Fault detection and characterisation in pressurised water reactors using real-time simulations

Abstract

The use of real-time plant simulators running in parallel with a nuclear plant to predict the control system behaviour and highlighting unexpected plant behaviour is presented. The study is performed on a 910 MW Generation II Framatome Pressurised Water Reactor model and simulator. By simulating the plant behaviour in real-time whilst comparing it with the real-time transient the plant is following, a complete second set of expected control operations and simulated plant measurements is generated. This enables the calculation of the unknown set of variables introduced into the plant as a fault condition. The benefit of such a system is that plant faults that are too small to detect (especially during transients when the plant operating point is moving around) can be identified as unexpected or faulty plant behaviour. The behaviour of the control system is also continually predicted so the effect of the control system compensating for fault symptoms (which in most cases hides the fault condition) is used to characterise the fault as a control variable acting on the plant. The approach is illustrated by simulating a specific fault, small enough to go undetected for an extended period of time, during a typical transient. This is continually compared with a plant simulation, simulating the same transient without the fault. Using the described methodology, the fault is detected and characterised long before the plant safety is jeopardised or the fault is detected by the conventional protection system.