BS EN 61226:2010 Nuclear power plants. Instrumentation and control important to safety. Classification of instrumentation and control functions
BS EN 61226 is an International Standard which establishes a method of classification of the information and command functions for nuclear power plants, and the I&C systems and equipment that provide those functions, into categories that designate the importance to safety of the function. The resulting classification then determines relevant design criteria.
The design criteria are the measures of quality by which the adequacy of each function in relation to its importance to plant safety is ensured. In this standard, the criteria are those of functionality, reliability, performance, environmental durability (including seismic) and quality assurance (QA).
BS EN 61226 is applicable to all the information and command functions and the instrumentation and control (I&C) systems and equipment that provide those functions. The functions, systems and equipment under consideration provide automated protection, closed or open loop control and information to the operating staff. They keep the NPP conditions inside the safe operating envelope and provide automatic actions, or enable manual actions, that prevent or mitigate accidents, or that prevent or minimize radioactive releases to the site or wider environment. The I&C functions that fulfil these roles safeguard the health and safety of the NPP operators and the public.
BS EN 61226 follows the general principles given in IAEA safety code NS-R-1 and safety guide NS-G-1.3, and it defines a structured method of applying the guidance contained in those codes and standards to the I&C systems that perform functions important to safety in a NPP. This standard should be read in association with the IAEA guides and IEC 61513 in implementing the requirements of IEC 61508 series.
Contents of BS EN 61226:
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Abbreviations
5 Classification scheme
5.1 General
5.2 Background
5.3 Description of categories
5.3.1 General
5.3.2 Category A
5.3.3 Category B
5.3.4 Category C
5.4 Assignment criteria
5.4.1 General
5.4.2 Category A
5.4.3 Category B
5.4.4 Category C
6 Classification procedure
6.1 General
6.2 Identification of design basis
6.3 Identification and classification of functions
7 Assignment of technical requirements to categories
7.1 General requirements
7.2 Requirements related to functions
7.2.1 Basic requirements
7.2.2 Specific requirements
7.3 Requirements related to I&C systems
7.3.1 Basic requirements
7.3.2 Specific requirements
7.4 Requirements related to equipment
7.4.1 Basic requirements
7.4.2 Specific requirements
7.5 Requirements related to quality aspects
7.5.1 Basic requirements
7.5.2 Specific requirements
Annex A (informative) Examples of categories
Bibliography
Figure 1 – Method of classification
Table 1 – Tabular correlation between categories and other IEC standards
