Systematic approach to predicting corrosion of zirconium alloys in the water coolant of nuclear reactors

A method of semiempirical prediction of corrosion of cladding zirconium alloys as a function of the operating conditions and composition is presented. The laws of thermodynamics and chemical kinetics of the oxidation reactions of a multicomponent zirconium alloy form the physicochemical basis of the computational method. The method is based on a model developed at the All-Russia Research and Design Institute of Integrated Power Technology for the corrosion of commercial and experimental zirconium alloys in water media under autoclave and reactor conditions taking account of the composition of the alloy and the water chemistry. The model is verified on the basis of independent tests performed on a series of zirconium alloys under autoclave and reactor conditions. The method developed makes it possible to predict the corrosion of fuel-element cladding made from zirconium alloys with fuel burnup to 80 MW·days/kg under the conditions of one- and two-phase VVER and RBMK coolant.     

Accurate quantitative CF-LIBS analysis of both major and minor elements in alloys via iterative correction of plasma temperature and spectral intensity

The chemical composition of alloys directly determines their mechanical behaviors and application fields.Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality control and material classification processes.A quantitative calibration-free laser-induced breakdown spectroscopy (CF-LIBS) analysis method,which carries out combined correction of plasma temperature and spectral intensity by using a secondorder iterative algorithm and two boundary standard samples,is proposed to realize accurate composition measurements.Experimental results show that,compared to conventional CF-LIBS analysis,the relative errors for major elements Cu and Zn and minor element Pb in the copperlead alloys has been reduced from 12％,26％ and 32％ to 1.8％,2.7％ and 13.4％,respectively.The measurement accuracy for all elements has been improved substantially.     

强流脉冲离子束辐照对钛合金显微组织的影响

为研究强流辐照过程中钛合金微观组织结构和化学成分的变化,利用束流成分70%H+和30%C+的混合强脉冲离子束对钛合金进行了表面轰击,对离子束诱发的显微组织形貌和化学成分在扫描电子显微镜(SEM)上进行分析。结果表明,钛合金内部组织由α和β两相构成,为α+β型两相钛合金。试样不同区域组织类型存在明显差异,大部分区域组织类型一致,局部区域属于典型的魏氏组织。强流辐照钛合金表层组织和微观结构发生一定的变化,边缘β相结构遭到一定程度的破坏。显微组织结构的变化是由于表层温度梯度引起的热应力及其在靶材体内的传播造成的。     

Microstructural examination of several commercial alloys neutron irradiated to 100 dpa

Fusion reactor design to an integrated first wall loading of 40 MW/y/m² or 500 dpa, produces extreme demands on structural materials. It is very difficult to conceive of material behavior at such high damage level. In an effort to assess the consequences of such damage, a series of commercial alloy specimens have been examined following irradiation with fast neutrons to doses on the order of 100 dpa (20% of goal fluence) at 400°C, 425°C or 540°C. The alloys were iron or nickel based and included ferritic (martensitic) and austenitic alloys. Examinations incorporated transmission electron microscopy and analytical electron microscopy of irradiated specimens. Microstructural examination confirm that ferritic alloys are very low swelling, but precipitate development can be very complex. Austenitic alloys can be very high swelling but no clearly defined microstructural differences were found between two alloys of similar composition but very different swelling response or between alloys of very different composition but with similar levels of swelling. Differences are ascribed to differences in the onset of swelling.     

EDXRF and micro-EDXRF studies of Late Bronze Age metallurgical productions from Canedotes (Portugal)

Metallurgical production in Central Portugal during the Late Bronze Age was primarily based on copper-tin alloys, despite influences from the Atlantic area where copper-tin-lead alloys are common. Metallic artefacts from archaeological site of Canedotes (Central Portugal) were analysed by EDXRF to establish the type of alloys present. Polished spots in selected artefacts were also analysed by micro-EDXRF to determine the major and minor elemental composition of the original alloys. The collection constitutes 18 copper-tin artefacts and one unalloyed copper artefact with tin and arsenic as minor constituents. Artefacts that require a thermomechanical finishing process, such as tools and weapons, seem to have improved control over the tin content. The composition of two buttons, one cramp and one metallic droplet suggest that some of the copper sources were rich in arsenic. Finally, the low iron content of the artefacts seems to agree well with the smelting of copper ores in crucible furnaces, a smelting process used in certain areas of the Iberian Peninsula until pre-Roman times.     

A PIXE mini-beam setup at the bonn cyclotron for archeometric metal analyses

The exact analysis of the elemental composition at and around a soldering joint of an antique piece of jewelry can elucidate the joining technologies and give hints of the genuineness of the object. As analytical method we use PIXE, which is nondestructive, multielemental and with fundamental parameter calculations gives absolute concentration values. To obtain the necessary spot size of the H₂⁺ beam at the Bonn cyclotron we use a piezo-controlled diaphragm, whose demagnified image is focussed on the target by two magnetic quadrupole triplets. With an electrostatic deflector the beam spot of 0.1 × 0.3 mm² size can be moved 2 mm in each direction on the target. With a laser beam, which simulates the ion beam, an irregularly shaped archeological object can be positioned. The laser is also used to obtain the alignment of the target surface to the ion beam direction and the small beam size makes it easier to find a flat part on the surface of the object; both of these are important preconditions for using the fundamental parameter method. A scan over a joint of modern gold alloys demonstrates the ability to detect soldering joints. The analysis of four pieces of Roman gold jewelry found in the area of Cologne and Bonn shows examples of brazing with a solder as well as diffusion soldering.     

锆合金耐腐蚀性能研究综述

锆合金主要用作核反应堆燃料元件的包壳材料及其他堆内构件。回顾了有关锆合金水侧腐蚀的主要研究结果及存在的问题，概括了现有的理论及面临的挑战。８０年代，关于锆合金化学成分、微观结构及辐照对耐腐蚀性能影响的研究取得了很大进展。近几年来的研究工作主要集中在探索腐蚀机理、选择最佳合金成分及控制微观结构方面，以满足提高燃耗、降低核电成本后对锆合金提出的更高要求。     

Analysis of trace elements in gold alloys by SR-XRF at high energy at the BAMline

Measuring in a non-destructive way the characteristic trace elements of the metal allows following the circulation of gold in the past. The aim of this work is to probe the possibilities of X-ray fluorescence with high energy synchrotron radiation (SR-XRF) at the BAMline at BESSY II to determine the concentration of Pt in ancient gold alloys. A HP-Ge detector was used to measure the Pt K-lines excited with an incident energy of 79.5 keV. Data processing was done by subtraction of a Pt free gold standard spectrum from the spectrum of the sample. Depending on the sample composition, the MDL ranges between 40 and 90 ppm. The first results obtained for a small set of gold alloys of different thickness, size and composition showed that high energy SR-XRF is a significant method for the non-destructive determination of Pt in gold.     

Void swelling of an oxide dispersion strengthened ferritic alloy in a high voltage electron microscope

An oxide dispersion strengthened ferritic alloy with nominal composition Fe-13Cr-3.5Ti-1.5Mo-2TiO₂ and a cast alloy with a composition close to that of the matrix of the oxide dispersion strengthened alloy are irradiated in a high voltage electron microscope in the temperature range 380–550°C. The alloys are doped with 0–30 ppm helium. For alloys containing 10 ppm He a peak swelling temperature at 450°C is found. A maximum swelling of 1.1% is found at an irradiation dose of 20 dpa. In the absence of He no swelling is found in the temperature range 430–470°C. The swelling rate is highest at the onset of swelling. The results obtained here are quite similar to those for some ferritic steels such as FV607, EM 12 and HT9, except for the influence of He and for the dose dependence.     

Dispersion type absorbing materials for thermal reactor control rods

The results of an experimental and theoretical investigation of the physical characteristics of absorbing materials of nimonic type alloys with oxides of the rare-earth elements dispersed in them are presented. The change of absorbing capability of the material as a function of its composition is discussed. The relationship between the mechanical and thermophysieal properties of the absorbing alloys and the concentration of absorber introduced into the alloys and the results of a study of the effect of irradiation on the properties of these materials are given.Translated from Atomnaya Énergiya, Vol. 17, No. 2, pp. 107–113, August, 1964     

High temperature reactivity of two chromium-containing alloys in impure helium

Chromium-rich nickel base alloys 617 and 230 are promising candidate materials for very high temperature gas-cooled reactors (VHTR) but they must resist corrosion in the impure primary cooling helium over very long times. The impurities of the hot helium can promote the development of chromium-rich surface oxides that appear to protect the alloys against intensive corrosion processes. However above a critical temperature (typically in the range 1173-1273 K), chromium oxide is reduced by carbon from the alloy and the surface layer is not stable anymore. Depending on the gas composition, the unprotected material rapidly either gains or loses carbon with a dramatic impact on its mechanical properties. The deleterious reaction of chromia and carbon thus fixes an ultimate reactor operating temperature. Critical temperature measurements are presented for alloys 617 and 230 and the influence of carbon monoxide partial pressure in helium is discussed.     

A theory of radiation-induced segregation in concentrated alloys

A new and simple theory for radiation-induced segregation in concentrated alloys is presented. The coupling between defect fluxes and atom fluxes is accounted for by the concept of preferential migration of vacancies and interstitials via A-atoms or B-atoms in a binary A-B alloy. Similarly, atom fluxes are partitioned into those occurring via vacancies and via interstitials. This approach permits expression of the defect fluxes and atom fluxes in terms of partial diffusivity coeffi- cients and concentration gradients of defects and alloy components. The time and space dependence of the defect concen- trations and composition of a binary alloy is described by a set of three coupled partial differential equations containing four partial diffusivity coefficients, i.e., those of A-atoms and B-atoms diffusing via vacancies and via interstitials. The set of differential equations has been integrated for some model binary alloys with complete miscibility, utilizing the geometry of a thin foil. The sample calculations are in good qualitative agreement with the general features of radiation-induced segregation as deduced from experiments. The temperature, dose and dose-rate dependencies of segregation in concentrated alloys are found to be similar to those predicted by the Johnson-Lam model for dilute alloys.     

Influence of long-term sodium exposure on the composition and microstructure of austenitic alloys

Austenitic alloys (Types 304, 316, 321, 347 stainless steel and Incoloy-800) were exposed to flowing sodium in out-of-pile test loops at 704 °C (1300 °F) and 621 °C (1150 °F) for varying times up to 15726 h. Changes in chemical composition and microstructure increased with increasing exposure time. Major alloying elements (Cr, Ni, Mn) were depleted from surface layers up to 130 μm thick. Unstabilized alloys (Types 304 and 316) lost carbon during exposure while stabilized alloys (Types 321, 347 and I-800) tended to gain carbon. Variations in other minor elements with exposure were determined. Changes in microstructure reflected the compositional changes in all the alloys. Specimens were examined by optical, transmission electron and scanning electron microscopy. A ferrite layer formed at the sodium exposed surface of all alloys except Incoloy-800. Sigma phase precipitation increased with exposure time. In the stabilized alloys cavities formed up to 120 μm below the sodium-exposed surface. The subsurface cavities appeared to be connected to surface pits via intergranular channels and were related to a decrease in density observed in the specimens.     

Investigations of multiple backscattering and albedos of 1.12 MeV gamma photons in elements and alloys

The energy and intensity distributions of multiple backscattering of 1.12 MeV gamma photons emerging from targets of elements and alloys are observed as a function of thickness and atomic number (Z) of the target. The numbers of these multiply backscattered events show an increase with increase in target thickness, and then saturate for a particular thickness of the target called saturation thickness (depth). The saturation thickness decreases with increasing atomic number and varies as e^−Z. The multiple backscattering, an interfering background noise in Compton profile, has been successfully used to assign the ‘‘effective atomic number’’ to alloys. Monte Carlo calculations also support the present experimental results. The number, energy and dose albedos are also found to be saturating for the same thickness where the numbers of multiply backscattered events saturate.     

Mechanical properties of high-nickel alloys EP-753 and РЕ-16 after neutron irradiation to 54 dpa at 400-650 °С

Short-term mechanical properties and void swelling were investigated for high-nickel alloys РЕ-16 and three compositional variants of Russian alloy EP-753 and in various starting conditions after side-by-side irradiation in the BN-350 fast reactor at 400, 500, 600 and 650 °С to 54 dpa. For both alloys irradiation resulted in significant hardening and ductility reduction dependent on their chemical composition and initial heat treatment. At test temperatures equal to the irradiation values both alloys exhibited a high level of strength and satisfactory ductility. In the test temperature range of 550-650 °С the phenomenon of high-temperature irradiation embrittlement was observed.     

Compositional changes in Fe-Cr-Ni alloys under proton bombardment at elevated temperatures

Compositional redistribution in austenitic Fe-Cr-Ni alloys during energetic proton bombardment has been calculated as a function of time, temperature, and ion energy, using a kinetic model of radiation-induced segregation recently developed for ternary alloys. The effect of spatial nonuniformity in damage rates was taken into account and found to have a peculiar effect on the redistribution of the alloying elements. Enrichment of Ni occurs at the bombarded surface and in the bulk beyond the damage range, whereas Fe and Cr are enriched in the peak-damage region at the expense of their depletion in regions near the surface and beyond the damage range. These compositional changes can lead to local phase transformation, since the composition of local regions of the alloy is shifted away from the initial composition into different parts of the multicomponent phase diagram. The stability of the austenite phase in the sub-surface and post-range regions is enhanced by irradiation, while the austenite-to-ferrite transformation takes place in the peak-damage region.     

Oxidation behaviour of fecralloy and 20/25/Nb stainless steels and a nickel-based alloy,PE16, in argon containing 7 μatm water vapour and 375 μatm hydrogen

The oxidation behaviour of four alloys [yttrium-bearing and yttrium-free Fecralloy ferritic stainless steels, a 20/25/Nb austenitic stainless steel and a nimonic alloy, PE16] have been studied in argon (1.3 atm pressure) containing 7 μatm water vapour and 375 μatm hydrogen. The alloys were exposed for periods up to 7166 h at temperatures in the range, 650–1000 °C. The overall reaction kinetics were determined, as were the magnitudes and nature of both the general and any internal attack. The behaviour of the alloys in wet argon was consistent with that observed in fully oxidising environments, except at the highest temperature studied, 800 and 1000°C, with the 20/25/Nb and Fecralloy steels respectively. In carbon dioxide a greater attack of both alloys and a more complex composition of the oxide film on the 20/25/Nb steel have been attributed to its higher oxygen potential compared with that of the H₂O/H₂ gas mixture.     

Contribution a l'etude du diagramme plutonium-cuivre

The compounds PuCu₂ and PuCu₄ are brought to evidence by solid state diffusion. The growth kinetics and the formation mechanism of these phases are studied using couples constituted of a biphased Pu-Cu alloy and of pure copper. A ternary phase of approximative composition PuCu₃ with a variable amount of Ga is brought to evidence using couples constituted of pure copper and of PuGa alloys. Crystalline parameters are determined by the Debye-Sherrer method on alloys obtained by direct elaboration or by diffusion.     

Ab initio calculations and interatomic potentials for iron and iron alloys: Achievements within the Perfect Project

The objective of the FP6 Perfect Project was to develop a first example of integrated multiscale computational models, capable of describing the effects of irradiation in nuclear reactor components, namely vessel and internals. The use of ab initio techniques to study, in the most reliable way currently possible, atomic-level interactions between species and defects, and the transfer of this knowledge to interatomic potentials, of use for large scale dynamic simulations, lie at the core of this effort. The target materials of the Project were bainitic steels (vessel) and austenitic steels (internals), i.e. iron alloys. In this article, the advances made within the Project in the understanding of defect properties in Fe alloys, by means of ab initio calculations, and in the development of interatomic potentials for Fe and Fe alloys are overviewed, thereby providing a reference basis for further progress in the field. Emphasis is put in showing how the produced data have enhanced our level of understanding of microstructural processes occurring under irradiation in model alloys and steels used in existing nuclear power plants.     

Dynamic analysis and evolution of mixed materials bombarded with multiple ions beams

Materials modification and response to the impact of energetic particles is an important ongoing research area in several applications. This includes both experimental and theoretical work. We updated and improved our models for the simulation of Ion Transport in Materials and Compounds (ITMC-DYN), part of HEIGHTS package, to now include dynamic changing of materials composition as result of multiple ion beams bombardment and target atoms mixing, segregation, and diffusion. Implemented models consider detail processes of simultaneous and multiple ions penetration and mixing, scattering, reflection, physical and chemical sputtering of composite material atoms, dynamic surface evolution/modification, thermal diffusion, and surface segregation and recombination of species in multicomponent alloys. For benchmarking of the models we compared our simulations results with several recent experimental data for nanoapplications and for the developments of future fusion energy systems. Simulation of tungsten surface evolution and modification under the impact of hydrogen ions with carbon impurities demonstrated good agreement with recent experiments. Details of surface erosion and conditions for blisters formation as a function of fluence and material temperature were also analyzed and explained.