Fault tolerant control for increased safety and security of nuclear power plants

在核电站等安全关键系统中，对可靠性、安全性和容错性的要求很高。故障危及工厂安全，导致工业流程运行效率低下，并降低部件寿命。在这样的安全关键系统中，设计能够容忍潜在故障的控制系统是有用的，以提高可靠性和可用性，同时提供期望的性能。一种能够自动容忍部件故障，同时保持期望的性能和稳定性的控制系统称为容错控制系统。容错控制方法允许控制系统在故障条件下以最小的性能和稳定性降级运行，防止局部、随机或有意的故障发展为灾难性的系统故障，导致可能对人类生命、设备、基础设施或环境造成严重后果的事故。在采取补救措施修复或消除故障时，容错有助于减少故障可能造成的破坏影响。拟议的工作将为压水堆核电站开发一个分级容错控制方案，该方案将在三个层次上定义：执行、协调和管理。执行级包括反应堆、蒸汽发生器和汽轮机，通过执行器执行由上级产生的控制动作，感知相关的被控对象变量，并将该信息传递给上级。中间层充当工厂经理层和执行层之间的协调器。为了最大限度地发挥其能力，协调级别将包括一个由四个不同控制器组成的库，这些控制器将被设计为能够容忍不同严重程度的故障，并且将有一种机制来根据管理级别的要求根据工厂的情况选择最合适的控制器。协调级还包含诊断和预测系统，该系统将收集工厂数据和有关部件使用寿命的知识，以检测和表征与传感器相关的故障和其他工厂故障。顶层管理工厂性能监控、工厂状况评估，并将命令传递给协调层。此外，管理层向与操作员交互的中央命令、控制和通信系统发送操作数据并从其接收指令。该项目还将涉及开发核电厂模拟器，该模拟器将用于实时测试将要开发和实施的分级容错控制方案，生成有关工厂在正常和故障条件下的行为的数据，并生成用于控制器设计目的的工厂或工厂部分的简化模型。实时测试将允许在接近真实工厂遇到的计算环境中评估发展，从而确保要开发的控制方法尽可能现实。这项工作将与印度专门研究核能的研究机构巴巴原子研究中心合作进行，并将受益于专门从事核安全管理和培训的英国组织STS Core的参与。

In safety-critical systems, such as nuclear power plants, the demand for reliability, safety and fault tolerance is high. Faults compromise plant safety, cause inefficiencies in the operation of industrial processes and reduce component life. In such safety-critical systems, it is useful to design control systems which are capable of tolerating potential faults to improve the reliability and availability while providing a desirable performance. A control system which can automatically tolerate component malfunctions, while maintaining desirable performance and stability properties is said to be a fault-tolerant control systemFault tolerant control approaches allow control systems to operate under fault conditions with minimal degradation of performance and stability, preventing localised, random, or intentional faults from developing into catastrophic system failures leading to accidents that may have severe consequences to human life, equipment, infrastructure, or the environment. Fault tolerance helps to reduce the damaging effects that faults can have while remedial action is taken to repair or eliminate the fault.The proposed work will develop a hierarchical fault-tolerant control scheme for PWR nuclear power plants which will be defined over three levels: execution, coordination and management levels. The execution level, which includes the reactor, steam generator and turbine, implements the control actions generated by the higher levels through actuators, senses relevant plant variables, and passes this information to the higher levels. The middle level acts as a coordinator between the plant manager level and the execution level. To maximise its capabilities, the coordination level will include a bank of four different controllers that will be designed to tolerate faults of different severity, and there will be a mechanism to select the most appropriate controller given the circumstances of the plant as required by the management level. The coordination level also contains a diagnostic and prognostic system, which will the plant data and knowledge about the useful life of components to detect and characterise sensor related and other plant faults. The top level manages plant performance monitoring, plant condition evaluation, and passes commands to the coordination level. In addition, the management level transmits operational data to and receives instructions from a central command, control, and communication system which interfaces with human operators. The project will also involve the development of a nuclear plant simulator which will be used to test in real-time the hierarchical fault tolerant control scheme to be developed and implemented, to generate data about the behaviour of the plant under normal and fault conditions, and to generate simplified models of the plant, or parts of the plant, to be used for the purposes of controller design. The real-time tests will permit to assess the developments in a computational environment that is close to what would be encountered on a real plant, hence ensuring that the control methods to be developed are as realistic as possible. The work will be carried out in collaboration with Bhabha Atomic Research Centre, an Indian research institution that specialises in nuclear energy, and will benefit from the involvement of STS Nuclear, a UK organisation that specialises in nuclear safety management and training.