05000498/LER-1988-052, Discusses Effects of Westinghouse Generic RCS Flow Anomaly, Per LER 88-052,Rev 1.Util Will Reevaluate DNB Ratio Using WRB-1 Correlation Prior to Unit Refueling in Summer.Interim RCS Flow Requirments of 40,000 Gpm Will Be Mainta

Discusses Effects of Westinghouse Generic RCS Flow Anomaly, Per LER 88-052,Rev 1.Util Will Reevaluate DNB Ratio Using WRB-1 Correlation Prior to Unit Refueling in Summer.Interim RCS Flow Requirments of 40,000 Gpm Will Be Maintained

ML20235U370
Person / Time
Site:	South Texas
Issue date:	03/01/1989
From:	Mcburnett M HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-3003, NUDOCS 8903090171
Download: ML20235U370 (3)

LER-2088-052, Discusses Effects of Westinghouse Generic RCS Flow Anomaly, Per LER 88-052,Rev 1.Util Will Reevaluate DNB Ratio Using WRB-1 Correlation Prior to Unit Refueling in Summer.Interim RCS Flow Requirments of 40,000 Gpm Will Be Maintained

Event date:
Report date:
4982088052R00 - NRC Website

text

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The Light c o mpg;a ny South Texas Project Electric Generating

gp P.O.Station Box 289 Wadsworth, Texas 77483 g,,

l March 1, 1989 ST-HL-AE-3003 ,

l File No.* G26 10CFR50.73

/A U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station Unit 1 Docket No. STN 50-498 Effects of the Westinghouse Generic Reactor Coolant System F]ow Anomaly Reference 1: Letter ST-HL-AE-2911 from G. E. Vaughn to USNRC Document Control Desk dated December 29, 1988 (Licensee Event Report 88-052).

On December 29, 1988, pursuant to 10CFR50.73, Houston Lighting & Power (HL&P) submitted Licensee Event Report 88-052 Rev. I regarc'ing the effects of the Westinghouse Generic Reactor Coolant System Flow Anomaly on the South Texas Project Electric Generating Station Unit 1.

The flow anomaly is a thermal-hydraulic instability in the reactor vessel which results in a decrease in coolant flow to certain areas of the reactor core. The resultant Departure from Nucleate Boiling (DNB) penalty reduces available generic margin. As an interim solution, HL&P revised operating procedures to ensure adequate margin to DNB by maintaining reactor coolant system (RCS) flow at or above 400,000 gpm for 100% power operation. Further safety analyses for Unit I have been completed which support operation at the Technical Specification RCS flow rate of 395,000 gpm. Incorporation of the results of the safety analyses into the design basis as discussed in the FSAR and Technical Specifications would require NRC eview and approval. In Reference 1, UL&P committed to submit these revisions by March 1, 1989.

However, these analyses show that compensating for the flow anomaly essentially requires all of the generic DNB margin necessary to accomodate the effects of rod bow in future cores.

HL&P plans to reevaluate the DNB ratio using the WRB-1 correlation instead of the W-3 R-grid correlation currently used for South Texas. This reevaluation will be performed prior to the Unit I refueling this summer. The expected result will provide for more " generic margin" available to offset the effects of the reactor coolant system flow anomaly and rod bow penalty in future cycles.

L4\NRC\ef A Subsidiary of liouston Industries incorporated f g 8903090171 890301 PDR ADOCK 05000498 P PT:C

ST-HL-AE-3003 Houston I ighting & Power Company File No.. C26 South Texas Project Electric Generating Station Page 2 This change to the DNB correlation constitutes a change to the licensing basis and therefore requires a submittal to the NRC, subsequent review and NRC approval prior to startup of Unit 1 after refueling. The WRB-1 correlation has been previously reviewed and approved for other plant applications by the NRC, Since the WRB-1 submittal required to support startup of Unit 1 will be made on or about March 30, 1989, HL&P will not submit the previously committed analyses to support operation at the RCS flow rate of 395,000 gpm to the NRC by March 1, 1989. The interim RCS flow requirements of 400,000 gpm will be maintained until NRC approval of the change to the DNB correlation.

If you should have any questions on this matter, please contact Mr.

A. W. Harrison at (512) 972-7298.

f M. A. McBurnett Manager, Operations Support Licensing SDP/hg i

9 L4\NRC\ef

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l Houston Lighting & Power Company Sf{HLAE;3003 South Texas Project Electric Generating Station pyg, 3 cc:

Regional Administrator, Region 'V Rufus S. Scott Nuclear Regulator'j Commission Associate General Counsel 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 1700 Houston, TX 77001 George' Dick, Project Manager U.S. Nuclear Regulatory Commission INPO Washington, DC 20555 Records Center 1100 Circle 75 Parkway Jack.E. Bess Atlanta, GA 30339-3064 Senior Resident Inspector / Unit 1

- c/o U.S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission 50 Bellport Lane P. O. Box 910- Bellport, NY 11713 Bay City, TX 77414 J. I. Tapia Senior Resident Inspector / Unit 2 c/o U.S. Nuclear Regulatory Commission P. O. Box 910 Bay City, TX 77414 J. R. Newman, Esquire Newman & Holtzinger, P.C.

1615 L Street, N.W.

Washington, DC 20036 R. L. Range /R. P.-Verret Central Power & Light Company ,

P. O. Box 2121 Corpus Christi, TX 78403 R. John Miner (2 copies)

Chief Operating Officer City of Austin Electric Utility 721 Barton Springs Road Austin, TX 78704 R. J Costello/M. T. Hardt City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Revised 12/21/88 L4\NRC\ef

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