Total kinetic energy and fragment mass distributions from fission of Th-232 and U-233

Properties of fission in Th-232 and U-233 were studied at the Los Alamos Neutron Science Center at incident neutron energies from subthermal to 40 MeV. Fission fragments are observed in coincidence using a twin ionization chamber with Frisch grids. The average total kinetic energy released from fission and fragment mass distributions are calculated from observations of energy deposited and conservation of mass and momentum. Accurate experimental measurements of these parameters are necessary to better understand the fission process in isotopes relevant to the thorium fuel cycle, in which Th-232 is used as a fertile material to generate the fissile isotope of U-233. This process mirrors the uranium breeder process used to produce Pu-239 with several potential advantages including the comparative greater abundance of thorium, inherent nuclear weapons proliferation resistance, and reduced actinide production. Thus, there is increased interest in the thorium fuel cycle to meet future energy demands and improve safety and security while increasing profitability for the nuclear power industry. This research is ongoing and preliminary results are presented

Studies of fission fragment properties at the Los Alamos Neutron Science Center (LANSCE)

Nuclear data related to the fission process are needed for a wide variety of research areas, including fundamental science, nuclear energy and non-proliferation. While some of the relevant data have been measured to the required accuracies there are still many aspects of fission that need further investigation. One such aspect is how Total Kinetic Energy (TKE), fragment yields, angular distributions and other fission observables depend on excitation energy of the fissioning system. Another question is the correlation between mass, charge and energy of fission fragments. At the Los Alamos Neutron Science Center (LANSCE) we are studying neutron-induced fission at incident energies from thermal up to hundreds of MeV using the Lujan Center and Weapons Neutron Research (WNR) facilities. Advanced instruments such as SPIDER (time-of-flight and kinetic energy spectrometer), the NIFFTE Time Projection Chamber (TPC), and Frisch grid Ionization Chambers (FGIC) are used to investigate the properties of fission fragments, and some important results for the major actinides have been obtained

Studies of fission fragment properties at the Los Alamos Neutron Science Center (LANSCE)

Nuclear data related to the fission process are needed for a wide variety of research areas, including fundamental science, nuclear energy and non-proliferation. While some of the relevant data have been measured to the required accuracies there are still many aspects of fission that need further investigation. One such aspect is how Total Kinetic Energy (TKE), fragment yields, angular distributions and other fission observables depend on excitation energy of the fissioning system. Another question is the correlation between mass, charge and energy of fission fragments. At the Los Alamos Neutron Science Center (LANSCE) we are studying neutron-induced fission at incident energies from thermal up to hundreds of MeV using the Lujan Center and Weapons Neutron Research (WNR) facilities. Advanced instruments such as SPIDER (time-of-flight and kinetic energy spectrometer), the NIFFTE Time Projection Chamber (TPC), and Frisch grid Ionization Chambers (FGIC) are used to investigate the properties of fission fragments, and some important results for the major actinides have been obtained

Neutron-Induced Fission Cross-Section of 233-Pa between 1.0 and 3.0 MeV.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Calculation of the Neutron-Induced Fission Cross-Section of 233Pa.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Calculation of the Neutron Induced Fission Cross-Section of 233Pa up to 20 MeV.

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

Template for estimating uncertainties of measured neutron-induced fission cross-sections

A template for estimating uncertainties (unc.) of measured neutron-induced fission, (n,f), cross-sections (cs) is presented. This preliminary template not only lists all expected unc. sources but also supplies ranges of unc., estimates for correlations between unc. of the same and different experiments which can be used if the information is nonexistent. If this template is applied systematically when estimating experimental covariances for an evaluation, it may help in pinpointing missing unc. for individual datasets, identifying unreasonably low unc., and estimating correlations between different experimental datasets. Thus, a detailed unc. estimate – usually, a time-intensive procedure – can be undertaken more consistently and efficiently. As an example, it is shown that unc. and correlations of 239Pu(n,f) by Merla et al. [Proceedings of the Conference on Nuclear Data for Science and Technology 1991 Jülich (Springer-Verlag, Berlin, 1992) pp. 510–513], which are questionably low in the GMA database underlying the neutron cs standards evaluations, are distinctly larger at 14.7 MeV and more strongly correlated if this template is used for reestimating the associated covariances

Reply to "Comment on Calculation of the Neutron Induced Fission Cross-Section of 233Pa'"

Abstract not availableJRC.D-Institute for Reference Materials and Measurements (Geel

SPIDER: A new instrument for fission fragment research at the Los Alamos Neutron Science Center

The study of fission fragment yields and how they behave as a function of excitation energy provides insight into the process in which they are formed. Fission yields are also important for nuclear applications, as they can be used as a diagnostic tool. A new instrument, SPIDER (Spectrometer for Ion DEtermination in fission Research), is being developed for measuring fission yields as a function of incident neutron energy at the Los Alamos Neutron Science Center. The instrument employs a time-of-flight mass spectrometry method in which the velocity and kinetic energy of the fragments are measured in order to determine their mass. Additionally, by using Bragg peak spectroscopy, the charge of the fragments can be identified. A prototype instrument has been developed and preliminary results indicate that ∼ 1 mass unit resolution is feasible using this approach. A larger detector array is currently being designed, and will be used at study fission yields from thermal neutron energies up to at least 20 MeV