NOC-AE-0037, Submits Annual Rept Re Revs to Accepted ECCS Evaluation Model,Per 10CFR50.46(a)(3)(ii)

Submits Annual Rept Re Revs to Accepted ECCS Evaluation Model,Per 10CFR50.46(a)(3)(ii)

ML20203K572
Person / Time
Site:	South Texas
Issue date:	12/17/1997
From:	Leazar D HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NOC-AE-0037, NOC-AE-37, NUDOCS 9712230011
Download: ML20203K572 (5)

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December 17,1997 NOC-AE-0037 File Nos.: G03.I1 G03.17 M33.02 10CFR50.46 STl: 30497510 U. S. Nuclear Regulatory Commission Attention: Document Comrol Desk Washington, DC 20555 South Texas Project Electric Ge ierating Station Units 1 &2 Docket Nos. STN 50-498, STN 50-499 10CFR5MfLAnnuaLRepon of ECC SWcmAlodel Revisions AnLARay. Report Of Significant ECCS MgleLChanges

References:

1) Letter from D. A. Leazar to NRC Document Control Desk,"10CFR50.46 Aonual Report of Emergency Core Cooling System Model Revisions," dated December 11,1996 (ST-llL-AE-5514).

2) Letter from D. A. Leazar to NRC Document Control Desk,"10CFR50.46 Thirty Day Report of Significant Changes to the Accepted Emergency Core Cooling System Model," dated July 17,1997 (ST-HL-AE-5698).

3) Letter from D. A. Leaza, to NRC Document Control Desk, "10Cl>R50.46 Thir;y Day Report of Significant Changes to the Accepted Emergency Core Cooling System Model For Unit 1," dated November 4,1997 (ST-IIL-AE-5783)

Pursuant to 10CFR50.46(a)(3)(ii), the South Texas Project (STP) is submitting this annual report concerning revisions to the accepted Emergency Core Cooling System (ECCS) evaluation model at STP Units 1 and 2. During 1997,ie Small Break Loss of Coolant Accident (SBLOCA) evaluation was reperformed, the Unit i and Unit 2 Large ' Break Loss of Coolant Accident LBLOCA evaluations were separated and the Unit 1 LBLOCA evaluation was reperformed.

Also, during 1997 the Peak Cladding Temperature (PCT) assessments were applied to the Unit 2 LBLOCA evaluation result. The sum of the absolute values of the PCT assessments for the Unit 2 LBLOCA evaluation exceeds 50 *F. The Unit 2 LBLOCA evaluation assessments therefore constitute a significant change as defined in 10CFR50.46.

In Reference 2 the NRC was notified of the reperformance of the South Texas Project Unit I and f Unit 2 SBLOCA analysis. Reference 2 reported a revised Feak Cladding Temperature, including all assessments, of 1860*F. The reanalysis represented a 198 F change from previous year end n

SBLOCA PCT of 2158 'F(Reference 1). gjV I 9712230011 971217 PDR ADOCK 05000490 llllllQlll]l{gll

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NOC-AE-0037 File Nos.: G03. I 1, G03.17 M33.02 Page 2 In support of ZIRLO clad fuel for STP Unit 1 Cycle 8, the STP Unit I and Unit 2 LBLOCA evaluatiens were separated and the Unit I analysis was reperformed. The reanalysis, and resulting Unit i LDLOCA PCT of 2132'F, were reported to the NRC in Reference 3. The reanalysis represented a 27 'F cnar.ge from previous year end LBLOCA PCT of 2159 'F (Reference 1).

In addition to the reana*yses perfornied in 1997, several new PCT assessments were applied in 1997. The asseasme .ts result in a 23 *F reduction in the Unit 2 LBLOCA analysis PCT.

The SBLOCA and LBLOCA ycar end PCT rackups are presented in Attachment 1. The new 1997 PCT assessments are discussed in Attachment 2.

Per the STP Unit I and Unit 2 SBLOCA evaluation model the PCT is 1860 F. For the Unit 1 LBLOCA evaluation model, the PCT is 2132*F. For the Unit 2 LDLOCA evaluation model, the PCT is 2136 F. The acceptance criteria for all models continue to be satisf'ied.

W1.U the SBLOCA PCT remains below the 10CFR50.46 acceptance criteria of 2200 'F, the analysis is currently being revised to implement an explicit four loop model. The revised analysis should climinate many of the assessments that currently apply to the SBLOCA analysis. The reanalysis is expected to be completed in 1998.

The Unit 2 LBLOCA analysis is expected to be replaced with the svne analysis used to mpport the Unit I Cycle 8 ZlRLO fuel in 1998. This will be done to reflect the introduction of ZlRLO fuel in Unit 2 Cycle 7.

If you should have any questions concerning this matter, please contact Mr. Charles R. Albury at (512) 972-8901 or me at (512) 972-7795. ,

.C.

D. A. Leazar Director.

Nuclear Fuel and Analysis JMW/kjt Attachments: 1) 1997 Year End PCT Rackups

2) 1997 PCT Assessments e.\wp\nt\ntc-wk\ misc-9n0037A*

sTI: A497510

NOC-AE-0037 File No.: G03.I1

, G03.17 M33.02 Page 3 Ellis W. Merschoff Jon C. Wood Regional Administrator, Region IV Matthews & Branscomb U. S. Nuclear Regulatory Commission One Alamo Center 611 Ryan Plaza Drive, Suite 400 106 S. St. Mary's Street, Suite 700 Arlington, TX 76011-8064 San Antonio,TX 78205 3692 ThomasW. Alexion Institute of Nuclear Power Project Manager, Mail Code 13113 Operations - Records Center U. S. Nuclear Regulatory Commission 30 Galleria Parkway

- Washington, DC 20555-0001 .tlanta, GA 30339-5957 David P. Loveless Richard A, Ratliff Sr. Resident inspector Bureau of Radiation Control c/o U. S. Nuclear Regulatory Comm. Texas Department ofllealth P. O. Box 910 1100 West 49th Street Bay City, TX 77404-0910 Austin, TX 78756-3189 J. R. Newman, Esquire C. R. Crisp /R. L.Balcom Morgan, Lewis & Bockius llouston Lighting & Power Co.

1800 M Street, N.W. P. C. Box 1700 Wahington, DC 20036-5869 Ilouston, TX 7?251 M. T. liardt/W. C. Gunst Central Power and Light Company City Public Service ATTN: G. E. Vaughn/C. A. Johnson P. O. Box 1771 P. O. Box 289, Mail Code: N5012 San Antonio,TX 78296 Wadsworth,TX 77483 J. C. Lanicr/A Ramirez U. S. Nuclear Regulatory Commission l

City of Austin Attention: Document Control Desk Electric Utility Department Washington, D.C. 20555-0001 721 Barton Springs Road Austin,TX 78704 I .

Attachment 1 NOC-AE-0037 Page1of1

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1997 YEAR END PCT RACKUPS Unit 1 and Unit 2 SBLOCA:

1996 year end SBLOCA PCT (Reference 1) - 2158 *F Change in PCT due to the SBLOCA reanalysis (Reference 2) - 198 'F

- Revised Year End SBLOCA PCT 1860 'F Unit 1 LBLOCAt Previous Unit.1 LBLOCA PCT (Reference 11- 2159 'F Change in PCT due to the LBLOCA reanalysis (Reference 3) - 27 'F Revised Year End Unit 2 LBLOCA PCT 2132 *F Unit i nBLOCA:

Previous Unit 2 LBLOCA PCT (Reference 1) 2159'F Redefinition of the Limiting LBLOCA case -38'F Error discovered associated with the translation of fluid properties from the SATAN Code to the LOCTA Code ~ 15 'F Revised Year End Unit 2 LBLOCA PCT 2136 F i

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Attachment 2 NOC-AE-0037 Page1of1 I

1997 PCT ASSESSMENTS Redefinition of the Limitine LHLOCA case:

During the LBLOCA analysis for ZIRLO cladding, an overconservatism was noted in the rod-heat-up boundaly conditions for the UFS AR Co = 0.6, Maxim"m Safeguards { Max SI) case. This case had previously been identified as the limiting LBLOCA case in the STP UFSAR, since it ,

resulted in the highest calculated PCT of all reported cases. However, further evaluation of this case (supported by separate studies), identified that the Max SI case resulted in the highest PCT as a direct result of the excessive coriservatism in the rod heat-up boundary conditions. The evaluation and consideration of the transient physics led to the conclusion that the Co = 0.6, Min SI case should be the limiting case, The PCT benefit associated with this correctior. reflects the difference in the previously reported Analysis Of Record PCT (2177 'F) for the Max SI case and the previously reported Analysis Of Record PCT (2139 'F) for the Min SI case.

i Translation Of Fluid Properties From SATAN To LOCTA:

An error was discovered in the coding related to the translation of fluid properties from the SATAN Code to the LOCTA Code. Representative plant calculations were used to evaluate the PCT impact of this error The calculations resulted in a PCT impact of 15 'F.  ?"

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