General Provisions - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 10

providing automatic reactivity control of nuclear
fuel fission processes, safety parameters display
system are also related to normal operation sys-
tems.
Other examples of functions what I&C normal
operation systems perform are:

removal from the core and cooling pool prevention
or limitation of discharged radioactive substances
over the specified boundaries. Operation of safety
systems is required in cases, when normal operation
systems are not able to keep controlled parameters
in design specific operating limits, for example,
due to failure, personnel fault or quick and reliable
response to deviation of operating limits or safety
operation conditions, to prevent development of
the emergency into an accident.
Provided there are no violations, the I&C
safety systems perform information functions of
monitoring, archiving and display of values of
controlled parameters, diagnoses its own technical
state and alerts personnel about operation failures,
which can cause system unavailability to initiate
the required safety functions.
The I&C safety systems are involved when
specific initiating events, violations of any safety
operation conditions occurs, any of the controlled
parameters or specified combination of controlled
parameters (emergency set-points) exceed design
specific limit, and / or on command is obtained
from other I&C safety system or from operating
personnel.
The I&C safety system that has identified any
of the listed causes:

• Automatic monitoring of constructions
and equipment state and control of techno-
logical processes (automatic level regula-
tion in the pressurizer; protection against
unallowable increase of pressure in the irst
circuit; monitoring of coolant level in the
reactor vessel, coolant leak detection, iden-
tiication of leak location and assessment
of coolant low due to leak; monitoring of
activity and content of isotope-neutron ab-
sorbers in primary coolant, etc.)
• Automatic detection and limitation of ef-
fects of internal or external hazards con-
sidered in the design (ire, earthquake,
radioactivity release, violation of terms of
safety storage of nuclear fuel and radioac-
tive wastes, etc.)
• Automated control of refueling, displaying
data on position, transfer and direction of
fuel Assemblies and grabs; monitoring of
neutron lux density and concentration of
liquid neutron absorber solution; protection
against damage, deformation, destruction,
or fall of fuel assemblies in the process of
their retrieval, relocation, and installation;
mechanical interlocking on the margin of
permissible relocation or detection of a
fuel assembly in non-design position, in
case of power loss or occurrence of design
speciic initiating event.

• Alarms operating personnel and displays
the cause that initiated the safety function.
• Generates and outputs command or a se-
quence of commands of design speciic
protective actions, to executive I&C sys-
tems or executive elements (starting devic-
es) of technological safety systems.
• Prohibits executions of commands that
could be outputted by other I&C safety
systems, I&C normal operation systems
and / or operating personnel, provided that
they are not compatible with executed pro-
tective actions.
• Displays data required for operating per-
sonnel for monitoring of safety system

I&C safety systems together with technological
systems and equipment perform safety functions,
in accordance with standard IEC, 2011 or Ukraini-
an regulation NP, 2008, such as emergency reactor
shutdown, emergency heat removal, residual heat