Properties of Safety Important I&C Systems and their Components - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 109

For devices with a consumption current not
more than 16 А (in a single phase), connected to
a common primary power network, disturbance
emission standards are specified (harmonic
components of consumed current and/or voltage
oscillations, caused by this current) in the primary
power network.

requirements for monitoring and alarm in case of
ignition detection in a device are mandatory, for
devices of other safety classes - recommended.
For prompt fire detection and making solu-
tions for its elimination, informational systems of
fire alarm and / or control systems of automatic
firefighting, related to 2(A) safety class, should
be provided. Fire alarm and automatic firefight-
ing systems (Bachmatch, 2008) are developed,
designed and placed in such a way to guarantee
that their spurious actuation will not affect other
systems.

Fire Safety

Operating stand-alone component parts of SHC
and peripheral equipment meet requirements of
fire-prevention standard of NAPB, 2000. Fire
safety is provided under maximal permissible
long- and short-term increase of power supply
voltage, high voltage on inputs and outputs, short
circuits inside a devices and output circuits. Fire
prevention is provided:

SOFTWARE PROPERTIES

For software of the I&C system, SHC and intel-
lectual peripheral equipment requirement are
regulated: for functions, structure and elements;
for diagnostics and self-control; for protection
against failures, corruptions, unforeseen actions.
Similar requirements are provided for electronic
design of complex programmable components.
Functions, Structure and Elements: Software
provides performance of all functions, that should
be executed or using with a specified reliability
and quality of operation. Software of the I&C
system, SHC and peripheral equipment has a
module structure. Text of one module contains a
limited number of operators, has a clear structure,
can be easily modified and tested.
The software that is used as a component in
the I&C system, SHC and peripheral equipment
of 2(A) safety class, the use of operating sys-
tems is limited by only the simplest functions. In
software that is used as a component of the I&C
system, SHC and peripheral equipment of 3(B)
safety class, the use of interruptions is limited, in
case of performance of category A functions - is
prohibited. In software, participating in execution
of category B and C functions, operating system
and interruptions are used only in reasoned cases.
Diagnostics and Self-Control: Software per-
forms a continuous automatic monitoring of a tech-

• Use of ire-proof materials, coatings and
cables (noncombustible, hardly inlam-
mable, lame-retardant and nonsmoking
and without toxic discharges) that passed
speciic tests and were certiied according
to the established procedure.
• Use of component parts, in which igni-
tion sources do not occur during reloading,
short circuits or failures.
• Voltage limitations, which can occur in in-
put or output circuits in case of adjacent
equipment failures or as a result of person-
nel errors.
• Use of active facilities of control, or pro-
tective shutdown of ignition sources, or
automatic device de-energizing in case of
detection of ire hazards.

Probability of fire in any operating stand-alone
device is not more than10 -6 a year. For prompt
ignition detection inside a device, a continuous
automatic monitoring and a preventive alarm in
case of detection of hazards (temperature increase,
smoke in a case) are provided. For operating
stand-alone devices related to 2(A) safety class,