Radiation Response Course

Defence Research and Recherche et de´veloppement Development Canada pour la de´fense Canada

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Pre-Instructional Package

T. J. S. Munsie DRDC – Suffield Research Centre

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Defence Research and Development Canada Reference Document DRDC-RDDC-2020-D130 December 2020

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IMPORTANT INFORMATIVE STATEMENTS

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CAN UNCLASSIFIED Abstract

DRDC-RDDC-2020-D130 i Résumé

La présente trousse de préinstruction devrait fournir la matière de base nécessaire pour maîtriser le langage utilisé durant le cours sur les effets du rayonnement. Une part importante du cours devrait être une revue de la matière et on en confirmera le contenu au début du cours. Les annexes constituent la documentation de référence. On s’attend à ce que les candidats se familiarisent avec la terminologie à le glossaire, la conversion des unités à l’annexe A et la liste de radioisotopes médicaux d’usage courant à l’annexe B. La terminologie à le glossaire est déjà utilisée en partie dans la trousse de prélecture, mais elle servira également durant le cours. Cette terminologie représente l’essentiel du « jargon technique » utilisé en radiologie et constitue le technolecte des sciences radiologiques.

ii DRDC-RDDC-2020-D130 Table of Contents

Abstract...... i

Résumé...... ii

Table of Contents...... iii

List of Tables...... iv

Acknowledgements...... v

1 Introduction...... 1

2 Understanding Radiation and its Health Effects...... 1

2.1 Types of Radiation...... 1

2.1.1 Alpha Radiation...... 1

2.1.2 Beta Radiation...... 2

2.1.3 Gamma Radiation and X-rays...... 4

2.1.4 Neutron Radiation...... 6

2.1.4.1 Water as a Neutron Shield...... 8

2.1.4.2 Concrete as a Neutron Shield...... 8

2.2 How Radiation is Measured...... 9

2.3 Biological Effects of Radiation Exposure...... 11

2.4 Interaction of Radioactive Particles with Shielding Materials...... 13

3 General Radiation Protection Principles...... 14

4 Sources of Radiation...... 15

4.1 Natural Background Radiation...... 15

4.1.1 Cosmic Radiation...... 16

4.1.2 Terrestrial Radiation...... 16

4.1.3 Inhalation...... 16

DRDC-RDDC-2020-D130 iii 4.1.4 Ingestion...... 17

4.2 Making an Effective Background Measurement...... 17

4.3 Commercial Radiological Sources and Shipments...... 18

4.3.1 Radiography Cameras and Projectors...... 18

4.3.2 Well-logging Devices...... 18

4.3.3 Medical Applications...... 21

4.3.3.1 Teletherapy...... 21

4.3.3.2 Blood Irradiation...... 21

4.3.3.3 Brachytherapy...... 22

4.3.4 Research Applications...... 23

4.3.5 Energy Applications...... 23

4.3.6 Transportation and Packaging...... 23

References...... 24

Annex A: SI Units and Conversions...... 25

Annex B: Radioisotopes used in Medical Applications...... 27

List of Symbols/Abbreviations/Acronyms/Initialisms...... 31

Glossary...... 32

iv DRDC-RDDC-2020-D130 List of Tables

Table 1: Weighting factors for dose based on particle type...... 10

Table 2: Weighting factors for dose based on effected tissue...... 11

Table 3: Biological effects of radiation based on dose...... 13

Table 4: A comparison of the density and gamma radiation half-value layer (HVL) of various typical shielding materials for 1 MeV gamma photons...... 14

Table 5: A partial list of commercial uses of radioisotopes...... 19

Table 6: A partial list of the appearance and radiation type of commercially used radioisotopes...... 20

Table A.1: Table of SI prefixes...... 25

Table A.2: Conversion between becquerel and curie units...... 25

Table A.3: Conversion between gray and rad units...... 26

Table A.4: Conversion between sievert and rem units...... 26

Table B.1: Medical uses of reactor-generated radioisotopes...... 27

Table B.2: Medical uses of cyclotron-generated radioisotopes...... 29

DRDC-RDDC-2020-D130 v Acknowledgements

The author would like to thank Dan White and the members of the Radiation and Nu- clear Technologies Group (RN Tech Gp), Counterterrorism and Training Centre (CTTC), Defence Research and Development Canada (DRDC) – Suffield Research Centre for their feedback. Additionally the author would like to thank Canadian Special Operational Forces Command (CANSOFCOM) for their feedback and input in the development of this pre- program instruction package (PIP).

vi DRDC-RDDC-2020-D130 1 Introduction

This pre-instructional package (PIP) is designed to cover the basic material required to be fluent in the language that will be used on the Radiation Response Course. It isexpected that a significant amount of this material is review, and the contents will be confirmed atthe beginning of the course. Part of this material (the appendices) is meant as a during-course and future reference document. A significant portion of Section 4.3 is likely new material, will be spoken about during the course and can be considered as reference for the level of understanding needed prior to the course. Information from Section 4.3 will make only a cursory appearance in the PIP reading evaluation.

2 Understanding Radiation and its Health Effects

Ionizing radiation is a type of radiation travelling either as a particle or electromagnetic wave, that carries sufficient energy to detach electrons from atoms or molecules, thereby ionizing them. Ionizing radiation is made up of energetic subatomic particles, ions or atoms moving at high speeds (usually greater than 1% of the speed of light) or electromagnetic waves on the high-energy end of the electromagnetic spectrum—typically x-rays and gamma rays. Ionizing radiation delivers sufficient energy to break the binding force between the electrons and the nucleus of the atom. For this reason, ionizing radiation is able to make changes to cells in our bodies. These same particles at low energy, or electromagnetic waves at lower energy such as radio or FM waves, are non-ionizing and essentially harmless in most circumstances.

2.1 Types of Radiation

There are four primary forms that ionizing radiation takes; three are particles and one is an electromagnetic wave. The particles are known as alpha particles, beta particles and neutrons. Of those, alpha and beta particles are directly ionizing, or cause ionization of an atom through their own interactions, while neutrons are considered indirectly ionizing, as they don’t create the ionization effect themselves, but generate a spray of daughter products in their interactions that do. The electromagnetic waves are known as gamma rays ionize atoms, and some high energy x-rays can ionize atoms as well.

2.1.1 Alpha Radiation

The production of alpha particles is termed alpha decay. Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. Alpha particles are relatively large and carry a double positive charge. Alpha particles cannot penetrate human skin and can be shielded by as little as a piece of paper. For example, the ranges of a 5 MeV alpha particle (most have such initial energy) are approximately only 0.002 cm in aluminium alloy or approximately 3.5 cm in air. The reason that they are so

DRDC-RDDC-2020-D130 1 easily stopped is that, on an atomic scale, they are massive in size and they are highly charged. However, if radioactive materials that emit alpha particles enter the body through ingestion, inhalation, or open wounds, they can cause severe damage to surrounding tissues. When an alpha particle interacts it can deposit an, atomically speaking, massive amount of energy per particle. When this energy is deposited into a piece of paper or a dead cell, the damage is unimportant. When it does so to a living cell, such as inside the human body where there is no dead layer of skin cell to be protective, they will easily disrupt or destroy the cell and can cause extreme internal damage even in small quantities. Moreover pure alpha radiation is very rare. Alpha decay is frequently accompanied by gamma radiation which is significantly more difficult to shield and discussed further in this section. Asimple summary of the properties is below.

• Alpha particles are energetic nuclei of helium and they are relatively heavy and carry a double positive charge.

• Alpha particles interact with matter primarily through coulomb forces (ionization and excitation of matter) between their positive charge and the negative charge of the electrons from atomic orbitals.

• Alpha particles heavily ionize matter and they quickly lose their kinetic energy. On the other hand they deposit all their energies along their short paths.

• Alpha particles can be stopped, or shielded, by a sheet of paper or the outer layer of skin.

In nuclear reactors they are produced for example in the fuel (alpha decay of heavy nuclei). Alpha particles are commonly emitted by all of the heavy radioactive nuclei occurring in nature (uranium, thorium or radium), as well as the transuranic elements (neptunium, plutonium or americium). Especially energetic alpha particles are produced in a nuclear process, which is known as a ternary fission. In this process, the nucleus of uranium is split into three charged particles (fission fragments) instead of the normal two with the smallest of the fission fragments most probably (90% probability) being an extra energetic alpha particle.

2.1.2 Beta Radiation

Beta particles are high-energy, high-speed electrons or positrons emitted by certain fission fragments or by certain primordial radioactive nuclei such as potassium-40. The beta particles are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay. There are two forms of beta decay: the electron decay (β− decay) and the positron decay (β+ decay). In a nuclear reactor this is especially likely to occur because a common result of fission products is an excess of neutrons. An unstable fission fragment with the excess of neutrons undergoes β decay, where the neutron is converted into a proton, an electron, and an electron antineutrino.

2 DRDC-RDDC-2020-D130 Beta particles are smaller and faster-moving than alpha particles, can travel through air several yards from the nuclei that emit them. Beta particles are slightly penetrating and can damage or penetrate the outer layers of skin (about 1 millimetre of tissue). They can be shielded by most clothing or materials such as plastic or aluminum foil. At high energies, beta particles have the ability to pass through approximately 2 cm of water or flesh, but can easily be stopped by 0.1 mm of aluminium. Like alpha particles, if they enter the body, beta particles can damage internal tissues and organs. When beta radiation interacts with a high Z material, it produces electromagnetic emissions known as Bremßtrahlung, German for “braking radiation.” Bremßtrahlung radiation is produced when charged particles are slowed down in matter, causing some of their kinetic energy to be converted into electromagnetic energy in the form of x-rays. The amount of Bremßtrahlung produced increases with increasing Z and density, which is why low-Z materials such as plastic or aluminium, rather than lead, are used to shield beta radiation. Lead and plastic are commonly used to shield mixed or pure beta radiation. Radiation protection literature is ubiquitous in advis- ing the placement of plastic first to absorb all the beta particles before any lead shielding is used.

Because of their mass, charge and coulomb interactions, the path of a beta particle through a material is not straightforward. Typically the path of the particle is best described as zig-zag, so their total distance traveled is significantly longer than the linear penetration depth of the particle, which is a useful feature for shielding. It is possible, especially when the particle is moving from one material to another, for its phase velocity to be high enough that at the interface it would be moving faster than the speed of light. This isn’t allowable by the laws of physics, so the material generates a shockwave of electromagnetic radiation at the interface known as Cherenkov radiation. This is what is responsible for the blue glow of uranium in water. This can be thought of as an equivalent to a sonic boom, but for light.

• Beta particles are highly energetic electrons or positrons and carry a single negative or positive charge, respectively.

• Beta particles typically interact with atomic outer-shell electrons through coulomb forces (ionization and excitation of matter) between their charge and the charge of the electrons from atomic orbitals.

• By virtue of their small mass, betas have much higher speeds and smaller impulses are involved in the collisions. This means that the stopping distance is an order of magnitude larger than for alpha particles.

• Lower density (low-Z) materials should be used to shield beta particles to avoid the production of x-rays (Bremßtrahlung) from atomic outer shell interactions in high-Z material.

DRDC-RDDC-2020-D130 3 2.1.3 Gamma Radiation and X-rays

Gamma and x-rays are electromagnetic waves (photons) that can travel hundreds of metres through air from the nuclei that emit them. Gamma radiation is the term given for electromagnetic waves that occur from interactions of particles within the nucleus. The emission of this electromagnetic radiation is the result of energy conservation in nuclear processes—when one particle or energetic wave interacts with another particle in an excited nucleus and causes a reaction this is the left-over or liberated energy resultant from brining the nucleus, nominally back to its energetic ground state. X-radiation is caused by interactions outside of the nucleus, primarily particles interacting with outer (or for higher energy x-rays, inner) electrons in the electron orbital cloud surrounding the nucleus. Although reactions within the nucleus typically require and liberate significantly higher quantities of energy, it is possible for high energy x-rays to be more energetic than low- energy gamma rays. Every process involving the electrons in their orbitals and every nuclear reaction obeys quantum mechanics, and the energy of each reaction is quantized. This mean that emission of a particular wavelength of gamma ray, and commonly for x-rays as well, is unique to a particular process for a particular atom. The pattern of x-ray and gamma ray emission can therefore be used as a fingerprint for a particular nuclear reaction and with an appropriate detector you can determine what is happening and to which atom or atoms. Gamma and x-rays can be generated both through natural processes or artificial means. The energy of a gamma or x-ray can be equivalently expressed as a frequency or wavelength, as all three of these terms are related by physical constants.

Without proper shielding, gamma and x-rays can pose significant health hazards even outside the body and must be heavily shielded to be safe. Very dense objects such as concrete or brick buildings or heavy vehicles can shield gamma or x-radiation. Key features of gamma rays are as follows:

• Gamma rays are high-energy photons. Photons form every part of the electromagnetic spectrum, so structurally they are the same as light. Just with a lot more energy and therefore a shorter wavelength.

• Photons (gamma rays and x-rays) can ionize atoms directly, despite the fact that they are electrically neutral, through the Photoelectric effect and the Compton Effect, but secondary (indirect) ionization is much more significant.

• Gamma rays travel at the speed of light and they can travel thousands of metres in air before spending their energy.

• Since the gamma radiation is very penetrating in matter, it must be shielded by very dense materials, such as lead or uranium.

• Gamma rays frequently accompany the emission of alpha and beta radiation.

4 DRDC-RDDC-2020-D130 Since gamma rays and x-rays exhibit a logarithmic relation between shielding thickness and intensity, only partial reduction of the radiation can be obtained. Stated differently, shielding reduces, but never eliminates, the probability that a wave can pass through shielding material. A shield can effectively reduce exposure to zero, but it can never absolutely do so. This is in contrast to a sheet of paper which can be considered to absolutely stop alpha particles. Lead is widely used as a gamma shield. A major advantage of lead shield is in its compactness due to its higher density. Similarly, depleted uranium is more effective due to its higher Z. Depleted uranium is used for shielding in portable gamma ray sources. It isn’t otherwise generally used owing to the lack of supply, higher cost and requirement to report and log all use of it as depleted uranium is a signal of enrichment activity (i.e., if you have depleted uranium, where did the radioactive part of natural uranium go?).

In nuclear power plants, shielding of a reactor core can be provided by the materials of the reactor pressure vessel and a heavy, typically hydrogen-dense concrete that is used to shield both neutrons and gamma radiation. Although water is neither a high density nor high Z material, it is commonly used as a gamma shields. Water provides a radiation shielding of fuel assemblies in a spent fuel pool during storage or during transports from and into the reactor core. In this case a significant amount of water is required, but it is something that is readily available.

In general, gamma radiation shielding is much more complex and difficult than the alpha or beta radiation shielding. In order to understand comprehensively the way how a gamma ray loses its initial energy, how it can be attenuated and how it can be shielded we must have detailed knowledge of the its interaction mechanisms.

Although gamma rays can directly ionize radiation, it is more likely that they will deposit their energy in an atomic particle and the subsequent interaction of that particle will cause the ionization itself. Based on the energy involved, there are three processes by which gamma radiation interacts with matter: the photoelectric effect, Compton scattering and pair production.

The photoelectric effect is the phenomenon that transforms visible light, infrared andul- traviolet rays into electricity in solar panels and cells of our cameras. It is also involved in the completely different field of radioprotection: by transforming penetrating X andgamma rays into electrons easy to stop, it protects us from the effects of these radiations. The photoelectric effect occurs in two stages. First, the photon takes out a bound electron inone atom. In the case of an incoming gamma photon, it is usually an electron belonging to the innermost layers, spectroscopically referred to as from then K (n = 1) or L (n = 2) shells. The atom that has lost one of its inner electrons is then left in an excited state. An electron from an outer shell (typically n > 3) moves to occupy the vacancy left by the ejected electron. An X-ray is emitted during this transition. Heavy atoms, such as lead, are much more favorable for the photoelectric effect and for radioprotection because the material is very dense. The binding energies of the K and L inner shell electrons, respectively, are much larger as the Z value increases.

DRDC-RDDC-2020-D130 5 The Compton effect is the name given by physicists to the collision between aphotonand an electron. The photon bounces off a target electron and loses energy. These collisions, referred to as elastic collisions, compete with the photoelectric effect when gamma rays pass through matter, further contributing to their attenuation. These elastic collisions become predominant when the photon energy becomes large compared to the energy that holds the electron in an atom, known as its binding energy. For a light atom such as carbon, the Compton effect prevails on the photoelectric effect above 20 keV. For copper it isabove 130 keV, and for lead, 600 keV. In this gamma energy range, which is rather extended, the phenomenon concerns all the electrons of the atom, whereas in the photoelectric effect these are the ten electrons from the innermost K and L shells, which play a role. For an absorber, it is the density of electrons that is crucial in the range where Compton effect dominates. Lead has thus also an advantage over lighter materials, in contrast to the photoelectric effect. The gamma photon is not destroyed in Compton collisions. The photon that emerges with the electron, called the “scattered” photon shares the initial energy with the electron set in motion. The electron then loses its energy by ionization as a beta electron. The scattered gamma propagates through the material without depositing energy until it interacts again. The energy sharing is unequal. It depends on the angle between the scattered photon and the initial gamma ray. Despite its extremely light mass, the electron is indeed a heavy target for a photon that is massless. The laws of physics governing the Compton effect are such that the scattered photon carries most of the initial energy: 96% on average at 50 keV, 83% at 500 keV. The scattered photon emerges usually in a different direction than the incident photon one. It can even go backward (backscattering). On average it scatters with an angle of 30 to 45 degrees. Gamma of hundreds of keV can undergo multiple Compton scattering before being absorbed by the photoelectric effect process.

When the gamma energy exceeds 1 MeV Compton scattering begins to be challenged by a new phenomenon: the transformation of a gamma into an electron and its antiparticle, a positron. This phenomenon is called pair production and becomes prominent with the high-energy gamma produced, for example, by a particle accelerator.

2.1.4 Neutron Radiation

Neutrons are uncharged particles found in the nucleus of any atom heavier than hydrogen. They can travel tens of yards through air from the nuclei that emit them and can be extremely damaging to tissue if present in large amounts. Neutrons can cause both internal and external damage and are more difficult to shield than gamma or x-rays. In sufficient quantities, materials high in hydrogen content (e.g., water, damp earth, concrete, and plastic) can effectively shield neutrons.

Outside the nucleus, free neutrons are unstable and have a half-life of 610 s (about 10 minutes, 10 seconds). The neutron will go through beta decay, described above, into a proton, electron and electron antineutrino. The opposite process for a proton and electron to turn into a neutron is energetically impossible, since a free neutron has a greater mass than a free proton. A high-energy collision of a proton and an electron or neutrino can, however, result in a neutron.

6 DRDC-RDDC-2020-D130 There are three main features of neutrons, which are crucial in the shielding of neutrons:

• Neutrons have no net electric charge, therefore they cannot be affected or stopped by electric forces. Neutrons ionize matter only indirectly, which makes neutrons a highly penetrating type of radiation.

• Neutrons scatter with heavy nuclei very elastically. It is difficult for heavy nuclei to slow down, let alone capture a fast neutron.

• The absorption of a neutron (one could equally say shielding of a neutron) causes initiation of certain nuclear reactions (e.g., radiative capture or even fission), which is accompanied by a number of other types of radiation. In short, neutrons make matter radioactive, therefore with neutrons we also have to shield the other types of radiation.

The best materials for shielding neutrons must be able to:

• Slow down (moderate) neutrons. This can be fulfilled only by material containing light atoms (e.g., hydrogen atoms), such as water, polyethylene, and hydrogen-rich concrete. The nucleus of a hydrogen atom contains only a proton. Since a proton and a neutron have almost identical masses, a neutron scattering on a hydrogen nucleus can give up a great amount of its energy. Up to the entire amount of energy from the neutron can theoretically be transferred to the proton, which due to its charge is much easier to slow and stop, in a single collision. This is similar to a billiard ball. Since a cue ball and another billiard ball have identical masses, the cue ball hitting another ball can be made to stop and the other ball will start moving with the same velocity. On the other hand, if a ping pong ball is thrown against a bowling ball (neutron vs. heavy nucleus), the ping pong ball will bounce off with very little change in velocity, only a change in direction. Therefore, lead is quite ineffective for blocking neutron radiation, as neutrons are uncharged and can simply pass through dense materials, ping-ponging their way through.

• Absorb a slow neutron. Thermal neutrons, which are those that have been slowed to approximately 0.025 MeV, can be easily absorbed by nuclear capture in materials with high neutron capture cross sections like boron, lithium or cadmium. Generally, only a thin layer of such an absorber is sufficient to shield thermal neutrons. Hydrogen (in the form of water), which can be used to slow down neutrons, does have a usable cross-section, effectively about 1% of the previously listed atoms. Although small, this insufficiency can be offset by using a sufficient thickness of water as ashield.With respect to nuclear cross-section, it should be noted that not just the element, but the specific isotope matters significantly. Hydrogen (a single proton) is over 6,000times more likely to absorb a neutron than deuterium (a proton and a neutron). Boron-10 is 100 times better than hydrogen, cadmium-113 is 150 times better than boron-10 and xenon-135 is over 60 times better than cadmium-113 [1]. The abundance, ease of

DRDC-RDDC-2020-D130 7 isotopic separation and toxicity play a significant role on what we use for shielding materials, as opposed to simply the physical processes involved.

• Shield the accompanying radiation. In the case of a cadmium shield, the absorption of neutrons is accompanied by strong emission of gamma rays. Therefore additional shielding is necessary to attenuate the gamma rays. This phenomenon practically does not exist for lithium and is much less important for boron as a neutron absorption material. For this reason, materials containing boron are used often as neutron shields. In addition, boron (in the form of boric acid) is soluble in water making this combination a very effective neutron shield.

2.1.4.1 Water as a Neutron Shield

Water, due to its high hydrogen content and its availability, is both an effective and common neutron shielding material when used correctly. In the specific case of neutrons, water perfectly moderates neutrons, but the absorption of neutrons by hydrogen nuclei produces secondary gamma rays with high energy. Due to the low atomic number of hydrogen and oxygen, water is not generally an effective shield against these gamma rays. In some cases, this disadvantage of water (low density) can be compensated by the high thickness of the water shield. Adding boric acid to the water can substantially help with this problem as boron is a much stronger neutron absorber, compared to water, and the reaction of a neutron with boron-10 produces almost no significant gamma emission. The difficulty of using boric acid and water then becomes the issue of construction materials, as boric acid will also react to degrade structural materials significantly more than water alone would.

2.1.4.2 Concrete as a Neutron Shield

The most commonly used neutron shielding in many sectors of nuclear science and engineer- ing is concrete. Concrete is also a hydrogen-containing material, but unlike water concrete has a higher density (suitable for secondary gamma shielding) and does not need any main- tenance. Because concrete is a mixture of several different materials its composition is not constant. When referring to concrete as a neutron shielding material, the material used in its composition should be understood as concrete is more a class of materials than a mixture. Several specific formulations have been engineered for nuclear shielding purposes. Generally, concretes are divided into “ordinary” concrete and “heavy” concrete. Heavy concrete contains heavy natural aggregates such as barites (barium sulfate) or magnetite or manufactured aggregates such as iron, steel balls, steel punch or other additives. As a result kg of these additives, heavy concrete has a higher density than ordinary concrete (~2300 m3 ). kg kg Very heavy concrete can achieve density up to 5,900 m3 with iron additives or up to 8900 m3 with lead additives. Heavy concrete provides very effective protection against neutrons.

8 DRDC-RDDC-2020-D130 2.2 How Radiation is Measured

There are four different but interrelated measurements for radiation and radiation exposure: radioactivity, exposure, absorbed dose, and dose equivalent (remembered by the mnemonic R-E-A-D). Both metric (becquerel) and imperial (curie) units are in use.

Radioactivity (or simply activity) refers to the amount of ionizing radiation released by a material. In other words, it is a measure of the number of disintegrations or radioactive decays it undergoes per unit time. The units for radioactivity are the curie (Ci) and becquerel (Bq), where 1 Ci = 3.7 x 1010 Bq or 37 GBq. 1 Bq is equal to one disintegration per second. 1 Curie was originally defined as the rate of radiation emanating from one gramof radium, but is now standardized as above.

The half-life is the time required for one half of the initial amount of the parent radioisotope to decay to the daughter isotope. The activity is proportional to the amount of material, so it decreases at the same rate, and the fraction of the initial parent activity (A0) remaining after time t can easily be calculated using Equation1, where A0 is the initial activity, t is the time since initial activity was measured and t1/2 is the halflife of the radioisotope.

t   t A 1 2 A(t) = 0 / (1) 2

This equation, simply, tells us that after one half-life, half of the parent radioisotope remains; after two half-lives, one quarter remains; after three, one eighth, etc. The situation is more complicated when the daughter isotope is, in turn, radioactive. Equilibrium occurs in a decay chain when a radionuclide decays at the same rate it is produced. If the parent and the daughter have similar half-lives, after a period of in-growth, the total activity will decay at roughly the same rate as the original radionuclide (transient equilibrium); if the parent half-life is much longer than the daughter, within about 7 half-lives, the daughter will decay at the same rate as the parent (secular equilibrium); and finally, if the daughter is much longer-lived than the parent, there will be no equilibrium.

Exposure describes the amount of radiation travelling through the air. Many radiation mon- itors measure exposure. The units for exposure are the roentgen (R) and coulomb/kilogram C ( kg ). Gamma radiation is measured in roentgens, which measure the amount of ionization caused in air. Since gamma rays have no mass, R is purely a measure of energy.

Absorbed dose, represented by D, is a measure of the energy imparted per unit mass. The SI unit of absorbed dose is the Gray (Gy), where 1 Gy = 1 J/kg. The traditional unit of absorbed dose is the rad (1 Gy = 100 rads). Conversion of roentgens to rads depends on the material absorbing the radiation. In tissue near the surface of the body, 1 R equals 1 rad. One roentgen of exposure will deposit 0.00877 Gy (0.877 rad) of absorbed dose in dry air and 0.0096 Gy (0.96 rad) in soft tissue. The rate at which the energy is imparted is the absorbed dose rate (Gy/h or rad/h).

DRDC-RDDC-2020-D130 9 Table 1: Weighting factors for dose based on particle type [2].

Radiation type Radiation weighting factor wR Photons 1 Electrons 1 Alpha Particles 20 Fission Fragments 20 Heavy Ions 20 Neutrons < 10 keV 5 Neutrons 10 keV to 100 keV 10 Neutrons > 100 keV to 2 MeV 20 Neutrons > 2 MeV to 20 MeV 10 Neutrons > 20 MeV 5 Protons (other than recoil), >2 MeV 2 to 5

Equivalent dose, represented by H, takes into account the fact that the biological harm to an organ depends not only on the physical average dose received by that organ, but also on the way in which the energy is deposited in the tissue. For example, alpha or neutron radiation will cause much greater damage than gamma or x-ray because they will deposit their energy much more densely, resulting in a higher probability of irreversible damage to chromosomes and less chance of tissue repair. This means that the absorbed dose to a particular organ or tissue is multiplied by a radiation weighting factor, wR, resulting in a quantity called the equivalent dose, HT :

HT = wRDT,R (2)

Where DT,R is the absorbed dose from radiation type R averaged over an organ or tissue T . The weighting factor(w) is 1 for gammas, x-rays, and betas; values for other types of radiation are given in Table1. It should be noted that especially for neutrons and protons the actual weighting factor is a function of energy, and the values reported in Table1 are a step-wise linear approximation, and other than around 700–900 keV energies generally overestimate the actual damage by approximately 0–10%. These are changing as we better measure the effects on tissue, as it isn’t possible to determine the actual effects through scientific laws—only through measurements and experimentation as they will be averages based on the individual.

The Si unit of equivalent dose is the sievert (Sv), while the traditional unit is the rem (1 Sv = 100 rem). Example: For photon radiation (i.e., gammas or x-rays), an absorbed dose of 1 Gy = 1 Sv, but for the same absorbed dose of alpha particles, the equivalent dose is 20 Sv as there is twenty times as much damage to tissue (wR = 20). Units for dose equivalent are roentgen equivalent man (rem) and sievert (Sv). Equivalent dose rates are usually expressed in Sv/hr or mSv/hr.

10 DRDC-RDDC-2020-D130 Table 2: Weighting factors for dose based on effected tissue [3].

Radiation type Radiation weighting factor wR Gonads 0.08 Bone Marrow 0.12 Lungs 0.12 Breast 0.12 Thyroid 0.04 Bone Surface 0.01 Colon 0.12 Stomach 0.12 Bladder 0.04 Liver 0.04 Esophagus 0.04 Skin 0.01 Salivary Glands 0.01 Brain 0.01 Remainder 0.12

Effective dose takes into account the fact that, for the same equivalent dose, different organs or tissues will suffer different degrees of damage. The tissue weighting factor, wT , represents the relative contribution of an organ or tissue to the whole-body damage, with the sum of all tissue weighting factors being 1 (i.e., the sum of all the body’s tissues). The effective dose due to only one type of radiation R is given by summing the equivalent dose to each organ or tissue, weighted according to the tissue weighting factor, over the whole body per Equation3.

E = ΣwT HT (3)

The tissue factors are given in Table2. The sievert (Sv) used as both the unit of equivalent dose and of effective dose.

2.3 Biological Effects of Radiation Exposure

When ionizing radiation interacts with atoms of living cells, it breaks chemical bonds, ulti- mately damaging the cellular material. DNA is the primary component of cellular damage from ionizing radiation. In addition, radiation also ionizes other molecules (such as water), producing negatively and positively charged ions (which are also referred to as radicals). These ions are highly reactive and chemically toxic, and can damage surrounding cells or molecules. This mechanism is referred to as indirect action. Alpha particles, for example, can damage DNA through direct action, where rather than causing a chemical reaction that

DRDC-RDDC-2020-D130 11 destroys the DNA chain it simply impacts and destroys the chemical bonds like a bowling ball going through bowling pins.

When DNA in a cell is damaged, there are three possible outcomes:

• The damaged cell repairs itself and there are no further effects or risks.

• The damaged cell cannot repair itself and dies.

• The damaged cell incorrectly repairs itself and mutations occur. The cell will then go on to produce abnormal cells which over time may become cancerous. This is how exposure to ionizing radiation increases the risk of developing cancer.

Because ionizing radiation damages the DNA of a cell, which is critical to cell division, cells that are actively proliferating/dividing at the time of exposure are the most radiosensitive. These include white blood cells and the cells lining the GI tract. The effects of radiation manifest themselves following cell division (cell death or mutation); therefore, cells that have very slow cell turnover/division tend to be less affected by radiation (e.g., bone cells). This is why different organs and parts of the human body have been assigned different weights in computing a whole-body dose in Table2. The biological effects of radiation can be divided into two categories: deterministic, or those that occur as a direct result of the exposure, and stochastic, or those that have a certain probability of occurring following exposure, and may occur much later on.

Deterministic adverse health effects have three key characteristics:

1. A minimum dose must be exceeded before the effect is observed (threshold);

2. The severity of the effect depends on the absorbed dose; and

3. There is a clear causal relationship between the exposure and the effect.

For these reasons, deterministic effects are typically observed in shorter time frames following exposures to significant doses of ionizing radiation (i.e., they are acute). Examples of deterministic effects include radiation-induced cataract formation and nausea and/or vomiting hours after exposure. Table3 lists some of the deterministic effects of acute exposure to radiation. The dose threshold for onset of various deterministic effects differs from person to person, depending on the variation of radio-sensitivity within the general population.

Stochastic effects occur by chance; they occur among unexposed as well as exposed individuals, but their probability may be increased by exposure to radiation. Unlike deterministic effects, they may occur without reaching a threshold level of radiation dose. While theprob- ability of occurrence of a stochastic effect increases with dose, its severity is independent of the dose. Cancer is the most common stochastic effect associated with radiation exposure.

12 DRDC-RDDC-2020-D130 Table 3: Biological effects of radiation based on dose[4].

Radiation (mSv) Deterministic Effects Chromosome aberrations can be detected (that may later cause stochastic effects) and temporary depression of white blood cell lev- Up to 750 els in some individuals at the high end of the dose range. No other observable effects. Nausea, vomiting, fever in 5 to 50 percent of exposed individuals within 24 hours of exposure with fatigue and loss of appetite over 750–3,000 several weeks. Slight to moderate reduction in white blood cells. Re- covery within a few weeks for most symptoms. Most individuals will suffer nausea, vomiting, anorexia, extreme fatigue and weakness within hours of exposure. Severe blood changes, with internal bleeding and increased susceptibility to infection, par- 3,000–6,000 ticularly at the higher doses. Recovery from 1 month to a year for most individuals at the lower end of the dose range; at the upper end of the dose range, death may occur for more than 50%. Vomiting will occur within hours of exposure. Severe blood changes, internal bleeding, infection, bone marrow destruction, and skin burns. 6,000–10,000 Between 80 and 100 percent of exposed individuals will succumb within 2-4 weeks; survival is unlikely.

2.4 Interaction of Radioactive Particles with Shielding Materials

Although each subsection on the different particles spoke about the specifics for shielding of radioactive materials, it should be noted that any material will provide some degree of shielding of particles. Typically what will always be relatively available and generally useful are things like iron, concrete, lead, and soil. The shielding ability of a material is determined by its density and the thickness of the material required to absorb radiation. This does vary slightly based on material and particle type, as was described in the subsections above. For gamma radiation, a useful measure is radioactive penetration based on material used known as the half-value layer (HVL) and tenth-value layer (TVL) numbers. This defines the thickness of a material to stop 50% or 90% of the radioactivity from penetrating, respectively. If you double the HVL and TVL thicknesses, that would shield 75% (the original 50% and 50% of the remainder, so 25%) or 99% (90% plus 90% of the remainder, so 9%) respectively. Sample HVL values for several materials and their respective density against 1 MeV gamma photons is given in Table4.

DRDC-RDDC-2020-D130 13 Table 4: A comparison of the density and gamma radiation half-value layer (HVL) of various typical shielding materials for 1 MeV gamma photons [5].

Element Density HVL thickness (cm) g air 0.0013 8.451 cm3 g water 1.00 9.76 cm3 g concrete 2.35 4.65 cm3 g aluminium 2.82 4.225 cm3 g iron 7.86 1.471 cm3 g lead 11.35 0.816 cm3

3 General Radiation Protection Principles

Protection from external exposure to all types of ionizing radiation is based on three important considerations:

• Time

• Distance

• Shielding

Time: Minimize the amount of time spent near a radiation source to reduce external (direct) exposure (total dose = dose rate x time).

Distance: Radiation exposure decreases rapidly with increasing distance from the radiation source. Distance is of particular concern when dealing with gamma rays and neutrons, because, unlike alphas and lower-energy betas, they can travel long distances. The intensity of a radiation source is inversely proportional to the square of the distance (it drops off with 1 r2 , where r is the distance from the source). This is known as the Inverse Square Law. The relative intensity at two different distances from the source is expressed by Equation4.

2 I1 (D2) = 2 (4) I2 (D1)

Equation4 tells us that if you double the distance (from d to 2d), you reduce the radiation intensity (and therefore the dose rate) by a factor of four (22). Increasing distance can be as simple as handling a source with tongs instead of using your fingers.

14 DRDC-RDDC-2020-D130 Controlling internal exposure is effectively also a matter of controlling distance fromthe source by using appropriate protective equipment to ensure that no radionuclides enter the body via inhalation, ingestion, or absorption. When relating inhalation, ingestion or absorption to the inverse quare law (Equation4) this can be thought of in terms of reducing your distance to the source effectively to zero, meaning an effective dose intensity of100%.

Shielding: For radiation protection purposes, shielding refers to the placement of a material around a radiation source in order to reduce the radiation intensity to a safe level. The thicker the layer of shielding around a radiation source, the smaller the exposure, assuming appropriate shielding materials are used. The type and amount of shielding required depends on the type of radiation and the energy of the radiation, as was covered above. As a simple example, using Table4 we can see that if we had 100 mSv of 1 MeV gamma radiation, if there we placed the source in 20 cm of water (2 half value layers, or a 75% reduction) the surface dose rate would be approximately 25 mSv. If the container holding the water and source was made out of 5 cm of concrete (another 2 HVLs, or another 75% reduction) the dose rate at the surface of the concrete would be approximately 6.25 mSv. The same shielding effect as the water and concrete could be accomplished with 3.25 cm ofleador 5.9 cm of iron, equal to 4 HVLs of each material.

In general, the goal of radiation protection is to keep radiation exposures as low as reasonably achievable (ALARA). This can be done by minimizing the exposure time, maximizing the distance from the source, and shielding the radiation source.

4 Sources of Radiation 4.1 Natural Background Radiation

This subsection is adapted from the Nuclear Safety Fact Sheet on background radiation issued by the Canadian Nuclear Safety Commission [6].

Radioactive materials and ionizing radiation are a part of the natural environment, and both generate “background” levels for radiation detection instruments. This background can be considered a constant source of ionizing radiation present in the environment and emitted from a variety of sources. According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), there are four major sources of natural radiation: cosmic radiation, terrestrial radiation and intakes of naturally occurring radionuclides through inhalation and ingestion.The total worldwide average effective dose from natural radiation is approximately 2.4 mSv per year; in Canada, it is 1.8 mSv. In some parts of the world, it is naturally much higher—for instance on the Kerala Coast in India, the annual effective dose is 12.5 mSv. The dose varies with the source of the radiation. For example, in northern Iran, geological characteristics result in a dose that can reach 260 mSv a year.

DRDC-RDDC-2020-D130 15 4.1.1 Cosmic Radiation

The Earth’s outer atmosphere is continually bombarded by cosmic radiation. Usually it originates from a variety of sources, including the sun and other celestial events in the uni- verse. Some ionizing radiation will penetrate the Earth’s atmosphere and become absorbed by humans which results in natural radiation exposure. Regions at higher altitudes receive more cosmic radiation. According to a recent study by Health Canada, the effective dose of radiation from cosmic rays in Vancouver, British Columbia, which is at sea level, is about 0.30 mSv annually. This compares to the top of Mount Lorne, Yukon, where at 2,000 m, a person would receive a dose of about 0.84 mSv annually. Flying in an airplane increases exposure to cosmic radiation, resulting in a further average dose of 0.01 mSv per Canadian per year.

4.1.2 Terrestrial Radiation

The composition of the Earth’s crust is a major source of natural radiation. The main contributors are natural deposits of uranium, potassium and thorium which, in the process of natural decay, will release small amounts of ionizing radiation. Uranium and thorium are found essentially everywhere. Traces of these minerals are also found in building materials so exposure to natural radiation can occur from indoors as well as outdoors. There are also natural sources of radiation in the ground, and some regions receive more terrestrial radiation from soils that contain greater quantities of uranium. The average effective dose from the radiation emitted from the soil (and the construction materials that come from the ground) is approximately 0.5 mSv per year. However, this dose varies depending on location and geology, with annual doses reaching as high as 260 mSv in Northern Iran or 90 mSv in Nigeria. In Canada, the estimated highest annual dose is approximately 2.3 mSv, as measured in the Northwest Territories.

4.1.3 Inhalation

Most of the variation in exposure to natural radiation results from inhalation of radioactive gases that are produced by radioactive minerals found in soil and bedrock. Radon is an odourless and colourless radioactive gas that is produced by the decay of uranium. Thoron, a less common isotope of radon, is a radioactive gas produced by the decay of thorium. Radon and thoron levels vary considerably by location depending on the composition of soil and bedrock.

Once released into the air, these gases will normally dilute to harmless levels in the atmosphere but sometimes they become trapped and accumulate inside buildings and are inhaled by occupants. Radon gas poses a health risk not only to uranium miners, but also to homeowners if it is left to collect in the home. On average, it is the largest source of natural radiation exposure.

The Earth’s crust produces radon gas, which is present in the air we breathe. Radon has four decay products that will irradiate the lungs if inhaled. The worldwide average annual

16 DRDC-RDDC-2020-D130 effective dose of radon radiation is approximately 1.3 mSv. A recent Health Canada survey on radon in homes reported that the radon levels in 93% of Canadian homes are below the Bq current Canadian guideline of 200 m3 .

4.1.4 Ingestion

Trace amounts of radioactive minerals are naturally found in the contents of food and drinking water. For instance, vegetables are typically cultivated in soil and ground water which contains radioactive minerals. Once ingested, these minerals result in internal exposure to natural radiation. Some of the essential elements that make up the human body, mainly potassium and carbon, have radioactive isotopes that add significantly to our background radiation dose.

Natural radiation from many sources penetrates our bodies through the food we eat, the air we breathe and the water we drink. Potassium-40 is the main source of internal irradiation (aside from radon decay). The average effective dose from these sources is approximately 0.3 mSv a year.

4.2 Making an Effective Background Measurement

Place the instrument into service as described in the appropriate user’s manual. If the instrument has an audible indicator of radiation being detected, make sure that it is turned on during background readings so as to become accustomed to the sound signature of background radiation. For a gamma measuring device, set the meter on its lowest scale and hold the meter at 1 metre above the ground (waist high). Allow the meter to stabilize and record the reading. For alpha and beta detectors, use the same procedures as above and take a reading at 1 metre. Note that if the alpha detector responds, the probe is probably defective. Then, place the probe approximately 1 centimetre above the surface and take and record the reading. Repeat each of the readings at least three times. The average of these readings is the background radiation level for the location.You should also repeat the background measurement processes in representative environments—inside buildings and in open outdoor areas. Background readings vary based on location. It is important to remember that facilities that normally house radioactive materials may have background levels that are higher than average and that structures can block some or all of the cosmic background component. Conversely, open air environments typically won’t have radon-related background. Additionally, at a single location background radiation is subject to Poisson statistics, so it cannot be assumed to be perfectly constant.

When responding to an incident, ensure that background readings are taken far enough from the site so they are not affected by the suspected device. The more accurate the background readings, the easier it is to detect an unusual radiation reading. The more sensitive the instrument and the lower the scale used, the more the instrument will respond to background radiation. This fact is important to remember when the device has an audible indicator for radiation detection.

DRDC-RDDC-2020-D130 17 4.3 Commercial Radiological Sources and Shipments

Radioactive materials are found in numerous settings and products—medical diagnostic and treatment facilities, manufacturing and construction industries, research laboratories, power-generating plants, and even some consumer products like certain ceramics, fertilizers, and foods. Some common uses are listed in Table5 and their typical appearances are listed in Table6. There are several sources listed in the tables, such as Ra-226, which are being or have been phased out due to the health hazards and better alternatives, but may still be in use around the world and are left for completenesses sake.

4.3.1 Radiography Cameras and Projectors

Industrial (or gamma) radiography is a type of “non-destructive testing” that uses encap- sulated radiation sources to find flaws in metal industrial objects, such as welds in piping systems. The process assures the safety and structural integrity of welded and joined structures in pipelines, buildings, bridges, and roadbeds; provides control, measurement, and quality assurance in automated industrial processes; and evaluates geological formations in oil, gas, and mineral prospecting. The material to be inspected must be situated between the source of radiation (called the “camera” or “projector”) and film or some other detecting device.

A portable radiography device weighs about 45 pounds and is designed to be hand-carried by one person. In a typical design, the source of a radiography camera is stored in an S-shaped hole through a block of depleted uranium metal, which acts as a heavy shielding. The radiation source in radiography cameras is typically 30–100 curies of iridium-192 or cobalt-60, machined to tiny disks or pellets in a welded stainless steel or titanium capsule about the size of a .22 calibre cartridge. The capsule is affixed to the end of a short flexible cable called a “pigtail.” For deployment; the pigtail is attached to a cable that allows the radiographer, operating at a safe distance, to crank the source out along a guide to the object to be imaged. During use, radiography systems emit high levels of highly penetrating radiation. Operators must be trained and licensed and wear dosimeters and alarms. Transportation and storage are closely regulated, but accidents; losses, and thefts can occur.

4.3.2 Well-logging Devices

Well-logging devices search for underground oil, coal, and natural gas. A mobile well-logging device consists of a gamma and/or neutron source and one or more detectors. When lowered into a drill hole, the device detects reflected radiation and provides insight into the characteristics of the surrounding materials. The device is usually long (4–7 feet) and thin (less than 4 inches in diameter) and weighs several hundred pounds. The radioactive source contained within it is generally small (about 2 inches in diameter). Well-logging sources are typically composed of cesium-137, californium-252, or a mixture of americium-241 and beryllium. The most common source shapes are cylinders and dowels. If an americium-241/beryllium mixture is used, it is usually in a powder (oxide) form and is encased in a ceramic cylinder.

18 DRDC-RDDC-2020-D130 Table 5: A partial list of commercial uses of radioisotopes.

Typical Activity Typical Source Application Typical Isotope (Ci) Shape Medical slug, wafer, disc, Teletherapy Co-60, Cs-137 1,350–27,000 cylinder, pellet wafer, disc, cylin- Blood irradiation Co-60, Cs-137 50–2,700 der Co-60, Cs-137, Cs-131, I-125, Pd- seed, needle, flat 103, Sr-90/Y-90 Brachytherapy 0.0014–11 band, cylinder, (Ra-226, Am-241, dowel, plaques Au-198, Ru-106, Cf-252) Industrial Industrial irradiation Co-60, Co-137 2,700–11,000,000 slug, pellet, wafer Ir-192, Cs-137, Industrial Radiography 5–250 cylinder Co-60, Ra-226 Cs-137, Cf-252, cylinder, dowel, Nuclear Well-logging 0.027–22 Am-241/Be powder Cs-137, Co-60, Am-241, Cf-252, Inspection Gauges Sr-90, Kr-85, Tl- 0.027–27 disc, cylinder 204, Ra-226/Be, Am-241/Be Am-241, Cs-137, Co-60, I-125, wafer, disc, pellet, Calibration Standards Sr-90, Ra-226, up to 0.001 epoxy, clump, liq- U-235, Pu-239, uid solution Cf-252 Research wafer, disc, cylin- Irradiators Cs-137, Co-60 27–27,000 der Energy Production Nuclear Power Generation U-235, Pu-239 >1,000,000 pellet, rod ceramic wafer, Radiothermal Generator Sr-90, Pu-238 30,000–300,000 cylinder

DRDC-RDDC-2020-D130 19 Table 6: A partial list of the appearance and radiation type of commercially used radioisotopes.

Radionuclide Colour(form) Emission type Half-life silver-white(pure), Americium-241 black, tan, pink, yel- α, γ, n (in mixtures) 433 a low(oxide ceramic) silver-white, Californium-252 grey(oxide pellet or α, γ, n 2.65 a wire) Silver-white(pure), Cesium-137 white, colourless, β,γ 30.2 a golden yellow(salt) Silver-grey(pure), Cobalt-60 red, pink, blue, β,γ 5.27 a green, black(metal) Silver-white (pure), green, black, Iridium-192 β,γ 73.8 d red(metal cylinder or wire) Silver-grey(pure), yellow-green, brown, 238: 86.4a, 239: Plutonium-238/239 α, γ, n (in mixtures) black (metal or ce- 24,400 a ramic) Silver-white (pure), white, yellow-white Radium-226 α, γ, n (in mixtures) 1600 a (pellet or salt solution) Yellow-silver (pure), Strontium-90 white, colourless, β 28.2 a grey (ceramic) Silver-white (pure), 235: 7.13 x 108 a, Uranium-235/238 yellow, green, α, β, γ, n 238: 4.51 x 109 a brown-black (metal)

20 DRDC-RDDC-2020-D130 4.3.3 Medical Applications

The most common use of radiation in medical treatment comes from the application of x-rays to examine bones in the human body without surgery. This can be extended for use in computerized axial tomography, and particle-based techniques such as positron emission tomography, which are also becoming more common. These are safer techniques in that, unlike a radioactive element, they can be turned on and made safe: no power generally means no continual production of radiation.

Isotopes are used for a wide variety of specific purposes. A fairly exhaustive list is provided in AnnexB.

4.3.3.1 Teletherapy [7]

Teletherapy refers to radiation therapy given by an external radiation source at a distance from the body. It is the most common type of radiotherapy used in cancer treatment and is usually given by a cobalt unit, which delivers high energy gamma rays, or a linear accelerator, which can deliver high-energy x-rays or electrons. In the most common scheme, treatment is given daily for a period of 4–8 weeks.

To deliver an even dose of radiation to the target, which may be several centimetres thick, the radiation source is placed at a distance from the patient (usually 80–150 cm). Healthy tissue, including skin, in the path of the beam can also be irradiated. To reduce this effect, higher-energy beams are used for deeper tumors and treatment is delivered from several angles, which maximizes the dose at the intersection.

Newer techniques, such as 3-D conformal radiotherapy, intensity modulated radiotherapy, and image guided radiotherapy, obtain an extremely accurate shaping of the target that receives the prescribed dose of radiation. These techniques allow radiotherapy to deliver a lower dose of radiation to healthy tissues and a higher dose to the tumor. Patients receiv- ing radiotherapy experience no physical sensation while being exposed to the radiation; it resembles very much having an X-ray. Side effects do, however, occur. In rapidly dividing tissues, such as mucosa and skin, early reactions are similar to sunburn. In slow dividing cells, for instance those in the kidney or vasculature supporting the brain and spinal cord, tolerance to radiation is lower. If treated above a certain threshold, they are at risk of developing late effects that usually become apparent many months after treatment.

4.3.3.2 Blood Irradiation [8]

Irradiated blood is used to prevent transfusion-associated graft-versus host disease (TA- GvHD) in people who received bone marrow transplants or transfusions of blood components. The disease can also affect a person who receives a blood transfusion from a close relative who is homozygous for certain human leukocyte antigens (HLA).

DRDC-RDDC-2020-D130 21 The irradiation process kills the donor’s T-lymphocytes which are the main cause of TA- GvHD. Unless the T-lymphocytes are destroyed, they will graft themselves in the recipient’s tissues. If the person’s own immune system is incapable of mounting an immune response to them, the T-lymphocytes get the upper hand and attack the recipient’s body as if it were a foreign invader.

Blood is irradiated by exposing the bags to gamma radiation from cobalt-60 or cesium- 137 using an instrument called an irradiator. The minimum radiation dose to kill the T- lymphocytes of 25 Gy. Another method uses x-rays generated by a linear accelerator.

Blood does not become radioactive after it is irradiated, and it does not present a danger to the recipient or their family members. The process does not damage healthy blood cells or platelets, but it does shorten the shelf life slightly because the cells lose some of their salt content.

4.3.3.3 Brachytherapy [9]

Brachytherapy is a form of radiation therapy, by which a radioactive source is placed close to the tumor, either directly adjacent to it or inside the tumor itself. This procedure delivers a high dose of radiation to the target with only a minimal dose affecting the surrounding tissues.

Brachytherapy uses sealed radioactive sources that are placed directly into tumors (inter- stitial) or in body cavities (intracavitary). One example is the implant of some 125Iodine inside the prostate gland, which deliver the required dose during the entire period they are active. More commonly, however, a radioactive source is inserted into the body and removed when the time calculated for the delivery of a specified radiation dose has elapsed. This time period needs to be determined by an oncologist.

Treatment can be delivered according to the dose rate (dose given during a determined period of time) via:

• Low dose rate (LDR) brachytherapy, which utilizes cesium-137 and iridium-192 sources, among others. In this technique, an applicator is placed in the cavity or inside the tumor and the source is fed into the applicator, once the patient is in a shielded room. They remain in isolation until the source is removed (usually 12–24 hours). This process often requires hospital admission.

• High dose rate (HDR) brachytherapy, which can be delivered with miniaturized sources of cobalt-60 or iridium-192, which allows a dose rate greater than 12 Grays per hour, accounting for short times of treatment. For this reason, HDR can be administered as an outpatient treatment. Brachytherapy is a key component of radiation treatment for gynecological cancers. Other indications for brachytherapy include: prostate, breast, soft tissue sarcomas, some head and neck tumors, and skin cancers.

22 DRDC-RDDC-2020-D130 4.3.4 Research Applications

Radioactive materials are used for many research applications, for example, to expose cell cultures, insects, plants, and animals to ionizing radiation for molecular biology, biotechnol- ogy, and pharmaceutical research. Research irradiators are sometimes called “self-contained” irradiators. Like blood irradiators, they are moderately sized and heavily shielded—the radioactive source is completely contained within and shielded by the machine. When the irradiator is in use, the sample is safely moved by the irradiator to the internal irradiation chamber, where it is exposed to the radiation source. Self-contained research irradiators most commonly use cesium-137 or cobalt-60.

4.3.5 Energy Applications

Radioactive materials are also used for energy purposes. For example, strontium-90 is used as fuel for thermoelectric generators. Fissile nuclear materials, such as uranium and plutonium, are used to fuel nuclear power reactors.

4.3.6 Transportation and Packaging

A vital step in identifying illegal transport and storage of radioactive materials is the ability to recognize legitimate transport and packaging. Hundreds of millions of packages containing radioactive materials are transported each year for valid reasons. As an example, it was reported in 2004 that three million such packages were transported by highway, rail, air, or water in the United States alone. Strict national and international administrative controls regulate the transport of radioactive materials. In general, radioactive material shipments must include internationally recognized package labels and shipment manifest declarations which indicate the nature of the shipment contents. Radioactive materials are shipped in their most stable forms, typically as solids. The shipment of radioactive liquids or gases usually requires additional precautions.

DRDC-RDDC-2020-D130 23 References

[1] Soppera, N., Bossant, M., and Dupont, E. (2014), JANIS 4: An Improved Version of the NEA Java-based Nuclear Data Information System, Nuclear Data Sheets, Vol. 120.

[2] ICRP (1991), ICRP publication 60: 1990 recommendations of the International Commission on Radiological Protection, Number 60, Elsevier Health Sciences.

[3] Protection, R. (2007), ICRP publication 103, Ann ICRP, 37(2.4), 2.

[4] NATO (1994), NATO Handbook on the Medical Aspects of NBC Defensive Operations [AMedP-6(B)], NATO.

[5] University of Florida Department of Environmental and Health Safety (2011), Radiation Protection, Ch. 3, p. 52, University of Florida.

[6] Canadian Nuclear Safety Commission (2013), Fact Sheet: Natural Background Radiation. Online and Handout.

[7] International Atomic Energy Agency (2019), Cancer Treatment: Teletherapy. Online, https://www.iaea.org/topics/cancer-treatment-radiotherapy.

[8] Alter, H. J. and Klein, H. G. (2008), The hazards of blood transfusion in historical perspective, Blood, The Journal of the American Society of Hematology, 112(7), 2617–2626.

[9] International Atomic Energy Agency (2019), Cancer Treatment: Brachytherapy. Online, https://www.iaea.org/topics/cancer-treatment-brachytherapy, accessed 04 May 2020.

[10] World Nuclear Association, Radioisotopes in Medicine. Online, https://world-nuclear.org/information-library/non-power-nuclear- applications/radioisotopes-research/radioisotopes-in-medicine.aspx, accessed 04 May 2020.

24 DRDC-RDDC-2020-D130 Annex A SI Units and Conversions

The Système International (SI) uses prefixes with the units to write very large and very small measurements in a concise manner. The common prefixes used with ionizing radiation units are shown in the tables below for comparison and quick reference. Included are conversions for units of becquerel and curie, for units of gray and rad and for units of rem and sievert.

Table A.1: Table of SI prefixes.

Prefix Symbol Exponent Tera T 1012 Giga G 109 Mega M 106 kilo k 103 base unit none 1 milli m 10−3 micro µ 10−6 nano n 10−9 pico p 10−12

While the SI unit of activity is the becquerel (Bq), the curie (Ci) is still commonly used.

Table A.2: Conversion between becquerel and curie units.

1 terabecquerel (TBq) = 27 curie (Ci) 1 gigabecquerel (GBq) = 27 millicurie (mCi) 1 megabecquerel (MBq) = 27 microcurie (µCi) 1 kilobecquerel (kBq) = 27 nanocurie (nCi) 1 becquerel (Bq) = 27 picocurie (pCi) 1 kilocurie (kCi) = 37 terabecquerel (TBq) 1 curie (Ci) = 37 gigabecquerel (GBq) 1 millicurie (mCi) = 37 megabecquerel (MBq) 1 microcurie (µCi) = 37 kilobecquerel (kBq) 1 nanocurie (nCi) = 37 becquerel (Bq)

DRDC-RDDC-2020-D130 25 The gray (Gy) and the rad are the SI and traditional units of absorbed dose, respectively.

Table A.3: Conversion between gray and rad units.

1 gray (Gy) = 100 rad (rad) 1 milligray (mGy) = 0.1 rad or 100 millirad (mrad) 1 microgray (µGy) = 100 microrad (µrad) 1 nanogray (nGy) = 100 nanorad (nrad) 1 kilorad (krad) = 10 gray (Gy) 1 rad (rad) = 10 milliGray (mGy) 1 millirad (mrad) = 10 microgray (µGy) 1 microrad (µrad) = 10 nanogray (nGy)

The sievert (Sv) and the rem are the SI and traditional units of equivalent dose and effective dose. Table A.4: Conversion between sievert and rem units.

1 sievert (Sv) = 100 rem (rem) 1 millisievert (mSv) = 100 millirem (mrem) 1 microsievert (µSv) = 100 microrem (µrem) 1 nanosievert (nSv) = 100 nanorem (nrem) 1 kilorem = 10 sievert (Sv) 1 rem (rem) = 10 millisievert (mSv) 1 millirem (mrem) = 10 microsievert (µSv) 1 microrem (µrem) = 10 nanosievert (nSv)

26 DRDC-RDDC-2020-D130 Annex B Radioisotopes used in Medical Applications

Radioisotopes produced in nuclear reactors are in Table B.1[10].

Table B.1: Medical uses of reactor-generated radioisotopes. Isotope Half-life Use Bismuth-213 46 min Used for targeted alpha therapy (TAT), especially cancers, as it has a high energy (8.4 MeV). Cesium-131 9.7 d Used for brachytherapy, emits soft x-rays. Cesium-137 30 yr Used for low-intensity sterilisation of blood. Chromium-51 28 d Used to label red blood cells for monitoring, and to quantify gastro-intestinal protein loss or bleeding. Cobalt-60 5.27 yr Formerly used for external beam radiotherapy, now almost universally used for sterilising. High-specific- activity (HSA) Co-60 is used for brain cancer treatment. Dysprosium-165 2 h Used as an aggregated hydroxide for synovectomy treatment of arthritis. Erbium-169 9.4 d Used for relieving arthritis pain in synovial joints. Holmium-166 26 h Being developed for diagnosis and treatment of liver tumours. Iodine-125 60 d Used in cancer brachytherapy (prostate and brain), also diagnostically to evaluate the filtration rate of kid- neys and to diagnose deep vein thrombosis in the leg. It is also widely used in radioimmuno-assays to show the presence of hormones in tiny quantities. Iodine-131 8 d (Fission product): Widely used in treating thyroid cancer and in imaging the thyroid; also in diagnosis of abnormal liver function, renal & kidney blood flow, and urinary tract obstruction. A strong gamma emitter, but used for beta therapy. Iridium-192 74 d Supplied in wire form for use as an internal radiotherapy source for cancer treatment (used then removed), e.g., for prostate cancer. Strong beta emitter for high dose-rate brachytherapy. Iron-59 46 d Used in studies of iron metabolism in the spleen. Lead-212 10.6 h Used in TAT for cancers or alpha radioimmunother- apy, with decay products Bi-212 (λ = 1 h) and Po- 212 delivering the alpha particles. Used especially for melanoma, breast cancer and ovarian cancer. Demand is increasing.

DRDC-RDDC-2020-D130 27 Table B.1: Medical uses of reactor-generated radioisotopes (continued). Isotope Half-life Use Lutetium-177 6.7 d Lu-177 is increasingly important as it emits just enough gamma for imaging while the beta radiation does the therapy on small (e.g., endocrine) tumours. Its half-life is long enough to allow sophisti- cated preparation for use. It is usually produced by neutron activation of natural or enriched lutetium-176 targets. Molybdenum-99 66 h (Fission product): Used as the parent in a generator to produce technetium-99m. Palladium-103 17 d Used to make brachytherapy permanent implant seeds for early stage prostate cancer. Emits soft x-rays. Phosphorus-32 14 d Used in the treatment of polycythemia vera (excess red blood cells). Beta emitter. Potassium-42 12 h Used for the determination of exchangeable potassium in coronary blood flow. Radium-223 11.4 d Used for TAT brachytherapy, lodges in bone, emits soft x-rays. Rhenium-186 3.8 d Used for pain relief in bone cancer. Beta emitter with weak gamma for imaging. Rhenium-188 17 h Used to beta irradiate coronary arteries from an an- gioplasty balloon. Samarium-153 47 h Sm-153 is very effective in relieving the pain of secondary cancers lodged in the bone, sold as Quadramet. Also very effective for prostate and breast cancer. Beta emitter. Selenium-75 120 d Used in the form of seleno-methionine to study the production of digestive enzymes. Sodium-24 15 h For studies of electrolytes within the body. Strontium-89 50 d (Fission product): Very effective in reducing the pain of prostate and bone cancer. Beta emitter. Technetium-99m 6 h Used to image the skeleton and heart muscle in particular, but also for brain, thyroid, lungs (perfusion and ventilation), liver, spleen, kidney (structure and filtration rate), gall bladder, bone marrow, salivary and lacrimal glands, heart blood pool, infection, and numerous specialised medical studies. Produced from Mo-99 in a generator. The most common radioisotope for diagnosis, accounting for over 80% of scans. Thorium-227 18.7 d Used for TAT, decays to Ra-223.

28 DRDC-RDDC-2020-D130 Table B.1: Medical uses of reactor-generated radioisotopes (continued). Isotope Half-life Use Xenon-133 5 d (Fission product): Used for pulmonary & lung ventilation studies. Ytterbium-169 32 d Used for cerebrospinal fluid studies in the brain. Ytterbium-177 1.9 h Progenitor of Lu-177. Yttrium-90 64 h (Fission product): Used for cancer brachytherapy and as silicate colloid for the relieving the pain of arthritis in larger synovial joints. Pure beta emitter and of growing significance in therapy, especially liver cancer. Note: Radioisotopes of gold and ruthenium are also used in brachytherapy.

Radioisotopes generated using cyclotrons are in Table B.2[10].

Table B.2: Medical uses of cyclotron-generated radioisotopes. Isotope Half-life Use Actinium-225 10 d Used for TAT especially prostate cancers. Astatine-211 7.2 h Use for TAT. Bismuth-213 46 min Used for TAT. Carbon-11 Positron emitter used in PET for studying brain physi- ology and pathology, in particular for localising epilep- tic focus, and in dementia, psychiatry, and neurophar- macology studies. They also have a significant role in cardiology. Nitrogen-13 Positron emitter used in PET for studying brain physi- ology and pathology, in particular for localising epilep- tic focus, and in dementia, psychiatry, and neurophar- macology studies. They also have a significant role in cardiology. Oxygen-15 Positron emitter used in PET for studying brain physi- ology and pathology, in particular for localising epilep- tic focus, and in dementia, psychiatry, and neurophar- macology studies. They also have a significant role in cardiology.

DRDC-RDDC-2020-D130 29 Table B.2: Medical uses of cyclotron-generated radioisotopes (continued). Isotope Half-life Use Fluorine-18 110 min Positron emitter used in PET for studying brain physi- ology and pathology, in particular for localising epilep- tic focus, and in dementia, psychiatry, and neurophar- macology studies. They also have a significant role in cardiology. F-18 in FDG (fluorodeoxyglucose) has become very important in detection of cancers and the monitoring of progress in their treatment, using PET. Cobalt-57 272 d Used as a marker to estimate organ size and for in- vitro diagnostic kits. Copper-64 13 h Used to study genetic diseases affecting copper metabolism, such as Wilson’s and Menke’s diseases, for PET imaging of tumours, and also cancer therapy. Copper-67 2.6 d Beta emitter, used in therapy. Gallium-67 78 h Used for tumour imaging and locating inflammatory lesions (infections). Gallium-68 68 min Positron emitter used in PET and PET-CT units. De- rived from germanium-68 in a generator. Germanium-68 271 d Used as the parent in a generator to produce Ga-68. Indium-111 2.8 d Used for specialist diagnostic studies, e.g., brain studies, infection and colon transit studies. Also for locating blood clots, inflammation and rare cancers. Iodine-123 13 h Increasingly used for diagnosis of thyroid function, it is a gamma emitter without the beta radiation of I-131. Iodine-124 4.2 d Tracer, with longer life than F-18, one-quarter of decays are positron emission so used with PET. Also used to image the thyroid using PET. Krypton-81m 13 sec from rubidium-81 (λ = 4.6 h), Kr-81m gas can yield functional images of pulmonary ventilation, e.g., in asthmatic patients, and for the early diagnosis of lung diseases and function. Rubidium-82 1.26 min Convenient PET agent in myocardial perfusion imaging. Strontium-82 25 d Used as the parent in a generator to produce Rb-82. Thallium-201 73 h Used for diagnosis of coronary artery disease other heart conditions such as heart muscle death and for location of low-grade lymphomas. It is the most commonly used substitute for technetium-99 in cardiac- stress tests.

30 DRDC-RDDC-2020-D130 List of Symbols/Abbreviations/Acronyms/Initialisms

ALARA as low as reasonably achievable Bq becquerel CANSOFCOM Canadian Special Operational Forces Command CAUSE Canadian Arctic Underwater Sentinel Experimentation CFB Canadian Forces Base Ci curie CTTC Counterterrorism and Training Centre DRDC Defence Research and Development Canada eV electronvolt Gy Gray HDR high dose rate HEU highly enriched uranium HLA human leukocyte antigens HVL half-value layer PIP pre-program instruction package Q quality factor R roentgen RDD radiological dispersal device RED radiological exposure device rem roentgen equivalent man RN Tech Group Radiation and Nuclear Technologies Group SI Système Internationale SNM special nuclear material Sv sievert TA-GvHD transfusion-associated graft-versus host disease TVL tenth-value layer UNSCEAR United Nations Scientific Committee on the Effects of Atomic Radiation

DRDC-RDDC-2020-D130 31 Glossary Radiation Terminology

This section is a glossary of terms that are in this literature and that may come up during this course. It is here as reference material, not as required reading.

Absorbed Dose:

The amount of energy deposited by ionizing radiation in a unit mass of tissue. It is J expressed in units of joule per kilogram ( kg ), and called the “Gray” (Gy). Actinides:

Elements in the periodic table with atomic numbers from 90 to 103 (thorium to lawrencium). These are elements with a higher atomic number than actinium, which has an atomic number of 89. They include most of the well-known elements found in nuclear reactions. Actinides with atomic numbers higher than 92 do not occur naturally but are produced artificially by bombarding other elements with particles. Some of the actinides include plutonium, curium, and californium.

Activity:

The property of certain nuclides of emitting radiation by spontaneous transformation of their nuclei. Various units of (radio)activity have been used including curie (1 Ci = 3.7 x 1010 disintegrations per second) and Becquerel (1 Bq = 1 disintegration per second).

Acute exposure:

An exposure to radiation that occurred in a matter of minutes rather than in longer, continuing exposure over a period of time.

Air kerma:

The initial kinetic energy of the primary ionizing particles (photoelectrons, Compton electrons,positron/electron pairs from photon radiation, and scattered nuclei from fast neutrons produced by the interaction of the incident uncharged radiation in a small volume of air, when it is irradiated by an x-ray beam. Unit of measure is the Gray.

ALARA:

Acronym for “As Low As Reasonably Achievable”; means making every reasonable effort to maintain exposures to ionizing radiation as far below the dose limitsas practical. This is a key principle in radiation protection and safety.

32 DRDC-RDDC-2020-D130 Alpha Particle:

The nucleus of a helium atom, made up of two neutrons and two protons with a charge of +2. Certain radioactive nuclei emit alpha particles. Alpha particles generally carry more energy than gamma rays or beta particles, and deposit that energy very quickly while passing through tissue. Alpha particles can be stopped by a thin layer of light material, such as a sheet of paper, and cannot penetrate the outer, dead layer of skin. Therefore,they do not damage living tissue when outside the body. When alpha-emitting atoms are inhaled or swallowed, however, they are especially damaging because they transfer relatively large amounts of ionizing energy to living cells.

Background radiation:

Ionizing radiation from natural sources, such as terrestrial radiation due to radionuclides in the soil or cosmic radiation originating in outer space.

Becquerel (Bq):

The amount of a radioactive material that will undergo one decay (disintegration) per second.

Beta particles:

Electrons ejected from the nucleus of a decaying atom. Although they can be stopped by a thin sheet of aluminum, beta particles can penetrate the dead skin layer, potentially causing burns. They can pose a serious direct or external radiation threat and can be lethal depending on the amount received. They also pose a serious internal radiation threat if beta-emitting atoms are ingested or inhaled.

Bioassay:

A measurement of radioactive materials present inside a person’s body through analysis of the person’s blood, urine, feces, or sweat.

Biodosimetry:

The use of physiological, chemical or biological markers of exposure of human tissues to ionizing radiation for the purpose of reconstructing doses to individuals or populations.

Biological half-life:

The time required for one half of the amount of a substance, such as a radionuclide, to be expelled from the body by natural metabolic processes, not counting radioactive decay, once it has been taken in through inhalation, ingestion, or absorption.

DRDC-RDDC-2020-D130 33 Bremßtrahlung:

German for “braking radiation,” this is radiation that is produced when charged particles are slowed down in matter and some of their kinetic energy is converted into electromagnetic energy in the form of x-rays. This typically occurs when beta particles are stopped in dense (high Z) materials.

Chain reaction:

A process that initiates its own repetition. In a fission chain reaction,a fissile nucleus absorbs a neutron and fissions(splits) spontaneously, releasing additional neutrons. These, in turn,can be absorbed by other fissile nuclei, releasing still more neutrons. A fission chain reaction is self-sustaining when the number of neutrons released ina given time equals or exceeds the number of neutrons lost by absorption in non-fissile material or by escape from the system.

Chronic exposure:

Exposure to a substance over a long period of time, possibly resulting in adverse health effects.

Cloudshine:

Also referred to as skyshine, this is radiation that is emitted upwards but is scattered back to the ground by the air. Typically, β particles and gamma rays form the components of cloudshine. This is most common above heavily irradiated areas and outside of nuclear plants, nuclear waste repositories and medical facilities that have no or inadequate shielding above their radiation source. This can cause higher than expected radiation readings outside of an area or facility.

Committed dose:

A dose that accounts for continuing exposures expected to be received over a long period of time (such as 30, 50, or 70 years) from radioactive materials that were deposited inside the body.

Contamination:

The deposition of unwanted radioactive material on the surfaces of structures, areas, objects, or people where it may be external or internal. Contamination means that radioactive materials in the form of gases, liquids, or solids are released into the environment and contaminate people externally, internally, or both. An external surface of the body, such as the skin, can become contaminated, and if radioactive materials get inside the body through the lungs, gut, or wounds, the contaminant can become deposited internally.

34 DRDC-RDDC-2020-D130 Contamination, fixed:

Fixed skin contamination is that which remains after bathing or attempted decontamination. Contamination is assumed to be removed by natural processes within 336 hours (14 days) after deposition on the skin.

Contamination, loose:

Loose skin contamination is that which is removable by bathing or decontamination.

Cosmic radiation:

Radiation produced in outer space when heavy particles (nuclei of all known natural elements) bombard the earth.

Coulomb:

The international system (SI) unit of electric charge. A coulomb is the quantity of charge passing a cross section of conductor in one second when the current is one ampere.

Criticality:

A fission process where the neutron production rate equals the neutron loss rateto absorption or leakage. A nuclear reactor is “critical” when it is operating.

Critical mass:

The minimum amount of fissile material that can achieve a self-sustaining nuclear chain reaction.

Curie (Ci):

The traditional measure of radioactivity based on the observed decay rate of 1 gram of radium. One curie of radioactive material will have 37 billion disintegrations in 1 second.

Decay chain (decay series):

The series of decays that certain radioisotopes go through before reaching a stable form. For example, the decay chain that begins with uranium-238 (U-238) ends in lead-206 (Pb-206) after forming isotopes,such as uranium-234 (U-234), thorium-230 (Th-230), radium-226 (Ra-226), and radon-222 (Rn-222).

Decay constant:

The fraction of a number of atoms of a radionuclide that disintegrates in a unit of time. The decay constant is inversely proportional to the radioactive half-life.

DRDC-RDDC-2020-D130 35 Decay products (or daughter products):

The isotopes or elements formed and the particles and high-energy electromagnetic radiation emitted by the nuclei of radionuclides during radioactive decay. Also known as “decay chain products” or “progeny” (the isotopes and elements). A decay product may be either radioactive or stable.

Decay (radioactive):

Disintegration of the nucleus of an unstable atom by the release of radiation.

Decontamination (radioactive):

The reduction or removal of radioactive contamination from a structure, object, or person.

Decorporation:

The removal of radioactive isotopes from the body using specific drugs called “decorporation agents.”

Depleted uranium:

Uranium containing less than 0.7% uranium-235, the amount found in natural uranium.

Deterministic effect:

An effect that can be related directly to the radiation dose received.The severity increases as the dose increases. A deterministic effect typically has a threshold below which the effect will not occur.

Dirty bomb:

A device designed to spread radioactive material by conventional explosives when the bomb explodes. A dirty bomb kills or injures people through the initial blast of the conventional explosive and spreads radioactive contamination over possibly a large area—hence the term “dirty.” Such bombs could be miniature devices or large truck bombs. A dirty bomb is much simpler to make than a true nuclear weapon.

Dose (radiation):

Radiation absorbed by a person’s body. Several different terms describe radiation dose.

36 DRDC-RDDC-2020-D130 Dose coefficient:

The factor used to convert radionuclide intake to dose. Usually expressed as dose per unit intake (e.g., sieverts per becquerel).

Dose equivalent:

The product of absorbed dose to a given organ or tissue multiplied by a quality factor (also known as a weighting factor [WF]), and then sometimes multiplied by other necessary modifying factors, to account for the potential for a biological effect resulting from the absorbed dose. It is expressed numerically in rem (traditional units) or sieverts (SI units).

Dose rate:

The radiation dose delivered per unit of time.

Effective dose:

A calculated quantity developed by the ICRP (1991) for purposes of radiation protection. The effective dose is assumed to be related to the risk of a radiation-induced cancer or a severe hereditary effect. It takes into account (1) the absorbed doses that will be delivered to the separate organs or tissues of the body during the lifetime of an individual due to intakes of radioactive materials; (2) the absorbed doses due to irradiation by external sources; (3) the relative effectiveness of different radiation types in inducing cancers or severe hereditary effects; (4) the susceptibility of individual organs to develop a radiation-related cancer or severe hereditary effect; (5) considerations of the relative importance of fatal and non-fatal effects; and, (6) the average years of life lost from a fatal health effect. Thus, the effective dose is a quantity calculated by multiplying the equivalent dose received by every significantly irradiated tissue in the body by a respective tissue weighting factor (this factor reflects the risk of radiation- induced cancer to that tissue) and summing together the individual tissue results to obtain the effective dose. Such a dose, in theory, carries with it the same risk ofcancer as would an equal equivalent dose delivered uniformly to the whole body.

Effective half-life:

The time required for the amount of a radionuclide deposited in a living organism to be diminished by 50% as a result of the combined action of radioactive decay and biological elimination.

Electromagnetic radiation:

A travelling wave motion that results from changing electric and magnetic fields. Types of electromagnetic radiation range from those of short wavelength, like x-rays and gamma rays, through the ultraviolet, visible, and infrared regions, to radar and radio waves of relatively long wavelengths.

DRDC-RDDC-2020-D130 37 Electron:

1 An elementary particle with a negative electrical charge and a mass 1837 that of the proton. Electrons surround the nucleus of an atom because of the attraction between their negative charge and the positive charge of the nucleus. A stable atom will have as many electrons as it has protons. The number of electrons that orbit an atom determine its chemical properties.

Electronvolt (eV):

A unit of energy equivalent to the amount of energy gained by an electron when it passes from a point of low potential to a point one volt higher in potential.

Element:

1) All isotopes of an atom that contain the same number of protons. For example,the element uranium has 92 protons, and the different isotopes of this element may contain 134 to 148 neutrons. 2) In a reactor, a fuel element is a metal rod containing the fissile material.

Enriched uranium:

Uranium in which the proportion of the isotope uranium-235 has been increased by removing uranium-238.

Exposure (radiation):

A measure of ionization in air caused by x-rays or gamma rays only. The unit of C exposure most often used is the Roentgen. In SI units the equivalent would be kg , but is not commonly used as the Roentgen specifically relates to dry air.

Exposure pathway:

A route by which a radionuclide or other toxic material can enter the body. The main exposure routes are inhalation, ingestion,absorption through the skin, and entry through a cut or wound in the skin.

Exposure rate:

A measure of the ionization produced in air by x-rays or gamma rays per unit of time (frequently expressed in roentgens per hour).

External irradiation (or external exposure):

External irradiation occurs when all or part of the body is exposed to penetrating radiation from an external source. During exposure, this radiation can be absorbed by the body or it can pass completely through. A similar thing occurs during an ordinary

38 DRDC-RDDC-2020-D130 chest x-ray. Following external exposure, an individual is not radioactive and can be treated like any other patient. Gamma or photon radiation exposure from a terrorist nuclear event or radiation dispersal device would make the victim at risk for Acute Radiation Syndrome, depending on the dose received.

Fallout (nuclear):

Minute particles of radioactive debris that descend slowly from the atmosphere after a nuclear explosion.

Fissile material

Any material in which neutrons can cause a fission reaction. The three primary fissile materials are uranium-233, uranium-235, and plutonium-239.

Fission:

The splitting of a nucleus into at least two other nuclei that releases a large amount of energy. Two or three neutrons are usually released during this transformation.

Fusion:

A reaction in which two lighter nuclei unite to form a heavier one, releasing energy in the process. Reactions of this type are responsible for the release of energy in stars or in thermonuclear devices.

Gamma rays:

High-energy electromagnetic radiation emitted by certain radionuclides when their nuclei transition from a higher to a lower energy state. These rays have high energy and a short wave-length. The spectrum of gamma rays emitted from a given isotope have the same energy, a characteristic that enables scientists to identify which gamma emitters are present in a sample (an isotope going through a specific decay may have multiple energies of gamma rays, but all of those energies are unique to that specific decay. If a second, identical nucleus decays the same way it will emit the same energy of gamma rays). Gamma rays penetrate tissue farther than do beta or alpha particles but leave a lower concentration of ions in their path to potentially cause cell damage. Gamma rays are very similar to x-rays.

Gray (Gy):

The new international system (SI) unit of radiation dose, expressed as absorbed energy per unit mass of tissue. The SI unit “Gray” has replaced the older “rad” designation. (1 Gy = 1 joule/kilogram = 100 rad). Gray can be used for any type of radiation (e.g., alpha, beta, neutron, gamma), but it does not describe the biological effects of different radiations. Biological effects of radiation are measured in units of “Sievert” (or the older designation “rem”).

DRDC-RDDC-2020-D130 39 Groundshine:

Gamma and/or beta radiation from radioactive material deposited on the ground, including as fallout after a nuclear detonation.

Half-life:

The time any substance takes to decay to half of its original amount.

Highly enriched uranium (HEU):

Uranium that is enriched to above 20% uranium-235 (U-235). Weapons-grade HEU is enriched to above 90% in U-235.

Hotspot:

Any place where the level of radioactive contamination is considerably greater than the area around it.

Incorporation:

Incorporation refers to the uptake of radioactive materials by body cells, tissues, and target organs such as bone, liver, thyroid, or kidney. In general, radioactive materials are distributed throughout the body based upon their chemical properties. Incorpo- ration cannot occur unless contamination has occurred. Incorporation is also called internal contamination.

Ingestion:

1) The act of swallowing; and, 2) In the case of radionuclides or chemicals, swallowing radionuclides or chemicals by eating or drinking.

Inhalation:

1) The act of breathing in; and, 2) In the case of radionuclides or chemicals, breathing in radionuclides or chemicals.

Internal exposure:

Exposure to radioactive material taken into the body.

Inverse square law:

The relationship that states that electromagnetic radiation intensity is inversely proportional to the square of the distance from a point source.

40 DRDC-RDDC-2020-D130 Ionization:

The process of adding one or more electrons to, or removing one or more electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical dis- charges, or nuclear radiation can cause ionization.

Ionizing radiation:

Any radiation capable of displacing electrons from atoms, thereby producing ions. High doses of ionizing radiation may produce severe skin or tissue damage.

Irradiation:

Exposure to radiation.

Isotope:

A nuclide of an element having the same number of protons but a different number of neutrons.

Kerma:

The initial kinetic energy of the primary ionizing particles (photoelectrons, Compton electrons, positron/electron pairs from photon radiation, and scattered nuclei from fast neutrons) produced by the interaction of the incident uncharged radiation, per unit mass of interacting medium. Unit of measure is gray.

Neutron:

A small atomic particle possessing no electrical charge, typically found within an atom’s nucleus. Neutrons are, as the name implies, neutral in their charge. That is, they have neither a positive nor a negative charge. A neutron has about the same mass as a proton.

Non-ionizing radiation:

Radiation that has lower energy levels and longer wavelengths than ionizing radiation. It is not strong enough to affect the structure of atoms it contacts but is strong enough to heat tissue and can cause harmful biological effects. Examples include radio waves, microwaves, visible light, and infrared from a heat lamp.

Non-stochastic effect:

See deterministic effect.

DRDC-RDDC-2020-D130 41 Nuclear energy:

The heat energy produced by the process of nuclear fission within a nuclear reactor or by radioactive decay.

Nuclear fuel cycle:

The steps involved in supplying fuel for nuclear power plants. It can include mining, milling, isotopic enrichment, fabrication of fuel elements, use in reactors, chemical reprocessing to recover the fissile material remaining in the spent fuel, re-enrichment of the fuel material refabrication into new fuel elements, and waste disposal.

Nuclear reactor:

A device in which a controlled, self-sustaining nuclear chain reaction can be main- tained with the use of cooling to remove generated heat.

Nuclear tracers:

Radioisotopes that give doctors the ability to “look” inside the body and observe soft tissues and organs, in a manner similar to the way x-rays provide images of bones. A radioactive tracer is chemically attached to a compound that will concentrate naturally in an organ or tissue so that an image can be taken.

Penetrating radiation:

Radiation that can penetrate the skin and reach internal organs and tissues. Photons (gamma rays and x-rays), neutrons, and protons are penetrating radiations. However, alpha particles and all but extremely high-energy beta particles are not considered penetrating radiation.

Personal protective equipment (PPE):

Clothing and/or equipment worn by workers (including first responders and first re- ceivers) to prevent or mitigate job-related illness or injury. Individual PPE elements can include respiratory and percutaneous protective equipment.

Photon:

A discrete “packet” of pure electromagnetic energy. Photons have no mass and travel at the speed of light. The term “photon” was developed to describe energy when it acts like a particle (causing interactions at the molecular or atomic level), rather than a wave. Gamma rays and x-rays are photons.

42 DRDC-RDDC-2020-D130 Plume:

The material spreading from a particular source and travelling through environmental media, such as air or ground water. For example, a plume could describe the dispersal of particles, gases, vapors, and aerosols in the atmosphere, or the movement of contamination through an aquifer(for example, dilution, mixing, or adsorption onto soil).

Quality factor (Q):

The factor by which the absorbed dose (rad or gray) must be multiplied to obtain a quantity that expresses, on a common scale for all ionizing radiation, the biological damage (rem or sievert) to the exposed tissue. It is used because some types of radiation, such as alpha particles, are more biologically damaging to live tissue than other types of radiation when the absorbed dose from both is equal. The term, quality factor, has now been replaced by “radiation weighting factor” in the latest system of recommendations for radiation protection.

Rad (radiation absorbed dose):

A basic unit of absorbed radiation dose. It is a measure of the amount of energy absorbed by the body. The rad is the traditional unit of absorbed dose. It is being replaced by the unit gray (Gy), which is equivalent to 100 rad. One rad equals the dose delivered to an object of 100 ergs of energy per gram of material.

Radiation:

Energy moving in the form of particles or waves. Familiar radiations are heat, light, radio waves, and microwaves. Ionizing radiation is a very high-energy form of electromagnetic radiation.

Radiation protection:

Sometimes known as radiological protection, is the science of protecting people and the environment from the harmful effects of ionizing radiation, which includes both particle radiation and high energy electromagnetic radiation.

Radioactive contamination:

The deposition of unwanted radioactive material on the surfaces of structures, areas, objects, or people. It can be airborne, external, or internal.

Radioactive decay:

The spontaneous disintegration of the nucleus of an atom.

DRDC-RDDC-2020-D130 43 Radioactive half-life:

The time required for a quantity of a radioisotope to decay by half. For example, because the half-life of iodine-131 (I-131) is 8 days, a sample of I-131 that has 10 mCi of activity on January 1, will have 5 mCi of activity 8 days later, on January 9. This is in contrast to a biological half-life, where a combination of decay and natural decorporation will cause less activity to remain in the human body compared to what would be expected given the normal radioactive decay of the substance.

Radioactive material:

Material that contains unstable (radioactive) atoms that give off radiation as they decay.

Radioactivity:

The process of spontaneous transformation of the nucleus,generally with the emission of alpha or beta particles often accompanied by gamma rays.This process is referred to as decay or disintegration of an atom.

Radioassay:

A test to determine the amounts of radioactive materials through the detection of ionizing radiation. Radioassays will detect transuranic nuclides, uranium, fission and activation products, naturally occurring radioactive material, and medical isotopes.

Radiogenic:

Health effects caused by exposure to ionizing radiation.

Radiography:

1) Medical: the use of radiant energy (such as x-rays and gamma rays) to image body systems; and, 2) Industrial: the use of radioactive sources to photograph internal structures, such as turbine blades in jet engines. A sealed radiation source, usually iridium-192 (Ir-192) or cobalt-60 (Co-60), beams gamma rays at the object to be checked. Gamma rays passing through flaws in the metal or incomplete welds strike special photographic film (radiographic film) on the opposite side.

Radioisotope(radioactive isotope):

Isotopes of an element that have an unstable nucleus. Radioactive isotopes are commonly used in science, industry, and medicine.The nucleus eventually reaches a stable number of protons and neutrons through one or more radioactive decays. Approxi- mately 3,700 natural and artificial radioisotopes have been identified.

44 DRDC-RDDC-2020-D130 Radiological or radiologic:

Related to radioactive materials or radiation. The radiological sciences focus on the measurement and effects of radiation.

Radioluminescence:

The luminescence produced by particles emitted during radioactive decay.

Radiological dispersal device (RDD)

a device that disperses radioactive material by conventional explosive or other mechanical means, such as a spray.

Radiological exposure device (RED):

Also called a “hidden sealed source.” An RED is a terrorist device intended to expose people to significant doses of ionizing radiation without their knowledge. Constructed from partially or fully unshielded radioactive material, an RED could be hidden from sight in a public place (e.g., under a subway seat, in a food court, or in a busy hallway), exposing those who sit or pass close by. If the seal around the source were broken and the radioactive contents released from the container, the device could become a radiological dispersal device (RDD), capable of causing radiological contamination.

Radionuclide:

An unstable and therefore radioactive form of a nuclide.

Rem (roentgen equivalent, man):

A unit of equivalent dose. Not all radiation has the same biological effect, even for the same amount of absorbed dose. Rem relates the absorbed dose in human tissue to the effective biological damage of the radiation. It is determined by multiplying the number of rads by the quality factor, a number reflecting the potential damage caused by the particular type of radiation. The rem is the traditional unit of equivalent dose, but has been commonly replaced by the sievert (Sv), which is equal to 100 rem.

Roentgen (R):

A unit of exposure to x-rays or gamma rays. One roentgen is the amount of gamma or x-rays needed to produce ions carrying 1 electrostatic unit of electrical charge in 1 cubic centimetre of dry air under standard conditions. The roentgen has the disadvantage that it is only a measure of air ionization, and not a direct measure of radiation absorption in other materials, such as different forms of human tissue. For instance, one roentgen deposits 0.00877 grays (0.877 rads) of absorbed dose in dry air, or 0.0096 Gy (0.96 rad) in soft tissue. One roentgen of x-rays may deposit anywhere from 0.01 to 0.04 Gy (1.0 to 4.0 rad) in bone depending on the beam energy.

DRDC-RDDC-2020-D130 45 Sealed source:

A radioactive source, sealed in an impervious container that has sufficient mechanical strength to prevent contact with and dispersion of the radioactive material under the conditions of use and wear for which it was designed. Generally used for radiography or radiation therapy. May be classified “Special Form” on shipping papers and packages.

Sensitivity:

The ability of an analytical method to detect small concentrations of radioactive material.

Shielding:

The material between a radiation source and a potentially exposed person or object that reduces that exposure.

Sievert (Sv):

1 Sv = 1 Joule per kilogram. Used to measure the health effects of ionizing radiation (usually low doses), both external and internal. Sievert is the special name for the Standard International (SI) unit of dose equivalent (H), equivalent dose (HT), effective dose (E), weighted dose, and organ dose equivalent. Sievert is calculated as follows: Gray multiplied by the “radiation weighting factor” (also known as the “quality factor”) associated with a specific type of radiation.

SI units:

The Système Internationale (or International System) of units and measurements. This system of units officially came into being in October 1960 and has been adopted by nearly all countries, although the amount of actual usage varies considerably, especially in the U.S.

Somatic effects:

Effects of radiation that are limited to the exposed person, as distinguished from genetic effects, which may also affect subsequent generations.

Source term:

Types and amounts of radioactive or hazardous material released to the environment following an accident.

Special Nuclear Material (SNM):

Plutonium and uranium enriched in the isotope uranium-233 or uranium 235.

46 DRDC-RDDC-2020-D130 Specific activity:

Unit pertaining to the disintegrations per gram of a radioisotope.

Stable nucleus:

The nucleus of an atom in which the forces among its particles are balanced.

Stochastic effect:

An effect that occurs on a random basis independent of the size of dose. Theeffect typically has no threshold and is based on probabilities, with the chances of seeing the effect increasing with dose. If it occurs, the severity of a stochastic effect is independent of the dose received. Cancer is a stochastic effect.

Thermonuclear device:

A “hydrogen bomb.” A device with explosive energy that comes from fusion of small nuclei, as well as fission.

Terrestrial radiation:

Radiation emitted by naturally occurring radioactive materials, such as uranium (U), thorium (Th), and radon (Rn) in the earth.

Transuranic:

Pertaining to elements with atomic numbers higher than uranium (92). For example, plutonium (Pu) and americium (Am) are transuranics.

Weighting factor:

A multiplier that is used for converting the equivalent dose to a specific organ or tissue into what is called the “effective dose.” The goal of this process was to develop a method for expressing the dose to a portion of the body in terms of an equivalent dose to the whole body that would carry with it an equivalent risk in terms of the associated fatal cancer probability. It applies only to the stochastic effects of radiation.

Whole-body count:

The measure and analysis of the radiation being emitted from a person’s entire body, detected by a counter external to the body.

Whole-body exposure:

An exposure of the body to radiation, in which the entire body, rather than an isolated part, is irradiated by an external source.

DRDC-RDDC-2020-D130 47 X-ray:

Electromagnetic radiation caused by deflection of electrons from their original paths, or inner orbital electrons that change their orbital levels around the atomic nucleus. x- rays, like gamma rays can travel long distances through air and most other materials. Like gamma rays, x-rays require more shielding to reduce their intensity than do beta or alpha particles. X-rays and gamma rays differ primarily in their origin: x-rays originate in the electron shell; gamma rays originate in the nucleus.

48 DRDC-RDDC-2020-D130 DOCUMENT CONTROL DATA *Security markings for the title, authors, abstract and keywords must be entered when the document is sensitive 1. ORIGINATOR (Name and address of the organization preparing the 2a. SECURITY MARKING (Overall security marking of document. A DRDC Centre sponsoring a contractor’s report, or a the document, including supplemental markings if tasking agency, is entered in Section 8.) applicable.) DRDC – Suffield Research Centre CAN UNCLASSIFIED Box 4000, Station Main, Medicine Hat

AB T1A 8K6, Canada 2b. CONTROLLED GOODS NON-CONTROLLED GOODS DMC A

3. TITLE (The document title and sub-title as indicated on the title page.) Radiation Response Course: Pre-Instructional Package

4. AUTHORS (Last name, followed by initials – ranks, titles, etc. not to be used. Use semi-colon as delimiter) Munsie, T. J. S.

5. DATE OF PUBLICATION (Month and year of publication of 6a. NO. OF PAGES (Total 6b. NO. OF REFS (Total document.) pages, including Annexes, cited in document.) excluding DCD, covering and verso pages.) December 2020 54 10

7. DOCUMENT CATEGORY (e.g., Scientific Report, Contract Report, Scientific Letter) Reference Document

8. SPONSORING CENTRE (The name and address of the department project or laboratory sponsoring the research and development.) DRDC – Suffield Research Centre Box 4000, Station Main, Medicine Hat AB T1A 8K6, Canada

9a. PROJECT OR GRANT NO. (If appropriate, the applicable 9b. CONTRACT NO. (If appropriate, the applicable contract research and development project or grant number under number under which the document was written.) which the document was written. Please specify whether project or grant.) 06cb

10a. DRDC DOCUMENT NUMBER 10b. OTHER DOCUMENT NO(s). (Any other numbers which may be assigned this document either by the originator or by the DRDC-RDDC-2020-D130 sponsor.)

11a. FUTURE DISTRIBUTION WITHIN CANADA (Approval for further dissemination of the document. Security classification must also be considered.) Public release

11b. FUTURE DISTRIBUTION OUTSIDE CANADA (Approval for further dissemination of the document. Security classification must also be considered.) None 12. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Use semi-colon as a delimiter.) Radiation Response Course; Pre-read Package; Radiation Safety; Training; Military Training; CBRN (Chemical Biological Radiological Nuclear); Gamma Radiation; Radiation; Radiation De- tection; Radiation Protection; Radiological; Radiological and Nuclear Detection; Radiological Dispersal Devices; Radiological Weapons Effects; Radiological/Nuclear Contaminated Environ- ments; Radiological/Nuclear Risk and Hazard Assessment

13. ABSTRACT/RÉSUMÉ (When available in the document, the French version of the abstract must be included here.)

This pre-instructional package is designed to cover the basic material required to be fluent in the language that will be used on the Radiation Response Course. It is expected that a significant amount of this material is review, and the contents will be confirmed at the beginning of the course. The appendices are reference material. It is expected that the candidate will be familiar with the terminology in the Glossary, the unit conversions in Annex A and a list of common medical radioisotopes in Annex B. The terminology in the Glossary is partially used in this pre- read package but will be used during the course itself and forms the core of “radiological jargon” or language specific to the radiological sciences. La présente trousse de préinstruction devrait fournir la matière de base nécessaire pour maîtriser le langage utilisé durant le cours sur les effets du rayonnement. Une part importante du cours devrait être une revue de la matière et on en confirmera le contenu au début du cours. Les annexes constituent la documentation de référence. On s’attend à ce que les candidats se familiarisent avec la terminologie à le glossaire, la conversion des unités à l’annexe A et la liste de radioisotopes médicaux d’usage courant à l’annexe B. La terminologie à le glossaire est déjà util- isée en partie dans la trousse de prélecture, mais elle servira également durant le cours. Cette terminologie représente l’essentiel du « jargon technique » utilisé en radiologie et constitue le technolecte des sciences radiologiques.