L-84-263, Forwards Response to 840813 Request for Addl Info Re Proposed Amend to Spent Fuel Facility Expansion

Forwards Response to 840813 Request for Addl Info Re Proposed Amend to Spent Fuel Facility Expansion

ML17346A560
Person / Time
Site:	Turkey Point
Issue date:	09/28/1984
From:	Williams J FLORIDA POWER & LIGHT CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
L-84-263, NUDOCS 8410040261
Download: ML17346A560 (56)

Text

REGULATORY INFORMATION DISTRIBUTION SY EM (RIDS)

ACCESSION NBR:8410040261 DOC,DATE: 84/09/28 NOTARIZED; NO FACIL:50-250 Turkey Point Plantg Unit 3g Flor )da Power and Light C

50-251 Turkey Point Plant~ Unit 4i Florida Power and Light C

AUTH BYNAME AUTHOR AFFILIATION WILLIAMSiJ>W ~

F 1 or ida Power 5 Light Co, RECIP,NAME RECIPIENT AFFILIATION VARGA S,A, Operating Reactors Branch 1

SUBJECT; For wards response to 840813 request for addi, info re proposed amend to spent fuel facility expanse.on.

DISTRIBUTION CODE:

A001D COPIES RECEIVED:LTR ENCL SIZE:

TITLE:

OR Submittal; General Distribution NOTES:

OL:07/19/7?

OL:04/14/73 DOCKET 05000250 05000251 05000250 05000251 RECIPIENT ID CODE/NAME NRR ORB1 BC 01 INTERNAL: ADi~l/LFMB NRR/DE/MTEB NRR/DL/DRAB NRR/DS I/RAB RGN2 COPIES LTTR ENCL 7

7 1

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1 RECIPIENT ID CODE/NAME ELD/HDS4 NRR/DL DIR TB REG F

04 COPIES LTTR ENCL 0

1 1

1 EXTERNAL: ACRS NRC PDR NTIS 09 02' 6

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LPDR NSIC Q3i Q5 TOTAL NUMBER OF COPIES REQUIRED:

LTTR 26 ENCL 23

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OX 14000, JUNO BEACH, FL 33408 FLORIDAPOWER 8( LIGHTCOMPANY September 28, 1984 L-84-263 Office of Nuclear Reactor Regulation Attention: Mr. Steven A. Varga, Chief Operating Reactor Branch 81 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Mr. Varga:

Re:

Turkey Points Units 3 & 4 Docket Nos.

50-250

& 50-251 Proposed Amendment to Spent Fuel Storage Facility Expansion Additional Information By letter dated August information regarding the and new storage racks.

our responses to these NRC 13,

1984, the NRC requested additional structural design of the spent fuel pit The attachment to this letter provides questions.

If you have any questions, please contact us.

Very truly yours, J.W. Williams, Jr.

Group Vice President Nuclear Energy JWW/GJK/mp Attachment cc: J.P. O'Reilly, Region II Harold F. Reis, Esquire 84100402~1 8409>8 PDR ADOCK 05000250 P

PDR PEOPLE... SERVING PEOPLE

I r

il

FLORIDA POWER Bc LIGHTCOMPANY TURKEYPOINT UNITS 3 8 4 PROPOSED AMENDMENTTO SPENT FUEL STORAGE FACILITY'EXPANSION REQUEST'OR ADDITIONALINFORMATION I.

Please provide the detailed seismic analysis report and relevant design drawing related to welds and support structure for review.

RESPONSE

The detailed stress reports and relevant design drawings for the fuel racks constitute proprietary information and are~maintained by the rack vendor (Westinghouse).

All materials are available for your review and we welcome the opportunity to discuss, with you any concerns or questions you may have.

2.

Please identify the racks'in Region I and II being analyzed.

.RESPONSE:

The seismic analysis was performed for the IOxl I rack in Region I.,This rack has a seven cell pad span in the N-S direction and a ten cell pad span in the E-W direction.

The non-linear model, was run using the seven cell pad span. and did not result in. the pads lifting off the floor. The other two Region I racks are 8xl I racks one of which has seven cell pad

.span N-S and ten cell pad span.E-W and the other has six cell pad span'-S and ten cell pad span'E-W.'he 8xll rack with the six cell pad span was investigated and was also found not to liftoff the floor. Since all the racks have the same number of pads (four) the IOxl I rack will have the highest pad loads and rack stresses.

A similar situtation occurs in Region II.

The seismic analysis was performed for the IOxl4 rack which has an 8xl3 pad span.

The non-linear analysis was run using the 8 cell pad span.

The other racks in Region II with the pad spans are as follows:

3 racks IOxl3 (3xl2 pad span),

I rack 9xl4 (8xl3 pad span),

3 racks 9xl3 (8xl2 pad span), and I rack 9xl3 (7xl2 pad span).

The 9xl3 rack with 7xl2 pad spacing was investigated and found not to lift off the floor.

Thus the IOxl4 rack will have the highest pqd.

loads and rack stresses.

II 3.

a.

Please identify the computer codes used to generate the simplified 2-D nonlinear model and the detailed 3-D linear model.

RESPONSE

The WECAN computer code was used to generate the simplified 2-.D nonlinear model and the 3-D detailed linear model.

b..

Please provide documents on these codes for review.

RESPONSE

The general WECAN code has been reviewed by the NRC through the submittal of Westinghouse document WCAP-8929, "Benchmark Problem Solutions Employed for Verification of the WECAN Computer Program".,For review of additional capabilities which pertain to the fuel rack nonlinear dynamic

analysis, the following documents are available:

Page I of 26

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3.

b.

'CONTINUED:

4.

a.

I.

Shah, V.N. Gilmore, C.B., "Dynamic Ana'lysis of a Structure with Coulomb Friction",

ASME Paper Number 82-PVP-I 8, presented at the I 982 ASME Pressure Vessel Piping Conference, Orlando, FL, June l982.

2.

Gilmore, C.B., "Seismic Analysis of Freestanding Fuel Racks",

ASME Paper Number 82-PVP-I7, presented at the l982 ASME Pressure Vessel Piping Conference, Orlando, FL, June l 982.

Please provide detailed stress and displacement results obtained in the analysis.

'I

RESPONSE

The following constitute the

results, rack displacements,

sliding, and rocking stability obtained from the seismic analysis for both Region I and Region II.

The support pad vertical displacements are used to calculate the overall-rack module rocking for partial and full fuel loading conditions.

However, liftoff does, not occur for the racks evaluated (Region, I and Region II) yielding a factor of safety against overturn much greater than l.5.

Page 2 of 26

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4.

a.

Continued:

RACK DISPLACEMENTS 0

REGION I REGION II SSE Seismic+ Maximum Normal Thermal-e smic+

Normal Thermal Max. Sliding Distance>=.2 (N-Linear Results)

Max. Structural Defi.,c=.8 (N-Linear Results)

Total Displacement One Rack A = Ds+ 5 SSRS Combined Displacement 2 Racks with only i sliding ~

=~~2

~2 Max. Normal Thermal Displacement Max. Combined Thermal 8 Seismic Displacements D= S~.+Dr ax Rack to Rack Gap in in in

~max in in in GAP in

.OOOI

.. I 24

. I 24I

. I 75

.088

.256 0.007 0.086 0.093 O. I 27 0.087 0.2 I 4 SSE Seismic Slidin

+ Max Accident Thermal REGION I'EGION I I SSE Seismic Sliding

+ Thermal Accident Max. Sliding Distance, M, =.2 Max. Accident Thermal Displacement Combined Thermal Bc Seismic Sliding D.= Qs+ S~

Rack to Rack Gap Ds in in in GAP in

.0001

.175

. I 75 I.

0.007 O. I 90 O. I 97 NOTE: THE RACK TO WALLGAPS ARE LARGER THAN THE RACK TO RACK GAPS.

Page 3 of 26

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4.

a.

CONTINUED:

COMPARISON OF LINEARAND NON LINEARMODEL PAD LOADS REGION I I Ox I I NS+ DW EW+

DW'3700 54300 73700 54300 72000 54300 42000 32300 Linear Non Linear Total NS + DW I 47400' 49600

'otal DW I08600 I I 2800 Ratio (NS+DW)/

I '36 I 33 DW Linear Total EW + DW I I 4000'otal DW 86600 Ratio (EW+DW)/

I,32 DW Non Linear II7000 88000

!.33 NS+ DW REGION I I I Ox I 4 EW+ DW 68200 87200 5!800 62000 96300 62000 96300 62000 Linear Non Linear Linear Non Linear Total NS + DW I55400 I45300 Total ED + DW I 92600 I 8 I 600 Total DW I I3800

.I 0 I 900 Total DW I24000 II4500 Ratio (NS+DW)/DW l.37 I.43 Ratio (EW+DW)/DW I.55 l.59 Page 4 of 26

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4.

b.

Also provide he margins of safety for the maximum stresses under various seismic loading conditions.

RESPONSE

REGION I RACKS

SUMMARY

OF DESIGN STRESSES AND MINIMUMMARGINS OF SAFETY Normal 8 U set Conditions I.O Su I.I I.2 l.3 ort Pad Assembl Support Pad Shear Axial and Bending Bearing Support Pad Screw Shear

'Support Plate Shear Weld Shear 2009 570I 4230 3675 2I 52 I5672 23I50+

23I50+

23I50%

9260 9260 23I50+

I0.52 3.06 4.47 l.52 3.30

.48 Design Allowable Margin Stress Stress.

of

~(si)

~(si)

~Safet 3.3

~CII A

2. I 2.2 2.3 2.4 Cell to Bottom Grid Weld Weld Shear Cell to Top Grid Weld Weld Shear Cell Axial and Bending Cell to Wrapper Weld Weld Shear I 5840 I5840

.5 I 4 45I7 23I50%

23150+

I,0++

9260

.46

.46

.94 l.05 A.II

~did A AI 3.I 3.2 3.3 3.4 3.5 3.6 Top Grid Box Member Shear Axial and Bending Top Grid Members Weld Shear Top Grid Outer Member Axial and Bending Shear Bottom Grid Structure Shear Axial and Bending Bottom Grid Members Welds Weld Shear Bottom Grid Base Plate Weld Weld Shear 2055 l659 l3544 l707 l46 3349 I2057 I5702 I594I 9260 I3890 2IOOO I3890 9260

. 9260 I3890 2IOOO 2IOOO 3.5 I 7.37

.55

7. I 4 62.5 I I.77

. I5

.34

.32 Thermal Plus OBE Stress is Limiting

++

Allowable Per Appendix XVII-22 I 5 Eq. (24)

Page 5 of 26

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4.

b. Continued:

REGION I RACKS

SUMMARY

OF DESIGN STRESSES AND MINIMUMMARGINS OF SAFETY Normal 8 U set Conditions 1.0 Grid Assembl

- Cont'd 3.7 Bottom Grid Outer Member Axial.and Bending Shear 3.8 Base Plate Stiffener to Base Plate Weld Weld Shear Design Stress

~(si) 12050 768'3500 Allowab le Stress

~(si) 13890 9260 21000 Margin of

~Safet

.15 11.06

.56 REGION 2 RACKS

SUMMARY

OF DESIGN STRESSES AND MINIMUMMARGINS OF SAFETY Normal 6 U set Conditions rt Pad Assembl 1.0 SuI.l Support Pad Shear Axial and Bending Bearing 1.2 Support Pad Screw Shear 1.3 Support Plate Shear Weld Shear 2.0

~CII A 2.1 Cell Axial and Bending 2.2 Cell to Base Plate Weld Weld Shear 2.3 Ce1 I to Cell Weld Weld Shear 2.4 Cell Seam Weld Weld Shear 2.5 Cell to Wrapper Weld Weld Shear Design Stress

~(si) 3504 10288 7631 6974 4403 34591

.899 15482 18389 1751 10299 Allowab le Stress

~(si) 23150%

23150%

23150+

9260 9260 46300%

1.0'1000 23150+

'21 94tt 18520+~

Margin of

~Safet 5.61 1.25 2.03

.33 I. IO

.34

.36

.26

.25

.80 Thermal Plus OBE Stress is Limiting SSE Stress is Limiting Allowable per Appendix XVII-2215 Eq (24)

Design Load and Allowable Load in Lbs is Shown Page 6 of 26

II

0 S.

With regard to the simplified 2-D nonlinear model, please respond to the following:

a.

Describe how the seismic loads were applied onto the model.

RESPONSE

The seismic loads were applied onto the model as simultaneous vertical and horizontal acceleration time histories.

b.

The analytical model of the fuel assembly used in this model was verified by comparison to fuel assembly test data.

The first test was a natural frequencies test to verify model's beam properties and the rotary spring stiffnesses.

The second test consisted of the fuel assembly in air impacting on a rigid surface to determine the fuel assembly grid impact stiffness and impact damping values.

Discuss how this model could be used to simulate the 3-D nonlinear structural behavior exhibited by the fuel rack.

co d.

RESPONSE

The nonlinear analysis is performed on a 2-D finite element model using a time history input of a horizontal shock and a vertical shock.

The linear model used in the analysis is a 3-D model which is run for two horizontal directions.

The loads for each horizontal direction are adjusted by load factors from the nonlinear

analysis, and thus include the effects of both a horizontal and a

vertical event.

The results of the two direction loads are then combined by the SRSS to account for the three seismic events.

Discuss how the time step of integrations was established in the analysis concerning the solution stability and convergence.

RESPONSE:,

A time step study is performed for a range of time steps.

From the results of this study, it is possible to determine the time step which gives a converged solution.

Refinement of the time step beyond this value willnotsignificantly affect the results.

Provide description of the friction element used in the model.

Elaborate on whether the friction element is capable of reversing the direction of its restraining force when sliding changes direction.

RESPONSE

The three-dimensional dynamic friction element is composed of a.gap in series with a parallel combination of impact spring and impact damper with a 'frictional spring orthogonal to the gap.

This element is designed to represent two surfaces. which may slide relative to each other, and may separate or contact each other.

This element is used to model the support pads and the fuel base.

This friction element is capable of reversing the direction of its restraining force when sliding changes direction.

e.

Describe the procedure used to calculate the hydrodynamic coupling masses.

RESPONSE

H drod namic 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.

Page 7 of 26

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5.

e.

CONTINUE This large hydrodynamic coupling force limits the deflection (and stresses) of racks that attempt to respond out of phase.

Thus the limiting condition is the racks responding in phase.

(Note that even if the racks could respond out of phase at their maximum displacement the clearances shown in question 4 are large enough to preclude rack to rack impacting.)

The seismic analysis for the Turkey Point racks treats the racks as if they are hydrodynamically coupled (move in phase).

The hydrodynamic coupling mass between the rack modules and the pool wall was calculated by evaluating the effects of the gap between the modules and the pool wall using the method outlined in the paper by R. J. Fritz.

("The Effect of Liquids on the Dynamic Motions of Immersed Solids" Journal of Engineering for Industry, February I 972.)

6.

With regard to the detailed 3-D linear-model, please respond to the following:

a.

Explain in detail how the load correction factors are derived.

RESPONSE

The nonlinear model accurately represents the non-linearities of the fuel to cell interaction and the interface between the rack base and pool floor (potential lift off and sliding).

As a result, the nonlinear model accurately predicts the loads at the rack to environment interface (rack base loads).

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

The load correction factors based upon the loads at the interface

'between the rack base and pool floor are used to adjust the overall stresses within the linear model in order to account for the nonlinear effects incorporated in the nonlinear analysis.

The load correction factors are determined'based on the ratio of the rack base to pool

.floor inter'face loads obtained in the nonlinear analysis to the loads obtained in. the linear analysis.

b.

Discuss how the seismic loads were applied onto the model.

RESPONSE

See response to 5.b of this report.

7.

Please provide detailed results on the overturning analysis.

RESPONSE

The nonlinear analysis showed that these racks did not liftoff the embeds during the seismic event, thus insuring the stability of the racks.

8; In Section 4.6.4(l), you discuss the fuel drop accident..

However, the discussion did not mention the consequences resulting from the fuel assembly drop accident on the pool liner and on the fuel rack structural integrity. Please comment.

RESPONSE

In the analysis it is shown that the energy of the falling fuel assembly is satisfactorily absorbed by the crushing of the fuel rack base plate and the deformation of the lower portion of the fuel assembly (lower fittingand lower portion of the-guide tubes and instrument tube).

The load transmitted to the pool liner is such that the stress developed in the liner does not result in perforation.

It should be noted that the analysis performed is conservative in that the fuel assembly is assumed to be under free fall (water resistance within. the cell, is neglected),

and it is assumed that no energy is dissipated by the breaking of welds which hold the base plate to the rest of the rack.

IN Il

8.

CONTINUED:

Rack deformation due to the drop accident does not compromise the subcriticality requirements as a Keff less than 0.95 is maintained.

9.

Please provide more'detailed information about the finite element model of spent fuel pool structure including the stainless. steel liner plate elements and how it is connected to the pool walls and foundation mat.

RESPONSE

The spent fuel pool is modeled using three-dimensional solid elements and the ANSYS computer code (Reference I). Figures I through 7 (submitted in response to Question IO) define the model geometry.

Due to symmetry along the long direction of the pool (north-south), only half the pool is modeled.

A minor geometrical dissymmetry occurs at the west end of the canal area where the spent fuel enters from the reactor building (see Updated FSAR Appendix l4E, Figure 3.I-3).

This minor dissymmetry has negligible effect on the structural behavior of the model considered.

Conservatively, the stainless steel liner is not considered in the model.

The model is supported vertically on a bed of compression spring elements representing the soil stiffness under the structure.

(Section 4.5.I of the Spent Fuel Pool Rerack Safety Analysis Report incorrectly states that the foundation's support is represented by solid elements.)

1 For symmetric loading of dead

load, hydrostatic

pressure, vertical earthquake, and spent fuel rack

loading, the nodes on the plane of symmetry are restrained in the directions perpendicular to this plane.

For the earthquake applied in the north-south direction, similar boundary conditions are employed except that the nodes under the base mat along the perimeter wal Is are restrained horizontally in the north-south direction.

For the nonsymmetric loading associated with the east-west earthquake, the restraints on -the nodes in.the plane of symmetry are released and the reactions from the symmetric load case are applied with appropriate east-west direction earthquake loads at these released nodes.

For load cases which include east-west seismic loading, the nodes under the base mat around the perimeter walls are restrained horizontally in the east-west direction.

Inertia loads due to the earthquake directly attributed to the concrete are input as distributed body forces.

All symmetric loads are applied simultaneously with the earthquake loads for each of the four directions (north, south, east, and west).

Thermal loads are applied as a separate. load case with boundary conditions similar to those for.the symmetric loads without horizontal. earthquake.

No additional loads are imposed on the structure in the thermal load case except for horizontal forces between the mat and the soil springs which represent the effect of friction between the soil and the base mat caused by thermal growth.

These individual load effects are combined as discussed in response to Question I O.

REFERENCE:

I.

G. J. DeSalvo and J. A. Swanson, "ANSYS Engineering Analysis System," Swanson Analysis Systems, Inc., July, I 979.

Page 9 of 26

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t IO.

Please provide a summary of the stress analysis of the spent fuel pool structure (walls, foundation mat, and liner plates), also the bearing stress of the soil and bed rock supporting the pool.

RESPONSE

The stress analysis was performed in accordance with the criteria included in the Turkey Point Updated FSAR, Appendix 5A,Section II (Design, Bases).

In summary, this criteria includes the following for.

Category I structures outside the containment; Y = I/9 (I.25D + l.25E)

Y = I/O (l.25D + I.OR)

Y = I/O (l.25D + I.25H + l.25E)

Y = I/O (I.OD + I'.OE I) where Y = required yield strength of the structures.

D=

dead load of structure and equipment plus any other permanent loads contributing stress, such as soil or hydrostatic loads.

In addition, a portion of "live load" is added. when such load is expected to be present when the unit is operating.

An allowance is also made for future permanent loads.

R =

force or pressure on structure due to rupture of any one pipe.

H =

force on structure due to restrained thermal expansion of pipes under operating conditions.

E =

design earthquake load

'El = maximum earthquake load'

=

wind load (to replace,E in the above load equations whenever it produces higher stresses).

Per the FSAR, design is in accordance with ACI 3IS-63. These criteria were used to evaluate the structure for effects from.the replacement fuel racks.

(Note that the Spent Fuel Storage Facility Modification Safety Analysis Report incorrectly states. that SRP Section 3.8.4.and.the NRC QT Position Paper were also employed in this evaluation.')

The analysis consisted of obtaining the state of stress in the pool using the analytical model described in the response to Question 9.

Dead weight, hydrostatic

pressure, and spent fuel rack loadings on the pool were considered separately and in combination with seismic, thermal, and wind loads to satisfy the following load combinations:

I.

I.25 (D+ P + L) with and without T 2.

I.25 (D+ P + L) with and without W 3.

I.25 (D+ P + L+ E) with and without T 4.

I.O (D + P + L + E I) with and without T Page 10 of 26

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I O.

CONTINUED:

where, D=

P=

L=

E=

El T=

W=

weight of the structure hydrostatic pressure of pool water weight of loaded fuel racks in pool design earthquake load, 0.05 g horizontally 2/3 (0.05 g) vertically maximum earthquake load, O. I 5 horizontally 2/3 (O. I 5 g) vertically therma I loads wind loads By using enveloping considerations, these load combinations were reduced to the following controlling load combinations:

l.25 (D+ P + L) with and without T l.25 (D + P + L) + El with and without T Seismic input loads for the analysis of the, pool structure were obtained using the res'ults of the seismic analysis discussed in FSAR Appendix l4E, Section 3.2.

Seismic loads for the new racks were taken into account in the pool structural evaluation.

Because, analysis has shown that these racks do not uplift during the seismic event, no added amplification factor for impact was considered.

Analysis showed that the seismic loading created a more severe effect than the combined effect of tornado wind and depressurization.

The thermal effect was obtained by imposirig a uniform thermal gradient across the solid elements.

In accordance with FSAR Section 5.2.3, the temperature of the inside face of the pool was taken as ISOoF while that of the exposed outside face of the walls was taken as 30oF.

The temperature of the bottom face of the slab was taken as 50oF.

This represents the effect after thermal equilibrium is reached.

Based on, the methodology suggested in Reference I, Appendix A,- this represents a worst case design condition.

Representative critical elements of the finite element model in the baqe

-mat and all walls were identified based both on high stress results and locations which result in severe loading.

These elements are shown in Figures 3 through.,7 and were further evaluated in the manner described below:

I..

Resulting stresses in elements caused by mechanical loads (all identified loads in the load case except thermal loads) were evaluated, by computing the capacities of the individual sections and comparing the capacities to the actual normal forces and moments.

2.

For the combination of mechanical and thermal loads, the sections were analyzed in accordance with the methodology discussed in Reference 2, Section 2.5.6.3.3 and Appendix A.

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CONTINUED:

A summary of the controlling stresses is provided in Table A for the locations identified in Figures 3 through 7.

These stresses represent maximum stresses for load transfer.

Controlling stresses occur in reinforcing steel, except for one instance where concrete shear governs.

The average bearing stress under the mat is 5 ksf,, with a localized maximum of 9 ksf.

This is below the design allowable pressure of IO ksf for the compacted limerock fill.

The average bearing stress on the bedrock, approximately 20 feet below the mat foundation, is also 5 ksf, with a conservatively computed localized maximum of 7.4 ksf.

This is below the design allowable pressure of 7.5'ksf.

This value accounts for the weight of the limestone backfill under the mat.

The liner plate was not considered to provide structural resistance in the analysis of the spent fuel pool.

However, a

separate analysis was conducted to determine the effects of

thermal, hydrostatic and hydrodynamic loads on the functionality of the liner system.

This analysis reviewed the buckling potential of the liner plate, as well as stresses in welds and embeds associated with it. The analysis sh'ows that there willbe no loss of function.

The reported analysis, as indicated above, was conducted'on the assumption of a maximum water, temperature of I80oF, based on the updated.FSAR criteria.

Recent evaluations using more conservative criteria indicate that the maximum water temperature may reach I83oF.

By comparing the results of the analysis performed for I80oF water temperature with that performed for 2I2oF water temperature (see response to NRC Question No.

8 submitted to Florida Power and Light via NRC letter of September 6, l984), an upper bound interpolation indicates that the maximum stresses reported'ould not be increased by more than 0.5 ksi if the water temperature were assumed to be I83oF.

This increase results in stress levels which remain within the specified allowables.

References:

I.

Commentary 'to ACI 349R-80 2.

ACI Committee 349 Report Criteria-for Reinforced Concrete Nuclear Power Containment Structure ACI Journal I972.

Page 12 of 26.

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"TABLEA LOAD COMBINATION MECHANICALLOADS MECHANICALBc THERMAL l.25 D + P + L l.25 D+P+L +E l.25 (D + P + L) + E + T Location N

(K/ft)

K-ft/ft K-ft/ft Mm/M N

M Mm (K/ft)

K-ft/ft K-ft/ft (3)

(2)

Mm/M Rebar Stress

@FY Rebar Stress Base Ma't I8. I East Wall 9.6 (Canal) 7.8 23

-22

-52 (fv = 82 psi) 2.95 I 3.2 I 6.7 27

- 2.36 25.0 '29.3

-43 I.80(4)

(fv = l42 psi) l.6 fs = l2.8 ksi (5) l.47 fv =. I42 psi (6) l.04 (4) 2.8 l~

l.04 (4)

East Wall 33.2 (Pool) l22 568 4.66 64.6 163 490 3.0 fs =35.I ksi f's = -9.6 ksi I.03 North Wal I I 9.8

-96.6

-l23 I.27 l3. I

-l40

-l51 I.08 fs = 27.I ksi f's = -2.65 ksi l.33 South Wall I 8.9

-38.5

-l92 4.99 23;0

-76. I

-I82 2.39 fs = 35.3 ksi(7) f's = l.4 ksi I.02 Middle Wall 28.5 22.1 209 9.46 2.6 32.5 2I8 6.7 fs = 9.6ksi f's = 9.0 ksi 3.75 N = Applied normal force on section M = Applied moment on section Mm = Maximum elastic moment (n'egative sign indicates compressive stress) fs

= Stress in tension steel f's

= Stress in compression steel fv

= Concrete shear stress NOTES:

(I)

Maximum elastic moment for a section with normal force N imposed on it.

(2)

Based on a cracked analysis per the methodology discussed in Reference 2, reinforcing steel stress is obtained directly.

Page I 3 of 26

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TABLE A (continued)

(3)

(4)

Due to the self relieving nature of thermal loads on reinforced concrete, the ratio of maximum moment capacity to actual moment cannot be uniquely determined.

As an alternative, the ratio of 4Fy to computed'einforcing steel stress is provided.

Since structural integrity is maintained'eyond the allowable stress for thermal loading, the actual safety factor is greater than the ratio reported.

Where shear stresses control, the ratio provided is that of allowable shear stress (conservatively taken as l48 psi) divided by fv.

This stress represents the maximum stress found in the top layer of reinforcing steel in the thinner center section of the base mat.

The top steel in this area is important 'for transfer of the tensile loads imposed by the lateral water pressure from the pool.

The bottom steel in the center portion of the base mat of the pool is used primarily for crack control.

Since the base mat rests directly on competent fill material, stresses in this bottom (secondary) steel resulting from thermal loads have no adverse effect on the ability of the pool to transfer load.

Therefore, the stress in the bottom steel is not included. in Table A.

(6)

(7)

As shown in Figure 6, this section occurs in the 3 foot wide by l8 inch thick section of the east wall between the two canal walls.

Because of the short span of this section, and the large ratio of section thickness to span length, the section does not resist loads in the fashion of a shallow beam; shear stresses control the section capacity.

Since shear stirrups are provided, the allowable shear stress in the concrete exceeds l48 psi.

The reinforcing steel on the outside face of this section is used only for crack control and is not needed to resist mechanical loads.

Therefore, the flexural stresses in this reinforcing steel are not included in Table A.

This represents an average stress (total force on the total section) over the top l0 feet of the outside face horizontal reinforcing, steel.

The result.

indicates that the section in general remains-below the minimum specified yield stress.

However, a maximum stress of 38 ksi has been calculated for the reinforcing steel in the top element of the wall.

Realizing the self-relieving nature of the thermal'stresses and further acknowledging that the section in general remains elastic; pool function and structural integrity are maintained.

Page l4of 26

QUESTION 10. (Continued)

~ggI-0 g sCP ply ML%Nlr446 NO SlXY tO z0 IUul l

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V ul FIGURE 1

Page 15 of 26

0

QUESTION 10 (Continued)

FIGURE 2 Page 16 of 26

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QUESTION 10 (Continued)

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BS g 93 PS

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NORTH WALL (Looking South)

SIDE, VIEW (Looking West)

LEGEND Stresses evaluated in horizontal direction Stresses evaluated in vertical direction Location of governing

( )

Number in parentheses combination number in stress reported in Table A indicates governing load table A.

FIGURE 3 Page 17 of 26

QUESTION 10 (Continued)

O 0'g 9C

/g 3 99 MIDDLE WALL (Looking south)

-(For legend, see Figure 3)

FIGURE 4 Page 18 of 26

1

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QUESTION 10 (Continued)

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~ 33 SQ SOUTH WALL (Looking South)

(For legend, see Figure 3)

FIGURE 5 Page 19 of 26

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,QUESTION 10 (Continued) 0 L<

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P

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BASE MAT (For legend, see Figure 3)

FIGURE 7

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I I.

Provide a sample calculation of the ultimate strength design of the critical connection between the pool well and, the foundation mat.

Have the reinforced concrete, and stainless steel liner plate been considered as a composite section in this analysis?

RESPONSE: 'he ultimate strength design, approach as defined by ACI 3IS was not used.

Conservatively, the acceptable ACI alternative of working stress, utilizing minimum specified yield strength for reinforcing steel, was used for all sections in the pool (including the connection between the wall and the foundation mat) as follows:

0 For 'each section. of the structure, section properties (thickness, reinforcing steel

area, depth, etc.)

are determined and the. section capacities for the combination of moment and axial forces are established.

The capacities are computed by use of the following equilibrium equations for combined moment and axial forces:

ZF 0:

(gjPkd) + A,'j,'

A,j, P

EMp ~ 0:.

()jPkd) e + + A,'j, e + d'eference 1

where Aj, e +d 0

2 b =

unit width of the section = l2 in d ='epth of the 'section from the extreme compression fiber to the center of tension steel d'=

distance from the extreme compression fiber to the center of compression steel factor where kd is the distance from the extreme compression fiber to the neutral axis of the effective section eccentricity from neutral axis to the assumed location of axial force to produce moment on the section total thickness of the section As = area of tension steel A'= area of compression steel fc =

concrete stress f's=

compression steel stress fs =

P=

tension steel stress axial force on the section (tension or compression)

Page 22 of 26

0

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CONTINUED:

This constitutes two equations with two unknowns (P and e). Moment capacity is computed as (P) x (e).

o For each value of k in the equations, there correspond values for P and e (and consequently M).

o The solution for the two equations is coded and the equations are solved for incremental values of k.

The resulting combinations of moments and axial forces for each section are tabulated as shown in Table A.

o The actual moment and normal force combinations from the structural analysis of the pool are computed and compared to the capacity of the corresponding section as determined above.

The section is considered-adequate when the actual moment and normal force combination is equal to or less than the moment.

and normal force capacity of the section..

o Shear stresses in the section are separately compared to allowable concrete shear stresses per ACI 3 I 8.

o Allowable concrete and steel stresses (compression,

tension, bending and shear) are not exceeded at the connection between the walls and foundation mat.

o The liner plate has not been considered to act in a

~

composite manner with the concrete, and has therefore been neglected in this analysis.

Reference:

I.,K.H.

Gerstle, "Basic Structural Design",

McGraw-HiI I Book Co.,

I 967.'age 23 of 26

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QUESTION 11 (Continued)

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l2.

Please discuss the design of the weld connections between the stainless steel liner plates.

RESPONSE

The l976 liner repair/replacement and acceptance criteria are discussed in Updated FSAR Section l4E.

The liner plate is not a structural element.

The loading from the stored fuel is transferred to the, concrete mat through the embedded plates.

The liner plate was not designed to act with the concrete as a composite section.

Monitoring trenches are provided behind the liner for detecting and'collecting any leakage.

Any leakage is directed to the waste disposal drainage system, thus preventing uncontrolled leakage of fuel pool water.

In support of the leak prevention function, the liner plates are welded to each other or to embedded plates using seam welds which were sized. for hydrostatic and thermal loads.

Vertical seams.in the wall.liner plates are square butt or bevel butt welds with embedded I/4" x 2" continuous bars serving as backing bars (Figures I and 2).

Horizontal seams in the wall liner plates are fillet welds between the plate edges and the embedded I/4" x 2l" continuous bars (Figure 3).

Seams in the floor liner plate are fillet welds between plate edges and embedded plates or.bars.

The surfaces of the seams are maintained flush with the floor by use of I'/4" square filler bars and bevel f i lier welds (Figure 4).

Page 25 of 26

0 0

QUESTION 12 (Continued)

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