Slide 1

Analytical X-ray Diffraction Safety Training

Part I

Slides developed by John Pickering

SJSU Radiation Safety Officer (RSO)(Retired)

Slide 2

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.

What is the purpose of radiation safety training?

Slide 3

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

Slide 4

Radiation is energy in transitin 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.

Slide 5

Slide 6

Ionizing radiationIonizing 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.

Slide 7

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 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.

Slide 8

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.

Slide 9

Radiological Fundamentals

Electron

Nucleus

Nucleus

Protons Neutrons

The basic unit of matter is the atom.

Slide 10

Slide 11

X-RAY AND GAMMA ( ) RAY PROPERTIES

Charge: None

Mass: None

Velocity: 3 x 108 m/s

Origin:

Rays: Nucleus

X Rays: Electron Cloud & Bremsstrahlung

Slide 12

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.

Slide 13

Ionizing Radiation

Slide 14

Four principal kinds of ionizing radiation

Kind 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 None Passes through

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

Slide 15

Background Radiation

Radon - 200 mrem

Cosmic - 28 mrem

Diet - 40 mrem

Terrestrial - 28 mrem

Slide 16

Man-made Radiation

Man-made sources of radiation contribute tothe annual radiation dose (mrem/yr).

Fallout < 1

Round trip US by air5 mrem per trip

Medical - 53Cigarette smoking - 1300

Building materials - 3.6Gas range - 0.2Smoke detectors - 0.0001

Slide 17

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

Slide 18

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

Slide 19

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 • 50 rem/year• 15 rem/year• 0.5 rem/year• 0.5 rem/gestation period• 0.1 rem/year

Slide 20

ALARA Program

• As Low As Reasonably Achievable– Responsibility of all

employees

• Exposures shall be maintained ALARA– Below regulatory limits

– No exposure without commensurate benefit

Slide 21

Responsibilities for ALARAManagement

Safety Organization

Radiation Worker

Ultimately YOU are!

•To establish a program•Meet regulatory limits

•Implementing a program•Run the daily operation

•To follow program

Slide 22

General Methods of Protection

• Time

• Distance

• Shielding

Slide 23

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).

Slide 24

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.

Slide 25

How X-rays are Produced

X-ray Tube

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

Slide 26

What are X-rays

• Electromagnetic radiation

• Originate in energy shells of atom

• Produced when electrons interact with a target

targetelectron

X-ray

Slide 27

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.

Slide 28

Slide 29

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.

Slide 30

Bremsstrahlung Radiation

Bremsstrahlung production = Z2

A

Slide 31

Photon Energy and Total Power

Voltage(Penetration)

(Current)

As the voltage increases the penetration increases

Energy

Dose

As the Current increases the dose rate increases

The total powerW = V x A

Slide 32

Photon Energy and Total Power

Energy

Dose

Characteristic X-ray

Gamma Peak(Specific Energy)

Slide 33

Photon Energy and Total Power

Energy

Dose

Average Energy = 1/3 Maximum Energy

Slide 34

Photon Energy and Total Power

Voltage(Penetration)

Current

Adding Filtration Filtration can shift the averageEnergy (voltage) higher

Slide 35

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

Slide 36

Emission

Radiation Emission

Slide 37

Absorption

Absorption

Slide 38

Reflection

Reflection

Slide 39

Skyshine

Skyshine

Slide 40

X-ray Safety for Operators

• Decrease dose to the operator

• Time– Determines total dose

• Voltage– Determines penetration

• Current– Determines dose rate

Slide 41

Ionizing Radiation

Produces damage through ionization and excitation

Slide 42

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.

Slide 43

Medial X-ray Shielding

Slide 46

Bioeffects

Slide 47

Slide 48

At HIGH Doses, We KNOW At HIGH Doses, We KNOW Radiation Causes Harm 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.

Slide 49

Law of Bergonie and Tribondeau

• The more rapidly reproducing cells are more radiosensitive.

• The least functionally differentiated cells are more radiosensitive.

1903

Slide 50

Dividing Cells are the Most Dividing Cells are the Most RadiosensitiveRadiosensitive

• Rapidly dividing cells are more susceptible to

radiation damage.

• Examples of radiosensitive cells are

– Blood forming cells

– The intestinal lining

– Hair follicles

– A fetus

This is why the fetus has an exposure limit (over gestation period) of 500 mrem (or 1/10th of the annual adult limit)

Slide 51

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.

Slide 52

Relative Radiosensitivity ofMammalian Tissues

Sensitive– Spermatogonia– Lymphocytes Hematopoietic

Tissues

Less sensitive– Epithelium– Epidermus

Resistant– Central nervous system– Muscle– Bone

Slide 53

Cell Cycle

Slide 54

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

Delayed

Diagnostic X-rayExposure

Slide 55

Direct versus Indirect Effects

Direct Effects:

Damage to DNA through ionization and excitation

Indirect Effects:

Decomposition of water in the cell.Interaction of directly altered moleculeswith other molecules

Slide 56

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.

Slide 57

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

Slide 58

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

ACUTE

CHRONIC

Slide 59

Chronic Exposure

Dose delivered in smallincrements over a long time

Effects appear slowly(many years)

Relatively low incremental doses required

Slide 60

Genetic Effects

• Somatic– 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

Slide 61

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

Slide 62

Measurement of Severity

• Prodromal Effects– Time of onset– Degree of symptoms– Duration of symptoms

• Hematological Changes– Lymphocyte counts

• Physical Dosimetry– Attendant readable

Slide 63

Factors that determine biological effect

• Dose rate

• Total dose received

• Energy of the radiation

• Area of the body exposed

• Individual sensitivity

• Cell sensitivity

Slide 64

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

Slide 65

Skin Effects

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

Erythema is a reddening of the skin caused by the expansion of small blood vessels in the outer layers of the skin.

Slide 66

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.

Slide 67

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

Slide 68

Slide 69

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

Slide 70

ALARAALARA

As Low As Reasonably Achievable