Currently operated VVI~R-1000 reactors operate in base-load support, and their standard data-acquisition and computing systems are designed in the main to maintain a steady state in the reactors. However, there are often deviations from base load operation, and a reactor may operate in a transient state several times during a run, which requires management in states far from equilibrium. Also, new designs for nuclear stations containing VVER-1000 envisage load following on the daily power graph.The operator should thus provide optimum management over conditions more complicated than base load ones, which requires appropriate data support. Such facilities have been incorporated at foreign nuclear power stations such as the BEACON system produced by Westinghouse [1].The need for similar systems for VV~R stations is reflected in the requirements of the state standard. For example, according to GOST R 50088-92 for VVI~R stations, when the reactor operates in the transient state, there should be provision for calculating the current state and forecasting its behavior, and also support to the operator to choose the optimum management.The "reactor simulator" program has been written for simulating load-following modes of Wt~R-1000 reactors. The first version is available, which does not require direct installation in the nuclear station. Instead, it is used off-line for examining load-following WI~R-1000 states and also for analyzing typical situations and for forecasting planned load following at nuclear stations.The functions of the "reactor simulator" program are briefly as follows. General Information. The program is a universal means of simulating the VVI~R-1000 in nonstationary states and is intended for forecasting in managing stations and also for use in design and research to improve fuel cycles and reactor management algorithms. Fortran-95 is used. The program works efficiently on personal computers of PC-AT/486 class or above.Reactor Model. Tile part dealing with the neutron physics (with a two-group diffusion model) and with the accumulation of wastes and the variations in t35Xe and 149Sm concentrations is the same as that in the BIPR-7 program [2]. The xenon kinetics are simulated together with calculations on the nonstationary 149Sm concentration and the fuel burn-up. In initiation and forecasting modes, one considers the nonequilibrium 135Xe concentration, while one considers the equilibrium one in load burn-up and archive translation modes.A major feature of the program is that the working control rod groups can occupy any positions, not merely ones that are multiples of the height step in the net used in the BIPR-7, and this is attained by use of a special interpolation for the neutron-physics constants.Basic Functions. The program implements the following basic functions: 1) calculations on reactor states and nonequilibrium fuel burn-up and 149Sm and 135Xe concentrations; 2) calculating the linear fuel pin power; 3) adjustment to the current state on the basis of the history and forecasting the subsequ...

Imitator reaktora") is a computational program intended for modelling the operation of the VVER-1000 reactor [1]. Its prototype is the well known program BIPR-7 [2], which is used mainly for planning fuel loading of the core. Unlike the earlier program, RS is oriented toward providing real-time information support to the operator of a nuclear power plant.At first, the functions of RS supplementary to BIPR-7 were developed with the aim of providing means of visualization and interactive control of the program simulating the control of the reactor by the operator of a nuclear power plant. At the same time, the program was checked using operational data from reactors at nuclear power plants, so that the following changes were made in the neutron physics subprogram:• the ability to calculate the state of the reactor with arbitrary penetration of the control rods into the core (BIPR-7 only permitted discrete positions coinciding with the boundaries of the computational layers); this is achieved by interpolating the properties of the fuel for a computational cell with absorbing control rods partially inserted into it. This enhanced the accuracy of the calculation of the height distribution for the energy release without having to increase the number of computational layers along the height of the core; • the program can be adjusted to real, generally nonstationary distributions of the concentration of 135 Xe in the core [3].By moving the controls or changing the boundary conditions at the end reflectors of the core (two alternative modes of running the program) the calculated and measured (i.e., specified by data from the internal control system of the reactor, SVRK) axial offsets of the distribution of the energy release can be brought into agreement. Hence, after simulating the reactor operation for a certain time the calculated and real distributions of the xenon concentration in the core converge, as is necessary if the accuracy of the calculation of the current state of the reactor is to be increased and its operation is to be predicted reliably; • a functionality has been developed for evaluating the microscopic distribution of the energy release [4] by superimposing the generally nonstationary distribution of the local power obtained with RS on a data base of values of the microdistribution obtained from the PERMAK program [5] for a set of stationary states of the reactor. This functionality is currently being modified for on-line operation. The RS program has been certified twice by the Russian Federation GAN, in 1998and 2002 (Certification No. 138 of February 21, 2002.Since 2001, RS has been developed as a means of information support for the operators of a nuclear power plant. In this capacity it is an essential part of the improved algorithms for controlling the energy release of the reactor core used in most new VVER-1000 power production units [6,7]. At present, RS is in use as part of a modernized internal reactor con-