Materials and Components From Npp Decommissioning: Opportunities of Investigation by Neutron techniques (pp. 107-122)
Authors: Massimo Rogante
Abstract: Lifetime prolongation and safety are key issues in planning and management of Nuclear Power Plants (NPPs), as knowledge of materials’ conditions and related ageing processes is necessary either to ensure high levels of dependability or to deal with severe natural and plant–centred events. Conventional investigations, nevertheless, can present a lack of information, thus the data obtained require to be complemented.
Decommissioning is not only a mere activity of installation’s conclusion, but also an important opportunity to get materials, parts and worked systems submitted for decades to degradation and ageing. In dismantling a NPP, so, new diagnostic activities and measures for the installation of new components can be suggested to enhance safety and reliability of NPPs.
Neutron investigations have lately become a progressively more considerable probe across a wide range of disciplines and they can reveal important properties about materials. Neutrons are becoming ever more helpful in the non–destructive characterisation of industrial materials and components of nuclear/traditional interests: applications of neutron–based methods, moreover, are being developed in a range of new sectors [1, 2].
In this paper, the following neutron techniques are briefly described, which can be exploited in the NPP field: small angle neutron scattering (SANS) for the micro- and nano-structural characterization as well as the radiation damage assessment; neutron diffraction (ND) for the determination of internal and sub–surface residual stresses (RS); prompt gamma activation analysis (PGAA) for qualitative and quantitative analyses of the material’s constitutive main and trace elements. Some applications are also described. The available results, together with those from comparisons between naturally aged, new (non-aged) components and reference basic materials, can permit investigating in a supplementary way NPPs parts, helping to increase safety levels and service life of nuclear installations, with remarkable positive impact by either environmental or economical point of view.