Fission probabilities have important implications both on the neutron production of the p-nucleus reaction and on the production of nuclear waste. Figure 6.3 compares experimental fission cross-sections for the highly fissile 235U to calculations using the Bertini code with or without

pre-equilibrium treatment. It is seen that, in this case, the pre-equilibrium treatment does not influence the results very much. This is a consequence of the very high fission probability. For neutron energies below 100 MeV, all INC calculations become unsatisfactory. This reflects a deficiency of the INC codes in reproducing reaction cross-sections below that energy. Figure 6.4 compares experimental fission cross-sections for the poorly fissile 208Pb with calculations using the Bertini and the ISABEL INC codes

with or without pre-equilibrium treatment, and for different level densities. Here the interest of the pre-equilibrium treatment is far from obvious. The standard level density is that of Igniatyuk [101] and gives the best results. The Julich level density [84] includes the effects of shells on level densities but not the washing out of these effects with temperature. It clearly under­estimates the level density. In any case, as stated earlier, it seems clear that progress has to be made in the fission treatment.