ML20195F892
| ML20195F892 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 11/17/1988 |
| From: | Bailey J GEORGIA POWER CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| GN-1509, NUDOCS 8811220399 | |
| Download: ML20195F892 (5) | |
Text
r Georgia Power Corrpany Post Offico Bok 282 Wayn3bora Georgia 30830 e
, Telephone 404 554-9961 404 724-8114 Southern Company Services. Inc.
Rr.1Off ce Box 2625 gm h
B trmngham Alabama 35202 Te'ephone 205 870-6011 Vogtle Proj.ect November 17, 1988 U. S. Nucicar Regulatory Commission File: X7BC35 Attn.: Document Control Desk Log GN-1509 Washington, D.C.
20555.
NRC DOCKET NUMBER 50-425 CONSTRUCTION PERMIT NUMBER CPPR-109 V0GTLE ELECTRIC GENERATING PIANT UNIT 2 SPENT FUEL RACKS Centlement During the structural audit of October 4-6 of this year, relative to the spent fuel racks, Georgia Power Company committed to submit the results of additional analyses that (a) provide the value of the maximum line load at the top of the rack which the modules can withstand and (b) provide the value of the averaged concrete bearing pressures for stored fuel, including the locii of the maximum allowable movement of the support spindle from the nominal position. The results of these analyses are summarized in Attachment 1 to this letter. to this letter is a summary of margins in critical locations for the safe shutdown earthquake loads. These margins were discussed with the NRC during the structural design audit, and we are using this letter to submit them to the NRC.
During the structural audit, the NRC and its consultants reviewed portions of Holtec International's proprietary seismic design report. At that time, the NRC consultants noted that additional review of this report might be needed.
We luvo arranged to have this information availabic on November 21 for further review by the ?RC and its consultants.
The confirm 1 tory multi-rack seismic analysis that was requested during the structural audit is progressing. We expect the results to be available for submittal to the NRC before December 21.
as11220399 [ h )DC 25 PDR AD N P
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U. S. Nuclear Regulatory Commission File: X7BC35 November 11, 1988 Log:
GN-1509 Page 2 If there are any questions concerning this information, please feel free to contact me.
Sincerely,
- b./
- J. A. Bailey Project Licensing Manager JAB /sm Attachments xc: NRC Regional Administrator NRC Resident Inspector C. K. McCoy P. D. Rice J. P. Kane R. A. Thomas B. W. Churchill, Esquire J. B. Hopkins (2)
G. Bockhold, Jr.
R. J. Goddard, Esquire R. W. McManus Vogtle Project File 1655V
l ATTACHMENT 1 1.
Determine the allowable value of the line load which can be imposed on the top of the high density racks in the Vogtle Unit 2 pool.
The allowable value of the uniform line load applied near the top of a Vogtle fuel rack module is computed to determine the impact load bearing capability of the modules.
It is recalled that these modules have been shown to maintain sufficient inter-module and module-to-rack impacts to preclude any lateral impacts. However, an assessment of the lateral load besring capability provides a measure of the ruggedness of the hardware.
The analysis was performed in the manner of similar analyses by Holtec International for Byron Units 1 and 2, Braidwood and St. Lucie Unit 1.
The maximum allowable load is defined as one which will initiate plastic deformation or collapse of the flux trap space in the active fuel region.
The analysis yields the allowable load to be 5064N, where N is the number of cells impacted. Thus a 10x11 module, wherein 10 cells face the impacting surface, has an impact load bearing capability of 50640 lbs.
2.
Demonstrate that the bearing pressure on pool liner during seismic conditions is within the plant licensed limits.
Presently, licensed maximum bearing pressure on the pool liner for factored load condition is 4760 psi.
This allowable is reduced to 50%,
2380 psi, for the regions of concrete which lie within 5 inches from the leak chase centerlines.
According to the rack module layout in the Vogtle West Pool, certain support spindles are quite close to the leak chase. The nearest distance between the support spindle centerline and leak chase centerline being 7.5 inches.
In order to diffuse the load over a wider area, 2" thick bearing pads are interposed between the liner and the support spindle.
As the prelude to the finite element analysis, the maximum factored l
load during the OBE condition was computed to be 327 kips. The OBE condition factored load was found to be greater than the SSE condition i
and therefore was osed as the basis for analysis.
For purposes of comparing the factored pressures to the allowablen, the loaded area was divided into two regions.
The circular patch directly under the 7.5" diameter (5.5" diameter spindle is extended to the l
l bearing pad central plane to a 7.5" circle) pr.tch is labelled Region A.
Most of this pstch is in the 4760 pst zone, but a portion may lie in 2380 psi zone.
The appropriate area weighted average is used as the allowable for Region A.
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ATTACHMENT 1 Page 2 Region B ie defined by the concrete region in the previously mentioned 5" zone (allowable pressure 2380 psi).
The finite element analysis gave the following final results.
l Region Allowable Pressure, psi Actual Pressure, psi A
4403 3152 B
2380 2009 l
Noting the large margins available in the next step of the analysis, i
the support spindle was displaced around the circum"erence of a circle of 3/4" radius.
Six discrete cases of analyses were performed. The case which produces minimun margin, out of all of the six cases, is reported below.
Region Allowable Pressure, psi Actual Pressure, psi A
4165 3074 B
2300 2009 The above analyses confirm that the support leg centerlines can be displaced within a 3/4" radius circle (surrounding their nominal location) without exceeding the plant bearing pressure allowables.
This flexibility provides for the anticipated tolerance needs in support foot location, and the consequences of support translation during the seismic event.
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ATTACHMENT 2 Summary of Margins in Critical Locations for Spent Fuel Racks for SSE, Normal Fuel,*
Allowable / Actual Cell-to-Baseplate weld 1.935 Using actual weld-in-place stress Cell to gap channel weld 1.79 t
stress
(
Support foot to baseplate 3.5 Based on limit load of f
weld stress gross weld cross section Impact load between fuel 5.78 Based on actual normal E
assembly & cell wall fuel load and cell wall limit load Compressive stress in cell 1.44 Based on local cell wall buckling Fuel assembly drop of 1.738*
Based on active fuel 36" to top of rack assumed at 13" below top of rack f
Fuel assembly drop to 3.31***
Normal fuel baseplate
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Stress ratios are obtained for fuel weights = twice normal fuel weight, except where noted.
4 This is a ratio of distance to active fuel / depth of cell metal from top which could yield in event of impact.
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- Distance from base plate to floor divided by deflection of base plate
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resulting f rom dropped load.
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The ratio of allowable value divided by actual (calculated) value is a stress j
ratio, load ratio. or geometry ratio depending on the pseticular calculation.
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