ML19338E225
| ML19338E225 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 09/19/1980 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8009250244 | |
| Download: ML19338E225 (3) | |
Text
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b MSP NORTHERN STATES POWER COMPANY M I N N E A PO LI S. M I N N E S OTA 55401 September 19, 1980 Director of Nuclear Reactor Regulation U S Nuclear Regulatory Commission Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket No. 50-282 License No. DPR-42 50-306 DPR-60 Supplement to License Amendment Dated May 6, 1980 SI Actuation and Power Distribution Limits The staff has requested additional information concerning this license amendment.
The staf f questions and the NSP responses associated with the Westinghouse fuel are as follows:
Question 1 The effects of rod bow on DNBR margin have been at le as t partially accounted for in previous licensing reviews by the application of generic thermal margin credits such as (1) the DNBR correlation statistics, (2) the red pitch reduction factor and (3) the thermal diffusion coefficient value. Please provide the appropriate values for the DNBR margins represented by these parameters for the Prairie Island plant.
Response 1 The appropriate DNBR margins represented by the specified parameters for the Prairie Island plant are:
Required for Used in
% DNBR Parameter Safety Analysis Design Margin Limit DNBR 1.24 1.30 4.8%
Pitch Red'iction No Yes 3.3%
Thermal Diffusion 0.019 0.0 38 3.0%
Coefficient TOTAL 11.1%
Question 2 The axial heat flux densification spike ef fect on DNB is plant specific.
Please provide the existing DNBR margin represented by inclusion of this factor in the Prairie Island safety analysis.
Include a brief discussion of how the densification spike factor is utilized in the safety analyses with respect to the DNBR thermal margin represented by its inclusion in these analyses.
80092502d
[
o NORTHERN CTATED POWER COMPANY a
Director of Nuclear Reactor Regulation September 19, 1980 Page Response 2 When the PT Densification FSAR was done in 1973, the DNB analysis included a densification power spike immediately upstre:am of the location of minimum DNBR, resulting in a calculated DNBR 7% less than that calculated without the densification spike.
Since that time, Westinghouse conducted DNB tests with ger spikes similar to those predicted to result from densification The results indicated that the ef fect of that spike on DNB 1 eat flux was negligib le.
Therefore, the inclusion of the above spike penalty (7% in DNBR) in the PI analysis repret. ento a 7% margin which can be utilized to offset current rod bow penalties.
Please contact us if you have any questions.
Very truly yours, L 0 Mayer, PE Manager of Nuclear Support Services LOM/TMP/jh cc: J G Keppler G Charnoff NRC Resident Ins pector
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REFERENCES
(
R Salvatori, " Fuel Densification Prairie Island Unit 1," WCAP-8091, March, 1973.
2)WCAP-8174, re: spike penalty elimination, DNB tests; Staf f review Stello to DeYoung (TAR-794).
(
Letter Eicheldinger to Stello, August 13, 1976, NS-CE-Il61; re: NRC acceptabi.lity of procedure of offsetting bow penalty with thermal margins, and application to plants.
(4)WCAP-2298, re: TDC; reviewed by staf f, Stello to DeYoung, September 18, 1974 (TAR-903).
(5) Letter Eicheldinger to Vassallo, May 1,1975, NS-CE-598, re:
Staff review of pitch reduction allowance.
(6) Letter Salvatori to Vassallo, Uovember 5, 1974, NS-RS-423, re: pitch reduction.
.