ML20235F271
| ML20235F271 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Vermont Yankee |
| Issue date: | 05/18/1976 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Stello V Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20234C970 | List:
|
| References | |
| FOIA-87-40 NUDOCS 8707130306 | |
| Download: ML20235F271 (2) | |
Text
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!q Victor Stello. Director, Division of Operating Reactors n
3 f%RK I TORUS UPLIFT BOUNDING CALCULATION wt Il Oj Per your request, the Containment Systsas Branch and their consultants have performed bounding type calculations with regard to establishing a M
better insight into the Mark I-torus uplift pnenomena. The primary A
objective was to yield a better understanding of the potential energy 3
entering the pool during the early stages of the LOCR.
It should be N
noted that the values obtained as a result of this study represent Q
theoretical limits to the forcing function value rather than values h
that would ever be expected in the actual event.
Two separate approaches were used to enluate the bounding uplift force.
9 The initial method was based on a simple energy balance converting 100 Jj percent of the available incoming wetwell energy into potential energy.
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Based on this converted energy, a torus uplift for the reference plant 3
was calculated to be 60 feet.
It should be noted that this value is lj based on the complete conversion of all incoming air internal energy into 6
the potential energy form. The energy addition rate into the wetwell was
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obtained from a presentation made by GE during a reeting. These results N
were based upon the GE standard computer program used to compute wetwell y
and drywell pressure responses during a LOCA.
M The second method used to bound the uplift was based upon a conservative f
estimate of the maximum amount of available kinetic energy that could s
be cor sidered for the system. To determine this, movies from the GL 1/12 g
scale tests were used to establish an upper limit of 25 feet per second id1 forthe water slug velocity.
94 Aj The water slug mars was also conservatively assumed to be the entire water b) a slug above the submergence depth of the downcomers. This could be con-f sidered a bounding assumption since both the movies and simplified analy-W tical models of the uplift event indicate that the generated pool swell is based on a parabolic velocity profile of the pool. This indicates that only a fraction of the pool mass reaches the peak velocity of 25 feet per pd second. Based on these assumptions, a reximum kinetic energy value was j
J calculated and simply converted into potential energy. For the reference Q
W Mark I plant, this approach yielded an upper bounding uplift value of approx-LS imately 4 feet.
d il Tne reason for the large difference between the two bounding approaches is M
. _..._ _ _. due_,to._the assumption of the effectiveness of the_i_nco_ ming energy.
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$i-Victor.Stello MAY 181976 m
af2fj first case,100 percent of the incoming internal energy was assumed to be M
converted into potential energy.
In the second case, since movies of the 2-1/12 scale test were used as the basis of determining the potential uplift, pq a significant portion of the incoming energy necessarily had gone into p.y f.tettonal affects and minor eddy flow.
f As'a result of the study, it can be concluded that the uplift phenomena
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associated with the Mark I torus design represents only a small fraction 9
of. the total available internal energy during the torus uplift phase of.
d the event. A review of the Vermont Yankee uplift versus load sensitivity q.
curve indicates that a torus uplift in the range of 4 to 60 feet corresponds l
h to a load factor of approximately 2 or greater; however, we believe that a M
load factor of 1.5 represents, in our judgment, a conservative estimate of the uncertainties of the available test results.
A load fact.or of 2 appears g
to us. to be excessive' and unwarranted based on current information.
Signed by y.)
Gus lainas kl g) obert L. Tedesco, Assistant Director i
. of plant Systems jj Division of Systems Safety 4j erd cc:
J. Kudrick P
C. Anderson
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- M P. Baranowsky m
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