[en] It was decided to use FLIP fuel (70 % enrichment in U235) - against the world tendency to reduce enrichment- because we already had 46 fresh FLIP fuels available in the facility and almost non of the standard type. In order to better use the fuel we had at that time, we decided to find a load scheme that better suited that purpose, we could use 46 FLIP fuel elements no irradiated and about 120 irradiated standard fuel elements. We use EXTERMINATOR to analize several options. We studied the burnup of the reactor core consisting of the two types of fuel, the total numbers of fuel elements was kept constant 85 to compare directly the results. The numbers of inserted FLIP elements was adjusted trying to get realistic core excess reactivity (about 6 $) and trying not to complicate power shapes mixing the two types of fuel in one ring. We selected two of them that were analized in more detail. The first one we called 8th configuration used all 46 FLIP elements placed in ring C, D and E with 59 irradiated standard elements filling the other positions, and the 9th configuration using 26 FLIP fuel elements in rings C and D with irradiated standard fuel completing the load. In both cases the three burned control rods were sustituted with new FLIP follower control rods. After some rough calculations we decided to drop the 8th configuration because we were concerned with the shoutdown margin of that configuration. After we loaded the fuel and performed rod worth measurements we finded out that we were subestimating the worth in our calculations. (author)