485atw Vol. 59 (2014) Issue 8/9 | August/September

Inside Nuclear with NucNet

Areva, Westinghouse and Rosatom as re-actor suppliers.First the government must refine nuclear legislation, define the nuclear regulatory body and contract siting studies for the first nuclear plant.

NucNet: Are you cooperating with Ar-gentina – a neighbouring country with years of experience in nuclear energy – or any other state for the development of the technology?Fernando Sierpe: Chile has signed agree-ments of cooperation with a number of countries including the US, France, Japan, Russia, Argentina and Brazil. Many Chile-

Fernando Sierpe is a member of the Association of Engineers of Chile, an autonomous institution which advises the government on matters related to engineering projects. Mr Sierpe is head of the association’s nuclear pow-er committee, which drew up the ‘Nu-clear Power Plants Development in Chile, 2009-2030’ report in 2009.

an nuclear specialists have followed courses in the US, Europe, Argentina and Brazil. The Association of Engineers of Chile’s nu-clear power committee has excellent rela-tions with organisations such as the IAEA, the Economic Commission for Europe (UN-ECE) and the Iberoamerican Programme of Science and Tecnology for Development (CYTED). These organisations, with our nuclear power committee, held the Inter-re-gional IAEA-UNECE-CYTED Workshop on Uranium and Thorium, in Santiago de Chile, in June 2013. It was attended by 60 delegates and specialists from 40 countries. Also, we have close relations with Chile’s Ministry of Energy, the governmental Comi-

sion Chilena de Energía Nuclear, the Chile Commission on Nuclear Energy, and sever-al Chilean universities which are being at-tracted by nuclear energy.

Nuclear Power Plant Operation

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NPP Atucha I: 40 Years of Commercial Operation of the Heavy-water Reactor in ArgentinaHermann-O. Fabian, Erlangen/Germany, and Oscar A. Mazzantini, Atucha/Argentina

Addresses of the Authors:Dr. Hermann-O. Fabian

Franzosenweg 6191058 Erlangen/Germany

Ing. Oscar A. MazzantiniUG-CAN II, Manager Licensing and Safety

Nuclearelectrica Argentina SAAtucha, Argentina

The nuclear power plant (NPP) Atucha I in Argentina – a heavy-water reactor with pressure vessel technology operated with natural uranium – accomplished a remark-able anniversary on 26 June 2014: 40 years of commercial operation. State-run Nucle-oelectrica Argentina SA (NA SA), being to-day the plant owner and operator com-memorated this anniversary with pride, as

only few NPP exist which can refer to such long operating time with good perfor-mance.

With a limited operating licence to 40 years (or rather 32 full load years) by the National Atomic Energy Agency (Comision National de Energia Atomica/CNEA) the plant had been handed over to CNEA on 24 June 1974 by the general contractor, Sie-mens AG, after release of the works con-tract on 1 June 1968.

The site is located to the north-west of Buenos Aires upstream on the Rio Parana. The plant has an output of 345 MW; it has been continuously, reliable and successfully operated and only interrupted due to larger repair measures on the generator trans-former (1976/1977), refurbishments inside the core area (1988/89 and 1999 to 2002) and remedy of malfunctions of compo-nents. Atucha I supplied overall 82.4 TWh

of electricity into the national grid (220 kV) with an integral operating availa-bility of 76.5 % [1].

This extraordinary performance over the long operating period highlights a good operation management and staff qualification of the NA SA dealing with the heavy-water reactor plant, as well as the qualified, reliable and solid design and technology of the plant developed, con-structed and put to operation by Siemens. Large scales of Argentinean personnel, as well as the national industry with substan-tial supply of individual components and systems were involved in the construction measures.

The plant Atucha I is the first NPP in Lat-in America and at the same time the first NPP export order for the manufactur Sie-mens. For both parties these were coura-geous and far-reaching decisions. To sup-port the order a bilateral cooperation con-tract for a peaceful usage of nuclear energy was concluded between both partner com-panies in 1969.

The tender put in by the Argentinean authority for the construction of a NPP back then gathered worldwide interest and led to a multitude of offers with different reactor types. Besides the PWR (pressur-ised water reactor), Siemens also offered the heavy-water variation in pressure-ves-sel design with natural uranium as fuel and heavy-water being moderator and coolant. (PHWR or “Schwerwasserreak-tor” in German)

The plant technology – details on the technology of Atucha I see [2] – is basically similar in both types, so that know–how from development, construction and oper-ation from previous plants in Germany with comparable plant construction and

486 atw Vol. 59 (2014) Issue 8/9 | August/September

Nuclear Power Plant Operation

large components as well as valid criteria for the design of safety arrangements of the PWR were taken as reference.

Different are fuel, the separation of moderator and coolant and the exchange mechanism of fuel elements, which can be exchanged or replaced during operation. The latter has been successfully tested and practised at the Multi-purpose Research Reactor (MZFR/50 MW) in Karls-ruhe/Germany built by Siemens. Thus an in-creased flexibility in operation of the reac-tor plant is achieved.

Important long-term overall economic considerations for the decision in favour of a natural uranium reactor resulted from:• Direct use of natural uranium as fuel, • Independent of enrichment and repro-

cessing,• National production of fuel elements

(FE),• Better fuel utilisation,• Flexible operation with higher availa-

bility through online FE-exchange,• Costs and currency savings.

The plant and system technology of Atu-cha I were continuously optimised and im-proved in terms of safety through accumu-lated experiences from Atucha itself and from international findings. Outstanding were:• The construction of a second fuel pool

building in order to receive and store spent fuel elements at the site.

• The construction of a completely inde-pendent, redundant and diverse second heat sink for a secure heat removal over the steam generator in case of acci-dents.

• Exchange of the complete emergency diesel generator system with 3 x 100 % diesel generators to improve and secure the emergency power supply.

• Improvement measures in the field of fire protection.

• Inspection of design after incidents in external plants such as Three Mile Island 2 (TMI) and Fukushima with implemen-tation of relevant improvements.

The successful operation of the plant and supervision measures, such as e.g. the ac-companied tracking of material embrittle-ment (especially of the reactor pressure vessel) led to the recognition, that an ex-tension of the plant operating time could be taken into consideration, even up to the

Milestones of plant Atucha I:• 07/1967 Submission of offers for the CNEA announced NPP in Argentina;

international contribution with different reactor types• 02/1968 LOI handed over to Siemens as general contractor for planning,

constructing, assembling and commissioning a natural uranium heavy-water plant in Atucha with an execution time of 49 months.

• 06/1968 Contract between CNEA and Siemens for the construction of the plant• 03/1969 Bilateral contract between Germany and Argentina for a cooperation in

research and development on the nuclear energy sector for its peaceful usage

• 06/1974 Handover of the Atucha I plant to CNEA by Siemens• 12/1976 Damage on the machine transformer due to lightning strike• 1977 Plant power increase by 8.2 % up to 345/367 MWe (net/gross),

of 1,190 MWth• 1977 Integration of Atucha I into the IAEA safeguard-standards (International

Atomic Energy Agency)• 1980 Construction of a second pool building for storage of spent fuel

elements (FE)• 1981 National Argentinean (CNEA) – German (BMI) cooperation for the safety

of nuclear facilities with technology transfer for the NPP construction• 1981 LOI/ Commission of Siemens/KWU for the construction of Atucha II with

technology transfer• 08/1988 Plant shutdown due to malfunction in the core area. Refurbishment of

several core components carried out by CNEA personnel• 07/1990 Plant reset to 100 % -operation • 1999 to 2002 Performance reduction due to control rod optimisation• 06/2014 40 years of commercial operation of the plant Atucha I • 2014 Consideration of extending the operating time

View of the Atucha nuclear power plant site with Atucha I in the foreground and Atucha II (under construction) in the background (Photo: NA SA).

accomplishment of the approved 32 years of full load in 2017 and under some cir-cumstances even far beyond. An operation beyond requires nevertheless necessary life-extending measures as well as safety-relevant supplements, which are currently discussed due to their scope and expense.

The Argentinian – German cooperation on national basis as well as the positive ex-perience from managing and operating Atucha I led to the commission of Siemens/KWU for constructing a second but double sized PHWR identical plant at the site of Atucha (LOI 1981). The capacity-wise stronger but technologically and design-wise identical sister plant Atucha II (745 MWe) is, in the meantime, already far pro-gressed in its construction and start up. The plant is currently in the nuclear start up stage; first criticality has been reached on 3 June 2014. After having meanwhile successfully performed the commissioning phase at 50 % power level it is to be expect-ed that the plant will be put to commercial operation in the 4th quarter of this year, af-ter having successfully tested several per-formance levels.

[1] IAEA/PRIS: IAEA – Power Reactor Infor-mation System

[2] “ATOM UND STROM“-Sonderdruck KWU, Das Kernkraftwerk Atucha, G. Her-zog und K.-J. Sauerwald, 15. Jg. / Heft 4/ April 1969