The set of automatic or semiautomatic machines and tools designed to work at a distance is known as REMA-I - REpair and MAintenance. REMA-I was conceived to work in areas either difficult to access or in radioactive environments.

The remote controlled system was specially designed to repair and maintain the coolers in the primary cooling circuit at the nuclear power plant Atucha-1 (CNA-1)

Working within the plan for the assistance to Argentine nuclear power plants, INVAP was responsible for the turn-key supply of the necessary engineering and equipment for the maintenance of the heat exchangers of the primary circuit at Atucha-1.

The scope of provision included the engineering, the set of tools and the provision of automation and control systems, the issuance and qualification of procedures and the construction of a simulator to qualify the equipment and procedures. The provision included a training program for operators and supervisors.

For the development of the project, INVAP had the specialized cooperation of Nucleoeléctrica Argentina S.A. and of the Argentine National Commission of Atomic Energy (CNEA) thus ensuring a desirable breadth of criteria while capitalizing on previously gained experience.

The coolers are heat exchangers located in the primary cooling circuit of CNA-1. These coolers are of utmost importance because they keep the average temperature in the circuit down, they are a part of the core cooling chain during stoppage and they supply heat to the thermal cycle of the generators.

The coolers constitute one of the plant's most radioactive points. This is due to their being the coolest point of the primary cooling system, to their being subject to normal fouling, to the existence of cobalt in reactor materials and to the accumulation of particles in the heavy water inlet.

The area where maintenance and repair work must be carried out, is cramped and difficult to access. An ensemble of specially designed tools is mandatory, operated by highly trained and specialized personnel.

The aim of the exercise is to carry out chores of maintenance such as cleaning, inspection and perhaps, when needed, the blocking of the exchanger tubes to extend the plant's useful life.

The criteria applied were: radiation doses to the intervening personnel as low as possible (ALARA - As Low As Reasonably Achievable), changes in the facility as few as possible, and the duplication of methods to achieve the desired aims.

REMA-I has equipped Atucha-1 with complete set of maintenance and repair tools and so has reduced the time of stoppages and thus plant availability has increased.

REMA-1 features the following benefits.

• It maximizes the resources for remote control and supervision of the operation.
• It improves access to the work area
• By means of adequate shielding, it provides a protected area where the set of tools is made ready
• Master-slave manipulators and transfer carts ensure the correct manipulation of tools and parts
• It provides welding and cutting tools so the operation and control of these procedures are carried out remotely
• The system includes complementary tools and accessories including accessories for inspection, radio-protection, video-system etc.
• It provides for the use of special newly designed bolts that are installed by means of a hydraulic tightener
• It provides a simulator used for the training of personnel and procedure qualification