Atucha (Argentina)

Map of Atucha

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Atucha is located some 100 km Northwest from Buenos Aires City.

Unit-1 with a net electric power of 335 MW, began its commercial operation in 1974. The reactor is of PHWR type. According to the original design Atucha-I is fuelled with natural uranium. Fuel elements of a new design have been incorporated, having slightly enriched uranium (0.85 % w U-235), so that the reactor core is now partly loaded with slightly enriched fuel, and partly with natural uranium fuel. Atucha-1 was constructed by KWU.

Safety analyses showed the need of adapting CNA-I emergency cooling system, designed during the late sixties, to the present nuclear safety criteria. This produced a series of requirements on the basis of an improving and updating (backfitting) program for the installation. A program for the progressive replacement of all the fuel channels is implemented. Other backfits had to be carried out related with the optimisation of radiological protection.

Construction of a second unit has been interrupted, CNA-II has a net electric power of 693 MW, and is being built near CNA-I. It was also conceived as a PHWR type reactor, natural uranium fuelled and heavy water moderated and cooled.

In June 2014, the new reactor at the Atucha nuclear power plant was put online.

Facilities in Atucha

plantreactor typconstruction startoperation startshut down

Failure during a test of the emergency boron injection system: A valve was left open which led to spillage of heavy water. The affected valve is always open- except during testing.


Atucha-1was shut down to repair fuel bearing pressure channels. Rising temperatures in the moderator caused low reactivity. Unit was manually shut down. No damage detected, so it was restarted again: but operators were unable to maintain power levels: oscillations and increasing reactivity -> so the unit was shut down again. One fuel element had been broken and damaged the pressure channell. Six surrounding channels were damaged,too. Some fuel pellets and other debris was found in the reactor vessel. Repair lasted 17 month. Station has been plagued by operating and technical problems since 1987. Operating at reduced power for only 3 of the past 16 months. Later reports say : A broken sensor line caused the damage, by creating turbulence and oscillations of the guide tube, which broke and began knocking against the pressure tube. During the outage the moderator level instrumentation of which the broken sensor line was a part, was replaced. Utility plans to clean and repair the reactor without removing the pressure vessel lid and heavy water. A lengthy procedure recommended by Atucha-1's vendor Siemens/KWU. Siemens' repair plan would have delayed startup for another 15 month and cost US $15 million, against the US$ 5 million actually spent. Siemens questioned Argentina's repair because it did not fully conform with accepted Western safety standards.