IEC 60744:2018 pdf download

IEC 60744:2018 pdf download.Nuclear power plants – Instrumentation and control systems important to safety
1 Scope
This document provides requirements and recommendations for the design, construction and test of safety logic assemblies used in safety systems to perform category A safety functions (in accordance with IEC 61 226). Safety logic assemblies include logic such as the hardwired logic assembly interfacing computer-based systems to switchgear, actuators or contactors to provide trip or engineered safety feature actuations. Safety logic assemblies are significant parts of a safety system and may include voting logic between redundant channels. This document provides a general description of safety logic assemblies for safety actuators control. The principles to meet dependability objectives are presented. The main features relating to the design requirements are described and explained. Various tests and their requirements are given in order to validate the design (including the qualification tests), the manufacturing and the correct installation on site. Annex A (informative) gives a list of possible applications of safety logic assemblies. Annex B (normative) suggests a list of possible hardwired technologies with their respective requirements to design safety logic assemblies. Annex C (informative) gives explanations on dependability and its attributes to improve reliability and to reduce the final risk which compromises the safety and the availability of the NPP. The scope of this document does not address the design of a protection system, it covers only the technological and architectural solutions required to design a safety logic assembly. The design of safety systems using safety logic assemblies is covered by IEC 61 51 3. The detailed and specific functions implemented in a safety logic assembly strongly depend on the design of each reactor and are not addressed in this document. As this document is focused on I&C part of the system, the final voting logic made with power breakers is excluded from the scope of this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: • IEC Electropedia: available at http://www.electropedia.org/ • ISO Online browsing platform: available at http://www.iso.org/obp 3.1 availability ability of an item or a system to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval, given that the necessary external resources are provided 3.2 channel arrangement of interconnected components within a system that initiates a single output. A channel loses its identity where the single-output signals are combined with signals from another channels (eg; from a monitoring channel or a safety actuation channel) [SOURCE: IAEA Safety Glossary, 201 6 edition] 3.3 dependability general term describing the overall trustworthiness of a system; i.e. the extent to which reliance can justifiably be placed on this system. Reliability, availability and safety are attributes of dependability Note 1 to entry: Annex C gives clarifications on this definition. [SOURCE: IAEA Safety Glossary, 201 6 edition] 3.4 dynamic logic equipment system assembly or subassembly employing dynamic logic signals 3.5 dynamic logic signal periodically changing voltage or current, the frequency being consistent with the required system response time. The different logic states are associated with different values of one or more parameters of the periodic change, for example, amplitude, slope, repetition rate of pulses or alternations, or pulse coding Note 1 to entry: One logic state may be associated with the absence of periodic change of such a signal. 3.6 engineered safety feature actuating part of a safety actuation system (actuator associated with its electrical and driving part) Note 1 to entry: Engineered safety features need energy to operate (valves, motors, etc.). Generally, they are compared with reactor trip breakers which do not need energy to operate. 3.7 failure loss of the ability of a structure, system or component to function within acceptance criteria Note 1 to entry: The structure, system or component is considered to fail when it becomes incapable of functioning, whether or not this is needed at that time. A failure in, for example, a backup system may not be manifest until the system is called upon to function, either during testing or on failure of the system it is backing up.