After several years of technical work, inspections, and fine-tuning, the Atucha II nuclear power plant has started working again maximum power capacityThe plant, located in Lima, Zárate district, received authorization from the regulator to operate again at full capacity and contribute all its energy to the Argentine electrical system.
The return to 100% power It marks the end of a period of more than seven years in which the facility worked with operational limitations due to a problem detected in the primary circuit. With the formal authorization of Nuclear Regulatory Authority (ARN)Atucha II returns to his full role as a central defender in the National Interconnected Systemproviding continuous and predictable generation.
Regulatory authorization and return to nominal power
As reported Nucleoeléctrica Argentina SA (NA-SA), the company responsible for the Atucha I, Atucha II and Embalse power plants, the ARN enabled Atucha II to reach its capacity again nominal power of 745 MW grossThis permit was granted after a verification process in which corrective work, technical tests, and new control systems implemented at the plant were evaluated.
According to official sources, the central It returned to operating at 100% power On January 14 at 19:20 p.m., following a gradual increase monitored by the regulatory body. The plant had been operating since October 2025 at around 97% of its capacity, as a preliminary step towards full recovery.
The president of Nucleoeléctrica, Demian ReidelHe noted that the power plant even showed a value of 100,2% in its power indicatorsThis generated some public curiosity. Reidel clarified that this number does not represent a dangerous excess, but rather corresponds to the concept of nominal power as a reference value100% is the optimal design point, and a small tolerance margin is allowed without affecting the safety or lifespan of the reactor.
In that regard, he explained that they work with an operational range of approximately 100% ± 0,5%As long as the power remains within these limits, the operation is considered normal and no permanent corrections are made, avoiding unnecessary wear on the reactor's control mechanisms.
The return to full capacity of Atucha II reinforces the role of the nuclear energy as baseload power generation, less exposed to the climatic oscillations that affect renewables and the hydrological variability of hydroelectric power plants.
The origin of the problem and the years of limited operation
The power restriction that plagued Atucha II dated back to 2018 late, when the company detected a progressive decrease in electrical power and an increase in the cooling system outlet temperature. This anomalous behavior pointed to a reduction in flow rate of heavy water in the primary circuit, responsible for moderating the chain reaction and cooling the reactor core.
Upon analyzing the interior of the reactor, the technical teams found debris or metal shavings in the combustible elementsIt was later determined that those remains came from the rupture of the shaft sleeve of one of the pumps in the primary circuit, which caused premature wear on the lower carbon bearing of the pump.
The company identified that the underlying cause was in a design flaw acknowledged by the manufacturer The pump, which had been recommended for replacement after the installation's pressure testing phase, was not replaced at the time, nor was it communicated to the operator as a pending task for the first scheduled shutdown, which ultimately led to the problem that was detected.
To avoid greater risks, Nucleoeléctrica decided manually remove the service center and design an intervention plan. Following the inspection and the definition of the repair strategy, Atucha II It resumed commercial operations in February 2019but under a scheme of reduced power, in which safety was prioritized over maximum generation.
During those years, the plant operated with restrictions thanks to the development of specific calculation programs These tests allowed researchers to predict the reactor's cooling behavior in the presence of impurities in the system. This tool was key to demonstrating that energy could continue to be generated safely while the final solutions were being designed and implemented.
Corrective works and safety improvements at Atucha II
The return to full power was not the result of a single isolated intervention, but of sustained work of multidisciplinary teams from Nucleoeléctrica and other technical bodies. The company implemented a complex plan of corrective actions aimed at both resolving the original problem and strengthen security and reliability of the central office in the face of similar events in the future.
Among the key measures are the comprehensive inspection and repair of the affected pump, as well as the replacing the shirts with an improved design which corrects the identified defect. This engineering change aims to reduce the risk of generating new metallic debris in the primary circuit.
In addition, they were installed filters in the reactor at the fuel element positionsThe goal is to capture and extract any metallic debris that might appear. This additional barrier acts as a defense-in-depth system, minimizing the possibility of foreign particles affecting the coolant flow or damaging the core components.
The power plant also incorporated a online monitoring system of the primary system to detect variations in activity that may be associated with failures in fuel elements. This real-time monitoring allows identify problems in early stages and act before they result in a significant loss of power or a risk to the integrity of the reactor.
Another key point was the implementation of specific alarms for flow drops in the primary circuit, along with detailed measurement of the heavy water flow in the cooling channels. These mechanisms provide operators with accurate information regarding any changes in the reactor's hydraulic regime.
As part of the validation process, a hydraulic simulator (mock-up) at the Centro Atomico ConstituyentesThis allowed for the reproduction of operating conditions and the testing of solutions in a controlled environment. This testbed was fundamental in supporting the engineering decisions with experimental data and in demonstrating to the ARN that the plant could resume operations with complete safety.
This entire set of actions, supervised at each stage by the regulator, culminated in the authorization to operate again at 100% powerconsolidating Atucha II as a strategic piece of the Argentine nuclear park.
Impact on electricity generation and role as baseload energy
The full recovery of Atucha II comes in a context of sustained growth of nuclear power generation in the country. Nucleoeléctrica Argentina linked in 2024 and 2025 successive annual production records, with a net generation of around 10,76 million MWh last year, a figure that represented approximately 7,5% of the national electricity demand.
Within that performance, Atucha II played a particularly important role, with a production that exceeded 5,4 million net MWh, above its previous all-time high recorded in 2016. With the plant now enabled to continuously deliver its nominal power, this contribution is expected to consolidate and even improve in the coming years.
Nuclear energy is thus positioned as a stable complement to renewablescapable of operating independently of fluctuations in wind, solar radiation, or hydrological availability. This baseload generation capability is key in electrical systems that seek reduce carbon emissions without sacrificing security of supply.
In practice, having a power plant like Atucha II operating at full capacity implies having a firm block of 745 MW gross Operating continuously, it helps alleviate pressure on other generation sources during peak demand. This stability is especially valuable in extreme heat or consumption peaks, where the system's robustness is put to the test.
From an economic point of view, the greater availability of nuclear energy can also contribute to reduce the need for fossil fuels for thermal generation, moderating exposure to the volatility of international gas and oil prices and reducing the outflow of foreign currency.
Growth of nuclear fuel and autonomy of the nuclear fleet
The recovery of Atucha II is taking place in parallel with significant progress in the nuclear fuel cycleThe state-owned company Dioxitek, which handles a key stage in uranium processing, reported that during 2025 it reached a production of 190 tons of nuclear-grade uranium dioxide, the largest volume since its creation in 1996.
This production milestone is the result of a process of internal reorganization, administrative streamlining, and industrial optimization at its Córdoba plant. Through improvements in each phase of the physical-chemical process, the efficiency of the technical staff was increased and the company's capacity to supply fuel to the Argentine nuclear fleet was consolidated.
190 tons of uranium dioxide allow you to project a scenario of self-sufficiency in fuel for the Atucha I, Atucha II, and Embalse nuclear power plants. In this way, Argentina reduces or even avoids importing a highly specialized input, with a direct impact on foreign exchange savings and energy security.
Dioxitek's industrial process transforms raw materials such as yellow cake and other by-products in ceramic quality uranium dioxide powderThis material is used to manufacture the pellets that make up the fuel elements, which are later loaded into power reactors.
Combining a power plant like Atucha II operating at 100% and a local fuel supplier with a production record strengthens a technological sovereignty scheme rare worldwide: the comprehensive mastery of nuclear technology for peaceful purposes, from the mineral to the massive generation of electricity.
New political impetus for the Argentine nuclear sector
The full operational return of Atucha II is part of a stage in which the Argentine Government has decided to give renewed prominence to nuclear energy within its energy strategy. Under the motto of having “More nuclear energy to power the country’s future”The Executive has presented the sector as a pillar to support electricity demand and economic growth.
In 2024, the so-called Argentine Nuclear PlanUnder the leadership of Demian Reidel, who also heads Nucleoeléctrica Argentina, the plan aims to... streamline the sector, correct incentives, and improve economic returns of the public investments made in the national nuclear complex.
In addition, there was the creation of the Secretariat of Nuclear Affairs, under the Ministry of Economy and headed by Federico Ramos Napoli. This new institutional structure aims to coordinate the long-term nuclear strategyintegrating aspects of power generation, industry, research and medical applications.
In this context, the full availability of Atucha II is interpreted as a sign of system robustness and as practical support for the policy of maintaining and enhancing existing strategic infrastructure. The sector closed 2025 with technical and productive advances relevant, which reinforce the idea that nuclear energy continues to be a pillar for the country's economic and industrial development.
At the same time, the good performance of the power plants and the record fuel production provide a solid basis for discussing, with data in hand, the role of nuclear energy in the transition to lower carbon matrices, both in Argentina and in other regions of the world that observe these developments as a reference.
The combination of a Atucha II operating again at 100% powerA strengthened fuel supply chain and a political framework that once again views nuclear energy as a strategic asset paint a picture in which Argentina's nuclear fleet gains weight in meeting electricity demand, consolidates its contribution as baseload energy, and positions itself as a regional example of how technical continuity and long-term planning can translate into greater energy security and autonomy.
