Geography
Ionising Radiation
Ionizing radiation refers to high-energy radiation that has enough energy to remove tightly bound electrons from atoms, creating charged particles (ions) in the process. This type of radiation includes alpha and beta particles, gamma rays, and X-rays. It is a natural part of the environment and can also be produced by human activities, with potential impacts on human health and the environment.
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11 Key excerpts on "Ionising Radiation"
eBook - ePub- U. Aswathanarayna(Author)
- 2018(Publication Date)
- Routledge(Publisher)
CHAPTER 7Natural radiation environment
7.1 IONIZING RADIATIONS
Ionizing radiations are capable of damaging biological tissues, with the nature of damage inflicted being related to the type, energy and penetrating power of the radiation involved. There are essentially two kinds of ionizing radiations: (1) electromagnetic radiations such as x-rays and gamma rays, and (2) corpuscular radiations, such as, alpha particles, beta particles (electrons), protons, neutrons, etc. Alpha particles are large particles, with energies of the order of millions of electron volts (MeV) and a range of 0.01 to 0.07 mm in soft tissues, and less in bone. Beta particles (electrons) are much smaller in size, have energies of the order of kilo electron volts (KeV), and have a range of several millimetres in soft tissues. X-rays and gamma rays are not stopped by tissues.The main natural sources of ionizing radiation in the environment are cosmic rays, and the decay of radioactive elements in rocks, soils, waters and atmosphere. So, wherever we live and whatever we eat and drink, we are being constantly and inexorably exposed to ionizing radiations all our lives. Normally, these radiation levels are so low as to have no ill effects on health. In normal circumstances, the exposure to man-made ionizing radiations is largely through medical examinations and treatment through X-rays. People and environment are occassionally exposed to high doses of man-made ionizing radiations through nuclear accidents (e.g. Three Mile Island reactor accident in USA or the Chernobyl disaster in Ukraine, in the former Soviet Union). Use of radon-bearing gas for cooking purposes, and the use of improperly shielded microwave ovens, etc. could also contribute to exposure to ionizing radations.7.1.1 Terminology of radiation units
The dose of radiation is the amount of energy absorbed per unit mass of material. One RAD (Radiation Absorbed Dose) is 10−2 Joules kg−1
eBook - PDF- John D. Cutnell, Kenneth W. Johnson, David Young, Shane Stadler(Authors)
- 2015(Publication Date)
- Wiley(Publisher)
32.1 | Biological Effects of Ionizing Radiation The physics of the biological effects of ionizing radiation. Ionizing radiation consists of photons and/or moving particles that have sufficient energy to knock an elec- tron out of an atom or molecule, thus forming an ion. The photons usually lie in the ultraviolet, X-ray, or g-ray regions of the electromagnetic spectrum (see Figure 24.9), whereas the moving particles can be the a and b particles emitted during radioactive decay. An energy of roughly 1 to 35 eV is needed to ionize an atom or molecule, and the particles and g rays emitted during nuclear disintegration often have energies of several million eV. Therefore, a single a particle, b particle, or g ray can ionize thou- sands of molecules. Nuclear radiation is potentially harmful to humans because the ionization it produces can significantly alter the structure of molecules within a living cell. The alterations can lead to the death of the cell and even of the organism itself. Despite the potential hazards, however, ionizing radiation is used in medicine for diagnostic and therapeutic purposes, such as locating bone fractures and treating cancer. The hazards can be minimized only if the fundamentals of radiation exposure, including dose units and the biological effects of radiation, are understood. Exposure is a measure of the ionization produced in air by X-rays or g rays, and it is defined in the following manner: A beam of X-rays or g rays is sent through a mass m of dry air at standard temperature and pressure (STP: 0 8C, 1 atm pressure). In passing through the air, the beam produces positive ions whose total charge is q. Exposure is defined as the total charge per unit mass of air: exposure 5 q/m. The SI unit for exposure is coulombs per kilogram (C/kg). However, the first radiation unit to be defined was the roentgen (R), and it is still used today.
eBook - ePub- Ben Selinger, Russell Barrow(Authors)
- 2017(Publication Date)
- CSIRO PUBLISHING(Publisher)
Chemistry of Ionising RadiationThis chapter starts with radiation basics, followed by the biological effects of radiation. External sources include NORM (naturally occurring radioactive materials) such as minerals in the garden, limestone caves, mineral beach sands and coal. Radioactivity in food and medical exposure are discussed. We toss in the dramatic story of a hyperactive, radioactive boy scout. The theory that low-level exposure might even have positive effects is not as outrageous as one might at first believe. Of the many applications of radioactive materials, a final example comes from the forensic investigation of art forgery.Radiation both causes cancer and is used to cure cancer. The sun’s rays keep us healthy but burn us, and worse. Radiation is a prime example of the conflict between the two faces of science/technology.Radiation is helpfully split into two categories: non-ionising and ionising, with some overlap. Electromagnetic radiation belongs (at moderate frequencies) to the non-ionising category. Its frequency ranges from radio waves, microwaves, infrared and visible light, all the way out to γ rays (which are, however, so powerful that they are ionising) (Fig. 18.1 ). All this radiation travels at the speed of light (3 × 10 8 m/s). Visible light covers only a very small section of this spectrum and comprises a stream of massless particles called photons.The energy of a photon depends on its wavelength (or frequency). The shorter the wavelength (or higher the frequency) of the radiation, the greater the energy of the photon. The physical and biological effect of a photon depends on its energy (Fig. 18.2 ).On the other hand, the quantity of radiation depends on the intensity (i.e. the number of photons). The very small proportion of ultraviolet radiation in sunlight can cause burning in 10 minutes, while you can spend weeks behind glass without getting a tan because it cuts out the UV, but lets through longer wavelengths.Fig. 18.1.
eBook - ePubThe Praeger Handbook of Environmental Health
[4 volumes]
- Robert H. Friis(Author)
- 2012(Publication Date)
- Praeger(Publisher)
22 Ionizing Radiation Arthur C. Upton Introduction Life has evolved in the continuous presence of ionizing radiation from natural sources, the existence and potential health effects of which were unknown prior to Roentgen’s discovery of the X-ray in 1895. Shortly thereafter, however, the X-ray was introduced rapidly into medical practice, and within weeks those working with the early radiation equipment began to report the occurrence of inflammatory reactions of the skin on their hands. In the ensuing years, various other types of radiation injuries were reported, including the first case of cancer attributed to ionizing radiation (see Table 22.1). During the century since then, study of the health effects of ionizing radiation has received continuing impetus from the expanding uses of radiation in medicine, science, industry, and the peaceful and military applications of atomic energy. The in-depth knowledge of the effects of ionizing radiation that has been gained as a result has been of strategic importance in the development of measures for protection against the harmful effects of radiation and other environmental agents. Physical Properties and Dosimetry of Ionizing Radiation Ionizing radiation differs from other forms of radiant energy in being able to deposit enough localized energy in atoms and molecules on which it impinges to break chemical bonds and give rise to ions and free radicals. The ionizing forms of radiation include (a) electromagnetic radiations of extremely short wave length and high energy (e.g., X-rays and gamma rays) (see Figure 22.1), and (b) particulate radiations, which vary in mass and charge (e.g., electrons, protons, neutrons, alpha particles, and other atomic particles). The distribution of such ionizing events along the path of the radiation in an absorbing medium—that is, the quality, or linear energy transfer (LET), of the radiation—varies with the energy and charge of the radiation, as well as the density of the absorbing medium
eBook - PDFEnvironmental Health
Third Edition
- Dade W. Moeller, D. W MOELLER(Authors)
- 2009(Publication Date)
- Harvard University Press(Publisher)
As it moves through space, electromagnetic radiation interacts with the atoms of which matter is composed. Only photons in the higher-energy ranges, such as cosmic rays, x rays, and gamma rays, have sufficient en-ergy to ionize these atoms by interacting with the orbital electrons and stripping them away. These are referred to as ionizing radiation. Electro- 296 e n v i r o n m e n t a l he a l t h Frequency Cycles/second (Hz) Energy Electron volts (eV) Radiation Cosmic rays X rays Gamma rays Ultraviolet Visible light Radar Television Nonionizing radiation Ionizing radiation Infrared Microwaves Radio waves Electric and magnetic fields 3 × 10 24 1.24 × 10 10 1.24 × 10 6 1.24 × 10 2 1.24 × 10 − 2 1.24 × 10 − 6 1.24 × 10 − 10 1.24 × 10 − 14 3 × 10 20 3 × 10 16 3 × 10 12 3 × 10 8 3 × 10 4 3 Figure 12.1 The electromagnetic spectrum magnetic radiation in the lower-energy ranges, such as the lower-frequency range of ultraviolet waves, as well as infrared waves, micro-waves, and radio waves, do not possess sufficient energy to be ionizing. These are referred to as nonionizing radiation. Once an electron is removed, it exhibits a unit negative charge, and the residual atom shows a net unit positive charge. The two products are known as an ion pair (Figure 12.2). This transfer of energy to atoms can result in chemical and biological changes that are harmful to health. e l e c t r o m a g n e t i c r a d i a t i o n 297 Incident photon Neutral atom Negatively charged electron Positively charged residual atom Figure 12.2 Interaction of an x or gamma photon with a neutron atom to produce an ion pair Nonionizing Radiation Although the biological effects of ionizing radiation have been recognized and reasonably well understood for some time, questions remain con-cerning the nature and effects of certain types of nonionizing radiation, in particular the photons associated with lower-energy electric and magnetic fields.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Learning Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 2 Ionizing Radiation Radiation hazard symbol. ________________________ WORLD TECHNOLOGIES ________________________ Ionizing radiation hazard symbol (recently introduced). Ionizing radiation consists of subatomic particles or electromagnetic waves energetic enough to detach electrons from atoms or molecules, thus ionizing them. The degree and nature of such ionization depends on the energy of the individual particles or waves, and not on their number. An intense flood of particles or waves will not cause ionization if these particles or waves do not carry enough energy to be ionizing. Roughly speaking, particles or photons with energies above a few electron volts (eV) are ionizing. Examples of ionizing particles are energetic alpha particles, beta particles, and neutrons. The ability of an electromagnetic wave (photons) to ionize an atom or molecule depends on its frequency. Radiation on the short-wavelength end of the electromagnetic spec-trum—high frequency ultraviolet, x-rays, and gamma rays—is ionizing. Lower-energy radiation such as visible light, microwaves, and radio waves are not. Ionizing radiation is ubiquitous in the environment, and also comes from radioactive materials, x-ray tubes, and particle accelerators. It is invisible and not directly detectable by human senses, so instruments such as Geiger counters are usually required to detect its presence. In some cases it may lead to secondary emission of visible light upon inte-raction with matter, as in Cherenkov radiation and radioluminescence. It has many ________________________ WORLD TECHNOLOGIES ________________________ practical uses in medicine, research, construction, and other areas, but presents a health hazard if used improperly. Exposure to radiation causes damage to living tissue, and high doses can result in Mutation, radiation sickness, cancer, and death.
eBook - PDF- David A. Wright, Pamela Welbourn(Authors)
- 2002(Publication Date)
- Cambridge University Press(Publisher)
This affects choices for methods of power generation as a whole, which is discussed in Sections 9.4.2 and 9.4.4. 8.2 Definitions 8.2.1 What is Ionising Radiation? When matter is subdivided, the molecule is the smallest amount that has the same properties as the original material. Molecules can be further subdivided into atoms, each type of atom being characteristic of an element. When atoms are divided, the constituents found are electrons, protons, and neutrons. These can be further broken down to yet smaller components, the nature of which is highly theoretical. The nucleus of an atom consists of positively charged protons and electrically neutral neutrons. Together they form the nucleon, which comprises 99% of the atomic mass of the atom. The nucleus is surrounded by a cloud of negatively charged electrons. Normally, the negative electrical charge associated with the elec-trons balances the positive charge on the protons. Atoms of the same element all have the same number of protons in the nucleus, but, within an element, the total number of neutrons may vary. Elements may, therefore, exist in two or more dif-ferent forms having slight differences in mass. These different forms are called iso-topes. For example, 99% of naturally occurring carbon in the environment ( 12 C) contains six neutrons and six protons in the nucleus. However, 1% of naturally occurring carbon ( 13 C) has an extra neutron in the nucleus. Both of these isotopes are stable, and, although they have virtually identical chemical properties (as deter-mined by their electron configuration), their slightly differing mass causes tiny but discernible differences in how they are partitioned in various components of the ecosystem. Isotopes of the same element may be differentiated analytically using a mass spectrometer (see Section 6.2.4). Many naturally occurring isotopes are unstable and may emit radiation as a result of their nuclear instability.
eBook - PDF- Walter Urbain(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
CHAPTER 1 Ionizing Radiation I. Radiation: Definition and Types 1 II. Ionization and Excitation 3 III. Radiations for Treating Foods 4 IV. Interaction of Ionizing Radiation with Matter 6 A. General 6 B. Electron Radiation 6 C. Electromagnetic Radiation 8 D. Role of Elemental Composition of Absorber 10 E. Quantitative Relationships in Energy Transfer 11 F. Induced Radioactivity 19 Sources of Additional Information 22 I. RADIATION: DEFINITION AND TYPES Food irradiation employs an energy form termed ionizing radiation. The particular attributes of ionizing radiation that make it useful for treating foods are several in number. Certain kinds of ionizing radiation have the ability to penetrate into the depth of a food. Through physical effects they interact with the atoms and molecules that make up the food and also those of food contaminants such as bacteria, molds, yeasts, parasites, and insects, causing chemical and biological consequences which can be utilized in beneficial ways. While ionizing radiation frequently is referred to as high-energy radiation, the total quantity of energy needed to secure the beneficial effects with foods is relatively small, and gross changes in a food which could affect its acceptability usually do not occur. The term ionizing radiation includes a number of different kinds of radia-tion. Not all the radiations classified as ionizing radiation have properties suitable for use in food irradiation, and, as a consequence, restrictions defining what kinds are satisfactory are required. The propagation of energy through space is termed radiation or radiant energy. There are two basic types of radiation: (1) electromagnetic and (2) corpuscular. Electromagnetic radiation consists of self-propagating electric and magnetic disturbances. Conceptually it can be considered to be a wave motion involving oscillating electric and magnetic field vectors. It is characterized by two 1 2 1. IONIZING RADIATION parameters inversely related to each other: 1.
- Edward W. Finucane(Author)
- 2023(Publication Date)
- CRC Press(Publisher)
Ionizations produced by this class of electromagnetic radiation can occur either “directly” or “indirectly”. “Directly” ionizing radiation includes:- electrically charged particles (i.e., electrons, positrons, protons, α-particles, etc.), and
- photons/particles of sufficiently great kinetic energy that produce ionizations by colliding with atoms and/or molecules present in the matter.
- liberating one or more “directly” ionizing particles from matter with which these particles have interacted or are penetrating, or
- initiating some sort of nuclear transition or transformation (i.e., radioactive decay, fission, etc.) as a result of their interaction with the matter through which these particles are passing.
Protection from the adverse effects of exposure to various types of Ionizing Radiation is an issue of considerable concern to the occupational safety and health professional. Certain types of this class of radiation can be very penetrating (i.e., γ-rays, X-rays, and neutrons); that is to say these particles will typically require very substantial shielding in order to ensure the safety of workers who might otherwise become exposed. In contrast to these very penetrating forms of Ionizing Radiation, α- and β-particles are far less penetrating, and therefore require much less shielding.Categories of Ionizing Radiation
Cosmic Radiation
Cosmic Radiation (cosmic rays) makes up the most energetic — therefore, potentially the most hazardous — form of Ionizing Radiation. Cosmic Radiation consists primarily of high speed, very high energy protons (protons with velocities approaching the speed of light) — many or even most with energies in the billions or even trillions of electron volts. These particles originate at various locations throughout space, eventually arriving on the earth after traveling great distances from their “birthplaces”. Cataclysmic events, or in fact any event in the universe that liberates large amounts of energy (i.e., supernovae, quasars, etc.), will be sources of Cosmic Radiation
eBook - PDFBiological Aspects of Freshwater Pollution
Proceedings of the Course Held at the Joint Research Centre of the Commission of the European Communities, Ispra, Italy, 5-9 June 1978
- O. Ravera(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
This means that, below a certain thres-hold, ionizing radiations are not able to damage organisms. According to certain authors, the^spontaneous mutations are produced by ionizing radiations and, consequently, they should be the cause of biological evolution. The natural dose-rate measured in different areas of the Earth is very different according to their lithological, geographical and ecological characteristics (Table 2). The hazard of high doses of ionizing radiations was well known even 179 180 Ο. Ravera Source Dose (mR) Cosmic rays 24 Soil and rocks radioactivity 36 -57 Radon in the air 1 in the body 21 ^^C in the body 1 Radon and decay products in the body 2 Fall-out contamination is extended to the whole biosphere, whereas radioactive discharges always concern small areas. For the present low level of fall-out radioactivity, the principal problem seems to be the wastes produced by nuclear installations for the production of electric power. The importance of these wastes will increase with the future development of nuclear power industry. For exam-ple, and ^^Κτ, discharged by nuclear plants, may become, in the near future, an important problem of radioprotection. Unfortunately, there is inadequate in-before the Second World War, but the consequences of the nuclear explosions in Japan during this war, have made the public afraid of radiation effects and radio-active pollution (Table 3). Actually, the use of the atomic bomb in 1945 and the following 336 nuclear tests have caused a sudden increase in the natural level of radioactivity, particularly in northern temperate latitudes. This increase, for the fall-out contamination, was worldwide and all foodchains, man included, were contaminated. It has been calculated that the mean dose due to fall-out absorbed by a man living in a tem-perate zone was equal to about 2.4% of the total dose due to the natural level of radioactivity (Table 4).
- Charles D. Reese(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
Workers many not even know that they have a potential for exposure to hazardous chemicals, and hazardous chemicals may be considered just an acceptable part of working. It is possible to maintain a lifetime dose for individuals exposed to radiation. Most workers wear a personal dosimeter, which provides levels of exposure. The same is impossible for chemicals where no standard unit of measurement such as the rem (roentgen equivalent man) exists for chemicals. The health effects of speci fi c doses are well known such as 20 – 50 rem — minor changes 252 Industrial Safety and Health for People-Oriented Services in blood occur, 60 – 120 rem — vomiting occurs but no long-term illness, or 5,000 – 10,000 rem — certain death within 48 h. Ionizing radiation is radiation that has suf fi cient energy to remove electrons from atoms. One source of ionizing radiation (IR) is the nuclei of unstable atoms. For these radioactive atoms (also referred to as radionuclides or radioisotopes) to become more stable, the nuclei eject or emit subatomic particles and high-energy photons (gamma rays). This process is called radioactive decay. Unstable isotopes of radium, radon, uranium, and thorium, for example, exist naturally. Others are continually made naturally or by human activities such as the splitting of atoms in a nuclear reactor. Either way, they release ionizing radiation. The major types of IR emitted as a result of spontaneous decay are alpha and beta particles and gamma rays. X-rays, another major type of IR, arise from processes outside of the nucleus. Neutrons are also a form of IR that is present around nuclear reactors. 17.2 TYPES OF RADIATION The four basic types of ionizing radiation of concern in most radiological work situations are alpha particles, beta particles, gamma rays, and neutron particles. These may exist in various amounts, depending on the exact location and nature of the work.
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