NUREG/IA-0235 International Agreement Report Numerical Analysis of Mixing Factors in the RPV of VVER-440 Reactor Using the TRACE Code Prepared by: P. Heralecky, M. Blaha TES Ltd Prazska 597 674 01 Trebic, Czech Republic A. 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Agreement Report Numerical Analysis of Mixing Factors in the RPV of VVER-440 Reactor Using the TRACE Code Prepared by: P. Heralecky, M. Blaha TES Ltd Prazska 597 674 01 Trebic, Czech Republic A. Calvo, NRC Project Manager Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 May 2010 Prepared as part of The Agreement on Research Participation and Technical Exchange Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP) Published by U.S. Nuclear Regulatory Commission ABSTRACT Experimental investigations of coolant mixing under steady state conditions at the Dukovany (Czech Republic) WER-440 NPP were performed. The main goal of these experiments was to evaluate the mixing factors under normal operations condition. An extensive TRACE input deck of VVER-440/213 reactor was developed in frame of R&D project 1 H-PK/61 in the TES Company. The TRACE input deck of VVER-440/213 reactor includes the reactor pressure vessel, the core and all important RPV internals. This paper contains some post-test analyses of the NPP Dukovany experiments using TRACE code V4.160 in order to generate background data for the forthcoming standardization procedure. There was performed a RPV nodalisation study to analyze influence of division of RPV into theta-parts on the calculated mixing factor. The purpose of performed TRACE analyses is to assess the capability of the TRACE code and the developed input deck to solve coolant mixing problems in VVER-440 type of reactors. iii CONTENTS Paqe ABSTRACT ...................................................................................................................... iii ACKNOW LEDG EM ENT ................................................................................................. vii ABBREVIATIO NS ..................................................................................................... viii 1. Introduction ........................................................................................................... 1-1 2. Plant description .................................................................................................... 2-1 2.1 The reactor pressure vessel .......................................................................................... 2-1 2.2 The core ......................................................................................................................... 2-2 2.3 The reactor coolant system ............................................................................................ 2-2 2.4 The main operational parameters .................................................................................. 2-3 3. The TRACE Code ................................................................................................... 3-1 3.1 Mixing phenomena modelling in the TRACE code ......................................................... 3-1 3.2 The TRACE code assessment ....................................................................................... 3-2 3.2.1 Code assessment with real plant data ............................................................... 3-2 3.2.2 W ER typical features related to code assessment ........................................... 3-3 4. M ixing Factors ...................................................................................... ..................... 4-1 4.1 Measurements at NPP Dukovany ................................................................................. 4-2 4.2 Measurement uncertainty ............................................................................................... 4-4 5. Input m odel description ........................................................................................... 5-1 5.1 8-Theta TRACE model ................................................................................................... 5-1 5.2 16-Theta TRACE model ................................................................................................. 5-1 5.3 Validation of the TRACE models basic thermo-hydraulics ............................................. 5-2 6. Results .................................................................................................................... 6-1 6.1 Experiment at the 1-st unit of NPP Dukovany ................................................................ 6-1 6.1.1 8-ThetaTRA CE model results ............................................................................. 6-1 6.1.2 16-ThetaTRA CE model results ................................ 6-4 6.1.3 R6sume of the TRACE VESSEL component nodalisation study ....................... 6-6 6.2 Experiment at the 4-th unit of NPP Dukovany ................................................................ 6-7 6.2.1 8-ThetaTRA CE model results ............................................................................. 6-8 6.2.2 16-ThetaTRACE model results ..........................................................................