Enhancing tritium breeding characteristics of a fusion reactor blanket

In this paper we have reported our results of a detailed time dependent study of neutron spectra, tritium production rate, tritium breeding ratio, slowing down time and average energy following a pulse of 14 MeV neutrons in Li+C assemblies of different sizes. We have solved the time dependent diffusion equation with energy dependent buckling as an eigenvalue problem. Our results show that an initial 14 MeV pulse slows down to the keV region within about 200 ns after its injection. At later times, its energy decreases rather slowly because elastic scattering is the sole mechanism of energy loss. Since most of the tritium producing reactions take place with neutrons having energies in this region, the tritium production rate is higher in a Li+C system than a corresponding natural lithium assembly. Moreover, in Li+C the calculated value of TBR is almost twice the value obtained for a natural lithium assembly of the same size. Also, by varying the concentration of Li-6 we find that the value of TBR tends to saturate beyond about 40%. (C) 1997 Elsevier Science Ltd.