ML20211A001
| ML20211A001 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 02/13/1987 |
| From: | Olshan L Office of Nuclear Reactor Regulation |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8702190071 | |
| Download: ML20211A001 (4) | |
Text
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NUCLEAR REGULATORY COMMISSION p,
E-WASHINGTON, D. C. 20555
%,..... p February 13, 1987 Docket Nos. STN 50-454 and STN 50-455
-MEMORANDUM FOR:
Document Control Desk FROM:
Leonard N. 01shan, Project Manager Project Directorate #3 Division of PWR Licensing-A
SUBJECT:
BYRON SPENT FUEL POOL EXPANSION The enclosed documents entitled " Proposed Response to NRC Question on Multirack Behavior During a Seismic Event," dated January 6,1987 and January 13, 1987, were received via telecopy. Please place them in the docket file for Byron Station, Units I and 2, Docket Nos. STN 50-454 and STN 50-455.
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L. 01shan, Project Manager
Enclosure:
As stated cc:
Reg File PDR LPDR 8702190071 070213 PDR ADOCK 00000454 P
PDH
S. Putm:n - Jcnucry 6, 1987
.I F Proposed Response to NRC Question on Multirack Behavior During a Seismic Event Que_stion #4 How was the conservatism of the single rack model demonstrated?
The model appears to limit the amount of sliding and tilting of the rack between small gaps.
This would not account for potential pileup of racks against the pool wall.
Has this possibility been investigated?
l l
Response
l l
Additional analysis designed to obtain enveloping rack responses in terms of impact force between racks and the liner is proposed to respond to this question.
Multiple single rack analysis q
may be used to maximize the impact force between racks.
The boundary conditions in single rack analysis simulate the condition where the racks are out of phase.
The rigid stop springs at the end of the gap stop the rack and allow little energy to be absorbed by the boundary and maximizes impact force.
In reality the adjacent rack will not be exactly out of phase and will absorb some energy tending to reduce impact force.
The impacts between adjacent racks may tend to separate the racks thus increasing rack to rack spacing.
This condition may be simulated through analysis considering larger gaps than provicenly essumed so that the cingle rack analysis impact force bound the impacts was.ch may occur in the pool.
l If the racks spread apart in the pool they may come in contact with the pool wall liner.
The pool liner is backed by concrete and is stronger than the rack structure and thus is capable of resisting blows larger than the rack can deliver.
l 1
Accordingly, the rack which produces the highest impact force (12x14) will be reanalyzed considering an increase in gap size.
The gap size will be varied in 1/4" increments starting at 1/4" until racks do not impact.
In order to maximize rack response the fully loaded rack case and the eccentric half loaded rack case will be analyzed.
The above analyses will be carried out for the limiting coefficients of friction; g4 = 0.2 and 0.8.
The above set of parameters will yield an upper bound on impact force.
The maximized impact force j
will be used to evaluate the racks and pool wall liner.
H. Asher
- NRC telecopy K. Singh
- Holtec telecopy K. Ainger
- 34FNE S. Gubin
- 35FNW i
T. J. Ryan
- 28 R. Salsbury - 22 i
i I
l
So putman - January 13, 1987 Prohosed Response to NRC Question on Multirack Behavior During a $afsmic E
/
Question #4 l
How was the conservatism of the single rack model demonstrated? The model appears to limit the amount of sliding and tilting of the rack between small gaps. This would not account for potential pfleup of racks agafnst the pool wall. Has this possibility been investigated?
Response
bck pile up will not occur because seismic acceleration levels are below the threshold necessary for the large sliding motion of the racks necessary for that pile up.
It may be seen from the analysts of an individual isolated rack that the input acceleration levels are low enough so that sufficient displacement does not occur to obtain the free slidin!) behavior necessary to produce such a pfleup. The maximum displacement, inc' uding sliding and tilting of an isolated rack, is 0.122 inches. However, multiple rack behavior 4
may tend to separate the racks.
4 l
~
This condition may be simulated through analysis constdering larger gaps than previously assumed so that the sin!11e rack analysis impact force bound the impacts which may occur in the poo'.
Additional analysis designed to obtain enveloping rack responses in terms of impact force between racks and the Ifner is proposed to respond to this question. Multiple single rack analysis may be used to maximize the impact i
force between racks. The boundary condttions in single rack analysis simulate the condition where the racks are out of phase. The rigid stop springs at the end of the gap stop the rack and allow little energy to be absorbed by the boundary and maximizes impact force.
In reality, the adjacent rack will not be exactly out of phase and will absorb some energy tending to reduce impact l
l force.
l If the racks spread apart in the pool, they may come in contact with the pool wall liner. The pool liner is backed by concrete and is stronger than the rack structure and thus is capable of resisting blows larger than the rack can deliver.
p
/
Accordingly, the rack which produces the highest impact force (12 x 14) will be reanalyzed considering an increase in gap size. The gap size will be varied in 1/4" increments starting at 1/4 until racks do non impact.
In order to maximize rack response, the fit 11y loaded rack case and the eccentric half loaded rack case will be analyzed. The above analyses will be carried out for the Ifmitin coefficients of friction;p= 0.2 and 0.8.
The above set of parameters will ield an upper bound on impact force. The maximized impact force will be used to evaluate the racks and pool wall ifner.
SP:stk Copies:
H. A;her - NRC telecon.y S. Gubin - Ceco 35 FNW K. S' ngh - Holtec telecopy T. Ryan - 28 K. Anfger - Ceco 34 FNE R. Salsbury - 22
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