Modelling of Americium and Curium Transmutation in Molybdenum and Magnesia Targets in the Experimental ADS MYRRHA

The results of assessment of the transmutation performances of two experimental channels situated in the active and reflector zones of ADS MYRRHA, under design at SCK•CEN, are presented. Evolution of the composition of two types of the IMF targets: one with MgO matrix and another with Mo matrix, both containing the incorporated (Pu0.4Am0.6Cm0.1)O1.88 fuel, are modelled during the irradiation period of about three years (810 EFPD), followed by a storage period of three years. Dependence of the actinide composition on time is practically the same in both IMF(Mo) and IMF(MgO) targets, but neutron multiplication performance of the fuel cell with the first is 30 % lower. A higher disappearance of americium in the targets disposed in the reflector zone channel (-1.63 g cm-3) is penalised by a relatively high build-up of curium (+0.41 g cm-3 at the end of the irradiation). The long-life isotopes 245Cm and 246Cm present about 80 % of the built-up curium. Less than +0.1 g cm-3 amounts the curium increment after irradiation in the targets placed in the active zone channel; it becomes 7 times smaller after the storage period.