Doppler coefficient for reactors containing thorium.

The Doppler increase in the effective resonance integral has been calculated for a model absorber which approximates the resonance structure of Th232. The results indicate that for rods of pure thorium the increase depends approximately on the square root of the temperature and very good agreement is obtained with experimental values of: 1/1 - dI/dT. The calculations also show that the addition of scattering material to the fuel rods will lessen the temperature dependence of the increase in the effective resonance integral