Overall Instrumentation and Control Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 288

Emergency protection set-points are assigned
by power (ERP “Рw”) and period (ERP “Т”) and
preventive protection set-points by power (PRP1
“Pw,” PRP2 “Pw”) and period (PRP1 “Т,” PRP2
“Т”), separately for monitoring during reloading,
startup, and operational subrange, and also upper
limit of reactor power automatic regulation (ULAR
“Pw”), that corresponds to 102% of reactor rela-
tive neutron power.
If relative neutron power or a period exceed
specified for them limit values (i.e. during fulfill-
ment of any of conditions Рw ≥ ERP “Рw,” Т
≤ ERP “Т,” Рw ≥ PRP1 “Рw,” Т ≤ PRP1 “Т,”
Рw ≥ PRP2 “Рw,” Т ≤ PRP2 “Т”), relevant output
of devices for data collection and processing (chan-
nel output) generates discrete signals, transmitted
to inputs of emergency and preventive reactor
protection system (E&PRPS). Analog signals,
defining the value of relative neutron power Рw,
are transmitted from inputs of each channel of the
first and second NFMS to inputs of reactor power
control, unloading, limitation and accelerated pre-
ventive protection system (RPW CUL & APPS).
In the same system, discrete signals generated
in channels 1 NFMS and 2 NFMS are transferred
when relative neutron power exceeds 25% and 75%
of the nominal value (Рw ≥ 25%; Рw ≥ 75%) and
when reactor relative neutron power achieves the
upper limit of reactor power automatic regulation
(Рw ≥ ULAR “Рw”).
In NFMS output signals are also generated:

• For RMCS - discrete signals, warning of

exceeding values of relative power or pe-
riod speciied as set-points of preventive
or emergency protection for a nuclear fuel:
STOP (if Рw ≥ PRP1 “Рw” or Т ≤ PRP1
“Т”) and REVERS (if Р ≥ ERP “Р” or Т ≤
ERP “Т”).

Current values of relative power and period cal-
culated in each channel and also averaged among
three channels are displayed on digital indicators
and built-in panel computer screen (in the form
of digitized diagrams and histograms). Besides
them, lower and upper limits of neutron power
in each subrange are displayed on built-in panel
computers screen, a current subrange is initiated,
signals on achievement of each of the specified
set-points of power and period are generated.
The data display device receives information
from DC&P 1, 2 and 3, saves it in an archive (in
a hard disk), creates (edits) archival file footages,
and provides their review and duplication on ex-
ternal media. Possibility of data output in Ethernet
network for transmission of digital messages in
IRMS and CIS is provided.

Emergency and Preventive
Protection

Functions of emergency and preventive protection
are performed by two independent emergency and
preventive reactor protection systems (E&PRPS).
Each system contains: • For IRMS and CIS - analog signals, repre-

senting speciied (limit) and current (aver-
aged by three channels) values of relative
power and a period, and discrete signals,
deining a measuring at the moment neu-
tron lux subrange (corresponding to
nuclear fuel reloading, reactor start and
power operation) and a result of checking
(diagnostic) of NFMS.

• Software-hardware complex (SHC).

• Sensors of temperature, pressure, level,

pressure drop, frequency, electric power,
technological equipment state.

• Peripheral devices (placed in MRC): warn-

ing means (visual alarms) for the relection
of the SHC state (faults, disconnections)