Nuclear energy

23 January 2026

The topic of nuclear energy is currently at the center of the European debate, both with regard to the construction of next-generation facilities and to the strategic investments in research and development required to bring nuclear fusion from a prospective application to a concrete technological reality. In both cases, nuclear fission and fusion, the production of energy and the management of power-generation facilities require the development of advanced technologies, some of which are deeply rooted in fundamental research in nuclear and particle physics.
Energy can be produced through nuclear processes essentially in two ways. The first involves the splitting of a heavy nucleus, such as those of uranium or plutonium, into two lighter nuclei: this is the process known as nuclear fission. The second method involves the fusion of light nuclei, for example isotopes of hydrogen, to form a heavier nucleus; this process is known as nuclear fusion. Both processes make it possible to release large amounts of energy thanks to the conversion of a small fraction of the mass of the nuclei involved into energy, in accordance with the well-known relativistic relation E = mc², and in compliance with the principle of conservation of energy.
Nuclear fission is a well-established technology and has been used for decades in numerous electricity-generating power plants worldwide. Nuclear fusion, by contrast, is still the subject of intense research, with the aim of harnessing its extraordinary potential in future reactors dedicated to the production of clean and sustainable energy.

I processi di fissione e fusione nucleare. ©INFN

On the left, a representation of the nuclear fusion process of a deuterium (2H) nucleus and a tritium (3H) nucleus. In reactors that currently produce nuclear energy, the “reverse” process occurs, known as “nuclear fission” (on the right in the figure). (© INFN)

Nuclear fission

Nuclear power plants currently operating in many European countries, and from which Italy imports a share of electricity estimated at around 7%, are based on the process of nuclear fission. In Europe, a significant fraction of the electricity consumed is generated through this mechanism (approximately 24% in 2024). Nuclear fission therefore represents an extremely powerful technology for large-scale energy production, with the advantage, compared to the combustion of fossil fuels (oil, gas, and coal), of not producing direct emissions of greenhouse gases or fine particulate matter into the atmosphere. For this reason, nuclear energy is often included among the so-called low-carbon energy sources.
Alongside these positive aspects, nuclear fission nevertheless presents certain critical issues related to safety and the production of radioactive waste. Maintaining the highest safety standards, as well as the secure management and disposal of nuclear waste, constitutes one of the main technological and social challenges associated with this form of energy production.
On the other hand, unlike the most widespread renewable energy sources today, such as solar and wind power, fission is not an intermittent source: it can provide energy continuously, without the need for energy storage systems or backup from fossil-fuel sources.
The nuclear reactor is the technologically complex system through which the energy released by fission is produced, controlled, and ultimately converted into usable electrical energy. Among the various types of reactors developed over the decades, the most widespread is the pressurized water reactor (PWR). In schematic terms, it consists of a containment structure, the core where fission reactions take place, heat-exchange systems, and the turbine generator unit for electricity production. This type of plant belongs to the so-called second- and third-generation nuclear reactors, including the so-called evolutionary reactors, or advanced third-generation reactors, featuring further improvements in safety.

Looking ahead, the reactors currently under study or under construction are the so-called advanced reactors, previously referred to as fourth-generation systems. These reactors are designed with the aim of maximizing the use of nuclear fuel, reducing and transmuting long-lived radioactive waste, and, in some cases, enabling the production of hydrogen.
Some prototypes or demonstration facilities are already in operation or under construction in countries such as Russia and China, or are in advanced stages of design also in Europe (including Italy) and the United States. These are complex infrastructures whose large-scale deployment is expected over long time horizons, starting from around 2040, as further research and development activities are still required.
In Italy, the first nuclear power plants for electricity generation were built starting in the 1960s, with the commissioning of the Latina plant, followed in subsequent years by other facilities across the national territory. The serious accident at Chernobyl in 1986 had a profound impact on the public and political debate on nuclear energy and led, the following year, to the calling of three national referendums on the sector. The outcome of these consultations subsequently resulted, at the political level, in the abandonment of nuclear power in Italy, a decision that progressively led to the shutdown of the three power plants that were still in operation at the time: Latina, Trino, and Caorso.
Since 1999, the sites of the Italian nuclear power plants have been owned by SOGIN (Società Gestione Impianti Nucleari), which is responsible for their management and decommissioning activities. These interventions concern not only the former nuclear power plants but also other nuclear facilities and complexes located throughout the country and are aimed at securing the sites and their progressive dismantling.

Latina Power Station - Exterior. @Sogin

In recent years, also considering the challenges associated with the energy transition and the reduction of greenhouse gas emissions, the issue of a possible return of nuclear energy within the Italian energy system has once again moved to the forefront of political, scientific, and cultural debate. This has fostered a broader reflection on the role of the different energy sources in the energy system of the future. Within this context, concrete developments have taken place at the institutional level.
In May 2023, the Chamber of Deputies approved a motion committing the Government to assess the role of nuclear energy within the framework of national energy policies. In June 2025, Italy officially became a member of the European Nuclear Alliance, an initiative aimed at promoting the role of nuclear power in the energy transition within the European Union. A further step in this direction was taken in October 2025, when the Council of ministers approved a draft enabling bill designed to provide an organic regulatory framework for the introduction of so-called “sustainable nuclear energy”, in line with the European objectives of decarbonisation by 2050 and energy security.
The measure, known as the “Disegno di legge Picchetto”, named after the Minister for the Environment and Energy Security, outlines a reference framework for a possible reintroduction of nuclear energy into the national energy mix, with particular attention to next-generation technologies. The enabling law provides for the development of a National Programme for Sustainable Nuclear Energy, the establishment of an independent Nuclear Safety Authority, the strengthening of scientific and industrial research, the training of new specialised skills, and the promotion of public information and awareness-raising activities.
The bill, however, defines a general framework, delegating its concrete implementation to a series of subsequent implementing decrees. For this reason, any operational developments are expected over medium- to long-term time horizons. From this perspective, the contribution of public research and dialogue among the scientific community, institutions, and civil society are essential elements for an informed and conscious assessment of future energy choices.

Image of the star-forming region N79 taken with MIRI, the James Webb Space Telescope's mid-infrared instrument. Credits: ESA/Webb, NASA & CSA, M. Meixner

This image from the NASA/ESA/CSA James Webb Space Telescope features an H II region in the Large Magellanic Cloud (LMC), a satellite galaxy of our Milky Way galaxy. This nebula, known as N79, is a region of interstellar atomic hydrogen that is ionised and is captured here by Webb’s Mid-InfraRed Instrument (MIRI).

Nuclear fusion

The goal of scientific research on nuclear fusion is to achieve a clean, safe, and potentially limitless source of energy by reproducing in the laboratory nuclear reactions similar to those that power the stars. For many years, fusion has been the subject of intense studies aimed at assessing its extraordinary potential as a future energy source. Once technological maturity is achieved, fusion will also be able to provide energy continuously, without the need for storage systems or backup from fossil-fuel sources. Moreover, it is based on materials that are widely available in nature, such as deuterium, which can be extracted from water, and lithium, which is abundant on Earth. Many believe that fusion could radically transform the energy paradigm, making a decisive contribution to European energy autonomy and thus acquiring strong strategic value.

To learn more, read the interview with Paola Batistoni, Italy’s representative on the governing board of the European agency Fusion for Energy, published in the latest issue of Particle Chronicle, the INFN newsletter, that is dedicated to nuclear fusion energy.

The main advantages of nuclear fusion reactors are essentially twofold: the ability to produce large amounts of clean energy from materials that are widely available in nature, and the generation of radioactive waste with significantly lower levels of radioactivity and much shorter decay times. However, the scientific and technological challenges that must be overcome to achieve an operational fusion reactor remain highly complex and require long development times, with prospects for industrial application not expected before the middle of the century. It should be noted, however, that over the past decade several industrial players worldwide have launched private fusion development programmes, claiming they can achieve commercial maturity on shorter timescales than those traditionally envisaged for this technology.
In nuclear fusion, energy is produced by the merging of two nuclei of very light elements, such as the hydrogen isotopes deuterium and tritium, which form a heavier nucleus while releasing a large amount of energy. For this process to occur, the fuel must be heated to extremely high temperatures, on the order of hundreds of millions of degrees, necessary to overcome the electrostatic repulsion between positively charged nuclei. This state of matter, known as plasma, cannot be contained by solid materials and therefore requires the development of advanced confinement technologies, which represent one of the main challenges of fusion research.

In the main experimental devices currently in operation or under construction, such as tokamaks, including ITER, under construction in France, and stellarators, such as Wendelstein 7-X in Germany, the plasma is confined by intense magnetic fields generated by large superconducting magnets. The development of these systems is closely linked to high-performance magnet technologies, an area in which the expertise developed in high-energy physics, particularly in particle accelerators such as the Large Hadron Collider (LHC) at CERN, plays a crucial role. Advanced superconducting materials, cryogenic techniques, and large-scale magnet engineering are in fact key elements for the success of fusion.
In the case of magnetic confinement, the approach that will be adopted by ITER, fusion is achieved at low plasma densities, long energy confinement times, and very high temperatures. These conditions are obtained by increasing the plasma temperature through the injection of neutral atoms and radio-frequency electromagnetic energy into very large plasma volumes.
In inertial confinement, by contrast, the ignition of the fusion reaction is pursued at very high densities, extremely short confinement times, fractions of a second, and within very small volumes, again at very high temperatures. This approach involves the use of small capsules, known as pellets, filled with fuel, which are compressed and heated by laser pulses, thereby triggering the fusion reaction. In this case, the process is extremely rapid, since the pellet is destroyed as the energy produced by the reaction is released.

The ITER Tokamak will be the largest device of its kind in the world, with a plasma volume of 840 m³. (© US ITER)

Spider ion source-ITER. Source: RFX

In recent years, investments and research programs in nuclear fusion have grown significantly worldwide, with the construction of large international experiments. Among these, ITER represents the leading global project in magnetic confinement fusion and aims to demonstrate the scientific and technological feasibility of a reactor capable of producing more energy than is required to sustain the plasma. As mentioned above, many industrial initiatives have recently emerged, often in the form of start-ups and mainly supported by private capital, with the goal of accelerating the development of fusion as a commercial technology for energy production.
INFN is not directly involved in the ITER project; however, it participates in the governing board of Fusion for Energy (F4E), the European agency responsible for promoting and coordinating all activities related to ITER, where it represents Italy together with ENEA. INFN is also involved as a member of the RFX consortium, based in Padua, in collaboration with which the Institute has carried out a study on the sources for the neutral beam injectors used to heat the plasma. RFX plays an important role in the realization of ITER by hosting the construction and testing activities of the reactor’s injectors, which involve two distinct devices: the SPIDER source and the MITICA injector, currently under construction, a replica of the systems that will be installed on ITER.

INFN is actively engaged in research and development activities in support of nuclear fusion, with particular attention to the infrastructures required for the qualification of materials intended for future reactors. Looking ahead, the DEMO reactor, the successor to ITER, will have to operate at higher power levels and will require components

This is the context for the IFMIF (International Fusion Materials Irradiation Facility) project, a facility dedicated to the study and qualification of materials for fusion, part of the collaboration between the European Union and Japan known as the Broader Approach. In its complete configuration, IFMIF will have two high-power deuterium ion accelerators and a liquid lithium target capable of producing a neutron flux with characteristics similar to those of future fusion reactors. As part of this project, the EVEDA prototype was developed, to which INFN contributed by supplying the radiofrequency quadrupole, installed in Japan and currently in an advanced stage of testing.

Installation of RFQs (Radio Frequency Quadrupoles) developed at the Legnaro National Laboratories for IFMIF (Rokkasho, Japan). ©INFN

The European IFMIF-DONES (Demo Oriented Neutron Source) initiative, promoted by the European Union for the qualification of materials intended for fusion reactors for energy production, is also part of this line of research. DONES will be based on a single IFMIF-type accelerator with a lithium target and will be located in Granada, Spain, with operations expected to start between 2034 and 2035.
Italy participates in the project’s Steering Committee and, as part of the activities coordinated by EUROfusion under the aegis of Euratom, INFN has contributed to the design of the accelerator, drawing on the experience gained with EVEDA. The DONES project is the subject of a bilateral agreement between Italy and Spain, under which INFN will contribute to the construction of the infrastructure by supplying the radiofrequency quadrupole and other components of the accelerator.

handling of the mechanical structure of the RFX-mod experiment

The DTT (Divertor Tokamak Test) project is positioned as an Italian-led initiative for the construction of an experimental demonstrator at the ENEA center in Frascati, in which INFN also participates as a shareholder of the company responsible for its realization. The main scientific objective of DTT is the study of the divertor, a key component of fusion reactors, often described as the “exhaust pipe” of the plasma, as it is responsible for preventing the quenching of the reaction by removing thermalized helium nuclei and impurities generated by the interaction between the plasma and the vacuum vessel walls.
INFN contributes to the project through several divisions and national laboratories, taking part in numerous activities, including the development of the acceleration section of the neutral beam injector, one of the main plasma heating systems. In this area, innovative additive manufacturing (3D printing) techniques are being applied.

The Institute also collaborates in the development of radio-frequency systems, which are likewise essential for achieving the temperatures required to trigger fusion, as well as in the development of advanced diagnostics for studying the physical behavior of the plasma. For these activities, INFN leverages the experience gained in experiments such as PANDORA, dedicated to the study of nuclear reactions in plasmas, as well as the expertise developed in the field of additive manufacturing.

Finally, INFN is also active in the field of inertial fusion. Commission 5, which coordinates the Institute’s technological research and the development of applications, has funded the FUSION project, dedicated to the development of innovative techniques for inertial confinement fusion, in collaboration with ENEA and several universities. These activities have been further strengthened through the COST Action ProBono and will continue with the HiPER+RF project, recently approved as an “Enabling Research” initiative within EUROfusion. HiPER+RF aims at the conceptual design of a new European infrastructure for laser fusion. Within this framework, INFN’s contribution focuses in particular on the development of advanced plasma diagnostics, computational models for ion energy loss in plasmas, and the future availability of the I-LUCE laser system for measurements of physical quantities and for the systematic study of nuclear reactions in plasmas.
Taken together, these activities testify the INFN’s contribution to the development of nuclear energy technologies, both in the field of fusion and in that of next-generation fission, in collaboration with research organizations such as ENEA and with the university system. The expertise developed in fundamental research finds application in areas of strategic relevance, such as plant safety, fuel cycle management, radioactive waste treatment, and the decommissioning of existing facilities. INFN has dedicated the strategic project INFN-E to this set of activities, framing and enhancing the Institute’s contribution to the development of nuclear energy technologies.

a cura di Ufficio Comunicazione INFN – COMUNICAZIONE ISTITUZIONALE E MEDIA