IEC 61226 pdf download

IEC 61226 pdf download Nuclear power plants — Instrumentation and control systems important to safety — Classification of instrumentation and control functions
1 scope
This International Standard establishes a method of classification of the information andcommand functions for nuclear power plants，and the l&C systems and equipment thatprovide those functions，into categories that designate the importance to safety of thefunction.The resulting classification then determines relevant design criteria.
The design criteria are the measures of quality by which the adequacy of each function inrelation to its importance to plant safety is ensured. ln this standard, the criteria are those offunctionality, reliability, performance, environmental durability (including seismic) and QA.
This standard is applicable to all the information and command functions and the instrument-ation and control (1&C) systems and equipment that provide those functions. The functions,systems and equipment under consideration provide automated protection，closed or openloop control and information to the operating staff.They keep the NPP conditions inside thesafe operating envelope and provide automatic actions，or enable manual actions，thatprevent or mitigate accidents, or that prevent or minimize radioactive releases to the site orwider environment. The l&C functions that fulfil these roles safeguard the health and safety ofthe NPP operators and the public.
This standard follows the general principles given in IAEA safety code NS-R-1 and safetyguide NS-G-1.3， and it defines a structured method of applying the guidance contained inthose codes and standards to the l&C systems that perform functions important to safety in anNPP.This standard should be read in association with the IAEA guides and lEC 61513 inimplementing the requirements of lEC61508.
2Normative references
The following referenced documents are indispensable for the application of this document.For dated references, only the edition cited applies.For undated references, the latest editionof the referenced document (including any amendments) applies.
IEC 60709，Nuclear Power Plants – Instrumentation and Control systems important to safety -Separation
IEC 60780,Nuclear power plants – Electrical equipment of the safety system -QualificationIEC 60812,Analysis techniques for system reliability – Procedure for failure mode and effectsanalysis (FMEA)
3 Terms and definitions For the purposes of this document, the following definitions – given in alphabetical order – apply. They are consistent, or where it was possible, identical with those used in other current IEC or IAEA codes, guides and standards.
3.1 anticipated operational occurrences
all operational processes deviating from normal operation which are expected to occur once or several times during the operating life of the plant and which, in view of appropriate design provisions, do not cause any significant damage to items important to safety or lead to accident conditions