Nuclear energy in Argentina

Having been the first country in Latin America to have a Nuclear Power Plant, Argentina is facing today the final arrangements for its Life Extension Project: Atucha I.

It is not the first time that Nucleoeléctrica Argentina, the company that operates the three Argentinian nuclear power plants, Atucha I, Embalse and Atucha II, has to face such a major challenge. It has already accomplished the construction of Atucha II in 2014 and the Life Extension Project of Embalse between 2016 and 2019.

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The different nuclear reactors in Argentina

Embalse

This Nuclear Power plant is located in Embalse, in the province of Córdoba, and it is a PHWR (pressurized heavy water reactor) designed by CANDU. Not only does Embalse generate electricity by fission, but also the isotope Cobalt 60, which is used in nuclear medicine.

Embalse has been granted an initial operation license from the Nuclear Regulatory Authority until 2015. Nevertheless, Nucleoeléctrica Argentina has reached the extension of this license for another thirty years.

The Embalse Life Extension Project represented an enormous challenge for Nucleoeléctrica Argentina, given all the modifications that were necessary to improve the safety and modernize the Nuclear Power Plant.

Some of the projects that stand out are:

- The replacement of the steam generators, the pressure tubes and the low pressure turbines.

- An additional preheater was added to increase electrical power with the corresponding turbine steam extraction.

Atucha I and II?

Atucha I and II are located in Lima, in the province of Buenos Aires. These nuclear reactors are prototypes of pressurized heavy water reactors (PHWR) from KWU Siemens, where the nuclear fuel is slightly enriched uranium (0.85%) and natural uranium, respectively. Although heavy water serves as both the heat transfer fluid and the moderator, they operate at different temperatures. .

The image below shows the reactor vessel which bears a striking resemblance to that of pressurized water reactors (PWRs). However, it differs from PWRs in having filler bodies at the top and bottom, their purpose is to reduce the amount of heavy water. The control rods are inclined due to the online change of fuel assemblies which are vertically arranged.

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Another difference between these plants and pressurized water reactors is that they improve the efficiency of the installation by exchanging heat between the moderator circuit and the secondary circuit. In this way, the moderator cools down, reducing its density and helping to moderate the neutrons. On the other hand, the steam from the secondary circuit reaches a higher temperature before entering the steam generators, which means that the temperature difference is less pronounced to reach saturation temperature.

Atucha I Life Extension Project

?After almost fifty years of operation, Nucleoeléctrica Argentina is ready to take on this new challenge that will enable it to continue the production of clean energy during its second phase of operation, which will last twenty-five years at full power. To achieve it, engineers and technicians have learned from Embalse's feedback and replicated several measures and protocols.

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Among the modifications made to improve nuclear safety, and therefore mandatory at the request of the ARN (Nuclear Regulatory Authority), are the following :

-??????? The incorporation of the "Feed and Bleed" system, which involves changing the pressurizer valves.

-??????? Verification of "Consequential Failure" for a common cause and the concept of rupture for the plant's compliance with current standards, linked to the study of possible failures and the modifications required to resolve them and improve nuclear safety.

-??????? Changing the filters in the safety injection system (it is important to note that this system does not inject boron, as there is a separate safety system that does so more quickly).

-??????? Modernisation of the reactors safety I&C system, for which Framatome will supply the Teleperm XS technology.

-??????? Construction of a secondary control room.

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To carry out modifications such as the replacement of filters, it is essential to chemically decontaminate the moderator system heat exchangers, which will be performed by Framatome.

Several projects are underway, including replacing low-pressure turbines, developing a control room simulator with Tecnatom, and the layup of systems and equipment. The latter will involve the dosing of Framatome's film-forming amine Octadecylamine (ODA).

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