Abstract
Due to increasing demand of Electricity, every country in the world wants to construct more and more nuclear power plants and apply different advance techniques for accident prevention, safety and reliability. Probabilistic Safety Assessment (PSA) and Living Probabilistic Safety Assessment (LPSA) are two of them, which are presented in this review paper. The paper consists of four parts, in first part latest application of PSA, in second part definitions and methodology of LPSA, in third part risk monitoring and in fourth part comparison between these three, has been described.