Studies of 54,56 Fe Neutron Scattering Cross Sections
Elastic and inelastic neutron scattering differential cross sections and γ-ray production cross sections have been measured on 54,56 Fe at several incident energies in the fast neutron region between 1.5 and 4.7 MeV. All measurements were completed at the University of Kentucky Accelerator Laboratory (UKAL) using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. The facilities at UKAL allow the investigation of both elastic and inelastic scattering with nearly mono-energetic incident neutrons. Time-of-flight techniques were used to detect the scattered neutrons for the differential cross section measurements. The measured cross sections are important for fission reactor applications and also for testing global model calculations such as those found at ENDF, since describing both the elastic and inelastic scattering is important for determining the direct and compound components of the scattering mechanism. The γ-ray production cross sections are used to determine cross sections to unresolved levels in the neutron scattering experiments. Results from our measurements and comparisons to model calculations are presented.
Investigation of Neutron Cross Section for Iron in the ENDF Library with Pulsed Sphere Measurements
Abstract This work investigates the quality of the ENDF 56Fe cross-section libraries for describing the transport of fast neutrons in iron. We have used the D(d,n)3He reaction with a pulsed 7-MeV deuteron beam energy as a neutron source and analyzed the neutrons transmitted through two natural iron spheres of thicknesses 3 and 8 cm. The experimental neutron time-of-flight transmitted spectra for various angles are compared with MCNP simulations. Our result indicates the possibility of an underestimation of the nonelastic cross section and an overestimation of the elastic cross section for 56Fe in the ENDF/B-VII.1 library for the neutron energy range of 7.2 to 10.2 MeV. Our result agrees qualitatively with the Ramsauer model and optical model calculations. This discrepancy in the library cross section might lead to an underestimation/overestimation of material damage in nuclear reactor calculations. A newer evaluation, ENDF/B-VIII.0, was released subsequent to the completion of the majority of this project. The new evaluation has a decreased elastic cross section and an increased inelastic cross section for 56Fe in our energy range of interest, which agrees qualitatively with our result.
Time behavior of gas pressure and PD activity in insulation cavities under AC voltage
In the framework of developing defect-based life models (i.e. the life model of partial discharge-induced damage growth from a micro-void in polymer matrix), ageing tests were performed on PE layered specimens with artificial cavities under constant gas pressure and constant gas volume conditions, respectively. Time behavior of the discharge repetition rate and amplitude were recorded and compared under these two conditions. Results show that pressure variation has little influence on PD activities at constant gas volume. Under constant gas pressure, the evolution of gas volume has similar characteristic to the product of discharge amplitude and repetition rate.