Chapter 2Literature ReviewQuantitative Risk Assessment (QRA) and related techniques have been developed in the aerospace, electronics, and nuclear power industries. In these sectors it is called Probabilistic Security Assessment, PSA, or Probabilistic Risk Assessment, PRA. In the 1970s and 1980s, the application of this method in the process industry began. The Canvey study (HSE 1978, 1981) and the Rijnmond study (Rijnmond Public Authority, 1982) are some good examples of its application. The quantitative risk assessment was developed by TNO Defense Security and Safety (the Netherlands). van der Voort et al. (2007) used this tool for the first time for the external safety of industrial plants with a risk of dust explosion. They divided the industrial plant into modules and then discovered the explosion scenarios with their frequency. They then calculated the consequences for external objects and humans, followed by calculating risk contours and social risk (FN curve). Zhiyong, Xiangmin, and Jianxin (2010) presented a case study of a hydrogen refueling station where QRA methodology was applied to calculate the potential risk exposure of people present in the station. They assessed risk exposure for staff working at the stations, for customers arriving for refueling and for third parties, also considering individual risk and social risk for the risk assessment. It turned out that the compressor leak was the main cause of the risks. To reduce occupancy risk, compressor augmentation has been proposed as an effective mitigation measure for station personnel. For customers the risk could be minimized by raising the compressors or placing fences around the compressors. The same measurements could be... in the middle of the paper... and the fault tolerance could be identified. (Liu & Chiou, 1997) focused on using Petri nets for fault analysis instead of fault trees. They devised a trapezoidal graphical method to account for failure scenarios. Until then it was assumed that the probability of the basic events of a Petri net occurring was constant, but in reality they may have different failure rates. Taking this into account (Adamyan et al., 2002) extended the work by using the Petri net to model complex processes such as failure analysis of a robotic manufacturing cell. Then a new approach was proposed by (Reza, Pimple, Krishna, & Hildle, 2009). They showed how using Petri nets and fault tree analysis, both forward and backward reachability analyzes related to acceptable and unacceptable system behaviors are performed taking a railway crossing system case study as an example.