X-ray Safety Schad.ppt

Center For Materials For Information TechnologyAn NSF Materials Research Science and Engineering

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The University of Alabama

Analytical X-ray Diffraction Safety Training

Slides stolen from John Pickering

SJSU Radiation safety Officer


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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.

What is the purpose of safety training?


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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 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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• 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.

Radiation Units


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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

Kind Atomic

Mass

Electrical Charge

Range in Air

Range in Body Tissue

Attenuation Exposure Hazard

Alpha 4 +2 < inch Unable to penetrate skin

Stopped by a sheet of paper or skin

Internal

Beta 1/1840 -1 Several feet 1/3 inch Stopped by a thin sheet of aluminum

Skin, eyes, and internal

Gamma / x-ray

NA 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


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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).

Radon - 200 mremCosmic - 28 mrem

Diet - 40 mrem

Terrestrial - 28 mrem


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Man-made RadiationMan-made sources of radiation contribute to

the 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


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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

The total powerP = V x I

As the voltage increases the penetration increasesAs the Current increases the dose rate increases


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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

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.


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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.

ACUTE

CHRONIC


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At HIGH Doses, We KNOW Radiation At HIGH Doses, We KNOW Radiation Causes HarmCauses 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

Delayed

Diagnostic X-rayExposure


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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 RadiosensitiveDividing 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 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


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ALARAALARA

As Low As Reasonably Achievable


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Dose Examples 1000 mrem SRS ANNUAL DOSE CONTROL LEVEL FOR RADIATION WORKERS - 800 mrem

AVERAGE DIAGNOSTIC NUCLEAR MEDICINE PROCEDURE - 430 mrem AVERAGE U.S. NON-OCCUPATIONAL RADIATION DOSE PER YEAR - 334 mrem AVERAGE ANNUAL DOSE FROM RADON IN THE HOME - 200 mrem AVERAGE ANNUAL DOSE TO A MEMBER OF AN AIRLINE FLIGHT CREW - 160 mrem

100 mrem AVERAGE U.S. NON-OCCUPATIONAL DOSE FOR I MONTH - 28 mrem ADDITIONAL ANNUAL BACKGROUND DOSE FROM LIVING IN A MASONRY HOME - 13 mrem

10 mrem CHEST X-RAY - 8 mrem AVERAGE U.S. BACKGROUND DOSE PER WEEK - 6 mrem ROUNDTRIP ATLANTA TO LOS ANGELES AIRLINE FLIGHT - 4 mrem

1 mrem ADDITIONAL DOSE FROM A ONE DAY VISIT IN DENVER - 1 mrem ROUNDTRIP ATLANTA TO NEW YORK AIRLINE FLIGHT - 0.4 mrem

0.1 mrem DOSE FROM SPENDING 1 HOUR IN GRAND CENTRAL STATION - 0.05 mrem ADDITIONAL DOSE FOR EACH HOUR SPENT IN DENVER - 0.05 mrem DOSE FROM SPENDING 1 HOUR AT THE STATUE OF LIBERTY - 0.04 mrem

0.01 mrem AVERAGE DOSE FROM A SMOKE DETECTOR IN THE HOME - 0.01 mrem DOSE FROM K-40 IN 1 BANANA - 0.007 mrem

Dose around our XRD machines in room 284: 0.015 mrem/hr


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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 [email protected] 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.

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X-ray Safety Schad.ppt