The generation and the propagation of radiation induced single event transients (SET) in CMOS circuits are evaluated. An accurate and computer efficient analytical model for SET generation and propagation is proposed. The model allows the rapid determination of the sensitivity of any MOS circuit node to SET, without the need to run circuit level simulations. The model predicts whether or not a particle hit generates a transient pulse which may propagate to the next logic gate or memory element. Electrical masking of the transient pulse as it propagates through each stage of logic until it reaches a memory element is also modeled. The proposed approach is suitable for integration into CAD-tools, intending to make automated evaluation of circuit sensitivity to SEU possible