ML20128B810

Safety Evaluation Accepting Methodology Described in Topical Rept RXE-91-002 Reactivity Anomaly Events Methodology for Reload Licensing Analyses for CPSES

ML20128B810
Person / Time
Site:	Comanche Peak
Issue date:	01/19/1993
From:	Office of Nuclear Reactor Regulation
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ML20126H551	List: ML20126H549 ML20128B722 ML20128B810
References
NUDOCS 9302030181
Download: ML20128B810 (2)

Text

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\..../ SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACJDR REGULATION RELATING TO REACTIVITY ANOMALY EVENTS METHODOLOGY TOPICAL REPORT RXE-91-002 TEXAS UTILITIES ELECTRIC COMPANY COMANCHE PEAK STEAM ELECTRIC STATION. UNITS 1 AND 2 DOCKET NOS. 50-445 AND 50-446

1.0 INTRODUCTION

By letter dated May 31, 1991, Texas Utilities Electric Company (TV Electric) submitted the topical report RXE-91-002, entitled " Reactivity Anomaly Events Methodology". The topical report describes the methods and models proposed for TV Electric application to the reload analyses of Comanche Peak Steam Electric Station Units 1 and 2 (CPSES). The report includes a descri) tion of the computer codes and modes, and the qualification of these metaods. The CPSES methods for performing transient calculations are described in detail, 2.0 EVALUATION Topical Report RXE-91-002 describes the TU Electric methodology for performing the event analyses for the CPSES Final Safety Analysis Report (FSAR) Chapter 15 events characterized as reactivity anomalies. Specifically, this report addresses those events described in Section 15.4 of the CPSES FSAR. The reactivity anomaly events include transients that are initiated by. movement of the control rods or changes in the reactor coolant system (RCS) boron concentration, and those events resulting from mispositioning of control rods or fuel assemblies. The methodology described in this report expands on methods previously developed by TU Electric related to core reload design, core thermal-hydraulic analysis and system thermal-hydraulic analysis.

The CASMO-3 computer code was used to generate fuel assembly cross sections.

CASMO-3 is a multi-group, two-dimensional transport theory code utilized for burnup calculations on BWR and PWR assemblies. Steady-state three-l dimensional core neutronics calculations are performed with SIMULATE-3. The l SIMULATE-3 computer code is used to determine reactivity coefficients,

! kinetics parameters, control-rod worth, multi-dimensional power distributions, l and event-specific axial power shapes.

1 The CPSES core thermal-hydraulic model employs VIPRE-01 to calculate the i thermal-hydraulic state and the core minimum departure from nucleate boiling l ratio (MONBR). The VIPRE-01 model includes a detaile.d fuel model which allows the determination of the fuel pellet temperature distribution.

I 9302030181 930119 i PDR ADOCK 05000445 l P PDR l

0 The staff reviewed and evaluated the methodology described in Topical Report-RXE-91-002 for analyzing and qualifying core physics methods, and its intended use at CPSES. The staff was aided by-the technical assistance of Brookhaven National Laboratory (BNL). The evaluation and findings are described in detail in the BNL technical evaluation report (TER) which is enclosed as an attachment to this report.

3.0 CONCLUSION

The staff finds the methodology described in Topical Report RXE-91-002

" Reactivity Anomaly Events Methodology" acceptable for reload licensing analyses for CPSES, subject to the applicable limitations and restrictions presented below:

1. Since supporting methodologies, as described in Topical Report RXE-91-002, can have significant impact on the consequences of the reactivity events, it is the licensee's responsibility to ensure that the application of the RXE-91-002 methods are carried out with approved versions of these related methods (Section-3.1 of attachment).

2. A generic overpressurization analysis for the control rod ejection event is provided in the CPSES FSAR. While this analysis is believed to be generally bounding, it is the licensee's responsibility to confirm conservatism in the FSAR overpressurization analysis for each CPSES reload core design.

3. The TER conclusion restricts the use of the TU Electric point kinetics rod ejection analysis to reload designs similar to the CPSES cycle-1 benchmark, and use of the conservatism utilized in the scram reactivity analysis. If significantly different fuel designs are introduced or operating conditions vary from those included in the benchmark data base, or if the conservatism in the scram reactivity analysis is relaxed, the rod ejection analysis will require requalification.

4. The uncertainty values and bases used in the statistical combination of uncertainties method must be provided in the cycle-specific application of the RXE-91-002 methodology.

Attachment:

Technical Evaluation Report Principal Contributor: A. Attard Date: January 19, 1993