An international team of nuclear physicists, with the participation of the Complutense University of Madrid and the Institute of Particle Physics, discovered that the fragments produced by nuclear fission only gain angular momentum after fission, which was not previously thought as before. This discovery may help to understand gamma radiation heating in nuclear reactors.
An international study was published in natural among them Nuclear Physics Group (GFN-UCM) IPARCOS Institute Researchers at the University of Complutense (UCM) in Madrid have determined how and when the fragments produced by the fission of atomic nuclei rotate during the fission process.
During this period Nuclear ruling One heavy nucleus splits into two lighter nuclei, releasing a lot of energy, leading to a variety of applications, such as power generation in nuclear power plants.
The fission process was discovered at a later stage 30 years The chemists Otto Hahn and Fritz Strassmann and the physicists Lise Meitner and Otto Frisch were both 20th Century. Nearly 90 years have passed since then, but to this day, there are still many problems.
The authors of this new study investigated how and why the fragments produced by nuclear fission have a high Angular MomentumIn other words, even if the original atomic nuclei are not rotating, they will spontaneously and rapidly rotate.
“Most current theories assume that the rotation of fission fragments is generated before the nucleus splits, which will cause a correlation between the rotations of the two fragments produced in the fission. However, our work shows that the fragments produced by nuclear fission It acquires its inherent angular momentum (rotation) after fission rather than before. Luis Mario FraileHe is a researcher at UCM, and his team has contributed to the preparation of experiments, data collection and analysis, and scientific discussions.
New information about the role of angular momentum in nuclear fission will improve the understanding of the fission process itself. It is also useful for other research fields, such as the study of structures. Neutron-rich isotope, And synthesis and stability Overweight element.
“In addition, it can have practical applications, for example, to help understand Gamma radiation heating In a nuclear reactor,” Fraile pointed out.
About thirty research institutes that study alien nuclei
The experiment is on ALTO accelerator from Irène Joliot-Curie Laboratory (IJC) in Orsay, FranceThanks to this collaboration, the International Group of Nuclear Physicists has made it possible No ball, Its purpose is to study the generation mechanism and structure of various exotic nuclei.
The collaboration led by IJC has researchers from 37 research institutes in 16 countries and regions. In addition to UCM, Institute of Particle Physics (IFIC), A hybrid center of CSIC and the University of Valencia.
In order to reveal the mechanism of fragment spin generation, the research team initiated a nuclear fission reaction at the ALTO facility and measured the gamma rays emitted during the process. Specifically, uranium 238ü And thorium 232thorium Use pulsed neutron beams.
A detailed analysis of the emitted gamma rays shows that Spin In fission, it is actually produced after nuclear fission. Experiments show that the average spin is related to the mass of the sawtooth fragments.
However, the average spin of these two fragments (which can be divided into different mass ratios) does not seem to be related to the quality of their related fragments.
The lead author of the study said: “What really surprised us was the lack of a significant dependence on the average spin observed in the fragment relative to the minimum spin required for the relevant fragment.” Jonathan WilsonIJC.
“Most theories that assume that the spin is generated before fission predict a strong correlation, but our results show that the spin of the fragment is generated after fission. It can be explained. Like a rubber band It further points out that turning force is generated when it breaks,” Wilson said.
John Wilson (JN Wilson) and others. “Angular Momentum Production in Nuclear Fission”, natural, 2021