4. METHOD OF SOLUTION
The analysis approach involves calculation of vessel failure pressures using fracture mechanics methods and estimation of pressure-transient characteristics using historical nuclear data.
The pressure vessel is described by input data, such as vessel wall thickness, inside radius, copper and phosphorus content, residual stress, flaw sizes, fluence, and temperature. The failure pressure for a given flaw is calculated using linear-elastic and elastic-plastic methods. After obtaining the failure pressure for a given flaw size, the probability evaluation is performed. The probabilities for the different flow sizes are then summed to obtain the total probability of pressure vessel failure from the various flaws which might exist in the vessel.