2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/189402We develop the general tools for model building with orientifolds, including SS supersymmetry breaking. In this paper, we work out the general formulae of the tadpole conditions for a class of non supersymmetric orientifold models of type IIB string theory compactified on $T^6$, based on the general properties of the orientifold group elements. By solving the tadpoles we obtain the general anomaly free massless spectrum.35 pages, 3 eps figures, Latex2eHigh Energy Physics - Theorytext