ReginaPintodeCarvalho APPLICATIONSOF NUCLEARENERGY
INDUSTRY•ENVIRONMENT FOODPRODUCTION•CULTURALHERITAGE
Regina Pinto de Carvalho
APPLICATIONS OF NUCLEAR ENERGY
Industry • Environment Food production • Cultural heritage Published by International Atomic Energy Agency - IAEA Vienna International Centre PO Box 100 / 1400 Vienna, Austria www.iaea.org
Technical revision Ana Márcia Greco de Sousa
Ilustration Henrique Cupertino
Lay-out Christiane Morais
Translation Custom Solutions Ltda.
Support International Atomic Energy Agency - IAEA Sociedade Brasileira de Física – SBF Comissão Nacional de Energia Nuclear – CNEN Sociedade Brasileira para o Progresso da Ciência - SBPC CHAPTER I - FUNDAMENTALS 9 Composition of the nucleus 9 Nuclear reactions 10 Radioactive decay 11 Obtaining radioelements 12 Obtaining ionizing radiation beams 13 Interaction of radiation with matter 14 Detection of ionizing radiation 15
CHAPTER II - STABLE ISOTOPES 17 Water isotopes 17 Stable isotopes in organic material 18 Measurement of isotopic variations 19 Mass Spectrometer 19 Laser Absorption Spectroscopy 20 Applications 21 Oxygen isotopes 21 Information on surface and groundwater 21 Carbon Isotopes 22 Origin of carbon in the atmosphere 22 Origin of carbon in the oceans 24 Nitrogen and sulfur isotopes 24
CHAPTER III - APPLICATION OF NUCLEAR ENERGY IN INDUSTRY 25 Radiotracers 25 Radiotracers in the oil industry 25 Gaseous flows 27 Nucleonic control systems 28 Neutron backscattering 29 PGNAA 30 γ Scanning 32 Dual-energy Gamma Radiation Analysis 32 Non-destructive tests 33 X-rays and γ-scans 33 Other applications of ionizing radiation 34
CHAPTER IV - ENVIRONMENTAL STUDIES 35 Radioactive tracers 35 Use of gold as a radiotracer 35 Technetium-99m used as a radiotracer 37 Tritium as a radioactive tracer in landfills 38 Tracer activation 39 Radiotracers for soil studies 40 Use of sealed sources 41 γ Transmission Analysis 41 γ Backscattering 41 Meteorological studies 42
CHAPTER V - APPLICATIONS OF NUCLEAR ENERGY IN FOOD PRODUCTION 45 Soil studies 45 Induced mutation 46 Sterile insect technique 48 Food irradiation 52 Livestock 53
CHAPTER VI – STUDY AND PRESERVATION OF CULTURAL HERITAGE 55 Dating with carbon-14 55 Muography 56
READING SUGGESTIONS 59 In general, people are mostly unaware of the peaceful applications of nuclear energy. Lending continuity to the project initiated in our previous book, “Applications of Nuclear Energy in Health”, the objective of this second book is to provide information and examples of the use of nuclear energy in areas as diverse as industry, environmental studies, food production and preservation of cultural assets. We thus hope to provide high school teachers with useful bibliography on the subject, at an appropriate level, to complement classroom activities. A brief introduction outlines the fundamentals of Nuclear Physics, followed by chapters on applications in various areas. These stand-alone chapters can be read in any order. To allow this, we have chosen to repeat, in some chapters, information we deem essential, in order to assure its understanding. The illustrations are presented so they can be understood by colorblind people. If you, dear reader, have this characteristic and find it difficult to interpret some figures, please contact us so that we can make the necessary improvements.
We would like to thank the many experts from all over the world who have dedicated time to talking to us and/or reading the material, sending information and references. To the extent possible, they are mentioned at the end of each chapter. In particular, we thank Prof. João Alberto Osso Júnior (IAEA) for his comments and observations. We also thank him for handling the operational part of the Project. We thank Drs. Jesus Carrillo-Castillo and Raul Ramirez (IAEA) for supporting the Project. In addition, we wish to express our deepest appreciation to Prof. Aldo Malavasi (IAEA), who embraced the project and allowed it to grow much beyond what we had initially imagined.
Regina January/2019
(...) and we shouldn´t forget that the structure of the atom cannot be seen with our eyes but we know it´s there. I know about many things that I have not [actually] seen. As have you...
Clarice Lispector - translated from A Hora da Estrela
7
CHAPTER I - FUNDAMENTALS
We can describe an atom as having a positive nucleus and negative electrons, located in a region around the nucleus. The volume of the atom is determined by the so- called “electronic cloud” and its mass is mainly related to the mass of the nucleus. The transformations of nuclei through bombardment and emissions are the object of the study of Nuclear Physics. This chapter presents a summary of the fundamentals of Nuclear Physics that will be necessary for the understanding of later chapters.1 Composition of the nucleus The particles that make up the nucleus are called nucleons. They may be positive (the protons) or have no electric charge (the neutrons). There are forces of attraction between the nucleons, which need to compensate for the electric repulsion forces between the protons, so that the nucleus remains cohesive. The chemical elements are distinguished from each other by the number of protons in their nuclei (equal to the number of electrons, if the atom is neutral). They may have diff erent numbers of neutrons, maintaining the same chemical properties, but having diff erent masses. Atoms of the same element with diff erent numbers of neutrons are called isotopes. Most elements have natural isotopes. Many natural isotopes are stable; others, unstable, decay by undergoing radioactive emissions. The nuclei are represented by the symbol of the element to which they correspond; a subscript on the lower left of the symbol represents its atomic number (number of protons), and a superscript on the upper left of the symbol represents its mass number (number of protons + number of neutrons). If a nucleus is in an excited state, this is specifi ed by an asterisk to the right of the symbol. The example below shows the representation of a uranium-256 nucleus (92 protons, 164 neutrons) in an excited state:
U i-1 256 ∗ 92 1 For a more detailed development of thePu subject, the readerU + can turn to the fi rst chapters of the previous book: “Applications of Nuclear Energy in Health”238 (RP de234 Carvalho 4and SM Velasques de Oliveira), SBPC-IAEA (2017), 94 92 2 available at:
1� N2
2 1 N N = 2 2 4
∙ It is not necessary to write the number of protons, since that is determined by the symbol of the element; however, it may be useful to display this number to facilitate the visualization of nuclear processes. Nuclear reactions A nucleus can be modifi ed by spontaneous emission, absorption or bombardment of particles, photons or other nuclei. When a nucleus is not in equilibrium, it can decay, emitting particles or radiation, to achieve a more stable confi guration. Isotopes that decay spontaneously are called radioisotopes. Nuclear emissions are described in Table I-1 and Figure I-1.
Table I-1 - Characteristics of nuclear emissions
Particle Composition Shielded or Blocked by α 2 protons + 2 neutrons sheet of paper β- electron aluminum foil positron (similar to an electron but β+ aluminum foil with positive charge) ν neutrino - - ν anti-neutrino - - γ high energy photon lead plate or some meters of concrete n neutron block of boron or paraffi n
Based on: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017 - Available at:
Figure I-1: Materials that can shield nuclear emissions
α particle
β particle
γ / X-ray
neutron
neutrino
paper aluminum lead paraffin sheet foil plate block Based on: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017 – Available at:
10 Nuclear emissions have high energies and are able to ionize the atoms with which they collide. Therefore, they are called ionizing radiation. X-rays, although they do not have a nuclear origin, have enough energy to ionize matter, and are therefore also considered as ionizing radiation. Nuclear reactions can be represented in a manner similar to chemical reactions. The following are examples of nuclear reactions: U 256 U∗ 92 Pu 256 ∗U + 92 U (i-2) 238 Pu 234 U + 4 94 25692 U∗ 2 n + U ( 238U )→ 23492 Ba +4α Kr + 3 n + E 94 PuU 25692 ∗U +2 1 n + 235 U (236 U∗ )→ 14192 Ba +α 92 Kr + 31 n + E 0 92 92238256Pu∗ 56 234UU +36 4 0 →H + H9492 → He 92+ n +2E (i-3) 1 n +235 U 236(238∗U )→ 141234 Ba +924α Kr +13 n + E 0 92 Pu92 U256+56 ∗ 362 0 2→H + 3 94H → 4→He9292+ 1 n +αE 1n + 2352381U (1236U234Pu∗) 2 1414 U0Ba++ 92 Kr + 31n + E 0 92 294O→+ 392p →92 4→F 256 1n + E36 0 n + 1 U 235( 1 UH)+1236→ 238 H∗ 2Ba +234He141α +0Kr n+4+923En + E 1 0 9218 O→+ 192p94 → 18→F 9256 1 n +2E36 0 (i-4) 1 235n + 2368U 2H∗ (+1 3HU141 )→ 9 4He 92+0Ba 1+n α+ E1Kr + 3 n + E 0 92 921 O1→ (p56, n)2 →F36 0 0 → 18 2 O +1→ 3 p →18 4 F 1 1 n + E 1 H235+8 1H 1236 1 He∗ +9 2 n141+0E0 92 1 0 92 1892O→ (p→, n) 18→56F 36 0 2 318→OH + 41pH → 181HeF + 1nn++EE 1 Be1+8 18e21 Li0189 + +0 (i-5) 18 → 1 O→ (p,18n) → F 1 O + 2p 13 F 4n + E01 7 Be 81+ 0 e−1 → 7 2Li9 +→ +0 18 4 1 O−1+ 1818 pO →(p3, n1)F 18 F n + E 8 1 9 → 0 ν γ 7 N0 =18− N e7 18 4 Be18 O+→ −(1p , n1e) → F3 18 Li + 1 + 8 N =1 →N e−λ9t ν 0 γ (i-6) 718Be + 0e−18→0 ( 7 ) Li → + + 4 −1 O p, n3 F 7 0T− →−λ7t ν γ Be + e N18 =Li0 +N e +18 4 −1T → 3 ν γ 7 0Be−+ N7e1=� N e −Liλt + + 4 −1 3 2 0 → N1 T ν −λt γ (i-7) 7N = N 0e −� 0 7 4 −12NT2 3 N−=λt 1→N e ν γ 0 �2 T 2 N1 −λt Equation i-21 describesN �N 20 the spontaneous decay of plutonium-238 which, after the =TN2 emission of an α21 1particle,� 2N 4N is transformed into uranium-234. N 2 =2 1 In equation i-3,2 ∙ 1 a2 uranium-235N �42 N nucleus absorbs a neutron and transforms into uranium-236, 2 N= in an excited state;∙21 thenN2 it N4divides into two smaller nuclei, barium-141 and krypton-92, 2= emitting 3 neutrons.1 N 2 ∙NThis2 reaction4 is called fission and releases a large amount of energy. = Equation2 i-42 describes1∙4 N Nthe reaction between a hydrogen isotope with 1 proton and = 1 neutron (the ∙deuterium2 2 , 4which can also be represented by the symbol D) and another
isotope of hydrogen, with∙ 1 proton and 2 neutrons (tritium, also represented by T). The two nuclei fuse into a nucleus of helium-4, emitting 1 neutron and great amount of energy. This reaction is called fusion and is one of the main sources of energy of the Sun and the stars. Equation i-5 describes the bombardmentU of oxygen-18 by a proton, resulting in 256 ∗ fluorine-18, while emitting a neutron92 and energy. Equation i-6 is a simplifiedPu way of Udescribing+ the reaction of equation i-5: the initial 238 234 4 94 92 2 nucleus, the involvedn + particlesU ( (inU parentheses))→ Ba + αand Kr the+ 3 finaln + E nucleus are indicated. In equation 1i-7, we235 have 236an example∗ 141 of electron92 1capture: the beryllium-7 nucleus 0 0 absorbs an electron from92 →itsH +own92 H electron→ He56+ cloud,n +36E transforming itself into lithium-7 and emitting a neutrino and energy2 in3 the 4form of1 γ radiation. 1 1 2 0 O + p → F n + E 18 1 18 1 Radioactive decay 8 1 9 0 O→ (p, n) → F During radioactive decay, the18 number18 N of radioisotopes decreases with time t, from
an initial number N0, accordingBe + toe an exponential Li + + law: 7 0 − 7 4 −1 3 N = →N e ν γ i-8 −λt T 0
1� 11 N2
2 1 N N = 2 2 4
∙ U 256 ∗ 92 Pu U + 238 234 4 U 94 92 2 → α 256 ∗ n + U ( U ) Ba + Kr +92 3 n + E Pu U + 1 235 236 ∗ 141 92 1 238 234 4 U 0 92 92 56 9436 920 2 → → → α 256 ∗ H + H n +He +U n( +UE) Ba + Kr + 3 n + E 92 Pu U + 1 235 236 ∗ 141 92 1 2 3 0 4 92 1 92 56 36 0 238 234 4 1 1 2 →0H + H → He + n + E 94 92 2 → n + U ( U )→ Ba +α Kr + 3 n + E O + p F 2 n +3 E 4 1 1 1 2 0 1 235 236 ∗ 141 92 1 → 0 0 18 1 18 1O + p F n + E 92 →H +92 H → He56+ n +36E 8 1 9 0 → → 18 1 18 1 2 3 4 1 O (p, n) F 8 1 9 0 1 1 2 0 O→ (p, n) → F O + p → F n + E 18 18 18 18 18 1 18 1 8 1 → 9 → 0 Be + e Li +Be ++ e Li + + O (p, n) F 7 0 − 7 18 18 7 0 − 7 4 −1 → 3 ν γ Be + e Li + + 4 −1 3 N = N e → ν γ 7 0 − 7 N = N e −λt 4 −1 → 3 ν γ T 0 N = N e −λt −λt The time required for the decay0 of half the nucleons in a sample is called0 the half-life 1� T T N2 and represented by the symbol . Thus, if at the beginning of an observation there are 1� 2 N2 1� N radioactive nuclei in the sample,2 after a half-life there will remain only 2 radioactive N 1 N N nuclei; after 2 half-lives, there will be only = radioactive nuclei, and1 Nso Non. Figure 2 2 2 4 = 2 2 4 I-2 shows the variation of the number of radioactive∙ nuclei as a function of time. 1 N N ∙ = Figure I-2: Variation of the 2number2 4 of radioactive nuclei as a function of time, in a case of spontaneous decay ∙
N
N/2
Number nuclei of N/4 N/8
T 2T 3T ½ ½ ½ Time
Source: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017 - Available at:
Table I-2 - Origin and half-life of some radioelements Radioelement Half-life Origin 232Th 14 ∙ 109 years 238U 4.5 ∙ 109 years Half-life comparable to that of Earth’s age 40K 1.3 ∙ 109 years 14C 5,730 years 3H 12.3 years Formed in the upper atmosphere 7Be 53 days
12 Radioelement Half-life Origin 210Pb 22.2 years product of 238U decay 239Pu 24 ∙ 103 years 137Cs 30 years Formed in nuclear tests and explosions 90Sr 28 years 60Co 5.3 years Obtained in reactors for medical and industrial applications 131I 12 days Obtaining ionizing radiation beams In order to promote nuclear reactions and obtain radioisotopes artificially, it is necessary to obtain beams of particles or radiation. Beams of charged particles are obtained in linear accelerators or cyclotrons, as shown in Figure I-3.
Figure I-3: How to obtain beams of charged particles
B
vacuum pump + / - target
+ E A B C D E F source of - / + particles
(A) (B)
A: In a linear accelerator, a metal filament is heated to separate electrons from the metal atoms; these electrons are accelerated in regions with alternating electric fields, synchronized with the movement of the electrons, in order to accelerate them always in the same direction. Proton beams can be obtained in a similar way. The beams are concentrated using magnetic fields. B: In a cyclotron, at the same time as they are accelerated, the charged particles are deflected by magnetic fields, moving in a spiral path. At each turn, the electric and magnetic field values are adjusted to increase beam energy Source: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017. Available at:
The neutron beams are obtained inside fission reactors, which produce high energy neutrons. They are moderated (i.e. have their kinetic energy reduced) by hydrogen-rich material contained in the reactor, usually water or heavy water (containing heavy isotopes of hydrogen). The collisions of neutrons with nuclei of similar mass (hydrogen or deuterium) cause the energy to be distributed among them. Another way to obtain neutrons is to use indirect reactions, in which charged particles are directed to a target and promote a reaction, thus emitting the desired neutrons. There are also some radioisotopes that decay with neutron emission. X-rays can be obtained by deceleration of charged particles or by bombardment. When charged particles are decelerated, there is an emission of X-rays, in the phenomenon known as Bremsstrahlung,
13 a German word for braking radiation. This effect is obtained by directing the particles against a target. At the same time, the particles displace electrons from the innermost layers of the target atoms; higher-level electrons “fall” to take the place of released electrons, and thereby emit X-rays whose energy corresponds to the energy difference between the initial and the final electron states. Interaction of radiation with matter The interaction of radiation with matter depends on the type of radiation: whether from photons (electromagnetic radiation), charged particles or neutrons. The electromagnetic radiation (photons) interacts with matter in three different ways, depending on its energy: the photoelectric effect, the Compton effect and pair production (Figure I-4). In the photoelectric effect, a photon strikes a metal surface and releases an electron from the surface. This phenomenon occurs for lower photon energies. With intermediate photon energy values, a photon and an electron free or weakly bound to an atom behaves like two particles that collide, modifying their trajectories and obeying the laws of conservation of energy and momentum. This phenomenon is called the Compton effect. If the energy of the photon is very high, pair production can occur: the photon disappears, giving rise to an electron and a positron, obeying the law of conservation of mass-energy. This phenomenon occurs in the vicinity of a nucleus, which recoils, obeying the law of conservation of momentum. The inverse phenomenon may also occur, pair annihilation: a positron and an electron mutually annihilate each other, generating photons of energy corresponding to the masses and energies of the pair. Although they are not of nuclear origin, these photons are called γ- radiation due to their high energy.
Figure I-4: A: illustration of the photoelectric effect, B: Compton effect and C: pair formation
incoming stripped photons electrons scattered photon
incoming photon
free scattered electron electron
photon (A) (B)
e-
(C) e+ Source: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017 - Available at:
14 The charged particles interact with atoms mainly by releasing electrons (ionization) or by transferring them to higher energy levels (excitation). During the interaction, they decelerate and emit electromagnetic radiation. Neutrons, as they have no electrical charge, interact with the nuclei through scattering (collisions with energy exchange) or capture, in which case they take the nucleus to an excited state and provoke nuclear reactions or fission of the nucleus. Detection of ionizing radiation The development of detectors for each type of radiation is based on the ways it interacts with matter. Generally, a radiation detector consists of a radiation-sensitive element or material and a system that transforms the effects of radiation into a measurable quantity related to the amount of radiation. Frequently, the radiation energy is transformed into an electric quantity, which can be easily and accurately interpreted or measured. The first radiation detectors used films with photographic emulsion. The emulsion consists of grains of silver salts, which are ionized by the passage of the radiation. The silver are reduced to metallic silver, forming an image that shows the radiation path. Photographic emulsions are still used in special cases. Currently, the most common detectors contain gas, which is ionized by the incoming radiation; the ions move through an electric potential, causing an electrical pulse that can be measured. The best-known gas detector is the Geiger-Müller counter (Figure I-5).
Figure I-5: Schematic of a Geiger-Müller counter
helium, neon or argon positive electrode gas at low pressure (central wire) radioactive electric source pulse + - 450 V
electric
thin mica pulse pulse electric window negative electrode (aluminum tube) scale meter
The radiation ionizes the gas contained in a chamber; the ions move through an electrical potential between the shell and a central wire, causing an electrical pulse to be recorded in an external meter. Based on: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017 - Available at:
More modern detectors use scintillators, which are crystals that emit light after the ionization caused by the passage of radiation; the emitted photons generate electrons, which are multiplied and measured in an external circuit (Figure I-6).
15 Figure I-6: Schematic of a scintillator detector
charged scintillator particle detector
photons light guide
photocathode
photomultiplier dynodes
The scintillating crystal emits photons after the ionization caused by the passage of radiation; when the photons attain the photocathode, electrons are released due to the photoelectric effect. The electrons emitted are accelerated and collide against metal plates (dynodes), from which other electrons are released. The amplified electron beam forms an electric pulse, which is analyzed by an external circuit. Source: R. P. de Carvalho and S. M. Velasques de Oliveira - Applications of Nuclear Energy in Health - IAEA, SBPC, 2017 - Available at:
It is also possible to perform radiation detection by using semiconductor materials: the radiation ionizes a semiconductor crystal and the emitted electrons are trapped at unoccupied levels of energy, in impurities of the crystal. These electrons can be released, for example, by increasing the temperature of the crystal; upon returning to their original energy levels, they emit photons, which can be transformed into electrical pulses.
16 CHAPTER II - STABLE ISOTOPES
Almost all the elements have several isotopes (nuclei with the same number of protons, but diff erent number of neutrons), occurring in nature inH diff erent proportions. Some are stable, others emit radiation of well-defi ned type, energy and1 half-life. As we shall see below, 1 it is possible to use the ratio of heavy to light isotopesH to determineO certain characteristics 1 16 of the substances and compounds formed by these 1elements.8 H O H 1 16 2 H Water isotopes 1 8 1 O H O 1 H 1 The water molecules (H2O) 16are mainly formed2 by 17 and O , but there is a small 1 8 8 O 1 O 16 number of molecules formed by H (deuterium), or 1 . Table8 II-1 shows the average 2 17 18O H abundance of stable isotopes of hydrogen and oxygen.8 The8 determination of these average 1 O (RO 16 R ) 2 values is done using sea water. = 8 11000 17 18 R H O 8sample std 8 (R R 2)− 17 Table II-1 - Abundance of stable isotopesO inδ sea water1 H ∙ = stdH1000 8 18 [heavyR isotopeO concentrationO ] R =sample std 1 Hydrogen isotope Relative abundance8 − 171H 18 Relative abundance H (R R ) [lightOxygen isotope81 isotopeO concentration ] δ std ∙ 8 = [heavy1000 isotope concentration1O(RO ] R ) 1 sampleR std =161 1000 1H 0,99985 R = 18o168O 0,99757 − [light isotope concentration8oo R ] O δ ∙ 8 H sample std 1 std (R 16HR ) − 16 [heavy isotope concentration] ⁄ o 1 = Oδ =28 10 oostd1000 ∙ 8O R = o [heavy12H isotope concentration] sampleoo R 1 std H [light0,00015 isotope concentration] R18= O 0,00038 16 −2 O 28 (δR ⁄ Ro[light171) isotope⁄ ∙ concentration] H O =δ 10 std17oo− 1H o [ heavy isotope8O concentration 1000 = 10 ] O oo R = R 8O 1 18sample std O o 0,00205 2 1 [light isotope− 17 concentrationoo ] 171 ⁄ (Ro δ R −) ⁄188 8O O = 10 oo O std 1000188O=∙ 10 − O R(R =80,R99R) ⁄ o The standard values for the relative18 abundancessample ofR 16hydrogenstd(R and ooxygen R O in)= seawater10 oo are measured at the 17 8 − = 18oo 1000 188 (R R ) = R 8 1000 International 8Atomic Energy Agencyδ (IAEA)− ⁄labs inH Vienna, (sampleRsample ∙Austria,R R18using−std)std a mixture of water from fi ve (R OR ) 1000 = std10 sample(R ⁄ − ostdR ) continents, and are known by the acronym VSMOWR (from= = Vienna0O,99=[R Standard−O10δ] oo −Mean1000 ⁄Ocean Water). sampleR std 2 δ ∙ 1000 = 10 = 18 1000 1 δ Rstd ∙ R 8 − [heavysample isotope18stdR concentrationstd ] sample std O [heavy18 isotopesample[ −O] concentrationstd ] (R − R ) std ∙ R(sample−R= R std) − = 1000 R = 0,99R R =δ [light[ δ O ]isotopestd− concentration⁄ ∙ ] δ The variationstd in∙ the relative abundance17 of stable[[heavylight isotopeisotopes isotope16 std 1000concentration concentration in= a given∙ 10 ] ]sample− is related sampleR std 8 [heavy isotope concentration ] R =sampleR18 stdR = 0,99R R = − O [ O−] δto the ratio in the standard∙ samplesample by: std [light isotopeo18 concentration ] [light isotopestd concentration ] [ O] 18 o ooo∙ − [heavy isotope concentration ] 16std =𝛿𝛿𝛿𝛿0 oo𝑂𝑂𝑂𝑂sampleooδ std 8 R = 0,99R [ O] R = [18O](R R ) o⁄ o [light isotope o concentration] 18 Oδ =⁄,oo⁄10 oo oo oo = (vapour1000O =) = 1013 oo18 o [ O] 16 sampleR std=𝛿𝛿𝛿𝛿sample0 𝑂𝑂𝑂𝑂18oo std 1 18 [ ⁄O] o o⁄ o −(R δ (rain OR=) = )−103 o ⁄oo O = oo10 oo (R δ R −) oo⁄ 16 δ 18 std δ δ∙ ⁄ o − 1000⁄ = 10 (vapour) =1813[ 18ooO] 1000 = 10 𝛿𝛿𝛿𝛿[heavy𝑂𝑂𝑂𝑂o isotope concentrationR 1 ] o 18 ⁄ o = 0 oo (RsampleRδ(vapourRstd) =)− 15⁄ oo18 (R OR= ) 10 oo R = 1 sampleδ − o std− ⁄ o δ − ⁄ [light isotopeδ17 (concentrationrain) = −3 16oo⁄ ] 1000=𝛿𝛿𝛿𝛿0= 𝑂𝑂𝑂𝑂 oo 10 1000 = 10 δ ⁄ o R2std ∙ o − R 18 (vapour) = 13 oo sampleδ std(rainstd) = −∙5 oo⁄ − sample std 1 R − o18= 0,99R o (R δ − R −) ⁄ o δ(vapourR) =− 15⁄ =oo 0(vapour,99δR ) = ⁄ 13 oo 1 o 2 𝛿𝛿𝛿𝛿 𝑂𝑂𝑂𝑂o ∙ − ∙ 1000 = −10 δ (rain) = −3 oo⁄ oo δstd = 0 −oo ⁄ R std 2 Rsampleo =C10 ,99Rstd o sampleR std= 0,99R δ (rain) =sample−5 oo⁄ δ (rain)std= −3 oo⁄ − 1 o ⁄ o δ [ O⁄ ] o δ(vapour) =− 15⁄ Ooo = 10 oo(vapour [)12= O13] oo ∙ − 2 1 std sample⁄ 186 std ⁄o sample std δ 1 − [18 Oδ(]vapour) =− 15 oo R = 0,99R 2 o18 δ C [ C O− ]o ⁄ [ O] δ (rain(R) = −5 oo⁄ R ) (rain) = 3 oo δ − ⁄ 16 2 12 131618δ (rain) = −5 o ⁄ 2 10001 = [10 O] oo sample[18O] std ⁄ 6δ(vapour) =6− 15⁄ o δ sample−R std C N oo [ O] C 1618 2 − 18 δ − ⁄ 16 2 =14𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o o C [ 18O] 12 std ∙ δ13 (rain−)==𝛿𝛿𝛿𝛿0 −𝑂𝑂𝑂𝑂o5 oo oo⁄ 6 7 oo 6 R = 0,99R 18 12 18 C N2 N⁄ o 16 δ (vapourδ =𝛿𝛿𝛿𝛿)0−= 𝑂𝑂𝑂𝑂o 13⁄ o oo6 =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o (vapourδ )C= ⁄oo13 oo C oo 13 sample 14std 15 71 7 o 18 6 [ O] δ1(vapour(rainδ 12))== ⁄−313 o ooo⁄13 (vapourδ ) =o⁄ 13 o N δN (rain) =S −3 oo⁄oo =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂 oo oo 6 6 18 1 1 C [ O] 15 δ1 32 − o⁄o N 1 14 δ δ(vapour(rain))==−−315 ⁄ ooo⁄oo δ (rainδ ) = ⁄−3 o o⁄ 7 7 (vapour16) = 15 oo (vapour) = 13 oo oo 16 S 13 S 14 N 2 1 6 δ2δ (rain) = −−5 o⁄o⁄ 7 1 1 o δ (vapour(rain))N== −515 o oo⁄oo N δ δ(vapour ) =−−15o⁄ ⁄oo 15 32 34 oo (rain) = 3 oo 18 16 16 7 2 2 𝛿𝛿𝛿𝛿 𝑂𝑂𝑂𝑂o δ Sδ 2 14v −− o⁄ ⁄15 2 1 o S = 0 oo δ (rain7) =C− 5 ⁄oo δ δ(vapour(rain))==−−515 ⁄ ooo⁄ C 7 oo 34 N S 32 o 2 12 2 16 (vapourδ ) = ⁄ 13 16ooδ 12o − ⁄ δ2δ −− o⁄ ⁄ v 15��E��6⃗ C 32 (rain) =C 5 oo S 7 6C 16 δ1 − o ⁄ 12SC S 2 34 (rain) = 3 oo δ 12 − ⁄ o 136 6C 16 3213�⃗6C 1 ����⃗ 34 C v δ(vapour) =− 15⁄ oE 166N 16 12 oo 13N S v 136 2 146 6C o δ (rain) = −5 o ⁄�⃗ 34147N N ��E��⃗ oo 7 16 N o 13 2 v14 ��E��⃗ 146 δ − ⁄ 157 7N �⃗ C 157N N o7S 14 12 ��E15��⃗ S �⃗ 157 6 327 7N C 1632S S 16S 15 13 �32⃗ S 327 6 1634 16S N 1634S S 16v 32 14 34v 1634 7 16 16S N vo v ��E��o⃗ 15 ��E��⃗ 34 7 16 S ����o⃗ �v���o⃗ E�⃗ E 32 �⃗ 16 o S ��E�⃗�⃗ �⃗ 34 16 �⃗ v
o ��E��⃗
�⃗ H H H H 1 1 1 H 1 1 11 H O 1 O O1O 1 1 1 16 16 16 O 8 8 168 O H 8H H H16 16 8 8 2 2 2 1 1 21 H H O 1 O O O2 2 1 1 17 17 17 8 8 178 O O O 8 O O 17O 17 18 8 8 18 18 8 8 188 O O (R R ) (R (R R 8 ) R ) = =(R 18R181000) 1000 = 1000 = R R 8 8 1000 sampleR std sample(Rsample(RRstd− stdR R ) ) − = =sample− std 10001000 δ δ Rstd−R∙ ∙ δ std ∙ δ [heavystd sampleisotopesample concentrationstdstd∙ ] [heavy isotope concentration] [heavyR = isotope concentrationstd − − ] R = R = [heavyδ δ isotope concentration∙ ∙ ] [Rlight= isotope[light isotope concentrationstd concentrationstd ] ] [light isotope concentration] [light[heavy[heavy isotope isotope isotope concentration concentration concentration] ] ] where R R= = . [light[light isotope isotopeo concentration concentration] ] o o oo oo oo o oo ⁄o o o 2 ⁄ o ⁄ O =o oo10 oo O = 10 oo The unitsO = of 10 are⁄ oo oo (permil) . For example, if we have a sample, with , this o 18 O = 10 oo 18 indicates( Rthat:18 R )⁄ ⁄ o o (R R δ18) O O=−= 10⁄10oo oo (R δ R −) ⁄ δ −δ ⁄ 1000 = 10 1000 = 10 (R Rδ 18R181000−) =⁄ 10 R sample std 1000 = 10 sampleR std sample(R(RRstdδ−δ R R−) −) ⁄ ⁄ H − sample− std ∙ 10001000=−= 1010 H Rstd− std ∙ − stdsampleRsampleR∙ =std0std,99−R 1 R std= 0−,99− R∙ − 1 R1 = 0,99R R H= 0,99R 1 O sampleHstd std ∙ ∙ std − − O R 1 = 0,99R H sample std sample R [ Ostd]= 0,99R 16 that is, the ratio [sample1 ofO1] in thestd sample is 1% less than in the standard.16 8 [ O] 1 [O[18 OO]] 1 8 H Osample sample stdstd 1 H [18O] [18O16] [ O ] O [1816O[] O] 2 It has been16 observed8 that molecules containing lighter isotopes are2 more likely1 to16 evaporate 816 H 18 16 1 [ [ O18]O] 8 O or participate inH chemical 1618 reactions, because molecular bonds are moreO easily broken. For the 2 H 𝛿𝛿𝛿𝛿 16 𝑂𝑂𝑂𝑂o 17 18 2 18 1 = 0 16oo 17 8 o same reason, molecules 18 with heavier isotopes are more2 likely to remain in condensed=𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂 phases. =1𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o O 8 O oo O oo=𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o o 1 (vapourδ ) =18⁄oo1318 oo O From these observations,17 o it is possible to study the Oevolution of in the18 pathδ described⁄ o δ17 ⁄8 =o𝛿𝛿𝛿𝛿0= 𝛿𝛿𝛿𝛿𝑂𝑂𝑂𝑂0 𝑂𝑂𝑂𝑂o (vapour) = 13 oo (vapour1) = 13 oo oo oo 18 8 δ8(vapourδ O) = ⁄−13o o⁄ 17 by water from evaporation(rain) = 3 oo ooin the oceans to the formation of rivers(8R and lakes1 R by) rainfall. 1 O 8 (R R ) δ − o ⁄ δ (vapour−(vapourδo δ)⁄=)⁄=13⁄ 13o o = (rain) =10003 oo (rain1) =1 183 oo oo oo O= δ 1000 Figure II-1 givesδ18δ(vapour( rainan) example=) =−3 15o⁄ o⁄ of this path. The change in the isotopic distributionR during a 8 oooo R sample 1 std (R 8 1 1 R ) 18 sample std − ⁄o 1 δ δ (raino) = −3 −o o⁄ ⁄ δ(vapour) =− 15 oo vaporization/condensation(R δ(vapour2)1=R− 15(rain⁄) oo) = 3cycle oo oo is called Rayleigh fractionation8 δ −. ∙ = δδ(vapour(rain) =−−515 o⁄ o1000⁄ (R R ) std = R 1000oooo δ [heavy isotope∙ 2 concentration] 1 1 std o 2 Rsampleδ δ o std− − ⁄o ⁄o = [heavy isotope1000 concentrationδ (rain) =] −5 ⁄ δsample(rain2) =2(vapour−std5(−vapour )⁄ =) =15 15 oo oo R = oo δ −δ(rain) =oo−5 o⁄ ⁄ 18O sampleR = std [light isotope concentration ] Figureδ II-1: The variationstd C ∙ooof δ in the water cycle 2 δ 2 2 ∙ − [light isotope concentration] ⁄ [heavy2 std isotopeδ δ (rain(rain⁄ concentration) =) =−5 −o5 o⁄ ⁄ ] δ − [heavyδ isotope2 −concentration 12 oo oo] δ std ∙ C R = δ C − ⁄ [heavy isotope concentration] o R = [light isotope2 concentration6C ] oo δ 2 C − ⁄ o 12 [light isotope12 concentrationδ C − ⁄] R = oo 6 6 12 C [light isotope concentration] C 136 ⁄ o C o 61212 ⁄ Oo= 10 oo o oo C O = 10 oo 13 13oo N6 6 o 13 C C oo 18 6 6 ⁄ 14 o (18R R ) N ⁄ O N= o 106 oo (R R δ) − ⁄ O = 10 oo7N13 13 ⁄ δ − ⁄ 1000 = 10 N6 6 O = 10 o 1000 = 1014 1814 N oo sampleR std 7 (R 18 R7 )14 N R − δ −157 ⁄ rain 18 samplevapour std rain N (R R ) N 7 − o δ − ⁄ 14N1000 14 = 10 o o std oo∙ − 1000S7= 10 ( R ooδ R −)δ = -15⁄ ⁄oo ∙ δ = -5 ⁄ − 15 sampleR vapour15 std 7 δ = -3 ⁄ std R = 0,99R R − 15 N N 1000R = =100 ,99R 7 sample std 7 o 32 R S − δ = -13S ⁄oo∙7 − sample std std ∙ 1615S 15− − sample std stdR = 0,99S7 R7 sample std 32 R =320,99R S S std ∙ − [ O] 16 16 3234 R = 0,99R [ O] S S 1616 [18O] sample 32S 32std 18 sample [ O]vstd1616 [ O] 34 34 sample std 16 [ 16 O] 34 S S 16 18 [ O] 16 v v [ O16] o [18O] v����34⃗ 34 E16 16 18 18 16 [ O] 18 𝛿𝛿𝛿𝛿 𝑂𝑂𝑂𝑂o o ocean16 o v v o = 0 oo ����⃗ ����⃗ =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂 E Eo �o⃗ 16 oo δ = 0 ⁄oo 18 ����⃗ E o (vapourδ ) = ⁄ 13 o 18 𝛿𝛿𝛿𝛿 𝑂𝑂𝑂𝑂o o ⁄ o oo = 0 oo��� �⃗����⃗ 18 (vapourδ ) = 13 = 𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o E E oo �⃗ �⃗ oo 𝛿𝛿𝛿𝛿 𝑂𝑂𝑂𝑂o 1 o The standardH is given by the isotopic composition of sea water, = 0 oo . The1 evaporationδ (rain )is= easier−3 for⁄ the lighter δ ⁄�⃗ o δ − o ⁄ oo ( vapour) =o 13 oo (rain) = 3 oo isotope: 1 (vapourδ ) = ⁄ 13 oo�⃗ .� ⃗The clouds move to the mainland, where the vapor condenses in rainfall and the (vapourδ ) = ⁄ 13 o δ1 − ⁄o 1 1 o oo1 (vapouro ) = 15 oo inverse occurs:1 δ (rain) = −3 oo⁄ . Then the water evaporates again, with δ(vapour) =− 15⁄ and the clouds are δ O(rain) = −3 o ⁄ oo oo δ1 − o ⁄ 2 o carried by16 the wind1 from the coast to the inland regions, where(rain they) = condense3 oo2 givingδ (rain) = −5 oo⁄ . δ(vapour) =− 15⁄ o δ (rain) = −5 o ⁄ 8δ1 − ⁄o oo oo (vapour) = 15 oo 1 2 H δ(vapour) =− 15⁄ o δ − ⁄ 2 o oo2 C 2 δ (rain) = −5 oo⁄ δ − ⁄ δ2 (rain ) = −5 o ⁄ C Stable1 isotopes inoo organic material δ2 − o ⁄ 2 (rain) = 5 oo 12 O δ − ⁄ 12 6 δ2 − ⁄C 6 C The17 study ofC the origin or transport of organicδ2 matter− ⁄ can be doneC using the isotopic 8 12 C 13 ratios of carbon,O 12 nitrogen6 or sulfur, in addition to the hydrogen and13 oxygen6 ratios shown 6 C 12 6 N above. 18Table II-2C shows the relative abundance of the6 major stableN isotopes of these three 8 13 C 14 (R R 13) 6 14 7 = elements. 6 1000N 13 7 N 6 N R N N sample − std 14 15 14 7 15 7 δ std 7∙ N 14 7 S [heavy isotope concentrationN ] 7 S 15 N R = 2 32 [light The isotope use ofconcentration permil15 (a.k.a.7 ]parts per thousand) is a way of expressing ratios 32in terms16 of whole numbers. 7 S 15 16 S 7 S Given a ratio or fraction, it is converted to a permil-age by multiplyingS by 1000S and appending a "mil o 32 34 sign" oo . From:32 16
18 [ O] 16
18 o =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂 oo
o (vapourδ ) = ⁄ 13 oo
1 o δ (rain) = −3 oo⁄
1 o δ(vapour) =− 15⁄ oo
2 o δ (rain) = −5 oo⁄
2 δ C− ⁄ 12 6 C 13 6N 14 7 N 15 7S 32 16 S 34 16v
o ��E��⃗
�⃗ H 1 1 O 16 8 H H 1 2 1 2 1 1 O O 16 17 168 178 8 8 H H O 1 2 18 1 12 18 1 O 1 O (R 8 R ) O O = (R R ) 1000 16 17 = R 1000 16 178 sampleR std 8 8 sample − std 8H O − H δ std ∙ 2 18 [heavy isotopestd concentration] 12 188 [heavy isotope concentration] 1 O (R 8 R ) R = O = (R R ) 1000 [light isotope concentration] 17 = R 1000 178 sampleR std 8 sample − std o O − o oo O δ std ∙ oo 18 δ [heavy isotopestd concentration∙ ] 18 [heavy isotope concentration] ⁄ o 8 R = O =⁄ 10 o oo (R 8 R ) R = [light isotopeH concentration ] O = 10 oo = 1000 [light isotope concentration] H = 1000 18 sampleR std H 1 (R δ R −) ⁄ 1 sample − std o1 δ − 1000⁄ = 10 1 − o ooO 1000 = 10 O δ std ∙ 1 oo R δ std ∙ 1 sampleR std [heavy isotope concentration] 16⁄ o − 16 R = [heavy isotope concentration] O =⁄ 10 o oo − R = O = 8 10 oo std ∙ − 8 [ light isotope concentration] H std ∙ − H [ light isotope concentration] 1618 R = 0,99R 188 R = 0,99R (R δ HR 2−) ⁄ 2 o δ 1− 1000⁄ = 10 sample std 1 o oo O 1000 = 10 sample std O oo sampleR 2 std [ O] sampleR 1− std [ O] ⁄ o − 17 17 O =⁄ 10 o oo O ∙ − [18O] O = 10 oo std 8 ∙ − [18 O] 8 R std = O0, 99R O 18 R 17 = 0,99R 16 (R 18 R ) 8 18 16 (R δ R −) ⁄ O 18 δ − 1000⁄ = 10 sample 8 std 8 (sampleR R )std 18 R 1000 = 10 18 [ O] 18 (R R ) sampleR std = [ O] 1000 =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o = 1000 sample − std (R 8 RR ) =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂 oo − ∙ − sample[18O] std sampleR std std ∙ − = [18 −O] 1000 o − std (vapourδ ) = ⁄ 13 o oo R = 0,99R δ R 16 ∙ (vapourδ ) = 13 oo R = 0,99R sample std16std δ std ∙ [heavy− isotope concentration] 1 [heavy isotope concentration] δ1 − o ⁄ sample std δ R = ∙ δ (rain) = −3 o oo⁄ sample std std 18 (rain) = R3 =oo [ O] [heavy [ lightisotope isotope concentration18 concentration] ] [light isotope concentration] [ O] =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o 1 R = =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o oo δ(vapour1 ) =− 15⁄ o 18 oo δ(vapour) =− 15⁄ oo [18 O] [light isotope concentrationo ] [ O] δ ⁄ o 2 o (vapour) =oo⁄ 13 o oo 2 o oo 16 (vapourδ ) = 13 oo δ (rain) = −5 o oo⁄ 16 (rain) = 5 oo 1 o δ1 (oorain) =⁄ −3 o o ⁄ 2 ⁄ o δ O = −10o oo⁄oo δ2 − ⁄ O = 10 18 (rain ) = 3 oo δ C− ⁄ oo 18 C =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o 118⁄ o o 18 =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o oo O =δ(vapour1 10) =−oo15 ⁄ o oo oo (R δ(vapourR ) =)− 15⁄ 12 (R R ) δ − ⁄oo 6 δ − ⁄ (vapourδ ) = ⁄ 13 o 18 2 1000o = 10 6C 1000 = 10 (vapourδ ) = ⁄ 13 o oo (R RδR2 ()rain) = −5 o oo⁄ C oo δsampleδ (−rainstd) =⁄−5 oo⁄ sampleR std 1 − 1000 = 10 13 − δ1 (rain) = −3 o ⁄ 2 13 Tableδ (rain II-2) = −-3 Relativeo oo⁄ abundanceR δ 2of carbon,−∙ ⁄ nitrogen− and sulfur isotopes6 ∙ − oo sample − stdδstd C− ⁄ N std 1 R =C0 ,99R N R = 0,99R δ(vapour1 ) =− 15⁄ o δ(vapour) =− 15⁄ o oo std ∙ 12 − 14 oo RelativeR = Nitrogen0,99126R Relative 147 Relative 2Carbon isotope sample 6C std Sulfur7 isotopeN sample std δ2 (rain) = −5 o ⁄ C N δ (rain) = −5 o oo⁄ abundance isotope[ O] abundance abundance[ O] oo sample 13 std 15 2 13186 15 18 δ2 − ⁄ [ O] [ 6 O] 7 [ O] δ C− ⁄ 0.9893 N 0.99636 S 0.9502 18 16 [ O] 14 16 12 32 126 147 16 6 16 718 16 C 0.0107 N 0.00364 S 0.042118 𝛿𝛿𝛿𝛿 𝑂𝑂𝑂𝑂o o 13 =150 oo =𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂 oo 18 34 136 157 1634 The reference6 values for the relative abundances=𝛿𝛿𝛿𝛿0 𝑂𝑂𝑂𝑂o of 7 theS isotopeso are measured by the IAEA16 laboratory in Vienna, which N (vapourδoo ) =S ⁄ 13 oo v (vapourδ ) = ⁄ 13 o N oo provides 14the standard samples. The standard for carbon32 is measured in Belemnite, limestone from marine fossils from 14 (vapourδ 1 ) = ⁄ 1332 o o 1 7 δ (rain16) = oo−3 oo⁄ o δ (rain) = −3 o ⁄ the Pee Dee7N geological formation in North Carolina16S (USA), and is named VPDB (Vienna-Pee��E��⃗ Dee Belemnite); theoo N 1 S E standard for nitrogen is establishedδ using(rain )atmospheric=1 −3 o ⁄ air⁄o and bears the name AIR; for sulfur, the VCDT1 (Vienna-o 15 δ(vapour34) oo=− 15 oo δ(vapour) =− 15⁄ oo 157 1634 3 Canyon Diablo7S Troilite) standard, measured1 in meteorites16v found in the Canyon Diablo� ⃗region (USA) is used.) . S δ(vapour2 ) =− 15v⁄ o o ⁄ �⃗ 2 o δ (rain) = oo−5 oo δ (rain) = −5 oo⁄ 32 32 2 16 2 o o⁄ 2 Measurement16S of isotopicδ (rain variations)δ= −5 ��E��o⃗oo − ⁄ δ − ⁄ S ��E��⃗ C C 34 δ2 − ⁄ 34 C 12 12 Tables16 II-1 and II-2 show that, for�⃗6 many elements, the ratio between the natural6 16v �⃗C concentrationsv of the different isotopes12 has orders of magnitude of 10-3 or even less. Therefore,C 6 o C 13 13 the measuring��E��o⃗ instruments must have high6 sensitivity and precision. Mass Spectrometers6 ��E��⃗ 13 N N or Infrared Absorption Spectrometer6 s are currently used. N 14 14 �⃗ 7 7 �⃗ 14 N N 7 Mass Spectrometer N 15 15 7 7 15 S S Figure II-2 shows the operating7 scheme of a Mass Spectrometer (MS), which is an S 32B 32 equipment used to measure the number16 of atoms with a given mass. 16 32 S S The sample to be analyzed is16 vaporized and ionized, and the ions are accelerated by 34��⃗ 34 B S 16F an electric field, acquiring a velocity v . In the figure, the ion shown is negative16 vand its B34 velocity is horizontal, pointing to16v the right. ��⃗ ��o��E⃗ o The ion Fbeam then passesB through �a�EF�� ⃗ velocity filter, where there is an electric field� �E��⃗ and ��⃗ o a magnetic field B . In the figure,F � �E��⃗ is vertical, from top to bottom, andB B is perpendicular ����E⃗ ��⃗ �⃗B B �⃗ to the page andF penetrates F it. F �=���⃗qE E B ��⃗ ����⃗�⃗ ��⃗ ��⃗ In this region,F each negativeF ion is subjected��⃗ to an electric force F F , vertical upwards, F �=���B⃗qE ����E⃗ E v F��⃗ and to a magnetic force F , vertical downwards.F The electric force is proportional to the E ����B⃗ ����E⃗ E charge q of the ion,����⃗ that is, F = qE , and the magneticE force is proportionalF � ���⃗ to the charge E F ����⃗ F ����B⃗ F E and velocity v of the F ion, = thatqE is F = qvB . Therefore,����⃗ it is possible to choose the field E F B intensities so that���� B⃗the electric andv magnetic forces cancel out for ionsF �= ��with�⃗�qE���B⃗ a chosen speed; F = qE B ����B⃗ F = qE these ions will travel inE a straight line and reachF = anqE opening at the end of that region. F = qvB v mv ����B⃗ = qvBF = qE E After crossingE the velocityF = filter,qvBR 2the ions reach a region where therevE is only a magnetic B v E v field, perpendicular to the direction of its velocity.v This field modifies the displacement of mv F = qvB E the ionic beam,= qvBcausing the ionsB to travel a circularv v path whose radius depends on the mass R 2 mv R = m F = qvB F = qvBB = qvB F = qvB F = qvB of the ions. This can be deduced2 if we observeqB that the magnetic force is the centripetal mv R F = qvB force that causesB thev circular= qvB movement of each ion: B B R = m R 2 ∙ B mv mv v mv mv =qBqvB H O H B = =qvBqvB 2 R = m mv = qvB R 2 2 R v qB1 16 1 R 2 R ∙ 1 8 1 = qvB R = m H O HR 2 H O H v qB ∙ v v 1 16 1 1 18 1 v R = m R = m H O H1 8 1 R = mqB 1 8 1 qB ∙ H O RH = m v qB H O H 1 16 1 R = m qB H O1 H 8 1 1 18 1 1 16 1 qB ∙ ∙ 1 16 1H O H1 8 1 ∙ 1 8H 1 O H H O H ∙ H HO HO H H O H 1 8 11 18 1 H O H 3 H O1 H 8 1 ∙ 1 16 1 Standards for161 isotopic16 1 ratios may also be2 provided16 2 by other international organizations,1 18 161 1 for example, by 1 1 18 1 H O H1 8 1 1 H16 O1 H 1 8 1 the NIST1 (National8 1 Institute1 18 of1 Standards and Technology,1 8 1 USA) or IRMMH (InstituteO H for Reference H O H 1 8 1 H 1 16 1 H O H H O H 1 16 1 H O H Materials and1 Measurements,18 1 H O European1 H 8 1 Community).1 8 1 1 118 181 1 2 161 28 1 H O H 2 1 H18 O1 H 1 18 18 1 1 8H 1 O H 1 16 1 1 1 8 1 H HO HO H H 1 8 21 16 2 O 1H 18O 1H H O H 1 8 1 1 16 1 1 16 1 1 8 1 19 1 16 1 21 8 1 H 18 1 H16 O1 H 1 18 18 1 2 16 2 1 8 1 H O H 1H O H 1 8 1 δ 1H 16O 1H H O H O H 2 C 1 8 1 2 16 2 2 16 2 1 H O H 1 28 161 2 181 8 1 O 13 2 16 2 1 8 1 H 2 1 8 1 H H δ 1 2 16H 2 C O 18 δ 1 8 1 2 H 2 2 1 δ 2 1 1 13 18 C O O 12 O O δ δ 18 18 C 13 N 1 18 18 O δ δ 13 δ 15 δC C δ 18 C N δ δ S C 13 δ 13 13 13 C 15 δ N 34 δ δ δ 13 δ S N 15 δ δ 34 15 δ S N N N N δ δ 34 15 S 15 15 15 N 34 δ δ S δ S δ 15 δ S δ S 34 δ S 34 34 34 δ δ δ 34 δ δ A detector plate, placed at the end of the path of the ions, measures the beam intensity for each value of the radius, that is, for each mass value.
Figure II-2: Scheme of a mass spectrometer
velocity detector
B
��⃗ F B - E slower ions F����⃗ B ��⃗ F B ��⃗ F �=���⃗qE faster ions F E ����⃗ B E F E v F����⃗ ��⃗ F �=���B⃗qE F F = qvB F �=���B⃗qE E E F����⃗ B v mv E v = qvB B FR 2= qvB F �=���⃗qE F = qvB B v E mR v= m lower mass v = qvBqB B R 2 mv = qvB ∙ higher mass FR 2 = qvB H O Hv R1=16m 1 B 1 8 1 qB mv v H O H R = m= qvB mass separation2 qB 1 18 1∙ R 1H 8O1H H O H ∙ The mass spectrometer1 16has 1the drawback of being a largeH pieceO H vof equipment and 1 168 1 R = m requiring shielding to prevent1H external8O1H magnetic fields from interfering1 16 1 in the measurement. H O H 1 8 1 qB In addition, if different ions1 18with1 the same charge/mass ratio areH present,O H they will also be 21 168 21 ∙ detected. The advantage of1 thisH 8 Otechnique1H is that the same equipment1 18 can1 be used to measure H 1 H 8 O1 H 1 16 1 isotopic ratios in different elements; it is mainly used for H, C, O1H, 16NO or1H S . 1 28 1 H O H 11 168 11 1 1 H 8 O1 H 16 O Laser Absorption Spectroscopy2 2 1H 18O 1H 1 188 1 1 8 1 H 2 H16 O2 H A recently developed deviceδ C is the Laser Absorption Spectrometer1 8 1 (LAS), which works 2 1 16H 1 based on the fact that when illuminated113 with an infrared emitting1 laser,8 1 the molecules absorb O H2 O H the frequencies correspondingδ to their natural vibrations. 1 18 2 16 O 2 1 8 1 The molecules can be comparedδ to mass-spring systems, where18 the atoms would be C H the masses and the bonding forces between them would be theδ springs. These sets may 13 N 2 C oscillate by rotation of the “masses”, compression or bending of the1 “springs”. The vibration δ15 13 O frequencies are characteristic of each molecule, and have frequencies in the infrared range. δ S δ 18 Thus, if there are molecules in a sample that differ by the presence of isotopes of the same 34 δ C atom, the frequencies of vibration N will be slightly different, and the absorption spectrum of δ the sample will show different15 peaks. 13 N δ δ S 15 34 δ S δ 20 34 N δ 15 δ S 34 δ
B
��⃗ F
B ����E⃗ F ��⃗ F B F �=���⃗qE
����E⃗ F E v
����B⃗ F = qE F = qvB
E v mvB = qvB Figure II-3 shows examplesR 2 of absorption spectra for water samples containing different isotopes. The largerF = theqvB isotope mass, the lower its vibration frequency. v Figure II-3: InfraredmvB absorptionR = m spectra of water samples = qvB qB R 2 ∙ (A) B (B) H O H v 1 16 1 ��⃗ R = m B 1 8 1 B F H O qB H O H 2
B ��1⃗ 18 1 ��⃗ ����E⃗ ∙ F1 8 1 F F H O H H O H ��⃗ E 1 16 1F ���1�E⃗ 16 1 ����⃗ B 1 8 1 F1 8 1 F F �=���⃗qE D O/H O (1/1) H O H H O H 2 2 E ����⃗ B 1 18 1F ���2�B⃗ 16 2 ����⃗ E Absorbance (a.u.) F = qE F = qE v Absorbance (a.u.) 1 8 1 1 8 1 H O H H F �=��E�B⃗qE E D O 1 16 1 v v F = qvB 2 1 8 1 2 H O H 1 E O Fv = qvB F = qvB B 1000 1500 2000 2500 3000 3500 4000 3662.6 3662.82 16 3663.02 18 3663.2 mv 1 8 1 = qvB δ 2 FH =B qvB CB R mv -1 m v -1 Wavenumber2 (cm ) = qvB Wavenumber (cm ) = qvB13 2 v 1 B R 2 R R = m Based on: van Trigt, R .: Thesism vO Rijksunivesiteitδ Groningen Based on: Vanderkooi, J. M. et al .: Biochimica et = qvB qB 18 2 v v Biophysica Acta - Proteins and Proteomics, 1749 (2), (2001) available at:
δ S 2 δ (rain) = −5 o ⁄ 34 oo
δ 2 δ C− ⁄ 12 6 C 13 6N 14 7 N 15 7S 32 16 S 34 16v
o ��E��⃗
�⃗ Figure II-4: isotope ratio δ 180 for Lake Victoria (Africa) and for the surrounding waters
) 4 oo
⁄ Lake o 3 0 ( 18 2 1 0 -1 Rivers -2 Wetlands -3 Groundwater -4 Oxygen as δ Isotope Ratio
The positive ratio for the lake indicates that it mainly undergoes evaporation and precipitation and is not supplied by the underground reserve or the rivers, which have δ 180 negative. The wetlands have δ 180 negative, indicating that they are supplied by groundwater and not by lake overflow. Based on document IAEA - Water Resources Program.
Carbon Isotopes Origin of carbon in the atmosphere
The presence of CO2 in the Earth’s atmosphere is mainly due to the respiration of living beings or the decomposition of their remains. Although its concentration is low, this gas is useful because it causes a beneficial “greenhouse effect”, which prevents some of the heat from the sun absorbed on the surface of the globe from escaping back into space. This helps keep Earth’s temperature at levels that are convenient for life maintenance. However, if the CO2 concentration in the atmosphere increases, excessive heat retention can occur, resulting in imbalance of the climate and harm to living beings. The concentration of carbon dioxide in the Earth’s atmosphere remained constant over a long period of time, around 0.028%. However, in the last 150 years, there has been an increase in this concentration, which now reaches 0.040%, which means an increase of 30% (Figure II-5). Through measurements of the carbon isotope ratio, it is possible to study the cause of this increase.
Figure II-5: Variation of CO2 concentration in the Earth’s atmosphere over time
400
CO2
350
300 Concentration (ppm)
250 1800 1900 2000 Year
Based on data from the European Environment Agency (EEA), available at:
22 Measurements of 13C in the atmosphere, as shown in Figure II-6, indicate that this 6 value decreased over time, although the CO2 concentration increased. Plants are known to more easily absorbδ from the air the carbon dioxide composed of lighter isotopes. The isotopic ratio of carbon in plants is therefore different from that in the atmosphere. Over time, the dead plants were buried and transformed into fossil fuels, keeping the same isotopic ratio. The burning of this fuel then releases into the atmosphere carbonic gas with a smaller proportion of 13C in relation to 12C. The decrease in the value of 13C in the atmosphere leads, therefore, to the assumption that the increase in carbon dioxide released into the atmosphere is due to the burning of fossil fuels, a hypothesis δcorroborated by the fact that this trend has been noticed since the beginning of the Industrial Revolution.
13 Figure II-6: Variation of the isotopic ratio C in CO2 of the atmosphere, as a function of time, measured in Antarctica (A) and Australia (B) δ -7.4 (A)
) -7.8 oo ⁄ o (
C 13
δ -8.2
-8.6
2000 2004 2008 2012 2016 Year
-7.6 (B) ) oo ⁄ o
( -8.0 C C 13
δ
-8.4 1995 2005 2015 Year
Based on data from NIWA (National Institute of Water and Atmospheric Research, New Zealand), available at:
6 13 Both the concentration of CO2 as the value of C in ancient times can be inferred by measurements made in ancient tree trunk rings, in sea corals or sponges, or in the air trapped in the ice at the poles. δ 23 Origin of carbon in the oceans Part of the carbon dioxide released into the atmosphere dissolves in ocean waters or is absorbed by microalgae, on the surface of the oceans, and transformed into organic molecules. Eventually, the carbon of organic origin is deposited at the bottom of the ocean.
The pumping of CO2 from the atmosphere by the oceans is useful to maintain stable levels of carbon dioxide in the atmosphere, but the excess of this gas dissolved in the oceans can lead to acidification of the oceans, harming sea life.
There is currently an increase in the CO2 concentration in the oceans, and isotopic carbon analysis in corals and sponges indicates a decrease over time in the value of 13C (Figure II-7), which may be further evidence that excess carbon dioxide is due to the burning of fossil fuels. δ 13 Figure II-7: Variation of isotope ratio C in CO2 of marine sponges, as a function of time, measured in Jamaica δ
+4.9
+4.7 ) oo ⁄ o ( +4.5 C 13
δ
+4.3
+4.1
+3.9 1800 1900 1960 1980 2000 Year
Based on data from F. Böhm et. al. [Earth and Planetary Science Letters 139 (1-2), 291 (1996)], available at:
Nitrogen and sulfur isotopes Isotopic compositions of nitrogen and sulfur can be used to determine the presence of pollution in water or pesticides in food. This is possible because detergents, medicines and chemicals used in industry and agriculture contain large amounts of nitrates and sulfates. The chemical reactions used for the production of these substances occur at different speeds for isotopes of different masses, and therefore, there is a variation in the values of 13C and 13C. Isotope measurements can inform if the nitrogen and sulfur contained in water and food are of natural origin or come from artificial pollutants. δ δ
Acknowledgments: We thank the collaboration of L. Araguas-Araguas and Manfred Groening (IAEA) in the preparation of this chapter.
24 CHAPTER III - APPLICATION OF NUCLEAR ENERGY IN INDUSTRY
Radioisotopes have several industrial applications, such as in chemical, petroleum or mining industries. This chapter describes three of the most common uses in industry: radiotracers, nucleonic control systems and non-destructive testing. Radiotracers Radiotracers are radioisotopes incorporated into a system and monitored to indicate the movement of the fl uid or solid to be studied. They are widely used in the chemical and petroleum industries, as well as environmental process studies. Radioactive tracers are interesting because the detectors are very sensitive, allowing the use of very low concentrations of the radioelement. The detectors used are portable, and measurements can be made in loco. The radiotracer must have physical and chemical properties similar to those of the material to be traced, and its half-life must be compatible with the measurement time: if the half-life is too short, it will not be possible to prepare, transport, introduce the tracer at the test site and perform the measurement before the activity falling to non-measurable values; if the half-life is too long, radioactive material will remain in place after the end of the analysis.
Radiotracers in the oil industry In the oil industry, radiotracers may be used to detect pipeline leaks due to cracks or failures in connections. Since water is normally injected under high pressure to facilitate the extraction and transport of oil, it is possible to use water-soluble radiotracers. These may be soluble salts, such as KBr containing bromine-82, or tritiated water (water where one or both hydrogen atoms have been replaced by tritium).
25 82Br can be obtained by neutron bombardment of the stable isotope 81Br:
Br + n Br + 81 1 82 35 0 35 Br Kr + + → γ T = 35 h Bromine-82 decays by - emission into the stable element krypton-82: 82 82 0 − Br + n e Br + 1 35 → 36 1β ν� �2 81THO 1 TDO 82 T O β 35 0 35 Br Kr + + → γ T = 35 h 2 82 82 Li +0 −n He + T 35 36 1 e 1� The half-life of bromine-82→ is long6 βenough1 ν� 4to allow3 for element2 activity to be observed, 3 THO 0 TDO2 T O1 for example during work in a refinery; after→ the measurements, the radiotracer will be at a very low level, leavingT no radioactiveHe + Li +waste+ n in the He +environment.2 T = 12.3 years 3 3 0 − Tritium (hydrogen atom with 26 neutrons1e and4 a proton)3 1 is the only radioactive isotope 1 → 2 −1β3 ν�0 2 1 �2 Se + → Kr + + of hydrogen. Although its half-life (12.3 years) is short compared to the Earth’s age, it exists T He +76 +4 79 +1 +T = 12.3 years in nature because it is created in34 the upper2 atmosphere36 0 by the bombardment of nitrogen by 3 3 0 − α →NaBr β ν e 1 cosmic rays. Its chemical1 → behavior2 −1 isβ Brthe+ ν� samen as thatBr + of �the2 hydrogen atom and therefore Se + Kr + + tends to bind with oxygen to form 81tritiated1 water,82 which is also called tritium oxide (THO, 76 35Br 4+ 0p 79 35Kr++1 +n 7 Br 34Kr + 2 + 36→ 0 γ T = 35 h 18 TDO or T2O) . The concentration of79 naturalα 1→NaBr tritium 79 isβ very1 ν low (1 atom of T for 10 atoms 82 82 35 0 −1 36 0 of H), but it can also be obtained36 artificially,1 → for e example, 1by the activation of lithium-6 by 35 → β ν� �2 neutrons: Kr Br +BrTHOBr ++ +p nTDO Kr Br T++O n T = 35h 79 79 0 + 7981 1 1 7982 2 1 1 36 → 35 3535 1β 1 0 ν 3635 0 �2 Br Kr Li+ +T n+ = → →4 .5He h + Tγ T = 35 h 6 1 4 3 82Kr 82Br3+ 0 0−+ 2 1 T = 35h 35 36 1 1� → e 1� 79 → 79 0 β+ 2 ν� 2 THO TDO T O 1 The process is accomplishedT 36 He→+35 by subjecting+1β ν lithium-containing T =�212.3 years ceramics to the neutron T 84= 4.5 h flux of a nuclear reactor.3 3 0 − 2 e 1 1 → 2 −1β LiKr+ν �+n n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 He +Kr T �2 Tritium decays into helium-3Se (stable)+ 1 �withKr +- emission: + 684 12 1 4 85 3 76 3364 0 079→ 2 36+1 1+ Kr 34Rb + 2 +36 → 0 T = 4.5 h α →NaBr84 β β ν T85 He85+ +Kr0 +− n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 Kr T = 12.3 years 36 37 −1 1� 3 , 3→ 0 − β ν� ( , ) 2 1 2 −1 Br84+ ep 1 Kr85+ n1 � U → U − β36Np ν�− 0 Pu36 2 Pu − Am The advantages of nusingKrγ tritiumβRbSe++ oxide β + asKr → +a radiotracer2 n γ +T = βare4.5 hits chemical behavior, 238 239 79239 1 239 79 1 241 241 identical to that of water,92 85 and92 85the76 35 fact93 4 0that1− →79in 94 36its decay+1 0+ there94 is no95 γ emission, only low 36Am�� 3734��Np + −21 +�� 36 �⎯0⎯�T 1=� 432�� years - , → αβ →NaBrν� ( β, ) ν2 energy emission, 241whichU Kr is easilyU237 Br +shielded. Np4 + The Pu disadvantage T Pu= 35h is thatAm the energy of the 95 93 − 2 − 1� − emitted radiation is low:79n γit→ is at79β most0 18.6α+β γkeV, with2 n γ an2 averageβ value of 6 keV. For its 238 36 239 35 Be239+ 1 239 C + n + 241 1 241 92 →92 93Br +β p ν94 Kr + n 94�2 95 detection,β it is necessary �to� add the�� tritiatedT �� =water4.5 h sample �⎯⎯� to a liquid�� scintillation detector, Am 9Np79+ 4 +1 12 79 1 T1 = 432 years 4 2 6 - 0 which emits fluorescent241 light237 in 35response4 α 13→ →to 36 radiation.0 γ This procedure needs to be 2 1� KT 1 95 → 93 α 2 γ2 �2 carried out in the laboratory.Kr BrBe++ + C + n + T = 35h 79 799 046+×�8410 12β J 1 Although the half-life of tritium is relatively long,1 compared to the time of 36 → 354 Kr12βα+3→ n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 ν 6 0Kr γ �2 measurements in the industry, the residueT is2 =notKT−421. 5 harmful h to humans or the environment. Cf 84 Zr1 + 85Ce + 4 n This is due to the fact that the energy36 1of0 its emission36 is very low, and the radiation Kr 252Rb + 102�2+� →146 1T = 4.5 h has low penetration (it does not98 penetrate,640× 10 for 58 example,J 0 the human skin). In the case 85 85 → 0 − H + H He +− 21n + 3.3 MeV1 of ingestion, tritium is36 rapidly→ 37 eliminated−1β 84 fromν� the body�2 in water molecules, mainly , 2 Cf2 3 Zr + 1 Ce( +, )4 n U 1U 1 NpKr 2+ n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 Pu0 Kr Pu Am through the urinary tract. H +− H → He− + n + 17.6 MeV − n γ 252β 84 102β 1 146852 n γ 1 β Figure III-1 illustrates238 the239 procedure98 239 40for pipe239 58leakage2410 detection241 using a radiotracer and 92 �� 922 H�+� 3 H9336→ 4��He0 +94 1→n36+�⎯ ⎯3�.3 MeV94 �� 95 AmKr 1 NpRb1 + → 2+ + 0 T T= 432= 4 years.5 h detectors buried along the pipe.2 In 2Figure3 III-2, 1 it is shown the detection method using a 24185 123785 1 4 0 2− 0 9536 9337 2−→1 1 1� radiotracer pig that moves inside→→H + the H pipe. α βHeγ+ν� n + 17.6� MeV2 2 , Be + C + n( +, ) U 2 U −3 Np4 − 1 Pu Pu − Am n γ 1 9β 1 4 2β 12 0 12 n γ β 238 239 4 239→2 239 6 0 241 241 92 92 93 α 3→ 94 γ 94 95 Am�� ��Np + +�� KT �⎯⎯�T = 432�� years 7 2 The T symbol is used for241 tritium (hydrogen237 with4 2 neutrons and 1 proton) and D for deuterium (hydrogen 2 1 with 1 neutron and 1 proton).95 → 93 α �γ �2 Be + 6 × 10 C +J n + −21 9 4 12 1 4Cf 2 Zr +6 Ce0 + 4 n α 3→26KT γ 252 102 2 146 1 98 40 58 0 H + H→ He + n + 3.3 MeV 6 ×�10 J 2 2 3 1 1 1 2 0 H + H → He +− 21n + 17.6 MeV Cf Zr + Ce + 4 n 2 3 4 1 1 2521 → 1022 0146 1 98 → 40 58 0 H + H He + n + 3.3 MeV 2 2 3 1 1 1 0 H + H → 2He + n + 17.6 MeV 2 3 4 1 1 1 → 2 0
Figure III-1: Detection of leakage in a pipeline using radiotracer and buried detectors
radiation detectors
radiotracer injection
dug pit
leak
The radioisotope is injected into a section of the pipeline and subsequently the reading is made using the detectors buried in the pipe path. If there is a leak or blockage in the pipeline, the radioisotope will be trapped at the leak point and the detectors located downstream will not record any activity. Based on a document provided by Patrick Brisset (IAEA).
Figure III-2: Detection of leakage in a pipeline, using radiotracer and a detection pig
data recording
position marking
leak
fl o w
detection pig The radioisotope is injected into the pipeline and travels along the line together with the fl uid. If there is a leak, the radioisotope will accumulate in that area. The pig is then inserted into the pipeline. As it moves along with the fl uid, it records the activity and is collected at the end of the path. At regular intervals, buried sources indicate the distances traveled. Based on a document provided by Patrick Brisset (IAEA).
Gaseous fl ows The monitoring of gaseous fl ows is important in the oil industry, gas pipelines, and the chemical industry, in catalytic fractionation columns or in environments with controlled airfl ow and exhaust (Figure III-3).
27 Figure III-3: Use of radiotracer to monitor the airfl ow in an industrial environment
3 5 air inlet 1 6
exhaust
4 2 Br + n Br +
81 1 82 35Br + 0n → 35Br + γ Br Kr + + T = 35 h 82 82 81 0 − 1 82 35 36 35 Br1 + 0 n e 35 Br + 1 The tracer is inserted through theBr air → intake Kr and+ itsβ activity+ ν�→ is measured γ atT diff�2 =erent35 hpoints in the room (points 1 to 81THO 1 TDO 82 T O 6); the tracer is later eliminated82 along with82 the35 exhaust0 − 0air. Based35 on an IAEA document available at:
2 2 3 −21 1 21 31 → 42 10 1 H +Cf 1 H → 2ZrHe+ + 0 nCe++ 174.6n MeV
2252 3 1024 1461 1 1 98 1→ →402 580 0 H + H He + n + 3.3 MeV 2 2 3 1 1 1 0 H + H → 2He + n + 17.6 MeV 2 3 4 1 1 1 → 2 0
control of some physical properties of the material, such as density, mass, chemical composition, moisture content, etc. Examples of the NCS are the moderation and backscattering of neutrons, the analysis of neutron activation of immediate γ rays (prompt γ neutrons), the analysis by dual-energy γ emission measurements, and gamma backscattering, tomography or scanning.
Neutron backscattering In this technique, a fast neutron beam is directed at the material to be analyzed. When colliding with hydrogen nuclei from the material, the neutrons lose energy (they are moderated); direct shocks cause some neutrons to be reflected back and to lose some of their energy. A slow neutron detector is placed next to the source and records the backscattered neutron intensity, which is proportional to the density of hydrogen atoms in the material. By moving the source and detector along the vessel it is possible to know, for example, the levels of liquids and/or gases in columns, the separation of phases, presence of precipitation or impurities etc. The source and detector are placed on the outside of closed containers and the analysis can be performed without interrupting the processing of the material. Figure III-4 illustrates the use of neutron backscattering in an oil tank to determine its internal contents.
Figure III-4: Neutron backscattering in an oil tank
Br + n Br + 81 1 82 35 0 35 vapourBr phaseKr + + → γ T = 35 h 82 82 0 − e 1 35 → 36 1β ν� �2 THO TDO T O organic phase Li + n He +2 T 6 1 4 3 3 0 → 2 1 water T He + + T = 12.3 years 3 3 0 − e 1 1 → 2 −1β ν� �2 sludgeSe + Kr + + 76 4 79 +1 + 34 2α →NaBr36 0β ν storage tank neutron backscatter signal Br + p Kr + n 79 1 79 1 1 0 Each phase of the material can be recognized35 by the backscattered→ 36 neutron intensity, which is proportional to the density of hydrogen atoms presentKr in that phase.Br + + T = 35h Based on IAEA document, available79 at:
8 241 237 4 Transuranic elements are elements that have2 atomic numbers 1greater than that of uranium. They are 95 → 93 α γ �2 unstable and do not exist in nature, butBe can+ be obtained C + artificially n + in the laboratory. 9 4 12 1 4 2α 3→ 6 0 γ 292 KT
6 ×�10 J −21 Cf Zr + Ce + 4 n 252 102 146 1 98 40 0 H + H→ He + 58n + 3.3 MeV 2 2 3 1 1 1 0 H + H → 2He + n + 17.6 MeV 2 3 4 1 1 1 → 2 0
Br + n Br +
81 1 82 35 0 35 Br Kr + + → γ T = 35 h Br + n Br + 82 82 0 − e 1 35 36 81 1 1 82 �2 → 35 β 0 ν� 35 Br Kr +THO + TDO → T O γ T = 35 h
82 82 0 − 2 e 1 35 → 36 Li 1+β n ν� He + T �2 THO TDO T O 6 1 4 3 3 0 → 2 1 2 T He + Li++ n He + TT = 12.3 years 6 1 4 3 3 3 03 − 0 2 1 e → 1 1 → 2 −1β ν� �2 T He + Se + + Kr + T+ = 12.3 years 76 4 79 +1 + 3 3 0 − 2 34 e 36 0 1 1 → 2 −1β αν�→NaBr β �2 ν Se + Kr + + 76 Br4+ p 79 Kr++1 +n 34 2α →NaBr36 0β ν 79 1 79 1 35 1 36 0 → Br + p Kr + n Kr Br + + T = 35h 79 1 79 1 79 79 0 +1 0 35 → 36 1 36 → 35 1β ν �2 Kr Br + T + = 4.5 h T = 35h 79 79 0 +1 �2 1 36 → 35 1β ν �2 T = 4. 5 h 84
Kr 1+� n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 Kr 2 84 1 85 36 0 36 Kr Rb + +84 → T = 4.5 h Kr + n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 Kr 85 85 0 − 1 36 → 37 84−1β 1 ν� 85 �2 Americium-241 decays, by α emission:36 0 → 36 ( , ) U Kr U Rb− + Np −+ Pu T Pu= 4−. 5 h Am n γ β β 2 n γ β 238 85 239 85 239 0 − 239 241 241 92 36 92 37 93−1 94 941� 95 Am��, → ��Np + β+�� ν� �(⎯⎯,�T) =2 432�� years U U Np Pu Pu Am 241 237 − 4 − − n γ β 2 β 2 n γ 1 β 23895 239 93 239 239 241�2 241 92 →92 93 α γ 94 94 95 Beryllium absorbs theAm�� α particle ��NpBe+ +and +forms� � Ccarbon-12, + �⎯n⎯�+T =emitting432�� years a fast neutron: 9 4 12 1 241 2374 42 6 0 2 1 95 → 93 αα 3→γ KT γ�2 Be + 2 C + n +
9 4 12 1 4 26 ×�106 J 0 The energy of the emitted neutrons αis 3→aroundKT 4 MeV.γ 2 −21
Cf Zr + Ce + 4 n PGNAA 6 ×�10 J 252 102 146 1 98 40 58 0 The PGNAA (Prompt GammaH + H →Neutron He +− 21 Activationn + 3.3 MeV Analysis) is a technique used Cf Zr + Ce + 4 n 2 2 3 1 in mining or in the cement industry,1 252 1 for102 2analysis 1460 of material1 while being transported on H +98 H → 40He + n + 17.6 0MeV conveyor belts (Figure III- 5A).H + H→ He + 58n + 3.3 MeV 2 3 4 Br +1 n Br + Thermal neutron sources91 are2 placed12 below23 the01 conveyor belt. When the neutrons strike 1 1 → 812 01 82 H + H → 35He + 0n + 1735.6 MeV the material, they Brare+ absorbed n BrbyBr+ the nuclei,Kr + which+ → are excited γ andT =decay35 h to their ground 2 3 4 1 state with γ emission.81 Each1 element82182 present1 82 2 in the0 − 0material to be analyzed has γ emission with → e 1 35 0 → 3535 →γ 36 1β ν� �2 well-defi Br ned energy,Kr + whose+ intensity isT proportional=THO35 h TDO to the T Oconcentration of the element; γ 82 82 0 − detectors placed above the econveyor then1 indicate the presence and concentration of each 35 → 36 1β ν� �2 2 component (FigureTHO III-5B). TDO Neutrons T O are Livery+ npenetrating, He + Tallowing the analysis of the 6 1 4 3 entire thickness of the material on the belt.3 0 2 1 Li + n He +2 T → 6 1 T4 He3 + + T = 12.3 years Figure III-5: Prompt3 gamma0 2 neutron1 activation (PGNAA) → 3 3 0 − e 1 1 → 2 −1β ν� �2 T He + + T Se= 12+ .3 years Kr + + (A)3 3 0 detector− 76 4 79 +1 + (B) e 1 25 1 → 2 −1β ν� �342 2 36 0 Se + Kr + + α →NaBr β ν 76 4 79 +1 + 20 34 2 36 0 silicon γ-raysα →NaBr β ν Br + p Kr +hydrogen n 79 151 79 1 calcium 35 1 36 0 neutronsBr + p Kr + n → Counts
10 iron 79 1 79 Kr 1 Br + + x 30 T = 35h calcium 35 1 36 0 x 15
→ 79 79 0 + iron / aluminum 1 36 → 35 1β5 ν �2 Kr Br + + T = 35hT = 4.5 h sources 79 79 0 + 36 35 1 1� 0 1 → β ν 2 0�2 1 2 3 4 5 6 7 8 T = 4.5 h 84 1� Energy (MeV) 2 𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 Kr + n Kr 84 84 1 85 A: Equipment diagram. B: Energy spectrum in cement analysis.36 Based0 on Thermofi36 sher Scientifi c document, available 𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 Kr Rb + + → T = 4.5 h at:
Br + n Br + 81 1 82 35 0 35 Br Kr + + → γ T = 35 h 82 82 0 − e 1 35 → 36 1β ν� �2 THO TDO T O
Li + n He +2 T 6 1 4 3 3 0 2 1 → T He + + T = 12.3 years
3 3 0 − Bre+ n Br +1 1 → 2 −1β ν� �2 Se + 81 1Kr + 82 + 35Br + 0n 35Br + Br 76 Kr4+ 79+ → +1 + γ T = 35 h 34 812 361 820 82 82 35α 0→NaBr− 0 35 β ν Figure III- 6: Obtaining Cf-252Br fromKr +Pu-239, + →by e means γ ofT1 a =neutron35 h absorption and 35 → 36 1β ν� �2 - decay sequence 82 82 THO0 − TDO T O e 1 35 → 36Br + 1βp ν� Kr + n �2 THO TDO T2O 79 Li 1+ n 79 He +1 T CfCf Cf Cf Cf Cf Cf Cf Cf Cf Cf CfCf Cf Cf Cf β 35 1 → 36 0 2 6 1 4 3 249 249 249 249250250250Cf 250Cf251251251Cf 251252Cf252252Cf252Cf Cf Cf 3Li + 0n 2 He + 1T989898 989898 98 98989898 98989898 98 Kr CfCf Br Cf Cf Cf + Cf Cf Cf Cf + Cf Cf Cf→ Cf Cf Cf Cf Cf Cf CfCf T BkBk= Bk 35h Bk249 Bk 249Bk Bk250 250 251 251 252 252 CfCf 6CfCf 1 CfCf 4 CfCf 3 98 98 98 98 98 98 98 98 79T 249 249 He249 79249 249+ 25025032500250250++ 2510251 2512512512522252 2522522521 T = 12.3 Bkyears Bk Bk Bk 36 9898 3598 9898 98981989898 989898→9898 9898989898 2492491�249250249250250250 CfCfCfCfCfCfCfCfCfCfCfCfCfCfCfCfCf 249→Cf 249CfBkBkCfBk Bk Bk 250 250 Bk BkβBk Bk Bk 251 251ν 252252 9797297 979797 97 3 98398 98098−T =98984.5 h 9898 CmCm Cm 249Cm Cm 249 Cm Cm 250 Cm 250 Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm 249 249 249 249 2492502502502502502512512512512522511T252 252252 2522HeBkBk+ −Bk1Bk + e T1� = 12.973 years97 97 97 98989898 9898989898 9898989898989898→98 24998 249 98249 249 249250250250250β250 ν� 2 Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm BkBk Bk Bk BkBk Bk Bk Bk Bk 3 97397979797 97Se9709797+−97 1 Kr + 244244+244 244245245245245 246246246246247247247247248248248248249249249249 1 249 2492 CmCmCm Cm250 Cm 250 − 1 Cm CmCm� Cm2 Cm e Cm CmCm Cm Cm Cm Cm961Cm96 Cm Cm 96 96 Cm 96Cm96Cm Cm Cm 96 96 Cm Cm96Cm96 Cm Cm 96 96969696 96 969696 96 969696 96 → 9797 9797β ν� �Am2Am Am 244Am Am 244 Am Am 245Am 245 246 246 247 247 248 248 249 249 249 249 249 249250 249250250250250 CmCm 76 Se +CmCm 4 79Cm KrCm + +1 CmCm+ + CmCm96 96 CmCm96 96 96 96 96 96 96 96 96 96 979797979797979797 97 244 244 244 244 24434 2452452452452452 24624636246246246 2472470247247247 248248248248248Am249 Am 249 249 249 249 Am Am 9696969696 9696969696α84→ NaBr9696969696 9696β 2439696 24396 243ν 24396962449696244962442449696969696 CmCm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm Cm 244 244 Cm CmAm Am Cm Am Am Cm76 Am Cm 245 245 Cm Am Cm Am Cm 4 Am Am Cm Am Cm 246 246 Cm 79 Cm Cm Cm Cm247+ 2471 +95959524824895 95959524924995 9696 34 9696 2 𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾963696 96096 PuPu Pu 96 96 Pu243 Pu Pu 243 Pu 96 96 Pu 244 Pu Pu 244 Pu Pu Pu Pu Pu Pu Pu Pu Pu Pu 244 244 244 244 244245245245245245246246246246246247247247Am247Am247 248 248248KrAmAm248+α248 249→n249NaBr 249249 249Kr β ν 95 95 95 95 96969696 9696969696 96 96969696 9696 243 96243 24396 243 24396 9696244244962449624424496 9696969696 96 Pu Pu - Pu Pu Pu Pu Pu Pu Pu Pu AmAm Am Am Am Am Am Am Am Am 9595959595 849595Br959595+ 1 p 85 Kr + 239239n 239239240240240240241241 decay241241242242242242243243243243 243 243PuPuPu Pu Pu 244 36 244 Pu PuPu Pu Pu 0 Pu Pu Pu Pu 36 Pu Pu PuPu Pu Pu 94 94 Pu 94 PuPu Pu94 Pu94 94 94 94949494 94949494 94949494 94 9595 799595 1 → 79 1 239 239 240 240 241 241 242 242 243 243 243 243 243 243 243244244244244244 Kr PuPuRb + PuBrPu + + pPu Pu KrPuPu+ T n Pu=Pu 4 .5 94h 94 94 94 94 94 94 94 94 94 95959595 9595959595 95 239 239 239 239 239 24024035240240240 2412411 241241241→ 362422422422422420243243243243243 neutron absorption PuPu Pu Pu Pu Pu Pu Pu Pu Pu Pu Pu Pu 85 Pu Pu Pu Pu 94 Pu 94 85 Pu 94 94 94Pu Pu Pu94 94Pu94 094Pu94 − 94 94949494 9494949494 9494949494 β 36 239 23937 24024079−1 2412411 79242242 12431243� , →Kr9494 Br943594+β 19494+ν� → 3694(94, ) 0 94294T = 35h 239239239239239240240240240240241241241241U241 242242 242242U242243 243243 243243Np Pu Pu Am 94949494 9494949494 9494949494 949494799494 94−94799494 94 0 −+ − n γ Kr β Br + β + 2 n γ T1β = 35h 238 36239 → 35239 1β 239 ν 241 �2 241 92 ��79 92 ��79 93 0��T+ 94= 4.5�⎯ h⎯ � 94 �� 95 Am36 Np35+ +1 T = 4321� years The chain of events is very→ long, whichβ explainsν the huge2 loss of material during the 241 237 4 T1� = 4.5 h 95 93 2 2 1� obtention process. This difficulty→ in obtainingα γ and handling2 the material makes it extremely 6 Be + 1 � C + n + expensive, about US$30×10 a gram. However,284 as it is a strong neutron emitter, the amount 9 4 12 1 4 2 Kr + 6 n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 0 Kr used in measurement equipments is of theα 3 →orderKT84 of microgramsγ (μg). 84 2 1 85 Californium is unstable and decays by36Kr emission+ 0n𝐾𝐾𝐾𝐾𝐾𝐾𝐾𝐾 of36 Krα particles or by fission; in the latter Kr Rb + + → T = 4.5 h case, there is the generation of a large number846 ×�10 1of Jneutrons, 85 as in the example below: 85 85 36 0 − 0 36 Kr Rb + + → T1 = 4.5 h 36 37 −1 −21 � , → β ν� ( , ) 2 85 85 0 − U36 U37Cf − −Np1Zr +− CePu+ 4 n 1�Pu − Am n,γ → β β β ν� 2(n,γ) 2 β 238 239252 239102 239146 1 241 241 92U 9298U − 93Np40 − 9458 Pu 0 94Pu − 95Am Amn��γ H + β��NpH→ + He+β��+ n + 32�.3⎯n ⎯MeVγ�T = 432β�� years The emitted neutrons238 have239 high energy239 levels239 (on average,241 0.7 MeV,241 and can reach up 92241 �� 2 92 2372�� 93 34 �� 194 �⎯⎯� 94 �� 95 to 2.6 MeV) and must be 95thermalizedAm 1 931Np before+ 2 +hitting 0 the materialT1 = 432to be years analyzed. To achieve H→+ H → 2Heα + γ n + 17.6 MeV�2 this, the radioactive element241 is encased237 Be in+ material 4 composedC + n + of a large quantity of hydrogen 95 93 2 1� 2→ 3 9 4 4α γ1 12 1 2 atoms (ceramics or polymers).1 1 4Be→+2 2 0 6C + 0n + α 3→ KT γ Another source of neutrons used9 in PGNAA4 2 12 is americium-241,1 already described in 4 2α 3→ 6 0 γ this chapter. 2 KT 6 ×�10 J It is also possible to obtain neutrons through the fusion of deuterium and tritium, 6 ×�10 −21 J forming helium and releasing neutrons:Cf Zr + Ce + 4 n −21 252 102 146 1 98Cf 40Zr + Ce + 4 0n H + H→ He + 58n + 3.3 MeV 252 102 146 1 2 98 2 403 158 0 1H + 1H→ He + 0n + 3.3 MeV H + H → 2He + n + 17.6 MeV 2 2 3 1 1 1 0 2H + 3H → 42He + 1n + 17.6 MeV 1 1 → 2 0 2 3 4 1 Since the PGNAA measurements1 1 need→ 2 thermal 0 neutrons, these formidable energies must be moderated by a factor of the order of 109. This is done by introducing special materials consisting of light atoms (e.g. paraffin) between the source and the material to be analyzed. For the fusion reactions to occur, an accelerator is needed to provide the nuclei with enough energy to overcome the electrostatic repulsion between them. Neutron generators based on the D-T fusion are already being marketed and will provide a much more affordable and lower-cost neutron source than nuclear reactors.
31 γ Scanning The attenuation of γ rays depends on the density and thickness of the material they traverse. Therefore, it is possible to obtain information about the interior of an enclosed container using appropriate sources and detectors. In the case of γ scanning, the source is placed on one side of the container, and the detector on the opposite side; they move together allowing a scan of the entire container (Figure III-7). This technique is useful to reveal the level of the various phases present inside a distillation column, as well as defects in its internal structure. The most commonly used sources are 137Cs or 60Co; NaI(Tl) scintillators are used as detectors.
Figure III-7: Profile of an oil industry column, achieved byγ scanning
(A) (B)
source
detector collapsed trays
foam
sealing base level
transmitted radiation intensity
The γ source is placed on one side of the column, and the detector on the opposite side. Since the γ transmitted intensity depends on the density of the traversed material, it is possible to map the internal structure of the column and to detect the presence of liquid or foam. Based on A. Jaafar, Hydrocarbon Asia Jan / Feb, 62-65 (2005) available from:
Dual-energy Gamma Radiation Analysis Gamma absorption is often used to learn the shape of an object or structure inserted in a container, but the profile obtained can be compromised, if the several phases involved have very close γ attenuation indices, which makes it difficult to establish clear boundaries between the phases. This problem can be overcome by using two different γ emissions with different energies. The attenuation profile of each material depends on the energy of the radiation; combining the results obtained with radiation of different energies, it is possible to obtain more precise information about the inside of the container.
32 Dual transmission is also useful for analysis of conveyor-transported mining products, where the thickness of the material transported may hinder the transmission of radiation through higher density components.
Non-destructive tests Non Destructive Testing (NDT) refers to tests that do not change the material being analyzed. These tests often use the absorption of electromagnetic radiation or sound to obtain information about the interior of a vessel. Radiographic NDT includes imaging through γ-rays, X-rays and, more seldom, neutron beams. Recently, analysis using muons (energetic particles coming from space) has been used for the study of large structures.
X-rays and γ-scans After traversing a material, the X and γ-rays are attenuated according to the density and thickness of that material. By measuring the intensity of the radiation that has passed through an object, it is possible to transform the information obtained into images that illustrate its interior. This technique is widely used in medical applications, baggage control at airports, checking the internal structure of containers, industrial machines, sculptures, antique objects, etc. (Figure III-8). The generation of X-rays requires large-sized fixed equipment and a source of electric power. When it is necessary to make the emission source mobile, it may be more convenient to use γ sources, usually cobalt-60 or cesium-137. In addition, γ-rays are more energetic and therefore more penetrating than X-rays, providing more information in the case of very thick objects.
Figure III-8: Gammagraph of the engine gear of a turbine, showing a crack in its interior
Photo: Commissariat à l’Énergie Nucléaire - CEA-CADAM (France). Source:
In radiography and γ scanning, the information is acquired by scintillator detectors and the data is then processed in computers to provide an image of the object.10
10 Prior to the development of computational methods, the detection of X or γ-rays was done using photographic films, sensitive to radiation. Today, these films are still used in special situations.
33 In tomography, images made at different angles and positions can be grouped to provide a three-dimensional view of the object.
Other applications of ionizing radiation In addition to the examples already mentioned, new applications of nuclear energy in industry as well as in other areas are developed every day. Through γ irradiation, for example, it is possible to cure polymer materials by changing their structure (with the formation of bonds between the polymer chains).
Acknowledgments: We wish to thank researchers Rubens Martins Moreira and Jefferson Vianna Bandeira (CNEN, Brazil), João Alberto Osso Júnior, Patrick Brisset and Sabharwal Sunil (IAEA) for their collaboration in the preparation of this chapter.
34 CHAPTER IV - ENVIRONMENTAL STUDIES
The environment of coastline regions and river banks is subject to considerable modifi cation, not only as a result of climatic events but also due to human intervention, leading to sediment accumulation or erosion. The study of the transport of sediments in aqueous environments is important, for example, in the construction and maintenance of ports and dams, where it is necessary to know if the sediments are transported by the water fl ow or if they are accumulated in place, in order to optimize the design. One of the techniques for studying the movement of water and sediments in ports, dams or water bodies is the use of radioactive tracers. These can be added to samples taken in loco, which are then released and monitored as the labelled material is carried along. The labelling can be performed on the sludge in aqueous suspension, on the liquid effl uent itself or on the deposited sediments. Radiation measurements are very sensitive and therefore only minimal amounts of radioactive tracer are necessary. In some studies, the sediment is labelled with non-radioactive elements; later, samples are collected in the vicinity of the discharge site and nuclear techniques may determine the presence of the tracer element and its quantity. Another possibility is the use of sealed source techniques to provide information on the density of sediments deposited in a navigation channel or concentration of sediments circulating in suspension. The radiation will be absorbed or scattered by the sediments, indicating their characteristics. These analyses are non-destructive and do not interfere with the natural fl ow of sediments. Environmental studies can also use nuclear techniques to observe the movement of natural or man-made radioisotopes.
Radioactive tracers Use of gold as a radiotracer For studies of soil erosion and sediment movement in the ocean, in port channels or in water ways, one can label clay or fi ne sand with gold-198, a radioactive element with a relatively short half-life (2.7 days). The particles of a sediment sample are pretreated with
35 a stable gold solution in the form of auric acid, and the gold element is adsorbed on its surfaces. Then, the sample is irradiated, creating a radiotracer with properties similar to those of the sediment. The fi ner the particles, the greater the ratio between their surface and their volume and, therefore, the more effi cient the gold labelling. The labelled material is scattered in small proportions (in a concentration of parts per billion) over the surface to be studied and subsequently traced using appropriate detectors. 198Au is obtained by neutron bombardment of metallic 197Au:
Au + n Au +
197 1 198 79Au + n0 79Au + 198 198 → γ Au decays into Hg, which is stable: Au Hg 197+ +1 +198 T = 2.7 days 79 0 → 79 γ 198 198 0 − 79Au 80Hg + −1 + e+ T 1� = 2.7 days → β ν� γ 2 198 198 0 − e 1 79 → 80 −1β T ν�= 27γ days �2 The radiation is easily shielded by the surrounding material. The most abundant γ 198 1 radiation emitted during Au decay Thas� 2 energy= 27 days values around 0.4 MeV. T = 73 days β Figure IV-1 shows an example of 1the� use of radiotracers to study sediment transport 12 in sea beds. T � 2= 73 days n + U ( U ) Mo + Sn + 3 n + E 1� Figure IV-1: Acquisition1 of 235data about236 2 ∗sediment99 transport134 in1 the seabed n0 + 92U →( 92U ) → 42Mo + 50Sn + 3 n0 + E
1 235 236 ∗ 99Tc 134 1 0 92 → 92 → 42 50 0 GPS satellite 99m Mo TcTc 99m
Mo Tcposition+ Mo ⁄+ Tcdata T = 66 h
99 99m 0 − ⁄ e 1 42Mo → 43Tc + −1β + ν� T �2= 66 h 99 Tc99m Tc0+− T = 6 h e 1 42 99m→ 43 99 −1β ν� �2 43Tc 43Tc +GPS antenna T 1� = 6 h → γ 2 99m 99 Tc 43Ru + 43 + T 1�= 211 10 years → γ 2 99 99 0 − 3 e 1 43Tc → 44Ru + −1β + ν� T �2= 211 ∙10 years
99 T 99 He + 0 − + T = 12.3 3years e 1 43 3 → 443 −10β − ν� �2 ∙ e 1 radiation T1 → He2 + radiation−1β + ν� data T �2= 12.3 years 3 3 0K − Ca + + detector 1 1 2 −1 90% e � → 40 β ν�40 0 − 0 2 19K �⎯� 20Ca + −1β + 0 ν 90%T = 1.2 10 years 40 40 0 − 0 9 19 �⎯1� 20 −1β 0 ν T �2= 1.2 ∙10 years K + e Ar9 + + 1 � 10% After insertion of the radiotracer in the40 studied2 0 region,− ∙a 40detector is placed0 on the seabed and pulled by a vessel that receives the activity data. The location19K + of the−e1 active �⎯� region18Ar + is determinedγ+ 0ν by GPS. Based on IAEA document, 10% 40 0 − 40 0 available at:
99m ⁄ Mo Tc Mo Tc + + T = 66 h 99 99m 0 − e 1 42 → 43 −1β ν� �2 Mo Tc + ⁄+ T = 66Tc h Tc + T = 6 h 99 99m 0 − 99m 99 e 1 1 42 → 43 −1β ν� �2 43 43 � Tc Tc + T = 6 h → γ 2 99m 99 Tc Ru + + T = 211 10 years 43 43 1� → γ 99 2 99 0 − 3 e 1 43 → 44 −1β ν� �2 ∙ Tc Ru + + T T= 211 He +10 years+ T = 12.3 years 99 99 0 − 3 3 3 0 − 43 44 −1 e 1 e 1 → β ν� 1�2 2 ∙ −1 �2 T He + + T →= 12.3 yearsβ ν� K Ca + + 3 3 0 − 90% 1 2 −1 e 1� 40 40 0 − 0 → β ν� 2 19 20 −1 0 K Ca + + T�⎯�= 1.2 10β years ν 90% 9 40 40 0 − 0 1� 19 �⎯� 20 −1β 0 ν 2 ∙ T = 1.2 10 years K + e Ar + + 9 10% 1� 40 0 − 40 0 2 ∙ 19 −1 18 0 K + e Ar + + �⎯� γ ν 10% 40 0 − 40 Be0 + e Li + + T = 53 days 19 −1 �⎯� 18 γ 7 0ν 0 − 7 4 3 1 −1 → ν γ �2 Be + e Li + + T n=+53 daysU ( U ) Rb + Cs + 2 n 7 0 − 7 1 235 236 ∗ 97 137 1 4 3 1 −1 → ν γ �02 92 → 92 → 37 55 0 n + U ( U ) Rb + CsCs+ 2 n Ba + + Ba + 30 years 153 s 1 235 236 ∗ 97 137137 1 137m 0 − 137 0 92 → 92 → 37 55 55 0 56 −1 56 Cs Ba + + �Ba⎯⎯⎯+⎯� β ν �⎯⎯� γ 30 years 153 s 137 137m 0 − 137 55 �⎯⎯⎯⎯� 56 −1β ν �⎯⎯� 56 γ
Au + n Au + 197Au + 1n 198Au + 79 0 → 79 γ 197 1 198 79 0 79 Au Hg + Au ++ n →+ Au + γ T = 2.7 days 198Au 198Hg + 0 − + + T = 2.7 days 197 1 e 198 1 Technetium-99m used79 as→ a radiotracer80 −1β ν� γ �2 198 198 790 − 0 → 79 γ e 1 79 → 80 −1β ν� γ �2 An alternativeAu for the Hglabelling+ T of+ fine= 27+ dayssediments T is the= 2 .7use days of technetium-99m. 11 This element is commonly198 198 used in0 radiologicalT− = 27 days testing . It is obtained by the decay of 1� e 1 79 → 80 −1β 2 ν� γ �2 molybdenum-99, a fission product of Turanium-2351 = 73 days which can be chemically separated from �2 other fission products: T1 = 7327 days �2 n + U ( U1 ) Mo + Sn + 3 n + E �2 1n + 235U (236TU∗) = 7399Mo days+ 134Sn + 31n + E 0 92 92 42 50 0 → → 134 1 235 236 1∗ 99 1 0 92 92 �2 42 50 0 99Mo decays into 99mn +Tc withU → a (half-lifeU ) → of Tc 66Mo hours+ Snand+ can3 n +beE transported to the place 99m 1 235 236 ∗ 99Tc 134 1 of use, where the technetium0 92 is extracted92 from42 the Mo/Tc50 mixture:0 → Mo99m→ Tc Au + Mon Tc Au + Tc Mo 197Tc + 1 ⁄+ 198 T = 66 h 79 099m 79 99Mo 99mTc + 0 − →⁄+ γT = 66 h Mo Tc e 1 42 → 43 −1β ν� �2 99m Au99 99 HgTc99m+ Tc++0 − + T =T 6 h= 2.7 days Tc decays into Tc with half-life of 6 hours,e through1 γ emission, with energy of 42 → 43 −1β ν� �2 12 198 Mo19899m Tc099+− ⁄+ T = 66 h 140 keV : 79 80 Tc − 1 Tc + e T1 =16� h → 43 → 43β ν�γ γ �2 2 99 99m 99m 99 0 − 42 43 −1 e 1 1 43→ → 43 βγ ν� �2 �2 Tc RuTc+ Tc+T + = 27 daysT T = 211= 6 h 10 years 99Tc 9999mRu + 0 99− +1 T = 211 103 years 43 44 −1 � e 1� 1 → 43 →β43 ν2� γ 2 �2 ∙ 99 T 99He + 0 − +T = 73 days T = 12.3 years3 Because the half-life of molybdenum-99e is 10 times1 greater than that of technetium- 43 → 44 −1β ν� �2 ∙ Tc3T 3HeRu++ 0 − ++1 T T = 211= 12 .310 years years 99m, it is possible to obtain technetium� e for medical diagnostics1 up to one week after the 1 → 2 −1β ν�2 �2 99 3 n +993 U 00(−− U ) Mo + Sn + 3 n +3E arrival of the material;43 1 after442 this−−K11 time, iteCae will+ still+ be1 � 1useful as an environmental tracer, →→ ββ νν�� 2 �2 ∙ T1 99mHe235+ 90%236+ ∗ 99 134T = 121.3 years since the activity of 0the 92Tc40 Krequired 92 40Ca in+ 42 this0 −case+ 500 is much 0 lower than that required 19→ 20 → −1 0 3 3 0T�90%−⎯�= 1.2 10β-7 years ν for medical examinations1 2 (on40 the−1 order40e of 100 − times).0 1� This is due to the fact that, in → 19 β 20ν� Tc− 1 0 2 �⎯� β9 ν environmental studies, the measurementKT 1 = Ca1. 2of+ activity10 years+ is done with the detector immersed �2 99m∙ 90% 9 in the sample (the radiotracer40K occupies+ 1 e40 Mo all Tcthe0Ar −+space 0+ around the detector) whereas in 19 �2 20 ∙ −1 0 medical diagnostics the measurementT�⎯�= is 110% .2done 10 βoutside years ν the body, covering a small solid 40K + 0e− 40Ar + + 0 19 99m−1 18 0 angle. It is then possibleMo to use TcTc+ which�10%⎯�⁄+ is 9no longerγ Tν useful= 66 h in medical clinics as an 40 1� 0 − 40 0 99 1999m −21 0 − ∙ 18 0 environmental tracer.Be + e Li + �⎯+� e γ T 1ν = 53 days 42 → K43+ e−1 β ν�Ar + + � 2 Technetium-99 7decaysBe + 0intoeTc− ruthenium-99 7LiTc++ 10% + by -T emission,T ==6 53h dayswith a very long half-life 4 40 3 0 − 40 10 −1 → ν γ �2 (211,000 years) and, 7therefore,n 99m+ 0 19− veryU 7 99−low(1 Uactivity,�⎯)� 18 Rb which+γ will0Csν + not 2 n harm the environment: 4 43 343 1 1 −1 →→ ν γ γ �2�2 Be1+n + 235e U Li(236+U ∗)+ 97 Rb +β 137T Cs=+53 21 daysn 0 92 → 92 → 37 55 0 Tc7 1 Ru0235+− 7 236+ ∗ 97 T 137= 211 101 years 4 0Cs −1 92 3 92Ba + 37 + 551� Ba0+ 99 9930 years→0→− ν →γ 153 s 2 3 137Csn + U 137m( BaUe+) 0 − Rb+ +1 Cs 137+Ba 2 +n 43 →55 44 −1β 56 ν� −1 �2 56 ∙ T 1 He�30⎯235⎯years+⎯⎯ � +236 ∗ β97 ν �153T⎯137⎯�s = 12.31 yearsγ After separation of137 the Mo/Tc137m mixture,0 the− technetium137 in the form of TcO (OH)2 is 550 92 5692 −1 37 55 56 0 3 3 �⎯⎯⎯⎯�0→− → β ν �⎯⎯� γ adsorbed on a sample1 of Csthe2 sediment−1 Bato ebe+ studied. + 1� Ba + → 30 years β ν� 153 2s An example of the137 usefulness of137m technetium-99m0 − as a sediment137 tracer is the study carried 55 K 56 Ca +−1 + 56 �⎯⎯⎯⎯� 90% β ν �⎯⎯� γ out at Pampulha Lake, in Belo40 Horizonte, 40 Brazil.0 − This0 manmade lake was formed by the building of a dam in the 1950s, 19to provideT�⎯�=20 1 flood.2 10−1 βcontrol, years0 ν water supply and a new recreational 9 area for the city. The body of water 1is surrounded by gardens and urban projects designed by �2 ∙ renowned architects, landscape artistsK + ande urbanists, Ar + the + ensemble being classified as a World 10% Heritage Site by Unesco. However,40 the0 − dam 40faces silting0 problems, because the sediment brought by the water streams 19that feed−1 it� ⎯is� deposited18 γ in0 theν bottom of the reservoir. The Be + e Li + + T = 53 days 7 0 − 7 11 4 3 1 The production of technetium-99m−1 → and its useν inγ medicine are� described2 in: R. P. de Carvalho and S. n + U ( U ) Rb + Cs + 2 n M. Velasques de Oliveira, “Applications of Nuclear Energy in Health”, SBPC-IAEA (2017). Available
at:
37 normal solution would be to dredge the bottom of the lake and transport the sediments to another area. However, as the region around the dam is now completely urbanized, there is no space available for sediment deposition. The proposed alternative is to deposit the sediment at the outlet of the dam, in order for it to be carried away downstream. This would be the normal pathway of the sediments if the dam did not exist, and this material is needed to support the ecosystem of the watershed because it carries organic compounds necessary for the maintenance of aquatic life. Consequently, a study was made to determine if the sediments deposited at the outlet of the dam would be transported by the waterways. The tracer used for sediments was technetium-99m, and the water was labelled with Rhodamine WT (Water Tracer). Rhodamine is completely soluble in water and is fluorescent, being easily traced. Figure IV-2 shows this study results.
Figure IV-2: Study of the transport of sediments from the outlet of a dam in Belo Horizonte, Brazil
Au + n Au + 197 1 198 79 0 → 79 γ Au Hg + + + T = 2.7 days 198 198 0 − 79 80 −1 e 1� → β ν� γ 2 T = 27 days Normalized activityNormalized 1 �2 T = 73 days A B 1 C D �2 n + U ( U ) Mo + Sn + 3 n + E At point A, Rhodamine (blue1 dotted235 curve) 236and Tc∗ (99m)99 adsorbed134 in sediments1 (orange continuous curve) were 0 92 92 42 50 0 simultaneously injected. At points B, C and→ D, water and→ labelled sediment arrived at the same time. The coincidence in height and shape of the curves shows that the sediment Tc and water move in a similar way. The change in shape of the curves indicates the dispersion of the material in the99m watercourse; point D is located after a dead zone, where the sediment was dispersed and took longer to pass. BasedMo on: J.V.Bandeira,Tc PhD Thesis - School of Engineering, UFMG (2004). Available at:
Figure IV-3: Measurement of the tritium concentration in the vicinity of a sanitary landfill
Tritium content on surface water (Ressaca Stream, Belo Horizonte, Brazil)
Nov. 1999 (dry season)
Apr. 2000 (wet season) Tritium units (TU) Tritium
R1 R2 R3 E2 E4 Collection Station
R1: collection point at the sanitary landfill ; R2, R3, R4: collection points at the watercourse. The reduction in the activity of the tritium indicates that the slurry was diluted in the water course, but is transported by the water, causing pollution. Based on: J. V. Bandeira, PhD thesis - School of Engineering, UFMG (2004). Available at:
Tracer activation For the analysis of long-term movement of sediments, samples can be labelled with stable elements not present in the region prior to the study. The labelled sediments are released in several positions, with a different tracer being used in each place. At time intervals determined by the dynamics of the process, samples are collected and analyzed by neutron activation to determine the presence and concentration of each tracer, making it possible to determine the direction and speed of the sediment displacement. For neutron activation analysis, the sample is submitted to a neutron flux in a research reactor. The neutrons are absorbed by the sample nuclei, which emit γ radiation. The energy of this radiation has characteristic values for each element and its intensity is proportional to the concentration of the activated nuclei. Thus, the presence of the element and its concentration in the sample can be recognized.15
14 The reason for the use of tritium in such equipments is that the emission can be transformed into visible light due to a phosphorescent dye. 15 Neutron activation analysis is also described in Chapter III - Applicationβ of Nuclear Energy in Industry, in the topic: PGNAA.
39
AuAu++ nn AuAu++ Au + n Au + 197 1 198 197197 11 198198 79 0 79 7979 00 7979 → γ →→ γγ AuAu HgHg++ ++ ++ Au TT =Hg=22.+7.7 days days + + T = 2.7 days 198 198 0 − 198198 198198 00 −− 79 80 −1 e 1� 7979 8080 −−11 ee →11�� β ν� γ 2 →→ β β ν�ν� γγ 22 T = 27 days TT ==2727 days days 1 11 �2 �2�2 T = 73 days TT ==7373 days days 1 11 �2 �2�2 nn++ UU (( UU)) MoMo++ SnSnn+++3 3nnU++ EE ( U ) Mo + Sn + 3 n + E 1 235 236 ∗ 99 134 1 11 235235 236236 ∗∗ 9999 1341340 1921 92 42 50 0 00 9292 9292 4242 5050 00 → → →→ →→ Tc Tc Tc 99m 99m99m Au + n Au + Radiotracers for soil studies Mo Tc MoMo TcTc 197 1 198 Soil movement and soil erosion79 can be0 studied→ 79 by determiningγ in the upper soil layers Mo Tc + ⁄+ T = 66 h the presenceMoMo and concentrationTcAuTc+ + Hg⁄+⁄+ of+ natural + TradionuclidesT += =66 66 h h orT of the= 2 .so-called7 days FRN (Fallout 99 99m 0 − 9999 99m99m 00 −− 42 43 −1 e 1 Radionuclides).4242 Some1984343 of −the−11981 FRNs ee 0 are− formed11 → in the upperβ atmosphereν� by �cosmic2 rays →→ 79 β80β ν�ν� −1 e�2�2 Tc Tc +1� T = 6 h bombardment. TcOthersTc comeTc→Tc++ from nuclearβ TT testsν�==6 6that hγ h occurred between2 the 1940s and 1960s, 99m 99 99m99m 9999 T = 2743 days 43 1 or from accidents4343 at nuclear4343 power plants,11 when fission/fusion→ γ products spread�2 through the →→ γγ �2�2 atmosphere across the globe and fell on the Earth’s surface. 1� TcTc RuRu++ ++ AuTTTc+ 2 ==n211 211Ru 10 +10Au years +years + T = 211 10 years An example of natural radionuclideT is = potassium-40,73 days which exists in a small proportion 197 99 1 99 198 0 − 3 9999 16 9999 00 −− 43 44 33−1 e 1� in nature4343 .44It44 has two−−11 majoree decay 79routes,11�1� 0→both with79 theβ sameν� half-life: 2 ∙ →→ ββ ν�ν� 2�T22 →He∙∙ + γ+ T = 12.3 years TT HeHe++ +n+ + U ( UTT) == 1212Mo.3.3 years +years Sn + 3 n + E Au Hg + 3+ +3 0 − T = 2.7 days 33 33 00 −− 1 2 −1134 e 1 1 ee235 236 ∗11 99 1 �2 11 22 198−−11 0 19892 092− �2�→2 42 β50 ν� 0 →→ 79ββ ν�ν�80 → −1 →e 1 KK → CaCa++ +β+ ν � γ K Ca�2 + + 90% 90%90% Tc 40 40 0 − 0 4040 4040 0 0 −− T00 = 27 days19 20 −1 0 1919 2020 −−11 00 99m T�⎯�= 1.2 10β years ν T T� �⎯ �⎯ � = = 1 1. 2. 2 10 10 β β years years ν ν 1 Mo Tc 9 99 �2 1 11 �2 �2�2 ∙∙ T = 73 days ∙ KK++ eMoe ArArTc+++ ++ ⁄+ K + Te = 66 hAr + + 1 10% 10%10% �2 40 0 − 40 0 4040 9900 −− 4099m40 0 0−0 n + U ( U ) Moe 19+ −Sn1 1+ 3 n +18E 0 1919 −−4211 ��⎯→�⎯� 181843 γγ−1β00νν ν� �2 �⎯� γ ν 1 235Tc 236Tc∗+ 99 134T = 6 1h 0 92 92 Be +42 e 50Li + 0+ T = 53 days BeBe40++ ee LiLi++ ++ TT ==5353 days days 40 The K decay is used 99mfor dating→ 99 rocks,→ by the determination of Ar concentration: 43 43 7 0 − 71� 77 00 −− 77 → 4 γ Tc− 1 3 2 1� in the 4molten4 −−1 1magma33 material, the argon11�� gas formed→ by νthe γdecay has escaped;2 after →→ νν γγ 22n + U ( U ) Rb + Cs + 2 n nn++ UU Tc (( UURu)) + RbRb++ 99m CsCs ++ 2 2nn T = 211 10 years solidification, this gas was trapped in the1 rock235 and 236its ∗concentration, 97 137 compared1 to 11 235235 236236 ∗∗ 9797 137137Mo Tc 11 99 99 0 − 0 92 92 337 55 0 40 potassium, 00 indicates 929243 → →the 92time9244 →elapsed→ 37−371 since55e55 the rock00 formation.1→� The→ determination of Ca CsCs →BaBa++ +β+ ν� CsBaBa++ 2 Ba +∙ + Ba + T He + + ⁄ 30 years T = 12.3 years 153 s concentration3030 isyearsyears less convenient Mo becauseTc +153 153 calcium137ss + may have137mT other= 66 0origins h− besides137 potassium 137137 137m3137m 3 00 −−0 − 55137137 56 −1 56 decay. Once5555 the age1 of5699 56 the2 rock−−199m1 −is1 determined,0e − 56 56�⎯ ⎯it⎯ ⎯is� possible1 to inferβ ifν there�⎯⎯� was erosionγ ��⎯⎯⎯⎯⎯�� → ββ β νν��⎯ν⎯��⎯� e γγ �2 1 42 → 43 −1β ν� �2 and sediment transport . Tc K Tc +Ca + + T = 6 h 90% Another example of a naturally99m 40 99occurring40 0 radionuclid− 0 e is beryllium-7. It originates 19 20 −1 01 43 �43⎯� β ν�2 in the upper atmosphere through the→T collision= 1.2γ of 10 atoms years of oxygen or nitrogen with protons, 17 7 79 coming from the solarTc wind Ru.+ Be 1decays+ into Li Tthrough= 211 electron 10 years capture, emitting γ �2 ∙ radiation with energy99 of 48099 keV: 0 − 3 43 44 K−+1 e e Ar + 1�+ → β ν�10% 2 ∙ T He +40 +0 − 40 T 0 = 12.3 years 19 −1 18 0 3 3 0 − �⎯� γ ν e 1 1 Be→+2 e −1β Li +ν� + T�2 = 53 days K Ca + + 7 0 − 7 4 90%3 1 −1 40→ 40ν γ 0 − 0 �2 n + 19U T�⎯�( =20U 1.)2 10−1βRb years+ 0 ν Cs + 2 n Because this radionuclide1 235penetrates236 a ∗maximum 97 of137 2 cm in 1the soil, the determination 9 0 92 →1 92 → 37 55 0 of the beryllium-7 activityCs can indicate �2 Ba if+ there ∙ was+ a recent Ba erosion+ or soil contribution from another region. 30 yearsK + e Ar + 153+ s 137 137m 10% 0 − 137 The cesium-137 is 55a fallout�⎯⎯⎯40⎯� radionuclide560 − − 140β of anthropogenicν �⎯⎯�0 56 γ origin, coming from 19 −1 �⎯� 18 γ 0ν uranium-235 fission: Be + e Li + + T = 53 days 7 0 − 7 4 3 1 −1 → ν γ �2 n + U ( U ) Rb + Cs + 2 n 1 235 236 ∗ 97 137 1 0 92 → 92 → 37 55 0 Cs Ba + + Ba + 30 years 153 s 137 137m 0 − 137 55 �⎯⎯⎯⎯� 56 −1β ν �⎯⎯� 56 γ 16 The natural isotopic abundance of 40K is of 0.012%. 17 This process is called spallation: when the particle strikes on a nucleus, it rips out part of its components in the form of smaller nuclei.
40
Au + n Au + 197 1 198 79 0 → 79 γ Au Hg + + + T = 2.7 days 198 198 0 − 79 80 −1 e 1� → β ν� γ 2
T = 27 days 1 �2 T = 73 days 1 �2 n + U ( U ) Mo + Sn + 3 n + E 1 235 236 ∗ 99 134 1 0 92 → 92 → 42 50 0 Tc 99m Mo Tc
Mo Tc + ⁄+ T = 66 h 99 99m 0 − e 1 42 → 43 −1β ν� �2 Tc Tc + T = 6 h 99m 99 43 43 1� → γ 2 Tc Ru + + T = 211 10 years 99 99 0 − 3 e 1 43 → 44 −1β ν� �2 ∙ T He + + T = 12.3 years 3 3 0 − e 1 1 → 2 −1β ν� �2 K Ca + + 90% 40 40 0 − 0 19 T�⎯�=20 1.2 10−1β years0 ν 9 1 �2 ∙ K + e Ar + + 10% 40 0 − 40 0 137Cs was released into the19 atmosphere−1 �⎯ �during 18 nuclearγ 0ν tests or in accidents on fission reactors. Its most likelyBe decay+ eroute is:Li + + T = 53 days 7 0 − 7 4 3 1 −1 → ν γ �2 n + U ( U ) Rb + Cs + 2 n 1 235 236 ∗ 97 137 1 0 92 → 92 → 37 55 0 Cs Ba + + Ba + 30 years 153 s 137 137m 0 − 137 55 �⎯⎯⎯⎯� 56 −1β ν �⎯⎯� 56 γ
The γ radiation energy is 0.66 MeV.
In Germany, the topsoil was contaminated with 137Cs from the Chernobyl nuclear power plant accident in 1986. This radioelement is absorbed only by shallow-rooted plants, not deep-rooted trees. The hunting of wild animals, such as deer, is banned during the fall / winter, because during these seasons the animals find no tree leaves and feed on grass and mushrooms. Their flesh is thus contaminated with cesium and should not be consumed. However, since cesium is not metabolized by the animals and is eliminated through their feces, they may be hunted and consumed at other times of the year.
Use of sealed sources
γ Transmission Analysis The transmission of γ radiation depends on the density of the material it crosses. This fact allows the characterization of the sediments suspended in water at ports, dams or navigation channels. Generally, the γ source for transmission measurements is cesium-137, whose production and decay route have been described earlier in this chapter. Its long half- life (30 years) makes it convenient for use in sealed sources.
γ Backscattering γ analysis can be done even when only one side of the object is available; in this case, source and detector are side by side and one analyzes the γ rays backscattered due to the Compton effect18. The intensity of the backscattered beam depends on the density and thickness of the material, and on the scattering angle. This technique is very useful for the study of sediment concentration in ports, rivers, navigation channels. The analyses can be done at a fixed point, by studying the variation of sediment concentration over time, or by measuring the vertical profile of this concentration. Figure IV-4 shows the schematic of a backscatter probe.
18 In the Compton effect, a photon collides with the electron of an atom, behaving like a particle; the exchange of energy between them causes the photon to be scattered with an energy different from the initial one and that depends on the scattering angle. Compton scattering is also described on Chapter I – Fundamentals.
41 Figure IV-4: Schematic of a γ backscatter probe.
pressure sensor
scintillation detector shielding
radioactive source
ballast
The radioactive source (usually cesium-137) emits in all directions; the radiation that would directly fall on the detector is shielded by a tungsten cone, and only the radiation backscattered by the liquid medium can reach the detector. The ballast at the bottom of the probe allows it to be placed at the desired depth, which can be determined by the pressure sensor. Based on: A. Caillot et. al.: A New Nuclear Density Gauge to Measure Directly High Turbidities in Muddy Areas; available at:
Meteorological studies Atmospheric dynamics can be studied using beryllium-7 as a radiotracer. As described earlier in this chapter, this radioelement is formed in the upper atmosphere by spallation of oxygen or nitrogen nuclei; it adheres to aerosol particles19 which are carried by the wind and fall on the ground due to gravity and rains. The analysis of the presence of 7Be in the lower atmosphere can give information about air movements. The CTBTO (Comprehensive Nuclear Test Ban Treaty Organization) is a UN organization that monitors worldwide nuclear explosions. It has a global network of detectors that continuously analyze the composition of the air and register the occurrence of seismic events. This network can be used for other studies and researches. The detectors indicate, among other factors, the concentration of 7Be in the atmosphere. It is known that the terrestrial atmosphere is formed by convection cells, where the less dense warm air rises to the upper atmosphere, while cooler, denser air goes down, closer to the ground (Figure IV-5). Regions between two cells are called convergence zones. There is a convergence zone near the Equator, two in the temperate zones (one in each hemisphere), and two in the polar regions.
19 Aerosols are fi ne particles, solid or liquid, that exist in suspension in a gas.
42 Figure IV-5: Earth’s atmospheric convection cells
convergence zones
convection cells
The region between two cells is called a convergence zone. Adapted from: L. Terzi, M. Kalinowski, Journal of Environmental Radioactivity 178-179, pg.1-15 (2017), available at:
In the convergence zones at the Equator and at the Poles, the direction of air circulation causes it to rise; in the temperate regions, inversely, we have air that descends (Figure IV-6). As the 7Be is formed in the upper atmosphere, its concentration is expected to be higher in the convergence zone of the temperate regions and lower in the convergence zones of the Equator and the Poles, compared to the concentration in other regions.
Figure IV-6: Circulation of air in the convergence zones
upwards downwards air flow air flow
upwards air flow
Pole Temperate Equatorial zone zone
Adapted from: L. Terzi, M. Kalinowski, Journal of Environmental Radioactivity 178-179, pg.1-15 (2017), available at:
The convergence zones move slightly north or south, depending on the seasons. By measuring the seasonal variation of the concentration of 7Be, it is possible to determine the position of the convergence zones and their movements and associate the movement with climatic characteristics (summer, winter, rainy or dry seasons, presence and intensity of the El Niño phenomenon, occurrence of monsoons, etc).
Acknowledgments: We wish to thank the collaboration of the researchers Rubens Martins Moreira and Jefferson Vianna Bandeira (CNEN, Brazil), João Alberto Osso Júnior, Patrick Brisset and Sabharwal Sunil (IAEA) in the preparation of this chapter.
43
CHAPTER V - APPLICATIONS OF NUCLEAR ENERGY IN FOOD PRODUCTION
The world’s population has grown exponentially, consequently increasing the demand for food. Nuclear energy can be used in the agriculture and livestock industries, enhancing food production: in soil study and preparation, in choosing the best seeds and plant species suited to the climatic conditions, in reducing agricultural pests, in preserving the health of livestock, etc. In this chapter, we will look at some examples of nuclear energy applications.
Soil studies When preparing a land for farming, it is important to know if the soil is subject to movement or erosion, its humidity, its need for fertilization, among other factors. Nuclear techniques for soil studies include analysis of radiotracer elements or stable isotopes and the use of neutron probes. Radiotracers, whether natural or of anthropic origin, as well as stable isotopes of carbon and nitrogen (13C and 15N), can be used to detect movement of the topsoil, as a sign of erosion or accumulation of material coming from other regions20,21. The isotopic composition of 15N is further used in soil fertilization studies. We know that plants need nitrogen for their development, which is an important element in the formation of chlorophyll. Through measurements of the isotopic composition of 15N in the plant and in the soil, it is possible to determine if the element is absorbed mostly from the soil or from the air. Based on the results of these studies, it is possible to determine if it is desirable to increase the concentration of nitrogen in the soil, either through the use of plants or bacteria that help fi x the element, or by artifi cial fertilization.
20 The use of radiotracers in the oil industry and in the study of sediment transport was described in Chapters III - Application of Nuclear Energy in Industry and IV - Environmental Studies. 21 The stable isotopes and the isotopic composition of some elements were detailed in Chapter II - Stable Isotopes.
45 Neutron probes are used to determine soil moisture, based on the interaction of fast neutrons with water. The source of neutrons used in these probes is an americium / beryllium pellet22. Americium-241 is an α emitter:
Am Np + + T = 432 years 241 237 4 2 1 95 → 93 α γ �2 Be + C + n + Beryllium absorbs anAm α particle, 9Np forming+ 4 + carbon-12 12 1 Tand= emitting432 years a fast neutron: 4 2α → 6 0 γ 241 237 4 1 KT 2 2 1 95 → 93 α γ �2 Be + C + n + � 9 4 12 1 4 B + 2αn 1→ 6Li + 0 + γ 2 KT 10 1 7 4 The energy of the emitted neutrons5 is0 on average3 2 4 MeV. The pellets are encapsulated . →� α γ with aluminum, Am lead or Npiron+ to shield+ Rnthe γ emission.T =Po432+ years 3 8 days In contact241 with the237 earth, 4the neutron222B + fluxn collidesLi218+ +with4 the soil elements and exchanges 95 93 2 86 1 84 2 → α 10γ Co1�⎯+⎯⎯ ⎯�n7� 2 4Co α energy with their nuclei. IfBe the+ masses 5 ofC the+0 nucleusn + 3 and2 the neutron are similar, the exchange 59 . →1 60 α γ of energy is more effective,9 and4 the neutrons12Rn27 1 are0 thermalized,Po27 + that is, they have their energy Co 4 Ni2 + 6 + 308 days+ → T = 5.3 years reduced to values of the order ofα 1→222KT . γ218 4 60 60 2086− 84 2 Co�⎯e+⎯⎯ ⎯�n Co α 1 Hydrogen, present27 in→ water28 molecules,−1β ν is γthe only element�2 with low atomic weight � 59 1 60 found in significant quantities in typical27 soils.0 Thus,27 the measurement of thermal neutrons Co Ni + + + → T = 5.3 years is related to the concentrationB + ofn water Li in+ the soil+ and can determine the amount of artificial 60 60 0 − 27 10 28 1 −1 7 4e 1� irrigation required. →5 0 . → β3 ν2α γγ 2 The slow neutron fluxRn is measured, Po for+ example, by Geiger-Müller (GM) detectors23, 3 8 days 222 218 4 using BF gas, with boron86 enriched with84 boron-10,2 which absorbs slow neutrons and emits 3 Co�⎯+⎯⎯ ⎯�n Co α α particles and γ rays: 59 1 60 27 0 27 Co Ni + + + → T = 5.3 years 60 60 0 − Am e Np + + 1 T = 432 years 27 → 28 −1β ν γ �2 241 237 4 2 1 95 → 93 α γ �2 Be + C + n + The GM counters determine the9 intensity4 12but not1 the energy of the emitted ionizing radiation. 4 2α 1→ 6 0 γ 2 KT The advantage of measurements made with neutron probes is that they do not depend on the temperature and atmospheric pressure of� the site, and are little affected by the salinity, chemical composition of the soil or theB + type n of bindingLi + of+ the water molecules with the soil particles. In addition, the equipment,10 consisting1 7 of the4 source and the detector, is compact 5 0 . → 3 2α γ and can be easily transported. Rn Po + 3 8 days 222 218 4 86 �⎯⎯⎯⎯� 84 2α Induced mutation Co + n Co 59 1 60 27 0 27 Mutation is a modificationCo Ni + observed+ +in the → DNA ofT a living= 5.3 yearsorganism. DNA is a 60 60 0 − double strand of nucleotides, bound by sugarse and phosphates.1 The nucleotides can have 27 → 28 −1β ν γ �2 four types of nitrogenous bases: adenine, thymine, cytosine and guanine, identified by the initials A, T, C and G. These bases form A-T or C-G pairs. The functional part of DNA is the gene, which consists of special sequences of hundreds or thousands of A-T or C-G pairs.
22 The Am/Be source was described on Chapter III - Application of Nuclear Energy in Industry. 23 The Geiger-Müller detectors were described in Chapter I - Fundamentals.
46 A mutation can be a point mutation, when there is a single change of nitrogenous base; it can insert or remove bases; or can reverse the order of the bases. The phenomenon was first described by the Dutch botanist Hugo de Vries in the early twentieth century, when he observed mutations in primrose plants. Induced mutation can be done through a chemical treatment (chemical agents) or irradiation (physical agent) of the seeds. The resulting mutations could have happened naturally, however would have taken much longer, perhaps millions of years. Induced mutation can be used to create, for example, plant species which are climate- resistant (drought, saline soil, excessive rainfall, etc.) or more nutritious. Induced mutation in decorative plants may result in flowers with different colors (Figure V-1). The technique, therefore, accelerates the natural evolution of plants. As induced mutations occur at a much higher speed than spontaneous mutations, they increase the likelihood of obtaining desired plant characteristics.
Figure V-1: Flowers of different colors, obtained through ion irradiation of petunia seeds
A B C D
E F G H
A: Natural color; B-H: Mutant colors. Source: Y. Hase et. al.: Plant Biotechnology 27, 99–103 (2010)
Rice is an excellent example: in 100 million years, Nature created 140 thousand different rice genotypes24; using radiation, it is possible to create new genotypes in less time: from the beginning of the research until results are obtained, the elapsed time is on average 10 years. Induced mutation is achieved by the exposure of plant seeds or tissues to γ / X radiation, electron or ionic beams25. The mutation rate is low (usually between 1% and 10%). After irradiation, the plants are cultivated and those with interesting characteristics are chosen for large-scale reproduction. Induced mutation was first reported in 1927, using a radon a source26. The first applications of induced mutation occurred in 1936 in Indonesia (tobacco), in 1949 in the Netherlands (tulips), in 1950 in Sweden (mustard) and in Germany (beans). Today, the technique is used worldwide to optimize species suitable for feeding people or livestock. There is a frequent confusion between induced mutation and genetically modified Am organisms Np + (GMOs).+ GMOsT are= obtained432 years by introducing genes from one species in the DNA 241 237 4 2 1 95 →chain93 of anotherα γ species. The�2 studies are recent and there is still no confirmation about the absenceBe + of side C effects+ n + from the consumption of these organisms. On the other hand, 9 4 12 1 4 2 6 0 α 1→ KT γ 24 2 The genotype is the set formed by the genes of an individual. 25 γ sources are being� replaced by X-rays, electron beams or ion beams, as these radiation sources stop emissionB + whenn they Li are+ switched+ off, while theγ sources emit continuously. 26 Radon10 is an1 α emitter;7 it4 belongs to the decay chain of uranium-238: 5 0 . → 3 2α γ Rn Po + 3 8 days 222 218 4 86 84 2 Co�⎯+⎯⎯ ⎯�n Co α 47 59 1 60 27 0 27 Co Ni + + + → T = 5.3 years 60 60 0 − e 1 27 → 28 −1β ν γ �2 induced mutation causes changes in the genes that already exist in the species, silencing some of them and awakening others, thus changing some characteristics of the species. Induced mutation has been used for almost a century, and there are no reports of problems caused by the consumption of food obtained by this technique.
Sterile insect technique Ionizing radiation may cause mutations, as described in the previous item, or cause some modifi cation in living beings, depending on the irradiation dose. The ability to sterilize insects with radiation is the basis for the application of the Sterile Insect Technique (SIT), which aims to develop methods of control or suppression of pests in agriculture, and of insects that cause diseases in humans or animals. The technique has been used for more than 50 years for the control of fruit fl ies and tsetse fl ies27. Today, it is widely used for the control of agricultural pests (fruit fl y, Mediterranean fl y), cattle breeding (stable fl y, tsetse fl y, screwworm fl y) and mosquitoes that transmit diseases to humans and animals. In this technique, a great number of insects are laboratory bred; males and females are separated, usually at the pupa stage, and females are discarded. The male pupae are irradiated with proper doses, resulting in sterile adults that did not lose their mating ability. Sterile insects are released in nature, where they compete with wild males; the females that mate with the irradiated insects do not generate descendants, thus contributing to the control of the population of undesirable insects in the region. The life cycle of an insect is shown in Figure V-2.
Figure V-2: Life cycle of an insect
adult female laying eggs
merging adult
larva pupa
Figure V-3 shows the development of SIT for fruit fl ies. The male and female pupae have diff erent color (white or black females, depending on the species, and brown males); they can be separated by an optical separator, described in Figure V-4.
27 The sterile insect technique is also discussed in: R.P.de Carvalho and S.M. Velasques de Oliveira - “Applications of Nuclear Energy in Health” - SBPC, IAEA (2017) - Available at:
48 Figure V-3: Fruit flies bred in captivity (A) © Regina Carvalho P.
(B) © Regina Carvalho P.
(C) © Regina Carvalho P.
B
A: The eggs are collected in a container placed under the cage. B: The larvae are bred in trays containing carbohydrates and yeasts. C: Male and female pupae have different colors and can be separated. Photos taken at the IAEA laboratories, Seibersdorf, Austria.
49 Figure V-4: The process of separating male and female pupae of fruit fl ies 1
2
4 3 4 5 6 4 5
4 7
9 8
The pupae are introduced into the separator (1) and a vibrating platform (2) causes the material to fall as a single layer (3). The pupae are illuminated (4) and the image is captured by cameras (5), which send a signal to the processing system (6); this system has previously been programmed to recognize white or dark objects. When a clear (female) pupa is detected, the processor sends an order to a compressed air gun (7), which directs the pupa to the discarded material container (9). Brown pupae (males) are collected separately (8). Based on a Color Sorter Group document - available at:
Male pupae are irradiated with cobalt-60, which is γ emitter, into a gammacell (Figure V-5), and incubated. In the research laboratories, after the emergence of the adult males, they are placed in contact with wild insects, in controlled environments that simulate the natural environments (Figure V-6), to verify the interaction between the insects.
Figure V-5: Equipment for γ irradiation (gammacell)
(A) (B)
shielding (concrete) sample irradiation container Co-60 bars surrounding the container © Regina Carvalho P. 6 A: External aspect; photo taken at the IAEA laboratories, Seibersdorf, Austria. B: Internal layout.
50 Figure V-4: The process of separating male and female pupae of fruit flies Figure V-6: Irradiated male insects are placed in contact with wild populations in controlled environments to verify the interaction between them © Regina Carvalho P.
Photo taken at the IAEA laboratories in Seibersdorf (Austria).
A similar procedure is used for the control of mosquitoes that transmit diseases among humans and animals (Figure V-7). Mosquito male pupae are smaller than female pupae, and can be separated using mechanical methods.
The pupae are introduced into the separator (1) and a vibrating platform (2) causes the material to fall as a single layer Figure V-7: Aedes aegypti breeding (3). The pupae are illuminated (4) and the image is captured by cameras (5), which send a signal to the processing system (6); this system has previously been programmed to recognize white or dark objects. When a clear (female) pupa is detected, the processor sends an order to a compressed air gun (7), which directs the pupa to the discarded Feed port of material container (9). Brown pupae (males) are collected separately (8). the fecundated Based on a Color Sorter Group document - available at:
male pupae
larvae A: The mosquitoes are bred in the IAEA laboratories in 6 Seibersdorf (Austria); B: The eggs are collected at the bottom A: External aspect; photo taken at the IAEA laboratories, Seibersdorf, Austria. B: Internal layout. of the cage; C: Female and male pupae are separated between
two vibrating plates. © Danilo Carvalho O. (C)
51 For other insects, the technique may vary depending on the characteristics of each insect. The separation between males and females of the Mediterranean fl ies, for example, is done by raising the temperature to 34ºC, which kills the female eggs. This mechanism is simpler and more accurate, since it allows the elimination of females in the egg phase, simplifying the insect breeding process. Other insects are very resistant to radiation sterilization, such as butterfl ies. However, if the dose is too high, it can kill the insects. On the other hand, if it is too low, it does not sterilize the insect, but will result in sterile off spring in the second or third generation. The release of sterile adults must be done weekly, in numbers ranging from 15 million to 1 billion insects per week, depending on the type of insect, the area to be covered and the degree of infestation. For use in agricultural areas, batches of insects are cooled to 4ºC during transport and stored in a state of latency. The release is done by small airplanes; as they fall, the insects warm up and regain vitality. In urban areas, the release is done on land. SIT has been quite successful in insect control, and is generally part of a series of techniques used simultaneously; its success depends on involving the whole community in a collaborative eff ort.
Food irradiation After growing and harvesting vegetables or obtaining animal products, it is necessary to ensure their conservation during storage and transport, until their delivery to the consumer. The techniques of food irradiation aim at their decontamination, by eliminating bacteria and fungi, controlling pests such as insects, that may become installed in the fruits and seeds, or prolonging their shelf life, inhibiting sprouting. These techniques are applied to grains, herbs, some fruits and vegetables or to meats. Irradiation can also be performed on prepared meals. This is particularly useful in the case of meals for astronauts, in hospitals or for sending to disaster sites (impacted by earthquakes, fl oods). In this case, the food is packed with a material that does not deteriorate when subjected to radiation; the packaging prevents the food from coming in contact with microorganisms and being recontaminated. The packaging of irradiated food carries an international logo, named Radura (Figure V-8).
Figure V-8: Radura, the international symbol used to identify food treated with ionizing radiation
52
Am Np + + T = 432 years 241 237 4 2 1 95 → 93 α γ �2 Be + C + n + 9 4 12 1 4 2 6 0 α 1→ KT γ Am Np + + 2 T = 432 years
241 237 4 2 � 1 95 → 93 α γ �2 Usually, the γ irradiation is carriedBeB + +out n with Licobalt-60,C++ n++ obtained by bombarding cobalt-59 (stable) in a nuclear reactor: 9 4 12 1 104 12α → 7 6 4 0 γ 5 0 . →1 3 KT 2α γ Rn 2 Po + 3 8 days 222 218 4 86 � 84 2 Co�⎯+⎯⎯ ⎯�n Co α B + n Li + + 59 1 60 10 27 1 0 7→ 27 4 Co Ni + 5 + 0 . + → 3 2α γT = 5.3 years 60 60 0 − Rn Po + Cobalt-60 is 27an energetic28 γ emitter−1 (1.33e8 days MeV and 1.1 MeV,1� in equal proportions): → 222β ν γ 218 4 2 86 84 2 Co�⎯+⎯⎯ ⎯�n Co α 59 1 60 27 0 27 Co Ni + + + → T = 5.3 years 60 60 0 − e 1 27 → 28 −1β ν γ �2 However, the use of γ sources brings safety problems in the transport and handling of radioisotopes and is being replaced by X or ion beam irradiation, which only radiate when in operation. The development of new manufacturing technologies is leading to smaller and portable devices.
Livestock The production of food of animal origin (milk and meat) encounters problems related to parasitic insects such as screwworm fly, cattle fly or tsetse fly and with diseases that affect entire herds, such as hoof-and-mouth disease, rinderpest, swine fever. Control of parasitic insects can be done through the sterile insect technique described earlier in this chapter. A successful case in SIT application was the eradication of the screwworm flies in North America. This fly lays its eggs in the wounds of the animals, where the larvae feed on their blood and flesh. Infestation in herds leads to a large loss of livestock and a low production of meat or milk. In 1965, the technique started to be used in Florida, along with other techniques for eliminating insects and educating the population. Over the next 10 years it was extended across all southern states to the west coast of the United States. In 1981, the screwworm fly was considered extinct in the United States, occurring only in isolated cases when pets or racehorses traveled with their owners to Central and South America, where they were contaminated. In each case, a local control was carried out with sterile insects for 6 months. In 1976 the technique was implemented in Mexico and later extended throughout Central America. Since 2000 there has been a sanitary barrier in the Panama Canal, with weekly release of sterile insects, to avoid recontamination by insects coming from South America.
Acknowledgments: We wish to thank Carlos E. Caceres, Danilo O. Carvalho, Jorge Hendrichs, Carl M. Blackburn, Zhihua Ye and Fatma Sarsu (IAEA) and Antonio Costa de Oliveira (Univ. Federal de Pelotas, Brazil) in the preparation of this chapter.
53
CHAPTER VI – STUDY AND PRESERVATION OF CULTURAL HERITAGE
Nuclear techniques are useful tools in the preservation and study of tangible cultural heritage. For example, γ irradiation can be used to kill fungi, microorganisms or insects in books and ancient works of art. The applied dose can be calculated to eliminate unwanted organisms without aff ecting the material to be preserved. The composition of inks, ceramics or metal alloys used in past eras can be revealed using the neutron or γ-ray analysis techniques described in Chapter III - Application of Nuclear Energy in Industry. Gammagraphy, also described in the same chapter, is used to show the interior of statues and other works of art. In addition to these, the carbon-14 dating technique is used to learn the age of fossils; and a new technique of non-destructive analysis was recently proposed for the study of large ancient buildings: the muography.
Dating with carbon-14 14C is formed in the upper atmosphere by the bombardment of nitrogen-14 by cosmic rays:
N + n C + p 14 1 14 1 7 0 6 1 → 14C is absorbed byC living N + organisms + as CO , in Tthe =same5,730 way years as the stable isotopes 14 14 0 −N + n 2C + p 12 13 6 7 14 1 - C and C. It is unstable, and transforms−1 into N by� 2 decay : → β14 ν�1 14 1 7 0 → 6 1 C N + + T β= 5,730 years 14 14 0 − 6 7 1 → −1β ν� �2 55 The carbon-14 isotopic ratio is constant as long as the organism is alive (on the order of 1012 atoms of 12C for every 14C atom), but it decreases after death, as 14C decays into 14N and there is no further absorption. Thus, by determining the 14C/12C ratio, it is possible to infer how long ago the organism died. In general, the assumption is that the isotopic carbon ratio in the atmosphere did not vary over time. The earliest radiocarbon dating was done in the 1940s, by counting the - emissions of the 14C. However, due to the small proportion of this isotope in a carbon sample, large amounts of material and long counting times are required. For example, a sampleβ of 1 g of “present” carbon has on average 15 emissions per minute; in order to obtain accurate information, it would be necessary to count for at least 12 hours. For old samples in which part of the 14C has already decayed, counting may take weeks or months. Currently, the mass spectroscopy technique described in Chapter II - Stable Isotopes can be used to determine the ratio of 14C in the total carbon of a sample. The analysis can be done quickly (10 to 30 minutes), and very small samples are used (~ 0.1 mg), which reduces the damage caused to the piece studied. Carbon-14 can therefore be used to determine the age of any old object containing carbon of organic origin, such as bones of humans or animals, shells, food remains in prehistoric vessels, paper, cloth, straw, material of plant origin found in old bricks etc.
Muography Muons (pronounced ‘mee-ons’) are negative particles, similar to electrons, but with a mass about 200 times greater than that of the electron. They are formed in the upper Earth atmosphere by collisions between the cosmic rays and the molecules of the atmosphere. Muons interact very little with matter and reach the Earth’s surface with high energies. When traversing large volumes, they lose energy proportionally to the density of the material and the distance traversed. Due to the fact that the flow of muons is intense across the surface of the globe, they can be used to examine the interior of large structures (mountains, large buildings, etc.). Muography is similar to γ scanning or radiography, with the advantage that the radioactive source exists permanently anywhere on Earth. Detection of muons is done by emulsion films, and can be confirmed with scintillation detectors. An example of application of muography is the study of the interior of the Vesuvius volcano. Through the obtained images, one can observe the formation of pockets of lava and infer the occurrence of future eruptions. In another recent study, the structure of the interior of the pyramid of Khufu, Egypt, was investigated. From the measurements, it was possible to determine the existence of an empty space, until now unknown, inside the pyramid (Figure VI-1).
56 Figure VI-1: Flow of incident muons, as a function of the position of the detectors, in the Khufu pyramid (Egypt)
B A muon flux
-0.4 -0.2 0.0 0.2 0.4 0.6
tg
The orange continuous curve shows the experimental data.θ The blue dotted line shows the expected flow, taking into account the known structure of the pyramid. The increase in flow in region A is due to the presence of a known tunnel (absence of material that could attenuate the flow). Region B presents an unexpectedly high value for the flow, indicating the existence of a void, hitherto unknown. Based on: K. Morishima et. al.: NATURE , 552 (21/28), 386 (2017).
Some companies are currently proposing the use of muography to verify the cargo transported in closed trucks.
57
READING SUGGESTIONS
The concepts of Nuclear Physics and its applications, discussed in this book, can be found in basic reference books, such as:
BRIMICOMBE, Michael W. Physics in Focus. Melbourne: Nelson Thornes Ltd., 1990. HALLIDAY, David; RESNICK, Robert; WALKER, Jearl. Fundamentals of Physics. 10th ed. New York: John Wiley & Sons, Inc., 2014. v.2. HEWITT, Paul. Conceptual Physics. 12th ed. Boston: Pearson Education, Ltd., 2015. JONES, Edwin R.: CHILDERS, Richard L. Contemporary College Physics. 3d ed. New York: McGraw-Hill, Inc., 2000. SERWAY, Raymond A.; JEWETT, John W. Physics for Scientists and Engineers with Modern Physics. 8th ed. Belmont: Brookscole, 2009.
Some websites offer information on nuclear power and its applications:
The Periodic Table. Available at:
59 Regina Pinto de Carvalho is a retired professor and researcher of the department of Physics at the Universidade Federal de Minas Gerais [UFMG], Brazil, where she has always sought to promote the teaching of Physics at all levels, through advising students or training future teachers and professors. She remains dedicated to this goal, both inside and outside the University, and continues training teachers while also producing texts and books to make the study of Physics more accessible and captivating. Regina was born in Belo Horizonte, in 1950, where she currently lives, after having worked and studied in other cities in Brazil and abroad. She has two children and three grandchildren.
60
"Thebookisactuallyverywellwritten,conciseandeasytoread!... Ithinkit'sgreatthat[theauthor]isspreadingawarenessforeveryone, especiallywhenpeopleisscaredabout[nuclearenergy]nowadays. Ithinkit'sagoodbooktohaveintheclassroom." (Gauri,engineeringstudent)
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