Approach and methodology for condition assessment of thermal reactor pressure vessels

• Published in: International journal of pressure vessels and piping 1993, Vol.54 (1), p.49-87
• Main Authors: English, C.A., Fudge, A.J., McElroy, R.J., Phythian, W.J., Buswell, J.T., Bolton, C.J., Heffer, P.J.H., Jones, R.B., Williams, T.J.
• Format: Article
• Language: English
• Subjects: Activation energy; Applied sciences; Atomic force microscopy; Atoms; Correlation; Damage; Dosage; Electron microscopy; Embrittlement; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Exposure; Fission nuclear power plants; Fracture toughness; Impact tests; Installations for energy generation and conversion: thermal and electrical energy; Materials testing; Mathematical models; Mechanical properties; Metals. Metallurgy; Microchemistry; Neutron scattering; Neutrons; Nuclear reactors; Piping; Pressure vessels; Q1; Reactors
• ISSN: 0308-0161; 1879-3541
• DOI: 10.1016/0308-0161(93)90127-F

In this paper we review the approach employed in the UK to characterise the embrittlement of thermal reactor pressure vessels (RPVs). The experimental techniques developed to characterise the neutron energy spectrum and fluence are described; these include the use of multifoil activation packs and a direct damage monitor. The techniques for the retrospective assessment of the exposure of service irradiated components and the methods for the prediction of end-of-life doses in RPVs are discussed. Displacements per atom (dpa) is the main exposure and correlation parameter employed and the success of using it to measure damage dose is evaluated. A variety of techniques is used to characterise the changes in mechanical properties in both materials test reactors and power reactors. These include fracture toughness, Charpy impact and tensile testing. Mechanical properties inter-relationships are particularly helpful when evaluating the condition of irradiated materials; the Charpy-tensile, Charpy-hardness and Charpy-fracture toughness correlations are reviewed. An important aspect of research into materials behaviour in the UK has been the development of mechanistic models of the embrittlement phenomena. These models have been reasonably successful in the interpretation of embrittlement in copper-containing materials, particularly in rationalising data obtained at different dose rates. The approaches are summarised. Microstructural techniques based on transmission electron microscopy, small angle neutron scattering and atom probe/field ion microscopy have been developed to characterise the microstructure and microchemistry of unirradiated and irradiated copper-containing materials. The contributions these techniques have made to the understanding and prediction of embrittlement processes are described.