ML19343D578
| ML19343D578 | |
| Person / Time | |
|---|---|
| Site: | 07001100 |
| Issue date: | 03/18/1981 |
| From: | Lichtenberger ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY |
| To: | Page R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| 18773, NUDOCS 8105050360 | |
| Download: ML19343D578 (6) | |
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Combustion Engineenng. inc.
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Windsor. Connecticut c6095 P M POWER Mustam SYSTEMS March 18,1981 License SNM-1067 Docket 70-1100 U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Mr. R. G. Page, Acting Chief Uranium Fuel Licensing Branch Division of Fuel Cycle & Material Safety
Dear Mr. Page:
It is requested that License SNM-1067 be amended to allow addit'ional storage of pellets at work station P-22 in the Building #17 fuel pelletizing area.
Presently, a slab thickness of 3.7 inches is permitted and the width of the storage shelves is restricted to 18 inches. A slab limit of 4.0 inches and a width of 30 inches has been analyzed for and demonstrates that an adequate criticality safety margin is maintained. Details of the calculational model, assumptions used, and results obtained are contained in the proposed license page revisions.
It is therefore requested that the following page changes to License SNM-1067 be approved:
Add Page Delete Page C-16, Rev.1, 3/18/81 C-16, Rev. O, 3/22/79 C-16a, Rev.0, 3/18/81 D-17, Rev.1, 3/18/81 D-17, Rev. O, 3/22/79 D-18, Rev.1, 3/18/81 D-18, Rev. 0, 3/22/79 D-19, Rev.1, 3/18/81 0-19, Rev. O, 3/22/79 If you have any questions regarding this amendment request, please contact Mr. G. J. Bakevich of my staff.
Very truly yours,
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6.2 Pellet Storage Shelves Steel shelves (W.S. P-22 and P-ll4) are provided for pellet storage.
The shelves are three high. They have a width of 30" and are limited to o
a slab thickness of 4.0 inches. The slab thickness of 4.0" is assured by limiting the number of fuel pellet trays stacked at any position.
Criticality Safety Analysis The following conservative assumptions were incorporated into the calculational model of the pellet storage shelves:
- 1) Each shelf was assumed to hold a 4.0 inch thickness of UO at 235)2 optimum moderation and maximum enrichment (4.1. wt.% U
- 2) The system was assumed to be infinite in the horizontal plane.
- 3) Variable density external water mist was introduced to determine peak reactivity.
- 4) All steel construction material (except the 1/4 inch shelf and back plate) was neglected The KENO-IV Code with 16 group Hansen-Roach cross sections was used to detemine the reactivity of the pellet storage shelves under various conditions of moderation. Optimum moderation of the fuel occurred at a concentration of 2.4 gm U/cc in water, assuming no external water mist.
The peak reactivity of the system, keff = 0.913310.0061 occurred at an external water mist density of 0.05 gm/cc which is higher than one could attain from fire fighting equipment or a sprinkler system. The criticality safety analysis demonstrates that the spacing boundary can be located 60 inches from the front of the shelves.
Note:
In the determination of cross sections for the pellet-water mixture, a volume homogenization procedure was employed which is non-conservative for low enrichment fuel. However, it has been shown that the non-conservatism of this approximation is more than offset by the conservative assumption that the pellet-water mixture is at an optimum fuel concentration of 2.4 gm U/cc.
For actual loading of the trays, the pellets pack to an average density of 5.95 gm UO /cc (5.24 gm U/cc), with 2
License No. SNM-1067, Docket 70-1100 Revision 1 Date: 3/18/81 Page: C-16
a 2a variation of 0.264 as detennined from a series of 14 measurements. This results in a much higher fuel density than the optimum density used in the analysis (2.4 gm U/cc).
For 5 w/o U0, the following critical masses (kg U) are deduced from 2
published critical data in figures I.D.9 and I.E.1 of UKAEA HandbookAHSB(1):
2.4 gm U/cc 5.2 gm U/cc Homogeneous 4 0 kg U N420 kg U 0.4" dia. rods
%56 kg U N195 kg U From this data one can see that the conservatism associated with the assumption of a fuel density of 2.4 gm U/cc in the homogeneous approximation is equivalent to a reduction in the critical mass of 340 kg U whereas the non-conservatism of using the homogeneous approximation evaluated for a fuel censity of 5.2 gm U/cc is equivalent to only 225 kg U.
Additional storage (W.S. P-15, P-19, and P-21) is provided for slab storage of finished pellets. A 5.5. inch slab limit is imposed, based on the following:
Sintered pellets, wht.n randomly loaded into sintering boats, or storage trays, pack to an average density of 5.95 gm/cc, with a 2a variation of 0.264 as detennined from a series of 14 measurements. Thus, at a 95% confidence level, the V
/Y ratio does not exceed 0.995 and from Figure 1.E.16 of UKAEA H0 UO 2
2 Handbook AHSB 1, the critical infinite slab thickness for 4.1% enriched 5 0.4" License No. SNM-1067, Docket 70-1100 Revision 1 Date:
3/1 8/81 Page: C-16a
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