ML19254D196
| ML19254D196 | |
| Person / Time | |
|---|---|
| Site: | 07002623 |
| Issue date: | 09/04/1979 |
| From: | Jeffrey Riley CAROLINA ENVIRONMENTAL STUDY GROUP |
| To: | |
| References | |
| NUDOCS 7910220491 | |
| Download: ML19254D196 (5) | |
Text
NRC PUBLIC DOCOliEh'T kOOM
'EC cu UNISD STcT35 0F AMIRICA I;UCIL.R REGULATCRY C0:2JISSION
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A In The Matter Of
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MIN 1L
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Di.iEE P C..: a C O:2ATf
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Docket No.
70-2523
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FA=a" N + to Operating License
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SNM-1773 for Oconee Spent Pael
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'fransportation and Storage at
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go McGuire Nuclear Station)
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4,17 ib II SN ~ 673 7 Q
hi T:~2 CASK DROP PROBLEl
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TESTI:GDNY CF JES63 L.
NILEY
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An anonymous allegatica was made to the NRC that
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=ade an " accident analysis which indicates that a dropped fuel shipping cask can fall into the ScGuiry spent fael pool under certain conditions.
DPC representatives have informed the NRC and stated in the FSAR that the fuel cask cannot fall into the pool."
NRC IE Investigation Report 50-369/78-10 and 50-370/78-4 discusses this catter and finds an " apparent conflict between eristing calculations and FSah Sectic 9.1.2.3 8hi66 is identified as Unresolved Ites 369/78-10-1 and 370/78-4-1."
R. L. Baer request ed addition'al information frca Applicant,
Ihclosure I, letter of Feb. 6, 1979.
This was to include "the results of an analysis, including the assu=ptions, analysis,
analysis methodology and drawings; that evaluates the consequences
_of dropping or tipping or conbination of both, of the Oconee fuel cask in the McGuire spent Pael handling building. "
"The analysis shoulddeconstratethatsuchaneventwill~notcabedaageto st ored spent fuel or safety related systens or co=perents is the McGuire fuel handling building."
spplicant 's response is 2
075 7 910220 M /
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P00RORGINil given in lett er fro. U. O. Prker, Jr., to E. 2. Denten, :Irch 2,1977.
I have read this correcpondence and nahe the follouing co ncnt.;
The rdational noned of a fnci cask in a tipping accident will depend 5 the cc:r.T.rsion of the potent:-1 crergy presed ct the poi--t of cask release frca the cr=e (see Case #3, DPC, IIsr. 21,1979). Using the ficor elevation as the reference level for potential energy that icvel of energ ccn be calculated for gecific ciretc-dances. I have calctistcd the center of gravity of the ecch (e.g.) and found l.t to be en the cc k avis 105"(3.758) fren the plce of the base. I han relied on irforr. tion pro.ided in the IES-h Certdicate of Cc: p2icnce :To. 6693 The cask weight is given as about 50,000 lb. The nc::i..= diancter at the base is 50"; of the neutron shield
~
tenke, h0"; and of the gc.:-a shic1d 30".
The neutren shic1d tanks a e assuned to crush in the tipping accident.to gprc:inately the dianeter of the gerna shield.
In a tipping accided the louest ele.7 tion of the c.g. in encet:ntering the fttel pool vall vill be 15" (1.25t). The avcilable energy for g trction of the cask till be the potential energ for the specific ci c= stance less thd for the ic"ect elevation of the c.g.
Ciret:nstance Potential Ene: y Available Enerc r Bare ht above floor 637,500 ft lb 575,0C0 ft lb Ma:inu:t elemtion 522,957 3 ace 21 E " abcw floor 5c5,hl7 Initici DF0 c seption h25,0C5 3cre on floor h37,500 Cask heri::cdal en floor 62,500 n
a n
IIeutron ttnk crushed, cack at rect 2
076
3 Available energy uill, during the tipping process, be conve:ted to kinetic ener g.
Energ recuired to cr.:sh the neutron tan': uill reduce the kinetic energ by tMt r.ount. The kinetic energ for gyrating _the cask
~
iho the fuel pool will be at a r.a:d:::: at the instad, the cask is hori::cdal oh the fuel pool vall and the c.g. is at an c' evt. tion cf 1.23, Energ7 dissipated b-inelastic i pact with the floc and ene gy used in crasFing f
the i: pact liriting structure of the base.M also be subtracted from the trittan7 avaliable energ.
The r.oct critical ci cunstance for the tipping accident, that is the leact conservative, occurs :&en the base is at floor level r.d the e.g. lies in the pir.e of the pit wall (see Sketch #3, DPC). In this position the available energy is 355 lower than at an elevation of the base of ht.
The base is designed to cr:f the rei;;ht of t'he cask and is correspo:xi-ingly cubctantial. Based onITS d aning 310078 (CISG Eiihith? ), Section 3-3, the cask pedestal structure has a rrexi=un e'fective dir.eter of about 36" and a rini.~.21 effective dianete-of about 30".
If, in a tipping accided, the pedestal suppe:t:: the cask, no allevan':e can be r2.de for energ7 absorption by the i. pact 1dniter for no defor-.ation d11 occur.
If the cask drops before tipping, and the pedestal inpacts the floor, the energy absc ption of i. pact till be mind cl. Only if all of the pedestal is our the pit will appreciable energ7 absorption cecur en f: pact.
In this case it is 2ike27 that the peri-p5.cral, i.gact limiting poMicn of the bc:eri21 so deforn as to deflect the cack into the pit.
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i Consecuently the tipping ciret:. stance uhich is noch critic 2, in the sense that the ene g7 avtilable for tippisg tF" be 1ccd, is that in thich the base is et floor level and c.g. is in the plene of the pit unll.
2 077
-h-Piveti-g tcuard the fuci pool fron this position, uhen the cask is horicental and suppo:ted by the fuel pool m21, the c.g. uill be 1.03n en the pit side of the vall. If the cast had no kinetic energ it uould fall bcek into the
-pit. The kinetic energ it has v7, houever, cause it to rotate about the fuel pool edge of the wall. What must be deterrdned is uhether the kinetic ener g at this nonent is sufficient to rotate it far enough to drop into the pool. Conservatively this would require sufficied continuing rotation for the c.g. to reach the plane of the pool tr77 The pctential energ at this point, assuning all kinetic energ has been used, vould be 166,5h2 ft Ib and the elevation of the c.g. 38 plus 1.05".
This would require that 615 of the init9'17 av ilable energ nould have been used in crudd.ng the neutron shield tank. Absolute 1;r no evidence has been offered as to hou much energ would be required to c: ash the tank.
More conseri,ative assu.~.ptions uould include having the cask tip initiate with a larger displacment of the cask axis fren the plane of the pit u-".
If that displace-.ed were lyn, the e.g. of the cask in the horizontal position would be 1.25" on the wall side of the plane of the pit wall.
The energ required to rotate the cask so that the e.g. nould reach the this t. uld happen ::ith the plane of the pool vall would be 157,708 it lb.
t dissipa. tion of as :n:ch as 63% of the initially ava.ilable energy. If the displacment of the af._s fron the plane of the pit :m" uere init4,"7 2On the e.g. in the hori c=tal position would fc.11 h.68" on the pool side of the pit wall. The ene g require to assare drop ido the po31 would be reduced to lhh,695 ft Ib pe'-.itting the dissipation of as nuch-as 665 of the initially available ener g.
2 078
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For the noct critical case, foregoing, the angle 9 (see DP0 Sketch f3) o is 65 Fe the more conser stive cases the angle would be, respective 4, 66.4 ~- "~ M. a' m.
It is not certain that adninistrative cedrols u4 provide a sufficied safer:cd,(L?C Sketch ph). An excess of travel along the final pcrtion of the proposed path night reasorably be expected to defom the handrail, which is chsractriced as a " visual berrier, na'd.n; a tipping accident possible n
by rid.r.g the floor en the rail side accessible. A substantial phy=ical barricr. over the pit / pool wall would nake tipping of the cask into the pool a phycical inpossibi2ity.
Such a barrier would rise 128 above presed floor level. As assenblies are to pass from pit to pool,either a fixed gap, in that ba.nd.er, depe"d4mc on design specifics, or a novable gate in the be.rrier ::culd be required.
"ifective safegur.rding agenst cask drop ido the fuel pool is essential to providdr.g positive assm.ce against a criticality accident in the fuel pool.
At Chelette, N.C.
sept h, 1979 Hand-deliwred to W47'4 n 1. Porter of this dche.
Cppied to ':rJ!.ance of service 31st by deposit in the U.S. nail of this date.
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u-(Jesse L. F.ileyrepresentingCE.~./
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