BS IEC 62646:2012

1.1 Object This International Standard establishes requirements for the whole life cycle of operating procedures that the designer wishes to computerise. It also provides guidance for making decisions about which types of procedures are to be computerised and to what extent. Once computerised, procedures are designated as \'Computer Based Procedures\' (CBP). Enhancing safety, easing operation and increasing NPP availability have always been greatly valued aims which, during NPP operation, rely to a large extent on the operating staff and on operating procedures. Digital technology is currently contributing by providing efficient help to do this at the automation level. In addition, the use of computer technology to provide formats of operating procedures to the plant operators 1, on-line and in real time, is increasing and becoming current practice. This can be done both for normal operating situations and also as advisory formats for use in abnormal situations. When properly implemented and kept up-to-date, such operating procedures can provide enhanced support for greater safety and operator effectiveness compared to paper based procedures. Their preparation demands great care and close interaction with operators and plant designers, and will also need close cooperation with I&C designers. CBP have many common points with paper based procedures. This standard focuses only on what is specific to CBP. 1.2 CBP overview Procedures provide the operators with two types of high level elements: information, i.e. explanations or data displayed in order to enable the operator to control the pro-cess, assess the plant situation, understand operating strategies and make appropriate decisions, guidance, i.e. a set of ordered steps for prompting and helping the operator to oper-ate the process and the plant equipment. Information and guidance are combined to minimise operators errors and to optim-ise efficiency of plant operation. These elements can be of a varying level of detail depending on the procedure policy, which aims to benefit from operator experience and predefined guidelines. Computerisation of procedures can provide, according to the specified design policy: enhanced process and plant equipment information, enhanced operator guidance, optional automatic plant control. However, introducing such procedures requires attention to the following issues: defining a clear policy on the scope of procedures, level of guidance and possible direct process control for example, taking into account experience from plant operation and human capabilities as well as organisational and technological issues, designing a safe and reliable CBP system, and also providing an appropriate back-up including operating procedures covering the assumed failure of the CBP system, validating a combination of plant operation strategies, formats presentation and human capabilities, as well as digital issues, maintaining the operator in the loop, i.e. ensuring adequate priority of human action versus computerised actions and preventing the loss of knowledge. 1.3 Exclusions from this standard In order to design CBP efficiently and properly, some important inputs should have already been decided and are therefore outside the scope of this standard: functional analysis and assignment IEC 61839 specifies functional analysis and assignment procedures and gives rules for developing criteria for the assignment of functions either to operators or to systems, human factors design guidelines. ISO 11064 series of standards provides guidance on human-centered design activities throughout the life cycle of a computer-based interactive system. In addition, IEC 60964 and IEC 60965, which provide requirements and recommendations for the main control room and supplementary control point arrangements, apply to the implementation of CBP in new nuclear power plants. Complementary advice for implementing CBP in case of main control room retrofitting is given in 6.2.3 of this standard. This standard also excludes: computer security, which is necessary to protect the whole life cycle of CBP, but is not restricted to computerisation of procedures. Nevertheless, this topic is to be considered when computerising operating means. IEC 62645 deals with cyber-security, requirements on the implementation for CBP functions of software and hardware of computer systems for CBP has to be implemented in line with its safety class in compliance with IEC 61513, the organisation for maintenance of procedures. 1.4 Organisation of this standard Clause 2 lists the reference documents. Clause 3 gives definitions relevant to this standard. Clause 4 lists the abbreviations used in this standard. Clause 5 provides an overview of CBP. It presents recommendations for the development of a policy for computerisation of procedures, based on the type of procedure to be implemented. Three generic types (termed “families??) are proposed, for which general and specific guidance is provided. Guidance related to the safety requirements of CBP systems is also provided. Clause 6 gives requirements for use in different environments, inside and outside of the MCR (Main Control Room) and possibly in conjunction with paper based procedures. It then considers assistance to and coordination of operator activities. Clause 7 deals with the digital system which processes CBP. It first considers safety and non-safety requirements, then gives requirements for handling failures of this system. Clause 8 focuses on the detailed requirements and recommendations related to the functional features of CBP, from the basic ones to the most sophisticated ones, i.e. information, navigation, guidance and plant control. Miscellaneous options that could ease CBP use are also given. Clause 9 considers the CBP life cycle, from the set-up of the project to the CBP maintenance and the operator training via design and implementation.