Fast neutron dosimetry in criticality accidents

Indium is suggested as a possible dosimeter for measuring fast neutron dose in supercritical accidents under the scattered-free condition. Neutron dosimetrical parameters, namely, the fission spectrum-averaged cross-sections of some threshold reactions and fluence-to-dose conversion factors have been calculated by the use of an electronic computer. One of the results is that the average cross-sections for the 32S(n,p)32P reaction are independent of spectral functions, namely the modified Cramberg and Maxwellian form. It is shown that the Maxwellian form is shifted towards high energy compared with the modified Cramberg form and subsequently gives average cross section value higher than the latter form for threshold detectors whose threshold energies are relatively high. The necessary data for neutron fluence-to-dose conversion factors in terms of kerma and maximum dose, are also provided. It is concluded that: the average cross section for the 115In(n,n')sup(115m)In is insensitive to a variation of spectral functions considered and of the fissioning types; the fluence-to-dose conversion factors is not sensitive to the varying neutron energy causing fission; these phenomena make indium applicable as an integral fast neutron dosimeter in supercritical accidents