At a time when many NPPs are considering reforms to prolong their lifetime and renew their operating licenses, INVAP offers its services for NPP maintenance and repair of Nuclear Power Plants.
Beginning with Argentine NPPs, INVAP supplied engineering and equipment for the maintenance of the heat exchangers of the primary circuit at Atucha-1 NPP (CNA-1). Atucha-1 is a natural-uranium burning NPP of medium power.

We are now offering this service worldwide, including engineering, renewal of instrumentation and control systems, the issuing and qualification of procedures and the construction of a simulator to qualify these equipments and procedures. The provision includes training programs for operators and supervisors.

The following is an example: the work was done on the Atucha-1 NPP, of Nucleoelectrica Argentina SA.

REMA-I

The highly radioactive environment in which such work is done, often implies the development of special tools. In the case of Argentina´s first NPP, the set of automatic or semiautomatic machines and tools designed to work at a distance were known as REMA-I - REpair and MAintenance. REMA-I was conceived to work in areas either difficult to access or in radioactive environments.

In this case, the remotely controlled system was specially designed to repair and maintain the heat transfer units in the primary cooling circuit at the nuclear power plant Atucha-1 (CNA-1)

Site characteristics

These heat exchangers are located in the primary cooling circuit of CNA-1. They keep the average temperature in the circuit low; they are 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 places. Since they are the coolest point of the primary cooling system, they are 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.

Main purpose of the maintenance and repair jobs.

Chores like cleaning, inspection and perhaps, when needed, the blocking of the exchanger tubes to extend the plant's useful life.

The criteria applied are: to keep radiation doses to the intervening personnel as low as possible (ALARA - As Low As Reasonably Achievable), to changes the facility as little as compatible with the aim to be achieved, and the installation of redundant systems when needed.

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 being prepared for use
• Master-slave manipulators and transfer carts ensure the correct manipulation of tools and replacement 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