ML052510484

Stations Units 1 & 2, Millstone Power Station Units 2 & 3, Information Regarding a Lynxt Error Supporting the Request for Approval of Topical Report DOM-NAF-2 Reactor Core Thermal-hydraulics Using the VIPRE-D Computer .

ML052510484
Person / Time
Site:	Millstone, Surry, North Anna
Issue date:	09/08/2005
From:	Hartz L Dominion Nuclear Connecticut, Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
05-020A, DOM-NAF-2
Download: ML052510484 (5)

Text

1 Dominion September 8 , 2005 United States Nuclear Regulatory Commission Serial No. 05-020A Attention: Document Control Desk NL&OS/ETS: RO Washington, D.C. 20555 Docket Nos. 50-280/281 50-338/339 50-336/423 License Nos. DPR-32/37 NPF-4/7 DPR-65/NPF-49 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

DOMINION NUCLEAR CONNECTICUT, INC. (DNC)

NORTH ANNA AND SURRY POWER STATIONS UNITS 1 AND 2 MILLSTONE POWER STATION UNITS 2 AND 3 INFORMATION REGARDING A LYNXT ERROR SUPPORTING THE REQUEST FOR APPROVAL OF TOPICAL REPORT DOM-NAF-2 REACTOR CORE THERMAL-HYDRAULICS USING THE VIPRE-D COMPUTER CODE INCLUDING APPENDIX A QUALIFICATION OF THE F-ANP BWU CHF CORRELATIONS IN THE DOMINION VIPRE-D COMPUTER CODE In a September 28, 2004 letter (Serial No.04-406), Dominion/DNC submitted Topical Report DOM-NAF-2, Reactor Core Thermal-Hydraulics Using the VI PRE-D Computer Code, and Appendix A to the Topical Report DOM-NAF-2, Qualification of the F-ANP BWU CHF Correlations in the Dominion VIPRE-D Computer Code, for NRC review and approval. Dominion/DNC was recently notified by Framatome ANP of an error identified in the LYNXT code, which was used to benchmark the VIPRE-D code. Although the impact of this error is considered negligible and should not affect the NRCs review of VIPRE-D, DominionIDNC is providing a description of the error and the impact for your information.

The attachment to this letter summarizes the error and the impact on the DNB benchmark analyses.

Although the docket number is identified for each Dominion/DNC unit, Dominion/DNC is requesting the approval of the generic application of this topical report. Plant specific applications of this topical report, including applicable appendixes, will be submitted to the NRC for review and approval, in accordance with Section 2.1 of DOM-NAF-2.

If you have further questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours, Leslie N. Hartz Vice President Nuclear Engineering Virginia Electric and Power Company Dominion Nuclear Connecticut, Inc.

Serial No. 05-020A Docket Nos. 50-280/281/338/339/336/423 Page 2 of 2 Attachment Commitments made in this letter: None cc: U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, Pennsylvania 19406-141 5 Mr. J. T. Reece (w/o Att.)

NRC Senior Resident Inspector North Anna Power Station Mr. N. P. Garrett w/o Att.)

NRC Senior Resident Inspector Surry Power Station Mr. S. M. Schneider (w/o Att.)

NRC Senior Resident Inspector Millstone Power Station Mr. V. Nerses NRC Senior Project Manager - Millstone Unit 2 U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. G. F. Wunder NRC Senior Project Manager - Millstone Unit 3 U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Stephen R. Monarque NRC Project Manager - Surry and North Anna U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, Maryland 20852

Attachment 1 Topical Report DOM-NAF-2 05-020A REACTOR CORE THERMAL-HYDRAULICS USING THE VIPRE-D COMPUTER CODE INFORMATION REGARDING A LYNXT ERROR Virginia Electric and Power Company (Dominion)

Dominion Nuclear Connecticut (DNC)

Characterization of the LYNXT Error During the development of a new version of the LYNXT computer code, Framatome ANP detected an error that affects the LYNXT DNB predictions for previous code versions. It was discovered that two different surface fits to the ASME steam tables were used to calculate the values for the thermodynamic quality for a given local coolant condition within the code. The difference in the two values is based on two different water property subroutines used to generate the saturated liquid enthalpy (hf) and the latent heat of vaporization (hfg), which are needed to calculate the thermodynamic quality given the local coolant enthalpy. One thermodynamic quality definition was being used in the flow field calculations and the second definition was being used in the calculation of the DNBR. Although the two definitions are very close (maximum observed differences less than 0.2 percent in hf and hfg) there is an impact on DNBR predictions. Neither surface fit is incorrect by itself, but the inconsistency of using two different values for the quality was characterized as a code error.

Generic Impact of the LYNXT Error Due to the location of the error in the LYNXT code, there is no impact to the LYNXT/BWU code/correlation limits reported in Framatome ANP's Topical Report BAW-10199 and Addendum 2. The differences between the DNBR results provided by the corrected and the uncorrected versions of the LYNXT code are extremely small, but observable.

Specific Impact to DOM-NAF-2 Topical Report DOM-NAF-2 describes Dominion's use of the VIPRE-D code, including modeling and qualification for Pressurized Water Reactors (PW R) thermal-hydraulic design. The Topical is entirely based on VIPRE-D calculations, and it does not rely on LYNXT results. However, the Topical includes information about VIPRE-D benchmarks to the NRC-approved code, LYNXT, to assist the NRC in the review of the VIPRE-D Topical Report.

For the 173 North Anna statepoints used in Section 5.1 in the Topical Report DOM-NAF-2, the average difference between LYNXT predictions with the error and without the error is less than 0.02%, and the maximum difference is less than 0.15%.

The maximum change to any numerical value reported in Section 5 of the main body of Topical Report DOM-NAF-2 regarding benchmark DNBR calculations between VIPRE-D and LYNXT is 0.02%.

0 The comparisons between the corrected LYNXT and VIPRE-D are slightly better than the comparisons between the uncorrected LYNXT and VIPRE-D.

Appendix A to Topical Report DOM-NAF-2 documents Dominion's qualification of the BWU-N, BWU-Z and BWU-ZM correlations with VIPRE-D. Tables A.4.1-3 and A.4.3-3 of Appendix A list the LYNXT/BWU codelcorrelation limits for information in comparison

to the calculated values for VIPRE-D/BWU. Since there is no impact to the LYNXT/BWU code-correlation limits reported in Framatome ANP's Topical Report BAW-10199 (including Addendum 2), Appendix A to Topical Report DOM-NAF-2 is not affected by this error.

Appendix B to Topical Report DOM-NAF-2 documents Dominion's qualification of the WRB-1 correlation with VIPRE-D. Appendix B to Topical Report DOM-NAF-2 is not affected by this error.

Conclusion Based on the above discussion, Dominion has concluded that the LYNXT error has a negligible impact to the information provided in Topical Report DOM-NAF-2, including Appendixes A and B.