In the field of nuclear safety and the design of fast neutron reactors, the Chi-Nu experiment at Los Alamos National Laboratory (USA) provides essential and new data. This multi-year research is expected to influence the understanding and application of nuclear fission reactions.
The multi-year Chi-Nu project measured the energy spectrum of neutrons emitted during neutron-induced fission. This experiment recently completed the most detailed and extensive uncertainty analysis on the three major actinide elements:Uranium-238L'Uranium-235 and that Plutonium-239.
“Nuclear fission and associated chain reactions were discovered only just over 80 years ago, and experimentalists are still working to provide a complete picture of the fission processes for the major actinides,” commented Keegan Kelly, a physicist at Los Alamos National Laboratory. “During this project, we observed clear signs of fission processes that, in many cases, have not been observed in any previous experiments. »
Crucial data for nuclear fission and reactor design
The experiment measured the spectrum of uranium-238's fast fission neutrons: the energy of the fission-inducing neutron – the neutron that crashes into a nucleus and splits it – and the potentially expanded energy distribution (spectrum) of neutrons released after this fission.
Chi-Nu focuses on “fast neutron”-induced fission with incident neutron energies in the millions of electron volts, where measurements have traditionally been rare.
Combined with similar measurements on uranium-235 and plutonium-239, the results of the Chi-Nu experiments now represent, in many cases, the primary source of experimental data that guides modern efforts to evaluate instantaneous fission neutron spectra.
This data is incorporated into nuclear models, Monte Carlo calculations, reactor performance calculations and more.
Jaime Gomez (left) and Keegan Kelly work to set up the Chi-Nu experiment, calibrate distances between detectors and install gas lines for the Fision counting target (center).Credit: Los Alamos National Laboratory
Future Applications of Chi Nu Abilities
Researchers continue to build a complete picture of actinide isotopes. In related work funded by the Nuclear Safety and Criticality Program, the Chi-Nu experimental team is currently collecting and analyzing data on plutonium-240 and uranium-233.
Once the Office of Experimental Sciences measurements are completed, the team plans to apply the skills and methods learned from fission neutron measurements to a range of other isotopes. They are also focusing their efforts on measurements of neutrons emitted during neutron diffusion reactions, in which neutrons transport through a material and release energy in the process. The energy and angle spectra of the emitted neutrons and gamma rays as well as the probability of the reaction occurring, usually referred to as the neutron scattering cross section, are measured.
synthetic
The data provided by the Chi-Nu experiment at Los Alamos National Laboratory represents a significant contribution to understanding nuclear fission and improving applications related to nuclear safety and reactor design. These results, which are part of a rigorous and detailed scientific approach , promise to positively influence technological progress in the field of nuclear energy.
For better understanding
What is the Chi Nu Experience?
The Chi-Nu experiment is a research project at Los Alamos National Laboratory that measured the energy spectrum of neutrons emitted during neutron-induced nuclear fission.
Which actinide elements were studied by Chi-Nu?
Chi-Nu analyzed the major actinide elements such as uranium-238, uranium-235 and plutonium-239.
How important is the data collected by Chi-Nu?
Chi-Nu data is critical for controlling nuclear models, reactor performance calculations, and other nuclear safety applications.
What are the future applications of the skills acquired by the Chi Nu team?
The Chi-Nu team plans to apply its skills in measuring fission neutrons to other isotopes and studying neutron diffusion reactions.
What's next for Team Chi-Nu?
The team continues to analyze isotopes such as plutonium-240 and uranium-233 and search for new measurements in the area of neutron scattering.
References
Photo caption: Physicist Keegan Kelly sets up a fision counting target for a Chi-Nu experiment that contains about 100 milligrams of an interesting actinide. The device includes 54 liquid scintillation neutron detectors and 22 lithium glass detectors for measuring neutrons in different energy ranges.
Article: “Measurement of the 238U(n, f) neutron spectrum of instantaneous fission from 10 keV to 10 MeV induced by neutrons with an energy of 1.5–20 MeV.” Physical Review C. DOI: 10.1103/PhysRevC.108.024603
[ Rédaction ]