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The problems of increasing the accuracy of energy release distribution and storage monitoring up to the limits of safe operation of RBMK-1000 reactors are examined. Accuracy can be increased by automatically optimizing some constants used in the special software of the SKALA-mikro system and by periodic self-certification of the algorithm used to determine the computational error in the energy-release distribution. It is shown that tests performed by periodically scanning the core with a calibrated detector and by successively switching off the detectors give close results.It is well known [1] that increasing the monitoring accuracy of the energy release distribution increases the margin factors up to the limits of safe operation of a RBMK-1000 core with respect to a crisis of heat transfer and the linear power density of the fuel elements, decreases the true and measured coefficient of radial nonuniformity of the energy release, and in individual cases is a necessary condition for the reactor to be put into the nominal power regime after prolonged shutdown, for example, after major repairs [2]. In addition, it creates additional possibilities for optimizing the energy release distribution. Monitoring accuracy is increased primarily by individual calibration of in-reactor detectors and by determining more accurately the constants used in special software. Ordinarily, calibration is performed by periodically scanning the core with Dt-6 hafnium calibration detectors [1] and (or) by calibrating control samples for each in-reactor detector on the IRT-2000 reactor (Moscow Engineering Physics Institute), which was recently put into operation.An important function of the SKALA-mikro system is to estimate the monitoring error for the energy-release distribution of each fuel assembly, directly influencing the margin factor up to the limit of safe operation. Periodic metrological certification of the evaluation algorithm is performed using scan results and Fisher's test. In addition, automatic optimization of some constants, used in the software, and self-certification of the error in reconstructing the distribution of the energy release by mathematical analysis of the data on the real state of the core, likewise increasing the accuracy of monitoring, have been adopted in RBMK-1000.The present article compares the results of constants optimization which are obtained by scanning and processing information on the running values of the RBMK-1000 core parameters.In the first case, the ratio of the power W i p of the ith fuel assembly calculated with the "Prizma-M" computer program of the SKALA-mikro system to the power W i sc obtained by scanning a fuel assembly with a Dt-6 hafnium detector is

The most important component of reliable and safe operation of a nuclear reactor is controlling its distributed and general parameters. Different in-reactor control systems used previously and currently in NPP with RBMK are examined. The means for controlling the power release in the reactor core are examined and the methods for reconstructing the power release in RBMK are reviewed briefly.In the development of RBMK, significant attention was devoted to devising means for monitoring the distributed parameters of the core, such as the neutron flux density, coolant flow rate in fuel channels and graphite temperature, and computing systems capable of real-time calculations of safety-important parameters which cannot be measured directly, specifically, the power, margin to crisis of heat transfer, and maximum lineal power of a fuel channel [1]. The urgency of developing detectors of a new type, computational means and information processing methods was determined for RBMK by the absence of means for heat-engineering monitoring of the power of a fuel channel with boiling coolant, unstable power release and refueling an operating reactor with a large perturbation of the distributed parameters of the core.Research on in-reactor detectors and methods of processing their indications, performed at the Beloyarskaya NPP, where at the first stage coaxial γ-sensitive ionization chambers intended for monitoring the fuel-channel power were tested, played a large role in the development work. Chambers of this type with a 6 m long sensitive part, central electrode and housing, which are separated from one another by spacing insulators made of aluminum oxide, failed after operating for 3-6 months because the resistance of the insulation decreased. Subsequently, they were replaced with triaxial chambers with a guard electrode in the coupling line and in the working volume and did fail because of a drop in the resistance of the insulation [2]. At the Beloyarskaya NPP, β-emission detectors with silver emitters successfully underwent tests and subsequently served for more than 10 years as the main means for monitoring the power release in RBMK [1].The power release in the channels of RBMK built in the first phase was measured with a system performing physical monitoring of the power release distribution and centralized monitoring system SKALA, which performed mathematical processing and displayed information for the operator in a form convenient for controlling the parameters of the core.The system performing physical monitoring of the power release distribution contains 130 radial monitoring detectors D.42 with a 7 m long sensitive part, uniformly arranged along the core in the central dry sleeves of the fuel assemblies 49 and 12 height monitoring assemblies 156, placed in the cooled channels of the CPS. Each assembly 156 has seven sections are uniformly distributed along the core height, each comprising a cable and sensor with a silver filament of total length 2.6 m formed into a 36-mm long spiral. A dry sleeve for periodic calibrati...

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Testing of the computer code Reactor Operator's Adviser on the No. 3 unit of the Leningradskaya nuclear power plant showed that the recommendations given in the code increase substantially (by a factor of 1.2) the minimum margin to the P2 level for the adjusted signal from the in-reactor detectors along the radius and decrease the maximum temperature of the graphite masonry by 12°C and the maximum nonuniformity factor of the energy release distribution by 3%. Operation for 3.5 h using the Reactor Operator's Adviser code recommendations maintained the operational parameters characterizing the energy release distribution along the core radius and height within acceptable limits.The quality of the smoothing of the energy-release distribution over the volume (radius and height) of the core increases the operational safety of nuclear power plants with RBMK-1000. For this purpose, a cybernetic model of the reactor operation has been developed [1] and implemented in the computer code Reactor Operator's Advisor (SOPR) [2], which is intended for automatic optimization of the distributed parameters of the core in RBMK-1000 reactors equipped with the Skala-Micro information-measurement system. The code is also supposed to be incorporated in the complex monitoring, control, and protection system for automatic optimization of the volume distribution of the energy-release.The procedure for smoothing the energy-release distribution in RBMK-1000 is an optimization problem where the goal function with possible power increase is minimization of the coefficient K v of volume nonuniformity of the energy release or the lineal power density of fuel elements in the plateau zone with a limit on the reactor power. The latter makes it possible to decrease the neutron leakage and increase the depth of fuel burnup [3]. In both cases, the final goal function is to increase the cost-effectiveness of nuclear power plants with RBMK-1000 reactors with all safety requirements being met. In the course of optimizing the energy-release distribution, the operator or the SOPR code must take account of the effectiveness criteria: increasing the margin to the maximum admissible power of the technological channel, maintaining an operational margin for the control rods used for local automatic control in a prescribed range, not decreasing below the maximum admissible margin with respect to critical heat transfer for the lineal density of the power and masonry graphite temperature, not permitting close approach to the emergency setting of the signals from in-reactor detectors along the radius, and others. Because of the difficulty of minimizing the energy-release coefficient K v a spectrum of effectiveness criteria is used in practice and in the development of metrics. Such an approach, called simulation modeling [4], for RBMK-1000 has been implemented in the SOPR code.Operational optimization of the energy-release distribution has gone through several developmental stages. Initially, the plan was to use the method of linear programming with a matrix model...