Analysis of a delayed return to full power using a three-dimensional simulator

For optimal operation of a power plant, it is now necessary to install an expert system in the control room, particularly to aid the operator in predicting, following, and explaining operating events. The three-dimensional MICROLUX code, foreseen for such a system, was tested on an operating event occurring in the Doel-3 reactor. After an --6-h scram, the return to full-power (P/sub N/) was limited at 15% P/sub N/ because of an unacceptable axial offset deviation, which was believed to have been caused by xenon buildup during the shutdown. The reactor was then required to be operated at reduced power for 18 h before again reaching nominal power. From the study, however, it seems that there was no danger in returning directly to full power in spite of the ex-core indications. The three-dimensional calculations and the ex-core results show that there is a need to investigate the ex-core/in-core relationship when the reactor is operated outside the calibration field. These preliminary results indicate that the axial offset concept should be analyzed on the basis of a large number of transient operating conditions with the help of three-dimensional methods, which give a better description of the core behavior during transients. The use ofmore » such methods could contribute to a safer and more economical operation of the reactor.« less