5 Radiation

7/30/2019 5 Radiation

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Radiation



Atom

The atom is made up of a nucleus composed of protons andneutrons, surrounded by a cloud of electrons.

The number of protons and electrons determine thechemical nature of the atom.

Z = Atomic number

N = Number of neutrons

A = Atomic mass = Z + N



Isotopes

Atoms of element with different number of neutrons

Protons = Atomic Number

Protons + Neutrons = Atomic Weight Example: Uranium-238

– 92 protons by definition

– 238-92 = 146 neutrons

Carbon-14

– 6 protons (by definition), 8 neutrons



Stable Vs Radioactive

The number of neutrons determines if the atom isstable or radioactive.

All isotopes of a particular element have the sameatomic number (number of protons) but differentatomic mass (number of neutrons).

Because all isotopes of an element have the sameatomic number, their chemical nature is identical.However, the radioactive nature of the isotopesvary.



Radioactive (unstable) isotopes

Radioactive (unstable) isotopes emitenergetic particles and/orelectromagnetic (EM) radiation in theform of photons.

All radioactive isotopes eventuallydecay to stable isotopes.

Stable isotopes can be maderadioactive by bombardment withenergetic protons in particle

accelerators or neutrons in nuclearreactors.



Radioactive Decay

Radioactive decay is a disintegration process by which aradioactive isotope emits energy in order to become a stableisotope.

Radioactive decay is random when observed for shortperiods.

By observing decay over longer periods of time a regularpattern emerges, we call the half-life .

The half-life is defined as the time required for half of the

atoms of a particular isotope to decay. The value of the half-life is specific to the isotope and may

vary from microseconds to thousands of years.



What is Radioactivity?

The “amount” of radioactivity (called activity) is givenby the number of nuclear decays that occur per unittime (decays per minute).

2/1

693.0

0

2/12/1

0

0

693.02ln

,

T

t

t

t

e A A

T T

e A A

e N N N dt

dN N is the number of radioactiveatom present at time t. N0 is

initial value

is decay constant

A is activity, A0

is initial value

T1/2 is half life



Radioactivity

Curie is the unit of radioactivity

1 Curie is 3.7 x 1010 decays/second

Rn-222 3.8 days .000006 grams

Co-60 5.26 yr .0013 grams

Sr-90 28 yr .007 grams Ra-222 1600 yr 1 gram

Pu-239 24400 yr 16 grams

U-238 4.5 b.y. 3,000,000 gm (3 tons)

2/1

693.0

0

T

t

e A A



Radioactive Decay: Half-Life

Decay Constant: fraction of atoms that

decay/time

Half-life = 0.693/Decay Constant

Shorter Half Life = More Radiation Per

Unit Time



Half-life of Radioisotopes

The half-life has been

determined for each isotope,

and can be used to perform

decay calculations.

As a rule, whenever an

isotope has undergone 10

half-lives, enough atoms will

have decayed to make theradiation field emitted

indistinguishable from the

“background" level.

Radioisotope Half-LifeCalcium - 45 (45Ca) 162.7 days

Carbon - 14 (14C) 5730 years

Chromium - 51 (51Cr)27.8 days

Hydrogen - 3 (3H) 12.35 years

Iodine - 125 (125I) 60.14 days

Iron - 59 (59Fe) 44.5 days

Manganese - 54 (54Mn)312.5 days

Phosphorus - 32 (32P) 14.29 days

Phosphorus - 33 (33P)25.3 days

Sodium - 22 (22Na) 2.6 years

Sulfur - 35 (

35

S) 87.39 days



Half-Life and Hazard

Very short half-life (days or less)

– Extremely high radiation hazard

– Decays very quickly

–

Probably won’t move far during lifetime Extremely long half-life (geological)

– Radiation hazard negligible

– Chemical toxicity is worst hazard

–Daughter products (radon) can be a problem

Medium half-lives (years to 1,000’s years)

– Last long enough to migrate



Units of Radiation Dose

Roentgen – Ability to create a specified electric charge

per volume of air

Rem (Roentgen equivalent man) –Biological effect of

one roentgen of X-rays Rad (Radiation absorbed dose) – Energy absorption:

400,000 rads heat H2O 1 deg

For general human exposure, these units are roughly

equivalent



Types of Radiation

Alpha (helium nucleus)

Beta (electrons)

Neutron (nuclear fission only)

X-rays (energetic electromagnetic radiation)

Gamma (more energetic than X-rays)



Ionizing Radiation

Ionizing radiation emitted may either photons (EM) or particles.

EM radiations (photons) differ in frequency, wavelength and energy.

The EM spectrum diagram shows the break point between ionizingradiation and nonionizing radiation.

Ionizing radiation has sufficient energy to disrupt the structure of anatom, causing the formation of charged ions.

These ions can cause chemical changes (damage) in human tissue andgenetic materials.



Ionizing Radiation

http://en.wikipedia.org/wiki/Image:Alphadecay.jpg



Alpha Radiation

Alpha particles are Helium nuclei consisting of two protons and two

neutrons.

They have a charge of +2, a mass of 4 AU (atomic units), and are veryenergetic.

The large charge and great mass makes them readily interact with

matter, giving them a short range (a few centimeters in air).

Alpha particles are of no concern as an external radiation hazard, but can

be a hazard if alpha-emitting isotopes enter the body through internalcontamination.

Generally we do not use alpha emitters at USD.

http://en.wikipedia.org/wiki/Image:Alphadecay.jpg



Beta Radiation

Beta particles are directly ionizing energetic electrons or positronsemitted from the atom as a spectrum of energies.

Some examples of pure beta emitters are 3-Hydrogen (tritium), 14-

Carbon, 35-Sulfur, and 32-Phosphorus.

The average energy of the betas emitted is about 1/3 of the maximumenergy beta emitted.

The mass of the beta is 1/1800 of an AU and it has a charge of +1(positron) or -1 (electron).

The range of a beta is dependent on it's energy and the material it istraveling in. For example; a P-32 beta particle has a range in air of about7 meters.

http://upload.wikimedia.org/wikipedia/commons/f/ff/Betadecay.jpg

http://upload.wikimedia.org/wikipedia/commons/f/fc/Gammadecay-1.jpg



Gamma Radiation

Gamma rays are electromagnetic radiation, having the highest frequencyand energy, and also the shortest wavelength, within the EMR spectrum.

Gamma rays are often produced alongside other forms of radiation suchas alpha or beta. When a nucleus emits an α or β particle, the nucleus issometimes left in an excited state. It can then jump down to a lower

level by emitting a gamma ray in much the same way that an atomicelectron can jump to a lower level by emitting UV or visible light.

Because of their high energy content, they are able to cause seriousdamage when absorbed by living cells.

Some examples of gamma emitters are 125-Iodine and 131-Iodine.

http://upload.wikimedia.org/wikipedia/commons/f/fc/Gammadecay-1.jpg



Background Radiation

Cosmic Rays

Solar Wind

Decay of Natural Radioactivity

Typical Doses

– Global Average 0.1 rem/year (80% natural)

– Some areas up to 1 rem/year

–Ramsar, Iran: up to 26 rem/year



Hazards of Radiation

Direct damage to organic molecules

Creation of reactive molecules and free radicals

DNA mutations – Birth Defects

– Sterility

– Cancer

Dangers of Radiation Types – Penetrating Ability

– Ability to create electric charges (ionize)



Nonionizing Radiation



The electromagnetic rays that do not have sufficient

energy to dislodge electrons in the body.

It does transmit energy to the atoms which give rise

to health effect. The shorter wavelength have higher energies than

larger wave length.

Nonionizing Radiation



Regions: Divided into three regions:

– Near 400 - 300 nm ( UV-A )

– Far 300 - 200 nm ( UV-B )

–Vacuum 200 -100 nm (UV-C )

Health Effects

– UV-A : Pigmentation of skin

– UV-B : Biological active & Potentially harmful

– UV-C : Bactericidal ; Germicidal

Ultraviolet



IR region

– Visible red light ( 750nm ) to 0.3-cm wavelength of microwaves.

Health Effects:

– Increase tissue temperature upon exposure depend on w/length.

– IR - A : 780 - 1400nm : absorbed through skin/cornea

– IR - B : 1400 -3000nm : Absorbed all in cornea/cataract

– IR - C : 3000 - 1mm : Damage to skin/eye

– Short w/length : Injured cornea, iris, retina and lens.

– Exposure to visible IR radiation from furnace - Glass blower

cataract / Heat Cataract.

Infrared



Region

– Within broadspectrum of Radio frequencies ( approx: 10-

300,000 MHz )

Health Effects – Thermal effects

– < 3000 MHz can penetrate skin and absorb by underlying

tissues.

–Serious damage can occur when underlying tissues such aseyes are exposed.

Microwave / Radiowave



Light Amplification by the Stimulated Emission of

Radiation.

– Coherent; Highly direction & low divergence

Health Effects – Permanent eye damage and skin bruises can result from

exposure to powerful lasers.

LASER



Radio Frequency (RF) Radiation and its

effects

Hazards of Electromagnetic Radiation to Personnel (HERP)

– Effects only possible at ten times the permissible exposure limit

– Heating of the body, Cataracts, Reduced sperm count in males, Shocks

or Burn, (Developing fetus is at no greater risk than mother)

Hazards of Electromagnetic Radiation to Ordance (HERO) – Premature activation of electro-explosive devices.

Electro Magnetic Interference (EMI)

– Interference with other electronic equipment



RF Radiation Standards

OSHA 29 CFR 1910.97 (a)(2)(i)

– For normal environmental conditions and for incident electromagnetic energy of

frequencies from 10 MHz to 100 GHz, the radiation protection guide is 10 mW/cm2.

(milliwatt per square centimeter) as averaged over any possible 0.1 hour period (6 minute

period)

OSHA 1910.268 - Telecommunication Industry

–Primarily safety requirements, such as electrical

– Mandates 1910.97 compliance for 1-300 GHz

– Describes “Tagout” of antenna 3-300 MHz

OSHA 1926.54, 20 - Construction Industry

– Includes tower erection, repairs and painting

– Limits MW to 10 mW/cm2. (no averaging)

–Requires Programs to provide safe work to employees and contractors; includes inspection

OSHA 1910.147 - Lockout/Tagout of Power

– Requires lockout / tagout of power during maintenance to prevent excessiveexposures

OSHA 1910.132 - Personal Protective Equipment

OSHA 1910.145, 1926.200 - Signs and Tags (Hazard Warning Signs)



BIOLOGICAL EFFECTS OF ELECTROMAGNETIC FIELDS

DETERMINED IN ANIMAL STUDIES

Reproduction, growth, and development - thermallyinduced teratogenesis, embryotoxicity and temporarysterility.

Immune and blood related - Stimulation of T & B

lymphocytes, immunosuppression, enhanced, naturallyoccurring tumors.

Nervous - Behavior changes, changes in Ca+2 flux, effectswith neuro-active drugs and chemicals.

Cardiovascular - Thermally induced increases in heart rate.

Ocular - Cataract formation, death of corneal endothelialcells, changes in retinal plexiform layers.

Neuroendocrine - Increased/ decreased hormone levels.



FACTORS THAT INCREASE THE RISK OF

DAMAGE FROM RF EXPOSURE

Thermally stressful environments

Use of alcohol

Some medication

Individual’s thermal sensitive

Unknowns



WAYS TO CONTROL RF RADIATION

EXPOSURE

Identify where the hazard areas are located

Post warning signage at site with potential

exposures.

Written guidelines

Employee training



EME ZONING

BLUE ZONE - areas < 20% of MPE

YELLOW ZONE - areas between 20 % and 100% of MPE

ORANGE ZONE - above 100% of MPE



Controls

Utilize low exposure equipment & site configuration – Use good equipment

– Control hazard areas

– Limit exposures

Access Restriction Maintenance of Controls

Lockout/Tagout

Signal Blocking or Blanking

Prevent access to hazardous locations (Signs & Fences) Standard Operating Procedures

Protective clothing





Exposure to Radiation

&

Radiation Hazards

B k d R di ti




Your exposure to radiation can never be zero becausebackground radiation is always present

Natural sources – radon gas

Cosmic rays Terrestrial (uranium-235)

Healing arts: diagnostic X-rays, radiopharmaceuticals

Nuclear weapons tests fallout

Research with radioisotopes

Consumer products Miscellaneous: air travel, transportation of radioactive material

Annual Dose from



Annual Dose from


Total US average dose equivalent = 360 mrem/year

Total exposure Man-made sources

Radon

Internal 11%

Cosmic 8% Terrestrial 6%

Man-Made 18%

55.0%

Medical X-Rays

Nuclear

Medicine 4%

Consumer

Products 3%

Other 1%

11

C P d N l M di i



Consumer Products, Nuclear Medicine

–Smoke detectors (Am-241)

– Welding rods (Th-222)

– Television (low levels of X-rays)

– Watches & other luminescent

products (tritium or radium) – Gas lantern mantles

– Jewelry

Hands and dials contain H-3 or

radium that glows in the dark

X-rays and fluoroscopes are

used to look inside the body

Wh i R di ti H f l?



Why is Radiation Harmful?

Radiation deposits small amounts of energy, or "heat"in matter

– Alters atoms

– Damage to cells & DNA causes mutations and cancer

– Similar effects may occur from chemicals

– Much of the resulting damage is from the production of ions

R di ti D



Radiation Dose

Human dose is measured in rem or millirem

1000 mrem = 1 rem

1 rem poses the same risk for any type of ionizing

radiation – internal or external

– alpha, beta, gamma, x-ray, or neutron

External radiation exposure measured by dosimetry

Internal radiation exposure measured using bioassaysample analysis

A t E



Acute Exposure

Large doses received in a short time period

accidents

nuclear war

cancer therapy

Short term effects (acute radiation syndrome

150 to 350 rad whole body)

Anorexia Epilation

Nausea DiarrheaFatigue Hemorrhage

Vomiting Mortality



ALPHA PARTICLES

– Interact electrically with human tissues and other matter.

Range 10 cm in air.

–Hazardous when taking into the body.

– Tend to accumulate in kidney, lung, liver and spleen.

– No effect when outside the body.



BETA PARTICLES

– Ejected from nuclei by disintegration of Radioactive atoms.

– Maximum range wood : 4 cm

–Human body penetration : 0.2 to 2.3 cm.

– High excessive dose may cause skin burns.



NEUTRONS

– Release by nuclei disintegration of Radioactive atoms. (

Fissionable isotopes ).

–The range and extend of damage to human depend on thecharacteristic of material they pass through.

– Human body penetration : 0.6 cm approx. depending on the

neutron energy.

–Emit secondary radiations ( alpha, beta, gamma. etc) oncollision with atoms.



GAMMA RADIATION:

– Similar to x-radiation

– Penetration depend on the wavelength

–The shorter wave length have greater penetrating powerand will penetrate several centimeters of steel.

– They are capable of penetrating deep into tissues and cause

ionizing.



COMMON EFFECTS:-

– Skin redness, Dermatitis, Skin Cancer, hair loss, eyes

inflammation.

–Damage to the bone marrow resulting a blood disease.

– Damage the digestive systems

– Radiation Sickness

– Mutagenesis ; Carcinogenesis ; Teratogenesis



Background exposure to ionizing radiation

Each of us receive about 300 mRem/year from natural sources. These include – solar cosmic radiation, – radon (a gas from soil) – internal dose from Potassium-40.

We also receive about 70 mRem from man-made sources, primarily from medicalapplications.

Therefore your altitude above sea level and the location and building materials of your home can also influence your background dose.

For example: the background dose for a person living in Denver is about twice thedose in San Francisco.



Internal vs. External Exposure

External exposure is the passage of particulate or EM radiation into tissuefrom outside the body.

Internal exposure results from isotopes which have been deposited insidethe body.

Internal deposition results from:

– ingestion

– inhalation

– absorption through the skin

–skin punctures.



Acute vs. Chronic Exposure to Radiation

Chronic exposures are received over many years.

– The biological effects of chronic whole body doses up to regulatorylimits (150 Rem over 30 years) have proven undetectable and maynot exist.

Acute exposure is received in a few hours. – The biological effects of acute whole body doses <10 Rem have

proven undetectable and may not exist.

– At acute doses of 10-75 Rem, temporary changes in blood cellchromosomes have been observed.

– At acute doses of >75 Rem, biological effects include erythema (skinreddening), and acute radiation syndrome (ARS - loss of hair, nausea,dehydration and possible death)

– The LD50/30 for humans (the lethal dose for 50% of a populationexposed within 30 days without medical treatment) is 300-350 REM.

– At an acute dose of 550 Rem, 99% of those exposed may die.

S ti G ti Eff t



Somatic vs. Genetic Effects

Somatic effects occur in the person receiving the radiationdose.

– Somatic effects can be caused by acute or chronicexposure.

–Cancer is a somatic effect identified with radiationexposure.

Genetic effects occur in the descendants of the person

receiving the radiation dose. – Genetic effects can be caused by acute or chronic

exposure.

– Mental retardation is a genetic effect identified with

radiation exposure.



Human Radiation Sources

Nuclear Fallout from Atmospheric Testing (USand Russia, 1963; France, 1974; China, 1980)

Chernobyl 1986

Uranium Mining

Radon release from construction and earth-

moving

Conventional power plants



Human Survival Limits

200 rem (whole body): few immediate fatalities

500 rem (whole body): 50% fatalities

1000 rem (whole body): No survivors



Radiation Protection



Posting of Radiation Areas

All radiation areas are posted with

warning signs

Use caution when entering and

working in a radiation area

If any container is labeled

“radioactive” do not disturb

CAUTION RADIATION



© Aduchem 2008 FlindersSecurity55

CAUTION - RADIATION

CAUTION RADIATION

THE GENERAL WARNING SIGN

is accompanied by SPECIFIC INFORMATION

FOR RADIONUCLIDES




FOR RADIONUCLIDES

CAUTION RADIATION

RADIATION AREA - RADIONUCLIDES

LICENSED SUPERVISOR J. SMITH Telephone ……

RADIATION SAFETY OFFICER M. JONES Telephone ……

FOR X RAY MACHINES




FOR X-RAY MACHINESCAUTION

RADIATION

THIS APPARATUS PRODUCES RADIATION WHEN

ENERGISED

LICENSED SUPERVISORJ. SMITH Telephone …….

RADIATION SAFETY OFFICER M. JONES Telephone …….

WARNING LIGHTS show when the machine is ON

Emergency Response



Emergency Response

Fire in radioactive areas: – Notify Fire Department and RSO, clear the area of people.

Remove any seriously wounded persons. Keep your distance

Notify RSO if you suspect: – Inhalation, ingestion or other intake of radioactive material

– Accidental release of radioactive material into theenvironment



Radiation Protection Basics

Time: minimize the time that you are in contact withradioactive material to reduce exposure

Distance: keep your distance. If you double the distance the

exposure rate drops by factor of 4

Shielding:

– Lead, water, or concrete for gamma & X-ray

– Thick plastic (Lucite) for betas

Protective clothing: protects against contamination only - keepsradioactive material off skin and clothes

Radiation Exposure Will Not



Radiation Exposure Will Not

Make You Radioactive

Radiation: energy in the form of particles and waves

Radioactive material: material that is unstable andemits radiation

Contamination: radioactive material where it is notwanted

Campfire example: burning logs (radioactive material),heat (radiation), burning embers that escape the

controlled area (contamination)

L b l P k



Labels on Packages

of Radioactive Material

Radioactive white I; almostno radiation (0.5 mR/hr or0.005 mSv/hr) maximumon the surface

Radioactive yellow II; lowradiation levels (50 mR/hror 0.05 mSv/hr) maximumat 1 meter

Your Role



Your Role

in Radiation Protection

Don’t touch or move anything with radioactive

material labels.

Report anything that looks out of the ordinary

If you are uncertain about what to do, where to go,requirements, or exposures: Contact your RSO or EHS



Use of Shielding

Radiation shielding functions on the principle of attenuation(reduction in force, weaken).

Particles or EM radiation deposit energy in the shieldingmaterial and are thereby attenuated.

Energy deposited in the shield cannot be absorbed in tissue,reducing the radiation hazard.

The ranges of various particulate radiations and the densities of various shielding are well known.

These values can be used to determine the type and thicknessof material required to reduce or stop particulate radiation.



Alpha particles, due to their mass and charge,readily interact with matter and are stopped by asingle sheet of notebook paper.

Low Z materials should be used to shield betaparticles. For example: all P-32 betas will beattenuated in 0.8 cm. of Lucite.

In general, 1.0 cm. of Lucite is sufficient to absorbany beta radiation.

Using to high Z materials such as lead shield betasmay result in Bremsstrahlung production, replacing

the beta particle hazard with an x-ray hazard.

Lead, concrete and steel are the best shieldingmaterials for photons (gamma emitters).





Radiation units

The Curie (Ci) is the most commonly used unit of

radioactivity (and used at USD).

A Curie is equal to 3.7 x 1010 (nuclear) disintegrations per

second (dps) or 2.22 x 1012 disintegrations per minute (dpm).

Internationally, the Becquerel (Bq) is often used.

A Bq is equal to 1 dps.

Because the Ci is so large and the Bq is so small, we often

use prefixes to define levels of activity. – We most often order milliCuries (mCi) or microCuries

(μCi) at USD.





Basic elements to external radiation protection



p

program

1. Time - decrease length of exposure to radioisotopes. Radiation field measurements are always expressed as a rate,

i.e. mRem/hr (or cpm).

2. Distance -maintain the max. distance from radiation

sources that still allows the work to be done Ionizing radiation follows the inverse square law the intensity

of the radiation field decreases with inverse square of thedistance from the source.

For example, standing twice as far from a source will reduce

the radiation field intensity to 1/4 of the original intensity. From a source such as a test tube or vial, a distance of a few

centimeters will greatly reduce the dose to the extremities.







Li iti i t l



Limiting internal exposure

Use good laboratory hygiene

Use proper labeling

Monitor for contamination

– Survey meter (Geiger Mueller)

– Wipe test

Dispose of waste properly

Decontaminate if needed





Posting and Labeling of



Posting and Labeling of

Radioisotope Use Locations

Identify areas selected for radioisotope use.

– Identify work, storage and waste areas

Limit radioisotope use to those identified areas

Limit exposure of yourself, coworkers, and the

community to the exposure hazard in that area

Regularly monitor radioisotope use locations for

contamination



How to Safely Use Radioisotopes

Receive proper training

Learn required information about the isotope and theprotocol you will use

Utilize proper technique and GLP

ALARA

Maintain a healthy respect for the biological hazards of ionizing radiation

Demonstrate responsibility

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5 Radiation