The Impact of Isotopic Composition of Lead on the Neutron-Physical Characteristics of Fast Reactor with Liquid Metal Coolant

It is well known, that lead coolant, highly enriched by 208Pb, has some advantages over other coolants. It is predicted that the use of 208Pb in the reactor core will lead to an increase in the production of plutonium and transmutation of long-lived decay products. The main objective of this paper was to investigate the influence of the isotopic composition on the fast reactor neutron-physical characteristics. For this purpose we used the RBETS-M benchmark - a fast energy reactor that includes 12 zones with different sizes and temperatures of the materials. Calculations were performed for homogeneous and heterogeneous models. Our calculations show that the replacement of the coolant with the natural lead to 208Pb and 208Pb together with Bi can substantially improve the neutron-physical characteristics of the fast reactor, in particular by reducing the initial reactivity margin. Studies of the heterogeneity effect in the reactor model showed an increase in the effective multiplication factor of about 1.5% at the end of the campaign.

Defects in Electron and Neutron Irradiated n-GaN: Disordered Regions Versus Point Defects

ABSTRACTEffects of 10 MeV electron and fast reactor neutron irradiations on carrier removal rate and deep traps spectra were compared for undoped n-GaN samples. It is shown that for electron irradiation the carrier removal rate is well accounted for by the difference in introduction rates of nitrogen-vacancy-related donors with activation energy 0.2 eV and of nitrogen-interstitial-related acceptors at Ec-1.2 eV. In the case of neutron irradiation the introduction rate of all deep traps was much lower than the carrier removal rate indicating that the main contribution to electron removal was due to disordered regions. These regions give rise to a marked persistent photocapacitance signal and a hole-trap-like feature in deep traps spectra. The Fermi level position in the core of disordered regions is located near Ec-(0.85-1) eV.

Electrical Properties, Deep Levels Spectra and Luminescence of Undoped GaN/InGaN Multi-quantum-well Structures as Affected by Electron Irradiation

ABSTRACTEffects of 10 MeV electron and fast reactor neutron irradiations on carrier removal rate and deep traps spectra were compared for undoped n-GaN samples. It is shown that for electron irradiation the carrier removal rate is well accounted for by the difference in introduction rates of nitrogen-vacancy-related donors with activation energy 0.2 eV and of nitrogen-interstitial-related acceptors at Ec-1.2 eV. In the case of neutron irradiation the introduction rate of all deep traps was much lower than the carrier removal rate indicating that the main contribution to electron removal was due to disordered regions. These regions give rise to a marked persistent photocapacitance signal and a hole-trap-like feature in deep traps spectra. The Fermi level position in the core of disordered regions is located near Ec-(0.85-1) eV.