Preface

Nuclear physics is the study of the properties of atomic nuclei. Its aim is to understand the properties of nucleons and the mechanisms of nuclear reactions (spontaneous and induced), with a view to describing the various processes of elastic and inelastic nucleus–nucleus interactions.

Radionuclides are useful in many areas of everyday life: archaeology, biology, agronomy, medicine, industry, etc. Among the most spectacular are applications in radiochronometry (dating of archaeological objects, sediments and soils for the detection of anthropogenic pollutants, etc.) and nuclear medicine (radiopharmaceuticals used in nuclear medicine imaging, radiotherapy, etc.). The production of electrical energy in nuclear power plants exploits the properties of nuclear fission reactions. In addition, the study of nuclear physics enables us to understand many astrophysical phenomena, such as nucleosynthesis processes (primordial, stellar, explosive) within the framework of the Big Bang model. The study of these processes allows understanding of the origin of chemical elements and how to model the evolution of stars from their birth to their explosive end, for example, in supernovae and neutron stars [SAK 22].

This book, entitled Nuclear Physics 2: Radiochronometers and Radiopharmaceuticals, is divided into four chapters.

Chapter 1 is devoted to a description of the Big Bang model, enabling us to understand the origin of all known chemical elements from nucleosynthesis reactions. The chapter begins with a presentation of Christian Doppler’s (1804–1853) theory, which led to his hypothesis of the physical phenomenon known as the Doppler effect in the case of sound waves. This is followed by a description of Christoph Buys-Ballot’s (1817–1890) historic experiment confirming the Doppler effect. The study then turns to Armand Hippolyte Fizeau’s (1819–1896) theory of the Doppler effect as it applies to light waves. This study establishes the formula for the Doppler–Fizeau effect, based on the transformation laws of the wave quadrivector. This is followed by a study of the longitudinal and transverse Doppler effects in the classical approximation for weakly relativistic motions, and the derivation of the Doppler–Fizeau formula used to interpret the redshift phenomenon of light sources in relative motion, and to calculate the radial velocity of a star or galaxy. In addition, the link between the sign of the Doppler shift and the relative motion of a light source is studied in the classical approximation, to highlight the phenomenon of redshift in the spectrum of stars and galaxies in particular. Following these developments, the principle of redshift measurement is illustrated schematically using the spectrum of the galaxy named NGC 3627 (NGC: New General Catalogue). Following this study of the redshift interpreted by the Doppler–Fizeau effect, the chapter then turns to the theoretical and experimental facts that have validated the Big Bang model. These range from the observation of the redshift to the discovery of the cosmic microwave background (CMB). This historical overview begins with the first observations of the redshift phenomenon in the spectral lines of galaxies by de Vesto Melvin Slipher (1875–1969). This is followed by the work of Alexander Friedmann (1888–1925), who first published a theory of the expansion of the universe. The work of Georges Lemaître (1894–1966), linking the expansion of the universe with observations of the escape velocity of extragalactic nebulae, and his formulation of the “primitive atom” hypothesis to explain the origin of the universe by introducing the notion of instant zero, figure prominently in this historical review. The presentation of this work is followed by Edwin Hubble’s (1889–1953) decisive observations showing that the variation of velocity with distance is linear, a relationship known as the Lemaitre–Hubble law. Various attempts to estimate the Hubble constant denoted H0 are then discussed. The discovery of the cosmic microwave background, the decisive argument in favor of the Big Bang theory, ends this historical review. This is followed by a brief description of the chronology of the universe’s evolution after the Big Bang. The various eras that characterize the chronology of the universe are studied: the Planck era, the era of grand unification, the era of inflation, the era of baryogenesis and primordial nucleosynthesis, the era of quark–gluon plasma formation, the era of nucleosynthesis, the dark age of the universe, designating the era beginning with radiation–matter decoupling, the radiative era and finally the era of star and galaxy formation. The chapter is interspersed with corrected application exercises.

Chapter 2 is reserved for the study of the various nucleosynthesis processes that began almost 1 second after the Big Bang and lasted approximately 3 minutes. The chapter begins with an overview of the concept of chemical elements, of which there are 118 known, 90 of which occur naturally on Earth. This is followed by a detailed study of the processes of primordial, stellar and explosive nucleosynthesis. The study of primordial nucleosynthesis describes the formation of light elements such as hydrogen, deuterium, helium-3, helium-4, lithium-6 and lithium-7 in the first instants of the universe. The study of stellar nucleosynthesis enables us to understand the origin of carbon-12, oxygen-16, neon-20, sodium-23, magnesium-24, silicon-28 and 30, sulfur-31 and phosphorus-30 and 31, as well as that of all nuclei up to iron-56. We then study the formation of all elements heavier than iron and isotopes synthesized via the s (slow) and r (rapid) processes during explosive nucleosynthesis. This study enables us to describe the “slow” neutron capture process via the s process, as well as the rapid process of radiative neutron capture followed by decay, which provides about half the abundance of elements beyond iron up to uranium. This chapter also covers the spallation process, corresponding to the formation or destruction of large nuclei by very high-energy particles (such as the nucleosynthesis of Li, Be and B in the interstellar medium), and the photodisintegration process, which reflects the destruction of nuclei by photons. The study then focuses on the description of important nucleus-forming processes, such as the triple-alpha reaction, a set of nuclear fusion reactions simultaneously transforming three α particles (helium-4 nuclei) into carbon-12 nuclei via the unstable beryllium-8 nucleus. We also look at the formation of compound nuclei, in particular, the 14N (p, γ) 15O reaction involved in the CNO (Carbon–Nitrogen–Oxygen) or the Bethe–Weizsäcker cycle studied in astrophysics. Finally, the chapter focuses on the classification of natural and artificial radionuclides in the environment. The chapter is also interspersed with corrected application exercises.

Chapter 3 is dedicated to the study of radiochronometers applied to dating. It begins with a study of the principle of carbon-14 dating. This introduces the notions of cosmogenic isotopes, cosmic radiation and calendar age. It introduces the notions of the “Bomb” effect and the “Suess” effect, which contribute to modifying the concentration of radiocarbon in the atmosphere. It also introduces the notion of the reservoir effect, reflecting the fact that oceanic and atmospheric concentrations of radioactive 14C are not homogeneous. Next, the study focuses on the principle of potassium–argon (K–Ar) dating. This method establishes the age equation of a volcanic eruption, only taking into account the 40Ar resulting from the decay of the 40K present in the lava (this argon 40 is often referred to as 40Ar*). Next, the age equation is corrected to take account of the 40Ar atmosphere, so that the results obtained with the K–Ar clock can be properly used. This is followed by a description of the principle of dating soils or sediments using the radiochronometers lead-210, cesium-137 and beryllium-7. A description of the principle of lead-210 dating explains the origins of supported lead-210 (210Pbsup) and excess lead-210 (210Pbex) in sediments. Next, the CFCS (Constant Flux and Constant Sedimentation), CRS (Constant Rate of Supply) and CIC (Constant Initial Concentration) models are described, enabling the age of a sediment to be determined experimentally. This chapter features a study of the atmospheric nuclear tests carried out between 1945 and 1980, and of the Chernobyl accident in 1986, the second largest source of cesium-137 in the atmosphere. This is followed by a description of the principle of 137Cs radiochronometer dating. This involves taking core samples from the sediment in question and interpreting the 137Cs activity profile, according to the sampling date. This is followed by a description of the principle of dating using the cosmonuclide 7Be, formed in the troposphere by nuclear spallation. The chapter concludes with a description of the principle of dating using the uranium–thorium radiochronometer to determine the age of certain carbonate formations of animal or sedimentary origin, and the principle of dating using the uranium–thorium and uranium–protactinium radiochronometers for coral dating. As in previous chapters, corrected application exercises are provided at various points in the chapter.

Chapter 4 is devoted to general information on radiopharmaceuticals...