Training for Users of Radiation Producing Devices

This training course has been partially adaptedfrom slides provided by Steve Backurz, RadiationSafety Officer of The University of New Hampshire

Elayna MellasRadiation Safety Officer

Environmental Health & Safety ManagerClarkson UniversityDowntown Snell 155

Tel: 315-268-6640emellas@clarkson.edu

Subject Slides

Nuclear Physics 3-17

Biological Effects 18-43

Radiation Exposure and Dose 31-47

Uses of Radiation 48-51

Radiation Hazards 52-59

Radiation Detection 60-66

Lab Procedures at Clarkson 67-74

Table of Contents

Introduction• Radiation is a valuable tool used in research

at Clarkson– Electron microscopes– X-ray fluorescence spectrometry– X-ray diffraction analysis of samples for

chemistry and engineering research• Radioactive materials and X-ray machines

are very safe if used properly and simple precautions are followed

Radioactivity ("Activity")Definition: A collection of unstable atoms that undergo spontaneous transformation that result in new elements.

An atom with an unstable nucleus will “decay” until it becomes a stable atom, emitting radiation as it decays

Sometimes a substance undergoes several radioactive decays before it reaches a stable state

The “amount” of radioactivity (called activity) is given by the number of nuclear decays that occur per unit time (decays per minute).

Ion

Any atom or molecule with an imbalance in electrical charge is called an ion

In an electrically neutral atom or molecule, the number of electrons equals the number of protons

Ions are very chemically unstable, and will seek electrical neutrality by reacting with other atoms or molecules

Radiation

Definition: Energy in the form of particles or waves

Types of Radiation Ionizing: removes electrons from atoms

Particulate (alphas and betas)Waves (gamma and X-rays)

Non-ionizing (electromagnetic): can't remove electrons from atoms

infrared, visible, microwaves, radar, radio waves, lasers

The Electromagnetic Spectrum

Radiation Wavelength in Angstrom Units

Photon Energy in Million Electron Volts (MeV)

108 106 104 102 1 10-2 10-4 10-6

X-RaysRadio Infrared Visible

Ultra-VioletLight

Gamma Rays

Cosmic Rays

10-10 10-8 10-6 10-4 10-2 1 10222 4 10

Gamma Radiation

Wave type of radiation - non-particulate Photons that originate from the nucleus of unstable atoms

No mass and no chargeTravel many feet in airLead or steel used as shielding

X-Rays Wave type of radiation - non-particulate Photons originating from the electron cloud Same properties as gamma rays relative to mass,

charge, distance traveled, and shielding Characteristic X-rays are generated when electrons fall

from higher to lower energy electron shells Discrete energy depending on the shell energy level

of the atom Bremsstrahlung X-rays are created when electrons or

beta particles slow down in the vicinity of a nucleus Produced in a broad spectrum of energies Reason you shield betas with low density material

Bremsstrahlung Radiation

Energy is lost by the incoming charged particle through a radiative mechanism

Beta Particle

-Bremsstrahlung Photon

+ +

Nucleus

X-Ray Machine Components

High Voltage

Power Supply

Tungsten Filament

Target

Glass Envelope

Tube Housing

CathodeAnode

Current

X-Ray Machine Basics

kVp - how penetrating the X-rays are Mammography - 20 - 30 kVp Dental - 70 - 90 kVp Chest - 110 - 120 kVp

mA - how much radiation is producedTime - how long the machine is on Combination of the above determines exposure

Types of Radiation

Mass (amu) Charge Travel Distance in Air

Alpha

Beta Plus

Beta Minus

Gamma

X-Rays

Neutron

4.0000

0.0005

0.0005

0.0000

0.0000

1.0000

+2

+1

-1

0

0

0

few centimeters

few meters

few meters

many meters

many meters

many meters

Interaction of Radiation with Matter

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

alters atomschanges molecules

damage cells & DNA similar effects may occur from chemicals Much of the resulting damage is from the

production of ion pairs

Ionization

Ionization by a Beta particle:

-

-

-

-

The neutral absorber atom acquires a positive charge

Beta Particle

-

CollidingCoulombic Fields

ejected electron

Gamma Interactions

Gamma interactions differ from charged particle Interactions

Interactions called "cataclysmic" - infrequent but when they occur lot of energy transferred

Three possibilities: May pass through - no interaction May interact, lose energy & change

direction (Compton effect) May transfer all its energy & disappear

(photoelectric effect)

Compton Effect An incident photon interacts with an orbital electron

to produce a recoil electron and a scattered photon of energy less than the incident photon

Before interaction After interaction

-

--

Incoming photonCollides with electron

--

--

Electron is ejected from atom

-

Scattered Photon

Biological Effects of Radiation

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 Nausea ErythemaFatigue Vomiting Hemorrhage

Epilation Diarrhea Mortality

Effects of Acute Whole Body Exposure on Man

AbsorbedDose (Rads) Effect

10,0001,200

600450100

5025

5

Death in a few hoursDeath within daysDeath within weeksLD 50/30Probable RecoveryNo observable effectBlood changes definite1st Blood change obs

Chronic Exposure

Doses Received over Long Periods Background Radiation Exposure Occupational Radiation Exposure

50 rem acute vs 50 rem chronic acute: no time for cell repair chronic: time for cell repair

Average US will receive 20 - 30 rem lifetimeLong Term Effects

Increased Risk of Cancer 0.07% per rem lifetime exposure Normal Risk: 30% (cancer incidence)

• Ionization within body tissues: similar to water• Ionization causes many derivatives to be formed:

PeroxidesFree RadicalsOxides

• These compounds are unstable and are damaging to the chemical balance of the cell. Various effects on cell enzymes and and structures occur.

• Radiation is not the only insult responsiblePollutantsVitamin imbalance (poor diet)Sickness and Disease

Cellular Effects

Cellular Effects (con't)

Cells often recover from damageRepeated Insults may cause damage to be

permanent Cell Death Cell Dysfunction - tumors, cancer, cataracts,

blood disorders Mitosis (Cell Division) Delayed or Stopped Chromosomal breaks Organ Dysfunction at High Acute Doses

Variations in Sensitivity

Wide variation in the radiosensitivity of various species

Plants/microrganisms vs. mammalsWide variation among cell types

Cells which divide are more sensitive Non-differentiated cells are more

sensitive Highly differentiated cells (like nerve

cells) are less sensitive

Effects on the Fetus

The fetus consists of rapidly dividing cellsDividing cells are more sensitive to radiation effects than nondividing cells

Effects of low level radiation are difficult to measure

A lower dose limit is used for the fetus

Genetic EffectsIt is possible to damage the hereditary material in a

cell nucleus by external influences like Ionizing radiation, chemicals, etc.

Effects that occur as a result of exposure to a hazard while in-utero are called teratogenic effects

Teratogenic effects are thought to be more severe during weeks 8-17 of pregnancy - the period of formation of the body’s organs

A higher incidence of mental retardation was found among children irradiated in-utero during the bombings of Hiroshima and Nagasaki

Maternal Factors & Pregnancy

Statistically, a radiation exposure of 1 rem poses much lower risks for a woman than smoking tobacco or drinking alcohol during pregnancy

SmokingGeneral Babies weigh 5-9 oz. Less than average

< 1 pack/day Infant Death 1 in 5> 1 pack/day Infant Death 1 in 3

Alcohol2 drinks/day Babies weigh 2-6 oz. Less than average 1 in 10

2-4 drinks/day Fetal alcohol syndrome 1 in 3> 4 drinks/day Fetal alcohol syndrome 1 in 3 to 1 in 2

Radiation1 rem Childhood leukemia deaths before 12 years 1 in 33331 rem Other childhood cancer deaths 1 in 3571

Dose Response Curves

Dose Dose

Effects occur after a threshold

Effects occur at any level = stochastic

Acute effects Chronic effects?

Bio

log

ical

eff

ects

The stochastic model is more conservative, and is used to establish dose limits for occupational exposure

Rate of Absorption

Most important factor in determining when effects will occur

Recovery is less likely with higher dose rates than lower dose rates for an equivalent amount of dose = more permanent damage

More recovery occurs between intermittent exposures = less permanent damage

Area Exposed

The larger the portion - the more damage (if all other factors are the same)

Blood forming organs are more sensitive

A whole body dose causes more damage than a localized dose (such as in medical therapy).

Dose limits take this into consideration

Radiation Exposure & Dose

Background Exposure Your exposure to radiation can never be zero because

background radiation is always present Natural Sources - Radon Cosmic Terrestrial Technologically Enhanced Sources (Man-Made) Healing Arts: Diagnostic X-rays, Radiopharmaceuticals Nuclear Weapons Tests fallout Industrial Activities Research Consumer Products Miscellaneous: Air Travel, Transportation of Radioactive

Material

Annual Dose from Background Radiation

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

NuclearMedicine 4%

ConsumerProducts 3%

Other 1%

11

Cosmic Radiation

2 x 10 particles (mostly protons) per second are incident on the atmosphere

Energy greater than one BILLION ELECTRON VOLTS

Interact with atoms in the atmosphere and produce secondary particles

muons, electrons, photons, and neutrons responsible for cosmic dose

18

Terrestrial

Major sources Potassium - a few grams per 100 grams of

ground material Thorium and Uranium - a few grams per

1,000,000 grams of ground materialDose due mainly to photons originating near

the surface of the ground

Radon

Naturally occurring radioactive gas Second leading cause of lung cancer Estimated 14,000 deaths per year Easy to test for

short and long term tests available EPA guideline is 4 pCi/L Fixable Radon in water from drilled wells can also

be an entry method

Exposure, X

A measure of the ionization produced by X or Gamma Radiation in airUnit of exposure is the Roentgen

X = Q (charge)

M (mass of air)

Absorbed Dose, D

Absorbed Dose (or Radiation Dose) is equivalent to the energy absorbed from any type of radiation per unit mass of the absorber

Unit of Absorbed Dose is the rad1 rad = 100 ergs/g = 0.01 joules/Kg

In SI notation, 1 gray = 100 rads

Dose Equivalent, HOne unit of dose equivalent is that amount of any type of radiation which, when absorbed in a biological system, results in the same biological effect as one unit of low LET radiation

The product of the absorbed dose, D, and the Quality Factor, Q

H = D Q

Units of Dose EquivalentHuman dose measured in rem or millirem1000 mrem = 1 rem1 rem poses equal risk for any ionizing radiation

internal or external alpha, beta, gamma, x-ray, or neutron

In SI units 1 sievert (Sv) = 100 remExternal radiation exposure measured by

dosimetry Internal radiation exposure measured using

bioassay sample analysis

Quality Factors for Different Radiations

Quality FactorX and Gamma RaysElectrons and MuonsNeutrons < 10 kev >10kev to 100 Kev > 100 kev to 2 Mev >2 MevProtons > 30 MevAlpha Particles

115

1020101020

External Dose2 Standard reference points

Shallow Dose: Live skin tissue at an average depth of .007 cm.

Deep Dose: Internal organs close to the body surface, 1 cm.

Shallow Dose Equivalent, SDE Alpha radiation not a hazard consider beta and gamma radiation.

Deep Dose Equivalent, DDE Alpha and Beta radiation not a hazard. For gamma, SDE = DDE (typically)

Internal DoseAll radiation types present a hazard2 Dose quantities:

Committed Dose Equivalent, CDE (specific to a particular organ)

Committed Effective Dose Equivalent, CEDE (sum of all organs x weighting factor for importance or each specific organ)

Total Effective DoseEquivalent, (TEDE)

Used to combine internal and external doses

Puts all dose on the same risk base comparison, whether from external or internal sources.

TEDE = CEDE + DDEAll units are in rems or Sieverts (Sv)All regulatory dose limits are based on controlling the TEDE

• Radiation Protection Program Required• Occupational Limits

5 rem per year TEDE 50 rem per year CDE (any single organ) 15 rem per year lens of the eye 50 rem per year skin dose

• Members of Public 100 mrem per year No more than 2 mrem in any one hour in

unrestricted areas from external sources• Declared Pregnant Females (Occupational)

500 mrem/term (evenly distributed)

Standards for Rad Protection

Declared Pregnant Woman

Voluntarily informs her employer in writing of pregnancy

Estimated date of conceptionDose limit is 10% of occupational limit (500 mrem)

Avoid substantial variation in doseForm for declaring pregnancy is on web site

Clarkson AnticipatedWorker Radiation Exposure

Anticipated Exposures: Less than the minimum detectable dose for film badges (10 mrem/month) - essentially zero

Average annual background exposure for U.S. population = 360 mrem/year

State and Federal Exposure Limits = 5000 mrem/year

Uses of Radiation

Consumer Products

Building materials Tobacco (Po-210) Smoke detectors (Am-241) Welding rods (Th-222) Television (low levels of X-rays) watches & other luminescent products

(tritium or radium) Gas lantern mantles Fiesta ware (Ur-235) Jewelry

Research at ClarksonUsing Radiation Sources

Radioactive Materials (both open and sealed sources)

Gas Chromatographs (sealed sources) Liquid Scintillation Counters (sealed

sources for internal standards) X-ray Diffraction equipment Electron microscopes X-ray fluorescence spectrometer

MedicalDiagnostic

X-rays Nuclear Medicine (Tc-99m, Tl-201, I-123) Positron Emission Tomography (PET)

Therapeutic X-rays (Linear Accelerators) Radioisotopes

Brachytherapy (Cs-137, Ir-192, Ra-226)Teletherapy (Co-60)Radiopharmaceuticals (I-131, Sr-89, Sm-153)

Radiological Hazards

Radiation Protection BasicsTime: minimize the time that you are in contact

with radioactive 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

External Radiation Inverse Square Law

Radiation levels decrease as the inverse square of the distance (i.e. move back by a factor of two, radiation levels drop to one fourth)

Applies to point sources (distance greater than 5 times the maximum source dimension)

where I = Intensity (exposure rate) at position 1 and 2 andR = distance from source for position 1 and 2

Position 1Position 2

(mrem/hr) (mrem/hr)

Source

222

211 RIRI

R1

R2 I2

I1

Gamma Ray Constant

Gamma Ray Constant to determine exposure rate

(mSv/hr)/MBq at 1 meterHint: multiply (mSv/hr)/MBq by 3.7 to get (mrem/hr)/uCi

Exposure Rate Calculation, X (mrem/hr) at one meter:

X =Where, A = Activity (Ci)

Gamma Ray Constant(mSv/hr)/Mbq 3.7 is the conversion factor

Sample Calculation

• 5 Curie Cs-137 Source• Calculate Exposure Rate at 1 meter

= 1.032 E-4 mSv/hr/MBq @ 1 meter

X = 1.032 E-4 * 3.7 * 5 Ci * 1000 mCi/Ci * 1000 uCi/mCi

X = 1909 mrem/hour

X = 1.91 rem/hour

Gamma Ray Shielding

Effectiveness increases with thickness, d (cm)

Variation with material, (1/cm)attenuation coefficients µHigh Z material more effective

Water - Iron - Leadgood - better - best

Shielding Beta EmittersLow energy betas (H-3, C-14, S-35) need no

shielding for typical quantities at ClarksonHigher energy beta emitters (P-32) should be

shieldedBeta shielding must be low Z material (Lucite,

Plexiglas, etc.)High Z materials, like lead, can actually generate

radiation in the form of Bremsstrahlung X-raysBremsstrahlung from 1 Ci of P-32 solution in

glass bottle is ~1 mR/hr at 1 meter

External vs Internal Dose

TEDE: Total Effective Dose Equivalent

TEDE = DDE + CEDE Total Dose = External Dose + Internal Dose

1 rem internal (CEDE) same as 1 rem external (DDE)

Internal dose is protracted over several years but calculated over 50 years and assigned in the year of intake

Radiation Detection

• Solid State Detectors Germanium Lithium

High Purity Silicone Lithium Silicone Diode Cadmium Telluride

Radiation Detector TypesGas Filled Detectors

Geiger Mueller (GM) Gas Flow Proportional

Counters Ionization

Scintillation Detectors Sodium Iodide (NaI) Zinc Sulfide (ZnS) Anthracene Plastic Scintillators

Gas Filled Detectors Ionization detectors

High CostSurvey metersReference class calibration chambers

Proportional countersHigh costGross laboratory measurementsContamination monitors

Geiger Mueller (GM) detectorsLow costSurvey metersContamination monitors

Scintillation DetectorsOne of the Oldest Detection Methods, Still Widely Used Today

Transducer Converts Radiation Energy to Visible Light

Visible Light Signals Amplified With Photomultiplier Tube

Output PM Tube Signal ProcessedHigh Efficiency For Photon Detection Compared To Gas-Filled Detectors

Use of Survey Instruments

Check Physical ConditionCables, Connections, DamageCheck for Current Calibration (License Requirement)

Battery CheckZero CheckResponse check prior to useSelect Proper ScaleResponse Time (Fast or Slow?)Audio (On or Off)

CPM & DPM

A radiation detector will not detect every disintegration from a source (i.e., they are not 100% efficient)

Counts per minute (cpm) is the number of disintegrations that a detector “sees”

The efficiency of a detector is determined by the following:

Efficiency = net cpm / dpm= gross cpm – background cpm /

dpm

• U. S. Nuclear Regulatory Commission Regulates the nuclear industry pursuant to the

Atomic Energy Act Regulatory guides published to describe

methods for complying with regulations• Agreement States

Some states have entered into an agreement with the NRC to regulate by-product material (and small quantities of source and special nuclear material)

Currently, 30 states are agreement states including New York

Regulatory Agencies

Radiation at ClarksonActivities are licensed by the State of New YorkRadiation Safety Committee has responsibility

to review, approve, and oversee activitiesRadiation Safety Officer (RSO) runs programClarkson is required to:

Train individuals that use sources of radiation

Train non-radiation workers that work in the vicinity of radiation sources

Monitor and control radiation exposures Maintain signs, labels, postings

Posting & Labeling Notices Posting

New York Notice to employees form Caution Radiation Producing Devices or X-

Rays

Employee Rightsand Responsibilities

Right to report any radiation protection problem to state without repercussions

Responsibility to comply with the Radiation Protection Program and the RSO's instructions pertaining to radiation protection

Right to request inspectionin writinggrounds for noticesigned

Responsibility to cooperate with NY State inspectors during inspections and RSO during internal lab audits

ALARA

The goal of radiation protection is to keep radiation doses As Low As Reasonably Achievable

Clarkson is committed to keeping radiation exposures to all personnel ALARA

What is reasonable?Includes: -State and cost of technology

-Cost vs. benefit-Societal & socioeconomic

considerations

• Inspections NY shall be afforded opportunity to inspect at

all reasonable times Records shall be made available Inspector may consult with workers privately Worker may bring matters to inspector

privately Workers can request inspection

• Must be in writing • Name is not revealed

Inspections

• Internal audits by Clarkson RSO are performed in all labs on campus

• Looking for same things as state inspector Security of radiation producing devices Proper procedures in use Postings, dosimetry, survey meters,

calibrations, records of surveys, etc.

Internal Audits

Your Rolein Radiation Protection

Report anything that looks out of the ordinary or if you are uncertain about what to do, where to go, requirements, exposures:

Call the people on the emergency list

Ask the Radiation Safety Officer (RSO)Elayna Mellas268-6640emellas@clarkson.edu

Acknowledgements

This training course has been adapted from slides provided by Steve Backurz, Radiation Safety Officer of The University of New Hampshire