Properties of Safety Important I&C Systems and their Components - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 67

manual ire detectors and issue of proper
control actions for warning devices and ac-
tuating elements of ventilation systems and
ireighting systems.

support of personnel; data output required for
execution of other functions.

System Point of View

Monitoring and control of refueling relate to
category A functions and provides:

This point of view considers the systems as an
organized set of equipment that implements mul-
tiple functions/subfunctions. This point of view
is typical for designers of overall I&C systems,
based on the analysis of functions specified by
processing engineers, selection of individual I&C
systems required for their implementation and
identification of functions, to be performed by
each of them (Figure 3). Upon that an individual
I&C system can participate in performance of
one or several different functions, including those
related to different categories.
Category of any function of I&C system is
determined according to the highest from the
categories of relevant functions, in which perfor-
mance it participates (one and the same function
in different I&C systems can relate to different
categories).
Safety I&C systems together with technological
systems and equipment perform functions required
for safety assurance during power unit operation
in all operation modes, violations of normal and
safety operation and post-accident mode, caused
by any design-basis accident.
According to IAEA 2002, a safety I&C systems
are divided into:

• Automatic control of refueling device ac-
cording to the program, schedule and car-
togram of refueling;
• Automatic measuring of neutron lux den-
sity and a concentration of luid neutron
absorber solution during refueling.
• Speed limit of transfer of fuel assembles on
the levels regulated in the design of refuel-
ing machine.
• Protection against damage, deformation,
destruction or fall of fuel rod arrays, and
also of stress application, exceeding maxi-
mal permissible, during their removing or
mounting.
• Mechanical locking of refueling device at
the limits of permissible transfers of fuel
assemblies, and also in case of detection of
the beyond design state, failures or dam-
ages of refueling device, power loss and
initiating events considered by the design.
• Immediate display of information of posi-
tion, transfer and orientation of fuel assem-
blies and pinchers.
• Monitoring using closed circuit television
system. • Protection systems control operation of

technological systems and equipment of
power unit and automatically initiate pro-
tective actions required to prevent exceed-
ing of design limits, deine dangerous or
potentially dangerous power unit state, or
limit efects of design-basis accidents.

Individual functions can be arbitrary divided
into parts (subfunctions), for example, for reactor
protection function (see Figure 2): monitoring of
technological parameters; monitoring of events
and states of equipment; initiation of protection
action; realization of control actions; information • Safety actuation systems control operation

of technological systems and equipment,