Reliability assessment of nuclear powered zero-liquid-discharge cogeneration systems with thermal energy storage

Nuclear power has the potential to simultaneously address demand for clean electricity, freshwater scarcity, and demand for valuable minerals, such as lithium, if it is thermally integrated with zero liquid discharge desalination (ZLD). ZLD is an energy-intensive process that desalinates seawater, mining its minerals and extracting freshwater such that no liquid is discharged. However, such nuclear-thermal integration could present challenges for the reliability of the combined system, given both nuclear and desalination are capital-intensive technologies. In this paper, the reliability of such a system is assessed for different maintenance strategies. Additionally, the impact of using thermal energy storage (TES) to decouple designs to maintain thermal independence and reduce downtime is investigated. The system is modeled in Event Modeling Risk Assessment using Linked Diagrams (EMRALD). We determined that performing preventative maintenance on degrading system components can reduce reactor downtime by as much as 40% and that introducing TES to decouple the power cycle from the ZLD reduces reactor downtime by as much as 65%. The impact of decoupling on reducing reactor downtime was found to depend on the component failure rates of the ZLD system, with such a strategy being less impactful for a higher reliability process heat application. High component reliabilities in the TES were found to be necessary to prevent increased downtime in the ZLD system, as failure in the TES could otherwise drive the ZLD system offline. Seeing these changes in system performance, this research shows how EMRALD can be used to compare the reliabilities of different cogenerating plant designs and maintenance strategies.