Decomposition of refuelling signals to estimate channel bore profiles

The fuel grab load trace (FGLT) generated during refuelling is a primary source of information relating to the structural health of the AGR cores. These refuelling events are routinely analysed and any anomalous behaviour reported at the station Monitoring Assessment Panel meetings. The FGLT is measure of the apparent weight of the fuel stringer as it travels through the graphite core. A number of components contribute to the measured weight, such as aerodynamic effects of coolant gas flow and friction caused by stabilising brushes on the fuel stringer interacting with the walls of the fuel channel. This paper describes a process for isolating each of these components from the FGLT. Separating out the effect of the lower stabilising brushes is particularly beneficial, as this provides a much improved representation of the channel bore, and thus characterisation of any underlying defects. This is valuable for detecting anomalies in regions of the core where the net effect of the upper and lower stabilising brushes results in masking of the graphite brick bore profile.