RADIOACTIVTY AND ITS APPLICATIONS

Dr Manjunatha S

College of Computer and Information Sciences

Majmaah University

KSA

Presentation outlines

• Introduction to radioactivity
• Sources of radionuclides
• Background radiation
• Applications of radioactivity
• Conclusion

Japanese Fukushima nuclear disaster (2011 ),

• Japanese Fukushima nuclear disaster (2011 )
• shut down the nation's 54 nuclear power plants.
• 2013 repots - highly radioactive, with some 160,000 evacuees still living in temporary housing.
• Some land will be unfarmable for centuries.
• The difficult cleanup job will take 40 or more years
• Cost tens of billions of dollars

• Fukushima Daichi, March 11, 2011�An 8.9 magnitude earthquake and subsequent tsunami overwhelmed the cooling systems of an aging reactor along Japan's northeast coastline. The accident triggered explosions at several reactors at the complex, forcing a widespread evacuation in the area around the plant.

August 10. 1985, Russia, the Echo II class submarine suffered an explosion, sending a radioactive cloud of gas into the air. Ten sailors were killed in the incident and 49 people were observed to have radiation injuries.

The abandoned city of Prypiat, Ukraine, Chernobyl disaster, Russia (1986).

• One of the worst nuclear accidents till date.
• The accident killed 30 people directly and damaged approximately $7 billion of property.
• A study published in 2005 estimates that there will eventually be up to 4,000 additional cancer deaths related to the accident among those exposed to significant radiation levels.
• Radioactive fallout from the accident was concentrated in areas of Belarus, Ukraine and Russia. Approximately 350,000 people were forcibly resettled away from these areas soon after the accident.

• Chernobyl, April 26, 1986�The Chernobyl disaster is considered to be the worst nuclear power plant disaster in history. On the morning of April 26, 1986, reactor number four at the Chernobyl plant exploded. More explosions ensued, and the fires that resulted sent radioactive fallout into the atmosphere. Four hundred times more fallout was released than had been by the atomic bombing of Hiroshima.

Mushroom cloud from the atomic explosion over Nagasaki, Japan rising 60,000 feet into the air on the morning of August 9, 1945.

• On August 6, 1945, the uranium-type nuclear weapon, code named "Little Boy" was detonated over  Hiroshima with an energy of about 15 kilotons of TNT
• Destroying nearly 50,000 buildings and killing approximately 70,000 people.
• On August 9, a plutonium-type nuclear weapon code named "Fat Man" was used against the Japanese city of Nagasaki with the explosion equivalent to about 20 kilotons of TNT.
• Approximately 35,000 people killed.

What is radioactivity?

Nuclear decay or radioactivity, is the process by which a nucleus of an unstable atom loses energy by emitting ionizing radiation.

A material that spontaneously emits this kind of radiation which includes the emission of alpha particles, beta particles, gamma rays and conversion electrons 

Who discovered radioactivity?

Antoine Henri Becquerel

Marie Curie

Why are elements radioactive?

Unstable nucleus:

• Has excess energy.
• Wants to go to “ground state.”
• Becomes stable by emitting ionizing radiation.

Radiation Types

Alpha Particles (2n, 2p)

Beta Particles (e- or +)

Photons (hv)

(x or gamma rays)

Paper

Concrete

Three Common Types of Radioactive Emissions

Dr Manjunatha S, CCIS

Alpha

Beta

Gamma

The electromagnetic spectrum

Figure courtesy of NASA/JPL-Caltech

Half life and mean life

Half-life is the time required for half of the atoms of a radioactive material to decay to another nuclear form.

Mean life is average of all half lives

• Primordial Radionuclides

That radionuclides that are present since the creation of earth and having long half-lives, e.g. ²¹⁰Pb, ²²⁶Ra, K⁴⁰

3. Cosmogenic Radionuclides

That radionuclides that are produced in the upper atmosphere as a result of cosmic rays interaction with light particles (carbon, Nitrogen and Oxygen), e.g. C¹⁴, ⁷Be, ²²Na, ³²P, ³²S

3. Anthropogenic Radionuclides

That radionuclides that are produced as a result of man-made activities such as nuclear fuel fabrication, enrichment, nuclear power generation, nuclear accidents etc., e.g. ¹³⁷Cs, ¹³⁴Cs, ¹³¹I, ⁹⁰Sr etc.

Sources of radioactivity

Units of Radioactivity

• The Becquerel (Bq): Disintegration per second, dps
• The curie (Ci)

1 Ci = 37,000,000,000 Bq

so 1 mCi = 37 MBq; and 1 µCi = 37 kBq

• rem: Rem is the term used to describe equivalent or effective radiation dose.
• In the International System of Units, the Sievert (Sv) describes equivalent or effective radiation dose. One Sievert is equal to 100 rem.

Natural background radiation

• The natural radiation energy between few KeV to MeV from primordial radionuclides are called background radiation.
• Background radiation is of terrestrial and extra-terrestrial origin.

1. Terrestrial radiation components

• The terrestrial component originates from primordial radionuclides in the earth’s crust, present in varying amount.
• Components of three chains of natural radioactive elements viz. the uranium series, the thorium and actinium series.
• ²³⁸U, ²²⁶Ra, ²³²Th, ²²⁸Ra, ²¹⁰Pb, ²¹⁰Po, and ⁴⁰K, contribute significantly to natural background radiation.

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2. Extra terrestrial radiation

• Among the singly occurring radionuclides tritium and carbon-14 (produced by cosmic ray interactions) and ⁴⁰K (terrestrial origin) are prominent.
• Radionuclides from these sources are transferred to man through food chains or inhalation.

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1. Terrestrial radiation components contd…

• The extra terrestrial radiation originates in outer space as primary cosmic rays.
• The primary cosmic rays mainly comprise charged particles, ionised nuclei of heavy metals and intense electromagnetic radiation.

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3. Artificial Radionuclides

• Over the last few decades man has artificially produced hundreds of radionuclides.
• Artificial radioisotopes to the atmosphere during the course of operation of the nuclear fuel cycle, nuclear tests (mainly atmospheric) and nuclear accidents
• Most of the artificial radioisotopes decay -short half-lives. Therefore only a few of them are significant from the point of human exposure.

Radon

• Radon is a radioactive gas decay product of radium, created during the natural breakdown of uranium in rocks and soils

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• It is one of the heaviest substances that remains a gas under normal conditions and is considered to be a health hazard causing cancer

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• It has three isotopes, namely, ²²²Rn (²³⁸U), ²²⁰Rn (²³²Th) and ²¹⁹Rn (²³⁵U). ²²²Rn has longer half life (3.84 days) than the other two isotopes

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Radon in Buildings

There are two main sources for the radon in home's indoor air, soil and water supply.

Sources of background radiation

Dr Manjunatha S, CCIS

Radioactivity – is it a health problem?

• The Alpha, Beta and Gamma particles all add energy to the body’s tissues. The effect is called the Ionizing Energy. It can alter DNA.
• Even though Alpha particles are not very penetrative if the decaying atom is already in the body (inhalation, ingestion) they can cause trouble.

Dr Manjunatha S, CCIS

Biological Effects: Mechanisms of Injury

Ionizing Radiation

Cell Damage

Repair

Transformation

Radiation Dose

Dose or radiation dose is a generic term for a measure of radiation exposure. In radiation protection, dose is expressed in millirem.

External Dose

X-Ray Machine

Contamination

Contamination is the presence of a radioactive material in any place where it is not desired,

and especially in any place where

its presence could be harmful.

Yuck!

The radium dial painters

• Watch-dial painters - United States Radium factory in Orange, New Jersey, around 1917 .
• The Radium Girls (4000) were female factory workers who contracted radiation poisoning from painting watch dials withself-luminous paint.
• They were used to tip (i.e., bring to the lips) their radium-laden brushes to achieve a fine point.
• Unfortunately this practice led to ingested radium, and many of the women died of sicknesses related to radiation poisoning.
• The paint dust also collected on the workers, causing them to “glow in the dark.”
• Some also painted their fingernails and teeth with the glowing substance.

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�Who’s the Famous “Madame” of Radiological Fame?

Marie Curie

• With her husband Pierre, discovered radium and coined the term “radioactive”
• First woman to win two Nobel Prizes

Medical Applications

Radioisotopes with short half-lives are used in nuclear medicine because they have the same chemistry in the body as the nonradioactive atoms.

• In the organs of the body, they give off radiation that exposes a scan giving an image of an organ.

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Thyroid scan

To find the location of a leak in a shallowly buried

pipe without excavation

Leak Detection

This use of radionuclide tracers to find leaks or flow paths has wide applications:

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• Finding the location of leaks in oil-well casings,
• Determining the tightness of abandoned slate quarries for the temporary storage of oil,
• Locating the positions of leaks in refrigeration coils,
• Finding leaks in heat exchanger piping,
• Locating leaks in engine seals.

Thickness control

• The manufacture of aluminium foil, β emitter is placed above the foil and a detector below it.
• Some β particle will penetrate the foil and the amount of radiation is monitored by the computer.
• The computer will send a signal to the roller to make the gap smaller or bigger based on the count rate

Living Tissue ¹⁴C/¹²C, Tissue ratio same as atmospheric ratio

Dead Tissue ¹⁴C/¹²C < ¹⁴C/¹²C, tissue ratio is less than atmosphere

t ½ = 5730 yr.

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Mummified remains found frozen in the Italian Alps

At least 5000 years old By carbon-14 dating

In 1991, hikers discovered the body of a prehistoric hunter that had been entombed in glacial ice until the ice recently moved and melted.

Space Exploration

• Radioisotope Thermoelectric Generator (RTG)

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• If two dissimilar metals were joined at two locations that were maintained at different temperatures, an electric current would flow in a loop.
• In an RTG, the decay of a radioisotope fuel provides heat to the “hot” junction, while the other junction uses radiation heat transfer to outer space to maintain itself as the “cold” junction.

Space Exploration

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The fuel in:

• Satellites
• Jupiter Probe
• Others

Jupiter Probe

An RTG loaded with 1 kilogram of plutonium (238) dioxide fuel would generate between 21 and 29 watts of electric power for the spacecraft.

After five years of travel through space, this plutonium-fueled RTG would still have approximately 96 percent of its original thermal power level available for the generation to electric power

Power Generation

Nuclear power supplies 19.4 percent of energy in the United States.

There are 104 nuclear power plants in the United States.

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Photo by Karen Sheehan

Nuclear Medicine

Diagnostic Procedures

• Short half-life radioactive injection
• Pictures taken with special gamma camera
• Many different studies:

Thyroid

Lung

Cardiac

White Blood Cell

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Photo by Karen Sheehan

Bone Scans

Image courtesy of

Radiation Therapy

Used for treating cancer.

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External Beam

Brachytherapy (implants)

Image courtesy of

Photo by Karen Sheehan

Some Radioisotopes Used in Nuclear Medicine

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Crop improvement by mutation techniques

• Higher yielding
• Disease-resistance
• Well-adapted
• Better nutrition

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Mutant cultivars

no mutation

negative mutation

Mutation techniques

- Improving crop cultivation

- Enhancing biodiversity

- Increasing farmer’s income

Crop improvement by mutation techniques

MUTANT VARIETIES

Total Number : 2672

Plant Species : 170

(2006)

Sources: FAO/IAEA Mutant Varieties Database

Insect Pest Control

Gamma Radiation

No Offspring

(BIRTH CONTROL)

Sterile

Sterile

Preservation of food and agricultural product by radiation

• An alternate method of food preservation by irradiation of X ray or gamma rays.
• It is used to prolong the shelf life of many food and agricultural products, destroy bacteria and microorganisms in food (pre packed or bulk) and grains(rice, corn..).
• The food exposed to controlled amount of ionizing radiation in shielded area for a specific time to achieve desirable objectives.
• The sources are gamma rays from Cobalt 60 or Cesium 137, X-rays up to 5 MeV or electron accelerators up to 10 MeV.

Does the irradiation process make food radioactive?

• Irradiation under controlled condition does not make food radioactive.
• Irradiation involves passing the food through and allow to absorb desired radiation energy.
• Radiation processing of food do not induce any radioactivity.

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Food preservation

Onion and potato are irradiation by

0.05 to 0.15 kGy

Effect of gamma irradiation treatment in delay ripening

Pear delay in ripening and decaying of under ambient condition.

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Peach after 7 days of ambient storage

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Effect of gamma irradiation and edible coating treatment on storage quality of varieties (after 100 days of ambient storage.

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Effect of gamma irradiation treatment on fungal growth of cherry after 9 and 35 days of storage under ambient and refrigerated conditions.

Effect of radiation processing on retention of dried apricot after 18 months of ambient storage.

Radioactive Consumer Products

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Photo by Karen Sheehan

Dentures

• Uranium is added to false teeth to provide a shine to the material (about 10% of the teeth)
• Concentration of uranium is quite low – about 300 parts per million

Radiation Detection Instruments

Geiger Counter

Liquid Scintillation Counter

Photo by Karen Sheehan

Photo by Carl Tarantino

Annual Radiation Dose Limits�General Public vs. Occupational

Established by the

Nuclear Regulatory Commission

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• General Public Limit - 100 mrem

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• Occupational Limit - 5,000 mrem

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Remember – We get approximately 300 mrem per year from natural background exposure.

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For more information about radiation you may contact the Health Physics Society.

Health Physics Society

Specialists in Radiation Safety

http://www.HPS.org

Additional References

• Hall E. Radiation and life, 2^nd ed. New York: Pergamon Press; 1984.

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• Bushong SC. Radiologic science for technologists, 7^th ed. St Louis, MO: Mosby, Inc.; 2001.