A thermal model to characterize the flattening effect of a nuclear fuel element in an annular channel using simple analytical approach

In the present work, axial power flattening effect due to insertion of adjuster rods is modeled and a heat generating fuel pin in an annular channel is characterized. The effect of insertion of single adjustor rod at the peak heat generation region is modeled as two heat sources and one heat sink. The results obtained from the developed model indicate that insertion of adjuster rods beyond a critical number (3-4); flattening effect does not improve much. The peak surface and centerline temperatures of fuel pin are observed to show a cyclic variation and shift towards end as compared to unadjusted profile. Results are in accordance with the best estimate RELAP code.