Results from Recent Experiments at the LOTUS Facility

Under the ongoing experimental program of fusion neutronics at the LOTUS facility, a number of activation and tritium breeding measurements were recently completed. The presence of the Lithium Blanket Module (LBM) made a number of measurements also possible in it alone and in a number of more complex assemblies, incorporating it as one of the components. The foil activations were done in the following assemblies: (a) 6, 12 and 18 cm thick single Be slabs, (b) 5, 10 and 15 cm thick Pb slabs, (c) 27.7cm thick ThO₂ slab, (d) 27.7cm ThO₂ + 80cm thick LBM, (e) 5cm Pb + 27.7cm ThO₂ + LBM, (f) 6cm Be + 27.7cm ThO₂ + LBM. Only five activation reactions were measured : ⁹⁰Zr(n,2n), ⁵⁸Ni(n,2n), ⁹³Nb(n,2n), ⁵⁸Ni(n,p) and ¹¹⁵In(n,n′). The tritium breeding measurements were conducted in three assemblies : (i) LBM, (ii) 5cm Pb + LBM, (iii) 6cm Be + LBM. Both axial and off-axis measurements were made. All the experiments have been analyzed using the two dimensional discrete ordinates code DOT3.5 coupled to the first collision source evaluator GRTUNCL. The agreement between the measured and computed reaction rates is better than 10% for ThO₂; it is not so good for others.