ML20096D417

Proposed TS Table 6.5.1 Re Rack Matl Data & Section 7.3 Re Local Buckling of Fuel Cell Walls

ML20096D417
Person / Time
Site:	Sequoyah
Issue date:	05/11/1992
From:	TENNESSEE VALLEY AUTHORITY
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ML20096D413	List: ML20096D410 ML20096D417
References
NUDOCS 9205180031
Download: ML20096D417 (4)

Text

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t Table 6.5.1 RACK MATERIAL DATA (200*F)

Young's Yield Ultimate Modulus Strength Strength Material E (psi) Sy (psi) Su (Psi)

SA-240,304L 27.6 x 106 25,000 71,000 (modified)*

Section III Table Table Table Reference I-6.0 I-2.2 I-3.2 SUPPORT MATERIAL DATA (200*F)

Young's Yield Ultimate Modulus Strength Strength Material d (pai) Sy.(psi) Su (psi) l 1 SA-240, 27. 6 x 10 #' 25,000- 71,000 t Type 304L (modified)*

(upper part of support feet) l i 2 SA-564-630 27.6 x 106. 106,300 140,000 (lower part of support feet; I

age hardened at l

1100'F)

-Dual certified to have chemical composition.of 304L material and physical properties of 304 material.

9205180031 920511 POR ADOCK 05000327 P PDR 6 - - , . - - .

- - . - - - ~,- .- - - - .. -

_ . . ~ _ -

i

. 7.3 Local Bucklina of Fuel Cell Walls This subsection and subsection 7.5 present details on the secondary stresses produced by buckling- and by temperature effects.

The allowable- local buckling stresses in the fuel cell walls are obtained by using classical plate buckling analysis. The following formula for the critical stress has been used based on a width of cell "b" [7.3.1):

n2 Et2 Ocr "

12 b2 (1 - p2) o cr is the limiting vertical compressive stress in the tube, E =

27.6 x 106 pai, p = 0.3, (Poison's ratio), t= . 060" (away from a pedestal), b = 8.75". The factor is suggested in (Ref. 7.3.1) to be 4.0 for a long panel. Near a pedestal, additional cel) wall 4 strength is provided by added strip material which increases the effective thickness of the region prone to buckling to .1045" in the highly loaded region.

For the given data, e i

ccr = 14232 psi  ;

f It should be noted that this stability calculation is based on the applied stress being uniform along the entire _. length of the cell wall. In the actual-fuel rack, the compressive stress comes from consideration of overall bending of the ' rack structures during~a-seismic event and _ as s uc.h is negligible at the rack top and >

maximum at the rack bottom. It is-conservative to apply the above equation to the rac E cell- wall -if we compare a cr with the-maximum compressive stress anywhere in the.-cell wall._As shown in Section -

6, the local buckling str_ess-limit is not-violated anywhere in the body of the rack modules. The' maximum compressive stress in the 7-3 W g*  %---cr>------. e- 9yq.*p4-- . .

- . y.,..,, ,.,.b,4. .c._- v r . - . - .e g mi

,, y , g,pg g e eg- y -.eqe

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

.

• l l

l l

l

. outermost cell is obtained by multiplying the limiting value of the strese factor R6 (for the cell cross-section just above the baseplate) by the allowable stress. Thus, from Table 6.7.2, o=

R6 x allowable stress = .333 x 25000 = 8325 psi under faulted conditions.

7.4 Analysis of the ImpqgLShield for Cask A,1 1 To maximize the storage capacity of the spent fuel pool, a spent-fuel stcrage isek containing 225 cells (15x15 cells) is proposed to be installed in the 12'x12' cask loading area of the cask pit ,

1 of the sequoyah spent fuel storage pool. After installation of the rack in the cask _ pit, the pit will be equipped with a removable impact shield (SA-36 material) to prevent accidental dropping of any object on the fuel rack. The proposed impact shield la shown in Figure 2.4.16. It consist.9 of panel coverplates attached to a  ;

frame made of wide flange beams. This shield is designed to withstand a total load of 288,000 lbs. uniformly applied on the whole shield, or a total load of 70,000 lbs. uniformly applied on ,

one of the panel plates. The panel plate thickness is detecrmined by a limit load analysis, and the dimensions - of the wide flange beams are chosen so that the maximum stresses in the frame for the '

postulated load cases are within the corresponding allowables.

l The AUSYS finite element program is used to perform the frame stress analysis. The results are summari::ed below:

(1) Panel plate can resist a uniform' load of 70,000 lbs, on one panel or a concentrated load of 7952 lbs. applied at any point without sustaining a plastic collapse.

-(2) Maximum direct plus bending stress in the frame beams is 51961 psi, which is below 90%~~of the ultimate material-strength. Maximum average shear stress is 2850 psi, which is less than the postulated- allowable (36,000 psi),

(3) Maximum average compression stress on_ concrete wall at the bearing locations is 329 psi, which is considerably _

lower than the allowable (2975 psi).

l 7-4 L

- _ _ _- , _ _ _ - _ . - ~ . - .. _.

r 5

Therefore, we obtain an estimate of maximum weld shear stress in an isolsted hot cell as Imax = 15515 psi l 4

Since this is a secondary thermal stress, it is appropriate to compare this to the allowable weld shear stress for a fculted-event r < .42Su = 29820 psi. Ir. the fuel rack, this maximum stress occurs near the top of the rack and does not interact with any other critical stress.

7.6 References for Section 7 (7.1.1) TVA Specification 3.94-3QNP-90, Revision 1, p. 42.

[7.2.1] TVA Sequoyah Nuclear Plant Updated Final Safety Analysis Report", April, 1991_ Section 9.1.

(7.3.1) " Strength of Materials", S.P. Timoshenko, 3rd Edition, Part II, pp 194-197 (1956).-

{7.5.1) " Seismic Analysis of High Density Fuel Racks, Part III-Structural Design Calculationn -

-Theory", -HI-89330,-

Revis 'on 1, 1989.

l 7-6

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