Radionuclide Sources
Michael Pöschl, Leo M. L. Nollet in Radionuclide Concentrations in Food and the Environment, 2006
The uranium isotopes are all radioactive, and their decay produces a number of secondary radioactive elements that continue to decay until they reach stable nuclei. This decay chain of radionuclides is commonly referred to as the uranium decay series. Similarly thorium, another primordial isotope with a long half-life, also has a decay series that leads to the formation of numerous naturally occurring secondary radionuclides. Thus the key primordial radionuclides of uranium and thorium decay to many other radioactive isotopes that occur in the environment at different levels of abundance, depending on their own decay rates and those of their parents. Figure 2.1 and Figure 2.2 show the decay schemes for primordial 238U and 232Th, respectively. Figure 2.3 shows the decay processes for 235U. Only the major pathways are shown in these figures, with the significant γ emitters highlighted in bold type. More detailed information on the isotopic decay processes, including minor pathways, can be obtained from the Table of Isotopes [5–7].
Biokinetic Models
Shaheen A. Dewji, Nolan E. Hertel in Advanced Radiation Protection Dosimetry, 2019
Radioactive decay results in emission of radiation and transformation of an atom, called the parent, into a different type of atom, called the progeny or daughter radionuclide. The progeny radionuclide may also be radioactive, in which case it will also eventually decay and emit radiation. This leads to a sequence of different radionuclides and decay events, eventually producing a stable nuclide. The parent radionuclide together with the sequential set of radionuclides produced by this process is called a decay chain. The members of a decay chain excluding the original parent radionuclide are referred to collectively as the radioactive progeny of that parent radionuclide.
Kill or Cure
Alan Perkins in Life and Death Rays, 2021
Radioactive materials are described as being unstable and have the natural ability to change the configuration of the particles in the nucleus of their atoms. As described in Chapter 2, the atomic nucleus of all elements contains two fundamental types of particles known as protons and the neutron. The protons have a positive electrical charge and will force each other apart (in the same way that the same poles of a magnet repel each other) if it were not for the presence of the neutrons which are neutral, i.e. have no charge. The neutrons therefore weaken the repulsive force of the protons allowing the nucleus to remain stable. For most stable atoms the number of protons is more or less equal to the number of neutrons. However, if the number of protons and neutrons diverge the atom is more unstable and will correct the imbalance by a process known as radioactive decay. If the atom has too many protons (proton excess) a proton will be converted to a neutron, whereas if there are too many neutrons a neutron is converted into a proton. These nuclear processes take place to allow a more stable balance of protons and neutrons and may be repeated through a number of transformations known as a decay chain. A fundamental feature of these transformations is that the conversion of protons into neutrons and neutrons into protons also releases other forms of energy from the nucleus. This energy is mainly in the form of radiation and is mainly of three types: alpha, beta and gamma. In some situation neutrons may be emitted, but this is mostly associated with nuclear fission or fusion reactions and alpha particles can cause neutrons to be emitted when they interact with the atoms in other materials.
Chromosome aberrations, micronucleus frequency, and catalase concentration in a population chronically exposed to high levels of radon
Published in International Journal of Radiation Biology, 2023
Dwi Ramadhani, Sofiati Purnami, Devita Tetriana, Irawan Sugoro, Viria Agesti Suvifan, Nastiti Rahadjeng, Septelia Inawati Wanandi, Heri Wibowo, Ikuo Kashiwakura, Tomisato Miura, Mukh Syaifudin
More than 60% of the total ionizing radiation a person gets each year can be attributed to natural sources; radon and its breakdown products account for more than 50% of these natural sources of radiation (Sinitsky and Druzhinin 2014). Radon, an odorless and colorless radioactive gas, is produced during the series of transformations in the uranium (U-238) decay chain. Specifically, radon (Rn-222) is the direct decay product of radium (Ra-226). As the decay chain continues, alpha (α) and beta (β) radioactive isotopes are produced. Alpha particles, have the ability to ionize and damage biomolecules in living cells (Walczak et al. 2019; Grzywa-Celińska et al. 2020). Ionizing radiation in the form of alpha particles can cause DNA damage, leading to double-strand DNA breaks and chromosomal aberrations (CA) (Robertson et al. 2013; Yanxiao et al. 2019). This type of radiation can also elicit damage to biomolecules (e.g. DNA, proteins, and lipids) indirectly by inducing the generation of reactive oxygen species (ROS). Several oxidant molecules are classified as ROS, including free radicals, such as superoxide (O2•–) and hydroxyl (OH•) radicals, and non-radical species, such as singlet oxygen (1O2) and hydrogen peroxide (H2O2). These highly reactive species are controlled by different mechanisms in the human body. One of them is the action of enzymatic antioxidants, such as superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) (Kuciel-Lewandowska et al. 2018).
Radiological risk assessment of the Hunters Point Naval Shipyard (HPNS)
Published in Critical Reviews in Toxicology, 2022
Dennis J. Paustenbach, Robert D. Gibbons
U-235 has a radioactive half-life of 7 × 108 years and is a naturally occurring radionuclide. U-235 accounts for 0.72 wt% of natural uranium with the remaining fractions consisting of U-238 at 99.27 wt% and U-234 at 0.006 wt%. Natural uranium is present in low amounts in rocks, soil, water, plants, and animals. Uranium and its decay products contribute to low levels of natural background radiation in the environment. U-235 transitions by alpha decay. Its decay products emit alpha, beta, and gamma radiation in various combinations depending upon which decay product of the U-235 decay series is evaluated. U-235 is primarily an internal radiation hazard if ingested or inhaled (ICRP 2008; Johnson et al. 2012). Studies of the chemical and physical characteristics of U-235 were carried out at HPNS due to its important role in nuclear fuel (USN 2004). Such studies included the chemical separation of U-235 samples irradiated at Lawrence Livermore National Laboratory, and animal research was also conducted to evaluate potential health effects from exposure to U-235, particularly highly enriched uranium in U-235. The potential for the presence of U-235 contamination at on-site laboratories was a primary reason it was identified as an ROC at HPNS (USN 2004). U-238 was not included as an ROC since results of the site investigations did not identify concentrations above risk screening criteria used by the USEPA and the Navy, and the majority of sampling results during site investigations were not statistically different from background.
Peptide receptor radionuclide therapy in neuroendocrine neoplasms and related tumors: from fundamentals to personalization and the newer experimental approaches
Published in Expert Review of Precision Medicine and Drug Development, 2023
3. Actinium-225 (225Ac): 225Ac has grown popular in recent years because of the advantage of being an α particle emitter, which is a high linear energy transfer (LET) radiation compared to the beta-emitters and has an energy of 5.93 MeV. Its role has been emphasized in patients with advanced cases which were resistant even to 177Lu, wherein its efficacy and safety profile have been observed [17]. Interestingly, these radionuclides have lesser tissue penetration range and thereby saves surrounding non-target organs from being irradiated with unwanted irradiation. They also have a better radiation safety profile. With 10 days half-life and multiple emissions like β −, γ rays in lower abundance it is quite suitable for use in therapeutic seating. Researchers are looking forward to observing the results and whether it will improve the outcome of PRRT in metastatic/advanced NETs. Similar to 90Y, there are issues regarding production and availability 225Ac, as it is available in limited quantities by radiochemical separation from two 229Th sources, one located at Oak Ridge National Laboratory (ORNL), U.S.A, and the other at the Institute for Transuranium Elements in Karlsruhe, Germany. There have been also a few issues regarding the chemical stability of intermediate species of the decay chain of 225Ac with chelators which are under research (sumarrized in Table 2).
Related Knowledge Centers
- Alpha Decay
- Beta Decay
- Exponential Distribution
- Radioactive Decay
- Radionuclide
- Thorium
- Half-Life
- Radon
- Bateman Equation
- Positron Emission