ML20092N917

Forwards Addl Info Re Spent Fuel Pool Two Region Rerack Mods,Requested by 840607 Telecopy from Franklin Research Ctr

ML20092N917
Person / Time
Site:	Mcguire, McGuire
Issue date:	06/22/1984
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
References
TAC-53531, TAC-53532, NUDOCS 8407050208
Download: ML20092N917 (6)

Text

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l DUKE POWER COMPANY

! P.O. BOX 33180

[~ CHARLOTTE, N.O. 28242 I

HALH.TUCKEN Tetrenose

!- .wwwrer.ne==, (704) 373-4531 I "*'""" """"

June 22, 1984 Mr. Har 31d R. Denton, Director Office of Nuclear Reactor Regulation U. S.' Nuclear Regulatory Commission Washington, D. C. 20555

. Attention: Ms. E. G. Adensam, Chief Licensing Branch No. 4 Re: McGuire Nuclear Station Docket Nos. 50-369, 50-370

Dear Mr. Denton:

'Please find attached additional information concerning the McGuire Nuclear Station spent fuel pool two region rerack modifications. This additional information was requested by a June 7, 1984 telecopy from Franklin Research Center to Duke Power which concerns the spent fuel rack design and analysis.

If there are further questions regarding this matter, please contact us.

Very truly yours, fb.

Hal B. Tucker

~fh WHM/ibh cc: Mr. J. P. O'Reilly, Regional Administrator Mr. W. T. Orders U. S. Nuclear Regulatory Commission Senior Resident Inspector ,

Region 11 McGuire Nuclear Station 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303 g01 I

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9497050208 840622 N ADOCK OS000369 P pg

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PleaseYr'avide a desailed stress report arid relevant design dre:ings for thifuel

• f ricks'bdng analyzed' tor our review. -

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RESPWSE; 'Althoughloth, tbs detailed stiess reports and relevant mq de~ s ign drawingstfar the fuel' racks constitute proprietary b- e,' ,cm

' w o .infhrmatienlanomust. therifore. be maintained in house,

. 'all materihls are av511able for yodybview at our facility.

'J'Ve welcome the opportunity.to discuss with you any concerns

'}'crquestionsfyoymaybgve,.,'

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' ? .S With regard to the,si$li."ted r'1on-linear fi' nite element model, y please provide the follMng:

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a. Confirm whether thii'is a 2-D,a'nalysis. If it is a 2-D model, N '"

explain;h'cw the simultaneous application of a vertical and o, one horizontal seismi.; loaifing ccmponent egn be accormiodated c3 in the analysis. ,

,' , ,. J 1: b.

" Disatss ffo'tv th't timee.; top of iritegretioli N selected-in the

, analysis}rehti,ve .to solutio:Lstabilify syd coh' vergence.

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c. Explain tioW the gaps betwic'Lthe individaal stell and the rigid wall is established in M e model., -

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RESPONSE:' a.77he nonlinear analysis is performed'on a 2-D fin 4e

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.9 4 element model'using a time history input of a horizontal

'h shock and a verWal shock. The linearynodel used C^ V ,,' in'the analy:,Is fC a 3-D mode 1Twhich is run for

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two horizonc.0' directions '.ib 1oads 'for each horizontal direction areStTusted by loaffactors 'from the nonlinear anal'vsis, and tissiNclude the effects

,b of both a horizontal and a brticab ovent. The i

5' results of the,two direction' loads are;tnen combined by the SRSS Cu account for 4he three seismic events.

N, ' b.* A time step Nuly is performed tOdranga of time

'\

h Steps. Jram,.tQ results of this study, it is possible to determine'ihd time step which gives a converged

. '% solutinn6 kefinement of the time step beyond this 3, .

,'h value will not significantly affect 3ha' results. i e

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e 2b. Time Step Study Time step values of 0.005, 0.0025, and 0.00125 seconds were investigated. As shown by the following table, the values at time 0.005 were not converged, values at time 0.0025 were very close to convergence, and the values at time 0.00125 were converged. The final analysis was conducted at a time step of 0.00125 seconds.

Time Step Support Pad Vertical Load Seconds Lbs.

.005 2x1022

.0025 1690

.00125 1680 l

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'l 4 acI The absolute value of the gap between the cell and l

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"/  : rigid pool wall is not specifically used in the ,

, nonliraar model. However, the effects of the gap

, between the pool wall and the fuel racks are used

. _I , 'in the calculation of the hydrodynamic mass which f, .'_

, is used between the cell and pool wall. The vnlue ,

'- r ic;f..this hydrodynamic mass is based upon the gr.ps

't , ,~ .between the perimeter cells and the pool wall and  ;

.the gaps between the interior cells using the method outlined in the paper by R. J. Fritz ("The Effect of Liquids on the Dynamic Motions of Immersed Solids",

7 f' '

ASME Journal of Engineering for Industry, February 1972).

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3. Please provide'information on how the load correction factors are '

derived from the non-linear time history model to be used in the r

detailed sefsmic model.

~, RESPONSE: 'The non-linear model accurately represents the non-linearities ,

of the fuel to cell interaction and the interface between the l

,, rack base and pool floor. (potential lift off and sliding). l As a result, the non-linear model accurately predicts the loads ,

at the rack to environment interface (rack base loads). ,

~

Tfe linear model accurately represents the load and stress distribution in the cells and rack structure within the rack module. -

s The load correction factors based upon the loads at the interface between the rack base and pool floor are used to-4 adjust the overall stresses within the linear model in order to account for the non-linear effects incorporated in l

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tha; non-linear analysis. The load correction factors are determined based on the ratio of the rack base to pool floor  ;

interface loads obtained in the non-linear analysis to the <

loads obtained in the linear analysis.

4. Please elaborate on the procedure to establish the hydrodynamic coupling effects between adjacent racks, and between fuel cell and fuel assembly.

RESPONSE: Hydrodynamic Effects Between Racks - The close proximity of adjacent racks, as well as the size of the racks relative to the gap between racks, is such that extremely large hydrodynamic masses are produced if the racks attempt to respond out of phase. It is this large hydrodynamic mass which causes the racks to respond in phase. The seismic analysis for the McGuire racks treats the racks as if they are hydrodynamically coupled (move in phase).

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a Hydrodynamic-Eff_ects Between Fue.' and Cell - The

. hydrodynamic mass between the fuel and cell is based upon the fuel rod array size and cell inside dimensions using the technique of potential flow and kinetic energy. The hydrodynamic mass is calculated by equating the kinetic energy of the hydrodynamic mass with the kinetic energy of the fluid ficwing around the fuel rods. The concept of kinetic energy of the hydrodynamic mass is discussed in a paper by D. F. DeSanto ("Added Mass and Hydrodynamic Damping of Perforated Plates Vibrating in Water", ASME Journal _of Pressure Vessel Technology, MafT981).

9

5. Please provide a list of issumptions used in the analysis.

RESPONSE: The basic assumptions for the seismic analysis are as follows:

Structural Damping: A structural damping value of 2% was used for both OBE and SSE events.

Material Damping: The material danping was neglected.

Fluid Damping: The fluid damping _was neglected.

Fuel Impact Damping: A damping value of 15% was used to represent the impact damping of the fuel assembly intermediate grids.

6. Please identify the fuel modules being analyzed in Regiont 1 and 2,a~nd provide results of stresses and horizontal displacements j for ~the following cases: u =0.2, 0.4, 0.6 and 0.8.

l-RESPONSE: The fuel rack modules. analyzed are as follows:

Region 1: The 11 x 13 rack is the module analyzed.

l- Thisis the only rack size in Region 1.

? Region 2: The 12 x 16 rack is the module analyzed.

i- This rack size is evaluated since it has

! the smallest pad spacing (12 cell direction)

L and thus has the greatest potential for

! . iift off and rocking.

i

Fuel rack stresses and displacements for friction f coefficients of u = 0.2 and 0.8.are analyzed. The maximum sliding distance (rack base horizontal displacement) of the rack module is obtained for the u =0.2 case.

L The reaximum rack loads and structural deflections

} are obtained for the u = 0.8 case. These two cases envelop the values of intermediate friction coefficients.

y. . .

Please refer to page 2.3-5 of the McGuire Safety and Environmental Analysis for the maximum rack sliding distance and to Tables 2.3-1 and 2.3-2 of the same report for the stress results.

7 .- Please indicate the loading pattern of the module used in the analysis (i.e., fully loaded, symmetrically loaded, or diagonally loaded,etc).

RESPONSE: The maximum loads for the McGuire racks are obtained based on a fully loaded condition. This is to be expected since the significant loading mechanism is the interaction between the fuel and the cells (fuel impact on cell). For a condition of the rack being partially loaded with fuel, there are less opportunities for fuel impact and thus the rack loads are less than for the fully loaded condition.

For the evaluation of the rack stability (potential rack overturn), however, the rack is evaluated for both partially and fully loaded conditions.

The support pad vertical displacements for the partial loading and fully loaded conditions are given in the following table for Region 2 fuel racks in the 12 cell direction (the direction of maximum lift-off). It is seen that the maximum lift off is produced by the partial loading of 3 rows of fuel. This condition produces the .ninimum factor of safety against overturn of (>100) which is much larger than the 1.5 minimum requirement. -

Fuel Loading 1 Row 2 Rows 3 Rows 4 Rows Full Support Pad Vertical .006 .010 .011 .010 .005 Displacement Inches

8. Please indicate the mode (of vibr)ation in assessing the hydrodynamic coupling effects between adjacent racks (i.e., symmetric or anti-symmetric) .

RESPONSE: The mode of vibration of adjacent racks is symmetric (in phase) due to the strong hydrodynamic coupling effects as discussed in response to question #4.

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