By a simple procedure , what should I do when I'm going through the thermal hydraulic design of nuclear reactor core...? .. I put initial guesses for the core dimensions ( fuel , clad , gap , length) initial guess for the fuel element pitch desired power ... I've found q'' critical heat flux based on the correlation in "Nuclear Systems I - Thermal Hydraulic Fundamentals - Todreas" I've found q'max ( based o DNB =1.3 ) q'avg based on ( hot spot factor =2 ) and based on q'max I've found the temperature distribution in one single fuel rod ... The results after assuming we have only 1 assembly inside the core that produces 17.6 MWth All fuel rods have the same enrichment the reflector will take care of the leakage to produce the desired power we need 188 fuel rods inside the assembly Rf = 0.405 cm (fuel pellet radius) Tg = 0.005 cm (gap thickness) Tc = 0.05 cm (clad thickness) Lr = 360 cm (fuel rod length) fuel element pitch (p) = 1.3 cm Pressure 15.5 Mpa with coolant flux flow rate 436 kh/hr.cm2 in one single channel I've found that ΔTF ( temperature drop through the fuel pellet) = 1656.5 C ΔTg ( temperature drop through the gap) = 511.3 C ΔTC ( temperature drop through the clad) = 95 C ΔTC ( temperature drop through the coolant) = 18 C .. does this sounds correct because I sill don't have that sense of the numbers...!!