ML20212G347

Ack Receipt of 860915 Rept of Rod Exchange Test.Overly Large Rod Worth Deviation as Compared to Ref Bank Attributed to Util Failure to Follow Methodology in WCAP-9863-A

ML20212G347
Person / Time
Site:	Mcguire, McGuire
Issue date:	01/13/1987
From:	Hood D Office of Nuclear Reactor Regulation
To:	Tucker H DUKE POWER CO.
References
TAC-62972, NUDOCS 8701200237
Download: ML20212G347 (3)

Text

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[eq o g UNITED STATES g ) g NUCLEAR REGULATORY COMMISSION 3  :

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Docket Nos.: 50-369 13 y g and 50-370 ,

fr. H. B. Tucker, Vice President I

Nuclear Production Department Duke Power Company 422 South Church Street Charlotte, North Carolina 28242

Dear Mr. Tucker:

Sub,iect: Rod Worth Deviations - McGuire Nuclear Station, Units I and 2 By letter dated September 15, 1986; you submitted a report entitled "McGuire s Unit  ? Cycle The report 3 Rod stated Exchance that Test - bank the reference Sumary(of Review Shutdown Criteriameasured C) worth, Evaluation."

using the method described in WCAP-9863-A, " Rod Bank Vorth Measurement Utilizino Bank Exchange," was found to be 14.5% below the predicted value and, there-fore, did not meet the " review" criterion of a 10% deviation stated in the WCAP, but that all rod worth deviations met the " acceptance" criteria which are based upon meeting safety analysis input assumptions.

The NPC has reviewed your above report and has discussed additional test re-sults by telephone conversations with NRC Region II and members of your Company.

We find that the difference between the measurement and prediction for the reference bank is much more than expected on the basis of previous experience.

It is, in fact, the largest deviation on a reference bank which we have seen during the roughly eight years that the rod exchange process has been used on any PWR. From our review of the other McGuire Unit 2 Cycle 3 measurements, we find that although they meet theit review criterion, the discrepencies be-

! tween measurements and predictions are large in comparison to previous experience.

You state in the report that the likely cause of the neasured versus predicted differences in reference bank reactivity is a combination of small variances in input to the reactivity computer and measurement environment effects. We note, i however, that Duke Power Company used a boron dilution rate of 700 ppm /hr rather than the recommended rate from 300 to 500 ppm /hr. It has been our ex-perience that using a faster dilution rate than recommended has led to inaccuracies. In addition, the flux rate durino the McGuire reference bank measurement was a decade higher than usual for physics testing. The flux signal was not recorded on the strip cnart, so it is not possible to quantitatively I assess the impact on the reactivity measurements. Generally, measurements made near nuclear heating levels tend to reduce the indicated reactivity. In order to emphasize the importance of the recomended procedures, they were incor-

! porated into the WCAP. We approved the WCAP with the understanding that the l procedures would be followed and that the maximum recommended rates would not j

be exceeded. Hence, we believe your failure to adhere to the procedures in the l WCAP must have contributed to the differences.

! 8701200237 870113 l PDR ADOCK 05000369 P PDR

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Mr. H. B. Tucker ,

,The rod exchange nethod approved for Westinghouse and used by Duke is complex, in part, because calculated correction factors are applied to measured results in crder to obtain inferred results. An additional complexity of the process ,

results from use of detailed three-dinensional calculations at varicus bef ahts j l in the core. Due to the complexity of the calculations and the rod swap tech-nique, our approval of rod swap is limited to use only by Westingbouse in accordance with the approval of WCAP-9863-A. All procedures in the WCAP are f an integral part of the rod exchange methodolcgy. In the future, these pre-cedures shall be follcwed or the baron dilution method should be used to l measure rod worths for all the control banks.

Sircerely, t

Darl Hood, Project Manager PWR Project Directorate #4-Division of PFR Licensing-A cc: See next page DISTRIBUTION:

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O e T Mr. H. B. Tucker Duke Power Company McGuire Nuclear Station cc:

Mr. A.V. Carr, Esq. Dr. John M. Barry Duke Power Company Department of Environmental Health P. O. Box 33189 Mecklenburg County 422 South Church Street 1200 Blythe Boulevard Charlotte, North Carolina 28242 Charlotte, North Carolina 28203 County Manager of Mecklenburg County 720 East Fourth Street Charlotte, North Carolina 28202 l Chairman, North Carolina Utilities Commission Mr. Robert Gill Dobbs Building Duke Power Company 430 North Salisbury Street Nuclear Production Department Raleigh, Nor th Carolina 27602 P. O. Box 33189 -

Charlotte, North Carolina 28242 Mr. Dayne H. Brown, Chief Padiation Protection Branch J. Michael McGarry, III, Esq. Division of Facility Services Bishop. Liberman, Cook, Purcell Department of Human Resources and Reynolds 701 Barbour Drive 1200 Seventeenth Street, N.W. Raleigh, North Carolina 27603-2008 Washington, D. C. 20036 Senior Resident Inspector c/o U.S. Nuclear Regulatory Commission Route 4, Box 529 -

Hunterville, North Carolina 28078 Regional Administrator, Region II U.S. Nuclear Regulatory Commission, 101 Marietta Street, N.W. , Suite 2900 Atlanta, Georgia 30323 L. L. Williams Area Manager, Mid-South Area ESSD Projects Westinghouse Electric Corporation MNC West Tower - Bay 239 P. O. Box 355 Pittsburgh, Pennsylvania 15230

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