ML17194A036

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Summary of 810717 Meeting W/Util & NSC-Quadrex in Bethesda, MD Re Seismic Design of Proposed Spent Fuel Pool Storage Racks.Draft Response to Seven Questions Proposed During 810630 Meeting & Attendance List Encl
ML17194A036
Person / Time
Site: Dresden  
Issue date: 07/20/1981
From: Oconnor P
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
References
NUDOCS 8107280640
Download: ML17194A036 (21)
v • d • e


Text

".

UN!I,i;;D STATES

. NUG. _AR REGU[ATORV COMMISSION

~ WASHINGTON, D. C. 20555

.. *July '2o, 1981 LICENSEE:

Commonw~alth Edison Company

.FACILIT~:* Dresden 2/3 1

SUBJEC,T:

MEETING

SUMMARY

- JULY 17' 1981 MEETING Representatives of *commonwealth Ed.ison (CECo) and NSC - Quadrex met with the NRC staff on July 17, 1981 in Bethesda, Maryland to discuss the seismic design of CECo's proposed spent fuel p6ol storage racks.

The meeting*attendees are listed in Enclosure 1.

The following issues were discussed durin~ the meeting:

1. A draft of Commonwealth Edison's proposed response (Enclosure 2) to 7 questions posed by the NRC staff during the June 30, 1981 meeting was discussed with the staff.*
2. The NRC staff reviewer requested that CECo carry* our additional studies of the seismic design of the racks~ The additional analyses should consider:
a. Full racks to determine the maximum uplift obtained
b.

Use a number of Varied time histories

c. Use appropriatecoefficients of function determined from the referenced MIT st~dy
3.

CECo should substantiate the use of Hausner's method.

4.

CECo should evalLlate the effect of multiple pulses.

5.

CECo should provide a technical basis foi the effects of local deformation.

6. The staff asked CECo whether it would be possible: to restrain the racks to e 1 imi nate the possibility of rack uplift and subsequent impact.

CECo representatives stated that it is not feasible within the.schedular constraints -of. faci 1 ity operations to redesign the racks to eliminate the possibility of uplift.

~IG~AL,~;~Na J~ * * \\

Pa~nor, ~ger Operating Reactors Branch #5, DL

. JUL 311981

'OFFICE~ DL: ORB#S/PM

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SUMMARY

_Do_ckets.~50.-237, so~249..

.. *NRC PDRs (2) ***....

  • to*ca*l-PDRs** (2.)

TERA (2)

NSIC ORB #5 RF G. Lainas D.* Crutchfield.

P. *o* Connor H. Sinith J.: Olshinski

  • J. Heltemes B. Grimes

.* OELD OI&E (3).

ACRS (10)

S *. Norris T~ Alexion

  • T. Wambach*

W. T. Russell R

~. A. Hermann

  • K. Herring
  • R. Janecek, CECo L. DelGeorge, CECo J *. Laird Woldridge, CEto

. Quazi A. Hossain," Quadrex Corp~.*.*.

C. C. Tank, Quadrex Corp.

Isham,; Lincoln ti* Beale*

  • Counselors at.. Law One First National Plaza,. 42nd:*Floor Chicago. Illinoi~. 60603.
  • Mr.. Doug Scott.
  • .Plant Superintendent Dresden° Nuclear Power-Station**

Rural Route /ff Merri s,: 111 i noi s> 60450:

Natural Resources< Defe~se* Council 917 15th Street, N.... w *.

Washington, o. c... 2ocio~

u. s. Nuclear Re.gulatory Conunission*

Resident InspectorsOffice Dresden Station*

  • RR /ff Morris;. Jll i'noi s... 60450..

.* Mary Jo Murray

  • A$s~stant: Attorney General Environmental Contl".ol Division***

188 w.: Randolph Street*

Suite' 2315.

Chicago, lllinois.60601 Morris Public: Library*.*

. 604* Liberty Street:

  • Morris~- I 11 i noi_ s
  • 6045.1

. Chairman Board of Supervi so.rs of Grundy County Grundy County Courthouse Morris, llli~oi~ 60450 John F. W9lfe, Esquire-3409 Shepherd* Street*

Chevy.Chase, Maryland 20015 or. Linda w *. Little:

500 Hermitage Ori ve*

Ralei~h~ Nort~ Carolina 2761?

  • t ***. : *-*--,.---~*

-~-- -*"-- ****,

r*

Ill fnois. Department: of. Nuclear Safety*

1035 Outer Park Drive, 5th Floor Springfield, I l li noi S* 62704 O. s. Environmental Protectfon*Agency

. Federal Activities* Branch Region.- V Office:*

ATTN:*

EIS COORD.INATOR' 230* South Dearborn* Street Chicago~ IllinoiL 60604*

Dr. Forrest J. Remick*

  • Mr*. L. De lGeorge.

. Director of Nuclear Licensing

. Cb!fllTlOnwea lth Edi son Company Post Office Box 767 Chicago, I 1 linoi s 60690 Susan N *. Sekul~r

  • Assistant Attorney (lenera.1 Environmental Control Division 188 W~ Randolph Street*

Suite 2315 *

  • chicago, Illinoi~ 60601
  • .*Mr*~ b. R *. Sti chnoth*
  • President Iowa-Illinois Gas and*

El ec.tri c Company 206.. East Second. Avenue*

Davenport,_ I.owa 52801.

Hr.- Ni ck Kai; vi an~k~s *

.. Pl~nt Superintendent Quad Cities Nuclear Power Station

. 227.10 **- 206th Avenue - North

  • Cordov.a, Illinois 61242 M~line Public Library Su4 -- 17th Street

~---------~----------*. -- -... -----** *--.. * -*-- -*...

ENCLOSURE l :

MEETING' ATTENDEES.

DRESDEN 2/3 c

SPENT FUEL POOL MODIFICATIONS

_Paul O' Connor*9; ORB#5/DL Tom Alexiqn,. ORB #2/DL' Quazi A. Hossain, Quadrex Corporation*

C. t. Tang,, Quatjre~ Corporation Robert F. Janecek, CECo Louis 0. DelGeor_ge, CECo Tom Wambach, ORB #5/DL.

J. Laird Woldridge,~CECb W. T. Rus~ell; SEPB/DL

    • R.* *A. Hermann, SEPB/DL K. Herring~ SEPB/DL
  • -:--=;....:..:.;...,~. --*.. '-*

~ --;----. *-*---.. --.

    • ~*-... ** *a*

'ENCLOSURE 2.

~---.*

~ *: (

REQUEST' NO. r Revise~ Tables: 304-2 and* 3.. 5-2 to r~fl ect *fortes. and: stresses in both the rack

.. and pool structures consid.ering a:l l effects:. ~f impact. for both. the. OBE and: the.

SSE~

Include* both t~e gross and. local' effects of impacts.

Cl early sunmari ze

  • the: bases for all load combinations and corresponding a-lTowabl e stresses for both th~ r~vised a~d e~istin~ tab~es.
  • Response**

a)

Rev~sion of Tabl~ 3.4.;.z Table* 3.4-2 provides a! summary of* stre~~es.in raCk components computed with fixed"'.'base assumptions. **This con~ition does not exis.t dur.ing impact~

. Effect of rack-to-rack and rack-to,-wa.11 impact on the* rack was eva 1 uated in response. to NRC 1 s Ques.tion 1. arid submitted on June* 8',..1981.

In that evaluation, i_t was. shown that loads and stresses obtained from fixed.-base' ass~mptions are n'i:>t ex~eeded during rack-to-rack and rack-to-wall impact

. (except loca'l pl'astic_ defonriation)'..* *

. R~ck.;.~o-pool floor impact _condition has been.evaluat~d*~* The evaluation results *are" surrmariied *in Tables 1-1 and: 1-2.

Comparison of these results *.. *

  • . ~ith those in Table 3A-2 shows. thatfixed-base c~ndition results dominate..
  • Thus,. the:* consideration impact effect did_ n_6t. necessitate, revising Table 3.4-2; b).Revision of Table 3.5~2.

j Table 3.5-:-2 provides a summary of stresses in pool floor and walls and the grid spanning. the trench* in the pool.* floo*r.

The pool floor moments* and shears shown in. this tabi'e were* computed without.

considering any impact load from racks.

The pool floor was reevaluated con-*

sidering. the* rack i~pact loads~ The *results of: this evaluation are shown.in Tabl~-l-3, which* replaces-th~pool.slab pa.rt of*Jable* 3~5-2~ Values in Table. 1-3 are *based.on*0~76 11 upllft of.the* loaded. ~ack~ *The* amount of ki~etic*

. energy abs.orbed by the floor slab was e;omp~ted by idealiZing the rading rai:k

as an-inverted: pendulum w.fth a;: maximum,_upJift o{ a~ 76" and* deducting* the

  • effect* of the* inertia. of the impacted pool slab.

The capacity of the* pool slab is governed by shear and was com'puted. assuming a 15%. increase in the compressive strength of the concrete*. due to aging.

The roaking behavior of the. *racks, is yery random in nature.. The' initial period* of the rocking rack, when idealized~ as an inverted pendulum, was.

.. coinpu,ted to be~ about l~ 5 cps. ( frequencY: increases as. rocking: continues,

.but the amplitude also decays rapidly) *. Because* of this random and slow rocking. motion, it is highly improbable* that more than half. the racks in the pool will be impacting on. the: pool floor* instantaneously.

Values listed in Table. l-3 show. t.hat the pool 'slab is c:apable of withstand-. *

. ing the additfo.naf impact loads from racks.~

The sources of conservatism in calculating the ~alues in this tabl~ are as follows:

a)

As -was shown in our* earlier* response* to. NRC' s Questi o*n No. 2 (June 8 submittal),.the use of 0.76" liftDff is conservative (see response to Question, i, this set).

b)

The input acceleration timehistory used in the nonlinear sliding analysis is equ_a 1 *to.1.1 times the actua 1 value.

c)

Assumption of half of the racks impacting simultaneously on the pool floor*

is judged to be conservative.

Pool walls values li~ted in Table 3~5-2 were based on wall-braced ratk configura-tion which e~erted lateraJ seismic loads on the ~alls. For the proposed free-standing racks,. no such lateral loads are present. *The effect of rack impact on

  • the wall was evaluated and the results presented in the response to NRC's earl.ier Question No. 2 (June 8 submittal)*.

Only SSE. load *combinati.on was considered.

there..

  • Evaluation of QBE load cases is underway after completion of which the Tab 1 e wi 11 be revi se.d.

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

Stresses, in the> Grid spanning t.he trench w.;-1r remain' unchanged',. s-ince* the, loads on rack }.egs computed: with fixed-base* assumptions are higher than those computed from rack-to-pool floor *impact consideration.

    • -* -*--*-~--
  • Cases 1

2 NOTES:

-e Table: 1-1 Rack Leg* Forces: Due to Rack* Impact on Poor Slab'.

Corner

  • oescri pti ans Leg (Kips.)

.All the racks" inside pool 76.T Half the racks* inside* pool.

86*. 5 One rack ins; de: pool 96.0 From original seismic.

179.8 analysis of rack*

e

\\l~f[

Middle Leg(Kips)

Remark 95.8-*

  • 10a.1 (1) 120.0
  • 20s~ g
  • i. -Computed us.ing energy ba 1 a nee method consi°dering the strain energy of:

(a) deformatiOn of the pool.slab as a plate; (b) local defonnation of the pool slab under ra.ck legs; and (c) defonnatfon of the rack.

  • ...,.---~---*
  • -._ __ ~

Rack Component Tilbe *wa l T Fuel Support.

Plate

  • Filler Plate Bas.e Grid Rack Leg Tabl 1:'..1-2 Stress in Rack Component Due to*

Rack Impact on Pool Slab Load*

CritiCal Allowable:

Com.bi nation-.*

Stress Type*.

Stress (ksi) 0+8+['

  • Membrane

.2T. 9 O+B+E

Membrane.

2T.9 O+B+E'.

Membrane*

27.9 D+B+E' Membrane 2T.9 O+B+E!

  • Memhrane 27.9 Computed*

Stress. (ks i )

15.13.

. 11.22 14.1 2.13 12.74

/

SUMMARY

OF.* POOL SLAB EVALUATION LOAD CASE (1)

LOAD CASE ITEMS

1. 4D+ 1. 4H+ 1~7L+1. 9E D+H+L +E.'

R~MARKS HALF RACKS.

ALL RACKS HALF RACKS ALL RACKS IMPACT IMPACT

. IMPACT IMPACT

<Equivalent unifonn load without impact (k/ft2) a.29 8.29

.6.16 ti, l6 I

Computed equivalent uni-form Joad iricluding rack impact (k/ft2)

  • 11.43 13.86 9.30 n.n (2)

Allowable uniform load (k/ft2 )

' 13.92

'13. 92 13.92

'13.92 (3)

NOTES:

1.

Incomp4ting *the rack impact load d4ring O~E,.it was a~sumed that l.9E is ~qual to E*' !

2~

Co~p~ted using energy-balance method considering the strain energy of deform~tion of the pool slab (both local defonnatfon *and deformation of the slab iiS a plate were'*corisidered) and the

. rack.

3.

Slab c,apacity was governed by shear due to djagonal tension and was computed on the basis of average ~llowable sheir acting on a critical section perpendicular to plane of the pool slab and located so that its perimeter.is a,distance d (effective depth of slab) froin ~dgeo*f the pool ~lab. The compressive strength fc.of the concrete was.increased by 15 pe_rcer:it ciue tp agin9.*

Table 1-3

. I i

i

. I

.e

  • .REQUEST" NO.. 2 Provide a* summary of rack support.1 eg *stresses (forces) for various amounts of fu~l stored in the pool.

Response

A sulTDllary of rack* leg. forces for various amounts of fuel stored* in the pool

  • 1s showri in Table* 1-L

."*---:.:..:...~*-*. -----***., -****-***---

URAEl.

. REQUEST NO. 3 Surrmarize the rack stresses for the* case where the: fuel rack is considered flexible with re~peci to the p~~l flooras:compared to those resulting from considering the floor flexible as compared to the racks, as assumed in pre-vious-analyses:.

Response.

Table 1-2 surrmarizes the: stresses. resulting from the rack impact on pool floor slab. These stresses were computed by proportioning_ the* seismic stresses using the* rati~ of the rack leg. load from impact analysis ~o that from the seismic analysis.

        • --*~~-**--
  • . REQUEST" NO. 4-Summari ze-the-differences and the* effects o,f the differences between your con-sideration -of hydrodynamic mass and _that. given in the* Branch Technica*l Position "OT" Pas itfon for Review and Acceptance* of..S_pent Fuel Storage and Handling
  • Applications".(forwarded to all licensees in April 1978).* In add.ition, verify that 1%.and, 2% damping were used in your OBEand SSE analyses, respectively, in atcordanc~ with your FSAR with no inc~ease in dampi~g assumed for submergence

.of th_e racks-..

Response

Hydrodynamic mass vaiues used were based o~ thi assum~tion that a single rack is placgd irr an infinite pool.. T~e weight of this hydrridynamic mass was 48.54 kips.

If only the mass of water available a~o~nd the rack is considered (assuming conservatively a 9 11 space-between 'rack a~d wall, and _2.5" gap between racks), the weight of the hydrodynamic mass is reduced to 5.96 kips. This change would increase the fixed-base *fundanienta l frequency of the rack from*

10.16 cps,-to 11.76 cps.

This reduction in mass would also reduce the stresses, but ~his has not been computed~

____ ;_...., **---:.......~" *----*

.REQUEST NO. 5

  • Provide a summary of the forces induced: in the pool floor structures assuming all racks impact in phase* in* addition to the.case of 1/2 the* racks impacting as pre*viously, considered..

Response

See Table r~J.

-*-...... *----~ _.:..-,... -*.*...

DRAfl REQUEST NO. 6 Your response to Ques~ibn 9, attached to your May 30, 1979 response to NRt questions-, provided floor* response spectra, which you then-- _stated *were used in tne analysfs of.the r~cks.. Your current position is that this response was erroneous.. Therefore, describe the time history used in. previous analyses and provide the corresponding response".spectra.

Quantify the effects of con-sidering "peak broaClening" _of these spectra.. Describe and justify all your analysis assumptions.

Response*

The time-history at the pool floor level obtained from the original building seismic an~lysis was used~ The ~esponse spectra of the two time-histories (one for E-W direction, one for N"".S _qirectfon) are shown in Figures s~1 and 6-2.

The effeci of 10% broadenirig these spe~tra are show~ in Figures 6-3 and.6-4.

The broadening of the E-W spe~tr~ increases. the response at.:the frequency of

  • 10.16 cps (short direction of the rack) -from d.704g to 0~718g~ The broadening of N-S spectra increases-the response at the frequency of 13.33 cps (longer direction of the rack) f~om 0.475g to about 0.509).

However, if this is con-

~idered. with the reduction.of hydrodynamic. mass (which increases the-fundamental frequency.from 10.16 cps.to* 11.76 cps), the* effect is negligible..

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DRAFT~

  • REQUEST" NO. 7' Verify *that the* 3.46 factor* of conservatism* in. the derivation of energies from the peak v~iocities resulting from* your nonlinear* rack analysis (as described in your response to Questicin 2, :attached to.your June 8, 1981 letter to the NRC) *;"s indeed* reliable in youroverall analysis and not just

. a quirk* of this. one particuJar nonlinear analysis~

Response*

A new.nonlinear sliding. analysis_ w~s perfonned using the* same mode.l as. before, but modifying the* time: steps of the time history by: 15 percent such that the peak of the response spectra shifted towards the rack fundamental frequency.

The factor of conservatism computed from this analysis result is shown in Table 7~i.

Compari~6n with earlier number*s~o~s re~arkable consistency~

Even though such excellent ~onsistency may not always. be present, energy J

balance methrid ca~definitely be considered conservative:*

I ;

-- --------. -* 1-*

I i

  • DRAFt Table T.. 1 Li ft-off of Empty Rack Li ft-off from Lift-off by Factor of
  • case**

Nonlinear Energy-balance Conservatism Remark Analysis 1

0.56 2.-20 3.93 (1) 2 o~85 3.38 3.98 (2)

NOTES:

1.

Using 1.1 t1rnes the. actual* time his.tory at the pool floor.

. 2.

Assuming that ~he frequen~y of the plan~ building is increased

. by 15%.

.....

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