Green Chemistry-integrated nuclear waste disposal methods like vitrification and cementation improve sustainability by reducing energy use, carbon footprint, and ecosystem toxicity compared to conventional techniques. However, their benefits depend on process optimization and specific waste characteristics.

Abdulhamid Dehghani

Green chemistry-integrated nuclear waste disposal methods, such as vitrification and cementation, represent significant progress toward more sustainable and environmentally friendly solutions compared to conventional techniques, such as long-term storage in casks or underground repositories. Analyzing key parameters such as energy efficiency, carbon footprint, and ecosystem toxicity enables a thorough assessment of their performance and sustainability in the long term.

1. Energy Efficiency

• Vitrification is a process that stabilizes nuclear waste in a glass matrix at very high temperatures (above 1000°C). While highly effective in ensuring the long-term stability of waste and minimizing the risk of radioactive leaching, the energy requirements for this process are significant. The use of fossil fuels to achieve these high temperatures results in high energy consumption, thereby increasing overall energy demand and indirect CO2 emissions. However, advancements in green chemistry technologies are focused on reducing these costs through the use of renewable energy sources and improving process efficiency, which can help reduce the energy impact.
• Cementation, which involves binding the waste in a cement mass, requires lower temperatures and, therefore, has a lower energy demand compared to vitrification. While cementation offers a relatively simple and cost-effective means of disposal, its main drawback lies in its lower long-term stability. Over time, cement matrices may exhibit signs of degradation, potentially requiring additional energy for future processing or reworking.

2. Carbon Footprint

• Vitrification has a significant carbon footprint due to the high energy consumption required for achieving the necessary temperatures. This process typically relies on fossil fuels, contributing to CO2 emissions. However, integrating green chemistry principles into vitrification involves introducing more energy-efficient technologies and utilizing renewable energy sources (e.g., solar or geothermal energy), which can significantly reduce the carbon footprint of this process.
• Cementation, given its lower energy demands, has a smaller direct carbon footprint. However, it is important to consider that cement production itself is highly energy-intensive and contributes to CO2 emissions. Although cementation as a waste disposal method may have a lower immediate impact compared to vitrification, its long-term contribution to the global carbon footprint needs to be carefully monitored, especially in light of increasing demands for more sustainable cement production.

3. Ecosystem Toxicity

• Vitrification is the superior option in terms of long-term stability and minimizing the risk of ecosystem contamination. The glass materials produced during vitrification have an extremely low tendency to leach radioactive and chemical contaminants into the environment, significantly reducing the risk to groundwater, soil, and plant and animal species. This process provides greater assurance regarding the preservation of ecosystems, particularly in the context of millions of years during which the waste will remain radioactive.
• Cementation, although effective in reducing leaching, offers lower long-term stabilization in comparison to vitrification. Cement matrices are more susceptible to degradation due to various factors, such as chemical corrosion, water, temperature fluctuations, and changes in pH. Given these risks, cementation may gradually lead to the release of radioactive and toxic materials into the environment, although this is a gradual process that occurs over longer time frames.

Green chemistry-integrated methods, such as vitrification and cementation, represent significant advancements over conventional nuclear waste disposal techniques. While these methods offer clear benefits in terms of reducing ecological and toxic risks, as well as improving long-term stability, challenges remain in terms of energy efficiency and carbon footprint. Vitrification, while effective in stabilizing and reducing the risk of contamination, requires high energy resources, while cementation, although more energy-efficient, carries the risk of reduced stability over decades. Further development of these technologies, with the integration of renewable energy sources and advanced materials, can significantly reduce their environmental impact, but continued research and optimization are necessary to ensure their sustainable development and implementation.

At the time of writing, the global installed capacity of nuclear power is 373 GW, provided by 415 operating reactors spread across 31 countries, while a further 209 power reactors have been shut down. Consequently, reactor decommissioning is both an existing and a future challenge for the sector, with the most recent reactors expected to operate into the 2080s.

Of the 209 shut down nuclear power reactors, 26 are UK Magnox reactors: a graphite-moderated, CO2-cooled design, similar to the French UNGG, which generated electricity from 1956 (with the commissioning of Calder Hall) until 2015. Construction of the Magnox fleet occurred across 11 stations in the UK over 16 years, with a combined capacity of 4110 MW. The first reactor to come offline was Berkeley in 1989, with the last generating reactor, Wylfa, coming offline in 2015. Nine similar French-designed UNGG reactors came offline in the 1990s.

Although their operating lifetime has come to an end, there is still a lot of work to be completed during their decommissioning. The initial policy adopted by the UK government was that all the Magnox reactors were to be defueled and made safe before being sealed for a period of quiescence (also known as ‘care and maintenance’) of up to 70 years while the radioactivity levels naturally decay making decommissioning activities less hazardous (NDA, 2016). In 2016, a review was conducted by the Nuclear Decommissioning Authority (NDA), the non-departmental public body of the government that supports development of UK nuclear policy, as to whether this approach was the most practicable after experience gained from the initial decommissioning of the Bradwell site. These approaches should be pursued and a period of quiescence is no longer a blanket policy (though varying lengths of deferred decommissioning may be considered dependent on the site condition). This new approach is going to first be explored on the next reactor chosen to be decommissioned, Trawsfynydd, which was selected due to the external structure having ‘degraded extensively since shutdown’ meaning that it would require more intensive work to make the site safe for a state of quiescence in comparison to ongoing decommissioning. Consideration was also given to “the low-economic-strength/high dependency on local Magnox Site”. Trawsfynydd has therefore been defined as a ‘lead and learn’ site, setting the precedent for the decommissioning of the remaining Magnox fleet.

This change in decommissioning from an assumed period of quiescence presents questions as to the environmentally optimal strategy for reactor decommissioning more broadly.

Life-Cycle Assessment (LCA) of nuclear waste management is a complex but essential process for evaluating environmental, economic, and social impacts from cradle to grave — from radioactive material generation to its final disposal. A rigorous LCA allows stakeholders to identify hotspots in the system, optimize processes, and ensure long-term sustainability and public safety.

At FACOP, our multidisciplinary team of experts brings a systems-thinking approach to nuclear waste management. We specialize in applying ISO 14040/44-compliant LCA methodologies tailored to high-risk, high-regulation sectors. Our consultants integrate advanced impact modeling, scenario analysis, and risk-informed decision-making to support the development of sustainable and socially responsible strategies for storage, containment, recycling, and final disposal.

Whether advising on geological repository planning, intermediate storage solutions, or minimizing lifecycle emissions and ecological footprints, FACOP provides evidence-based and future-proof guidance — balancing innovation, safety, cost-efficiency, and regulatory compliance.

We welcome collaboration on such a vital issue and are ready to contribute to building a safer and more sustainable nuclear future.