OLev System Hazard Analysis ETA Evaluation Events trees are better at handling ordering of events but fault trees better at identifying and simplifying event scenarios Practical only when events can be ordered in time(chronology of events is stable)and events are independent of each other Most useful when have a protection system Can become exceedingly complex and require simplication Separate tree required for each initiating event Difficult to represent interactions between events Difficult to consider effects of multiple initiating events Defining functions across top of event tree and their order is difficult Depends on being able to define set of initiating events that will produce all important accident sequences Probably most useful in nuclear power plants where all risk associated with one hazard (serious overheating of fuel) designs are fairly standard large reliance on protection systems and shutdown systemsLeveson − 149,150 System Hazard Analysis c ETA Evaluation Events trees are better at handling ordering of events but fault trees better at identifying and simplifying event scenarios. Practical only when events can be ordered in time (chronology of events is stable) and events are independent of each other. Most useful when have a protection system. Can become exceedingly complex and require simplication. Separate tree required for each initiating event. Difficult to represent interactions between events Difficult to consider effects of multiple initiating events. Defining functions across top of event tree and their order is difficult. Depends on being able to define set of initiating events that will produce all important accident sequences. Probably most useful in nuclear power plants where all risk associated with one hazard (serious overheating of fuel) designs are fairly standard large reliance on protection systems and shutdown systems