Properties of Safety Important I&C Systems and their Components - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 105

chive - not more than 2 seс from comple-
tion of directive input before occurrence of
proper information in a speciied format on
a display device.

and further power restoration of is determined in
the form of a maximal permissible upper value,
after its expiration an automatic recovery of ex-
ecution of specified functions, interrupted due to
power cut, is guaranteed. Execution of category A
functions in a full scope with standardized proper-
ties is automatically resumed not later than in 1
min after power restoration, execution of category
B and C functions - not later than in 5 min (or
a bigger time interval - on agreement between a
designer of the I&C system, the developer of SHC
and the operating organization or a customer).

Function execution speed (maximal permis-
sible number of functions, executed within a
time unit):

• Calculation of design parameters for pro-
tection functions - not less than 100 times
per second for each of parameters.
• Calculation of design parameters for func-
tions of restriction, regulation, interlocking
- not less than 10 times per second for each
of parameters.
• Comparison of values of controlled pa-
rameters with set-points of preventive and
emergency alarm - not less than 10 times
per second for each of parameters.
• Archiving of data about initiating events,
failures of design limits of safety opera-
tion, occurrence of conditions of genera-
tion protective action commands - not
less than 100 times per second, data of a
state of technological equipment, values
of controlled parameters and set-points,
violations of operational limits and condi-
tions, commands of restriction, regulation,
technological protection and interlocking,
discrete and remote control - not less than
10 values per second for each of type of
achieved data.
• Updating of video frame variable data, dis-
played in a monitor screen - not less than
once per second.

Human-Machine Interface

The I&C system and SHC, directly interacting
with a personnel of NPP, should support the
human-machine interface, whose properties al-
low minimizing personnel load and decreasing
the probability of human errors. From the I&C
system and SHC, human-machine interface is
supported for:

• Alarm facilities (visual and audible alarm),
multi-access information display (video
monitors, informational screens and mimic
panels), command input elements and op-
erator's guidelines placed in MCR, ECR
and local control panels.
• Automated workplaces of operational
personnel and/or workstations, placed in
MCR and ECR.
• Workstations of operational personnel,
placed in rooms of a shift engineer and/or
technical support center.
• Automated workplaces of personnel, man-
aging accidents, and safety experts, situ-
ated in emergency response centers. Time of information storage in a data base

(in operational memory of SHC) - not less than
24 hours, in an archive is usually within one fuel
campaign of the reactor facility.
Time actuation start of a peripheral equipment
and SHC after a short-term (not more than 10 min)
of an intentional or unintentional disconnection

• Elements of alarm, indication, display (vid-

eo monitors, panel computers) and manual
control elements, inbuilt into devices.

Human-machine interface facilities, placed in
MCR and ECR, are labeled and placed in such