Methods for Safe Disposal of Radioactive Waste

Every year, nuclear power plants, hospitals, research institutions, and industrial facilities around the world generate thousands of tonnes of radioactive waste. Unlike ordinary waste, radioactive material remains hazardous for decades, centuries, or even millions of years – which makes disposal one of the most technically demanding challenges in environmental science. Getting it wrong, even once, can have irreversible consequences for ecosystems and human health. This post breaks down how radioactive waste is classified and examines the specific disposal methods used to manage each category safely.

Understanding the types of radioactive waste 🔗

Not all radioactive waste is the same. The International Atomic Energy Agency (IAEA) classifies radioactive waste into six categories based on the activity levels of the radionuclides it contains and the length of time it remains dangerous. For practical disposal purposes, these categories are most often discussed as three main groups: low-level waste, intermediate-level waste, and high-level waste.

Low-level waste (LLW) 🔗

Low-level waste is the most common type by volume. According to the Wikipedia overview on radioactive waste, LLW accounts for roughly 90% of the total volume of all radioactive waste globally, yet contains only about 1% of the total radioactivity. It includes everyday items that have become contaminated with radioactive material – things like protective clothing, wiping rags, mops, medical syringes, lab equipment, and water treatment residues from nuclear reactors. Most LLW has short-lived radioactivity and does not require shielding during handling, although higher-activity LLW does require containment. Its radioactivity typically decreases to safe levels within a few hundred years.

Intermediate-level waste (ILW) 🔗

Intermediate-level waste contains higher concentrations of radioactivity than LLW and includes materials such as chemical sludge, metal fuel cladding, resins, and materials from reactor decommissioning. According to the National Academies of Sciences, ILW – as defined under IAEA standards – requires a greater degree of containment and isolation than near-surface disposal alone can provide, particularly when it contains long-lived radionuclides. It generally does not generate significant heat during storage, which distinguishes it from high-level waste. ILW may be solidified in concrete or bitumen before disposal.

High-level waste (HLW) 🔗

High-level waste is produced primarily from spent nuclear fuel and the reprocessing of nuclear materials. It is intensely radioactive and generates considerable heat from radioactive decay, which means it requires both shielding and active cooling. ENSREG, the European Nuclear Safety Regulators Group, notes that HLW must be isolated in deep, stable geological formations – typically hundreds of metres below the surface – for timescales extending to hundreds of thousands of years. Though HLW makes up less than 1% of all radioactive waste by volume, it contains the vast majority of the total radioactivity.

Disposal techniques for radioactive waste 🔗

The method of disposal depends directly on the waste’s classification. The guiding principle is straightforward: the higher the radioactivity and the longer it persists, the deeper and more isolated the disposal must be. Three primary techniques are used internationally – landfill disposal, near-surface disposal, and deep geological disposal.

Landfill disposal 🔗

Landfill-type disposal is reserved for the least hazardous radioactive material – specifically very low-level waste (VLLW). The IAEA’s guidance on long-lived low and intermediate level waste confirms that landfill disposal is suitable for very low-level waste with minimal concentrations of long-lived radioactivity. These facilities involve no complex engineered barriers and resemble standard municipal landfills in structure. The waste is buried in simple trenches or cells, covered with waterproof material, and monitored for a period after closure. Strict waste acceptance criteria ensure only materials with extremely low radionuclide content – especially low in long-lived activity – are admitted to these facilities. Mining waste containing naturally occurring radionuclides, for instance, may sometimes follow this route when activity levels permit.

Near-surface disposal 🔗

Near-surface disposal is the most widely used method globally and is the standard approach for low-level waste and some short-lived intermediate-level waste. Countries including Spain, France, Japan, Sweden, Finland, the United Kingdom, and the United States all use engineered near-surface repositories. These facilities are located at or within a few tens of metres of the surface and rely on a combination of engineered barriers – such as reinforced concrete vaults, grouted metal containers, and drainage systems – and the natural properties of the surrounding soil and rock to contain radionuclides.

The safety of near-surface disposal is based on both the engineered containment system and a period of active institutional control after the facility closes. This control, which may last for centuries, involves monitoring, restricted land use, and surveillance to prevent human intrusion while the waste’s radioactivity decays to acceptable levels. As the IAEA states, this method works well for waste with limited concentrations of long-lived radionuclides, because institutional controls can realistically be maintained for the duration needed for the radioactivity to decay.

In the UK, for example, low-level waste is disposed of at the Low Level Waste Repository in Cumbria, where waste is placed in grouted metal containers stacked within concrete vaults – a step up from the earlier landfill-style trenches used at the same site.

Deep geological disposal 🔗

Deep geological disposal (DGD) is the internationally recognised approach for high-level waste and long-lived intermediate-level waste. The concept involves placing waste in engineered repositories excavated hundreds of metres underground in stable geological formations – typically granite, clay, or salt rock – where the natural geology provides long-term isolation without relying on human oversight. According to the World Nuclear Association, deep geological disposal is the preferred method in countries including Finland, France, Sweden, Canada, Japan, Switzerland, and the United States.

The approach uses a multi-barrier system: the waste itself is vitrified (converted to glass) or encapsulated in steel or copper canisters; these are surrounded by a buffer material such as compacted bentonite clay; and the entire package is placed within the excavated rock. Each layer provides an independent line of protection against the migration of radionuclides into groundwater or the surrounding environment. Finland’s Onkalo repository, located in Eurajoki and excavated to a depth of 400-450 metres in bedrock, is the world’s first deep geological repository to be licensed for the permanent disposal of spent nuclear fuel from civil reactors. France is advancing its Cigeo facility, planned at approximately 500 metres depth in a clay formation in Bure.

Deep geological disposal is designed to be passive – meaning that once sealed, no active monitoring or maintenance is required to keep the waste isolated. This is especially important given that some radionuclides in HLW remain dangerous for over a million years, far beyond any realistic timeframe for institutional management.

Borehole disposal: a practical solution for small volumes 🔗

A distinct but increasingly important disposal method is borehole disposal. Rather than large mined tunnels, this approach involves drilling a narrow hole – typically a few tens to a few hundred metres deep – and placing sealed waste packages within it before sealing the borehole with engineered materials. According to the IAEA’s 2024 Safety Guide on Borehole Disposal Facilities, this method is specifically designed for the disposal of disused sealed radioactive sources (DSRS) and small volumes of low and intermediate level secondary waste generated during their management.

What are disused sealed radioactive sources? 🔗

Sealed radioactive sources are devices in which radioactive material is permanently enclosed within a capsule or bonded in solid form. They are used across a wide range of sectors – in medicine for cancer radiotherapy, in industry for equipment testing and sterilisation, and in research and agriculture. Once they reach the end of their useful life, they are classified as disused sealed radioactive sources. As the IAEA explains, even though a disused source may no longer emit sufficient radiation for its intended purpose, it remains radioactive and potentially hazardous, and must be managed as radioactive waste.

The challenge, particularly for developing countries, is that these sources accumulate in small quantities – far too little to justify the cost and infrastructure of a full near-surface or deep geological repository, yet too hazardous to leave in indefinite storage. The IAEA reports that under typical circumstances, a developing country may generate hundreds of disused sources with low levels of radioactivity over several years, and that once conditioned for disposal, hundreds of such sources can occupy less than one cubic metre of space.

How borehole disposal works 🔗

The borehole disposal concept, as detailed in IAEA Safety Standards Series No. SSG-1, involves placing conditioned waste packages containing disused sealed sources into an engineered borehole drilled and operated directly from the surface. The sources are first encapsulated – typically in stainless steel capsules – before being lowered into the borehole. The borehole is then progressively filled with sealing materials such as bentonite, cement, or crushed rock to create a low-permeability barrier between the waste and the surface environment.

The key advantage of borehole disposal is its simplicity and accessibility. The drilling technology required is similar to that used in water well construction and is available in most countries, including those with limited infrastructure. The method requires no large construction project, no complex engineered facility, and relatively modest financial investment. The IAEA describes the borehole disposal concept as an economical yet safe solution that is particularly well-suited to countries with small waste inventories and limited human and financial resources.

Disposal depths in borehole facilities for sealed sources generally range from a few tens of metres to several hundred metres, depending on the activity levels of the waste and the geological conditions of the site. The IAEA’s standard borehole design uses a narrow diameter of approximately 26 centimetres, suitable for sources less than 110 mm in length – covering a wide range of commonly used sealed sources from medical and industrial applications.

Security and long-term safety benefits 🔗

Beyond managing environmental risk, borehole disposal also addresses nuclear security concerns. Disused sealed sources stored above ground – whether in hospitals, universities, or industrial facilities – represent a potential security risk if not adequately protected. Placing them permanently underground in a borehole significantly reduces the risk of theft or misuse. As the IAEA notes, limiting the probability of disused sources being accessed and used for malicious purposes is a key driver behind promoting the borehole disposal method globally.

Borehole disposal facilities have already been implemented in several countries for the storage and disposal of radioactive waste including disused sealed sources, with examples recorded in the USA, Australia, and Russia. The IAEA has actively tested the transfer technology in Croatia and is assisting multiple member states in implementing this solution – providing training, technical specifications, and equipment support to enable safe national disposal programmes.

Matching waste type to disposal method 🔗

Each disposal method exists because no single approach can safely manage the full spectrum of radioactive waste. Very low-level waste with minimal long-lived activity can go to landfill-type facilities with basic controls. Low-level and short-lived intermediate-level waste is handled in engineered near-surface repositories with institutional oversight for periods of up to a few hundred years. Long-lived intermediate-level and high-level waste, which remains hazardous far beyond any realistic monitoring period, requires deep geological disposal in stable rock formations hundreds of metres below the surface. And for countries managing only small quantities of disused sealed sources, borehole disposal provides a cost-effective, secure, and technically sound alternative that avoids the need for large-scale infrastructure.

The underlying logic across all these methods is the same: place the waste in an environment where natural and engineered barriers together can isolate radionuclides from the biosphere for as long as they remain dangerous – whether that is 300 years or 300,000 years.

What do you think? As countries continue to expand nuclear energy in response to climate goals, the volume of radioactive waste will inevitably grow – does the current portfolio of disposal methods seem adequate for the long term, or are new approaches urgently needed? And given that deep geological repositories won’t be universally available for decades, what responsibilities do nations with small nuclear programmes have in managing their waste in the interim?

References

1. https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1419_web.pdf
2. https://en.wikipedia.org/wiki/Radioactive_waste
3. https://www.nationalacademies.org/read/26500/chapter/14
4. https://www.ensreg.eu/safe-management-spent-fuel-and-radioactive-waste/categorisation-radioactive-waste
5. https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1407_web.pdf
6. https://www.geoengineer.org/education/web-class-projects/ce-176-environmental-geotechnics/assignments/nuclear-waste-disposal
7. https://world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-waste/storage-and-disposal-of-radioactive-waste
8. https://www.iaea.org/publications/15332/borehole-disposal-facilities-for-disused-sealed-radioactive-sources
9. https://www.iaea.org/newscenter/news/iaea-reaches-milestone-disposal-radioactive-sources
10. https://www-pub.iaea.org/MTCD/Publications/PDF/Pub1418_web.pdf
11. https://www.iaea.org/newscenter/news/technological-challenges-safe-disposal-radioactive-waste