Abstract
Safety analysis uses probability combinatorial models like fault tree and/or event tree. Such methods have static basic events and do not consider complex scenarios of dynamic reliability, leading to conservative results. Reliability, availability, and maintainability (RAM) analysis using reliability block diagram (RBD) experience the same limitations. Continuous Markov chains model dynamic reliability scenarios but suffer from other limitations like states explosion and restriction of exponential life distribution only. Markov Regenerative Stochastic Petri Nets oblige complex mathematical formalism and still subject to state explosions for large systems. In the design of complex systems, distinct teams make safety and RAM analyses, each one adopting tools better fitting their own needs. Teams using different tools turns obscure the detection of problems and their correction is even harder. This work aims to improve design quality, reduce design conservatism, and ensure consistency by proposing a single and powerful tool to perform any probabilistic analysis. The suggested tool is the Stochastic Colored class of Petri Nets, which supplies hierarchical organization, a set of options for life distributions, dynamic reliability scenarios and simple and easy construction for large systems. This work also proposes more quality rules to assure model consistency. Such method for probabilistic analysis may have the effect of shifting systems design from “redundancy, segregation and independency” approach to “maintainability, maintenance and contingency procedures” approach. By modeling complex human and automated interventional scenarios, this method reduces capital costs and keeps safety and availability of systems.
Highlights
As shipping has a contribution to greenhouse gases emission [1], future regulations may create more taxes on crude oil, rising transport tariffs
For Mobile Nuclear Power Plants (MNPP), due to their mobile nature, there is no grid power, so they need to rely on the own power for operation and safety
After losing completely the electrical power, the nuclear power plant (NPP) blackout scenario starts at once, but only after a given time, damage starts as the primary circuit has thermal inertia
Summary
As shipping has a contribution to greenhouse gases emission [1], future regulations may create more taxes on crude oil, rising transport tariffs. For Mobile Nuclear Power Plants (MNPP), due to their mobile nature, there is no grid power, so they need to rely on the own power for operation and safety. To meet current core damage frequencies, the probability of long-term station blackout must be lower than 10-5 reactor-year. Adopting probabilistic analysis methods like fault and event trees, a MNPP would need to have large redundancy on diesel generators. The same order of long-term station blackout probability can be obtained, with less diesel generators, by the adoption of more realistic scenarios like passive redundancy, replacement of spares, permissibility of short deterministic outage periods before core heat up, etc. Given most part of these scenarios is proven to be realistic, the current methods of probability analysis as fault trees are too conservative
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