[en] This manual describes the use of the Set Equation Transformation System (SETS) to perform the accident sequence analysis portion of a probabilistic risk assessment (PRA) for a nuclear power plant. Other tasks in a PRA provide the input to the accident sequence analysis task. The SETS computer program is used to process these inputs to identify the dominant failure modes and to compute an approximate frequency of occurrence for an accident sequence. The use of SETS for each step in an accident sequence analysis is described and an example SETS user program is provided for each step