Overall Instrumentation and Control Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 282

In this cabinet, the SPDS can be used to analyze
and diagnose causes of the onset of disturbances
in unit operation and to identify corrective actions.
Description of SPDS will be given in Chapter 11.
In-core reactor monitoring system (IRMS)
monitors neutron and thermo-hydraulic param-
eters of the reactor core and the primary circuit;
controls distribution of neutron flux density across
the section and along the height of the core and
predicts their changes; generates signals, which
warn operational personnel about violations of
specified operational limits and initiate actuation
of preventive protection of the reactor facility in
case of such violations; archives and displays
monitoring results.
In IRMS two hierarchical levels are provided.
The lower level contains sensors of pressure,
flow rate, temperature, measuring channels of
the neutron flux density located inside the reactor
and means of collection, transformation of sensors
signals and preliminary data processing; the up-
per hierarchical level is formed by dual-computer
system. Information required for calculations is
input in IRMS from adjacent I&C systems, in-
cluded in the the reactor control and protection
system (shown in Figure 7): information on the
neutron flux density (reactor neutron power) - in
the form of continuous signals from second and
third set Neutron flux monitoring system (NFMS),
information on the position of control rods - in the
form of continuous signals from Rod group and
individual control system (RG&ICS), information
on preliminary protection - in the form of discrete
signals from the emergency and preventive reac-
tor protection system (E&PRPS). In turn, IRMS
outputs discrete signals of violations of specified
operational limits for local energy release, depar-
ture from nucleate boiling on the surface of fuel
elements and coolant temperature at the output
of fuel assemblies in E&PRPS.
Engineered safety features actuation systems
(ESFAS) are intended to initiate actions of tech-
nological systems and power unit equipment,
ensure their monitoring and control during execu-

tion of specified functions in any operation modes
on the reactor facility (including design basis and
beyond design basis accidents). Systems of
planned and emergency cooling, emergency sup-
ply of feedwater into steam generators, make-up-
blowdown of the primary circuit, drain water
collection, sprinkling system, etc. relate to such
technological systems.
In the overall I&C system of power unit with
WWER-1000 reactor, three ESFAS are provided,
where functions of technological protection, be-
ing the most important for safety, are executed
independently in each of such a system and less
important are distributed among them.
Each ESFAS contains:

• Technological parameter sensors and nor-
malizing transducers.
• Three independent channels, in each of
them monitoring of controlled parameters
is performed and technological protection
and interlocking signals are generated.
• Means of automatic water level control in
steam generators, discharge pressure of an
emergency feedwater pump, pressure in a
fast acting steam dump system, etc.
• Devices of remote control of actuators and
technological equipment of the power unit.
• Keys of mode selection and speciication
of remote control commands, set in MCR
and ECR.

According to the initial design, ESFASs were
assembled on the basis of a specifically developed
equipment family - a universal hardware complex,
in which computers were not used: all safety
important control functions were implemented
by hardware and informational ones, connected
with technological protection, interlocking and
remote control, were transferred for execution in
CIS. In the process of modernization, earlier used
equipment is substituted by software-hardware
complexes (SHC ESFAS), implemented on the
basis of RADIY PLATFORM or MSKU (see