Radiological Awareness

Objectives

• Identify types of radiation• Identify terminology and risks associated with

radiation• Identify self aid procedures for protection against

radiation exposure

Sets the stage for understanding the what/why about your radiation detection equipment

Pretest

• Check your knowledge about radiation• Fill in your answers now• Keep until class is done, compare your answers

Ionizing Radiation

• Ionizing radiation is electromagnetic energy or energetic particles emitted from a source

− Electromagnetic energy: radio waves, light, x-rays, etc. − Source: unstable atoms of any material− Ionize: To strip electrons from other atoms causing

chemical changes in molecules

Alpha Radiation

• Heavy charged particles• Highly ionizing• Not penetrating

− Travel several centimeters in air or a few microns in tissue

− Stopped by paper or clothing

• Internal hazard

Beta Radiation

• High energy small particle• Moderately penetrating

− Up to a few meters in air− Several millimeters in tissue

• Primarily internal hazard, some external

Gamma Radiation or X-rays

• High energy rays• Very penetrating• Difficult to shield• Protective clothing will not protect

against photon radiation• External and internal hazard

Neutron Radiation

• Uncharged high speed particle• Can be very penetrating• Requires special consideration for

shielding• External and internal hazard – but –

not likely to encounter neutron radiation

Examples of RadioactiveMaterials

Substance Emit Use

• Americium 241 a, g Smoke detectors

• Cobalt 60 b, g Medical therapy

• Cesium 137 b, g Many industrial uses

• Radium 226 a Medical therapy

• Uranium 238 a, b, g Reactors and weapons

• Iridium 192 b, g Industrial radiography

Radiation Half-life

• Time required for a radioactive substance to lose half of its radioactivity

− Each radionuclide has a unique half-life− From a fraction of a second to millions of years

Examples:Tc-99m 6.0 hrsI-131 8.05 daysCo-60 5.26 yrsSr-90 28.1 yrsPu-239 24,400 yrsU-238 4,150,000,000 yrs

Units of Measure

• Rad (Gray) = absorbed dose• Roentgen (R) = energy

− Dose rate expressed in R/h, mR/h, μR/h− Counts per minute (cpm) - measure of energy from

surface contamination (not the same as R/hr)

• For gamma and x-ray, 1 R ~ 1 rad

Units of Measure (Cont.)

• Rem (sievert) - amount of damage suspected from a particular type of radiation dose

− (1R = 1 rad = 1 rem) gamma = 20 rem alpha

• Curie (becquerel) - amount of material in terms of its radioactivity

− Compare 1 Ci = 37 billion Bq

Background Radiation

• Natural sources of radiation (~ 260 mrem/yr)− Cosmic radiation− Radioactive material in the environment

• Radon is largest contributor

− Radioactive material in the body

• Manmade sources (~ 100 mrem/yr)− Medical and dental procedures− Releases to the environment− Commercial / industrial sources

Radiation Doses In Perspective

• Natural background and manmade radiation 360 mrem/yr(~20 +/- μR/h is background)

• Diagnostic chest x-ray 10 mrem

• Flight from LA to Paris 4.8 mrem

• Barium enema 800 mrem

• Smoking 1.5 packs per day 16,000 mrem/yr

• Heart catheterization 45,000 mrem

• Mild acute radiation sickness 200,000 mrem

• LD50/60 for radiation 450,000 mrem

ALARA

Goal of exposure management:

keep radiation exposures to a level

As Low As Reasonably Achievable

(ALARA)

Radiation Exposure Risks

s Thyroid Lung

LiverBone

Irradiation Externalcontamination

IncorporationInternalcontamination

Increasing risk

Self Protection Measures

• 1st Avoid exposure and contamination− Detect radiation exposure− Back away when too high

• 2nd Use Personal Protective Equipment (PPE)• 3rd Decontaminate yourself

Radiation Protection Basics

• Time

• Distance

• Shielding

• PPE

Time

Source Result Dose25 mrem

100 mrem per hour x 15 minutes (.25 hour) = 25 mrem

Distance

1 meter 1 meter

Dose rate is ¼ when distanceis doubled

100 mrem/hr 25 mrem/hr

Source

The “four times” rule

Shielding

• Alpha

• Beta

• Gammapaper lead

Simplified Radiation PPE

• Protect your respiratory tract− Respirator, surgical mask, etc.

• Protect your skin− Gloves!− Outer clothing− Chemical suit is not always needed

Detect Ionizing Radiation

• Not detected by human senses• Requires use of detection instruments• No single instrument can detect or measure all

types of radiation

can't smell it can't see it

Radiation Detection Instruments

• Dosimeter measures dose received (odometer)− Track personal exposure

• Survey instrument detects and measures dose rate (speedometer)

− Find source of radiation− Find surface contamination

• Area monitor is a fixed site survey meter− Entry alert

Self Decontamination

• Wash it off− Hand washing− Tepid water, mild soap− No scrubbing

• If showering, use shampoo• Remove and launder clothing• Monitor after decon

Radiation Summary

• Recognize types, terms, and risks of ionizing radiation

• Understand self protection measures − Time, distance, shielding− PPE− Detecting radiation− Self decon

• Review answers to pretest