Katarzyna Kiegiel

Phosphogypsum (PG), a major by-product of phosphate fertilizer production, is an underutilized secondary source of rare-earth elements (REEs) and naturally occurring radioactive materials. This study presents a comparative assessment of REE leaching behavior and radionuclide partitioning in PG from major European deposits in Poland, Spain, Croatia, and Ukraine. Comprehensive chemical, mineralogical, and radiochemical characterization was combined with controlled leaching experiments under varying conditions. The results revealed strong deposit-dependent differences in REE content, extractability, and radiological properties, influenced by phosphate rock origin and processing history. Mineral acids (HCl, HNO ₃ , and H ₂ SO ₄ ) achieved the highest REE recoveries, with optimal conditions at pH 1–2, 30–40°C, and 3–4 h. Kinetic analysis using the shrinking-core model indicated diffusion-controlled leaching, enhanced by increasing acid strength. Radiochemical evaluation showed partial mobilization of uranium-series radionuclides into leachates, while thorium remained in solid residues, and radium was largely retained due to sulfate precipitation. Activity concentration indices and hazard parameters remained within recommended safety limits, indicating minimal radiological risk. These findings demonstrate that PG can be selectively valorized as a secondary REE resource while maintaining radiological safety.

To mitigate the effects of climate change, the world must significantly reduce its reliance on fossil fuels to lower greenhouse gas emissions. The nuclear power and renewable energy sources, such as solar, wind, water, waste, and geothermal energy, emit minimal to no greenhouse gases or pollutants during operation. These sources are considered crucial for combating climate change and supporting sustainable development. However, the production of electricity, like most industries, generates waste. Comparisons show clear differences: fossil fuel plants produce the largest total waste mass (primarily combustion ash, flue gas desulfurization residues, and wastewater sludge), while nuclear facilities generate a minimal volume but high-activity spent fuel and long-lived radioactive materials. Solar PV systems generate significant end-of-life electronic waste and glass encapsulant, and wind turbines yield moderate composite blade residues. Hydropower sediment management and geothermal scaling contribute unique waste streams of local concern. Regardless of the energy source, responsible waste management is critical to minimize environmental impacts. This article explores the sustainability of low-carbon energy sources, specifically focusing on waste management with the aim of highlighting the need of implementing targeted strategies such as advanced recycling and material substitution in order to minimize environmental impacts and enhance the circularity of low-carbon energy systems.

Phosphogypsum (PG), a large-volume by-product of phosphate fertilizer production, represents an underexploited secondary resource of rare earth elements (REEs) with growing relevance for advanced nuclear fuel and reactor technologies. This study evaluates the recovery of REEs from PG through an integrated chemical, radiochemical, and techno-economic framework aimed at producing high-purity rare earth oxides (REOs) suitable for nuclear-grade applications. Leaching experiments using H₂SO₄, HCl, and HNO₃ were coupled with a systematic assessment of five precipitation routes—oxalate, phosphate, fluoride, carbonate, and sulfate. Among the tested systems, oxalate precipitation from sulfuric acid leachates achieved the highest total rare earth element (TREE) recovery (94.2%) under elevated temperature and acid concentration, while carbonate and sulfate routes exhibited substantially lower efficiencies (<65%). A techno-economic assessment for a conceptual 100,000 t·y⁻¹ PG processing facility demonstrated strong economic viability, with the oxalate–H₂SO₄ system yielding the highest net present value (645 MUSD) and the lowest unit production cost of REOs among all evaluated routes. The results confirm that phosphogypsum can serve as a strategic secondary feedstock for REEs relevant to nuclear fuel fabrication, neutron-absorbing materials, and advanced reactor systems. The validated process route and economic framework provide a basis for pilot-scale implementation and support the integration of industrial waste valorization into secure and sustainable nuclear material supply chains.

Nuclear energy can help stop climate change by generating large amounts of emission-free electricity. Nuclear reactor designs are continually being developed to be more fuel efficient, safer, easier to construct, and to produce less nuclear waste. The term advanced nuclear reactors refers either to Generation III+ and Generation IV or small modular reactors. Every reactor is associated with the nuclear fuel cycle that must be economically viable and competitive. An important matter is optimization of fissile materials used in reactor and/or reprocessing of spent fuel and reuse. Currently operating reactors use the open cycle or partially closed cycle. Generation IV reactors are intended to play a significant role in reaching a fully closed cycle. At the same time, we can observe the growing interest in development of small modular reactors worldwide. SMRs can adopt either fuel cycle; they can be flexible depending on their design and fuel type. Spent nuclear fuel management should be an integral part of the development of new reactors. The proper management methods of the radioactive waste and spent fuel should be considered at an early stage of construction. The aim of this paper is to highlight the challenges related to reprocessing of new forms of nuclear fuel.