Analytical X-ray Diffraction Safety Training

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Analytical X-ray Diffraction Safety Training
Slides stolen from John PickeringSJSU Radiation
safety Officer
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What is the purpose of safety training?
To increase your knowledge to enable you to
perform your job safely by adhering to proper
radiation protection practices while working with
or around x-ray generating devices.
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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.

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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.

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Fundamental Radiation Physics

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

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Four principal kinds of ionizing radiation
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General 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.
• They do Chemistry

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Background Radiation Natural sources of
radiation contribute to the annual radiation
dose (mrem/yr).
Cosmic - 28 mrem
Radon - 200 mrem
Diet - 40 mrem
Terrestrial - 28 mrem
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Man-made Radiation Man-made sources of radiation
contribute to the annual radiation dose
(mrem/yr).
Cigarette smoking - 1300
Medical - 53
Fallout lt 1
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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

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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.

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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).

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Photon Energy and Total Power
As the voltage increases the penetration
increases As the Current increases the dose rate
increases
The total power P V x I
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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.

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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
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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 1 R/minute

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X-ray Safety for Operators

• Decrease dose to the operator
• Time
• Determines total dose
• Voltage
• Determines penetration
• Current
• Determines dose rate

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

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Ionizing Radiation

• Produces damage through ionization and excitation

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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
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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 studiesbut not human

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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

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

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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.

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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

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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 accelerator. 40 rad/s inside victims
  shoes, 1300 rad/s to hands.

• 3 days after exposure
• Note erythema and swelling
• 1 month after
• Note blistering and erythema
• 2 months after

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ALARA

• As Low As Reasonably Achievable

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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.

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Dose Examples
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Engineering Controls

• Interlocks never bypass interlocks or
• other safety devices
• Warning Lights know the beam status
• whenever working with XRD
• Shielding
• Locked doors

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Problems with equipment

• If there are any questions or concerns about
  the functioning of an XRD unit, it must be taken
  out of service immediately and reported to the
  unit supervisor.
• Be aware that shutter mechanisms can
• fail. Warning lights can fail.

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General Methods of Protection

• Time

• Distance

• Shielding

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Verify you have viewed this powerpoint

• Send an email to hbarrett_at_bama.ua.edu stating
  that you have viewed the Annual Training for
  Persons using X-Ray Producing Machines
  presentation. Include your CWID, your
  sublicensee name, the building and room number
  where you work with radioactive materials.