Human Impacts • Radiation • Nuclear Accidents • Invisible Environmental Hazards
Updated:
Radiation and nuclear hazards are among the most difficult environmental risks to understand because they are usually invisible. Radioactive material can move through air, water, soil, sediment, food chains, forests, oceans, buildings and waste systems without producing an obvious color, smell or physical warning.
A nuclear hazard may begin with a reactor accident, damaged fuel, failed cooling system, lost medical source, radioactive-waste leak, nuclear test, contaminated firefighting response, uranium-processing failure or unexplained isotope detection. The original event may last minutes, but contamination, monitoring, waste management and land-use restrictions can continue for years or decades.
This main pillar explains the complete radiation and nuclear-hazard system: what ionizing radiation is, how radioactive isotopes decay, how exposure is measured, how reactor accidents develop, how radioactive material spreads, why atmospheric fallout differs from environmental contamination and why nuclear waste can remain dangerous longer than the infrastructure designed to contain it.
Radiation and Nuclear Hazards: Key Points
- Radiation is energy emitted by atoms, particles or electromagnetic processes.
- Radioactivity is the spontaneous decay of unstable atomic nuclei.
- Radioactive contamination is radioactive material present where it should not be.
- Exposure means a person or organism receives ionizing radiation.
- The key questions are: Which isotope? What concentration? Which exposure pathway? What dose? For how long?
- Radioactive material can move through air, fallout, rain, snow, groundwater, rivers, oceans, sediment, dust, smoke and food chains.
- Reactor accidents may involve cooling failure, fuel damage, hydrogen explosions, fire, containment failure and radioactive release.
- Nuclear fallout is atmospheric deposition; radioactive contamination is the broader presence of radioactive material in environmental or human systems.
- Nuclear waste is difficult to manage because some radionuclides remain hazardous longer than ordinary tanks, buildings and political systems last.
- This main pillar owns broad radiation, reactor-safety and nuclear-hazard stories.
- Narrowly focused stories belong in the dedicated contamination, fallout or radioactive-waste child pillar.
What Are Radiation and Nuclear Hazards?
A radiation hazard exists when ionizing radiation or radioactive material creates a pathway capable of exposing people, wildlife, ecosystems or infrastructure.
A nuclear hazard may involve:
- Reactor accidents
- Damaged nuclear fuel
- Loss of cooling
- Radioactive contamination
- Atmospheric fallout
- Spent nuclear fuel
- Radioactive-waste leaks
- Lost radioactive sources
- Uranium processing
- Nuclear-fuel transport
- Weapons-test legacy zones
- Radiological emergencies
Not every radiation detection represents an emergency. Sensitive instruments can measure radioactive material at concentrations far below levels expected to cause immediate harm.
Reliable reporting therefore requires more than the word “radiation.” It requires information about:
- The radionuclide
- The measured activity
- The radiation type
- The exposure duration
- The environmental medium
- The pathway to people or ecosystems
- The resulting dose
Radiation and Nuclear-Hazards Cluster
This page is the main pillar for radiation physics, reactor hazards, broad nuclear-safety questions and events involving several overlapping mechanisms.
Three specialist child pillars consolidate narrower legacy archives.
Radioactive Contamination Explained
Radioactive material spreading through water, groundwater, soil, sediment, buildings, food, seafood, forests, farms and human surroundings.
Primary topics:
- Radioactive water
- Tritium leaks
- Contaminated groundwater
- Cesium in soil and sediment
- Radioactive food and seafood
- Lost radioactive sources
- Exclusion zones
- Environmental recovery
Nuclear Fallout Explained
Radioactive material transported through the atmosphere and deposited by dry fallout, rain or snow.
Primary topics:
- Radioactive plumes
- Atmospheric transport
- Rainout and snowout
- Nuclear-test fallout
- Fallout maps
- Iodine-131 deposition
- Cross-border radiation clouds
- Wildfire resuspension
Radioactive Waste & Storage Explained
The creation, containment, transport, leakage and long-term disposal of nuclear and radioactive waste.
Primary topics:
- Spent nuclear fuel
- Cooling pools
- Dry-cask storage
- Waste drums and tanks
- Deep geological repositories
- Leaking storage systems
- Military nuclear waste
- Long-term disposal
| Dominant subject | Best destination |
|---|---|
| Broad radiation, reactor safety or mixed nuclear-hazard story | Radiation & Nuclear Hazards Explained |
| Radioactive material in water, soil, sediment, food or buildings | Radioactive Contamination Explained |
| Radioactive cloud, plume, atmospheric transport or deposition | Nuclear Fallout Explained |
| Spent fuel, waste tanks, drums, repositories or storage failure | Radioactive Waste & Storage Explained |
Radiation, Radioactivity, Contamination and Exposure
These terms are related but do not mean the same thing.
| Term | Meaning | Example |
|---|---|---|
| Radiation | Energy travelling as particles or electromagnetic waves | Gamma rays emitted by cesium-137 |
| Radioactivity | The spontaneous decay of unstable atomic nuclei | Iodine-131 decaying into a more stable form |
| Radioactive material | A substance containing unstable atoms | Tritium-contaminated water |
| Contamination | Radioactive material present where it should not be | Cesium-bearing dust on soil or buildings |
| Exposure | Receiving radiation from an internal or external source | Standing near contaminated equipment |
| Dose | The amount of radiation energy absorbed and its biological significance | A measured dose expressed in gray or sievert |
What Is Ionizing Radiation?
Ionizing radiation carries enough energy to remove electrons from atoms or molecules. This process creates ions and can alter chemical bonds in biological tissue.
Ionizing radiation includes:
- Alpha particles
- Beta particles
- Gamma rays
- X-rays
- Neutrons
Non-ionizing radiation—including visible light, radio waves and most microwaves—does not have enough energy per photon to ionize atoms in the same way.
Why Ionization Matters
Ionization can damage cells directly or create chemically reactive molecules that affect DNA, proteins and cell membranes.
The biological consequence depends on:
- Radiation type
- Dose
- Dose rate
- Exposed tissue
- Exposure duration
- Whether exposure is internal or external
Alpha, Beta, Gamma and Neutron Radiation
Alpha Radiation
Alpha particles consist of two protons and two neutrons. They travel only short distances and are stopped by paper or the outer layer of skin.
Alpha-emitting material can become hazardous when inhaled, swallowed or introduced through a wound.
Examples: plutonium-239, americium-241 and radon-decay products.
Beta Radiation
Beta particles are high-energy electrons or positrons emitted during radioactive decay.
They penetrate farther than alpha particles and may create both external skin exposure and internal exposure.
Examples: tritium, strontium-90 and carbon-14.
Gamma Radiation
Gamma rays are highly penetrating electromagnetic radiation emitted from atomic nuclei.
Dense materials such as lead, steel or thick concrete are commonly used for shielding.
Examples: cesium-137 and cobalt-60.
Neutron Radiation
Neutron radiation occurs mainly around active reactors, criticality events, particle accelerators and nuclear detonations.
Neutrons are highly penetrating and may make other materials radioactive through neutron activation.
Radioactive Isotopes: The Real Characters in Nuclear-Hazard Stories
An isotope is a form of an element with a particular number of neutrons. Some isotopes are stable, while others decay and emit radiation.
| Radionuclide | Why it matters | Common context |
|---|---|---|
| Iodine-131 | Short-lived but important after a fresh release because iodine can concentrate in the thyroid | Reactor accidents, fresh fallout, milk and food monitoring |
| Cesium-137 | Long-lived, mobile in some environments and strongly associated with fallout, soil and food-chain monitoring | Chernobyl, Fukushima, lake sediment, forests and crops |
| Strontium-90 | Chemically resembles calcium and may enter bones and food systems | Fallout, contaminated water, milk and environmental monitoring |
| Tritium | A radioactive form of hydrogen that can become part of water molecules | Nuclear-plant discharges, wastewater and groundwater leaks |
| Cobalt-60 | A strong gamma emitter used in medicine and industry | Lost sources, industrial accidents and medical equipment |
| Plutonium-239 | A long-lived alpha emitter associated with nuclear fuel, waste and weapons programs | Waste sites, test sites, fuel processing and contaminated particles |
| Americium-241 | A long-lived alpha and gamma emitter produced through plutonium decay | Waste, industrial sources and weapons-test legacy sites |
| Ruthenium-106 | A fission product that can reveal a release through atmospheric monitoring | Cross-border detection events and source investigations |
Why the Isotope Matters
Different radionuclides behave differently in air, water, soil and the human body.
The relevant questions include:
- Is the isotope volatile?
- Does it dissolve in water?
- Does it bind to soil or sediment?
- Can plants or animals absorb it?
- Which type of radiation does it emit?
- How long is its half-life?
Half-Life and Environmental Persistence
A radionuclide’s half-life is the time required for half of its radioactive atoms to decay.
After one half-life, half remains. After two half-lives, one quarter remains. After three, one eighth remains.
Short-Lived Radionuclides
Short-lived radionuclides may dominate immediate emergency decisions but decline relatively quickly.
Iodine-131, for example, has a half-life of about eight days and is most important soon after a fresh release.
Long-Lived Radionuclides
Long-lived radionuclides can affect soil, forests, sediment, waste management and land-use decisions for decades or far longer.
Cesium-137 has a half-life of approximately 30 years. Plutonium-239 has a half-life measured in thousands of years.
Half-Life Is Not the Same as Risk
Risk also depends on:
- Initial quantity
- Radiation type
- Chemical form
- Environmental mobility
- Exposure route
- Biological retention
- Shielding and distance
Radiation Dose and Exposure
Radiation detection and radiation dose are related but not identical. Instruments may detect radioactive material without showing that a person received a dangerous dose.
Activity
Radioactivity is commonly measured in becquerels, representing nuclear decays per second.
Absorbed Dose
Absorbed dose is measured in gray and describes the radiation energy deposited per unit mass.
Equivalent and Effective Dose
The sievert accounts for radiation type and, for effective dose, the sensitivity of exposed tissues.
Dose Rate
Dose rate describes how quickly a dose is received. The same total dose delivered over seconds may have different biological consequences from a dose spread over months or years.
Exposure Pathways
- External gamma radiation
- Radioactive particles on skin or clothing
- Inhalation of contaminated dust
- Ingestion of contaminated food or water
- Medical or occupational exposure
Distance, Time and Shielding
Radiation protection frequently relies on three basic principles:
- Reduce time near the source
- Increase distance from the source
- Use appropriate shielding
Natural and Human-Made Radiation
Radiation is a natural part of the environment. Human activity can nevertheless create concentrated sources, new exposure pathways and contamination zones.
Natural Background Radiation
- Cosmic radiation
- Radon gas
- Uranium and thorium in rock
- Potassium-40 in food and bodies
- Natural radionuclides in soil and water
Human-Made Sources
- Medical imaging and treatment
- Nuclear power
- Nuclear weapons testing
- Industrial radiography
- Research reactors
- Radioactive tracers
- Nuclear-fuel processing
Radon
Radon is a naturally occurring radioactive gas produced by uranium decay in rock and soil. It can accumulate in buildings and represents a different hazard pathway from reactor accidents or fallout.
Technologically Enhanced Natural Radioactivity
Mining, oil and gas production, phosphate processing and industrial activity can concentrate naturally occurring radioactive material into waste, scales, sludge or tailings.
How Nuclear Reactors Work
A nuclear reactor uses controlled fission to release heat. That heat produces steam or another working fluid that drives turbines and generates electricity.
Nuclear Fission
In fission, a heavy atomic nucleus splits into smaller nuclei and releases energy and neutrons.
Chain Reaction
Released neutrons can trigger additional fission events. Control rods absorb neutrons and regulate the reaction.
Fuel
Commercial reactor fuel commonly contains uranium formed into pellets and sealed inside metal fuel rods.
Coolant
Coolant removes heat from the reactor core. Loss of coolant can expose or overheat fuel.
Containment
Containment structures are designed to limit radioactive releases during accidents.
Decay Heat
Even after a reactor shuts down, radioactive decay continues generating heat. Cooling must continue until decay heat falls sufficiently.
How Nuclear Reactor Accidents Happen
Severe reactor accidents usually develop through a chain of failures rather than one isolated problem.
Loss of Coolant
A pipe break, valve failure or system malfunction can reduce cooling around nuclear fuel.
Station Blackout
A station blackout occurs when a plant loses both offsite electricity and emergency power needed for pumps, instruments and control systems.
Fuel Overheating
Without sufficient cooling, fuel temperatures rise. Fuel cladding can fail and release fission products.
Core Damage and Meltdown
At high temperatures, fuel and reactor materials may melt and relocate within or below the reactor vessel.
Hydrogen Generation
High-temperature reactions involving fuel cladding and steam can produce hydrogen, creating an explosion risk.
Containment Failure or Venting
Pressure may force operators to vent gases, or damaged containment may allow radioactive material to escape.
Spent-Fuel Pool Hazards
Used fuel remains radioactive and generates heat. Loss of water or cooling can create serious radiation and fuel-damage concerns.
Major Nuclear and Radiological Hazards
Reactor Accidents
Cooling failure, fuel damage, fire, explosion or containment failure can release radioactive material.
Radioactive Contamination
Radioactive material enters water, soil, food, buildings or living systems.
Nuclear Fallout
Radioactive material is transported through the atmosphere and deposited onto land or water.
Radioactive Waste
Spent fuel and contaminated materials require secure management over long periods.
Lost Sources
Medical or industrial sources may be abandoned, stolen, misplaced or accidentally recycled.
Criticality Accidents
An uncontrolled nuclear chain reaction can expose workers to intense neutron and gamma radiation.
Transport Accidents
Radioactive materials are transported by road, rail, ship and air, creating packaging and accident risks.
Uranium-Mining Hazards
Mining and milling can create radioactive tailings, contaminated dust, radon and polluted water.
How Radioactive Material Moves Through Earth Systems
Radioactive contamination is often imagined as a single cloud. In reality, it may move through slow and ordinary environmental pathways.
Atmospheric Transport
Gases and particles can travel in plumes before being deposited by gravity, rain or snow.
Groundwater
Leaking tanks, pipes and waste sites can release radionuclides into aquifers and fractured rock.
Rivers and Lakes
Water transports dissolved radionuclides and contaminated sediment downstream.
Ocean Currents
Marine releases can disperse, dilute, settle into sediment or enter coastal ecosystems.
Soil and Sediment
Radionuclides may bind to mineral particles and remain stored in soils, riverbeds, reservoirs or seafloor sediment.
Food Chains
Plants, animals, fungi and aquatic organisms can absorb radionuclides and create exposure through food.
Fire and Smoke
Wildfires can disturb contaminated vegetation and soil, resuspending particles into the atmosphere.
Flooding and Erosion
Floods can redistribute contaminated soil, sediment and waste across new areas.
Radioactive Contamination
Radioactive contamination means radioactive material has entered an unwanted location.
It can affect:
- Drinking water
- Groundwater
- Rivers and lakes
- Ocean water and sediment
- Agricultural soil
- Forests
- Food and animal feed
- Buildings and equipment
- Human skin, clothing or tissue
Contamination may result from an accident, leak, atmospheric deposition, lost source, waste failure, mining operation or cleanup disturbance.
The specialist guide covers Fukushima water, tritium leaks, radioactive groundwater, contaminated forests, food-chain detections, lost sources and environmental recovery.
Nuclear Fallout
Nuclear fallout is radioactive material deposited from the atmosphere following a nuclear explosion, reactor fire, severe accident or airborne release.
Local Fallout
Larger particles may settle relatively close to the source.
Regional and Long-Range Fallout
Smaller particles and gases can travel across countries or continents.
Dry Deposition
Particles and gases settle without precipitation.
Rainout and Snowout
Rain and snow can remove radionuclides from a plume and create concentrated deposition zones.
Resuspension
Previously deposited radionuclides can return to the atmosphere through fire, wind, farming, construction or erosion.
The specialist guide covers fallout plumes, deposition maps, iodine-131, cesium-137, nuclear testing, radioactive rain and cross-border detection events.
Radioactive Waste and Long-Term Storage
Radioactive waste includes spent nuclear fuel, contaminated equipment, reactor materials, processing waste, medical sources and waste from research or weapons programs.
Low-Level Waste
Low-level waste may include clothing, filters, tools and contaminated laboratory materials.
Intermediate-Level Waste
Intermediate waste may contain resins, chemical sludge and reactor components requiring shielding.
High-Level Waste
High-level waste includes highly radioactive reprocessing waste and spent nuclear fuel.
Spent Fuel Pools
Newly removed fuel is stored underwater for cooling and radiation shielding.
Dry-Cask Storage
Older spent fuel may be transferred into sealed metal and concrete containers.
Deep Geological Repositories
Repositories aim to isolate high-level waste in stable rock formations for extremely long periods.
The Timescale Problem
Some nuclear waste remains hazardous longer than ordinary buildings, governments and institutions are expected to survive.
The specialist guide covers Hanford, WIPP, Runit Dome, waste tanks, repositories, dry casks, spent fuel and leaking containment systems.
Lost, Stolen and Abandoned Radioactive Sources
Radioactive sources are used in medicine, construction, industry, mining, research and agriculture.
A source may become hazardous when it is:
- Abandoned
- Stolen
- Misplaced
- Improperly discarded
- Damaged
- Mixed with scrap metal
- Opened by an untrained person
Orphan Sources
An orphan source is a radioactive source no longer under regulatory control.
Scrap-Metal Contamination
A source entering recycling systems can contaminate scrapyards, furnaces, vehicles, buildings and manufactured metal.
Goiânia
The 1987 Goiânia accident demonstrated how a small abandoned medical source could contaminate homes, objects, people and an urban neighborhood.
Lost Industrial Capsules
Industrial gauges and capsules may contain powerful radioactive sources. Their small size can make recovery difficult across long transport routes.
Earth Systems and Nuclear Risk
Nuclear facilities are human-built systems, but they exist inside landscapes shaped by geology, water, climate and natural hazards.
Earthquakes
Strong ground motion can damage buildings, pipes, electrical systems, tanks and cooling infrastructure.
Tsunamis and Storm Surge
Coastal flooding can disable backup power, pumps and emergency equipment.
River Flooding
Floodwater may affect reactors, waste facilities, contaminated land and access routes.
Wildfires
Fire can threaten infrastructure and resuspend radionuclides from contaminated forests or soil.
Drought and Heat
High temperatures and reduced river flow may affect cooling-water availability and reactor operations.
Coastal Erosion
Erosion and sea-level change can threaten legacy waste sites and contaminated coastal infrastructure.
Groundwater
Subsurface flow can carry contaminants beyond property boundaries and complicate cleanup.
Time
Corrosion, institutional change and infrastructure aging can turn temporary storage into a long-term vulnerability.
Radiation Monitoring and Detection
Many nuclear-hazard stories begin with a measurement rather than a visible event.
Radiation Survey Meters
Portable instruments measure radiation near people, objects, buildings and contaminated ground.
Dosimeters
Dosimeters record accumulated exposure for workers or emergency personnel.
Air Monitoring
Air filters and monitoring stations can detect radionuclides transported in atmospheric plumes.
Water Sampling
Laboratories analyze drinking water, groundwater, rivers, lakes and seawater for specific radionuclides.
Soil and Sediment Sampling
Samples can reveal deposition patterns and long-term environmental storage.
Food Monitoring
Milk, crops, meat, fish, mushrooms, honey and other foods may be tested after releases or in known contamination zones.
Gamma Spectrometry
Gamma spectroscopy identifies radionuclides based on characteristic gamma energies.
Whole-Body Counting
Specialized instruments can estimate certain radionuclides inside the body.
Questions That Matter
- Which radionuclide was measured?
- What was the concentration or activity?
- Which medium was tested?
- Was the result above background?
- Was it a single result or persistent trend?
- What dose could result?
- Was the source identified?
Emergency Zones, Evacuation and Protective Actions
Protective actions depend on the type and scale of the release.
Sheltering
Remaining indoors can reduce exposure to an airborne plume and deposited particles.
Evacuation
Evacuation may be ordered when projected exposure exceeds emergency thresholds or critical infrastructure is threatened.
Food and Water Restrictions
Authorities may restrict milk, crops, livestock, seafood, drinking water or forest products.
Potassium Iodide
Potassium iodide can reduce thyroid uptake of radioactive iodine when taken at the correct time and under official guidance. It does not protect against other radionuclides or external radiation.
Decontamination
Removing outer clothing, washing exposed skin and controlling contaminated materials can reduce external contamination.
Exclusion Zones
Long-term exclusion zones may be established where contamination makes ordinary residence, farming or infrastructure use difficult.
Communication
Poor communication can amplify fear, while overly reassuring communication can damage trust. Effective communication should distinguish detection, contamination, exposure and dose.
Major Nuclear and Radiological Events
These benchmark events illustrate different nuclear-hazard mechanisms. The main pillar provides the overview; detailed contamination, fallout and waste material belongs in the specialist pages.
| Event | Year | Location | Main mechanism | Primary destination |
|---|---|---|---|---|
| Kyshtym / Mayak | 1957 | Soviet Union | Radioactive-waste tank explosion and regional contamination | Radioactive waste |
| Windscale Fire | 1957 | United Kingdom | Reactor fire, atmospheric release and food restrictions | Nuclear fallout |
| Three Mile Island | 1979 | United States | Partial core meltdown and reactor-safety failure | Main pillar |
| Chernobyl | 1986 | Ukraine / Soviet Union | Reactor explosion, graphite fire and widespread fallout | Nuclear fallout |
| Goiânia | 1987 | Brazil | Abandoned cesium-137 medical source | Radioactive contamination |
| Tokaimura | 1999 | Japan | Criticality accident during uranium processing | Main pillar |
| Fukushima Daiichi | 2011 | Japan | Earthquake, tsunami, station blackout, meltdowns and contaminated water | Radioactive contamination |
| WIPP Release | 2014 | United States | Underground radioactive-waste drum failure | Radioactive waste |
| Runit Dome | Legacy | Marshall Islands | Nuclear-test waste under aging coastal containment | Radioactive waste |
The INES Scale
The International Nuclear and Radiological Event Scale ranks events from Level 0 to Level 7.
- Levels 1–3: incidents
- Levels 4–7: accidents
INES is useful for public communication but does not capture every aspect of long-term contamination, waste management or environmental recovery.
How Legacy Radiation and Nuclear Articles Should Be Classified
Classify each legacy article according to its dominant hazard mechanism—not merely the word “nuclear” in the headline.
Redirect to Radiation & Nuclear Hazards Explained When:
- The article explains radiation generally
- Reactor safety is the central subject
- A nuclear accident involves several mechanisms
- The INES scale is discussed
- The article ranks nuclear accidents
- A map shows reactors near faults or hazards
- Radiation exposure and dose dominate
- The story does not fit one specialist child pillar
Redirect to Radioactive Contamination When:
- Radioactive water is central
- Tritium leaks into groundwater
- Cesium is detected in soil or sediment
- Food, seafood or crops are contaminated
- A lost source contaminates buildings or objects
- Environmental cleanup or exclusion zones dominate
- Fukushima water and food monitoring are central
Redirect to Nuclear Fallout When:
- A radioactive plume is central
- Fallout maps dominate
- Rainout or snowout is discussed
- Nuclear-test fallout is involved
- Iodine-131 deposition is central
- A radiation cloud crosses national borders
- Wildfire smoke resuspends fallout
- Chernobyl atmospheric transport dominates
Redirect to Radioactive Waste & Storage When:
- Spent nuclear fuel is central
- Waste tanks or drums leak
- A repository is discussed
- Dry-cask storage dominates
- Buried nuclear waste is involved
- Hanford, WIPP or Runit Dome is central
- Nuclear-waste transport or disposal dominates
Radiation and Nuclear-Hazards Glossary
- Activity
- The rate at which radioactive atoms decay, commonly measured in becquerels.
- Alpha particle
- A heavy charged particle consisting of two protons and two neutrons.
- Becquerel
- A unit representing one radioactive decay per second.
- Beta particle
- A high-energy electron or positron emitted during radioactive decay.
- Contamination
- Radioactive material present where it should not be.
- Criticality
- A state in which a nuclear chain reaction becomes self-sustaining.
- Decay heat
- Heat produced by radioactive decay after a reactor has shut down.
- Decommissioning
- The process of shutting down, dismantling, decontaminating and managing a nuclear facility after operation.
- Dose
- A measure of radiation energy absorbed and its potential biological effect.
- Fallout
- Radioactive material deposited from the atmosphere after an airborne release.
- Gamma ray
- Highly penetrating electromagnetic radiation emitted during nuclear processes.
- Gray
- The unit of absorbed radiation dose.
- Half-life
- The time required for half the radioactive atoms in a sample to decay.
- Ionizing radiation
- Radiation energetic enough to remove electrons from atoms or molecules.
- Isotope
- A form of an element with a particular number of neutrons.
- Radionuclide
- A radioactive isotope.
- Radioactivity
- The spontaneous decay of unstable atomic nuclei.
- Resuspension
- The return of previously deposited radioactive particles to the air through wind, fire or disturbance.
- Sievert
- A unit used to describe radiation dose adjusted for biological effect.
- Spent nuclear fuel
- Used reactor fuel that remains highly radioactive and produces heat.
Frequently Asked Questions
What is radiation?
Radiation is energy travelling through space or matter as particles or electromagnetic waves. Ionizing radiation has enough energy to remove electrons from atoms.
What is the difference between radiation and radioactivity?
Radiation is the energy emitted. Radioactivity is the process through which unstable atomic nuclei decay and release radiation.
What is radioactive contamination?
Radioactive contamination is the unwanted presence of radioactive material in air, water, soil, food, buildings, equipment or living organisms.
Is all radiation dangerous?
No. Risk depends on radiation type, dose, dose rate, duration, exposed tissue and whether radioactive material remains outside the body or enters through inhalation or ingestion.
What is the difference between contamination and exposure?
Contamination means radioactive material is physically present. Exposure means a person or organism receives radiation. Exposure can occur without contamination, and contamination can create continuing exposure.
What is nuclear fallout?
Nuclear fallout is radioactive material deposited from the atmosphere after a nuclear explosion, reactor fire, severe accident or airborne release.
Why is nuclear waste difficult to manage?
Some radionuclides remain hazardous for longer than ordinary tanks, buildings, institutions and political systems are expected to survive.
What causes a nuclear reactor meltdown?
A meltdown occurs when nuclear fuel overheats and is damaged or melts, usually after cooling failure, loss of power or severe disruption of reactor systems.
Why are Fukushima and Chernobyl different?
Chernobyl involved a reactor explosion, graphite fire and major atmospheric fallout. Fukushima followed an earthquake, tsunami, station blackout and reactor meltdowns, with long-term contaminated-water and decommissioning challenges.
Can radioactive contamination enter food?
Yes. Radionuclides can enter crops, milk, livestock, fish, shellfish, mushrooms, honey and other foods through contaminated soil, water, fallout or animal feed.
Does detecting radiation mean there is an emergency?
Not necessarily. Sensitive instruments can detect very small quantities. The isotope, concentration, pathway and resulting dose determine the significance of the measurement.
What is the INES scale?
The International Nuclear and Radiological Event Scale classifies nuclear and radiological events from Level 0 to Level 7 according to their safety significance.
