ML18136A152

Forwards Info Re Calculational Uncertainties Associated W/ Current Design Data Generated W/Flame Model,In Response to NRC Questions on VEP-FRD-24, VEPCO Flame Model.

ML18136A152
Person / Time
Site:	Surry, North Anna
Issue date:	11/02/1979
From:	Thomas W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Harold Denton Office of Nuclear Reactor Regulation
References
017A, 17A, NUDOCS 7911060361
Download: ML18136A152 (5)

Text

VIRGINIA ELECTRIC .A.ND POWER COMP.A.NY RIOHMOND, VIRGINIA 2 3 2 61 November 2, 1979 Mr. H. R. Denton, Director Serial No. 017A Office of Nuclear Reactor.Regulation FR/WCB: mvc Attn: Mr. Albert Schwencer~ Chief Docket Nos. 50-280 Operating Reactors Branch No. 1 50-281 Divisi~n of Operating Reactors 50-338 .s U. S. Nuclear Regulatory Commission 50-339 Washington, D.C. 20555 License Nos. DPR-32 DPR-37 NPF-4

Dear Mr. Denton:

TOPICAL REPORT VEP-FRD-24

• .. "THE VEPCO 'FLAME MODEL" Attachment 1 provides our responses to Nuclear Regulatory Commission (NRC) Staff questions on the Vepco topical report VEP-FRD-24, "The Vepco FLAME Model," transmitted by the W. N. Thomas (Vepco) to H. R. Denton (NRC) letter, Serial No. 017, dated January 19, 1979. These questions were provided informally by Mr. J. D. Neighbors to our Mr. M. L. Bowling.

Specifically addressed are the calculational uncertainties associated with the current design data generated with the FLAME model. These uncertainties will be applied to the appropriate licensing and safety analysis calculations performed with the FLAME Model. No uncertainty will be applied to design data calculated with the FLAME Model used to compare with startup physics and core follow measurement results.

Should you have any further questions concerning this topical report, please contact us.

2:;;:L W. N. Thomas Vice President Fuel Resources Attachment p

r*

Question 1: For what parameters will the Vepco FLAME Model (Reference 1) be used as the p~oduction calculational tool:

Response 1: As noted in Reference 1, the Vepco FLA}1E Model is capable of calculating:

1. Assembly and core average axial power distributions

2. Differential control rod bank worths

3. Integral control rod bank worths as a function of bank position

4. Control rod bank insertion limits

5. Axial burnup distribution

6. Axial offset T

7. Peaking Factors (F Q' FXY(Z), FZ)

However, the FLA}1E model is currently used to calculate only integral and differential rod worths and core average axial peaking factors on a produc.tion basis.

Question 2: What are the calculational uncertainties associated with these parameters?

Response 2: See Table 1 below.

TABLE 1 FLAME Model Calculational Uncertainties Number of Parameter Data Points Uncertainty Core Average Axial Peaking 44 8.0%

Factor, Fz Differential Bank Worth Average 15 3.0 pcm/step Maximum 16 3.0 pcm/step Integral Bank Worth Individual 26 15.0%

Cumulative 26 10.0%

Question 3: How were these uncertainties determined?

Response 3: The uncertainties to be applied to FLAME model predictions have been obtained by using the statistical methods described.in Reference 2. The indicated uncertainties are conservative (i.e., larger) with respect to calculated values based on a 95% probability with a 95% confi'dence level.

The uncertainties developed do not take credit for measurement uncertainty. The deviation between measured data and actual plant parameters could be subtracted from the deviation b*etween measurement and.prediction. Consequently, the measurement un-certainty inherent in the resulbs presented provides additional conservatism in the proposed caiculational uncertainties.

L ..

REFERENCES

1. W. C. Beck, "The Vepco FLAME Model", VEP-FRD-24, October 197.8 (Virginia Electric and Power Co.).

2. "An Acceptable Model and Related Statistical Methods for the Analysis of Fuel Densification", U.S. N.R.C. Regulatory Guide 1.126, Revision 1, March 1978.