Properties of Safety Important I&C Systems and their Components - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 110

nical state of the I&C system, SHC or peripheral
equipment and provides technical diagnostics with
a regulated integrity, depth, reliability, efficiency
and periodicity.
Software performs diagnostics of its software
(“self-control”), for example, using methods of a
repeat count and comparison of results, detection
of prohibited situations, assessment of duration
of execution of programs, procedures, etc. Soft-
ware provides automatic registration, storage
and display of data of results of diagnostics and
self-control. Recoding of programs of self-control
diagnostics do not influence execution of main
functions of software and does not cause degra-
dation of their properties. Failures (errors during
execution) of diagnostic and self-control programs
do not affect execution of main functions of the
I&C system, SHC or peripheral equipment.
Service software provides automation of pe-
riodic monitoring of the I&C system, SHC and
peripheral equipment during maintenance and
periodic checks (testing).
Protection Against Failures, Corruptions,
Unforeseen Actions: Based on results of techni-
cal diagnostics and provides reconfiguration of
structures of the I&C system (SHC) and com-
putation process recovery. Software executes
automatic checking of input information, warning
of personnel in case of unreliability detection and
protection from hazardous effects, which could be
caused by data corruption. In software protection
against computer viruses is [provided. As general
methods of protection, for example, the following
are applied:

• Creation of a safety and isolated operation-
al environment.
• Detection of informational iles in a pur-
chased software, a read-only memory of
purchased component parts and complex
electronic components.

• Software safety recovery.

Detailed information on software in safety im-
portant NPP I&C systems is described in Chapter 5.

Solutions and Recommendations

The compliance of discussed in this chapter the
properties of I&C systems and their components
(software-hardware complexes and peripheral
equipment) to the requirements of national and
international regulations, rules and standards is
a necessary, but not sufficient condition for func-
tional safety these systems assessment. To ensure
the functional safety it have to be complemented
the second condition - the fulfillment of order
of I&C systems design, manufacturing, testing,
inspection and maintenance, as well as the same
to hardware- software complexes and peripheral
equipment for these systems. This condition is
mentioned, but wasn't detailed in this chapter and
requires the separate consideration.
Particularly, recommend to include the require-
ments to these processes at all stages of the life
cycle of I&C systems and their components to new
Ukrainian regulations on I&C functional safety.

FUTURE RESEARCH DIRECTIONS

• Control of integrity of system areas,

launched application programs and used
data.

Directions of work on further improvement of
properties of safety important I&C systems and
their components: • Control of events, critical for a safety

system.

• Prevention of a negative result in case of a

random launch of actions not speciied by
speciications.

1. Extension of a set of requirements for proper-
ties of I&C systems and their components,
which should be regulated by norms, rules
and standards of nuclear and radiation safety