Related Experiment Video
Updated: Jul 20, 2026
10:24
Neutron Radiography and Computed Tomography of Biological Systems at the Oak Ridge National Laboratory's High Flux Isotope Reactor
Published on: May 7, 2021
Neutron cross section measurements at ORELA for improved nuclear data and their application
K H Guber1, L C Leal, R O Sayer
1Oak Ridge National Laboratory, P.O. Box 2008, MS 6354, Oak Ridge, TN 37831-6354, USA. guberkh@ornl.gov
Radiation Protection Dosimetry
|April 11, 2006
Summary
New measurements of neutron cross sections for elements like aluminum and silicon show significant differences from existing nuclear data. These findings impact nuclear criticality safety calculations.
Area of Science:
- Nuclear physics
- Neutron cross-section measurements
- Nuclear data evaluation
Background:
- Existing nuclear cross-section data used in criticality calculations may be inaccurate.
- The Nuclear Criticality Safety Program requires reliable neutron cross-section data.
- Evaluated nuclear data files like ENDF/B-VI and JENDL-3.2 may contain discrepancies.
Purpose of the Study:
- To measure total and capture neutron cross sections for key nuclides.
- To address concerns regarding the accuracy of current nuclear data.
- To provide updated cross-section data for improved nuclear criticality safety.
Main Methods:
- Utilized the Oak Ridge Electron Linear Accelerator (ORELA) for neutron generation.
- Conducted measurements of total and capture neutron cross sections.
- Focused on the energy range from 100 eV to 600 keV.
Main Results:
- New capture cross-section data for aluminum, silicon, chlorine, fluorine, and potassium were obtained.
- These new measurements in the 100 eV to 600 keV range differ substantially from ENDF/B-VI and JENDL-3.2 data.
- Significant discrepancies were observed between experimental results and evaluated nuclear data files.
Conclusions:
- The study highlights potential inaccuracies in current evaluated nuclear data files.
- Revised cross-section data are necessary for accurate nuclear criticality safety assessments.
- The findings necessitate an update of nuclear data libraries to reflect experimental measurements.
More Related Videos
Related Concept Videos
03:08Atomic Radii and Effective Nuclear Charge
The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number and distribution of electrons in their valence shells.
02:13Nuclear Binding Energy
The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy is the energy produced when the atoms’ nucleons are bound together;...
00:59Atomic Nuclei: Nuclear Magnetic Moment
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:06Nuclear Overhauser Enhancement (NOE)
Irradiation of a spin-active nucleus causes an increase or decrease in the signal intensity of neighboring nuclei that are not necessarily chemically bonded or involved in J-coupling. This phenomenon, called the nuclear Overhauser enhancement (NOE), results from through-space interactions between the nuclear spins. The NOE effect decreases with increasing internuclear distance and is generally not observed beyond 4 angstroms. In NOE, dipole-dipole interactions between neighboring spin-active...