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Radioactive Waste Management

Radioactive Waste Management

How much do you know about radioactive waste? Your perception of it may have been affected by television and films. They often show radioactive waste as a bright, toxic sludge that corrodes everything it touches. The reality is less exciting, and fortunately, less dangerous! Most radioactive waste is solid, plain, and not especially hazardous.

Interested to know more? Don't waste your time – get reading!


Radioactive Waste: Definition

Let's begin with the definition of radioactive waste.

Radioactive waste is any material that is intrinsically radioactive, or has been contaminated by ionising radiation.

Due to the hazardous nature of ionising radiation, it must be disposed of carefully and safely.

Ionising radiation is a form of electromagnetic radiation with enough energy to remove electrons from atoms that it passes through (hence the name ionising, as it converts atoms into positive ions). Radioactive objects release high-energy gamma rays and packages of subatomic particles. Exposure to radiation creates free radicals, highly reactive and unstable molecules. Free radicals damage your cells and DNA, leading to tissue damage and cancer.

Despite this, we are surrounded by background radiation. It comes from many sources from the sun to food we eat and drink - both man made and natural.

Examples of Radioactive Waste

Radioactive waste can come from a variety of sources. Most of the UK's radioactive waste comes from decommissioning nuclear power plants, but there are a few other surprising industries.

IndustryRadioactive Waste
Materials used in the operation and decommissioning of nuclear power plants become contaminated with ionising radiation.
Healthcare
Radioactive waste is generated from radiation-based treatments and diagnostic processes. It usually consists of sharps, vials, PPE, and absorbent materials.
Agriculture
Phosphate rock is extracted and processed to create fertilisers. Waste rock often contains radioactive elements, such as uranium, thorium, and radium.
Research
Radioactive materials are used in biological, medical, chemical, and physics research.

Radioactive Waste Management: Policy and Strategy

Items with no further use that are contaminated by radiation above 10,000 Becquerels are classified as radioactive waste.

The Becquerel is the derived unit of radioactivity. One Becquerel is equivalent to one nuclear decay per second.

Radioactive waste is hazardous, and can impact human health. Exposure to ionising radiation is associated with cancer, tissue damage, and acute radiation sickness. Thus, it must be disposed of appropriately and safely.

Characterisation of Radioactive Waste

Before disposal, all radioactive waste needs to be 'characterised' according to their properties. Scientists characterise radioactive wastes using:

  • Information about how, when, and where the waste was produced

  • Measuring radiation emitted

  • Taking samples for laboratory analysis

  • Interpreting data

Waste characterisation is important, but it can be expensive. So, waste producers must prioritise which wastes need to be assessed first.

Radioactive waste is separated into one of three categories, depending on its level of radioactivity:

  • Low-level waste

  • Intermediate-level waste

  • High-level waste

Nuclear materials are radioactive items that have potential value, and are not currently considered as waste. That includes uranium and plutonium, elements which can be used to make nuclear fuel. Nuclear materials also include spent nuclear fuels, which can be reprocessed and reused. Even after five years in a reactor, spent nuclear fuel still contains over 90% of its potential energy!

At present, nuclear materials are safely stored in case there is a need for them in future. If the UK government decides that the materials have no further use, they will reclassify them as waste. The government make this decision based on economic, environmental, and safety grounds.

Radioactive Waste Management spent uranium fuel StudySmarterFig. 1 – Spent uranium fuel. Source: pixabay.com

Basic Steps in Radioactive Waste Management

What are the basic steps carried out by producers of radioactive waste?

  1. Planning and Preparation: the first (and most critical) step is to minimise the volume of waste produced. Waste managers also consider how the waste will be dealt with, before it arises.

  2. Waste Treatment: the techniques depend on the category of waste, and its intended disposal.

  3. Packaging: most radioactive waste requires special packaging for storage and disposal. This makes it easier and safer to handle and transport.

  4. Storage: waste is stored in interim facilities until the radioactivity has dissipated. The storage period ranges from a few months to multiple decades, depending on the level of radioactivity.

  5. Disposal: waste is placed into engineered facilities for permanent storage.

Transport

Radioactive wastes may need to be transported during the disposal process. Transport usually takes place via road or rail, and is subject to strict conditions.

The UK is home to only one vitrification plant – an establishment that cools high-level radioactive waste using glass. The plant is part of Sellafield Ltd, a nuclear site on the Cumbrian coast. Any waste requiring vitrification is transported to Sellafield. As well as being the only vitrification plant in the UK, it stores up 80% of the country's nuclear waste!

The Waste Hierarchy

The waste hierarchy sets out a priority order for managing waste materials, based on its environmental impacts.

  1. Waste prevention

  2. Waste minimisation

  3. Reuse of materials

  4. Recycling

  5. Disposal

Disposal techniques depend on the level of radioactivity. To recap, the three categories are low-level waste, intermediate-level waste, and high-level waste. Now, we're going to look at the disposal process for each type of waste.

Low-level Radioactive Waste Management

Approximately 94% of radioactive waste is categorised as low-level – i.e., experiencing relatively low levels of radioactivity.

Low-level waste (LLW) is monitored to make sure that it doesn't exceed 4 GBq (gigabecquerels) of alpha activity, or 12 GBq of beta or gamma activity.

Most of the UK's LLW originates from the operation and decommission of nuclear facilities, but some comes from universities and hospitals.

The waste is grouted (consolidated) in metal containers, then stacked into concrete-lined, highly engineered vaults. When the vaults are full, they will be covered by a cap.

Radioactive Waste Management radioactive waste StudySmarterFig. 2 – Barrels of radioactive waste stored in an underground vault. Source: Wikimedia Commons

New Approaches to Managing Low-level Waste

To make the waste management process more sustainable, nuclear sites are exploring different waste and treatment options for LLW.

  • Metals Recycling: metals with low levels of surface radioactivity can be recycled. The surface of the metal is removed by shot blasting, leaving clean uncontaminated metal below. Alternatively, radioactive contaminants can be removed during melting.

  • Incineration: plastics, textiles, and oils can be incinerated. This reduces the volume of waste for disposal by over 90%.

  • Landfill: waste with minimal amounts of radioactivity is classified as Very Low-level Waste (VLLW). This waste can be disposed of at permitted landfill sites, alongside non-radioactive wastes. However, there are strict controls regarding the amount of VLLW that can be disposed of at regular landfill sites.

Intermediate-level Radioactive Waste Management

Around 6% of radioactive waste is categorised as intermediate-level. It exceeds the radiation limits of low-level waste, but unlike high-level waste, it does not generate heat. Most intermediate-level waste (ILW) comes from nuclear reactor components and sludge from effluent treatment.

First, ILW is treated before storage and disposal. Treatments include:

  • Super-compacting: using a hydraulic press to reduce the volume of waste

  • Cutting: large items are reduced in size to fit into packaging containers. Cutting uses conventional tools, plasma-jets, lasers, or explosive fuses.

  • Drying: liquid waste is dried using inert gases and heat.

After treatment, the waste is immobilised in cement and placed into a stainless-steel container. Larger items are packed into concrete boxes or cast iron containers.

Long-term Storage

The preferred option for storing ILW is geological disposal.

Geological disposal involves placing packaged waste in an engineered, underground repository.

The rocks provide a barrier against the escape of radioactivity. There is no intention to retrieve the waste after the facility is closed; the waste will be stored underground permanently.

High-level Radioactive Waste Management

Less than 1% of all radioactive waste is categorised as high-level. Usually found in liquid form, this waste is hot due to its radioactivity. Sources of high-level waste (HLW) include reactor operation and reprocessing nuclear fuel.

Liquid HLW undergoes vitrification at Sellafield Nuclear Site, Cumbria.

Vitrification is the process of mixing liquid waste with crushed glass to produce a molten product.

After vitrification, the molten product is poured into stainless-steel canisters incorporated with neutron absorbers for long-term storage (at least 50 years).

Neutron absorbers act like the control rods in a nuclear power plant, preventing hazardous chain reactions of decay.

Over time, the radioactivity will dissipate, and the waste will cool down. Eventually, it will undergo geological disposal.


I hope that this article has explained how radioactive waste is managed. Waste is categorised into three types according to its level of radioactivity: low-level, intermediate-level, and high-level. Most waste is sealed and placed in long-term storage.

Radioactive Waste Management - Key takeaways

  • Radioactive waste is any material that is intrinsically radioactive, or has been contaminated by radiation. Most of the UK's radioactive waste comes from decommissioning nuclear power plants.
  • Radioactive waste is separated into one of three categories: low-level, intermediate-level, and high-level. The basic steps carried out in radioactive waste management are: planning and preparation, waste treatment, packaging, storage, and disposal.
  • Low-level radioactive waste is grouted into metal containers, then stacked into engineered vaults. However, some can be recycled.
  • Intermediate-level waste is treated, immobilised, and placed in steel containers for geological disposal.
  • High-level waste undergoes vitrification, then is poured into specialised stainless-steel containers for geological disposal.

1. EDP Sciences, Very low-level waste (VLLW), Radioactivity.Eu, 2022

2. James Temperton, Inside Sellafield: how the UK's most dangerous nuclear site is cleaning up its act, Wired, 2016

3. Office of Nuclear Energy, 5 Fast Facts about Spent Nuclear Fuel, U.S. Department of Energy, 2022

4. UK Radioactivity Waste Inventory, About radioactive waste, 2022

Frequently Asked Questions about Radioactive Waste Management

Radioactive waste management is the management and disposal of material contaminated by ionising radiation.

The basic steps in radioactive waste management are planning and preparation, waste treatment, packaging, storage, and disposal.

The three types of radioactive waste are low-level, intermediate-level, and high-level.

Radioactive materials are consolidated into metal containers, then stacked into concrete-lined, highly engineered vaults. 

Spent nuclear fuels can be recycled into new fuels or useful by-products.

Final Radioactive Waste Management Quiz

Question

Define radioactive waste.

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Answer

Radioactive waste is any material that is intrinsically radioactive, or has been contaminated by ionising radiation.

Show question

Question

What is the Becquerel, and what is it equivalent to?

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Answer

The Becquerel is the derived unit of radioactivity. One Becquerel is equivalent to one nuclear decay per second.

Show question

Question

How is radioactive waste categorised?

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Answer

Radioactive waste is categorised according to its level of activity.

Show question

Question

What is the first step of radioactive waste management?

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Answer

Planning and preparation is the first step of radioactive waste management. Producers aim to minimise the quantity of waste produced, and plan its disposal in advance.

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Question

How is radioactive waste transported?

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Answer

Radioactive waste is transported by road or rail.

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Question

What percentage of radioactive waste is categorised as low-level?

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Answer

94%

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Question

How is low-level radioactive waste managed?

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Answer

Low-level waste is grouted in metal containers, then stacked into concrete-lined, highly engineered vaults, covered by a cap.

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Question

Some low-level radioactive waste can be incinerated. Which materials?

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Answer

Plastics, textiles, and oils can be incinerated.

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Question

What percentage of radioactive waste is categorised as intermediate-level?

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Answer

6%

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Question

What treatment technique uses a hydraulic press?

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Answer

Super-compaction

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Question

Define geological disposal.

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Answer

Geological disposal involves placing packaged waste in an engineered, underground repository.

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Question

Name two sources of high-level waste.

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Answer

Sources of high-level waste include reactor operation and reprocessing nuclear fuel.

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Question

What is vitrification?

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Answer

Vitrification is the process of mixing liquid waste with crushed glass to produce a molten product.

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Question

What is the purpose of neutron absorbers?

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Answer

Neutron absorbers act like the control rods in a nuclear power plant, preventing hazardous chain reactions of decay.

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Question

Which category of waste is often found in hot, liquid form?

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Answer

High-level waste

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