Assessing current condition as regards to fracture toughness is an integral part of setting operational limits and re-licensing requirements for nucelar reactor pressure vessels. The fracture toughness of reactor pressure vessel steels degrades with irradiation and therefore the current condition must be assessed based on surveillance speciments that have been inthe ractor since initial construction. But these specimens are limited in number. Thus fracture safety assessment must rely on a limited number of data points to characterize the current impact toughness. which is then correlated to the current fracture toughness transition temperature as defiend by the Code of Federal Regulation (10CFR50.61). This method tends to be conservative and inaccurate because it relies on a harpy V-notch transition temperature-to-fracture toughness transition temperature correlation instead of actual fracture toughenss measurements.
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