ML041450310

CFR50.46 Annual Report of ECCS Model Revisions

ML041450310
Person / Time
Site:	South Texas
Issue date:	05/03/2004
From:	Leazar D South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-04001722
Download: ML041450310 (4)

Text

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AAA May 3, 2004 NOC-AE-04001722 STI: 31741298 10CFR50.46 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Units 1 & 2 Docket Nos. STN 50498, STN 50-499 10CFR50.46 Annual Report of ECCS Model Revisions

Reference:

Letter from D. A. Leazar to NRC Document Control Desk, "Revision to the Year 2002 10CFR50.46 Annual Report of ECCS Model Revisions," dated April 8,2003 (NOC-AE-03001500)

Pursuant to 10CFR50.46(a)(3)(ii), the South Texas Project (STP) submits this annual report concerning revisions to the accepted Emergency Core Cooling System (ECCS) evaluation model at STP Units 1 and 2.

During 2003, the Small Break LOCA Peak Clad Temperature (PCT) increased from 1578'F (see reference) to 16120F. The 340F increase is the result of a PCT penalty, developed by Westinghouse, to address inconsistencies in several drift flux models as well as the nodal bubble rise/droplet fall models. During 2003 no PCT assessments were required for the Large Break ECCS Model. The Large Break LOCA PCT remains at 21360F (see reference).

2003 SBLOCA PCT Assessment The NOTRUMP code was updated to resolve some inconsistencies in several drift flux models and the nodal bubble rise/droplet fall models. The changes include:

1) Bubble rise and droplet fall models were made consistent with flow link calculations,

2) Corrections were made to limits employed in the vertical counter-current flooding models,

3) Checking logic was added to correct situations where drift flux model inconsistencies could result (i.e. prevent liquid flow from an all-vapor node and vapor flow from an all-liquid node, and

4) A more rigorous version of the Yeh Drift Flux Model was implemented (the previous version of this model was incorrectly restricted to a 50% void fraction limit).

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NOC-AE-04001722 Page 2 of 3 Westinghouse classified the changes as a closely-related group in accordance with Section 4.1.2 of WCAP-13451. The 340F Small Break LOCA PCT penalty was developed through plant-specific calculations.

Significance Determination The 340F Small Break LOCA PCT penalty is the only PCT assessment for 2003. Since the impact of the changes is less than 50 'F, the penalty is classified as "not significant" as defined in IOCFR50.46. A schedule for reanalysis for the Small Break LOCA is not provided because the revised PCT remains below the regulatory limit and the value of the PCT change is less than 500F.

PCT Rackups The acceptance criteria for all models continue to be satisfied. Attachment I provides the current ECCS evaluation model PCT rack-ups.

If you should have any questions concerning this matter, please contact Mr. Charles Albury at (361) 972-8901 or me at (361) 972-7795.

David A. Leazar

Director, Nuclear Fuel & Analysis jmw/jal

Attachment:

2003 Year-End PCT Rack-ups

NOC-AE-04001722 Page 3 of 3 cc:

(paper copy)

(electronic copy)

Bruce S. Mallett Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville,MD 20852 Richard A. Ratliff Bureau of Radiation Control Texas Department of Health 1100 West 49th Street Austin, TX 78756-3189 Jeffrey Cruz U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MNI 16 Wadsworth, TX 77483 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP L. D. Blaylock City Public Service Michael K. Webb U. S. Nuclear Regulatory Commission R. L. Balcom Texas Genco, LP A. Ramirez City of Austin C. A. Johnson AEP Texas Central Company Jon C. Wood Matthews & Branscomb C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704

NOC-AE-04001722 Page 1 of I ATTACHMENT 1 2003 YEAR-END PCT RACK-UPS Unit 1 and Unit 2 Large Break LOCA:

2002 / 2003 Year-End Large Break LOCA PCT (see reference) 2136 OF Unit 1 and Unit 2 Small Break LOCA:

2002 Year-End Small Break LOCA PCT (see reference) 1578 OF NOTRUMP Bubble Rise / Droplet Fall and Drift Flux Model Inconsistency Correction 34 OF 2003 Year-End Small Break LOCA PCT 1612 OF