presenter_on-site_00 1 radiation protection fundamentals craig maxwell - rct radiation protection...

Presenter_On-Site_00 1

Radiation Protection Fundamentals

Craig Maxwell - RCT

Radiation Protection Group

Lawrence Berkeley National Laboratory


Objectives

• Familiarize you with some of the basics of Radiation and Radioactive Decay

• Discuss some of the common instruments found in research labs

• Review control methods used to reduce exposure


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Nucleus

Neutrons

Protons

Electrons(Electron Clouds)

Structure of the Atom


Ionizing radiation High energy radiation

• Gamma-rays, x-rays - photons• Particles: alpha, beta, neutron

Ejects electrons from atoms• Produces an altered atom - an ion

Non-ionizing radiationLow energy

• Lasers, RF, microwaves, IR, visible

Excites electrons• Produces heat


Alpha Decay4He Nucleus

Ejected from NucleusYour skin will stop it

internal hazard

stopped by paper

found in soil, radon and other radioactive materials


Beta DecayEither too many neutrons or too many protons

stopped by plastic

skin, eye and internal hazard

Naturally occurring in food, air and water


Gamma / X-ray Decay• Emission of a photon • Often occurs after or when nucleus is in an excited state

stopped by lead

medical usesnaturally present in soil and cosmic radiation


Types of Ionizing Radiation

Alpha

Beta

Gamma and X-rays

Neutron

Paper Plastic Lead Concrete

Helium nucleus (2 protons, 2 neutrons): +2 charge

Electron: +1 or -1 charge

Photon: 0 charge

Neutron: 0 charge


Radiation Quantities and Units

RadioactivityQty: ActivityUnit: Curie (Bequerel) 1 Ci = 1000 mCi 1 Bq = 1 dis per sec 1 Ci = 3.7 e10 Bq

Radiation RiskQty: Dose EquivalentUnit: rem (Sievert) 1 rem = 1000 mrem 1 Sv=100 rem

Radiation Absorbed DoseQty: DoseUnit: rad (Gray) 1 rad - 1000 mrad 1 rad = 100 erg/gram 1 Gy=100 rad

roentgen

equivalent

man


Radiation Weighting Factors (WR)

Absorbed dose (Rad/Gy) x WR =

Equivalent dose (rem)Photons, electrons & muons (all

energies) 1

Beta & positron 1

Neutrons 5-20

Alpha, fission fragments, heavy nuclei 20

10CFR835


Sources of Ionizing Radiation

Radioactive materials

• Naturally occurring (uranium, carbon-14, …)• Artificial (activated by neutrons from a reactor or accelerator beam)

Radiation Producing Machines

•X-ray machines (characteristic, bremstrahlung)• Accelerators (ion beams, neutrons, x-rays)


Background and Manufactured Radiation In the U.S. Contributes 360 mrem per year


Manufactured Sources of Radiation

Cigarette Smoking - 1300 mrem

Building Materials - 3.6 mrem

Fallout < 1

Smoke Detectors - 0.0001

Medical – 53 mrem

mrem

mrem

Medical Doses:

A: Dental exam (16 mrem)

B: Mammogram (25 mrem)

C: Tc-99m cardiac function (75 mrem)

D: Cranial CT multiple scans (up to 5 rem)

E: “Full body CT screening” – one scan ( 1 to 2 rem)

F: Spiral whole body CT scan ( 3 to 10 rem)


Whole Body Annual Dose Limits

RADIATION WORKER - Federal NRC Limits

Whole Body - 5000 mrem/year

Extremities - 50,000 mrem/year

Skin - 50,000 mrem/year

Eyes - 15000 mrem/year

Pregnant - 500 mrem/term / 50 mrem/month

General Pubic - 100 mrem/year


Effect of Dose and Dose Rate

100 rems

20 years

5 min

Chronic exposures may increase cancer risk. 100,000 people

exposed to 100 mREM 4 or 5 additional cancers

Localized effects:

>500 REM Skin –

radiation burn

Whole body effects:

LD50/30 500 RAD


Risk Perspective

Average Estimated Days Lost Due to Daily Activities

Health Risk Ave. Est. Days Lost

Unmarried Male 3,500

Cigarette Smoking 2,250

Unmarried Female 1,600

Coal Miner 1,100

25% Overweight 777

Alcohol (U.S. average) 365

Construction Worker 227

Driving a Motor Vehicle 207

100 mrem/year for 70 years 10


Radiation

vs

Contamination


Radiation Vs. Radioactive Contamination

Radiation is particles or waves of energy emitted from unstable atoms.

Radioactive Contamination is radioactive material usually in any location you do not want it.

Exposing a material to radiation does not necessarily make it

radioactive, but radioactive material on a non-radioactive item, makes the item contaminated.


Radiation Survey Meters

Two common Ion Chamber radiation survey instruments are:

VictoreenBicron


Beta Contamination Instrument

Ludlum 3

Type: Normally equipped with a Geiger-Mueller 44-9 (pancake) probe

Detects: Beta, gamma


Alpha/Beta Contamination Instrument

Ludlum 2224

Type: Plastic scintillation for beta detection that has a [ZnS (Ag)] coating for alpha detection

Detects: Alpha and Beta


Other Instrumentation

Ludlum 16 with a 44-3 thin window NaI probe

Liquid Scintillation (LSC)


Instrument performance

• Dead or low batteries - erratic or no detection

• Calibration has changed - may read high or low

• Defective cable or other problems

• Poor survey technique– angle of probe to source - only detects part– to far from source - radiation absorbed by air– survey too fast – only detects part

You must use them correctly if you expect them to work for you


Radiation & Contamination

Control Methods

Used to reduce exposure to

radiation and

radioactive material contamination


Engineering Controls

• Containment– Glove box– Glove bag

•Ventilation

– Fume Hood

– Bio Safety Cabinet


Engineering Controls cont.

• Interlocks

• Tamper-Proof Screws/Bolts

• Flange Padlocks

• Security Seals

• Shielding

• Access controls (e.g. card key)


Administrative Controls

• Regulations

• Formal Authorizations

• Facility policies and procedures

• Labels, signs, and postings

• Routine radiation surveys

• Machine operational restrictions


ALARA As Low As Reasonably Achievable

ALARA Techniques:

• Time - (Reduce)

• Distance – (Increase)

• Shielding – (Proper Shielding)

Reduce Radiation

Doses


Control Methods

• Engineering

• Administrative

• ALARA Techniques• Time• Distance• Shielding

• Missing Control


Exposure Prevention Methods

• Protective clothing such as lab coats, gloves & safety glasses

• Self-monitoring to reduce the spread of radioactive contamination


Good Work Practices

Use deliberate movements and apply lessons learned from cold runs (mock-ups).


Respect and Understand the Postings

Treat all radiological areas as if everything was contaminated.


Common sources of radioactive contamination

– Sloppy work practices

– Poor housekeeping

– Opening radioactive materials/systems without proper controls

– Leak or tears in containers

– Damaged Sealed Sources

– Spills


Upon Completion of Work

Be sure to survey yourself


Upon Completion of Work

Hand washing is a good work practice and an important final step after working with any radioactive material.


Final Thoughts

• It is our mission to ensure that research and learning continue in the safest manner possible.

• Be a mentor

• Be a resource

• Lead by example

• Always use best practices

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