Nuclear energy has historically been at the center of the debate about the future of global energy. As humanity seeks cleaner, safer, and more sustainable sources to meet its growing energy needs, research into new nuclear technologies is gaining importance. Not only are conventional systems using uranium being studied, but also alternatives such as thorium, whose characteristics and potential are attracting increasing interest.
In the following lines, we invite you to immerse yourself in a detailed and up-to-date overview of the types of nuclear energy, the technical characteristics of each, the emerging role of thorium as an alternative fuel, and the major technological and theoretical advances that could pave the way for atomic energy in the future. This information brings together the most relevant current knowledge, integrating data from multiple specialized and popular sources, and does so with a clear, natural approach adapted to the Spanish-speaking world.
What is nuclear energy and how is it generated?
Nuclear energy is the energy stored in the nucleus of atoms., an enormous amount of energy that can be released through nuclear reactions. There are two main ways to harness it: fission and fusion. Although fusion is the process that powers the Sun, commercial technology today is entirely based on Nuclear fision.
In fission, the nucleus of a heavy atom such as uranium or plutonium splits into smaller fragments when bombarded by neutrons. This splitting not only produces lighter nuclei: it also releases additional neutrons and a considerable amount of energy in the form of heat and radiation.
This heat is used for generate steam that drives turbines, producing electricity in nuclear power plants. The process is analogous to a conventional thermal power plant, although with a different heat source.
Main types of nuclear reactors and technologies
The nuclear industry has developed a variety of technologies and reactor types over the past few decades. Below, we review in detail the most relevant ones, both in current use and in experimental or theoretical stages:
- Light Water Reactors (PWR and BWR): They are the most common in the world, they use ordinary water as a coolant and moderator of neutrons. Pressurized water reactors (PWR) and boiling water reactors (BWR) generally use enriched uranium.
- Heavy Water Reactors (PHWR): In these, heavy water (deuterium oxide) acts as a moderator and coolant. They allow the use of natural uranium or thorium fuel, making them a special option for countries with limited availability of enriched uranium.
- High Temperature Gas Reactors (HTR): They use a gas, such as helium, as a coolant and allow working at higher temperatures. They favor the use of alternative fuels, such as thorium, increasing efficiency and safety.
- Fast Neutron Reactors (FNR): They harness fast neutrons and can use both uranium and plutonium, while allowing for transmutation and maximum fuel utilization.
- Molten Salt Reactors (MSR): A technology still in the development phase, where nuclear fuel is dissolved in a molten salt, facilitating the use of thorium and other fertile elements.
- Accelerator-driven reactors (ADS): A revolutionary and still experimental concept in which a proton beam generated by an accelerator produces neutrons that sustain the reaction in a subcritical matrix of thorium or uranium.
Each type of reactor has its own advantages, challenges, and specific applications. Current systems focus on safety, fuel efficiency, and radioactive waste reduction, while experimental designs propose solutions for a cleaner, safer energy future.
The nuclear fuel cycle: from mining to waste
The nuclear fuel cycle begins with the extraction of the mineral from nature., usually uranium, although thorium is emerging as a promising alternative.
In the case of uranium, the enrichment of the isotope U-235 is required, as it only constitutes 0,7% of natural uranium and is responsible for sustaining the chain reaction. The process involves several stages: mining, conversion, enrichment, fuel manufacturing, reactor use, waste management, and, occasionally, reprocessing to recycle useful materials.
In cases where thorium is used as fuel, the process varies. Thorium-232 itself is not fissionable, but upon neutron capture, it transforms through a series of decays into uranium-233 (U-233), which is fissionable and can sustain a nuclear reaction. This conversion involves technical challenges but offers significant advantages in terms of sustainability and waste.
Waste treatment and storage remains the greatest ethical, technical, and social challenge for nuclear energy. With uranium and plutonium, waste remains hazardous for millennia, while the use of new technologies and fertile elements such as thorium could radically reduce the time during which waste would remain at a significant level of hazard.
The potential of thorium: the nuclear energy of the future?
Thorium is a chemical element discovered in 1828, notably more abundant in the Earth's crust than uranium. and with properties that give it considerable advantages over traditional nuclear fuels. It is found primarily in monazite, a rare earth mineral, and does not require enrichment for use, as it only exists in nature as thorium-232.
In its pure state, thorium has a half-life of about 14.000 billion years, making it extremely stable and low in radioactivity compared to other active ingredients. Furthermore, thorium oxide has a very high melting point, around 3350°C, and excellent thermal conductivity, making it ideal for applications requiring heat resistance.
Thorium is considered a fertile material, not directly fissile in thermal reactors, but capable of fission when converted into uranium 233., an excellent fissionable material. This is essential for next-generation reactors and advanced fuel experiments.
Thorium utilization methods for nuclear power generation include:
- Additive in uranium cycles, compatible with existing reactors.
- Supplementing the uranium cycle with plutonium, providing benefits in waste reduction.
- Complete replacement of the uranium cycle, using only thorium and recycled U-233.
The key in all these cases is to get a adequate neutron balance, so that neutron capture by thorium allows the generation of enough U-233 to sustain the reaction and potentially reproduce the fuel.
Advantages of thorium over uranium in nuclear energy
The advantages of using thorium as a nuclear fuel have generated renewed international interest., especially in countries with abundant reserves of this element and limited access to uranium.
Its main benefits include:
- Abundance: There is three to four times more thorium than uranium in the Earth's crust. This availability makes it especially attractive for meeting future energy demand.
- No enrichment required: All mined thorium is potentially usable as fertile material, simplifying the fuel cycle and reducing proliferation risks.
- Waste reduction: Radioactive waste generated by thorium is mostly much shorter-lived (around 200-400 years of dangerous radioactive activity) than current uranium waste, which remains dangerous for millennia.
- Safer against accidents: Thorium's melting point is much higher than that of uranium, providing additional safety margins in the event of an accident.
- Difficulty for military diversions: The thorium cycle also generates U-232, a strong gamma emitter that makes the generated materials difficult to handle and use in military operations.
The use of thorium could represent a paradigm shift in nuclear energy.: more efficient, less dangerous and more respectful of future generations.
Challenges, limitations and technical obstacles of thorium
However, not everything is an advantage in the development of thorium-based nuclear technology. Despite the promise and enthusiasm, there are significant challenges to overcome before thorium can become a competitive, commercial fuel on a large scale.
Some of the disadvantages and obstacles identified in international studies and experiences are:
- Insufficient technological maturity: To date, thorium technology has not passed all the testing and qualification stages required for commercial implementation. Multiple analyses, licensing, and strong government and investor support are still required.
- Development and manufacturing costs: The production and reprocessing process for thorium fuels is currently more expensive than that for uranium, although costs could be reduced as technology matures.
- Lack of commercial incentives: With uranium abundant and cheap, countries and companies have found little incentive to invest in new, resource-saving technologies when the main input is not in short supply.
- Complexity in control and management: The transition from thorium to U-233 requires careful management of reactivity and decay product issues during reactor operation and shutdowns.
- Historical and political problems: Part of the limited development of thorium technology to date is due to strategic decisions made in favor of plutonium, due to its usefulness in nuclear weapons after World War II.
Although these challenges are not without proposed solutions, the transition to the commercialization and mass deployment of thorium-based nuclear energy will ultimately depend on political will, sustained investment, and the resolution of still open scientific and technical challenges.
International projects, research and applications with thorium
Several countries have shown interest and experience in researching and testing thorium-based fuel cycles., especially those with large reserves or less access to uranium.
India This is the paradigmatic case: it has enormous reserves of thorium, but a shortage of uranium, which is why it has integrated the development of this technology into the core of its national nuclear program. Its strategy follows the so-called "three-stage program," combining heavy water reactors, fast neutron reactors, and advanced heavy water reactors.
In NorwayThor Energy has conducted tests in existing reactors using thorium-based fuels, along with uranium and plutonium, demonstrating the technical feasibility of the concept.
China, Canada, Germany, the Netherlands, the United Kingdom, Russia, Brazil and the United States have also carried out experimental demonstrations and prototypes of thorium reactors and fuels, including molten salt reactors and hybrid systems.
The fruits of these experiments have revealed both the current strengths and weaknesses of thorium, laying the groundwork for further development and possible large-scale industrial application in the future.
Molten salt reactors: the perfect candidate for thorium
Among the technologies associated with thorium, the molten salt reactor (MSR) stands out for its disruptive potential. In this type of reactor, the fuel is in a liquid state, dissolved in a mixture of molten salts. It allows high temperatures to be reached at low pressures, which reduces risks and improves thermal efficiency.
The molten salt fuel cycle would facilitate the continuous loading and unloading of fuel, the removal of fission products, and the gradual incorporation of thorium, optimizing the "reproduction" of U-233 and, therefore, the utilization of the resource.
Several international projects are focusing their R&D&I on MSR reactors., with special leadership from China and Russia, and the support of European and American institutions and companies.
Although commercial deployment is expected to take several decades, the molten salt reactor appears to be one of the most promising theoretical and technological advances on the global nuclear horizon.
New concepts: accelerator-driven reactors and the future of hybrid systems
Beyond conventional reactors, the development of accelerator-driven reactors (ADS) opens up new avenues for safe and flexible nuclear energy. In this system, a particle accelerator generates a beam of protons that, upon impacting a heavy target, produce a shower of neutrons through the phenomenon of spallation.
These neutrons are used to induce fission in a "subcritical" matrix of thorium or uranium, meaning one that cannot sustain a chain reaction on its own without external input from the accelerator.
The main advantage of these systems is their greater control and security: Simply turning off the accelerator instantly halts the reaction, eliminating the risk of accidents like those in Fukushima or Chernobyl. They also allow for the transmutation of long-lived radioactive waste.
The concept is still in the experimental phase, but projects like EMMA in the United Kingdom and international collaborations are bringing it closer to technical and economic reality.
Doubts and social debate about nuclear energy and thorium
The discussion about the future of nuclear energy and the role of thorium is far from unanimous. Environmental advocates argue that the resources and efforts devoted to nuclear research could have been directed toward promoting renewable sources, which are free of the risks of waste and accidents.
Some experts point out that the promising thorium technology still faces decades of refinement before it is truly competitive on an industrial scale., and that relying on it could delay urgent action against climate change, which requires immediate solutions.
However, the potential to reduce nuclear waste, improve reactor safety, and ensure a long-term supply of clean energy means that the thorium option has supporters both in the scientific community and among environmental sectors open to debate about new alternatives.
On the scales, Thorium-based nuclear energy is emerging as a transitional or complementary path. for renewable systems, capable of providing low-emission baseload electricity while renewable technology is developed and deployed massively.
Nuclear energy in figures: reserves, potential and energy horizon
According to recent international estimates, global reserves of thorium far exceed those of uranium, with large deposits in India, Australia, Norway, and Brazil. The so-called "Red Book" published by the OECD and the International Atomic Energy Agency estimates known and estimated resources at more than 6 million tons globally, which could sustain humanity for centuries if technology allows.
Furthermore, thorium is often found as a byproduct of rare earth mining, giving it an additional strategic and economic advantage, especially in the context of growing global demand for materials for electronics and clean energy.
The efficient and safe use of these reserves, along with the development of hybrid systems, advanced waste recycling, and an international non-proliferation policy, emerge as the major challenges of the coming nuclear era.
The development and integration of new nuclear technologies, with a particular emphasis on thorium and theoretical advances such as hybrid systems and molten salt reactors, could have a decisive impact on the safety, sustainability, and competitiveness of atomic energy in the 21st century. The current situation presents a scenario full of potential, but also of technical and social challenges. As these technologies continue to refine and mature, thorium could move from promise to reality, becoming a key element in the transition toward cleaner, safer, and more flexible energy systems that meet the needs of a constantly evolving planet.