Jaime Gomez (left) and Keegan Kelly work to establish the Chi-Nu experiment, calibrating detector ranges and setting up gas lines for the fission-counting target (center). Credit: Los Alamos National Laboratory
Experiment measures the energy spectrum of neutrons given off from neutron-induced fission.
The results of the Chi-Nu physics experiment at the Department of Energys Los Alamos National Laboratory have actually contributed necessary, never-before-observed data for enhancing nuclear security applications, comprehending urgency security, and designing fast-neutron energy reactors. The Chi-Nu task, a years-long experiment measuring the energy spectrum of neutrons emitted from neutron-induced fission, just recently concluded the most detailed and substantial unpredictability analysis of the three major actinide aspects– uranium-235, plutonium-239, and uranium-238.
” Nuclear fission and related nuclear domino effect were just found a little bit more than 80 years earlier, and experimenters are still working to offer the complete photo of fission processes for the major actinides,” said Keegan Kelly, a physicist at Los Alamos National Laboratory. “Throughout the course of this job, we have actually observed clear signatures of fission procedures that in most cases were never ever observed in any previous experiment.”.
The Los Alamos groups final Chi-Nu research study, on the isotope uranium-238, was recently published in the journal Physical Review C. The experiment measured uranium-238s prompt fission neutron spectrum: the energy of the neutron inducing the fission– the neutron that crashes into a nucleus and splits it– and the potentially extensive energy distribution (the spectrum) of the neutrons released as an outcome. Chi-Nu concentrates on “fast-neutron-induced” fission, with incident neutron energies in countless electron volts, where there have typically been very couple of measurements.
Physicist Keegan Kelly installs a fission-counting target consisting of approximately 100 milligrams of an actinide of interest for a Chi-Nu experiment. The device consists of 54 liquid scintillation neutron detectors and 22 lithium-glass detectors to determine neutrons in different energy varieties. Credit: Los Alamos National Laboratory.
Important Data for Fission-Related Work.
Together with similar measurements on uranium-235 and plutonium-239, the arise from the Chi-Nu experiments are now, oftentimes, the dominant source of speculative information assisting contemporary efforts to assess the prompt-fission-neutron spectrum. The data inform nuclear models, Monte Carlo estimations, reactor efficiency computations, and more.
When a nucleus goes through fission, or divides, several neutrons are released, potentially inducing fission in surrounding nuclei to create the chain reaction. The likelihood of subsequent responses in the chain depends on the energy of the fission neutrons.
Experimentation Process at LANSCE.
Conducted at the Weapons Neutron Research facility at the Los Alamos Neutron Science Center (LANSCE), the Chi-Nu experiment relied on an advanced apparatus screening numerous energy varieties. Neutrons discharged from the fission event are then measured in either the liquid scintillator or lithium-glass detector ranges, depending on the experiments energy variety, with both detectors taping flashes of light caused within the detectors by the neutrons.
Future Applications of Chi-Nu Skills.
Researchers continue designing the full photo of actinide isotopes. In adjacent work funded by the Nuclear Criticality and Safety Program, the Chi-Nu speculative team is presently collecting and examining information on plutonium-240 and uranium-233.
And with the Office of Experimental Sciences measurements now concluded, the team is wanting to use the skills and methods theyve gotten with fission neutron measurements to a series of other isotopes. They are likewise shifting efforts towards measurements of neutrons released from neutron scattering responses. In these responses, neutrons transport through a material while depositing energy. The emitted neutron and gamma-ray energy and angular spectra are measured in addition to the likelihood for the response to occur, typically described as the neutron scattering cross-section.
Reference: “Measurement of the 238U( n, f) prompt fission neutron spectrum from 10 keV to 10 MeV caused by neutrons with 1.5– 20 MeV energy” by K. J. Kelly, M. Devlin, J. M. ODonnell, D. Neudecker, A. E. Lovell, R. C. Haight, C. Y. Wu, R. Henderson, E. A. Bennett, T. Kawano, J. L. Ullmann, N. Fotiades, J. Henderson, S. M. Mosby, T. N. Taddeucci, P. Talou, M. C. White, J. A. Gomez and H. Y. Lee, 14 August 2023, Physical Review C.DOI: 10.1103/ PhysRevC.108.024603.
Funding: The U.S. Department of Energy through Los Alamos National Laboratorys Office of Experimental Science.
The experiment measured uranium-238s prompt fission neutron spectrum: the energy of the neutron inducing the fission– the neutron that crashes into a nucleus and splits it– and the possibly comprehensive energy distribution (the spectrum) of the neutrons released as a result. The device consists of 54 liquid scintillation neutron detectors and 22 lithium-glass detectors to measure neutrons in different energy ranges. Performed at the Weapons Neutron Research facility at the Los Alamos Neutron Science Center (LANSCE), the Chi-Nu experiment relied on an advanced apparatus testing numerous energy ranges. Neutrons released from the fission event are then measured in either the liquid scintillator or lithium-glass detector arrays, depending on the experiments energy variety, with both detectors taping flashes of light induced within the detectors by the neutrons.
The released neutron and gamma-ray energy and angular spectra are measured along with the likelihood for the reaction to take place, usually referred to as the neutron scattering cross-section.
