Formulation and Reliability Feature Analysis of Analog, Digital and Hybrid I&C Architectures for Research Reactors

Optimized design of Instrumentation and Control (I&C), having rationally good reliability features like high availability, low spurious trip rate and low cost, is very important for safety and economical use of nuclear reactors. The demand for optimization becomes more significant in case of small size educational or research reactor due to less margin of cost. The aim of study, in this article, is to develop analog, digital and hybrid architectures for reactor protection I&C system and identification of suitable one for research reactor. The reliability feature analysis of proposed architectures has been performed in three parts (i) analytical analysis for redundancy (ii) Bayesian network model for estimation channel failure λ_dc and (iii) unavailability or Probability of Failure on Demand (PFD) for each I&C system architecture. It is found here that 2oo3 (2 out of 3) architecture is highly suitable for research reactor as it has low nuisance process trip rate, rational availability (reasonable high) and low probable to CCF failure, if compared with other ones. Results have shown that hybrid configuration can perform better than analog, digital architectures. This research would be helpful for the designers to consider appropriate model with defined cost and availability for their design.