An analytical method for leak before break assessment based upon stochastic fracture mechanics

An analytical method is proposed for probabilistic assessment of LBB in piping systems based upon stochastic fracture mechanics. Basically, we follow the assumptions such that: (i) The surface crack propagation can be decomposed into surface and depth directions, (ii) the well-known Paris' law is applicable to each direction, (iii) the Newman-Raju's expression is applicable for the stress intensity factor of the surface crack. First, by taking into account the randomness of material's property and loading, a probability density function of random surface crack propagation is derived with the aid of a Markov approximation method. Next, discussion is made on how we apply the result to the probabilitic LBB assessment. (orig.)