Sema Group Plc last month presented what it and client Electricite de France say is a world first – a fully computerised command and control room for the first of the electricity generator’s new generation nuclear reactors. The two were careful, however, to draw the distinction between computerised and automated of the new control centre at EDF’s 1,450-MW N4 nuclear reactor Chooz B on the Franco-Belgian border, which should be on-line within the next six months. The command and control room of Chooz B is not more automatic than other control rooms, said Jean-Claude Legendre, chief of the Chooz B project for EDF. The level of automation has hardly changed since the introduction of the REP reactors (same generation, previous models). The idea is just to give the operators more information, better presented, he said. The idea for the system came from Three Mile Island in Pennsylvania, where the operators didn’t have enough information about what was going on or what they should do, said Pierre Bacher, an EDF executive at the presentation. The operator has complete priority of his actions. When he follows the recommended course of action, he has to go through several steps, answering yes or no. The system can only override the operator if it’s in disagreement, Bacher added cautiously. The system actually gives us an extra check over what we had with paper, said control room operator Cecile Bardin, She added that it also put the necessary information under her fingertips, whereas she used to have to search through manuals to find out what an alarm indicator meant and what she had to do. The system is organised into four levels. Level 0 is the power plant itself and its devices (reactor, steam generators), actuators (motors, pumps) and sensors (temperature, pressure, flux). Level 1 is programmable logic controllers performing automatic safety and regulation functions and interfacing the installations with the plant control room. Level 2 is computers and operator stations, processing data from Levels 1 and 3 and providing the man-machine interface. Level 3 is unit supervision resources, interfacing with external systems (national dispatching centre, maintenance and test aids, national crisis centre). Data is sent from Level 0, with its 12,000 sensors to the programmable logic controllers at Level 1, where they are checked, processed and sent to the Level 2 computers.
Global view of the reactor
The computers analyse the data in terms of historical or pre-determined values, archives them and formats them for clear presentation to the operator. In a contract worth about $200,000, Sema Group was responsible for Level 2, part of Level 1 and communications between the different subassemblies and with external systems (Level 3). The control room comprises four identical operator stations, for two plant operators, one plant manager and one safety engineer. Each operator has a detailed view of one part of the reactor, said Jean-Marc Miraucourt, associate project manager. Then the room has a global view of the reactor posted to prevent them getting locked into their own corner. Miraucourt noted that the operators always have the same interface, whether the system is in a normal or emergency state. With an alarm, the system issues a list of what must be done, with a graphic that enables the operator to localise the problem. The list is generated from an existing technical documentation database, while the graphic reflects the actual state of the reactor. Electricite de France defined the functional and ergonomic requirements for the command and control room, as well as the elaboration of data and applications for the database. Pierre Juguet, head of energy sector activity for Sema, said the system is the biggest of its kind in the world, monitoring and controlling 35,000 devices and parameters, issuing 19,000 digital instructions with a run-time of less than half a second, and 10,000 technical data sheets and 4,000 data alarm sheets. Sema chose Ada as the development language and 17 VAX 4000s from Dig
ital Equipment Corp to run the system. -Marsha Johnston
