IEC 62340:2007
Nuclear power plants - Instrumentation and control systems important to safety - Requirements for coping with common cause failure (CCF)

Standard No.

IEC 62340:2007

Release Date

2007

Published By

International Electrotechnical Commission (IEC)

Latest

IEC 62340:2007

Replace

IEC 45A/668/FDIS:2007

Scope

I&C systems important to safety may be designed using conventional hard-wired equipment, computer-based equipment or by using a combination of both types of equipment. This International Standard provides requirements and recommendations1 for the overall architecture of I&C systems, which may contain either or both technologies. The scope of this standard is: a) to give requirements related to the avoidance of CCF of I&C systems that perform category A functions; b) to additionally require the implementation of independent I&C systems to overcome CCF, while the likelihood of CCF is reduced by strictly applying the overall safety principles of IEC SC 45A (notably IEC 61226, IEC 61513, IEC 60880 and IEC 60709); c) to give an overview of the complete scope of requirements relevant to CCF, but not to overlap with fields already addressed in other standards. These are referenced. This standard emphasises the need for the complete and precise specification of the safety functions, based on the analysis of design basis accidents and consideration of the main plant safety goals. This specification is the pre-requisite for generating a comprehensive set of detailed requirements for the design of I&C systems to overcome CCF. This standard provides principles and requirements to overcome CCF by means which ensure independence2: a) between I&C systems performing diverse safety functions within category A which contribute to the same safety target; b) between I&C systems performing different functions from different categories if e.g. a category B function is claimed as back-up of a category A function and; c) between redundant channels of the same I&C system. The implementation of these requirements leads to various types of defence against initiating CCF events. Means to achieve protection against CCF are discussed in this standard in relation to: a) susceptibility to internal plant hazards and external hazards; b) propagation of physical effects in the hardware (e.g. high voltages); and c) avoidance of specific faults and vulnerabilities within the I&C systems notably: 1) propagation of functional failure in I&C systems or between different I&C systems (e.g. by means of communication, fault or error on shared resources), 2) existence of common faults introduced during design or during system operation (e.g. maintenance induced faults), 3) insufficient system validation so that the system behaviour in response to input signal transients does not adequately correspond to the intended safety functions, 4) insufficient qualification of the required properties of hardware, insufficient verification of software components, or insufficient verification of compatibility between replaced and existing system components.

IEC 62340:2007 Referenced Document

• IEC 60671 Nuclear power plants - Instrumentation and control systems important to safety - Surveillance testing
• IEC 60709 Nuclear power plants - Instrumentation, control and electrical power systems important to safety - Separation*， 2018-04-18 Update
• IEC 60780 Nuclear power plants - Electrical equipment of the safety system - Qualification
• IEC 60880 Nuclear power plants - Instrumentation and control systems important to safety - Software aspects for computer-based systems performing category A functions
• IEC 60980 Recommended practices for seismic qualification of electrical equipment of the safety system for nuclear generating stations
• IEC 61000-4 Electromagnetic compatibility (EMC) - Part 4-9: Testing and measurement techniques - Impulse magnetic field immunity test*， 2016-07-13 Update
• IEC 61226 Nuclear power plants - Instrumentation, control and electrical power systems important to safety - Categorization of functions and classification of systems*， 2020-04-29 Update
• IEC 61513 Nuclear power plants - Instrumentation and control important to safety - General requirements for systems*， 2011-08-01 Update

IEC 62340:2007 history

• 2007 IEC 62340:2007 Nuclear power plants - Instrumentation and control systems important to safety - Requirements for coping with common cause failure (CCF)