Calculation of reactivities using ionization chamber currents with different sets of kinetic parameters for reduced scra
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ulation of Reactivities Using Ionization Chamber Currents with Different Sets of Kinetic Parameters for Reduced Scram System Efficiency in the VVER1000 of the Third Unit of the Kalinin Nuclear Power Plant at the Stage of Physical StartUp M. N. Zizina, S. N. Zizinab, L. V. Kryakvinb, V. A. Pitilimovb, and V. A. Tereshonokb a
Russian Research Centre Kurchatov Institute, pl. Kurchatova 1, Moscow, 123182 Russia b JSC VNIIAES, ul. Ferganskaya 25, Moscow, 109507 Russia email: [email protected] Received February 18, 2010
Abstract—The effectiveness of the VVER1000 reactor scram system is analyzed using ionization chamber currents with different sets of kinetic parameters with allowance for the isotopic composition in the calcula tion of these parameters. The most “correct, aesthetically acceptable” results are obtained using the eight group constants of the ROSFOND (BNABRF) library. The difference between the maximum and minimum values of the scram system effectiveness calculated with different sets of kinetic parameters slightly exceeds 2β. The problems of introducing corrections due to spatial effects are not considered in this study. Keywords: VVER1000, scram system effectiveness, BNAB78, BNAB90, ENDF/B6, ENDF/BVII.0, TVSM, BNABRF. DOI: 10.1134/S1063778811140110
The choice of kinetic parameters and the method for their estimation substantially influence the reactiv ity in processing signals from ionization chambers obtained during transient processes; this influence is especially pronounced for the scram system effective ness. Here, the kinetic parameters are the relative yields αi of delayed neutrons and the constants λi of decay of delayed neutron precursors. This study analyzes the influence of kinetic param eters on the value of scram system effectiveness obtained using the inverse solution of the kinetic equa tion with the use of ionization chamber currents recorded in the course of measurement of the scram system effectiveness. The measurements were per formed for the first fuel load of the third unit of the Kalinin nuclear power plant in the case of operation at a minimum controllable power level at the stage of physical startup [1]. The reduction of the scram system effectiveness on February 12, 2005, at 9 a.m. (t = 362.6 s) when the rod 13–36 (ninth group) was stuck and then sent in 20 s later was considered. The corrections to the back ground current were 0.190 × 10–10, 0.180 × 10–10, and 0.105 × 10–10 for ionization chamber nos. 3, 14, and 25, respectively. The scram system effectiveness was calculated using a program written in MathCad. This program implements the integral form of the inverse solution of the kinetic equation according to the algo rithm described in [2]. The calculations were per
formed with and without the background current taken into account. The results of calculation were verified using a pro gram written in Fortran; this program implements the same integral algorithm. The results of calculations performed by S.V. Tsyganov also completely agreed with our re
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