The researchers of the Institute of Corpuscular Physics (IFIC), research center of the University of Valencia Science Park (PCUV), Gustavo Alcalá and Alejandro Algora, from the group of Gamma Spectroscopy and Neutrons of the IFIC, have led a study that has been published in the prestigious journal Physical Review Letters. The aim of this study is to understand the properties of antineutrinos emitted in nuclear fission reactors
Neutrinos are fundamental subatomic particles with an extremely small mass, close to zero and devoid of electric charge, which makes them invisible to electromagnetic fields. They are the second most abundant particles in the universe, generated in stars and cosmic explosions, and are able to pass through the Earth without being perceived. For this reason, they are known as "the phantom particle".
Each subatomic particle has its antiparticle, (which has the same mass and spin as its corresponding particle, but an electric charge and magnetic moment of opposite sign). Antineutrinos, the neutrino antiparticles, are emitted or produced during certain nuclear disintegrations. Within a nuclear reactor, unstable atomic nuclei are produced which disintegrate in various ways. One of the most common forms is called beta decay, in which the nucleus emits a beta particle (an electron) and an antineutrino.
Already in 2024, the Gamma and Neutron Spectroscopy group of the Institute of Corpuscular Physics (IFIC), located in the scientific-academic area of the University of Valencia Science Park (PCUV), together with scientific teams from France, England and Finland, They announced the development of a new detection system which aimed to clarify some of the discrepancies between theoretical models and observations recorded in the detection processes of neutrinos emitted in nuclear reactors. The key to understanding these discrepancies, they claimed, could be in measuring the beta spectra of fission products. Now, this new detection system has paid off and the group has published its results.
"These measurements are the first of their kind made with ultra-pure radioactive beams and allow us to better evaluate the corrections used for the calculation of the antineutrino spectrum of a reactor", Gustavo Alcalá, researcher at IFIC
The work has addressed measurements of the form of beta decay spectra which most contribute to the spectrum of antineutrinos from reactors using high purity radioactive beams produced at IGISOL, an internationally recognized Finnish experimental facility. It is very complex to detect the emitted neutrinos in order to analyse their energy, but it is possible to infer this by measuring the energy of the beta particle, since both are related by the principle of energy conservation. That is, you can measure the beta particles emitted in a reactor and study the antineutrinos through them.
With these results, Alejandro Algora and Gustavo Alcalá, have managed to correct the calculations of the antineutrino spectrum of reactors in a significant way, since the measures study «a type of beta transition which represents a high percentage of the total and therefore directly affects the region of the spectrum that is not understood», comments Alejandro Algora, principal investigator of the experimental proposal.
These measurements, says Alcalá, "are the first of their kind made with ultra-pure radioactive beams and allow us to better evaluate the corrections used for calculating the spectrum of antineutrinos in a reactor".
These measures could have major implications in the future: it could be determined whether there are illegal manipulations with reactor fuel by means of measurements of the antineutrino spectrum
Thanks to the large number of antineutrinos emitted per second by a reactor (approx. 1020), nuclear reactors have been of great relevance in the study of the properties of neutrinos, for example in studying their ability to transform from one type into another, a phenomenon known as the neutrino oscillation and, more importantly, for the first time they were able to demonstrate their existence directly.
It is now possible to monitor the power of a nuclear reactor using neutrino detectors. But these measures could have major implications in the future: it would be possible to determine whether there are illegal manipulations with reactor fuel by means of measurements of the antineutrino spectrum. In addition, it is believed that it will be possible to see through the neutrinos what is happening inside a nuclear reactor.
The work, carried out in the framework of an international collaboration (IFIC-Subatech-Univ. Surrey- Univ. de Jyväskylä- Univ. Warsaw) and led by the IFIC, is the first in a series of studies which will contribute to a better understanding of the anomalies that still persist in the physics of nuclear reactor neutrinos.
Source: IFIC
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