On September 26, 2023, Los Alamos National Laboratory announced the successful conclusion of the Chi-Nu physics experiment, which has provided valuable data to enhance nuclear security, criticality safety, and the development of fast-neutron energy reactors. The project focused on analyzing the prompt fission neutron spectrum of uranium-238, uranium-235, and plutonium-239, offering significant insights for these applications.
Actinide elements, which include uranium and plutonium, play a crucial role in nuclear weapons and energy reactors. The Los Alamos National Laboratory stated, "Actinide elements, and the chain reactions they can undergo, are important for nuclear weapons and energy reactors."
The Chi-Nu experiment concentrated on examining the prompt fission neutron spectrum of uranium-238, specifically studying the energy of the initiating neutron and the subsequent distribution of released neutrons during fission. This research, along with similar investigations of uranium-235 and plutonium-239, has become a primary source of experimental data, providing valuable guidance for assessing the prompt-fission-neutron spectrum.
Keegan Kelly, a physicist at Los Alamos National Laboratory, highlighted the significance of the project, stating, "Throughout the course of this project, we have observed clear signatures of fission processes that in many cases were never observed in any previous experiment."
The Chi-Nu study on the uranium-238 isotope, titled "Measurement of the 238U(n, f) prompt fission neutron spectrum from 10 keV to 10 MeV induced by neutrons with 1.5–20 MeV energy," has recently been published in the journal Physical Review C. This research is dedicated to investigating "fast-neutron-induced" fission, focusing on incident neutron energies in the millions of electron volts range, an area that has historically lacked measurements.
In parallel efforts, funded by the Nuclear Criticality and Safety Program, the Chi-Nu experimental team is currently gathering and analyzing data related to plutonium-240 and uranium-233. These additional studies aim to further enrich the understanding of fission processes and contribute to advancements in nuclear security and energy reactor applications.
The Chi-Nu experiment at Los Alamos National Laboratory has provided crucial data that enhances nuclear security, criticality safety, and the development of fast-neutron energy reactors. The findings from this project contribute to the ongoing research on actinide elements and their chain reactions, which are vital for nuclear weapons and energy reactors. The analysis of the prompt fission neutron spectrum of uranium-238, uranium-235, and plutonium-239 offers valuable insights for assessing the prompt-fission-neutron spectrum. The Chi-Nu study, focusing on fast-neutron-induced fission, has filled a gap in measurement data for incident neutron energies in the millions of electron volts range. The publication of the Chi-Nu study on the uranium-238 isotope demonstrates the commitment of the research team to sharing their findings with the scientific community. Additionally, ongoing efforts to gather and scrutinize data on plutonium-240 and uranium-233 will further contribute to the knowledge of fission processes and their applications in nuclear security and energy reactors.