Suite 1100 Mrs. Phillip B. Johnson 1150 Connecticut Avenue, N.W.

1907 Stratford Lane Washington, D. C.

20036 Rockford, Illinois 61107 Douglass Cassel, Esq.

Dr. Bruce von Zellen 109 N. Dearborn Street Department of Biological Sciences Suite 1300 Northern Illinois University Chicago, Illinois 60602 DeKalb, Illinois 61107 Ms. Pat Morrison Mr. Edward R. Crass 5568 Thunderidae Drive Nuclear Safeguards & Licensing Rockford, Illinois 61107 Sargent & Lundy Engineers 55 East Monroe Street Ms. Lorraine Creek Chicago, Illinois 60603 Rt. 1, Box 182 Manteno Illinois 60950 Mr. Julian Hinds U. S. Nuclear Regulatory Commission Byron / Resident Inspectors Offices 4448 German Church Road

1. '*" "'<^' Byron, Illinois 61010 Mr. Michael C. Parker, Chief Division of Enaineering Illinois Department of Nuclear Safety i

1035 Outer Park Drive Springfield, Illinois 62704 i

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ENCLOSURE 2 1

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S. Putnan - January 13, 1987

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Pro osed Response to NRC Question on hittrack Behavior During a Seismic Event Question #4 l

How was the conservatism of the single rack model demonstrated? The model appears to limit the amount of sliding and tilting of the rack between small gaps. This would not account for potential pfleup of racks against the pool wall. Has this possibility been investigated?

Response

i Rack pile up will not occur because setsmic acceleration levels are below the i

threshold necessary for the large sliding motion of the racks necessary for l

that pile up.

It may be seen from the analysts of an individual isolated rack l

that the input acceleration levels are low enough so that sufficient displacement does not occur to obtain the free sliding behavior necessary to produce such a pfleup. The maximus displacement, inc' uding sliding and tilting of an isolated rack, is 0.122 inches. However, multiple rack behavior may tend to separate the racks.

This condition may be simulated through analysis considering larger gaps than previously assumed so that the single rack analysts impact force bound the i

impacts whf ch may occur in the poo' Additional analysis designed to obtain enveloping rack responses in terms of impact force between racks and the Ifner is proposed to respond to this question. Multiple single rack analysis may be used to maxistze the impact force between racks. The boundary conditions in single rack analysts simulate the condition where the racks are out of phase. The rigid stop springs at the end of the gap stop the rack and allow little energy to be absorbed by the boundary and maximizes impact force.

In reality, the adjacent rack will not be exactly out of phase and will absorb some energy tending to reduce impact force.

If the racks spread apart in the pool, they may come in contact wf th the pool wall liner. The pool liner is backed by concrete and is stronger than the

^~ rack structure and thus is capable of resisting blows larger than the rack can deliver.

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Accordingly, the rack which produces the highest impact force (12 x 14) will i

l be reanalyzed considering an increase in gap size. The gap size will be varted in 1/4" increments starting at 1/4 until racks do non impact.

In order to maximize rack response, the fir 11y loaded rack case and the eccentric

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half loaded rack case will be analyzed. The above analyses will be carried out for the Ifmitin coefficients of friction;p= 0.2 and 0.8.

The above set of parameters will f eld an upper bound on impact force. The maximized impact force will be used to evaluate the racks and pool wall ifner.

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Copies:

l H. Asher - NRC telecooy

5. Gubin - Ceco 35 FNW K. Singh - Holtec telecopy T. Ryan - 28 K. Anfger - Ceco 34 FNE R. Salsbury - 22 1

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ENCLOSURE 2 REQUEST FOR ADDITIONAL INFORMATION - PULTI-RACK BEHAVIOR OF SPENT FUEL POOL RACKS 1.

The proposed approach could be acceptable if it can be shown that seismic acceleration levels are below the threshold necessary for large sliding motion and the results of additional analysis demonstrate significant safety margins.

2.

The statement that the maximum displacement of an isolated rack is only 0.122 inches appears inconsistent with previous results which had shown maximum displacements of 0.1722 inch for the 12X14 rack, and 0.801P inch for 8X14 rack. Explain the discrepancy. How will fluid couplina be treated in the isolated rack model?

3.

If the proposed additional analysis is performed:

a)

The 8X14 rack should also be analyzed since previous analyses showed that this rack experienced both - maximum displacements and maximum impact loads.

b)

The zero initial gap conditions should also be analyzed since it is the nominal condition.

4.

Provide a list of additional cases proposed to be analyzed. Will both interior and edge racks be analyzed? For edge racks, will gaps to the pool wall be reduced as gaps between racks increase?

5.

Provide the minimum safety margins including the margins on girdle bar impact.

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