Cross sections for hydrogen and helium producing reactions induced by fast neutrons on potential first wall materials of fusion reactor technology

Cross sections were measured for the 61Ni(n,p)61Co and 58Ni(n,α)55Fe reactions in the energy region of 5 to 10 MeV, using radiochemical separations and high resolution γ- and X-ray spectroscopy, respectively. An analysis of the systematic trends in the [(n,d)+(n,n'p)+(n,pn)] reaction cross sections at 14.7 +- 0.3 MeV was carried out. Cross sections were also measured for several (n,p), [(n,d)+(n,n'p)+(n,pn)], (n,α) and (n,n'α) reactions induced by a 30 MeV d(Be) break-up neutron spectrum, similar to the one expected in Fusion Materials Irradiation Test Facility (FMIT). Up to about 10 MeV incident neutron energy hydrogen and helium production is caused by (n,p) and (n,α) reactions, respectively. At 14-15 MeV the contributions of (n,n'x) processes are appreciable, the (n,n'p) process being exceptionally strong for target nuclei with neutron separation energies higher than the proton separation energies. With 30 MeV d(Be) break-up neutron spectrum, the contributions of (n,n'x) processes are significant for all the target nuclei. (Auth.)