[en] Three methods generally are used to establish the reliability of primary components of reactors, e.g. reactor pressure vessels. These methods are based on the fracture mechanics approach, which combines the three essential parameters; stresses, material and defects. The first method is the deterministic method and establishes safety factors by dividing the minimum resistance by the maximum load. The second method is the probabilistic method and establishes reliability factors by combining probability density functions of resistance and load. The third method is the combination of the two methods and relates the deterministic safety factors to the probabilistic reliability factors. Examples of these three methods are given. (author)