Using Carleman's inequalities, shown valid in reflexive Orlicz spaces by P.Nowosad and the author in previous work, certain properties of integral operators completely of finite double norm acting on these spaces are proved. The main results are: a form of Schur's inequatily, completeness of the set of generalized functions for certain operators and the annihilation of the trace of T 2 for cuasi-nilpotent operators T. These generalize known results in the case of Hilbert-Schmidt operators on Hilbert Spaces.