Simulation of a regulation system under conditions of an unforeseen power reduction in an RBMK reactor

Abstract

The simulation of the dynamics and control of RBMK under real operating conditions, performed at the stage of their design and assimilation, as well as experience obtained over many years of operation of reactors of this type show that the traditional automaiic regulator (AR) does not provide the required level of automation of the control of modern power reactors with their inherent spatial instability of energy release.A significant practical step toward raising the level of automationwas the creation of a system of local automatic regulators (LAR), operating from signals generated by neutron sensors inside the reactor~ Experience in operating such systems based on RBMK has shown that their use radically raises the operating efficiency of the reactors.Together with the LAR systems mentioned above, LAR systems working from the side ionization chambers (LAR--S!C) have now been theoretically substantiated [1][2][3], tested, and put into commerica! operation in a number of blocks.With their help the problem of backup of the LAR system and reactor control at low power levels, when intrareactor sensors are inadequate. is solved quite efficiently.Automatic regulation systems in power reactors, while ensuring the required stabilization of the energy distribution in the stationary operating state of the power block, must also ensure normal implementation of an emergency controlled power reduction (A3-I-4 in RBMKi000) [4]. Since the usual efficiency of an automatic regulation system (AR, LAR, LAR-SiC), including its high-speed efficiency, is inadequate for realizing A3-I-4 conditions, this system must be supplemented by overcompensation (OC) rods.In creating an overcompensatinn system it is necessary to determine the number and distribution of OC rods relative to the rods of the regulating system~ as well as signals which will actuate them.In this work, these questions are solved for the example of an eight-zone LAR--SIC system.The LAR--SIC system makes use of the principle of asymmetry of the neutron balance operator [5], realized by selecting the locations of the actuating units at a definite distance from the monitored points.To solve the question of the distribution of OC rods, in this work we employed a procedure previously used for determining the optimal configuration of the LAR--SIC system without OC rods based on the quality criterion for the response of the system to a perturbation at all harmonics included in the solution [i, 6]. The radius of the circle on which the LAR--SIC rods are arranged is assumed to be equal to 0.4 Ro (Ro is the extrapolated radius of the reactor).We studied the operation of the LAR~-SIC system with one OC rod in each regulation channel. We assumed that the OC rods and LAR--SIC move synchronously. We varied the distance R between the LAR--SIC rod and the OC rod adjoining it and the angle | between the directions from the LAR--SIC rod to the chamber and to the OC rod. At the same time we preserved the central symmetry of the arrangement of the LAR--SIC and OC reds. From the data obtaine...