A model based nonlinear controller with an explicit integral action (M
RNCI) is theoretically applied to a liquid metal cooled nuclear reacto
r for controlling neutron power and core coolant output temperature us
ing rod position and primary pump fractional flow as manipulated varia
bles. The performance of the MRNCI is compared with the model based no
nlinear controller without any explicit integral action (MRNC) and als
o to that of the conventional PI controller. Under system parameters u
ncertainty, the performance of the MRNCI is superior to that of the MR
NC. Conventional PI controllers are shown to give an inferior performa
nce.