Overall Instrumentation and Control Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 295

actions not only on devices but also on their
fastening to the building constructions, and
also on external electric and optical cables
in the places of their joining to the device.
2. Not less actual task is assess risk of mistakes
of I&C systems and their components, which
detect internal and external hazards that
could lead to extreme influences to NPP
equipment and initiate actuation of systems
for prevention and minimization of these
influences. Example of these components
are seismic sensors, which detect exceeding
of regulated accelerating level and generate
signal for actuation of emergency and pre-
ventive reactor protection system, refueling
machine control system, etc. The subject
of special study is standardization of accu-
racy characteristics of seismic sensors and
methods of their testing for different forms
of seismic acceleration spectra.
3. Dangerous internal events also include igni-
tion in NPP areas, especially in the rooms
where safety systems equipment is located.
One of directions of fire safety improvement
is equipment of NPPs with not only informa-
tion systems of fire alrm, but control systems
of automatic firefighting. These systems have
to satisfy requirements on functional safety
as the other I&C systems of safety class
2(A) and special safety regulation (NAPB,
2002). Example of these systems designed
by Ukrainian companies is complex for fire
alarm and control of automatic firefighting
SPS1 (Bachmatch, 2008).

5. Requirements on resistance to temperature
influence (see Chapter 3) were formed to
prevent violation of operation conditions
in the rooms, where operating stand-alone
devices are located, and determine time of
maximum duration of this influence. This
time depend from reason of violation (e.g.
LOCA, failure of ventilation, failure of air
condition, etc.). Experience shown that time
to violation liquidation and restore of opera-
tion conditions not exceed time mentioned in
Chapter 3. But it is true only in the case when
violation cause by one independent event. If
violation is a consequence of the other event
(e.g. earthquake), more time is needed for
restoration of operation conditions. During
this time I&C safety systems have to fulfill
their functions in high temperature condi-
tions. This take place for another external
influencing factors (EIF). No limitation of
duration of safety equipment operation at
extreme value of temperature (and other
EIF) have to be considered.
6. The Fukushima-1 accident showed the need
to create post-accident monitoring systems
at every NPP, as one of immediate tasks.
The post-accident monitoring system (see
Chapter 3) should support NPP personnel
and safety experts in the control of accidents,
mitigation of their consequences, return of
the reactor facility to controllable state and
subsequent analysis of the causes and pro-
gression of design basis and beyond design
basis accidents.

4. In addition, it is necessary to reassess com-

ponents of other I&C systems important
to safety in accordance to fire-prevention
standards NAPB, 2002. Important task is
also estimation of resistance of operating
safety class 2(А) stand - alone devices to
influence of extinguishing agent, filling a
room after actuation of an automatic fire
fighting system.

The post-accident monitoring system should
provide acquisition, archiving, saving, displaying
and registration of the following information:

• About character and time of the beginning
of initiating events, passing out of opera-
tional limits and conditions, incidents and
accidents.