International Standard Bases and Safety Classification

International Standard Bases and Safety Classification

Michael Yastrebenetsky (State Scientific and Technical Centre for Nuclear and Radiation Safety, Ukraine) and Grygoriy Gromov (State Scientific and Technical Centre for Nuclear and Radiation Safety, Ukraine)
DOI: 10.4018/978-1-4666-5133-3.ch002
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Abstract

The main standard bases for NPP I&C systems are documents of the International Atomic Energy Agency (IAEA) and International Electrotechnical Commission (IEC). Standards are interconnected through the following: IAEA develops general safety principles for NPP I&C systems, and IEC develops technical requirements that use and specify safety principles. Structures of the bases are considered. Classifications of I&C systems and their components are given on the basis of their safety impact. According to the IAEA classification, all systems are divided into safety important and non-safety important. According to IEC, functions to be performed by I&C systems shall be assigned to categories according to their importance to safety. The importance to safety of a function shall be identified by means of the consequences in the event of its failure, when it is required to be performed, and by the consequences in the event of a spurious actuation. All functions are divided into categories A, B, C.
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Background

Elaboration of international standards related to NPP I&C began immediately after commissioning of the first NPP. The International Electrotechnical Commission (IEC) created a separate technical committee devoted to NPP I&C, with name “Nuclear Instrumentation” in 1960. One of the first IEC publications-”General principles of nuclear reactor instrumentation” was issued in 1967. IEC understood importance of computer technique for NPP automatics: publication “Application of digital computer to nuclear reactor instrumentation and control “dates back to 1979.Computers only began to make first steps for their using at NPP at that time.

During more than 50 years IEC developed a lot of standards applicable to different types of I&C, to different aspects of NPP I&C design and operation. Special attention is paid to application of computer systems and the latest achievement in information technology.

The International Atomic Energy Agency (IAEA) elaborated Codes on safety of NPPs, which related to all NPP systems, including I&C (e.g., “50-C-D. Code on Safety on Nuclear Power Plants. Design” -1979). Special safety guides related exclusively to NPP I&C (“50-SG-D3. Protection Systems and Related Features in Nuclear Power Plants”- 1980). IEC and IAEA have close connections in the development of standard base for NPP I&C.

Many countries where NPPs are operated developed their national standard base related to I&C. One of the first American National Standards (based on IEEE Standard 323-1974) was ANSI/IEEE Std.323-1983 “IEEE Standard for Qualifying Class1 Equipment for Nuclear Power Generating Stations” which did not lose its importance for long time. The first USSR Regulation PBYa- 04-74 “Rules of NPP Nuclear Safety” which contained requirements on reactor control and protection systems, was issued in 1974.

Ukraine after gaining independence (1991) used to 1999 USSR regulations and standards related to NPP I&C. Ukrainian regulation “NP 306.5.02/3.035-2000. Requirements for nuclear and radiation safety information and control systems important to safety of nuclear power plants” was issued in 2000.

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