Environmental Engineering Reference
In-Depth Information
systems use high-speed digital devices, com-
munication networks, chips with high and extra
high-scale integration (microprocessors, memory
devices, programmable integrated logic circuits
etc.) essentially sensitive to electromagnetic distur-
bances and power supply quality. Unexpected per-
formance loss of individual components, caused
by the interference or deviation of power supply
parameters, can lead to unpredictable behavior of
the whole system. IEC standards of 61000-4 series
have considerably extended previous IEC ones.
Standards of technical committee IEC TC
56 “Dependability” have a great importance for
NPP I&C. Dependability covers the availability
performance and its influencing factors: reliability
performance, maintainability performance and
maintenance support performance (including man-
agement of obsolescence). The standards cover
generic aspects on reliability and maintainability
management, testing and analytical techniques,
software and system dependability, life cycle
costing, technical risk analysis and project risk
management.
Let us also mention a standard issued by TC
75 on “Classification on environment conditions.”
sented, on the right - IEC documents. The first level
is general safety in different branches of industry,
covered by IEC 61508, and IAEA documents are
naturally not included. The second level is general
NPP safety issues, covered by IAEA SSR-2/1, and
IEC standards are not included. The third level is
NPP I&C requirements and includes IAEA NS-G-
1.3, subjected to IAEA NS-R-1 and corresponding
to IEC 61513 and IEC 61226. The fourth level is
I&C systems components. It includes IAEA NS-
G-1.1 on NPP I&C software and IEC documents
(e.g., IEC 60880 (IEC,2006) on software or IEC
60987 (IEC,2007,c). on computers.
At the regional level, the IEC works to achieve
harmonization of standards among regional stan-
dardization organizations. A considerable part of
European standards, developed by European
Committee of Electrotechnical Standardization
- CENELEC, is identical to IEC standards or
slightly differs. So, all 7 parts of IEC 61508 are
ratified by CENELEC, and this standard is pub-
lished under EN 61508.
A number of IEC standards devoted to soft-
ware (IEC, 2006, IEC, 2004,b), to hardware
(IEC,2007,c), to classification of functions
(IEC,2009,b), to control rooms (IEC,2009,a), to
separation (IEC2004,a), to coping with common
cause failures (IEC,2007,b), to data communica-
tion (IEC,2009,c), etc have been published as EN
standards and implemented as nationally in 31
European countries.
IEC is closely connected with the Interna-
tional Organization for Standardization - ISO.
In particular, taking into account rapid growth
of computerization, in 1986 IEC and ISO cre-
ated a joint technical committee (ISO/IEC Joint
Technical Committee for Information Technology
- JTC1). This committee consists of subcommit-
tees. Standards applied in the field of NPP I&C
are developed by subcommittee 7 on software
engineering (JTC1/SC7 Software Engineering).
A necessity of analysis of this group of standards
is caused by a wide use of the latest achievements
of information technologies in the I&C systems.
Interconnection between
IEC Standards and Other
International Standards
IEC and IAEA closely interact with each other
in the context of NPP I&C systems, though, their
functions differentiate. According to a formal
cooperation agreement between IAEA and ТC
45 IEC, concluded in 1981, IAEA is responsible
for development of general concepts for NPP I&C
safety, TC-45 IEC is responsible for development
of technical requirements, using and detailing
the safety concepts mentioned above. Terms and
definitions, used in IEC standards, correspond to
IAEA standards.
Interconnection between documents of IEC and
IAEA is shown in Figure 5 that has a following
structure. On the left IAEA documents are repre-
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