Abstract
The heat pulse method for determining thermal diffusivity α is investigated to ascertain if it can be applied to determine thermal conductivity changes of graphite and ceramics under neutron irradiation. It is verified that heat losses and a finite pulse time effect alter the temperature-time curve for the specimen rear face. The variation of the parameter ω in the relationship α = ωL2/π2t1/2 is determined experimentally for t1/2 values in the range 0.002 to 16 sec. When considerable heat loss occurs a reliable diffusivity value can still be obtained from the relationship α = 0.48 L2/π2tx by measuring tx, the time axis intercept at zero temperature rise.