International experiences with radiation embrittlement assessment of outdated reactor pressure vessels

The analysis of radiation-induced material deterioration in the vessel wall is an essential basis for the brittle fracture safety analysis of reactor pressure vessels. The analysis of the embrittlement state of pressure vessels of older reactor design types cannot correspond in all points to the requirements of the series of nuclear engineering codes presently in effect. One of the reasons for this is missing information, especially on the chemical composition and the mechanical/technological characteristics. On the other hand, it has to do with deviations from present standards with regard to production and quality assurance. The resulting problems and uncertainties in evaluating the state of embrittlement of older plants will be discussed on the basis of an assessment of the national and international technical literature. The paper shows the necessary for an extensive technical discussion as a means of evaluating the present information on radiation and gaining a better understanding of the processes of radiation-induced deterioration. (orig.)