Analysis of the uncertainties in the physical calculations of water-moderated power reactors of the VVER type by the par
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ysis of the Uncertainties in the Physical Calculations of Water-Moderated Power Reactors of the VVER Type by the Parameters of Models of Preparing Few-Group Constants V. V. Bryukhin*, K. Yu. Kurakin, and M. A. Uvakin AO OKB GIDROPRESS, ul. Ordzhonikidze 21, Podolsk, Moscow oblast, 142103 Russia *e-mail: [email protected] Received January 13, 2015
Abstract—The article covers the uncertainty analysis of the physical calculations of the VVER reactor core for different meshes of the reference values of the feedback parameters (FBP). Various numbers of nodes of the parametric axes of FBPs and different ranges between them are investigated. The uncertainties of the dynamic calculations are analyzed using RTS RCCA ejection as an example within the framework of the model with the boundary conditions at the core inlet and outlet. Keywords: uncertainty analysis, VVER, FВР, nodes of the parametric axes, RTS RCCA ejection, model with the boundary conditions DOI: 10.1134/S1063778816080044
INTRODUCTION The KORSAR/GP thermal-hydraulic computational code [1] used to carry out coupled neutronic and thermal-hydraulic calculations belongs to codes of improved estimation; it is designed to simulate the normal operating and emergency conditions of reactor plants equipped with water-moderated power reactors of the VVER type. To calculate the neutron kinetics of VVER reactor cores in the three-dimensional approximation, within the KORSAR/GP code, the KARTA program block [2] is used with the constant software prepared using the SAPFIR_95&RC_VVER software package [3]. The macroscopic constants depend on the fuel burnup, the fuel and the coolant temperatures, the boric acid concentration in the coolant, and the presence of reactivity members. We will refer to the quantities that affect the macroscopic constants as the feedback parameters (FBP). The dependence of the macroscopic constants on the FBPs is preset in the KARTA block in the form of multidimensional arrays using a definite fixed number of reference points, which allows us to pose a question about the influence of the selection of these points on the computational results. In this work, the uncertainties of the physical calculations of the VVER reactor core for different meshes of the reference values of FBPs are analyzed. When preparing the few-group constants using the SAPFIR_95&RC_VVER software package, different
numbers and values of the nodes of the parametric axes of FBPs are investigated. For the chosen formulation of the problem, the uncertainties of the dynamic calculations are analyzed by the example of RTS RCCA ejection within the framework of the model with the boundary conditions at the core inlet and outlet. PREPARATION OF THE LIBRARIES OF FEW-GROUP CONSTANTS The libraries of few-group constants are created by the SAPFIR_95 code [4]. For this purpose, first the burnup of the subchannels is calculated at the reactor parameters that correspond to the mean operating parameters and then additional calculations are carried out for the chosen power density values with the
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