IEC 60987-2021 Nuclear power plants – Instrumentation and control important to safety – Hardware requirements.
3.1 9 qualification
process of determining whether a system or component is suitable for operational use. The qualification is performed in the context of a specific class of the I&C system and a specific set of qualification requirements
Note 1 to entry: The qualification requirements are derived from the specific class of the I&C system and a specific application context.
Note 2 to entry: I&C systems are typically implemented on the basis of interacting sets of equipment. Such equipment may be developed as part of the project, or it may be pre-existing equipment. Typically, qualification of an “I&C system” is accomplished in stages: first by the qualification of individual pre-existing equipment (usually early in the system realization process); in a second step by the qualification of the integrated I&C system (i.e. the final realized design).
Note 3 to entry: Qualification of I&C systems is always a plant- and application-specific activity. However, it may rely to a large degree on qualification activities performed outside the framework of a specific plant design (these are called “generic qualification” or “pre-qualification”). Pre-qualification may reduce the plant-specific qualification effort significantly, however, the application-specific qualification requirements need to be demonstrated.
[SOURCE: IEC 61 51 3:201 1 , 3.38, modified – embedded definition of Pre-existing equipment has been removed in Note 2 to entry and last sentence of Note 3 corrected.]
3.20 random fault
non-systematic fault of hardware components
Note 1 to entry: Faults of hardware components are a consequence of physical or chemical effects, which can occur at any time. A good description of the probability of the occurrence of random faults can be given using statistics (fault rate). Increased fault rates can be the consequence of systematic faults in hardware design or manufacture, if these occur without temporal correlation, for example as a consequence of premature ageing.
[SOURCE: IEC 62340:2007, 3.1 5]
3.21 safety function
specific purpose that must be accomplished for safety for a facility or activity to prevent or tomitigate radiological consequences of normal operation, anticipated operational occurrences and accident conditions
Note 1 to entry: Safety functions are required to fulfil the fundamental safety functions that are (i) control of reactivity, (ii) removal of heat from the reactor and from the fuel store, (iii) confinement of radioactive material,shielding against radiation and control of planned radioactive releases, as well as limitation of accidental radioactive releases [IAEA SSR-2/1 , Requirement 4].
Note 2 to entry: Safety functions are primarily those that are credited in the safety analysis and include functions performed at all levels of defence in depth.
[SOURCE: IAEA Safety Glossary, 201 8]
3.22 system
set of components which interact according to a design, where an element of a system can beanother system, called a subsystem
Note 1 to entry: See also “I&C system”.
Note 2 to entry: I&C systems are distinguished from mechanical systems and electrical systems of the NPP.
Note 3 to entry: This IEC SC 45A definition is totally compatible with the sub-definition of “system” given in the frame of the 201 8 edition of the IAEA Safety Glossary definition of “Structures Systems and Components (SCC)”.
[SOURCE: IEC 61 51 3:201 1 , 3.56, modified – In Note 3 to entry, edition 2007 of IAEA Safety Glossary definition has been updated to edition 201 8.]IEC 60987 pdf download.