The spectral neutron fluence employed is that experimentally measured at the Triga reaction in Casaccia.
In requiring neutron fluence to ASIF reactor, it should be remembered that the niel dose is directly proportional to the required integral fluence, which, in turn, is directly proportional to the irradiation time.
The present Neutron NIEL calculator is based on values obtained with the software NJOY, developed by Los Alamos National Laboratory.
NIEL for compounds is determined by means of Bragg's rule , i.e., the overall NIEL in units of MeV cm2/g is obtained as a weighted sum in which each material contributes proportionally to the fraction of its atomic weight.
Currently, the lower energy limit for Neutrons NIEL is 1e-4 eV. The higher energy limit is 20 MeV.