Time filter

Source Type

Civitanova Marche, Italy

Rogante M.,Rogante Engineering Office
International Journal of Energy, Environment and Economics | Year: 2012

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. © 2012 Nova Science Publishers, Inc.

Rogante M.,Rogante Engineering Office | Mikula P.,Nuclear Physics Institute of Czech Republic | Vrana M.,Nuclear Physics Institute of Czech Republic
Key Engineering Materials | Year: 2014

Thermal neutrons are very useful probe in a nondestructive determination of internal stress/strains, due to their high penetration into most materials. In comparison with conventional X-ray techniques, real bulk information on both macro- and micro-strains in materials can be obtained by neutron diffraction (ND) techniques. Knowledge of the spatial and directional distribution of internal residual stresses (RS) is increasingly considered fundamental to determine their influence on properties of engineering materials and a consequent material behaviour. As the assesment of stresses is always related to the stress free material state, an accurate evaluation of the unstressed lattice parameters (e.g., the interplanar distance), in order to determine RS by ND is one of the key tasks. It helps to avoid inacceptable errors in the course of the real material strain and stress evaluation. The availability of carefully measured zero-strain standards is also essential to confirm the absence of systematic instrumental effects determining the diffraction profile at a chosen scattering angle. In this paper, the state of the art of the main analytical and experimental procedures currently established or adoptable to determine these critical parameters, particularly regarding industrial applications, is presented. © (2014) Trans Tech Publications.

Rogante M.,Rogante Engineering Office | Mazzanti M.,Fiat Powertrain Technologies S.p.A. | Mikula P.,Nuclear Physics Institute of Czech Republic | Vrana M.,Nuclear Physics Institute of Czech Republic
Kovove Materialy | Year: 2012

The residual stresses (RS) induced in the substrate by case hardening treatment (HT) play a significant role in the behaviour of power train engineering components. In this paper, the results of RS investigation by neutron diffraction (ND) in 20NiCrMo2 steel car gear-shafts are presented. The RS were measured in correspondence of the critical region (notch) which is sensitive to fatigue-stress and/or crack, namely before/after a hardening treatment and after the successive finishing process. The achieved results can supply useful information on the effects of the various manufacturing processes on the RS status, better to evaluate the extent of distortion before and after the hardening treatment and to give a substantial support in the life assessment of the considered components. Furthermore, these results can yield parameters exploitable in monitoring of the hardening treatment characteristics, thereby confirming the relevance of thermal stresses induced by the same hardening treatment.

Rogante M.,Rogante Engineering Office | Lebedev V.T.,RAS Petersburg Nuclear Physics Institute
Journal of Alloys and Compounds | Year: 2012

Udimet 520 and Udimet 720 samples submitted to different annealing temperatures and ageing times have been investigated by small angle neutron scattering (SANS), with the aim to study precipitates phases microstructural evolution and materials' behaviour. These materials are γ′ (Ni 3Al, Ti) precipitation hardened nickel-based superalloys possessing high strength, corrosion resistance and metallurgical stability. They are mainly adopted in high temperature environment, having found applications over a very wide range of temperature. Their importance has increased thanks to their good balance of mechanical properties and economic potential. Information on the thermal treatment effects has been obtained, in particular concerning precipitate size and volume fraction distributions. The results contribute to confirm SANS to a level of industrial applicability in the considered sectors. © 2011 Elsevier B.V. All rights reserved.

Rogante M.,Rogante Engineering Office | Pasquini U.,Azienda U.S.L. | Rosta L.,Hungarian Academy of Sciences | Lebedev V.,RAS Petersburg Nuclear Physics Institute
Physica B: Condensed Matter | Year: 2011

In this paper, neutron techniques in particular, small angle neutron scattering (SANS) and neutron diffraction (ND) are considered for the non-destructive characterization of Nitinol artery stents. This roughly equiatomic (50Ni50Ti at%) shape memory alloy (SMA) exhibits significant properties of superelasticity and biocompatibility that make it suitable to be typically used as smart material for medical implants and devices. Nitinol self-expanding artery stents, as permanent vascular support structures, supply an ideal option to bypass surgery, but they are submitted for the whole of patient's life to the dynamical stress of the artery pulsation and the aggression from the biological environment. These stents, consequently, can suffer from wear and fracture occurrence likely due to a variety of cyclic fatigue, overload conditions and residual stresses. Neutrons have recently become a progressively more important probe for various materials and components and they allow achieving information complementary to those obtained from the traditional microstructural analyses. The outputs from the preliminary works already carried out in this field consent to consider neutron techniques capable to contribute to the development of these crucial medical implants. The achievable results can yield trends adoptable in monitoring of the stent features. © 2010 Elsevier B.V. All rights reserved.

Discover hidden collaborations