Analytical X-ray Diffraction Safety Training Part I Slides developed by John Pickering SJSU Radiation Safety Officer (RSO) (Retired)

What is the purpose of radiation safety training? To help you gain enough knowledge to enable you to perform your job safely. To ensure that you adhere to proper radiation protection practices while working with or around x-ray generating devices.

Fundamental Radiation Physics Radiation – alpha particles, beta particles, gamma rays, X-rays Radioactivity – spontaneous nuclear transformations Generally alpha particles and beta particles Often accompanied by gamma ray emission Ionizing Radiation – radiation capable of producing charged particles (ions) in the material through which it passes

Radiation is energy in transit in the form of high speed particles and electromagnetic waves. We encounter electromagnetic waves every day. They make up our visible light, radio and television waves, ultra violet (UV), and microwaves with a spectrum of energies. These examples of electromagnetic waves do not cause ionization of atoms because they do not carry enough energy to remove electrons from atoms.

Ionizing radiation Ionizing radiation is radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from their orbits, causing the atom to become charged or ionized. Ionizing radiation deposits energy at the molecular level, causing chemical changes which lead to biological changes. These include cell death, cell transformation, and damage which cells cannot repair. Effects are not due to heating.

Radiation Units Roentgen (R) The roentgen (R) is a unit of radiation exposure in air. It is defined as the amount of x-ray or g radiation that will generate 2.58E-4 coulombs/kg of air at standard temp and pressure. rad RAD stands for Radiation Absorbed Dose and is the amount of radiation that will deposit 0.01 J/kg of material. A roentgen in air can be approximated by 0.87 rad in air, 0.93 rad in tissue, and 0.97 rad in bone. Dose The SI unit of absorbed dose is the gray (Gy), which has the units of J/kg. 1 Gy= 100 rad.

Radiation Units REM REM stands for Roentgen Equivalent Man. The REM is a unit of absorbed dose and is equal to the rad multiplied by a weighting factor which varies according to the type of radiation. The weighting factor for x-rays is equal to 1. For x-rays, one rem is equal to one rad. The SI unit used in place of the rem is the sievert (Sv). 1 Sv = 100 rem.

Radiological Fundamentals The basic unit of matter is the atom. Nucleus Electron The basic unit of matter is the atom. The central portion of the atom is the nucleus. Electrons orbit the nucleus. The nucleus consists of protons and neutrons. Nucleus Protons Neutrons

X-RAY AND GAMMA ( ) RAY PROPERTIES Charge: None Mass: None Velocity: 3 x 108 m/s Origin: Rays: Nucleus X Rays: Electron Cloud & Bremsstrahlung

What are x-rays? X-rays are photons (electromagnetic radiation) which originate in the energy shells of an atom, as opposed to gamma rays, which are produced in the nucleus of an atom.

Ionizing Radiation

Four principal kinds of ionizing radiation Atomic Mass Electrical Charge Range in Air Range in Body Tissue Attenuation Exposure Hazard Alpha (He nuclei) 4 +2 < inch Unable to penetrate skin Stopped by a sheet of paper or skin Internal Beta (electrons or positrons) 1/1840 -1 Several feet 1/3 inch Stopped by a thin sheet of aluminum Skin, eyes, and internal Gamma / x-ray (photons) None Passes through Thick lead or steel External and internal Neutron 1 Neutral Hundreds of feet About 10% goes through Several feet of water or plastic Primarily external

Background Radiation Cosmic - 28 mrem Radon - 200 mrem Diet - 40 mrem Terrestrial - 28 mrem

Man-made Radiation Man-made sources of radiation contribute to the annual radiation dose (mrem/yr). Cigarette smoking - 1300 Medical - 53 Round trip US by air 5 mrem per trip Building materials - 3.6 Gas range - 0.2 Smoke detectors - 0.0001 Fallout < 1

Radiation Sources X-ray diffraction is a source of very intense radiation. The primary beam can deliver as much as 400,000 R/minute Collimated and filtered beams can produce about 5,000 to 50,000 R/minute Diffracted beams can be as high as 80 R/hour

Dose Limits EPA Guidance for dose limits NRC Regulations for dose limits DOE Regulations for dose limits DOT Regulations for transport State Agreement States NCRP National Scientific Body Licensee Institutional Admin Limits

Regulatory Limits Radiation Worker Whole Body Extremities Skin and other organs Lens of the eye Non-Radiation Worker Embryo/fetus Visitors and Public 5 rem/year - 3 rem/quarter 50 rem/year 15 rem/year 0.5 rem/year 0.5 rem/gestation period 0.1 rem/year

ALARA Program As Low As Reasonably Achievable Responsibility of all employees Exposures shall be maintained ALARA Below regulatory limits No exposure without commensurate benefit

Responsibilities for ALARA Ultimately YOU are! Responsibilities for ALARA To establish a program Meet regulatory limits Management Safety Organization Implementing a program Run the daily operation Radiation Worker To follow program

General Methods of Protection Time Distance Time Minimize the time around the x-ray source. Less time equals less exposure. Distance Increase the distance. Radiation reduces by 1/(distance)2 Shielding Put appropriate material between you and the source. Shielding

What are x-rays? X-rays are produced when accelerated electrons interact with a target, usually a metal absorber, or with a crystalline structure. This method of x-ray production is known as bremsstrahlung. The bremsstrahlung produced is proportional to the square of the energy of the accelerated electrons used to produce it, and is also proportional to the atomic number (Z) of the target (absorber).

What are x-rays? Many different types of machines produce x-rays, either intentionally or inadvertently. Some devices that can produce x-rays are x-ray diffractometers, electron microscopes, and x-ray photoelectron spectrometers. X-rays can also be produced by the attenuation of beta particles emitted from radionuclides.

How X-rays are Produced When fast-moving electrons slam into a metal object, x-rays are produced. The kinetic energy of the electron is transformed into electromagnetic energy. X-ray Tube

What are X-rays Electromagnetic radiation Originate in energy shells of atom Produced when electrons interact with a target target X-rays are photons (electromagnetic radiation) which originate in the energy shells of an atom, as opposed to gamma rays, which are produced in the nucleus of an atom. X-rays are produced when accelerated electrons interact with a target, usually a metal absorber, or with a crystalline structure. This method of x-ray production is known as bremsstrahlung. The bremsstrahlung produced is proportional to the square of the energy of the accelerated electrons used to produce it, and is also proportional to the atomic number (Z) of the target (absorber). Many different types of machines produce x-rays, either intentionally or inadvertently. Some devices that can produce x-rays are x-ray diffractometers, electron microscopes, x-ray photoelectron spectrometers, and Van de Graaf accelerators. X-rays can also be produced by the attentuation of beta particles emitted from radionuclides. electron X-ray

Characteristic X-rays Characteristic x-rays are produced by transitions of orbital electrons from outer to inner shells. Since the electron binding energy for every element is different, the characteristic x-rays produced in the various elements are also different. This type of x-radiation is called characteristic radiation because it is characteristic of the target element. The effective energy characteristic x-rays increases with increasing atomic number of the target element.

Bremsstrahlung Radiation A projectile electron that completely avoids the orbital electrons on passing through an atom of the target may come sufficiently close to the nucleus of the atom to come under its influence. Since the electron is negatively charged and the nucleus is positively charged, there is an electrostatic force of attraction between them. As the projectile electron approaches the nucleus, it is influenced by a nuclear force much stronger than the electrostatic attraction. As it passes by the nucleus, it is slowed down and deviated in its course, leaving with reduced kinetic energy in a different direction. This loss in kinetic energy reappears as an x-ray photon.

Bremsstrahlung Radiation Z2 A Bremsstrahlung production =

Photon Energy and Total Power As the voltage increases the penetration increases As the Current increases the dose rate increases Dose (Current) Energy Voltage (Penetration) The total power W = V x A

Photon Energy and Total Power Characteristic X-ray Gamma Peak (Specific Energy) Dose Energy

Photon Energy and Total Power Average Energy = 1/3 Maximum Energy Dose Energy

Photon Energy and Total Power Adding Filtration Filtration can shift the average Energy (voltage) higher Current Voltage (Penetration)

Interaction with Matter When x-rays pass through any material some will be transmitted some will be absorbed some will scatter The proportions depend on the photon energy and type of material

Emission Radiation Emission

Absorption Absorption

Reflection Reflection

Skyshine Skyshine

X-ray Safety for Operators Decrease dose to the operator Time Determines total dose Voltage Determines penetration Current Determines dose rate

Produces damage through ionization and excitation Ionizing Radiation Produces damage through ionization and excitation

X-ray Safety Filtration removes low-energy x-rays from the primary beam. Collimation limits the beam to a useful area. Compliance testing performed periodically. Registration of sources with regulatory agency.

Medial X-ray Shielding

Open Beam XRD Example of an unenclosed (open) x-ray diffractometer (Geology Department). The open x-ray beam of such an instrument can be extremely hazardous, and it is far preferable to enclose the entire x-ray apparatus.

XRD (tin/polycarbonate enclosure) Properly enclosed and interlocked x-ray diffractometer. The enclosure is made of tin-impregnated polycarbonate. Leaded glass enclosures are also used. If a panel is opened while the XRD is being used, the interlock should either shut off the x-ray or close the shutter, preventing accidental exposure to personnel.

Bioeffects

At HIGH Doses, We KNOW Radiation Causes Harm High Dose effects seen in: Radium dial painters Early radiologists Atomic bomb survivors Populations near Chernobyl Medical treatments Criticality Accidents In addition to radiation sickness, increased cancer rates were also evident from high level exposures. Narrative The Picture of woman using fluoroscope. Just off the picture to the right is the business end on an X-ray machine beaming toward her face. The beam hits the phosphors on the back of the “telescope” and she can she her hand as an X-ray and watch it move…. She also gets a whopping dose to the face! Throughout this century, people have been exposed to radiation. Some through accident or ignorance; others, like the atomic bomb survivors or medical patients, where exposed intentionally. Extensive data has been collected on these exposures in an attempt to understand more about it’s effects. At high doses of radiation, we know there are physical effects such as burns, radiation sickness and even death. Another observed effect of high doses of radiation is a detectable increase in certain cancer rates. Not a sure thing, but rather a slight increase over the natural incidence of cancer for large exposures.

Law of Bergonie and Tribondeau The more rapidly reproducing cells are more radiosensitive. The least functionally differentiated cells are more radiosensitive. 1903

Dividing Cells are the Most Radiosensitive Rapidly dividing cells are more susceptible to radiation damage. Examples of radiosensitive cells are Blood forming cells The intestinal lining Hair follicles A fetus Suggested narrative: When cells are dividing (or undergoing mitosis) they are more susceptible to radiation damage because the cells don’t have their full suite of repair mechanisms. Because of this, cells that are often dividing like The cells that create our blood or line our intestine, also Hair follicles, and, of course, fetal cells are more susceptible to radiation damage. This is why the fetus has a exposure limit (over gestation period) of 500 mrem (or 1/10th of the annual adult limit) Specialized or slowly dividing cells, like brain cells are radio-insensitive. Credit: The vedio (and voiceover) was Excerpted from DOE’s Transportation Emergency Preparedness Program (TEPP) http://www.em.doe.gov/otem/program.html This is why the fetus has an exposure limit (over gestation period) of 500 mrem (or 1/10th of the annual adult limit)

Biological Effects of Radiation are dependent upon: Total energy deposited Distribution of deposited energy Low dose, low-dose rate radiation exposure. The effects are in great dispute. It is thought that the effects of a protracted dose of radiation are not as great as with an acute dose because of biological repair mechanisms.

Relative Radiosensitivity of Mammalian Tissues Sensitive Spermatogonia Lymphocytes Hematopoietic Tissues Less sensitive Epithelium Epidermus Resistant Central nervous system Muscle Bone

Cell Cycle

Prompt – effects that appear quickly Bioeffects Somatic (body) effects of whole body irradiation can be divided into "prompt" effects and "delayed" effects. Prompt – effects that appear quickly Delayed – effects that may take years to appear Prompt Diagnostic X-ray Exposure Delayed

Direct versus Indirect Effects Damage to DNA through ionization and excitation Indirect Effects: Decomposition of water in the cell. Interaction of directly altered molecules with other molecules

Bioeffects Three levels of effects that can occur days to weeks after a large, whole body exposure to radiation: Hematopoietic syndrome (~ 100-1000 rem): effects on blood-forming organs; infection, anemia Gastrointestinal syndrome (~1000-5000 rem): destruction of cells lining the intestines; diarrhea, electrolyte imbalance Central Nervous System syndrome (5000- rem and higher): damage of central nervous system function; muscle coordination loss, seizures, coma It is important to note that whole body radiation exposures of magnitudes shown above are extremely rare and not associated with x-ray diffraction.

Radiation Syndromes Three syndromes from acute doses Hematopoietic Blood system Gastronitestinal Instestinal tract Central nervous system Progression through the syndromes Prodromal (initial) First set of symptoms Latent Asymptomatic period Period of illness Characteristics of prodromal stage reoccur along with additional symptoms Recovery or death

Biological effects depends on whether it is an ACUTE DOSE or a CHRONIC DOSE.

Chronic Exposure Dose delivered in small increments over a long time Effects appear slowly (many years) Relatively low incremental doses required

Genetic Effects Somatic Heritable Damage to genetic material in the cell May cause cell to become a cancer cell Probability is very low at occupational doses Heritable Passed on to offspring Observed in some animal studies but not in humans

Prenatal Radiation Exposure Sensitivity of the unborn Rapidly dividing cells are radiosensitive Potential effects Low birth weight - (most common) Mental retardation Chance of childhood cancer

Measurement of Severity Prodromal Effects Time of onset Degree of symptoms Duration of symptoms Hematological Changes Lymphocyte counts Physical Dosimetry Attendant readable

Factors that determine biological effect Dose rate Total dose received Energy of the radiation Area of the body exposed Individual sensitivity Cell sensitivity

Exposure Effects 1000 rad - second degree burns 2000 rad - intense swelling within a few hours 3000 rad - completely destroys tissue 4000 rad acute whole body exposure is LD 50/30 LD 50/30 - lethal to 50% of population within 30 days if not treated

Skin Effects Erythema is a reddening of the skin caused by the expansion of small blood vessels in the outer layers of the skin. Exposure (R) Time Period Effects < 300 R Somatic effects generally not observed 300 – 800 R 24 – 48 hours 8 – 14 days 1 month Temporary hair loss Erythema Maximum erythema pain Recurrence of erythema (last 2-3 weeks) > 1500 R Long term Scar tissue, radiation dermatitis

Bioeffects- X-rays and Skin Most radiation overexposures from analytical x-ray equipment are to the extremities. For x-rays of about 5-30 keV, irradiation of the fingers or hands does not result in significant damage to blood-forming tissue. At high exposures some general somatic effects to the skin can occur. Very high exposures may necessitate skin grafting or amputation of the affected extremity. Biological effects can be observed at 10 rem in special blood studies. Typically effects are visually observed at 50 to 100 rem.

X-Ray Burns vs. Thermal Burns Most nerve endings are near the surface of the skin High energy x-rays penetrate the outer layer of the skin that contains most of the nerve endings so one does not feel an X-Ray burn until the damage has been done X-rays penetrate to the deeper, basal skin layer, damaging or killing the rapidly dividing germinal cells, that are destined to replace the outer layers

Accident Case Study Case Study - A radiation accident at an industrial accelerator facility from: Health Physics, Vol. 65, No. 2, August 1992, pp. 131-140. Reproduced by permission. 3MV potential drop accelerator. 40 rad/s inside victim’s shoes, 1300 rad/s to hands. 3 days after exposure Note erythema and swelling 1 month after Note blistering and erythema 2 months after

As Low As Reasonably Achievable ALARA As Low As Reasonably Achievable