The plant is controlled by a microprocessor based distributed system with a redundant communication network. The critical functions of the system required for the plant to operate, are also duplicated.

The protection system, also based in microprocessors, uses a minimum of programmable actions. The software is written directly in machine language (assembler), with a strong effort made to keep it extremely simple. Apart from these small pieces of software, the protection system is "hard".

These features are similar to most recent designs of non-integrated PWRs: they are not a particular characteristic of integrated reactors but a new trend in nuclear power plant design.

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The CAREM reactor uses hydraulic control rod drives. This type of rods are wholly contained in the pressure vessel, carrying the concept of integration one step further.

A sketch of its functioning is included. Rods are kept in position by water flow. A positive flow pulse causes the rods to climb one step, while a negative flow pulse causes the rods to go down one step. If water flow is suddenly interrupted, the rods, in a fail safe action, are dropped into the core. The water, after passing through the drives, is dumped into the primary system, inside the pressure vessel. The main advantage of this type of drive is that it can fit in the volume available inside the pressure vessel of an integrated reactor. The use of conventional electromagnetic control rod drives would require a higher containment.

The protection system is able to trigger a scram using a built in valve, that causes the rods to fall by gravity.

However, the

drives are designed in a fail safe way: rods will fall automatically in the event of a plant black-out or in a loss of coolant accident, due to the interruption of the water flow through the drives, without requiring a trip from the protection system.