Accelerator radiation protection: Recourse to nuclear reaction models

Abstract

Nuclear reaction models play a very crucial role in theoretical estimation of radiation environment in accelerator facilities where experimental data are scantily available. In this paper, we discuss the exciton and hybrid models for pre-equilibrium reaction, the Weiskopf-Ewing formalism for compound nuclear emissions and quantum molecular dynamics (QMD) model for spallation reactions. The choice of Fermi gas or Gilbert Cameron level density results in a variation of 21% in the neutron yield from p + Cu reaction at 20 MeV. The surface effects, which are more pronounced at higher energies influence the organ absorbed dose at most to 5% even at 60 MeV for the same reaction. The code EMPIRE and the hybrid model code ALICE give a reasonable estimate of dose and induced activity in proton accelerator facilities up to about 200 MeV until when pion production is not significant. The code HION can be a preferred choice for neutron dose simulation in low energy heavy ion (HI) accelerators. However, the model needs improvement for more accurate estimation of the angular distribution. QMD model can be used to estimate the induced activity and absorbed dose for proton and HI reactions at several hundreds of MeV to GeV per nucleon.