Regulator's safety goal for Atucha Long-Term Operation project

05 June 2024

Argentina's Nuclear Regulatory Authority (Autoridad Regulatoria Nuclear, ARN) says that planned upgrades and improvements to allow a 20-year extension to the Atucha I nuclear power unit will "raise the design basis of the facility to a higher level of safety than that with which it was originally licensed".

Atucha I has operated for 50 years so far (Image: Nucleoelectrica)

Operator Nucleoelectrica is to embark on an extended reconditioning shutdown of the unit, beginning this year, which is expected to last two or three years in total. The ARN said, in an update on the Long-Term Operation (LTO) project, that the improvements "will result in a nuclear power plant with safety characteristics superior to the original design. The selection of these improvements was defined based on extensive evaluations required and reviewed by the ARN, taking into account the impact on safety, their applicability and their justification in relation to the design of the plant".

Atucha I, a 362 MWe pressurised heavy water reactor, entered commercial operation in 1974 and had a design life in its operating licence of 32 equivalent years of full power. The first extension, with an amendment to the operating licence, began in 2018 when that 32-year mark was reached.

ARN said during this first extension phase that Nucleoelectrica "had to carry out studies and establish programmes that would ensure ... that the systems and components adequately preserve the functionalities for which they were designed, thus guaranteeing operation under the safety conditions with which the plant was licensed. The studies and maintenance tasks necessary to meet this requirement had to obtain approval from the ARN".

The duration of the amended operating licence was for the equivalent of 5 years operation at full power, or 10 years from 2014, whichever came first, although both are now set to fall within months of each other. The ARN says that Nucleoelectrica has asked to be able to operate Atucha I until the 10-year limit, which would be 29 September this year, and the regulator says in its update that it is currently considering the request.

The next stage of the LTO will be the extended shutdown during which it will "verify in detail the implementation of the updates and improvements required ... to raise the design bases of the facility to a higher level of security than that with which it was originally licensed", the ARN says.

Atucha I was designed and built by KWU, which was a joint venture of Germany's Siemens and AEG. Over time, KWU was fully owned by Siemens, before being sold to the reactor business of France's Areva which is now owned by EDF and trading as Framatome. However, Argentina now has an experienced supply chain of its own for pressurised heavy water reactors, having completed and brought into operation the similar Atucha 2 reactor in 2016.

It has become increasingly common for pressurised heavy water reactors like Atucha I to undergo refurbishment, which typically involves replacing pressure tubes and fuel channels, to enable another two decades of operation. Nucleoeléctrica Argentina says that 2000 jobs would be created during the extension project as it modernised "all the processes and systems of the plant". It has put the refurbishment programme's cost at USD463 million and held fundraising rounds last year to cover the cost of both the life extension project and construction of a dry storage facility for used fuel.

Argentina has three nuclear power reactors - the two at Atucha plus the Embalse nuclear power plant - which generate about 5% of its electricity. It also has its own pilot small modular reactor - CAREM - under construction.

Researched and written by World Nuclear News