\subsection{Objective}
LBE composition evolution depends on the irradiation during the operation and the following decay. Since the particle fluxes vary depending on the zone of the reactor also the depletion of the coolant will be affected by the position. The central zone of the core, near to the spallation target is characterized by high energy proton flux and a high energy neutron spectrum up to 200 MeV, since the neutrons are generated from spallation reactions in the target from incoming protons at high energy. This means is this region spallation and activation products with high energy treshold will be generated. Outside the spallation target assembly there is a negligible proton fluence since charged particles have a limited mean free path in the matter before being absorbed. The neutron spectrum is still fast with upper bound determined by the neutrons emitted by fission and the peak in the epithermal region. The main depletion mechanism of the LBE in the core is nuclide activation by fast neutron spectrum. In the pool neutron spectrum is much softer because of the distance from the neutron source (spallation, fission) and the thermalization of the neutrons in the reactor components. In this case low energy activation reactions are the more effective.\\
The main objective for the LBE source term is to assess the impact of zone division on the nuclide vector $N (t)$, comparing with a model in which homogeneous depletion is performed at reactor level. The limit of the transport/depletion model is the circulation of the LBE in the reactor, bringing to continuous mixing of the coolant that cannot be reproduced by our models. 