What is Radiation - UML

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What is Radiation?

Radiation is energytransported in the form of particles or waves.

Penetration Abilities of Different Types of Radiation

Alpha ParticlesStopped by a sheet of paper

Beta ParticlesStopped by a layer of clothingor less than an inch of a substance (e.g. plastic)

Gamma RaysStopped by inches to feet of concreteor less than an inch of lead

RadiationSource

NeutronsStopped by a few feet of concrete

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Alpha Survey Meter

Detecting Radiation

Beta and Gamma Survey Meter

Radiation vs. Radioactive Material

• Radiation: energy transported in the form of particles or waves (alpha, beta, gamma, neutrons)

• Radioactive Material: material that contains atoms that emit radiation spontaneously

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Exposure vs. Contamination

Exposure: irradiation of the body absorbed dose (Gray, rad)

Contamination: radioactive material on patient (external)or within patient (internal)

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Basic Radiation Principles

Radiation is energy released from unstable elements. The energy is released until the element is stable.

This may take a fraction of a second or billions of years depending upon the element.

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Basic Radiation Principles…continued…

Decay (decrease in the radioactivity) can be determined using half-lives.

A “half-life” is the time it takes for an isotope to reduce its activity by one half…

Basic Radiation Principles …continued…

This means that if, an element has a half-life of five years:

1/2 of the radiation would be present in 5 years




1/32 of the radiation would b e present in 25 years

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U-238 has a 4.47 billion year half-life

Cesium-137 has a 30 year half-life

Cobalt-60 has a 5 year half-life

Iodine-131 has an 8 day half-life

Other sources of ionizing radiation may decay faster, causing less exposure.

Source: http://www.epa.gov/radiation/radionuclides/http://www.epa.gov/radiation/radionuclides/ accessed 12/23/2004


Radiation is everywhere, coming from:• the solar system• the atmosphere • the earth (soil, rocks, and water) and • man-made sources.

You cannot see, smell, or feel it.

http://www.epa.gov/radiation/radionuclides/

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Radiation: Overview

Biological injury Ionization of atoms within the cell

Ionization breaks molecular bonds

Cell damage occurs when critical cell structures are affected

Types of Ionizing Radiation

Alpha particles

Beta particles

Gamma rays

Neutron particles

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Alpha particlesRelatively large mass

Consists of two protons and two neutrons

Possesses +2 positive charge striping electrons from atoms it passes through

Alpha particle decay

U.S. Department of Energy Image

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Alpha particles Do not travel far Range in air is 1-2 inches

Completely stopped by the dead layers of the skin or by clothing

Offer minimal external hazard

Can cause significant regional cellular damage when internalized

The penetrating power of three types of radiation

U.S. Environmental Protection Agency Illustration

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Beta particlesElectrons emitted during decay

Found in fallout

Half the charge of alpha particles

Electrically interacts with passing atoms

Beta particle decay

U.S. Department of Energy Images

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Beta particles Travel further than alpha particles

Easily shielded by thin plastic, glass, aluminum or wood

External hazard to skin and eyes

Less dangerous internally but still can cause significant regional injury



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Gamma rays / X-raysElectromagnetic wave / no charge

Ionize matter by direct interaction with orbital electrons

Difference between radiation is only their source

Best shielded by dense materials

Gamma decay


Gamma decay


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Gamma rays Highly penetrating

Can produce whole body exposure

Equally dangerous with external or internal exposure



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Neutron particlesEmitted from unstable atoms during a nuclear

reaction

No electrical charge

Causes damage by direct collision with the nucleus of another atom

May produce indirect ionization


Neutron particles Highly penetrating; difficult to stop

Best shielded by materials with high hydrogen content

Cause whole body injury like gamma rays, but 20 times more damaging

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Radioactive Isotopes

Alpha emittersAmericium-241

Plutonium-239/238

Radium-226


Americium-241Decay daughter of plutonium

Main threat is heavy metal poisoning

Large quantities : cause whole-body irradiation

75% of the lung burden is absorbed

Absorbed rapidly from skin wounds

Urinary and hepatic excretion

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Plutonium-238/239Produced from uranium in reactorsPrimary fissionable material in nuclear plants and

weaponsAlways contaminated with americiumPrimary toxicity is from inhalationGI absorption depends on chemical stateMay be washed from intact skin


Radium-226Primary alpha emitter, but daughter products

emit beta and gamma rays

Most common exposure is ingestion

Follows calcium to bone deposition

Associated with leukemia, aplastic anemia, and sarcomas

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Beta emittersIodine-131, 132, 134, 135

Phosphorus-32

Strontium-90


Iodine-131, 132, 134, 135Created during nuclear fission

Found in reactor fuel rods or after a nuclear explosion

Primary toxicity is to the thyroid gland

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Thyroid Glands

National Institute of Diabetes and Digestive and Kidney Diseases Image


Phosphorus-32 Found in research labs and medical facilities

Completely absorbed from all sites

Deposited in the bone marrow and other rapidly replicating cells

Local irradiation causes cell damage

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Strontium-90 Direct fission product of uranium

Daughters emit beta and gamma rays

Readily absorbed via respiratory and GI routes

~ 50% of dose deposited in bone


Gamma emittersCesium-137

Cobalt-60

Uranium-238, 234,235

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Cesium-137By-product of the manufacture of weapons-

grade radioactive material

Half-life of 31 years

Salt that dissolves easily in water

Emits both gamma and beta radiation

Completely absorbed through the lungs, GI tract, and wounds


Cobalt-60Produced by non-radioactive cobalt to intense

radiation in the reactor core

Emits both gamma and beta radiation

Half-life of 5 years

Rapidly absorbed from the lung

< 5% absorption from the GI tract

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Uranium-238,235,234Natural mix of all three isotopes Half-lives of 4.5x109, 7x108, and 2.5x105

yearsInhaled compounds metabolized and excreted

in urineUrinary levels of 100 µg per deciliter may

cause renal failureAbsorption is determined by its chemical state

Units of Radiation

Rad still used widely International unit called gray (Gy) Quality factor used to adjust for

differences in tissue absorption

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• Alpha () particles can be blocked by a piece of paper.

• Beta () particles can be blocked by a firefighter’s turnout gear, but not a piece of paper.

• If exposed, wash off particles well with soap and water in a timely manner.

• Note: If particles are ingested, inhaled, or enter the body through wounds, medical attention is recommended.


Gamma rays () are a different matter.• Pure energy, similar to x-rays• Can be blocked by concrete, lead or steel• If exposed, medical attention is recommended.

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Nuclear Reaction: Decontamination

• Primary contaminants will be alpha and beta emitters

• Simply removing clothing and shoes will reduce contamination by approximately 90%

Remember 3 Factors to Minimize Exposure

• Time

• Distance

• Shielding

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Technical Emergency Response Training

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RADIOLOGICAL MATERIALS

TIME

• 100 mrem per hour x 15 min (.25 hour) = 25 mrem

SourceSource Dose25 mrem

Dose25 mrem

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DISTANCE

SourceSource

1 meter1 meter 1 meter1 meter

Dose RateDose Rate

100 mrem/hr100 mrem/hr 25 mrem/hr25 mrem/hr

SHIELDING

ALPHA PARTICLE

BETA PARTICLE

GAMMA RAYS

PA

PE

R

LE

AD

SK

IN

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Measurement and Health Effects of Radiation

Exposures

Measurement

The term used to measure radiation doses is “rem.”It measures the effect of radiation on living tissue, also known as a “biologically effective dose.”Typically, exposure is expressed in “millirems” (mrem) which is one-thousandth of a rem.

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Typical Radiation Doses

Flight from Los Angeles to London . . . . 5 mremAnnual public dose limit . . . . . . . . . . .100 mremAnnual natural background . . . . . . 300 mremFetal dose limit . . . . . . . . . . . . . . . . . 500 mremAnnual radiation worker dose limit . 5000 mrem

Emergency: The MDH accepts an emergency exposure for lifesaving only of 25 to 100 rem.

Note: Workplace exposures required to be “As Low As Reasonably Achievable” (ALARA)

Factors that Influence Health Effects of Radiation

• General health of the individual • Amount (The “threshold dose” means that the

effect is not seen until the absorbed dose is greater than a certain level.)

• Frequency (acute or somatic)• Strength of isotope• Targeted cells or organs receiving the dose

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Uses of Radioactive Material

Uses of radioactive material

Medical applications include:

• Nuclear medicine equipment

• Isotopic generators• Therapy units and seed

implants• Radiopharmaceuticals• Computed Tomography

(CT) imagingSource: FDA, Center for Devices and Radiological Healthhttp://www.pueblo.gsa.gov/cic_t ext/health/ fullbodyhttp://www.pueblo.gsa.gov/cic_t ext/health/ fullbody-ctscan/ fullbody-ctscan.htmAccessed 12/21/2004

http://www.pueblo.gsa.gov/cic_text/health/fullbody

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Business applications include:

• Luminous dials• Moisture and density gauges• Thickness gauges• Rifle sights• Static eliminators

Source: Nuclear Regulatory Commission http://www.nrc.gov/readinghttp://www.nrc.gov/reading-rm/doc-coll ections/news/2004/04-004i.htmlAccessed 12/21/2004


Public health applications include:

• Food irradiation• Radiography• Well logging• Chemical agent detectors • XRFs for lead paint analysis• Smoke detectors

http://www.foodprocessinghttp://www.foodprocessing-technology.com/projects/sure/accessed 12/21/2004

Source: FDA, Center for Devices and Radiological Health http://www.pueblo.gsa.gov/cic_t ext/healthttp://www.pueblo.gsa.gov/cic_t ext/health/ fullbody-ctscan/what.htm

accessed 12/21/2004

http://www.nrc.gov/reading

http://www.foodprocessing

http://www.pueblo.gsa.gov/cic_text/healt

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Potential Radiological Incident?

Accidental (Controlled by regulatory systems)• The transportation sector (vehicle, rail, ship) carries many

materials across the US. Despite fears of an attack, the most likely radiological incident remains a transportation accident involving radioactive materials.

• Nuclear power plants build strong structures and exercise

Intentional (Controlled by legal systems)• Stolen materials• Dirty bombs

Damage to a nuclear power plant is difficult to imagine

US plants: 3 barriers between radioactive materials and the environment. The reactor will not explode.

Structures that house reactor fuel are robust. Fuel is protected from impacts of large commercial aircraft.

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Damage to a nuclear power plant is difficult to imagine

…continued…Professionals discuss, plan, and perform “exercises” often to rehearse skills and test possible scenarios:• At worst, could be a release of radioactive

materials into the air, creating a “plume.”• May need to evacuate a surrounding area.• Precautionary medical measures may be

necessary for those caught in the plume or its expected path down-wind.

Bombs with radioactive material (“Dirty Bombs” or “RDDs”)

Definition: a conventional bomb surrounded by or filled with non-nuclear radiological materials. (also called a radiological dispersal device, or RDD)

Unlikely, and most probable, form of radiological terrorismRadioactivity would not kill or seriously injure people (but

an explosion might).Would create fear or chaos: coined a “Weapon of Mass

Disruption.”Expect significant long-term psychological effects.

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Bombs with radioactive material …Continued…

An RDD could be • any size,• spread radiation, and• contaminate an area.

This photo was staged, but several alleged real-life RDD plots have been upset.

Photo: www.seattle.gov/mayor/gallery_2003/gallery_TOPOFF2_03.htmwww.seattle.gov/mayor/gallery_2003/gallery_TOPOFF2_03.htmErik Stuhaug, photographer, accessed 11/10/2004

Summary

Alpha, beta, gamma, and neutron radiationAlpha particlesNo external risk Produce regional internal injury

Beta particles Significant external risk to skin & eyes

www.seattle.gov/mayor/gallery_2003/gallery_TOPOFF2_03.htm

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Summary

Gamma radiation and neutrons Highly penetrating Produce whole body exposure

Units of radiation Rad and rem Gray (Gy) and sievert (Sv)

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What is Radiation - UML