Fracture Initiation Aspects of the Loss of Coolant Accident for Water Cooled Nuclear Reactor Pressure Vessels

摘要

This study reviews the influence of certain important variables, namely coolng fluid temperature, flaw shape and size, wall thickness, vessel radius, cladding, heat transfer coefficient, fluence, and time following a loss of coolant accident (LOCA) on the tendency of preexistent flaws in a reactor vessel to propagate due tothe activation of the emergency core cooling system following a LOCA. Based on this analysis, it is concluded that under certain combinations of the variables investigated situations exist where the calculated stress intensity at ta preexisting crack exceeds the static initiation toughness. Although a number of single variables have a strong influence on critical crack growth cooling water temperature has been found to be a most important factor in assessing the propensity for crack growth. On the other hand, proof of crack arrest could provide a satisfactory solution to the problem. Analytical and experimental studies are recommended to obtain stress intensity factors leading to initiation of crack growth and to establish the validity of crack arrest.