Applications and Safety
2. Industrial and Scientific Applications
Learning outcomes
- I can identify industrial uses of radiation.
- I can explain how radiation is used in quality control.
- I can describe how radioactive tracers are used.
- I can explain the role of radiation in scientific research.
- I can identify everyday applications of radioactive materials.
Industrial and Scientific Applications of Radiation
Radioactive materials and ionizing radiation are used in many areas outside medicine. They are valuable because radiation can be detected very sensitively, can pass through materials, can ionize matter, and radioactive isotopes can be followed as they move through complex systems.
Important applications include:
- industrial quality control
- thickness and level monitoring
- detecting leaks and blockages
- industrial radiography
- sterilization
- radioactive tracers
- scientific research
- environmental studies
- smoke detectors
- space exploration
The type of radiation and isotope used depends on the job being performed.
Why Radiation Is Useful in Industry
Radiation has several properties that make it useful for industrial applications.
It can:
- penetrate materials
- be detected without direct contact
- provide continuous measurements
- reveal hidden defects
- trace the movement of substances
- sterilize materials
- operate in harsh environments
- provide information without destroying the object being tested
Many radiation-based techniques are examples of:
non-destructive testing
This means an object can be inspected without cutting it apart or significantly damaging it.
Choosing the Type of Radiation
Different types of radiation have different penetrating powers.
Alpha radiation
- very strongly ionizing
- very short range
- stopped easily
- useful in some specialized applications
Beta radiation
- moderate penetrating ability
- can pass through thin materials
- useful for measuring the thickness of paper, plastic and thin metal sheets
Gamma radiation
- highly penetrating
- can pass through relatively thick materials
- useful for industrial radiography, level monitoring, tracers and sterilization
The radiation must have the right penetrating ability for the application.
Thickness Monitoring
One important industrial application is measuring the thickness of continuously manufactured materials.
Examples include:
- paper
- plastic film
- aluminium foil
- thin metal sheet
A radioactive source is placed on one side of the material.
A detector is placed on the other.
The basic arrangement is:
radioactive source → material → detector
Some of the radiation is absorbed by the material.
The detector measures the radiation that passes through.
How a Thickness Gauge Works
Suppose beta radiation is used.
If the material becomes:
too thick
more beta radiation is absorbed.
Therefore:
detector count rate decreases
If the material becomes:
too thin
less beta radiation is absorbed.
Therefore:
detector count rate increases
A control system can use this information to adjust the manufacturing machinery.
Automatic Quality Control
Imagine a factory producing paper.
The target thickness must remain constant.
If the detector count becomes too low:
paper too thick → rollers adjust to reduce thickness
If the detector count becomes too high:
paper too thin → rollers adjust to increase thickness
This creates a:
feedback control system
Radiation therefore allows continuous automatic quality control during manufacturing.
Why Beta Radiation Is Useful for Thin Materials
Alpha radiation would usually be unsuitable because it is absorbed too easily.
Gamma radiation may be too penetrating for very thin materials, so the difference between slightly thicker and thinner material may be less pronounced.
Beta radiation often provides a useful balance for thin sheets:
some passes through + some is absorbed
This makes changes in thickness easier to detect.
Gamma Radiation for Thicker Materials
For thicker materials, more penetrating radiation may be required.
Gamma radiation can pass through thicker materials than beta radiation.
Therefore, the radiation type is selected according to:
- material
- thickness
- density
- required sensitivity
Level Monitoring
Radiation can also be used to monitor the level of material inside a container.
For example, a factory may need to measure the level of:
- liquid
- powder
- grain
- chemicals
- molten material
without opening the container.
A gamma source and detector can be placed on opposite sides of the container.
If material blocks the beam:
more radiation is absorbed
and:
detector reading decreases
If the beam passes through an empty part of the container:
less radiation is absorbed
and:
detector reading increases
Why Radiation Is Useful for Level Monitoring
Radiation gauges do not need to touch the material being measured.
This can be particularly useful when the material is:
- extremely hot
- corrosive
- under high pressure
- hazardous
- inside a sealed container
The source and detector can remain outside the vessel.
Industrial Radiography
Radiation can be used to inspect the inside of solid objects.
This technique is called:
industrial radiography
It works in a similar general way to medical X-ray imaging.
High-energy X-rays or gamma radiation pass through an object.
Different parts of the object absorb different amounts of radiation.
A detector or imaging system records the transmitted radiation.
Finding Hidden Defects
Industrial radiography can reveal:
- cracks
- voids
- poor welds
- air pockets
- internal corrosion
- manufacturing defects
This is particularly useful for inspecting:
- pipelines
- aircraft components
- pressure vessels
- bridges
- structural welds
- machinery
The object does not normally need to be cut open.
Non-Destructive Testing
Industrial radiography is an example of:
non-destructive testing (NDT)
The purpose is to inspect a component while leaving it usable.
This can improve:
- safety
- reliability
- quality control
- maintenance planning
Detecting a hidden crack before a component fails can prevent serious accidents.
Quality Control
Radiation can therefore be used in several forms of industrial quality control.
Examples include:
Thickness control
Checking whether manufactured sheets have the correct thickness.
Level control
Checking the amount of material inside a container.
Radiography
Checking products for internal defects.
Density measurements
Measuring changes in material density.
These systems allow manufacturers to monitor production accurately and continuously.
Radioactive Tracers
A radioactive tracer is a small amount of radioactive material introduced into a system so that its movement can be followed.
The tracer emits radiation.
A detector can locate the tracer even when the substance is:
- inside a pipe
- underground
- inside machinery
- mixed with other substances
Detecting Leaks in Pipes
Suppose an underground pipe is leaking.
Digging up the entire pipeline would be expensive.
Instead, a suitable radioactive tracer can be introduced into the fluid.
Detectors are moved along the route of the pipe.
If tracer escapes through a leak, increased radiation may be detected near that location.
This helps engineers identify:
where the leak is located
so only the necessary section may need investigation or repair.
Finding Blockages
Radioactive tracers can also help locate:
blockages
inside industrial systems.
A tracer is introduced into the moving fluid.
Detectors monitor its movement.
If the tracer:
- slows
- stops
- accumulates
at a particular location, this may indicate a blockage or flow problem.
Measuring Flow
Tracers can be used to investigate:
- flow speed
- mixing
- residence time
- circulation
- movement through complex industrial equipment
For example, detectors placed at different locations can measure how long a tracer takes to travel between two points.
This can provide information about fluid flow.
Choosing a Tracer
A radioactive tracer should be chosen carefully.
An appropriate tracer should:
- behave like the substance being studied
- emit radiation that can be detected
- have an appropriate half-life
- be detectable in very small quantities
- minimize unnecessary environmental or worker exposure
Why Half-Life Matters for Industrial Tracers
Suppose a tracer's half-life is extremely short.
It might decay before the investigation is completed.
If its half-life is extremely long, radioactive material may remain unnecessarily after the investigation.
Therefore, the preferred half-life is generally:
long enough for the experiment but not unnecessarily long.
This is similar to the reasoning used when selecting medical tracers.
Tracers in Environmental Science
Radioactive and isotopic tracers can also help scientists investigate natural systems.
They can be used to study:
- groundwater movement
- sediment transport
- ocean circulation
- nutrient movement
- pollution pathways
- soil processes
Tracing the movement of matter can reveal processes that would otherwise be difficult to observe directly.
Tracers in Biological Research
Radioactive isotopes have played an important role in biological research.
Scientists can incorporate radioactive isotopes into molecules and follow where those molecules travel.
For example, tracers have been used to investigate:
- nutrient absorption
- photosynthesis
- DNA synthesis
- metabolism
- movement of substances through organisms
Radioactive Carbon in Research
Carbon is found in many biological molecules.
Radioactive carbon isotopes can therefore be used to label carbon-containing compounds.
Scientists can follow the radioactive signal to determine where carbon atoms move during biochemical processes.
Radioactive carbon tracers contributed historically to research into processes such as:
photosynthesis and metabolism
Phosphorus-32
Phosphorus is an important component of:
- DNA
- RNA
- ATP
- phospholipids
The radioactive isotope:
phosphorus-32 (³²P)
has therefore been widely used as a tracer in biological and biochemical research.
Its radiation allows researchers to detect where phosphorus-containing molecules are located.
Autoradiography
A technique called:
autoradiography
can be used to visualize the location of radioactive material in a sample.
Radioactively labelled molecules expose a detector or imaging material.
The resulting pattern shows where the radioactive substance was located.
Autoradiography has been important in research involving:
- DNA
- proteins
- cells
- tissues
- plants
Radioactive Isotopes and DNA Research
Radioactive tracers played an important historical role in molecular biology.
Scientists could label different biological molecules using radioactive isotopes.
Because phosphorus occurs in DNA, radioactive phosphorus could be used to track DNA.
Because sulfur occurs in many proteins but not DNA, radioactive sulfur could be used to label proteins in particular experimental contexts.
This helped scientists investigate the roles of DNA and proteins.
Scientific Dating
Radioactive isotopes are also used to determine ages.
Examples include:
- carbon-14 dating
- potassium-based dating
- uranium-lead dating
These methods allow scientists to investigate:
- archaeology
- Earth's geological history
- volcanic events
- ancient climates
- evolution
- the age of rocks and minerals
Radioactive decay therefore provides scientists with natural clocks.
Neutron Activation Analysis
Radiation can also help scientists determine what substances are present in a sample.
One technique is:
neutron activation analysis
A sample is exposed to neutrons.
Some nuclei absorb neutrons and become radioactive.
The radiation emitted can then be analyzed.
Different elements produce characteristic signals.
This can help determine the elemental composition of a sample.
Applications of Neutron Activation Analysis
This technique has been used in fields including:
- archaeology
- geology
- environmental science
- forensic science
- materials research
It can detect extremely small concentrations of some elements.
Sterilization Using Radiation
Ionizing radiation can destroy microorganisms by damaging important biological molecules such as DNA.
Radiation can therefore be used to sterilize certain products.
Examples include some:
- syringes
- surgical gloves
- medical instruments
- dressings
- laboratory equipment
- packaged medical supplies
Why Radiation Sterilization Is Useful
Radiation can penetrate packaging.
Therefore, some products can be:
- manufactured
- sealed in packaging
- irradiated
- supplied sterile
This reduces the chance of contamination after sterilization.
Irradiation Does Not Necessarily Make an Object Radioactive
A common misconception is that exposing an object to radiation automatically makes it radioactive.
For many common irradiation processes using gamma rays, X-rays, or appropriately selected electron beams:
the treated object does not become radioactive.
Radiation passes through the material and deposits energy, but that is different from creating unstable nuclei.
The exact physics depends on the type and energy of the radiation involved.
Food Irradiation
Ionizing radiation can also be used to treat some foods.
Food irradiation can help:
- reduce harmful microorganisms
- control insects
- delay sprouting
- extend shelf life in some products
The radiation damages microorganisms and pests.
Properly performed food irradiation does not mean the food itself becomes radioactive.
Smoke Detectors
One familiar everyday application of radioactive material is the:
ionization smoke detector
Some ionization smoke alarms contain a very small amount of:
americium-241
Americium-241 emits alpha radiation.
The alpha particles ionize air molecules inside the detector.
This allows a small electrical current to flow.
How an Ionization Smoke Detector Works
Under normal conditions:
alpha radiation → ionizes air → small current flows
When smoke enters the chamber:
- smoke particles interfere with the ions
- the electrical current changes
- the circuit detects the change
- the alarm sounds
The radioactive source is small and enclosed within the detector.
Why Alpha Radiation Is Suitable
Alpha radiation is strongly ionizing.
This makes it effective at:
ionizing air
Alpha radiation also has very low penetrating ability.
It is easily stopped by materials in the detector casing and by a short distance in air.
Static Elimination
Ionizing radiation has also been used in specialized industrial equipment to reduce static electricity.
The radiation ionizes nearby air.
The resulting ions can help neutralize accumulated electrical charge.
This can be useful where static electricity could interfere with industrial processes.
Modern systems may use other ionization technologies as well.
Measuring Density
Radiation gauges can measure the density of materials.
A radiation source sends radiation through the material.
A detector measures how much radiation passes through.
Generally:
greater density → greater attenuation → lower detector reading
These techniques can be used in applications involving:
- construction materials
- industrial processing
- mining
- manufacturing
Radiation in Oil and Gas Exploration
Radiation-based instruments can be used to investigate underground rock formations.
Measurements can provide information about properties such as:
- density
- composition
- porosity
This helps scientists and engineers understand geological formations around boreholes.
Space Exploration
Radioactive materials can also provide energy for spacecraft.
Some spacecraft use:
radioisotope thermoelectric generators (RTGs)
An RTG uses heat produced by radioactive decay.
That thermal energy is converted into electrical energy.
Why RTGs Are Useful
Solar panels become less effective far from the Sun.
Some missions also operate in locations where sunlight is:
- weak
- intermittent
- unavailable for long periods
Radioisotope power systems can provide electrical power for many years.
They have been used on missions exploring the outer Solar System and on some planetary surface missions.
Plutonium-238
A commonly used isotope for radioisotope power systems is:
plutonium-238
Its radioactive decay releases thermal energy.
An RTG converts part of this heat into electricity.
The device is not a nuclear reactor.
It does not depend on a controlled chain reaction.
Instead, it uses:
heat from natural radioactive decay
Scientific Research and Particle Detection
Radiation detectors are also important scientific tools.
Examples include:
- Geiger-Müller counters
- scintillation detectors
- semiconductor detectors
- cloud chambers
- particle detectors
Scientists use these instruments to investigate:
- radioactive decay
- nuclear reactions
- cosmic radiation
- particle physics
- environmental radiation
Research Reactors and Radiation Sources
Specialized research facilities can produce:
- neutrons
- radioactive isotopes
- particle beams
These can be used to investigate:
- material structures
- nuclear properties
- biological molecules
- new materials
- fundamental physics
Radiation is therefore both something scientists study and a tool they use to investigate other phenomena.
Radiation and Materials Science
Radiation techniques can reveal information about the internal structure and properties of materials.
For example, neutron-based techniques can investigate:
- crystal structures
- magnetic materials
- polymers
- engineering components
Different forms of radiation interact with matter differently, giving scientists complementary information.
Quality Control Example
A factory manufactures aluminium foil.
A beta source is placed above the moving foil and a detector below it.
Suppose the detector reading decreases.
This means:
less beta radiation is passing through
A likely explanation is:
the foil has become too thick
The control system can then adjust the rollers.
Tracer Example
A factory suspects that an underground pipe is leaking.
A radioactive tracer is introduced into the fluid.
Detectors are moved along the pipeline.
At one location, an unexpectedly high radiation signal is detected outside the pipe.
This suggests:
tracer is escaping near that location
and therefore:
a leak may be present there.
Industrial Radiography Example
Engineers want to inspect a thick welded pipe.
Gamma radiation is directed through the weld.
A detector records the transmitted radiation.
If a region contains a void or crack, the amount of material along the beam path changes.
This can produce a difference in the radiographic image.
Engineers can identify the defect without cutting the pipe open.
Advantages of Radiation in Industry
Radiation-based techniques can provide several advantages:
- measurements without physical contact
- inspection without destroying products
- continuous monitoring
- detection through sealed containers
- high sensitivity
- ability to trace very small quantities
- operation in difficult environments
- automation of manufacturing processes
Limitations and Risks
Ionizing radiation can damage biological tissue.
Industrial and scientific applications therefore require careful control.
Potential issues include:
- worker exposure
- loss or damage of radioactive sources
- contamination
- radioactive waste
- transport and storage requirements
- security
- equipment and training costs
The benefits of using radioactive materials must justify these risks.
Radiation Safety
The fundamental radiation protection principles include:
Time
Reduce unnecessary time near radioactive sources.
Distance
Increase distance where practical.
Radiation intensity from a small source often decreases approximately according to:
I ∝ 1/r²
Shielding
Use appropriate shielding.
Examples include:
- plastic for some beta sources
- lead or concrete for penetrating gamma radiation
The correct shielding depends on the radiation involved.
Controlled Sources
Industrial radioactive sources are generally:
- clearly identified
- securely contained
- stored safely
- handled by trained personnel
- monitored according to applicable regulations
Many applications use sealed sources, where the radioactive material is enclosed to help prevent contamination.
Comparing Applications
| Application | Radiation Property Used | Typical Purpose |
|---|---|---|
| Thickness gauge | Partial absorption | Control sheet thickness |
| Level gauge | Penetration and absorption | Monitor container level |
| Industrial radiography | High penetration | Find internal defects |
| Radioactive tracer | Easy detection | Follow movement or locate leaks |
| Sterilization | Ionization | Destroy microorganisms |
| Smoke detector | Ionization | Detect smoke |
| Scientific tracer | Detectability | Follow biological/chemical processes |
| Radiometric dating | Predictable decay | Determine age |
| RTG | Decay heat | Generate spacecraft electricity |
Choosing the Correct Radiation
When selecting radiation for an application, ask:
How penetrating must it be?
How ionizing must it be?
Does it need to leave the material and reach a detector?
What half-life is appropriate?
Can the source be safely contained?
There is no single "best" type of radiation for every application.
Common Mistakes
Mistake: Saying beta radiation is always used for thickness monitoring.
Beta is often suitable for thin materials, but the appropriate radiation depends on the material and thickness.
Mistake: Saying gamma radiation is used because it is strongly ionizing.
Gamma radiation is especially useful in many industrial applications because of its high penetrating ability.
Mistake: Saying radioactive tracers make an entire industrial system dangerously radioactive.
Tracers are selected and controlled carefully, and only small amounts may be required.
Mistake: Saying irradiation automatically makes materials radioactive.
Exposure to radiation and becoming radioactive are different processes.
Mistake: Saying a smoke detector uses radiation to detect smoke directly.
In an ionization smoke detector, radiation ionizes air. Smoke changes the resulting electrical current.
Mistake: Saying an RTG is a nuclear reactor.
An RTG converts heat from radioactive decay into electricity; it does not operate using a controlled fission chain reaction.
Mistake: Choosing an extremely long-lived isotope for every tracer experiment.
The half-life should suit the duration and purpose of the investigation.
Key Terms
Industrial radiography — use of penetrating radiation to inspect the internal structure of manufactured objects.
Non-destructive testing (NDT) — inspection of a material or component without significantly damaging it.
Thickness gauge — system that uses radiation absorption to monitor material thickness.
Level gauge — radiation-based system used to monitor the level of material inside a container.
Radioactive tracer — radioactive substance used to follow the movement of material through a system.
Quality control — processes used to ensure manufactured products meet required standards.
Attenuation — reduction in radiation intensity as radiation passes through matter.
Autoradiography — imaging technique showing the distribution of radioactive material within a sample.
Neutron activation analysis — analytical technique in which neutron irradiation produces radioactive nuclei whose emissions can reveal elemental composition.
Sterilization — destruction or removal of microorganisms.
Irradiation — exposure of an object or material to radiation.
Ionization smoke detector — smoke detector that uses ionization produced by a small radioactive source.
Americium-241 — alpha-emitting radioisotope used in some ionization smoke detectors.
Radioisotope thermoelectric generator (RTG) — device that converts heat from radioactive decay into electrical energy.
Plutonium-238 — radioisotope used as a heat source in some radioisotope power systems.
Sealed source — radioactive material enclosed to help prevent its release into the environment.
Key Takeaways
- Radiation has many industrial, scientific and everyday applications.
- Radiation can be used for continuous industrial quality control.
- Beta radiation can be useful for monitoring thin sheets such as paper, plastic and foil.
- Gamma radiation can be used for thicker materials because it is more penetrating.
- Thickness gauges measure changes in radiation transmission through materials.
- Radiation can monitor material levels inside sealed industrial containers.
- Industrial radiography can reveal internal defects without destroying the component.
- Radioactive tracers allow scientists and engineers to follow the movement of substances.
- Tracers can help locate leaks and blockages in pipelines.
- An appropriate tracer should have a suitable half-life and detectable radiation.
- Radioactive tracers are useful in biology, chemistry and environmental science.
- Radioactive isotopes can be used to label and follow molecules in scientific experiments.
- Ionizing radiation can sterilize certain medical and laboratory products.
- Irradiating an object does not normally mean that the object becomes radioactive.
- Americium-241 is used in some ionization smoke detectors.
- Alpha radiation in an ionization smoke detector ionizes air and allows a small current to flow.
- Radiometric dating uses predictable radioactive decay as a natural clock.
- Radioactive decay can provide long-lasting energy for spacecraft.
- RTGs convert heat from radioactive decay into electrical energy.
- Radiation applications require careful safety procedures involving time, distance and shielding.
Check Your Understanding
- Give three industrial uses of ionizing radiation.
- Explain how radiation can be used to monitor the thickness of paper.
- What happens to the detector count rate if the paper becomes thicker?
- Why is beta radiation often suitable for monitoring thin materials?
- Why might gamma radiation be more suitable for monitoring a much thicker material?
- Explain how radiation can be used to monitor the level of material inside a sealed container.
- What is industrial radiography?
- Explain why industrial radiography is described as non-destructive testing.
- Give three types of defects that industrial radiography might detect.
- What is a radioactive tracer?
- Explain how a radioactive tracer could be used to locate a leak in an underground pipe.
- Why should a tracer's half-life be appropriate to the duration of the investigation?
- Give two examples of how radioactive tracers can be used in scientific research.
- Explain how ionizing radiation can sterilize medical equipment.
- Does irradiating medical equipment normally make the equipment radioactive? Explain.
- Which radioactive isotope is used in some ionization smoke detectors?
- Explain how an ionization smoke detector works.
- What is an RTG, and what energy transformation occurs inside it?
- Explain why radioactive power sources can be useful for some spacecraft.
- Compare the radiation properties needed for a thickness gauge, industrial radiography, and a radioactive tracer.