Experiment on the increase of the burn-up fraction of fuel assemblies in VVER-440 reactor

The rated fuel lifetime in a standard VVER-440 reactor includes three partial fuel rechargings). One way of intensifying the fuel use is to increase the number of partial reactor rechargings with a simultaneous increase of the full fuel lifetime. This mode of fuel use makes it possible to raise the fuel burn-up fraction. Two conditions, however, should be met. First, the number of the recharged fuel assemblies (FA) should make it possible to retain a rated number of fuel rechargings during the calendar year of operation, and, second, operational reliability level of the fuel elements should not be exceeded as a result of an increase of the nuclear fuel lifetime. Theoretical studies of various fuel-use ways in the VVER-440 reactor were made. They involved an increased number of partial rechargings with a simultaneous increases of fuel lifetime and specified the quantitative parameters of a fuel cycle consistent with these conditions. The studies showed that for intensifying the fuel use in commercial NPS containing VVER-440 reactors it is appropriate to increase the number of partial reactor rechargings from three to four with a simultaneous decrease of the number of recharged FA from 102 to 78. The design duration of a fuelmore » cycle with the rated fresh fuel enrichment amounts to 255 eff. days. This fuel-use mode makes it possible to increase the burn-up fraction of unloaded fuel by 13.3% in comparison with the rated value and, as a result of this, to decrease the fuel component of electric power cost, to reduce natural uranium consumption, and to cut down separation man-hours in the external fuel cycle.« less