Testing of improved algorithms controlling energy release in VVÉR-1000 in maneuvering regimes at the Tianwan nuclear power plant (China)

Abstract

The salient features of improved algorithms adopted at the Tianwan nuclear power plant for controlling the energy released in a VVÉR-1000 core are examined. The optimal configuration of the controlling groups is chosen in the first two power-generating units, the reactor power can be varied automatically under the control of an automatic power regulator, the boron regulation system makes it possible to determine the first-loop makeup automatically, and a modern version of the Imitator Reactora program has been installed. The results of testing the algorithms in the No. 1 unit in regimes with single and cyclic (daily) power maneuvers are presented. The tests of single power maneuvers were combined with dynamic tests of equipment. The operation of the power-generating unit in a daily load schedule was tested separately. Five daily load-change cycles were conducted during these tests.Improved algorithms consist of a complex of modern means adopted in new power-generating units at nuclear power plants for controlling the energy release in a VVÉR-1000 reactor. This complex includes a new arrangement of groups of control rods and methods for moving them inside the core, a procedure for monitoring energy release, means for providing information to the operator, and the control algorithms themselves (the sequence of actions taken by the operator). Such algorithms have been partially adopted in the No. 1 unit of the Volgodonsk (2001) nuclear power plant and completely adopted in the Nos. 2 and 3 units of the Khmel'nitskaya (2004) and Kalinin (2005) nuclear power plants, respectively, and the first two units in the Tianwan nuclear power plant (2007).Fundamental Features of the Algorithms. By definition, an increase of the axial offset corresponds to a redistribution of the power release into the top half of the core. The concepts of instantaneous (AO) and equilibrium (AO*) offsets, offset-offset, and offset-power phase diagrams are used [1,2]. The information provided to the operator is based on the use of the Imitator Reaktora computational program [3]. Free controlling groups of regulation rods with numbers 10, 9, and 8 ( Fig. 1a) are used to control the energy released in the core under normal conditions. These rods can be moved in manual or automatic regimes, individually, or with motion transferred from group to group downward or outward by 50 and 100% of the core height, respectively. Group 10 (working group) is always present in the core, and groups 9 and 8 are inserted into the core when the reactor is unloaded and when xenon fluctuations are suppressed. Xenon fluctuations are suppressed by maintaining a constant or equilibrium offset [4] or by spatially localizing the xenon processes [5].

Investigation of xenon transient processes in VVER-1000 at the Tianwan nuclear power plant (China)

“…At the end of a run, they can be of a divergent character. When necessary, to prevent the local power from exceeding the admissible level, the axial xenon oscillations are suppressed by moving groups of control rods [3,4]. The diametric oscillations are excited when the movement of the control rods is asymmetric, for example, one rod drops.…”

Integral and axial xenon oscillations superposition and vver-1000 core energy-release stability

“…Then additional control actions with operator participation will be required to suppress the xenon oscillations. For this, the regulations provide special control algorithms [5].…”

Development, introduction, and current state of the computational program “reactor simulator”

“…Its prototype is the well known program BIPR-7 [2], which is used mainly for planning fuel loading of the core. 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 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:…”

“…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]. 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].…”