Estimating fuel channel bore from fuel grab load trace data

Detailed measurements of the graphite core fuel channels are made by specialist inspection equipment during planned outages, typically every 18 months to 3 years. The bores of the graphite fuel bricks are obtained during these inspections and are used to provide important information about the health of the core. Additionally, less detailed online monitoring data is obtained much more frequently during refuelling events, called the fuel grab load trace (FGLT), which can be also used to infer the health of the graphite core. This paper describes the process of creating a model which isolates a component of the refuelling data and maps it directly to dimensional measurements of fuel channel bore. The model is created from a combination of the theoretical understanding of the physical interactions of the fuel stringer during refuelling events and several years of refuelling and inspection data to estimate suitable model parameters. Initially the model created was a coarse estimation of FGLT to fuel bore dimension but through refinements a much more accurate model has been created. An application of this model is shown through a case study of a recent outage where estimations were made on refuelling data and were compared to previously unseen inspection data.