Development and validation of the automatic control rods operation system for ABWR

TOSHIBA has introduced the first automatic control rods operation system for the first ABWR (advanced BWR) in the world. The automatic control rods operation system, which is named APR (Automatic Power Regulator), has core critical approach control, pressurization control and power control function and covers the operation from reactor startup to about 70% electrical power. APR calculates the manipulating demand of control rods from feedback signals, that are neutron flux, calculated temperature rise ratio and electrical power. The manipulating demand of control rods is dispatched to an RC&IS (rod control and information system) as an insertion/withdrawal signal. The control rods to be operated are automatically selected by the RC&IS. In the development of this system, a 3D core simulator was adopted to verify the control algorithm and to validate this system. Prior to startup tests, a 3D core simulator was used to precisely predict dynamics and to verify control parameters. In parallel with the introduction of APR to ABWRs, operators were trained to operate the APR with a plant wise simulator, in which the 3D core simulator is adopted for precise simulation of flux behavior. Through this training, operators can obtain the skill to operate the APR system under normal plant condition and abnormal condition such as plant transients or APR failure.