Argentina’s nuclear utility Nucleoeléctrica SA (NA-SA) says unit 2 of the Atucha NPP has restarted operation after completing a successful repair, which it described as “without precedent in the world”.
Atucha II had been closed since October 2022 when a vibration was detected inside the reactor causing one of four supports (spacers) to fall to the bottom of the reactor. The repairs are estimated to cost $2-4m. NA-SA said this did not represent a threat to the safety of the plant, but compromised its operation. The damaged 10cm-long component was in an inaccessible part of the reactor and a special mechanical arm had to be developed to help to remove it.
NA-SA extracted the detached spacer from a depth of 14 metres inside the reactor using engineering tools and procedures designed and manufactured by the company together with local suppliers. The remaining spacers were then reinforced the fixed in place.
The special tools designed for the procedure included a cutting tool, cutting base, holding tool, gripper, the design of a basket to hold the component and extract it and the design of a lighting and vision tool to be able to monitor the manoeuvre. It was also necessary to develop a pressure welding tool and a method to preventatively weld and strengthen the three remaining spacers.
The tools and repair methods were tested on a full-scale model (mock-up) of the relevant sector of the reactor. The Nuclear Regulatory Authority ARN reviewed and approval of all the proposed designs and manoeuvres.
NA-SA said the solution allowed the plant to be repaired remotely without the need to dismantle the reactor, as recommended by the original designer, which made it possible to shorten repair times from four years to ten months.
“The completion of this challenge not only marks a new milestone for the Argentine nuclear industry, but also confirms the country's scientific-technological capabilities to carry out complex engineering projects,” NA-SA noted. “In this way, the experience acquired by Nucleoeléctrica in this repair will allow the country to export knowledge and tools for use in other nuclear power plants in the world.”
Argentine Secretary of Energy Flavia Royo said on Twitter [now X] “I want to congratulate the workers of Nucleoeléctrica for the work they carried out in record time”. She added: “The solution implemented by Nucleoeléctrica consisted of carrying out the repair remotely, through the holes for loading and unloading fuel from the reactor, without the need to disassemble it.”
Argentina has three pressurised heavy water reactors – Atucha I, Atucha II and Embalse – with a total generating capacity of 1,641 MWe which provide 9% of electricity generation. Atucha I, which began construction in June 1968, was the first NPP in Argentina and Latin America. Currently, it has a gross power of 362 MWe. The reactor uses heavy water as coolant and moderator, and 0.85% slightly enriched uranium as fuel. Construction of Atucha II began in 1981 as a joint venture of CNEA and Siemens-Kraftwerk Union but work was suspended in 1994 with the plant 81% complete. It was restarted in 2006 and was first connected to the grid in 2014 starting commercial operation in 2016.
Image: Atucha II (courtesy of Nucleoeléctrica Argentina)
