Calculational and experimental studies of reactivity temperature effects in heterogeneous critical assemblies with a heavily-blocked absorber

Reactivity temperature effects have been studied in a wide temperature range (20-240 deg C) on 6102-water critical assemblies of the TAS-3M reactor containing Cd and Gd absorber rods uniformly spread in the fuel element lattices. Studied have been three critical assembly arrangements differing in a number of fuel elements, absorbers and absorber material. Reactivity was measured by two techniques: 1) measurement of the drho/dT=f(T) function followed by its integration; 2) measurement by a pulse technique at a fixed location of a boron steel compensating rod. The calculations were conducted in the two-group diffusion approximation using a multizone reactor model in the (r,z) geometry. A satisfactory agreement between both the two independent experimental techniques and the calculations is stated