Vol. 4 No. 1 (2023): Suplemento de la Revista Mexicana de Física. Proceedings of the 16th International Symposium on Radiation Physics

Preface.

Proceedings of the 16th International Symposium on Radiation Physics 

The Fricke dosimeter is a widely used gamma radiation dosimetry system. The system is based on the detection of Fe²⁺ to Fe³⁺ oxidation in an aqueous solution of ferrous sulfate in sulfuric acid, exposed to ionizing radiation in the presence of oxygen. The system is formed by a series of highly dependent chemical reactions. We developed a numerical model of coupled differential equations based on the mass balance; each equation incorporates information about the formation and breakdown of each molecule, as well as a term that represents an external source of radiation. The numerical model can reproduce the behavior of the experimental data at room temperature. We proposed a correction factor to simulate the behavior of the dosimeter at temperatures of 198 K and 77 K, respectively, when the system is in a thermal bath of dry ice or liquid nitrogen. This model could support a variety of experimental challenges for radiation at low temperatures in different fields of industry and could have relevance for astrobiology problems by offering the possibility of simulating reactions in comets and other exoplanetary bodies.

The past seven decades the design and structural material of nuclear installations has improved and their safety precludes the possibility of severe accidents in GEN-III and III⁺ nuclear power plants (NPP). Zaporizhzhya GEN-III⁺-NPP (Ukraine), is used as subject of discussion. This NPP suffered a military attack this 2022. We discuss the possibility of a severe nuclear accident and the release of radioactive material, as a consequence of an adverse structural damage. Clearly, damage to a GEN-II, -III⁺ reactor dome by military ordnance can only be estimated from data gained during past nuclear accidents in a war zone, or in the neighborhood of military targets. We report historical experiences of reactors in a war zone or under direct military attack. Based on the available data we will discuss possible scenarios applicable to a nuclear installation in Ukraine. The concrete containment of buildings protecting the nuclear vessel and its LEU-fuel loaded core, are not designed to withstand military attacks. We will discuss possible consequences of a severe structural damage due to weaponry. Estimations will be made considering the VVER-1000 Zaporizhzhya ZNPP, class GEN-III⁺ built near the city of Enerhodar, Ukraine. This reactor has a 2m-plus-steel-reinforced containment. It is also discussed that spent-fuel temporal reservoirs in war zones, are higher-risk structures with higher likelihood of severe radioactive material release than NPP reactors.

Adverse effects of long-term exposure to galactic cosmic radiation (GCR) pose a clear obstacle to future space exploration programs. In addition to GCR we have solar particle radiation. We simulated the latter using a scaled fluence profile of solar protons taken from a literature study that comprises about three solar cycles. The model is a three-layer stack that includes shielding material and muscular tissue. Our simulation strategy uses protons as precursor radiation of neutrons. Subsequently, the shield is adjusted for thickness, dictated by an average depth at which neutrons are created through various processes during the simulation. Neutrons are then energy-binned and a corresponding neutron flux is simulated. Particles generated during the second phase of the simulation, i.e. by neutrons, are then counted toward absorbed dose within the muscular tissue layer. Clearly, the dynamics of the process is not captured by the simulation, nevertheless an overview of neutron yield can be estimated and the absorbed dose. The objective is to provide some insight about the effect of the new composite shield, PMMA-Bi2O3, that has an intrinsic capability for gamma dose reduction, compared to a more traditional aluminum shield.

In this work we present a classroom alternative to simulate radioactive decay of nuclei. It consists of a game in which the students in a classroom are invited to participate in a kind of lottery. The students (around 45 in a typical classroom) take 20 “tickets” numbered at random from 1 to 50. As a whole we have 900 initial “tickets”. Then one student is asked to give a random number between 1 and 50 (for example 34) and the teacher gives a range of numbers from 34 to 38 or 30 to 34. The students cross the numbers in their list that coincide with the numbers given by the teacher. These numbers are the “lucky” ones and represent “nuclei” which decay, then someone gives another number and the process is repeated and the number of “lucky” tickets put in a list. Repetition of the process gives a sequence of numbers which are the number of “nuclei” surviving
as the time goes on. The nuclei decaying are considered as stable ones. A plot of the surviving “nuclei” as a function of time (number of times the students are asked to cross the lucky numbers) gives a typical exponential decay. When one considers the case of nuclei A decaying into nuclei B decaying to nuclei C and this one is a stable one, using the corresponding differential equations one obtains the normal curves of nuclei as a function of time.

This work presents a novel method for mitigating indoor radon, which consists of four steps:  a) nucleation of water vapor around Rn atoms and Rn progenies, b) condensation of the mentioned clusters favored by a Peltier cooling process, c) accumulation of the resulting liquid, and d) discharging of the liquid outside. This system was proved in an underground cave with microclimate conditions (80 % relative humidity, 798-800 mbar atmospheric pressure, 20 ± 1 ⁰C temperature, and an almost constant indoor Rn activity of  890 Bq/m³), in México City. The proposed method takes advantage of the natural formation of a system of Radon-Water (Rn-H₂O) complexes, by van der Waals interactions. We have observed that by reducing the relative humidity by Peltier cooling, from 80 to 52%, a removal of radon is produced, from 607 to 165 Bq/m³, which is a very remarkable mitigation effect. Experimentally, the operation of the mitigation system in relative humidity environments between 30 and 80%, and between 40 and 1500 Bq/m³, is certified, always obtaining control of the desired intramural radon activity (100 Bq/m³), in less than 12 hours. This surpasses most of today’s commercial radon mitigation methods in efficiency, cost, time and ease, specifically in conditions where ventilation is not a reliable option.

This study presents a method for the identification of a set of radioactive sources of 60Co, in an industrial irradiator. This identification was requested by a Mexican regulatory authority. To fulfill this request, a method was developed to make the identification by the gamma spectrometry method. The complexity in the measurement lies in the fact that the set of sources has an activity of 500,000 Ci of 60Co and the identification is complicated because with that gamma intensity one has to have a strategy to reduce the phenomena of saturation, pile up and dead time and achieve that photopeaks generated in the gamma spectrum of the gamma energies of 60Co are clearly visible.
A low efficiency and relatively high resolution CZTe detector, was selected, which was placed in an acrylic box with a collimated lead shield to carry out the measurement inside the irradiator pool to reduce scattered radiation and to be able to clearly appreciate the spectrum gamma of 60Co.

The study of the interaction of gamma radiation with relevant elements on our planet is important for escearth sciences to understand current phenomena that the Earth is experiencing and to suggest solutions such as the removal of dyes from wastewater. The goal of this work is to show the importance of research results in which the interaction of gamma radiation with organic compounds gives clues to solving current problems by making use of gamma radiation interaction with matter. Our results show that gamma irradiation could be an alternative to the removal of emerging contaminants, a topic of current relevance.

We assume that the neutrino mass matrix Mν, in the model-independent context, is diagonalized by the Tri-Bi-Maximal (TBM) pattern. In the following, we explore the TBM mixing pattern deviation by considering different textures for the charged lepton matrix, which are classified into equivalence classes that allow us to reproduce the experimental data on neutrino oscillation. Our target is on the charged lepton matrix with the minimum number of free parameters, i.e., the maximum number of zeros of the texture that allows us to correctly reproduce the value of the reactor mixing angle θ13. We show a deviation from the TBM pattern in terms of the charged leptonic masses, which provides a prediction value for the phase factors in the charged lepton mass matrices. These are related to the “Dirac-like” CP and “Majorana-like” phase factors. For the last type of phase, we show its phenomenological implications through effective Majorana mass in the neutrinoless double-beta decay.