Overall station control at Hunterston A

Design or analysis of nuclear-power-plant overall-control systems involves transient representation the behaviour of the reactors, boilers, turbines and ancillary plant. The representation of 2-phase transient heat transfer in evaporators and the transient behaviour of steam drums is particularly important. Typical system representations may contain 150 ordinary differential equations, many of them nonlinear. These are solved on analogue or digital computers; the system general controllability is first established, suitable values for the control parameters are determined, and the system behaviour in normal operating and fault conditions is then studied in detail. Commissioning-test transients are simulated for guidance during system commissioning; the test results establish the suitability of the control system and the validity the analytical approach. In the paper the development of the representation of the overall plant-control system of the Hunterston nuclear generating station is outlined. Examples are given of transients predicted analytically and obtained in practice. The test results show that the system works satisfactorily, and suggest that an analytical approach of the complexity outlined enables the behaviour of the plant and control system to be predicted adequately from the practical point of view.