  We present a new algorithm for the identification and physical
characterization of current sheets and reconnection sites in 2D and 3D large
scale relativisticmagnetohydrodynamic numerical simulations. This has been
implemented in the PLUTO code and tested in the cases of a single current
sheet, a 2D jet and a 3D unstable plasma column. Its main features are: a) a
computational cost which allows its use in large scale simulations; b) the
capability to deal with complex 2D and 3D structures of the reconnection sites.
In the performed simulations, we identify the computational cells that are part
of a current sheet by a measure of the gradient of the magnetic field along
different directions. Lagrangian particles, which follow the fluid, are used to
sample plasma parameters before entering the reconnection sites that form
during the evolution of the different configurations considered. Specifically,
we track the distributions of the magnetization parameter $\sigma$ and the
thermal to magnetic pressure ratio $\beta$ that - according to particle-in-cell
simulation results - control the properties of particle acceleration in
magnetic reconnection regions. Despite the initial conditions of the
simulations were not chosen "ad hoc", the 3D simulation returns results
suitable for efficient particle acceleration and realistic non-thermal particle
distributions.
