Sensitivity analysis of core neutronic parameters in accelerator driven subcritical reactors

In this paper, sensitivity of the ADSRs core neutronic parameters to the accelerator related parameters such as beam profile, source multiplication coefficient (ks) and proton beam energy (Ep) has been investigated. TRIGA reactor has been considered as the case study of the problem. Monte Carlo code MCNPX has been used to calculate neutronic parameters such as: effective multiplication coefficient (keff), net neutron multiplication (M), spallation neutron yield (Yn/p), energy constant gain (G0), energy gain (G), importance of neutron source (φ*), axial and radial distributions of neutron flux and power peaking factor (Pmax/Pave) in two axial and radial directions of the reactor core for three eigen values levels (ks) including: 0.91, 0.97 and 0.99. According to the results, using a parabolic spatial distribution instead of a uniform spatial distribution increases the relative differences of spallation neutron yield, net neutron multiplication and energy gain by 4.74%, 4.05% and 10.26% respectively. In consequence the required accelerator current (Ip) will be reduced by 7.14% to preserve the reactivity. Although safety margin is decreased in highest case of ks, but energy gain increases by 93.43% and the required accelerator current and importance of neutrons source decrease by 48.3% and 2.64% respectively. In addition, increasing Ep from 115 MeV up to1 GeV, improves spallation neutron yield and energy gain by 2798.71% and 205.12% and decreases the required accelerator current and power by 96.83% and 72.44%, respectively. Therefore, our results are indicative of the fact that investigating sensitivity of the core neutronic parameters to the accelerator related parameters are necessary in order to optimally design a cost-efficient ADSR.