ML20040H506

Forwards Response to Staff Questions Re Statistical Combination of Uncertainties.Info Intended to Complete C-E Input Needed to Close Out SER Confirmatory Item

ML20040H506
Person / Time
Site:	05000470
Issue date:	02/09/1982
From:	Scherer A ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:	Eisenhut D Office of Nuclear Reactor Regulation
References
LD-82-012, LD-82-12, NUDOCS 8202180323
Download: ML20040H506 (2)

Text

,

C-E Power Systems Tel. 203/688-1911 Combustion Engineenng. Inc.

• Telex 99297 1000 Prospect Hill Road Windsor, Connecticut 06095 POWER H SYSTEMS Docket Nr..: STN-50-470F February 9, 1982 LD-82-012 SL W1li,,

Mr. Darrell G. Eisenhut, Director O Division of Licensing /

U. S. Nuclear Regulatory Commission Washington, D. C. 20555 f:U .-

Q, 3; , . , . I ? SSa Q 'h

Subject:

CESSAR SER Confirmatory Item on SCU b\ >

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Dear Mr. Eisenhut:

//, 7-Transmitted herewith is the response to staff questions on Statistical Combin-ation of Uncertainties (SCU) identified as a confirmatory item in Section 4.4.6 of the CESSAR Safety Evaluation Report.

The enclosed information is intended to complete the C-E input that the staff needs to close out the CESSAR confirmatory item concerning SCU.

If I can be of any additional assistance in this matter, please contact me or Mr. G. A. Davis of my staff a' (203)688-1911, Extension 2803 Very truly yours, COMBUSTION ENGINEERING, INC.

n. M enerer Director Nuclear Licensing AES:ctk Enclosure cc: C. I. Grimes

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I 8202180323 820209 PDR ADOCK 05000 E

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e STATISTICAL COMBINATION OF UNCERTAINTIES METHODS TO COMBINE DNBR UNCERTAINTIES FOR CESSAR PLANTS The Statistical Combination of Uncertainties (SCU) methods that will be applied to combine DNBR uncertainties for CESSAR plants will be essentially identical to the methods applied to combine system parameter uncertainties for ANO - Unit

2. The ANO-2 methods are discussed in Reference' 1 and have already received NRC approval. - While the same methods will be used for CESSAR plants, fewer system parameters will actually be combined statistically in the CESSAR plants SCU analysis.

A limited number of flow nodel test data are available to characterize the CESSAR plants inlet flow distribution uncertainties statistically. Consequent-ly, it has been decided to impose deterministic allowances based on the existing test data to account for the CESSAR plants inlet flow distribution uncertainties. These deterministic allowances will be applied in the detailed thermal-hydraulic (D-TORC) analyses used to benchmark the design thermal margin model. A description of the general benchmarking method is provided in Reference 2.

Since the inlet flow distribution uncertainties will be taken into account deterministically for CESSAR plants, they will not be included in the SCU analysis. The remaining system parameter uncertainties, listed in Table 5-1 of Reference 1, will be combined in the CESSAR plants SCU analysis. These remain-ing uncertainties include the enthalpy rise factor, the systematic pitch,.

systematic clad 0.D., heat flux factor, and the CE-1 CHF correlation.

References

1. " Statistical Combination of Uncertainties: Combination of Systen Parameter Uncertainties in Thermal Margin Analyses for Arkansas Nuclear One Unit 2",

CEN-139(A)-P, November, 1980.

2. " TORC Code: Verification and Simplified Modeling Methods", CENPD-206-P-A, June, 1981.