The experimental dependence of the alpha,f and T-n parameters, in function
of the water thickness, for different irradiation channels of Triga Mark II
I reactor, were analyzed. An exponential law for the alpha(r) dependence wa
s obtained in the neighborhood of the active zone of the reactor numericall
y modelated using the S-n method for 69 neutrons groups, and this dependenc
e is slower in light water reactors than in graphite reactors.