Radiation safety benefits and risks
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Radiation Safety benefits and risks - PowerPoint PPT Presentation

Radiation Safety benefits and risks Accidental and avoidable exposure to ionizing radiation is a risk. Effects of ionizing radiation on life depend on types of radiation, rates of receiving, and dosages (amounts) received.

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Radiation Safety benefits and risks

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Radiation Safetybenefits and risks

Accidental and avoidable exposure to ionizing radiation is a risk.

Effects of ionizing radiation on life depend on types of radiation, rates of receiving, and dosages (amounts) received.

Natural ionizing radiation include cosmic rays, X-rays and gamma rays from space, and natural radioactivity.

Risk will be discussed in terms of types, rate of receiving, and dosages using well defined units and quantities .

Dose Units & Radiation Safety

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Early Experiences of Radiation Effects

Early workers exposed to X-rays developed dermatitis.

Uranium miners developed skin lesions.

People working with radioactivity experienced illness.

Researchers exposed to radioactivity suffered radiation sickness at advanced age.

Manhattan project workers in Los Alamos, Oak Ridge, Hanford, and atomic worker in the former USSR suffered anorexia, fatigue, headache, nausea, vomiting, and diarrhea.

Dose Units & Radiation Safety

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Collective Response to Radiation Risk

In 1928, the International Committee on X-ray and Radium Protection was formed to look into the risk of radiation. It is now called International Commission on Radiological Protection, ICRP.

In 1942, a group of health physicists had the responsibility to assess problems and implement safe operation procedures regarding radioactivity.

After WW2, the (American) National Council of Radiation Protection (NCRP) was formed in 1946.

Guidelines are given for radioactive material handling and applications.

Today, safety committee is set up to deal with radiation risks.

Dose Units & Radiation Safety

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Mission Statement of the ICRP

The International Commission on Radiological Protection, ICRP, is an independent Registered Charity, established to advance for the public benefit the science of radiological

protection, in particular by providing recommendations and guidance on all aspects of protection against ionising


From www.icrp.com

check with ICRP for up-to-date guidance regarding radiation

Dose Units & Radiation Safety

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National Policies on Ionizing Radiation

The Environmental Health Directorate of Canada is concerned with radiation risks. Safety Codes were prepared by the Radiation Protection Bureau of Health Canada. The latest change was made in October 1999.

Working with ionizing radiation must follow guidelines for the organization and for the workers. Safe practice is more than follow guidelines to the letter. Apply common sense to avoid as much exposure as possible.

URLhc-sc.gc.ca /ehp/ehd/catalogue /rpb_pubs/99ehd237.htm.

Dose Units & Radiation Safety

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Radiation Effects

Somatic effectsdamages to cells passed on to succeeding cell generations.

Genetic effectsdamages to genes that affect future generations.Genes are units of hereditary information that occupy fixed positions (locus) on a chromosome. Genes achieve their effects by directing the synthesis of proteins.

Somatic effects and genetic effects show no immediate symptoms

Dose Units & Radiation Safety

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Somatic Effects

Damages to cell membranes, mitochondria and cell nuclei result in abnormal cell functions, affecting their division, growth and general heath.

Organs such as skin, lining of gastrointestinal tract, embryos, and bone marrow, whose cells proliferate rapidly are easily damaged.

Bone marrow makes blood, and its damage leads to reduction of blood cell counts and anemia.

Damage to germinal tissues reduces cell division, and induces sterility.

Dose Units & Radiation Safety

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Genetic Effects

Human cells contain 46 chromosomes. Germ or ovum cells contain 23.

A chromosome contains a deoxyribonucleic acid (DNA) molecule.

The double-helix DNA has two strands of phosphoric-acid and sugar linked bases of Adenine, Guanine Cytosine or Thymine.

The A-T and G-C pairs stack on top of each other.

The DNA codon transcripts mRNA, which directs the amino-acid sequences of protein. DNA Damages result in somatic and genetic effects.

When DNA molecules replicate (pass on to next generation), they are sensitive to radiation damage. Joining wrong ends of broken DNA is called Translocation, which cause mutation and deformation at birth.

Genetic effects increase frequency of mutation.

Dose Units & Radiation Safety

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Genetic Effects - DNA Molecules

The double-helix DNA has two strands of phosphoric-acid and sugar linked bases of Adenine, Guanine Cytosine or Thymine.

The A-T and G-C pairs stack on top of each other.

Dose Units & Radiation Safety


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Genetic Effects - Replication of DNA


Dose Units & Radiation Safety

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Transcription of DNA


Dose Units & Radiation Safety

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AL-MADA'IN, Iraq - Dozens of people are showing up every day at a hospital near a defunct Iraqi nuclear plant, suffering from rashes, bloody noses and other symptoms of radiation poisoning, doctors said Saturday.

The Tuwaitha nuclear facility, 12 miles south of Baghdad, was left unguarded after Iraqi troops fled the area on the eve of the war. (News, Jun, 2003)

Dose Units & Radiation Safety

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Radiation Absorption and Dosage


RadioactivityBq, Ci

  

Exposure dose Gy, rad (R)

Quality factorQ

Biological doseSv, rem

The amount of energy absorbed from exposure to radiation is called a dose. The radiation effect measured by a dosimeter reflects an equivalence of certain dosage of X-rays. The amounts are defined in certain units as shown here.

Dose Units & Radiation Safety

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Units for Radiation Source (review)

The SI unit for radioactivity is Bq (1 becquerel = 1 dps).

The decayis not necessary all absorbed unless it’s internal.

1 Curie = 3.7e10 Bq.

These units have nothing to do with energy, type (a, b, g, X-rays, neutrons, protons or particles), and effect of radiation.

Commonly used units







these modifiers are also used for other units.

Dose Units & Radiation Safety

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Dose Units - roentgen, rad, and gray

Amounts of absorbed energy are not the same as exposed.The amount of radiation energy absorbed is called a dose.

A roentgen ( R) is a dose of X- or -rays that produce 1 esu charge (negative and positive each or 2.1e9 ion pairs) in 1.0 L.

1 R = 352.1e9 = 7.35e10 eV (*1.6x10-12 erg/eV) = 0.12 erg (per 0.00123 g air) = 1 rad (100 erg per g of any substance)

1 Gy = 1 J / kg (1 J per kg of any substance is a gray, Gy) = 1e7 erg / kg = 100(100 erg/g)~100 rad

Dose Units & Radiation Safety

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Integral Dose Used in Radiation Therapy

  • Total energy absorbed by an organ called integral dose is gram-rad or g-rad or g-Gy total dosage received by an organ.

    • g-Gy = dose * mass of the organ

  • Accumulated dose is the dose received over a period, but g-Gy is the total dose received in a single time.

Dose Units & Radiation Safety

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The Quality Factor Q and Dosage Units

Quality factor (Q) or (rbe) of various radiations.

RadiationQ or rbe

X-, - and  rays1

Thermal neutrons (n)3

Fast n, , and protons10

Recoil nuclei20

The factor reflecting the relative harmfulness of various types of radiation is called the quality factor (Q) or relative biological effectiveness (rbe)

Biological dose = Q * exposure dose

Dose Units & Radiation Safety

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Exposure and Biological Dosage


RadioactivityBq, Ci

  

Exposure dose Gy, rad (R)

Quality factorQ

Biological doseSv, rem

SI unit cgs unit

Exposure unit1 Gy = 100 rad (=100 R)

Biological dose1 Sv = 100 rem (= Qrad)

Gy: gray, Sv: sievert, R: roentgen, rem: roentgen equivalent man

Dose Units & Radiation Safety

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Summary of Units for Radioactive Dosage

QuantitySymbolSI unitcgs unitConversion factor

radioactivityABqCi1 Ci = 3.7e10 Bqexposure doseXC/kgR1 C/kg = 3876 Rabsorbed doseDGy (J/kg)rad1 Gy = 100 rad =6.24 eV/gbiological doseHSv (Q*Gy)rem1 Sv = 100 rem

Dose Units & Radiation Safety

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Exposure Limit

Maximum permissible dosage of workers in radiation zone

Max. accumulated Max. dose/13 wk mSvmSv

Whole body 50(age-18) 30

Hands and 250 (750/y)forearms

1 Sv = 1000 mSv = 100 rem

Dose Units & Radiation Safety

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Dosimeters for Dosage Monitoring

Dosimeters are devices to measure exposed doses.

Film-badges, electroscopes, ionization chambers, biological and chemical dosimeters have been used for radiation monitors.

Plants, cells, bacteria, and viruses reacting to radiation are biological dosimeter candidates.

Ferrous sulfate, FeSO4, solution is a chemical dosimeter due to the reaction:4 Fe2+ + energy + O2 4 Fe3+(brown) + 2 O2-

Some glasses and crystals serve as solid state dosimeters.

Shelf life, linearity, stability, usage simplicity, easy-to-read, dose-rate and equal responses to various radiation are some considerations.

Dose Units & Radiation Safety

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Chemical 3-dimensional Dosimeter

Ferrous ions, Fe2+, are oxidized by ionizing radiation, and convert to ferric ions, Fe3+, which complexes with xylenol orange dye to give an orange compound.

When the sample is prepared in a gel form, it serves as a 3-dimensional dosimeter, because the complexes are localized in the gel. These dosimeters are useful for planning radiation medical treatments such as radiation cancer treatment.

Dose Units & Radiation Safety

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A Dosage Evaluation Example

A 5-MeV  particle is absorbed by 1 gram of water, estimate the dosage in rad and rem.

The Q factor is 10 for  particle, and thus the dose is 8e-7 rem or 8e-9 Sv.

If the a particle is absorbed by a of 10-9 g cell, then the dose is 109 times higher (0.8 Gy, 8 Sv), exceeded lethal dose for most living beings.

Dose Units & Radiation Safety

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Natural Radiation Sources

Cosmic rays consist of high-energy protons, helium ions, heavier nuclei, and some electrons. They cause nuclear reactions generating secondary electrons and radioactivity.

The terrestrial radiation sources are natural radioactive nuclides.

Some Natural Occurring Radioactive Nuclides

Nuclides (t½ ~ 106-15 y)Radiation

235, 238U, 232Th and their off springs, , 

144Nd, 147, 148, 149Sm, 152Gd, 186Os, 190, 192Pt ()

40K, 87Rb, 115In, 123Te, 138La, 176Lu, 187Re, 210Bi etc.+, , EC ()

Nuclides produced by cosmic rays

14C (5730 y), 3T (15 y), 7Be (53 d), 10Be (2.7×106 y)

Dose Units & Radiation Safety

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Artificial Radiation Sources

X-rays are generated by stopping fast moving electrons. A chest X-ray exam is exposed to less than 0.01 Sv, more if multiple images are taken.

Accelerators generate high-speed electrons, atomic nuclei, high-energy particles, and synchrotron radiation.

Nuclear explosions leave radioactive fission products.

Nuclear reactors are sources of ionizing radiation.

Leakage of radioactive nuclides contaminates environment.

Nuclear-waste areas are sources of radiation.

Uranium mining tailings are more radioactive than natural sources.

Dose Units & Radiation Safety

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Low-dosage Exposures

Background annual exposure


natural occurring sources0.8 medical procedures (X-rays)0.8others0.2weapon tests0.05consumer products0.04airline travel0.005Total1.9

Low-dose exposures in addition to natural background radiation have delayed somatic and genetic effects.

Dose Units & Radiation Safety

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High-dosage Exposures

Symptoms develop shortly in high-dosage exposures.

1 Sv or lower dose exposure has little immediate symptoms.

1-2 Sv exposures cause nausea and occasional vomiting in a few days. Victims survive when infection is medicated.

2-4 Sv exposures cause anorexia, fatigue, nausea and vomiting, diarrhea, low chance to survive.

4-5 Sv, lethal dose (LD50), absorption lead to disorientation and shock due to injury to central nervous and cardiovascular systems.

Dose Units & Radiation Safety

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Radiation Injuries

Whole-body radiation victims mostly suffer from injuries to the hemopoietic, gastrointestinal (GI), and central nervous (CN) systems.

Injuries to the hemopoietic system lead to bone morrow syndromes with low red and white cells and platelet counts.

The GI syndromes are anorexia, fatigue, nausea, vomiting, and diarrhea. GI system failures weakens body defence.

Damages to the isolated and non-renewable CN system show ataxia (loss of motion control), disorientation, apathy, depression, prostration (exhaustion), convulsions, and shock.

Organs such as skin, gonads, and eyes are sensitive to radiation.

Dose Units & Radiation Safety

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A Summary

Early experiences led to the discoveries of radiation effects.

Radiation causes delayed somatic and genetic effects due to damages to cells and the DNA molecules.

Quantities of radiation, absorbed or exposed doses, and biological effective doses must be expressed in units.

Exposure limits for workers are guidelines, and limits for the general public are 100th of those for workers.

Some principles of dosimeters have also been discussed.

Understanding radiation sickness symptoms and injuries leads to a peaceful mind.

Dose Units & Radiation Safety

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