Overall Instrumentation and Control Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 289

and indicating a cause, what initiated the
emergency or the preventive protection;
manual control means (keys for initiation
of commands of emergency or preventive
protection and conirmation of messages).
• Key (placed in ERC) for manual initiation
of emergency protection commands.

• Discrete signals from a electric supply sys-
tem (lack of supply voltage on feeders).

• Commands from control keys in MCR and

ECR.

In addition, at the input of each SHC channel,
a discrete signal is supplied during deactivation
of another SHC, for example, for checking or
maintenance.
The channel that has detected a deviation of
at least one monitored (measured or calculated)
parameter over the set-point limit of emergency
protection actuation, or identified a failure of any
of specified safe operation conditions, or received
from proper channel 1 NFMS (2 NFMS) a signal
Рw ≥ ERP”Рw,” Т ≤ ERP”Т” or an operator's
command (from a key “ERP,” placed in MCR or
ECR), forms a discrete signal that is transmitted
to the cross output cabinet. On the basis of these
signals, obtained from, at least, two or three chan-
nels, cross output cabinet generates (according to
an accepted logical condition “two-out-of-three”)
and outputs an emergency protection command
(ERP).

• Cables for connections.

E&PRPS has three independent interredundant
channels. Each channel has a full set of required
sensors, independent from sensors of other chan-
nels, and performs all main functions of emergency
and preventive protection. The central part of each
channel - signal forming (SF) device - implemented
in a separate cabinet and supplied by built-in panel
computer for set-points input and adjustment.
The following is common for three SF devices
(channels): cross output cabinet (not shown in
Figure 8); elements (keys) of manual control and
visual alarms, placed in MCR and ECR; worksta-
tion (WS) of data archiving and display, and laser
printer, located in a room of a shift personnel that
monitors a state and provides maintenance and
recover of reactor control and protection system
(LOC); automated work places of technologist and
operator (not shown in Figure 7 and 8).
Each channel receives:

• At the output of three channels of the ac-
tuation system (RG&ICS): Initiates reac-
tor emergency shutdown due to the main
and standby power from all control rods,
causing their drop in the reactor core.
• At the irst and second output of a pow-
er supply system of control rod drives:
Initiates emergency shutdown due to deen-
ergization of alternate current on both in-
puts of power supply to all control rods.
• At the outputs of three channels of a tur-
bine control system (TCS): Initiates ac-
tions, leading to turbine unloading in case
of reactor emergency shutdown.
• At the input of the boron regulation sys-
tem (BRS): Initiates connection of high-
pressure boron injection pump.

• Analog and discrete signals from sensors S
of this channel.
• Discrete signals Рw ≥ ERP “Рw,” Т ≤ ERP
“Т,” Рw ≥ PRP1 “Рw,” Т ≤ PRP1 “Т,” Рw
≥ PRP2 “Рw,” Т ≤ PRP2 “Т” from a prop-
er channel 1 NFMS (2 NFMS).
• Discrete signals from IRMS (violations
of speciied operational limits of local en-
ergy release, departure from nucleate boil-
ing on the surface of fuel elements and
coolant temperature at the output of fuel
assemblies).