ML20055D994

Forwards Addl Info Re Seismic Design Considerations for Certain safety-related Vertical Steel Tanks,Per 890525 Request

ML20055D994
Person / Time
Site:	Wolf Creek
Issue date:	07/05/1990
From:	Withers B WOLF CREEK NUCLEAR OPERATING CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
WM-90-0118, WM-90-118, NUDOCS 9007100246
Download: ML20055D994 (4)

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• WQLF CREEK NUCLEAR OPERATING CORPORATION 4

7 Sert D. Withers gg. July 5, 1990 j WM 90-0118

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[U.'S.NuclearRegulatoryCommission

, 'ATTH: Document Control Desk  ;

Mail Station Pl-137 i

-Washington, D. C. 20555 l h >

Reference:

1) Letter dated May 25, 1989 from.F. J. Hebdon, ,,

NRC to B. D. Withers WCNOC

2) ET 89-0076, dated September 22, 1989 from  ;

F. T. Rhodes, WCNOC to NRC  ;

" 3) Letter dated March 27, 1990 from D. V. Pickett, NRC to B. D. Withers, WCNOC

Subject:

_ Docket No. 50-482: Response to Request for Additional Information Concerning Seismic Design ,

Considerations'for Certain Safety-Related Vertical Steel Tanks Gentlemen:

-Reference 1 requested information_concerning seismic-design considerations 1

-for.the Wolf Creek Generating Station (WCGS). Refueling ' Water . Storage y Tank (RWST): which was subsequently provided in Reference 2. Reference 2 provided the results of a reanalysis of the RWST which was performed in accordance with the guidance of Draft Revision 2 of the Standard Review Plan-Section 3.7.3. The NRC Staff performed an audit of = the reanalysis on February 14, 1990 which resulted in a request for additional information (Reference 3). "

The Attachment provides the Wolf Creek Nuclear Operating Corporation (WCNOC). _

response to the request for additional information. If you have at.y questions concerning this matter, please contact me or Mr. H. K. Chernoff of my staff.

Very truly yours,

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Bart D. Withers President and l Chief Executive Officer BDW/jra Attachment 1 l

cc: R. D. Martin (NRC), w/a )

D. V. Pickett (NRC), w/a M. E. Skow (NRC), w/a g

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l J. S. Wiebe (NRC), w/a npn % P.O. Box 411/ Burimgton, KS 66839 / Phone: (316) 364-8831 f)

I 9007100246 900705 An Eques opporiurviy Empsoyer ur<He/vti .I PLIR ADOCk 05,000482 l F i: Oc

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' Attachment to WH 90-0118 Page.1 of.3L

-QUESTION la f During the audit, it was discovered that the forces and stresses on the roof- .;

L angle connecting the cylinder and the roof under.the postulated' seismic. '

loadings were not available. Hence the adequacy of the angle and the angle welds could not be verified. Provide information (summarize results) related to the adequacy of the connection under the postulated seismic loads, i

RESPONSE:

, Forces on the tank roof angle connecting the cylinder and the roof, under- .,

the postulated seismic loadings including the ' sloshing effects, were-calculated. .The angle and the connecting welds were evaluated for these l loads and were found to be structurally adequate. All stresses remain l within the' Code allowables under the pootulated seismic loads. d QUESTION 2:

During the audit, it was discovered that the conclusion of 'no tension" in ..

any part of the tank anchor bolts.and foundation was based on the use of an .!

AISI; formula. which the staff considers inappropriate. Provide information. l (summarize results) regarding the adequacy of the affected tank areas under l the postulated. seismic loadings. Specifically, the following items should j be-included: 1

a. . Adequacy of the anchor bolts-and the bolt lugs (or chairs),

b. Adequacy of the tank shell in tension and'in compression.

1 o c. Stresses in foundation media and the adequacy of.the reinforced concrete

! section'under the sump.

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d. Potential for overturning of the tank and the foundation.

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e. Potential for sliding of the tank and the foundation.

n l .The. method of combining the responses of the three: components of the r l postulated earthquakes should be in accordance with the FSAR commitment.

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RESPONSE

In order to address items "a* thru "e', the method of combining the  !

L responseslof the three components of the postulated earthquakes is discussed. -i first..

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2 Attachment to'WM 90-0118, I

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!Page 2'of 3 j The RWST seismic design calculation used .the ' component- factor method',  !

n which is special case'of the square-root-sum-of-squares (SRSS) method, for-L combining. the three components of the postulated earthquakes. A 1: supplemental analysis has been provided in the calculation to compare this method to the SRSS method. This supplemental analysis demonstrates that the

• techniques- utilized provide more_ conservative results than the=SRSS method.

Therefore, the method of combining the responses of the three. components of the postulated earthquakes is in accordance with the Updated Safety Analysis L Report (USAR) commitments.

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The following provided information and summarizes results of the evaluation '

of the affected tank areas under the postulated seismic loadings' as I specifically noted in items "a' thru "e' above:

a) The analysis for determining the tank anchor bolt tension was based on-an AISI formula which yielded "no tension' in the anchor ' bolt. This.

conclusion was seemingly in conflict with the foundation slab analysis which showed uplift under the footing. The analysis for determining bolt tension has been revised to use classical methods in order to be consistent with the

' foundation _ analysis. The revised analysis results in uplift on the tank anchor bolts. The analysis for-transmitting shear and uplift loads _from_the-. 4

, , tank to the foundation has been revised to include the bolt uplift ' loads j calculated. by the revised analysis. By utilizing static friction between ,

the tank bottom and the concrete footing, it has been demonstrated thatJtank sliding will not occur and, therefore.- the bolts will not experience any. _g shear loads. The bolts, -including all components, have been evaluated for the resulting uplift loads and were found to be structurally adequate.

'b) Based on -the discussion provided above'regarding. combining the.three r

, components of'theipostulated earthquakes, the analysis for . checking the adequacy 1 of the tank shell, as provided in the calculation, remains valid.

It should be noted that the tank shell design is governed by-_ compression, rather than tension, due to a much lower allowable stress in compression. J

.The tank shell was found to be structurally adequate for all loading combinations, c) Additional analysis has been provided in the calculation for evaluating ,

the tank foundation media, including the reinforced concrete section under '

the sump, for the loads from the seismic reanalysis. The calculation conservatively evaluated the main foundation elab by assuming that all the- '

~ load from the sump area was taken by the main slab and the sump section did di not contribute any strength to-the main slab. The reinforced concrete section under the- sump was evaluated for its adequacy to span between the main elab-areas. All reinforced concrete sections of the main foundation slab and under the sump were found to be structurally adequate and the stresses remain within the Code allowables. 1 l

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Attachment-to WM 90-0118  :

I Page 3-of 3' in i; .

d)' ' Based on the discussion provided above- regarding combining the three i components; of the postulated earthquakes, the ' analysis for checking overturning of the tank foundation as provided in the calculation . remains q valid.: The' factor of safety against overturning is.in accordance with the-

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USAR commitment..

e) Based on the-discussion provided above regarding combining the- three-components of the postulated earthquakes, the analysisLfor checking' sliding

. , of the tank foundation as provided in the calculation remains- valid. The factor of safety against sliding is in accordance with the USAR. commitment.

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