  The concept of the LAr TPC technology that is an excellent tracking -
calorimeter detector will be used for the next generations of neutrino
experiments. In this class of detectors both the scintillation light emitted
and the charge produced by the ionization are used to detect and identify the
characteristics of the primary particle. The reduction of the radioactive
background, the knowledge of the sources and mechanisms of its production as
well as the characteristics of the signals have as consequence the increase of
the sensitivity of huge detectors and the capability to discriminate between
various particles interacting with the detector. Cosmogenic sources of
background or activation of different materials become more important in this
context. The radioactivity induced by cosmogenic reactions in Ar is discussed
by considering muon capture and reactions induced by neutrons as sources of
background. The simulated cross sections for the considered nuclear reactions
are obtained using TALYS and EMPIRE codes, highlighting the similarities and
differences between the results of these nuclear codes and the level of
concordance with the few existing experimental data.
