Diversity and Multi-Version Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 228

Solution and Recommendations FUTURE RESEARCH DIRECTIONS

Described models of multi-version systems are a
base for the development of different architecture
variants. The proposed techniques of diversity
level and multi-version systems safety assessment
are founded on two interconnected approaches.
First of them is the metric-based technique al-
lowing to assess a diversity level and to compare
multi-version systems on application of different
kinds and different volume of diversity. Second
one is based on the probabilistic models, which
include β calculated using metric analysis.
Development and implementation of multi-
version FPGA-based systems is a new stage of
the evolution in area of improving safety of NPP
I&Cs. In this chapter we discussed basic concepts
of diversity as a key approach to decreasing a
probability of a common cause failure of safety-
critical I&Cs and the taxonomic scheme of multi-
version computing as a part of dependable, safe
and secure computing.
Known version redundancy classification
schemes were generalized in three-space matrix
(“cube of diversity”) taking into account features of
FPGA technology. This unique technology allows
to simplify NPP I&C development and verifica-
tion, realize multi-reconfiguration (dynamical
function- and dependability-oriented architecting,
multi-parametrical space-structural adaptation,
etc.), to propose decisions with different product-
process version redundancy.
Key challenges related to diversity-oriented
and FPGA-based systems are the following: ex-
isting standards are not enough detailed to make
all necessary decisions concerning diversity (all
the more FPGA-based decisions); multi-version
I&Cs are still unique, failures occurred rarely and
information about failures is not enough represen-
tative; methods of diversity assessment and kind
selection, as a rule, are based on expert approach.
FPGA technology allows developing multi-
version systems with different product-process
version redundancy, diversity scalable multi-
tolerant decisions for safety-critical NPP I&Cs.

Future R&D steps may be the following:

• Development of the detailed standards
and guides to assess and choice types and
capacity of diversity according to require-
ments and criteria of safety and cost.
• Research of diferent diversity types appli-
cation to decrease risks of CCF taking into
consideration dependencies of these types.
• Development of Safety Case-oriented tech-
niques and tools for diversity assessment.
• Research and development of diversity ap-
plication techniques for cyber security im-
provement taking into account features of
MP and FPGA technologies.
• Analysis of diversity approach for System-
on-Programmable Chip (Network-on-
Chip, System-in-Package) and research of
SoPC-based multi-version I&C systems.

CONCLUSION

Application of the diversity allows a decrease in
the probability of CCFs. A new graphical model
is presented in this chapter for different variants of
diversity and can be used during the development
of safety-critical systems and selection of optimal
algorithms for diversity types based on a criterion
of safety-reliability-cost. The model addresses
diversity types at different levels: complex elec-
tronic components (FPGA, etc.), printed circuit
boards, manufacturers, specification languages,
design and program languages, etc. It takes into
consideration the dependencies among diversity
types. The graphical model is developed using
the subgraph splitting algorithm, which has been
previously used for software test generation.
Key challenges related to MP- and FPGA-based
multi-version I&C systems concern uniqueness
of ones, specific risks of CCFs (including CCFs
for different versions of MVS) existing standards
(are not enough detailed), approved diversity-