Industrial Radiography

Occupational exposures and protection

A. H. Mehrparvar, MDOccupational Medicine departmentYazd University of Medical Sciences

History 500 BC: Democritus postulates that all matter is made

of indivisible units they call "atomos." 1895 (Nov 8): Roentgen discovers X-rays. 1896: First diagnostic X-ray in US (E. Frost) 1896: Thomas Edison reports eye injuries from X-

rays 1896: First therapeutic applications of X-rays

Many nobble prizes in this issue

Types of radiation Ionizing

Electromagnetic energy X-ray Gamma ray

Subatomic particles Electron Proton Neutron

Non-ionizing infrared, visible, microwaves, radar, radio waves, lasers

Radiation spectrumRadiation wavelength in angstrom units

10 8 10 6 10 4 10 2 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 10 2

Photon energy in million electron volts (MeV)

22 4 10

Definitions Radioactivity (Bq, Ci) LET (linear energy transfer) (kev/μm) Absorbed dose (Gy, Rad) Equivalent dose (Sv, Rem) Effective dose (Sv, Rem)

Radiation Units:

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%

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Occupational exposure Aircrew Dental worker Radiologist Radiology technicians Reactor worker Electron microscopist Industrial radiographer

Plasma torch operators High-voltage TV repairman Underground Uranium

miner Atomic power plant worker

Organ excposuresBone marrow (mGy)

Breast (mGy)Gonads (mGy)Effective dose (mSv)

Chest0.040.0900.04

Chest CT5.9210.087.8

Skull0.2000.1

Head CT2.70.0301.8

Abdomen0.40.032.2, 0.41.2

CT5.60.78, 0.77.6

IVP1.93.93.6, 4.34.2

Mamography0200.1

Barium enema

8.20.716, 3.48.7

Radiation Sourcesx-ray generatorsgamma ray sources

Imaging ModalitiesSeveral different imaging methods are available to display the final image in industrial radiography:

• Film Radiography

• Digital radiography

•Real Time Radiography

•Computed Tomography (CT)

•Computed Radiography (CR)

Industrial Radiography

• Application: use of radiography for the non-destructive testing (NDT) of items

• a means of checking the physical integrity of equipment and structures such as vessels, pipes, welded joints, castings and other devices

Industrial radiography (cont.)• Sensitive to changes in thickness, corrosion, cracks,

and material density changes• Technique is not limited by material type or density• Can inspect assembled components• Detects both surface and subsurface defects• Provides a permanent record of the inspection• often carried out under difficult working conditions,

such as in confined spaces, extreme cold or high temperatures.

Radiographic Images

Radiographic Images

Radiographic Images

Radiation Bioeffects Deterministic (non-stochastic)

Severity increases with radiation dose Threshold: 50-100 rem Dose and dose rate dependent Examples

Cataract induction Epilation (hair loss) Erythema (skin reddening) Blood changes

Radiation Bioeffects Stochastic (probabilistic)

Probability of occurrence increases with radiation dose Threshold: 10 rem, but regulatory models assume no

threshold (ALARA!) Examples

Cancer induction Genetic mutations Developmental abnormalities

Deterministic Radiation Effect Thresholds

HEALTH EFFECT ORGAN DOSE (rem)

Temporary sterilityTestis 15

NauseaGI 35

Blood cell depressionBone marrow 50

Reversible skin effectsSkin 200

Permanent sterilityOvaries 250 - 600

VomitingGI 300

Temporary hair lossSkin 300 - 500

Permanent sterilityTestis 350

Skin erythemaSkin 500 - 600

Stochastic Radiation Effects Cancer

incidence begins to increase in populations acutely exposed to more than 10 rem

continues to increase with increasing dose Genetic Effects

more than 100 rem of low-dose rate, low LET radiation needed to double the incidence of genetic defects in humans

no human hereditary effects seen at gonadal doses less than 50 rem In Utero Irradiation

developmental and other effects begin to increase at 10 rem

Somatic effects Short Term

ARS Hemopoietic (bone marrow

syndrome) 100-1000 rad 25 rad can depress blood count Gastointestinal (600-1000 rad) CNS (5000 rad)

Locally Erythema 300-1000 rad Epilation Delay/suppress menstruation 10

rad

LONG TERM Cataract Reduced fertility Fibrosis Organ atrophy Sterility Cancer Embryologic effects

Biologic effects of radiation on pregnant women Spontaneous abortions during first 2 weeks of

pregnancy-- 25 RAD or higher 2nd week to 10th week – major organogenesis –IF

radiation is high enough can cause congenital abnormalities

Principle response after that may be malignant disease in childhood

Tissue sensitivityVery HighWhite blood cells (bone marrow)

Intestinal epitheliumReproductive cells

HighOptic lens epitheliumEsophageal epithelium

Mucous membranes

MediumBrain – Glial cellsLung, kidney, liver, thyroid, pancreatic epithelium

LowMature red blood cellsMuscle cells

Mature bone and cartilage

Radiation workers Any person working with radioactive substances two groups of radiation workers:

Group A: worker can receive more than 30% of the annual dose equivalent limit, must undergo routine medical examinations and have personal monitoring devices.

Group B: radiation worker will not receive more than 30% of the annual dose equivalent limit, do not undergo medical examinations or have to carry monitoring devices.

Occupational exposure limits

Occupational exposure limits (cont.)

Action Level of 1.0 mSv/y

provide and ensure the proper use by workers of an acceptable dosimeter or radiation badge

perform radiation surveys to measure radiation levels in work areas

provide written instructions on safe and proper procedures and practices related to the use of the radiation-emitting device

Technicians who work with radiation must wear monitoring devices that keep track of their total absorption, and alert them when they are in a high radiation area

Survey Meter Pocket Dosimeter Radiation Alarm Radiation Badge

Radiation Safety

Ring badge

How to Correctly Wear Your Badge Whole body badges should be worn between the neck

and the waist Ring badges can be worn on any finger  The badge should be on the inside of your palm,

facing the radioactive work

ProtectionTwo principles:

Justification (no exposure)

Optimization (ALARA)

ALARA Principle

• keep all radiation doses well below the regulatory limits and As Low As Reasonable Achievable (ALARA)

• ALARA (as low as reasonable achievable) limits are 10% of these: 

• 500 mrem deep•1500 mrem eye• 5000 mrem shallow extremity

                 

Types of Radiation Exposure

External - from gamma photons, x-rays or high-energy beta particles emitted from a source outside the body

Internal - from sources inside the body, which presumably came to be there following ingestion or inhalation of contamination

                 

Protection Against Internal Exposure Pathways of contamination:

Inhalation, ingestion, wound, through skin

Minimization awareness of the hazard

good laboratory technique

use of personal protective equipment (ppe) such as gloves, lab coats and fume hoods

proper and timely performance of surveys for radioactive contamination

Protective Gloves

Lab Coat

Personal Protective Equipment

Fume Hood

Protection Against External Exposure The three important factors in protecting against

external exposure are: time distance and shielding 

Judicious use of a combination of these factors can minimize radiation exposure

Radiation SafetyThere are three means of protection to help reduce

exposure to radiation:

Personal protective devices

Shielding Shields that reduce gamma ray intensity by 50% (1/2)

include: 9cm (3.6 inches) of packed soil 6 cm (2.4 inches) of concrete 1cm (0.4 inches) of lead 150 m (500 ft) of air

Guidelines for protection There must be at least one person designated as the

responsible user or radiation protection officer (RPO) to undertake responsibility for: Proper function and miantanance of equipment Equipment used and maintained only by competent

personnel Correct use of equipment establishing safe operating procedures Increasing awareness of staff about radiation rules investigating any high x-ray exposures received by personnel ensuring that radiation levels outside controlled areas are

below the maximum permissible limits

Radiographers should: Follow the local rules and any other relevant procedures Properly use radiation monitors Wear their individual dosimeters, at the correct location at

all times during radiography and source handling Co-operate with the RPO and qualified expert on all

radiation safety issues Participate in any training concerning radiation safety

General requirements Warning Signs

                        

> 5 mrem/hour

           

> 100 mrem/hour

               

> 500 rem/hour

                    

Depends on radionuclide: > 10 mCi H-3, 1 mCi S-35, 0.1 mCi P-32,

0.001 mCi I-125   

Markings All controls, meters, lights and other indicators relevant to the

operation of the equipment must be readily discernible and clearly labelled or marked as to function

Indicator Lights There must be readily discernible, separate indicators on the

control panel that respectively indicate: (i) when the control panel is energized and the machine is ready to

produce xrays,and (ii) when x-rays are produced.

Exposure Control exposure switch, timer, or other device to initiate and

terminate x-ray production. the exposure switch must: (i) require continuous pressure by the operator to produce x-rays (ii) be so located that convenient operation outside of a shielded area is

not possible (iii) for mobile x-ray equipment, be equipped with a cable at least three

metres long.