ML20244A421
| ML20244A421 | |
| Person / Time | |
|---|---|
| Site: | 05000545 |
| Issue date: | 10/24/1977 |
| From: | Eicheldinger C WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | Ross D Office of Nuclear Reactor Regulation |
| References | |
| NS-CE-1580, TAC-07329, NUDOCS 7808300049 | |
| Download: ML20244A421 (3) | |
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Westinghouse Electric Corporation Power Systems ecrass PtttsturghPem:yNaia 15230 i
October 24, 1977 NS-CE-1580 )
Mr. Denwood F. Ross, Jr.
Assistant Director Reactor Safety Division of Reactor Licensing .
i Office of Nuclear Reactor Regulation l U. S. Nuclear Regulatory Commission 7920 Norfolk Avente Bethesda, Maryland 20014 j
Dear Mr. Ross:
Enclosed are:
1 Twenty-five (25) copies of Attachment on Fuel Rod Bow Penalties (Proprietary).
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2.
Twenty (20))
Proprietary . copies of Attachment on Fuel Rod Bow Penalties (Non- ,
Also enclosed are: -
- 1. One copy of Application for Withholdin , AW-76-35, (Non-Proprietary).
- 2. One copy of Affidavit (Non-Proprietary This letter is intended to provide the basis for a near tem revision of fuel
. rod bow penalties imposed on the current Westinghouse 15 x 15 and 17 x 17 i designs. l
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The method currently in use' for quantifying rod bow penalties is essentially a two-step process:
First, DNBR penalty as a function of channel closure is specified based upon critical heat flux rod bundle test results. The bow penalty currently pre-scribed is basically a linear function of channel closure normalized to a measured DNBR penalty associated with rod contact in thimble cell geometry.
This revision incorporates the results of recent partial bow thimble cell l tests e.t 85% closure conducted by Westinghouse which demonstrate a signifi- l cantly lower penalty at partial closure than indicated by the linear inter- !
polation. --
,j Secondly, rod bow magnitude, i.e. channel closure is specified as a function of fuel burnup based upon rod bow measurements of irradiated fuel assemblies.
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In the case of 15 x 15 LOPAR fuel, a statistical bound has been derived from l a' fit of twenty-seven regions of data. In the case of 17 x 17, a conserv'ative !
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NS-CE-1580 October 24, 1977 Page 2 l i
bound had been specified based on a simplistic extrapolation of the 15 x IE LOPAR data. This extrapolation was necessary due to a lack of actual 17 x 17 j irradiated bow measurements. This revision establishes a 17 x 17 bow magni- l tude versus burnup projection in its own right based upon 17 x 17 bow measure- l ments of demonstration assemblies irradiated in the VEPC0 Surry plants. Poten- J tial region to region variability is conservatively accommodated by augmentation 1 of the Surry bow measurements by a factor of 1.5 as derived from the 15 x 15 l LOPAR data. This data was additionally augmented by a factor of 1.2 to con-servatively account for potential cold to hot affects. We understand that this approach is consistent with current NRC recommendations on treatment of l limited bow data sets. j i
The net result of these revisions is to reduce EOL design burnup DNBR bow penalties (before margins) to 11.7% for 15 x 15 LOPAR fuel and 10.6% for I 17 x 17 fuel . By comparison the current EOL DNBR bow penalties for both designs is on the order of 30%.
Supporting information is protided in the attachments to this letter which provide an emnded discussion of the information discussed with the NRC Staff at an October 26, 1977 meeting.
We request that this revision be recognized as an interim position pending i an expected statistical convolution of bow affect with DNB correlation statistics and/or, in the case of 17 x 17 fuel, the first . full cores irrad-iated fuel examination. Convolution will require a definition of bow penalty as a function of closure rather than merely bounding the affect as done for the purpose of this interim position.
Westinghouse is recommending to its customers, both first core and reload, that they reference this submittal on their individual applications.
This submittal contains proprietary information of Westinghouse Electric Corporation. In conformance with the requirements of 10CFR Section 2.790, 1 as amended, of the Commission's regulations, we are enclosing with this submittal an application for withholding from public disclosyre and an affidavi t. The affidavit sets forth the basis on which the 'information may be withheld from public disclosure by the Commission. "
Correspondence with respect to the affidavit or application for withholding l!
il should reference AW-77-52 and should be addressed to R. A. Wiesemann. Manager I j
of Licensing Programs, Westinghouse Electric Corporation, P. O. Box 355, '
Pittsburgh, Pa. 15230 Please feel free to contact us if you should have further questions on this [{
matter. ,, I Very truly yours.
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C. Eiche1dinger, Manager sP- j A ment , clear Safety Dopartment .
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