Radiation Physics Chapter 3

Radiation Physics (46351) & Radiation and Environment (42341)

• Chapter 3: Radioactivity Sources and Decay Chains
• Course Instructor: Prof. Dr. Khalil Thabayneh
• University: Hebron University, Palestine

Introduction

• Earth's environment contains Natural Occurring Radioactive Materials (NORMs) spread in various geological formations (water, rocks, air).
• Food, air and buildings also contain radioactive elements and radionuclides.
• Background levels of radioactivity are generally not harmful to humans or other living things.
• Human-made activities involving radionuclides can cause environmental effects.
• All species on Earth have evolved in environments with natural background radiation.

Where Does Radiation Come From?

• Over 80% of radiation exposure comes from natural sources (cosmic, soil, radon).
• Only about 20% of exposure is from human-made sources, primarily used in medicine.
• Radiation can irradiate the human body externally (from outside the body) or internally (from inside the body, after inhaling, swallowing or absorbing).

Worldwide Distribution of Radiation Exposure

• Radon (42%)
• Cosmic (13%)
• Soil (16%)
• Food (9%)
• Artificial (20%)
• Medical (20%)

Natural Sources Introduction

• Earth's environment has been exposed to radiation since its creation, from outer space and its crust & core.
• There's no way to avoid natural radiation sources.
• Global average effective dose per person is about 2.4 mSv, ranging from 1 to 10+ mSv depending on location.
• Buildings can trap radon gas or contain radionuclides, increasing radiation exposure.

Cosmogenic Radiation

• Cosmic rays (protons and heavier nuclei) originate in outer space.
• They strike the atmosphere, forming a nuclear cascade.
• Most particles are stopped before reaching the Earth's surface, except for energetic muons and neutrons.
• Cosmogenic radionuclides include 22Na, 7Be, and 14C, formed in the atmosphere.
• 14C has a half-life of 5,730 years.
• 81Kr has a half-life of 210,000 years.

Cosmogenic Radiation (Continued)

• Most cosmic rays originate in deep space or released during solar flares.
• The Earth's atmosphere and magnetic field shield the Earth from cosmic radiation to varying extents.
• Higher altitudes expose humans to more cosmic radiation.
• People at high altitudes receive more cosmic radiation than those at sea level.

Terrestrial Radiation (NORMs)

• Terrestrial NORM comes from earth's mantle and crust.
• Humans exploring the earth increase exposure to radiation.
• Important NORM natural radionuclides include 232Th, 238U, 235U, and 40K.
• These elements have been decaying for a long time.
• NORM in the earth's crust has long half-lives.
• NORM (Thorium and Uranium) decay chains produce significant nuclides.
• Radionuclides in nature are close to a state of secular equilibrium, with equal activities in each chain.

UNSCEAR, Terrestrial Sources and Exposure

• UNSCEAR estimates annual average external exposure from terrestrial sources at about 0.48 mSv.
• Exposure varies geographically.
• Some regions have higher NORM concentrations (e.g., Kerala, India).
• The average annual radiation dose for outdoor areas in many countries is between 0.3 and 0.6 mSv.

Radon: Properties & Risks

• Radon-222 is a radioactive, gaseous element in the uranium decay chain (from 226Ra).
• It has a relatively short half-life (3.82 days).
• Radon-222 is a leading cause of lung cancer.
• Its gaseous nature allows it to permeate soil, rocks, and buildings.
• It concentrates in buildings and uranium mines.

Radon: Inhalation Risks & Distribution

• Inhaled radon and its short-lived decay products (218Po and 214Po) are retained in the lungs.
• They irradiate lung tissue with alpha particles.
• Radon is a major cause of lung cancer, particularly in smokers (due to synergistic effects).
• Radon is highly concentrated in buildings, especially basements.
• Indoor radon concentrations vary geographically.

Radon: Workplace Exposure

• Radon gas in underground mines poses significant occupational exposure.
• The annual average effective radiation dose for miners is about 2.4 mSv for coal miners and 3 mSv for other miners in this sector.

Internal Exposure

• Internal exposure occurs when radioactive materials are inhaled, ingested (eaten), or absorbed through the skin.
• Alpha and beta particles are unlikely to cause internal exposure (usually external).
• Internal radiation dose depends on the amount of material, its location in the body, how long it remains, and the type of radiation.
• Food and water can contain radionuclides from natural sources.

Artificial Radioactivity

• Humanity has been exposed to artificial radiation sources for about a century.
• These sources are generally beneficial (medicine, power generation, scientific research).
• Industries (nuclear weapons production, nuclear tests, radioactive leaks) often have some degree of negative impact.
• Individual doses from artificial radiation vary significantly.

Medical Applications of Radiation

• In medicine, radiation is used for diagnosis and treatment (e.g., X-rays, CT scans, nuclear medicine).
• Medical use is by far the largest source of artificial radiation exposure.
• Accounts for approximately 20% of worldwide population exposure.
• Medical radiation exposure is concentrated in industrialized countries.

Radioactive Exposure in Workplaces

• Exposure doses from workplaces in the nuclear industry are typically higher, particularly in uranium mining.

Accidents in Medical Applications

• Human error is the major contributor to radiation accidents.
• Errors can include giving wrong doses, improper use of equipment, or exposing the incorrect patient.
• Quality assurance programs help mitigate the risk of these accidents.

Accidents at Nuclear Facilities

• Nuclear accidents can lead to significant exposures (e.g., Chernobyl, Fukushima).
• These accidents result in widespread contamination and long-term health impacts.

Nuclear Weapons Exposure

• Nuclear weapons testing releases radioactive materials into the atmosphere.
• The highest exposure is usually short-lived and localized.
• Current levels of exposure from nuclear weapons testing are very low.

Nuclear Reactors

• Nuclear fission in reactors can produce electricity, but also generates radioactive waste including radionuclides.

Nuclear Power Plants

• Global nuclear power generation has increased significantly since their initial development.
• The normal operation of nuclear power plants has a limited effect on worldwide radiation.

Industrial and Other Applications

• Industrial uses of radiation sources (e.g. irradiation, radiography, measurement devices) generally pose low exposure risk.

Naturally Occurring Radioactive Materials

• NORM in industrial products and waste can increase public exposure.
• Mining and processing of ores can increase NORM levels.

Geothermal Energy

• Geothermal energy generation can also cause radiation exposure.
• Depleted uranium, a by-product of enrichment, is used for shielding, counterweights, and munitions.

Consumer Products

• Some consumer products (e.g., luminous clocks, smoke detectors) contain radionuclides.
• The use of specific radionuclides in consumer products has declined, with radium replaced by alternatives.

Average Radiation Exposure

• Natural sources of radiation are the source of most public exposure (air, food, drink).
• Medical uses are the greatest source of artificial sources from any single activity.

Explore the fundamentals of natural and human-made radioactivity sources and decay chains in Chapter 3 of the Radiation Physics course. This quiz covers key concepts about radioactive elements found in the environment and their effects on living organisms. Test your knowledge on the origins of radiation exposure and its implications.