Tokarev V. Models and a method of reliability assurance of Nuclear Power Plants Instrumentation and Control System under multiversion technologies using

The dissertation is devoted to development of the reliability models, methods of reliability ensuring and fault tolerant structures choice of Nuclear Power Plants (NPP) Instrumentation and Control Systems (I&C) important for safety. Scientific results are: 1) a new reliability models of the multiversion I&C structures which take into account failures and faults of different versions caused by relative, group and absolute defects and permit to obtain probabilities of different safety states; 2) an improved reliability models of the one-version I&C structures that describe possible system states with regard to different quantity and types of hardware and software failures and faults and permit to receive analytical equations for calculation of the reliability and availability measures of unrecovered and recovered systems; 3) an improved method of assessment and choice the variants of I&C structures which bases on complex approach to tasks of analysis, synthesis and verification of structures and permitsto ground of multivesion technology of a system development. The obtained results have applied for software-hardware complex of emergency and preventive protection of nuclear reactors VVER-1000 which are used on Ukrainian NPPs. It permits to ground system-technical decisions and ensure requirements fulfilment for diversity principle.