Heat deposition analyses were conducted for the High Flux Isotope Reactor (HFIR) highly enriched uranium (HEU) and low enriched uranium (LEU) cores with a representative target loading and explicit involute fuel plate representation. The analyses were focused on determining on a fine mesh the heat deposited in various regions of the fuel elements: fuel plates (filler, clad, fuel meat); water channels between fuel plates; and sidewalls of the fuel elements. The results show that for the HEU core, approximately 94% of the power is deposited in the fuel regions at beginning and end of cycle, and the other 6% is distributed throughout other reactor regions: flux trap target, control element, and reflector. For the LEU core, approximately 96% of the power is deposited in the fuel regions at beginning of cycle. This paper summarizes the computational approach used and the results for the in-depth heat deposition analyses of HFIR HEU and LEU models, with explicit fuel plate representation, which have not been conducted prior to this work.