Fuel channel bore estimation for onload pressurised fuel grab load trace data

Accurate fuel channel bore estimation enables information about the health of the graphite core of an advanced gas-cooled reactor to be inferred. This was extensively explored previously for offload depressurised fuel grab load trace (FGLT) data: by isolating the frictional component of the FGLT and using inspection data as a ground truth, a linear regression model was trained to estimate the fuel channel bore. However, when data gathered during onload refuelling has the added complication of the interaction between the fuel assembly and coolant gas, the same process cannot be used. This paper describes the process for removing the aerodynamic effects of the coolant gas in the core from onload pressurised FGLT data. This effect cannot be directly measured, so initially, an empirical model was created by comparing the response from both offload depressurised and onload pressurised events. This model is then used to estimate the offload equivalent FGLT response, and by using a bore estimation model, trained on offload data, it is possible to produce bore estimations for onload FGLT data.