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Babcock &Wilcox ro -c-ra= crow P.o. Box 1260, Lynchburg, Va. 24505 Telephone: (804) 384-5111
!,,ly October 11, 1977 Q, sq 0
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Office of Nuclear Reactor Regulation i.~~
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Mr. Steven A. Varga
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Chief, Light Water Reactors Branch #4 G'
Division of Project Management
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U. S. Nuclear Regulatory Commission
_v Washington, D.C.
20555
Subject:
Request for B6W Topical Report on B C Absorber 4
Reference:
Steven A. Varga to J. H. Taylor, " Request for B6W Topical Report on B C Control Rods 4
Dear Mr. Varga:
This is in reply to the request in the above reference to advise you concerning the B4W schedule for preparation of the subject topical report.
The TVA Bellefonte Units will be the first B4W 205 units that will utilize B C control rods.
The FSAR for these units has g
already been prepared and will be. filled on December 1, 1977.
It is therefore not possible to submit a topical report con-cerning B C one year prior to the submittal of the FSAR on the 4
first plant to use B C, as requested, in the above reference.
4 The TVA FSAR will contain significantly more information con-cerning B conforms,C control rods than the B-SAR, since the TVA FSAR to Revision 2 to the SAR format guide.
B6W feels that the information provided in the TVA FSAR should be sufficient to meet the needs of a Staff review concerning B C control rods.
In any event, the use of B C control rods will b8 resolved on the 3
TVA docket and the review 3hould be completed by the end of 1978.
This date is well in advance of the schedule for submittal of an FSAR for the first applicant referencing the B-SAR (during the first quarter of 1983).
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The Babcock & Wilcox Company / Estabhshed 1867 7
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1 Mr. Steven A. Varga October 11, 1977 B6W therefore recommends that in lieu of a topical report,.
the review of B G control rods for use in 205 FA units be g
completed during the licensing of the TVA Bellefonte Units.
truly yours
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Manager, Licensing l
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re.,or cencranoo c,ou, P.o. Box 1200, Lynchburg, Va. 24505 Telephone:(804) 384-5111 December 20, 1977-Mr. Steven A. Varga Light Water Reac' tors Branch #4 Division of Project Management Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Subject:
VMFT Experimental Results
References:
1)
Topical Reports BAW-10025 and 10025P, " Reactor Vessel Model Flow Tests for 205 Fuel Assembly Cores" 2)
Topical Reports BAW-10026 and 10026P, " Reactor Vessel Model Flow Tests for 145 Fuel Assembly Cores"
Dear Mr. Varga:
Recent experiments at the BGN Vessel Model Flow Test facility have shown results which will affect the information presented in the referenced topical reports.
These experimen'ts were discussed at length with G. Kelly and W. Hodges of the NRC staff in a phone conversation on December 9, 19'7.
-The investigations conducted concerned a calibration error which results from an assymetric flow distributor plate geometry upstream of the venturi flow nozzles and the orientation of the flow meter taps relative to this geometry.
The results show that the venturi meter flow measurements are sensitive to the orientation.of the differential pressure taps with respect to the upstream flow distributor p' late geometry.
Seventeen different flow distributor plate geometries, i
characteristic of incore conditions, were mocked up in the calibration loop.
For each geometry, the effect of measuring the flow at each of the four corners, which is consistent with the probe orientation in the VMFT, was investigated.
The statistical error which results from the orientation of the differential pressure taps has been calculated for a 95/95 tolerance limit using Monte Carlo techniques.
Each flow meter calibration curve was adjusted to accommodate the error and the statistical treatment identified a 2% reduction of flow in the interior region of the core and a reduction of the minimum flow maldistribution factor. from 0.99 (as reported in Reference 1) to 0.965.
The Dabcock & Wifrez company / E',taNi+,hed 1867 L.
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Mr. Steven A. Varga Page 2 December 20, 1977 Preliminary results of parametric studies using advanced analysis methods have indicated that the overall effect on minimum DNBR calculations will be negligibic.
This conclusion is true with regard to the reports noted in both References 1 and 2 above.
B4W intends to submit revisions to Reference 1 in the second quarter of 1978 and to Reference 2 in the second half of 1978.
B6W commits to use the reduced flow factor determined as a result'of these recent investigations in future analyses at the FSAR stage on all affected applications utilizing methods which will have been approved by the NRC staff.
These FSAR analyses will show a negligible change in DNBR.
If you have any questions with respect to these topicals or this lettdr, please contact Mr. D. Mars of my staff (Extension 2852).
V truly yours ffi/J/.
h ' (f 7 James II. Taylor Manager, Licensing Jilt:dsf cc:
R. B. Borsum (BGW)
__T. 11. Cox _(NRC)._
W. liodges (NRC)
G. Kelly (NRC)
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