"HOT" in nuclear jargon usually means radioactive. Used uranium fuel is "hot" because it contains fission products, which are radioactive.
Nuclear reactor startup usually involves withdrawal of several control rods from the core. The control rods contain boron-10 and eat up neutrons, but do not have chain reaction themselves; hence stopping chain reaction, so pulling them out enables chain reaction to increase.
If fuel rods are actually hot (temperature) then chances are they are also "hot" (radioactive), since the source of heat in the fuel is the fission chain reaction that produces radioactive fission products.