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.

Due to the hazardous nature of Ionising Radiation, it must be disposed of carefully and safely.

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.

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.

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

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

• Low-level waste

• Intermediate-level waste

• High-level waste

Basic Steps in Radioactive Waste Management

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

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 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.

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.

Fig. 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.

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.

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

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.

^{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}