The interpretation of kinetic experiments for source-driven systems is often based on the relationship betwen the prompt time response and the multiplicativity of the system. The presence of a reflector may modify the physical features of such responce. For systems in which the neutron hisories are dominated by the presence of the reflector, it becomes difficult to determine the subcriticality value through the observation of the flux response. In this work the characteristics of this phenomenon are analysed, starting from a simple diffusion model that allows to easily get a physical insight. The modification of the time constant is interpreted in terms of modifications to the effective mean prompt neutron generation time, which is increased by the presence of the reflector. Spectral effects, that may also be very significant, are investigated. Afterwards, more realistic evaluations are carried out by using Monte Carlo simulations of pulsed experiments in source-driven systems. The results confirm the conclusions that may be drawn from the analysis of the simple cases.
REFLECTOR EFFECTS ON THE KINETIC RESPONSE IN SUBCRITICAL SYSTEMS
SARACCO, PAOLO;LOMONACO, GUGLIELMO;
2015-01-01
Abstract
The interpretation of kinetic experiments for source-driven systems is often based on the relationship betwen the prompt time response and the multiplicativity of the system. The presence of a reflector may modify the physical features of such responce. For systems in which the neutron hisories are dominated by the presence of the reflector, it becomes difficult to determine the subcriticality value through the observation of the flux response. In this work the characteristics of this phenomenon are analysed, starting from a simple diffusion model that allows to easily get a physical insight. The modification of the time constant is interpreted in terms of modifications to the effective mean prompt neutron generation time, which is increased by the presence of the reflector. Spectral effects, that may also be very significant, are investigated. Afterwards, more realistic evaluations are carried out by using Monte Carlo simulations of pulsed experiments in source-driven systems. The results confirm the conclusions that may be drawn from the analysis of the simple cases.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
