On the Use of Dynamic Modelling for the Design of IRF

Abstract

The multi-purpose high-flux Irradiation Research Facility (IRF) reactor has been proposed by AECL as a replacement for the venerable NRU reactor at Chalk River, and the pre-project design of IRF is currently underway. As part of this design effort, we are currently modelling the dynamic response of the reactor and especially that of the Reactor Regulating System (RRS). The tool chosen for this work is the MATRIXx family of programs, including XMath, SystemBuild and DocumentIt. The SystemBuild tool allows users to specify a complete model by graphically interconnecting a set of modules (SuperBlocks) and/or "primitives". Each module, in turn, can be defined graphically by interconnecting a further set of sub-modules and/or "primitives". The system supports both continuous (analog) as well as discrete (digital) modules at the same time. Thus, it is possible to accurately model a continuous process coupled to its computer-based control system. The frequency response of the system can be extracted from the same model. The model will be used for control system stability analysis and to choose appropriate design parameters for various controllers and dynamic compensators within both the RRS and other important controllers in the system. The whole system can then be tested using various manoeuvres such as start-ups, shutdowns and step perturbations. It can also be used to verify that the design functions well under extreme conditions such as those which might occur at the beginning or end of the fuel cycle, or when attempting to override a poison-out. The model can also be of practical assistance to other designers in choosing the various parameters involved (e.g., step size of the stepping motor drives for the control absorber rods (CARS), or rundown time of the main primary coolant system pumps). The model currently consists of: point- or 7-node neutron kinetics with temperature and xenon feedback, 1 or 2 sets of log, linear and log rate amplifiers, the RRS (flux) control algorithm, 1 or 2 banks of CAR drives, the primary coolant circuit with 2 pumps and two main heat exchangers, and secondary temperature control valve(s) and controller(s). This model-based design process has proven very useful for the MAPLE reactor design, and it is expected to be equally important in designing the even more complex IRF system.