Ionising Radiation

Ionising vs Non-Ionising Radiation

Not all radiation is ionising. Let's look back to GCSE Physics and the electromagnetic spectrum.

The electromagnetic spectrum covers the range of wavelengths of radiation.

The wavelengths of radiation decrease from the left side to the right side.

There are seven types of electromagnetic radiation. In order of decreasing wavelength, (and increasing energy) they are:

1. Radio Waves

2. Microwaves

3. Infrared Radiation

4. Visible Light

5. Ultraviolet Radiation

6. X-rays

7. Gamma Rays

Radio waves, microwaves, infrared radiation, and visible light are considered non-ionising. They have a lower frequency, so they have less energy than ionising radiation.

Ultraviolet radiation, X-rays, and gamma rays are considered ionising. Unlike non-ionising radiation, ionising radiation can alter molecules within our bodies.

Types of Ionising Radiation

We've learned that the three types of ionising radiation are ultraviolet radiation, X-rays, and gamma rays. Let's go into detail about each type.

Uses and Examples of Ionising Radiation

High-energy ionising radiation is important in a range of industries.

Nuclear Weapons

When a free neutron hits the nucleus of a radioactive material (e.g. uranium), it sets off a chain reaction of nuclear decay, releasing neutrons and large amounts of ionising radiation. Nuclear weapons such as atomic bombs exploit chain reactions of nuclear fission, producing an atomic explosion.

Nuclear Power

Nuclear power also exploits the chain reactions of nuclear fissions, but instead using the energy produced to generate electricity. The energy released from the nuclear decay of uranium or plutonium is used to convert water into steam. The steam travels through turbines, which drives a generator, converting the turbine's kinetic energy into electricity.

Ship Propulsion

Ionisation radiation could present a carbon-free propulsion source for ships. Controlled chain reaction of nuclear decay releases large amounts of energy. Technology on board the ship transfers this energy to a coolant, which is used to generate propulsion power.

Manufacturing and Industry

Ionising radiation is frequently used in manufacturing and industry, including:

• Disinfecting drinking water

• Checking for defects in metallic castings and welds

• Locating fossil fuels and minerals for extracting

• Making signs reflective

• Producing non-stick cookware

• Creating wrinkle-free clothing

Healthcare

Gamma radiation is used to sterilise medical equipment without using heat. It's also important in many diagnostic and treatment practices.

• X-rays are used to detect and diagnose broken bones.

• Radiotherapy uses targeted doses of gamma radiation to destroy tumours in the body.

• Tracers containing radioactive isotopes are used to make soft tissues show up in medical imaging, and indicate tissue blockages.

Agriculture and Food Production

The agriculture industry exposes plants to ionising radiation to control insect populations, thus reducing the demand for polluting pesticides.

Fresh fruit is often exposed to ionising radiation from an isotope of cobalt-60. Gamma rays emitted by the cobalt will destroy any bacteria on the fruit, without contaminating or damaging the fruit in any way.

Irradiation pasteurisation exposes milk to ionising radiation, killing bacteria without the use of heat.

Dangers of Ionising Radiation

Exposure to ionising radiation can cause health problems. The high-energy radiation removes electrons from atoms, creating unstable molecules called free radicals. Free radicals are highly reactive, causing damage to the body's cells and DNA:

• Cell degeneration

• Ageing

• Mutagenesis – gene mutations

• Carcinogenesis – transformation of normal cells into cancer cells

Health Consequences Caused by Free Radicals

Cell damage caused by free radicals results in a range of health consequences.

Radiation Sickness

Exposure to an acute dose of ionising radiation can cause radiation sickness. Symptoms include:

• Nausea

• Vomiting

• Diarrhoea

• Skin damage

• Haemorrhaging (bleeding from a damaged blood vessel)

• Hair loss

• Immune system problems

Cancer

Free radical damage may trigger carcinogenesis. Alternatively, damaged cells may be unable to repair themselves, leading to cancer in the long term.

Even high levels of exposure to sunlight (containing UV radiation) is associated with skin cancer in later life.

Figure 3 – Metastatic melanoma cells under a microscope. This condition occurs when cancerous melanoma cells (caused by exposure to ionising ultraviolet radiation) spread to the rest of the body. Source: unsplash.com

Heritable Effects

If pregnant women are exposed to ionising radiation, it can impact the foetus. Effects include stunted growth, deformities, brain abnormalities, and an increased risk of cancer.

Ionising Radiation: UK Regulations

Due to the health risks of ionising radiation, it's regulated carefully.

The Ionisation Radiation Regulations 2017 (shortened to IRR17) is the main legislation regulating exposure to ionising radiation in the UK. Any employer or industry where ionising radiation is used must comply with the IRR17.

All employers are required to keep exposure to ionising radiation as low as possible. Exposures must not exceed specified dose limits of:

• 20 mSv in a calendar year

• Or 100 mSv over five consecutive years, with a maximum dose of 50 mSv in a single year

Additionally, it's important to note that nuclear power generates large amounts of radioactive waste. This needs to be disposed of carefully to prevent contamination.

I hope that this article has explained ionisation radiation for you. Remember that it is a form of radiation with enough energy to remove electrons from atoms it passes through. Ionising radiation is useful in a range of industries. However, exposure to large amounts of ionising radiation can be dangerous, so it is regulated carefully.

^{1. American Museum of Natural History, Constant Speed, 2022}

^{2. History.com, Bombing of Hiroshima and Nagasaki, 2022}

^{3. Patrick J. Kiger, What Is Planck's Constant, and Why Does the Universe Depend on It?, How Stuff Works, 2019}

^{4. UK Government, The Ionising Radiations Regulations 2017, 2017}

^{5. University of Tennessee, The EM Spectrum, 2022}