L-87-536, Responds to NRC 871023 Request for Addl Info Re Util 870612 Proposed License Amend to Permit Replacement of Spent Fuel Pool Racks to Ensure That Sufficient Future Capacity Exists for Storage of Spent Fuel

Responds to NRC 871023 Request for Addl Info Re Util 870612 Proposed License Amend to Permit Replacement of Spent Fuel Pool Racks to Ensure That Sufficient Future Capacity Exists for Storage of Spent Fuel

ML17221A558
Person / Time
Site:	Saint Lucie
Issue date:	12/23/1987
From:	Woody C FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
L-87-536, NUDOCS 8712280206
Download: ML17221A558 (16)

Text

ACCESSION NBR:

F*CIL: 50-335 AUTH. NAME WOODY, C. O.

RECIP. NAME REGULATOR INFORMATION DISTRIBUTION STEM (RIDS) 8712280206 DQC. DATE: 87/12/23 NOTARIZED:

NO St.

Lucie Pianti Unit i. Florida Poeer

& Light Co.

AUTHOR AFFILIATION Florida Poeer

& Light Co.

RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

DOCKET 0 05000335

SUBJECT:

Responds to NRC 871023 request for addi info re spent fuel pool rack descriptioni design

& analysis'er util 870612 proposed license amend. Multi-rack analysis shoeed that racks do not impact mails

& confirms its conservativeness.

DISTRIBUTION CODE: '001D COPIES RECEIVED: LTR ENCL SIZE:

TITLE:

OR Submittal:

General Distribution REC IP IENT ID CODE/NAME PD2-2 LA TOURIGNYi E INTERNAL'RM/DAF/LFMB NRR/DEST/CEB NRR/DEBT/RSB NRR/PM*8/ILRB 01 EXTERNAL:

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TOTAL NUMBER OF COPIES REQUIRED:

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DECEMBER S,S,1981 L-87-536 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gent lernen:

Re:

St. Lucie Unit I

Docket No. 50-335 S ent Fuel Pool Rerack - Desi n and Anal sis By letter L-87-245, dated June l2, l987, Florida Power & Light Company (FPL) submitted a proposed license amendment to permit replacement of the spent fuel pool racks at St. Lucie Unit I to ensure that sufficient future capacity exists for storage of spent fuel.

By letter dated October 23, l987 (E. G. Tourigny to C. O. Woody) the NRC Staff requested additional information in the area of the spent fuel pool rack description, design and analysis it needed to continue its review of this proposed license amendment.

Attached is FPL's response to this request.

If additional information is required, please contact us.

Very truly yours, C. O. Wood Executive Vice President COW/EJW/gp Attachment cc:

Dr. J. Nelson Grace, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, St. Lucie Plant I '7i228020b 871223' PDR ADOCK 05000335 P

PDR EJW I/028/ I an FPL Group company

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QUESTION

/11:

Provide the results of the multi-rack seismic analysis for racks (modules) Al, A2, Bl, and B2.

RESPONSE Pl:

The multi~ack analysis as described in the response to Question 3g, as presented in FPL to NRC correspondence, L<7<22, dated October 20, 1987 has been completed.

The parameters as specified in that response have been incorporated in the model, except that an additional analysis has been performed wherein the gap between the rack modules and the south pool wall has been taken as 5.5 inches to more closely represent the actual condition.

The imposed seismic loading is'SSE in the East+lest and vertical directions.

Table l presents the analysis results for an assumed coefficient of friction of 0.8 (the governing values from the 4.5 inch gap or 5.5 inch gap analysis are shown) and compares each parameter with the corresponding result from the single rack design basis analysis for rack B2.

Table 2 presents the same information for an assumed coefficient of friction of 0.2.

It can be seen from the tables that in the multimack analysis the racks do not impact'he walls, and that the results are enveloped by the design basis single rack analysis, thereby confirming its conservativeness.

TABLE 1 COF

.8 MAX. VALUES Item Rack/wall at girdle bar - impact load Rack/wall at base-plate impact load Rack cell wall to fuel assembly (per cell impact load)

Vertical load on pool floor from one foot Multi-Rack Model 0jl Of/

612. lb

.784 x 105 lb 3W Single Rack Design Basis Earthquake (B2 Rack)

OP O//

974. lb 2.231 x 105 lb Max. E-9 rack displacement at top of rack

.120 inch

.4238 inch

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TABLE 2 COF

=

.2 MAX. VALUES Item Rack/wall at girdle bar - impact load Rack/wall at base-plate impact load Rack ce'1 wall to fuel assembly (per cell impact load)

Multi-Rack Model 0ri 0ri 618.

3W Single Rack B2 Design Basis Earth uake 08 or>

Vertical load on pool floor from one foot

. 655 x 105 lb 1.378 x 105 lb Max.

EH< rack displacement at top of rack

.149 inch

.2088 inch

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QUES'IION 82:

Explain how the increased load of the spent uel pool due to the reracking changes the safety margin on the liquefaction potential of the soils beneath the fuel handling building?

RESPONSE

82:

The increase in the weight of the building resulting from the re-racking of the spent fuel pool will not reduce the safety margin against the liquefaction potential of the soils beneath the Fuel Handling Building.

The fuel handling building is founded on structural backfill which had been subjected to strict QC inspection to meet the design intent of providing adequate bearing capacity and dynamic strength to resist seismically induced loadings and liquefaction potential.

The re-racking of the spent fuel pool within the Fuel Handling Building will result in an increase in the weight of the building.

This increase will not reduce the safety margin on the liquefaction resistance of the soils beneath the Fuel Handling Building, but to the contrary, may actually improve or increase the subsoil liquefaction resistance because this resistance is directly proportional to the effective overburden pressure.

This phenomenon was presented by Seed and Idriss and others in the publication, Li uefaction of Soils Durin that soils subjected to static shear stresses prior to an earthquake will have a higher resistance to liquefaction compared to soils subjected to free field shaking.

Under the increased building weight, the static shear stresses in the soils will increase, thereby maintaining or even improving this liquefaction resistance.

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QUESTION /t3:

Demonstrate that in developing the simulated seismic excitation for the pool floor, the spectra enveloping requirement of SRP 3.7.1.II.a is met.

RESPONSE

/>3:

SRP 3.7.1 specifies that where.... "a recorded or specified time history is not available as input motion for seismic system

analysis, an artificial time history may be generated from the design response spectra for the purpose of carrying out a time history analysis".

It further requires that the response spectra obtained from'uch artificial time history of motion should "generally" envelope the design response spectra for the damping value used.

Furthermore, the SRP requires that the response spectra corresponding to the time histories should not fall below the design response spectra at more than five points separated by increments of not more than 10 percent of the coincident frequency.

The calculated response for the two horizontal, and one vertical SSE time histories envelope the respective design response spectra over the entire range of the fuel rack natural frequency spectrum.

QUESTION /l4:

Was pool wall flexibilityconsidered in the fuel rack analysis model 7

RESPONSE

i]4:

The pool wall is conservatively assumed to be a rigid unyielding structure with respect to rack-to-wall impact.

The analysis demonstrates that such impacts do not occur.

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QUESTION //5:

Provide a description of the EBS/NASTRAN and the POSBUKF programs and sample outputs.

~ Discuss how these programs were verified.

Also, provide a list of values of modeling parameters used in the pool structure analysis.

RESPONSE

//5:

(a)

EBS/NASTRAN EBS/NASTRAN is an enhanced NASXRAN program developed by Ebasco.

It not only has all the NASTRAN capabilities in structural and mechanical

analyses, but also has many additional features.

One of the additional features is the ability to perform concrete cracking analysis.

This feature incorporates a special'plate element which consists of a user specified number of layers, each having a different proportion of steel to concrete area, representing the presence of reinforcing steel.

Each layer will crack or reclose according to the stressmtrain relationships of the concrete and steel.

Thus a cracking pattern and stress redistribution can be determined.

One of the verificati'on problems listed in EBS/NAS'IRAN Verification Manual is included as Attachment 1.

The feature verified in the example is the plate bending formulation of the non-linear cracking analysis by comparing analytical results with experimental data.

Sample output from EBS/NASTRAN for the verification problem is also included in the Attachment.

(b)

POSBUKF POSBUKF is a program developed by Ebasco to examine the elastic post&uckling behavior of a flat plate subjected to thermal and lateral loading using an energy method approach.

The program determines the deflected shape of a buckled plate by minimization of potential energy, an'd from

this calculates plate stresses utilizing strain&isplacement and stressmtrain relationships for the particular case under study.

Fox a detailed description and verification of the program, as well as sample output, see.

Modeling parameters used in the pool structural analysis may be found in Subsection 4.6.1.2 of the St Lucie Plant Unit No 1 S ent Fuel Stora e Facilit Modification, Safety Analysis Report, transmitted via letter L+7-245 dated June 120 1987 '

QUESTION 86:

How was fuel assembly structural integrity demonstrated under seismic and impact load conditions ?

RESPONSE

$/6:

The concept of integrity of the fuel assembly in the context of spent fuel storage implies that the fuel rods do not crush or crack under impact loading.

The maximum fuel assembly to cell wall impact load at a typical spacer grid location is less than 2300 lbs, which is an order of magnitude less than the fuel rod crushing or impact resistance.

In experiments conducted on comparable fuel assemblies, loads in excess of 3400 lbs are required to produce plastic deformation of the spacer grids.

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r QVESIION 87:

How was the structural integrity of the Boraflex material and its cover plate demonstrated under all design conditions?

RESPONSE

87:

The Boraflex material is held in the vertical orientation by a stainless sheathing which provides full lateral support to the Boraflex sheet.

Both the sheathing and the Boraflex material are removed from any load paths that develop in the rack during mechanical or seismic loadings.

Therefore, the integrity of the Boraflex material is unaffected by the seismic or other postulated load conditions.

QUESTION //8:

How was the leah.-tight integrity of the pool liner evaluated?

Has consideration given to potential punching or tearing of the liner due to rack-to-floor impacts c

RESPONSE

88:

The leaktight integrity of the pool liner plate is confirmed by the fact that li.ner stresses and strains under design condi,tions are within allowable values.

See Table 4-3 of the St Lucie Plant Unit No 1 S

nt Fuel Stora e Facilit Modification, Safety Analysis Report, transmitted via letter L-87 -245 dated June 12, 1987.

Possible punching or tearing of the liner plate due to localized impact forces will not occur since the 1-1/4 inch thick base plates (minimum 13 inches square) provided under the rack support feet (9-1/2 inch diameter) will distribute such loads and prevent direct contact between the rack feet and the liner plate.