Analysis on Enrichment and Mass of Uranium Materials With Time-Correlated Measurement
Abstract Effective determination for enrichment of the uranium materials in heavy shielding is technically difficult to solve. Various technical methods so far have been proposed to deal with this problem. With the time-correlated coincidence measurement method, 14 MeV neutrons and fission spectrum neutrons are chosen to interrogate the uranium samples with different masses and enrichments. The fission spectrum neutrons are obtained by slowing down the 14 MeV neutrons. Results have shown that a good linear relationship exists between masses of the uranium materials (⩽10% enriched 235U) that possess the same enrichment. A linear relationship also exists between enrichments of the uranium materials that possess the same mass.
252Cf source-correlated transmission measurements and genetic programming for nuclear safeguards
One of the main targets of nuclear safeguards is to determine the mass and enrichment of fissile samples enclosed in special, non-accessible containers. In this paper, we present a method to estimate the mass of uranium oxide samples based on 252Cf source-driven noise-analysis measurements. We show that the mass of the samples can be successfully predicted using a genetic programming algorithm. The input presented to the algorithm was in the form of features extracted from the physical properties of the measured correlation functions.
Validation of Geant4 and MCNPX-PoliMi simulations of fast neutron detection with the EJ-309 liquid scintillator
Abstract In organic liquid scintillators, the energy distribution of neutrons is indirectly measured by characterizing the pulse height distribution of light output produced through nuclear reactions within the detectors. However, the complexity of the light generation on these detectors makes simulating their response difficult with standard Monte Carlo techniques. This paper presents the response of 7.62-cm-long×7.62-cm-diameter and 12.7-cm-long×12.7-cm-diameter EJ-309 liquid scintillators, simulated using the Geant4 and MCNPX-PoliMi Monte Carlo codes. The simulations are restricted to the neutron transport and interaction models. Monoenergetic neutrons as well as fission neutrons emitted by a 252 Cf spontaneous fission source are used in these simulations. The energy deposition of neutrons in organic liquid scintillators is dependent upon their collisions with hydrogen and carbon nuclei; therefore simulating neutron collisions on an event-by-event basis is important to generate neutron pulse height distributions. There are no default physics models in Geant4 hence proper selection of physics models is required for accurate simulation. In this paper, we compare Geant4 (ver. 4.9.5) and MCNPX-PoliMi (ver. 2.0) neutron pulse height distributions. The simulations are validated with time-of-flight (TOF) measurements obtained with 12.7-cm-long×12.7-cm-diameter EJ-309 detectors. Results show that both Geant4- and MCNPX-PoliMi-generated distributions are in good agreement with the measured data.