The failure of stress corrosion fraction (SCF) will lead to the

ejection of nuclear power plant related equipment, which will

affect the safety and economy of nuclear power plant. In this

paper, a SCF failure analysis method for primary coolant circuits

materials was established based on Paris model, and the

uncertainty of fracture toughness was transformed into an

integral form to improve the calculation efficiency. Taking the

weld of thermowell as an example, the probability of SCF failure

was calculated, and the uncertainty was analyzed by Wilks’

method. The influences of simple random sampling (SRS), Latin

hypercube sampling (LHS) and Halton low discrepancy

sequence on the uncertainty quantification of the calculated

results were studied. At the same time, a surrogate model was

established based on polynomial chaos expansion (PCE) method

to study whether this method was suitable for SCF probability

calculation. The results show that Halton sequence with 1000

samples can make the mean and variance convergence of failure

probability better than SRS and LHS. When calculating the

upper limit of tolerance interval, the mean and median of results

corresponding to LHS are similar to those of SRS, but the

dispersion degree of LHS is lower than SRS, while the results

corresponding to Halton sequence are smaller than those

corresponding to SRS and LHS. The increase of Wilks’ order can

reduce the conservatism. When the order is 4, both the

computational efficiency and the computational accuracy are

considered. The results of the surrogate model based on PCE are

basically consistent with those of the original program, but the

amount of calculation is greatly reduced. This method is suitable

for SCF probability analysis.