*3.1.4 FCCAL code methodology*

FCCAL is written in Fortran computer programming language. It is used to calculate fuel centerline temperature, fuel surface temperature, and average coolant temperature in steady-state as well as transient conditions as a function of coolant flow rate (Kg/s), bundle power (Kw), Fuel burnup (MWD/TeU), average channel power (Kw) and actual coolant temperature. For the start of the iteration, a guess value of fuel centerline temperature is assumed taking into account the fact that the fuel centerline temperature cannot be less than the coolant temperature for a reactor operating at steady power. The heat generated in the fuel is taken away by the coolant and transferred to the steam drum and further goes on to generate electricity. Equivalent thermal conductivity across the pellet, plenum gap, clad, and heat transfer to the coolant is calculated. The results are compared with the actual instrument measurements and the guess temperature is accordingly re-evaluated. The guess temperature is accepted to be correct when the error in the code computed values and the instrumented value is within �2°C. The instrumented temperature is measured from platinum resistance temperature detectors. An error of this magnitude is acceptable as the instrument measurement error is �2°C.
