Effect of changing the outer fuel element diameter on thermophysical parameters of KLT-40S reactor unit

Abstract

This paper contains the results of KLT-40S reactor unit thermophysical studies and describes its main design features. Such quantities as fuel burnup, Reynolds and Prandtl numbers, coolant flow velocity, temperature distributions for fuel and fuel rod cladding, and departure from nucleate boiling ratio up to boiling crisis were calculated for different fuel rod diameters and fuel compositions. It is shown that changing the dispersed fuel composition from (U238 + U235)O2 to (Th232 + U233)O2 does not alter the maximal temperatures of fuel and fuel rod cladding significantly. An increase in the outer fuel rod diameter up to 7.2 mm leads to a decrease in the maximal temperatures of fuel and fuel rod cladding. Maximal temperatures of fuel and fuel rod cladding do not exceed melting temperatures for silumine and E635 alloy, respectively. Coolant flow velocity for all fuel rod diameters does not exceed 10 m/s and there is no boiling crisis.