| 1. |
- Anghel, Clara, et al.
(författare)
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Effects of Pt surface coverage on oxidation of Zr and other materials
- 2008
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Ingår i: Journal of ASTM International. - 1546-962X. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Certain elements, including noble metals, are identified to influence corrosion behavior of many metals in high-temperature water/steam and O 2. We have previously reported effects of porous Pt coatings on the thermal oxidation of Zr, Fe, Ni, Cr and GaAs in O2. Effects of Pt on oxidation of Zircaloy-2 In H2O have also been observed at temperatures near 400°C. An enhanced oxidation rate Is observed in all of the studied systems upon a sufficiently high surface Pt-particle density. Even more interesting, low Pt-particle density in most cases leads to a decreased oxidation rate. In the case of Zr and Zircaloy-2 the beneficial effect of Pt is stronger when hydrogen is present In the metal substrate and in the oxide layer. From 18O/SIMS experiments it is concluded that, for a sufficiently high Pt-particle density on the surface, enhanced transport of dissociated oxygen, On- (n=0; 2), towards the oxide/metal interface occurs in all of the studied systems. An oxygen spillover from Pt particles to the adjacent surface is a known phenomenon in catalysis and partly explains the results observed also in the current study of oxidation of Zr-based materials. Such a spillover involves a high surface diffusivity of dissociated oxygen, O n-, which results In an increased gradient of On- across the oxide scale. In turn, the high oxygen gradient enhances the transport of oxygen towards the substrate/oxide-interface. This shows that not only diffusivlty but also an effective activity of dissociated oxygen at the external oxide surface influences the oxidation rate. Naturally, the effects of Pt are maximized when small (nm-sized) and evenly distributed Pt particles are present on the surface. In our presentation a summary of obtained results of Pt additions on different materials will be given with suggested interpretations. Especially, the observed beneficial combination of Pt and hydrogen in the oxidation of Zr-based materials Is discussed with a possible mechanistic explanation. Parallels are also drawn to the potential effect of Noble Metal Chemical Application (NMCA), used in a large fraction of the U.S. BWRs, on the corrosion resistance of Zr-based claddings.
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| 2. |
- Drakos, C, et al.
(författare)
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Identification of a Physical Model to Evaluate Rutting Performance of Asphalt Mixtures
- 2005
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Ingår i: Journal of ASTM International. - 1546-962X. ; 2:3, s. 165-185
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is to identify a physical model that can provide reliable predictions about a mixture's ability to resist permanent deformation under realistic stress states. Key differences were identified between stress states under the existing Asphalt Pavement Analyzer (APA) loading device (hose) and stress states under radial truck tires, which may indicate potentially different rutting mechanisms. It was shown that the APA hose was not capturing the critical lateral stresses found to be detrimental to rutting and cracking of HMA pavements. A new loading device (rib) was designed and constructed for use in the APA that more closely represents stress states found under radial tires. Contact-stress measurements under the two loading devices - hose and rib - showed that the rib was able to reproduce the lateral stresses found under individual ribs on a radial-tire tread. Subsequent finite element modeling also showed that the rib appeared to generate similar shear stress patterns to those found under the modeled radial-tire load. A new method was developed to measure deformations on the surface of APA specimens, where a contour gauge was used to record and store the entire surface profile of the sample throughout the progress of the test. An area-change parameter, which reflects volume change, was introduced to calculate the volumetric changes in the specimen. The area-change parameter can be used to determine whether specimen rutting is primarily due to shear instability or consolidation. Two mixtures of known field performance - poor and good - were tested to evaluate the test's ability to predict performance with the new loading device and the new measurement and interpretation system. Results showed that the new system (loading strip and profile measurement method) appears to have greater potential of evaluating a mixture's potential for instability rutting than the original (hose and single rut-depth measurement) configuration.
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| 3. |
- Efsing, Pål, 1965-, et al.
(författare)
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Analysis of the Ductile-to-Brittle Transition Temperature Shift in a Commercial Power Plant With High Nickel Containing Weld Material
- 2007
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X. ; 4:7
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Tidskriftsartikel (refereegranskat)abstract
- Plant specific surveillance programs that ideally include all relevant materials and materials combinations that are subjected to neutron irradiation during operation address the degradation due to irradiation of the reactor pressure vessel material for nuclear electric power plants. Plant specific surveillance programs are not unique to the two power plants treated in this study. The current Swedish regulatory system does, however, call for a fairly rigid approach within the surveillance program. In the Swedish case, this means that there is a plant specific predetermined inspection∕test program that has to be followed in order to verify the operability of the power plant and also to verify the operational limits with respect to pressure∕temperature effects on a repetitive basis. The two pressurized water reactor plants Ringhals 3 and 4 have in common that the weld metal used for the butt welds of the reactor pressure vessel is a high nickel type material, above the current limits of the NUREG Reg. Guide 1.99, rev. 2. In the original state, the high nickel content provides excellent fracture toughness in the unirradiated material condition and a low ductile-to-brittle transformation temperature (DBTT). It has, however, been highlighted in several studies that high nickel materials exhibit a very large DBTT shift as a consequence of irradiation, and also that the precipitates that form during the irradiation are not as easily controlled during a heat treatment to remove the irradiation damage as are the copper rich clusters. This paper will present the current state of the art regarding these effects as observed in the weld metal specimens. The paper will present the results from the Charpy V notched and fracture mechanics specimen test encapsulated in the Ringhals Units 3 and 4 surveillance programs. The results from the Ringhals Units 3 and 4 surveillance programs show that there is a need for corrective action to be taken in order to ensure 60 y of operability for the two power plants.
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| 4. |
- Efsing, Pål, 1965-, et al.
(författare)
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Ringhals Units 3 and 4 - Fluence determination in a historic and future perspective
- 2012
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X. ; 9:4, s. 104012-9
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Tidskriftsartikel (refereegranskat)abstract
- The Ringhals site is situated on the Swedish southwest coastline. At the site, there are four operating nuclear power plants. Historically, the Swedish policy has been that the nuclear power plants were to be closed in 2010. The present position is to operate the units until their technical and economic lifetime has run out. The units shall be maintained and invested in to ensure a lifetime of at least 50 years, but the actions taken shall not limit the time to this date. When the initial surveillance capsules were evaluated, it was noted that the material properties of the weld material of unit 3 and 4 showed some deviations from the expected behaviour. Currently there is an extensive project running for re-evaluating the embrittlement situation from a long-term operating perspective. One part of the project is aimed at more accurately determining the fluence levels of the reactor pressure vessels (RPVs). The basis for the early evaluations of the dosimeters in the surveillance capsules and the corresponding fluence evaluation had an operating lifetime of 25 years as a target value. Therefore, the accuracy and refinement of the measurement and calculation were taken to be good enough to suit this life span. Looking back at the results from the dosimetry measurements there are a few discrepancies. Some of the dosimeters were disintegrated and some measurements had comparatively large uncertainties. When starting this project there were some re-evaluations done with the old fluence prediction model. For every new run and refinement there appeared new difficulties, and the decision was to start the evaluation from scratch.Then there are two questions remaining regarding the fluence: What is the current fluence level? What will the resulting fluence be after 60 years of operation, when we have up-rated output power of both reactors? This paper aims to describe the view of the fluence evaluation in the surveillance program of the RPV, both in a historical and prospective view.
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| 5. |
- Hailesilassie, Biruk Wobeshet, et al.
(författare)
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Mechanisms of asphalt blistering on concrete bridges
- 2012
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Ingår i: Journal of ASTM International. - 1546-962X. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Blistering is a major problem in asphalt-covered concrete structures, such as multi-storage parking buildings, built-up roofs, tunnels, pedestrian areas, or concrete bridge decks. In this particular research, a linear viscoelastic finite-element model is developed to simulate time-dependent blister growth in an asphalt layer under uniformly applied pressure with and without temperature and pressure fluctuation. Indirect tensile tests on mastic asphalt (MA) are performed at three different temperatures to characterize and determine the material properties for the model. A three-dimensional thick-plate axisymmetric finiteelement model is developed using ABAQUS with linear viscoelastic properties and validated with closedform solution from first-order shear-deformation theory for thick plates. Elastic-viscoelastic analogy is used to find an analytic solution for the time-dependent deflection of the blister. In addition, the blister test is conducted on different samples of MA in the laboratory and digital image correlation measurement technique is used to capture the three-dimensional vertical deflection of the MA with time. Finally, the results from image correlation are compared with the finite-element simulation and thick-plate theory analytic solution. The finite-element model simulation shows that the daily temperature variations may have a significant influence on blister growth in asphalt pavements. It is found that the blister can grow continuously under repeated loading conditions over subsequent days. The study concludes that temperature fluctuation in the blister has more influence on blister growth than fluctuation of the pressure inside the blister.
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| 6. |
- Kristoffersen, Hans, et al.
(författare)
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A complete system for testing and evaluation of quenchants and quenching systems
- 2009
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Ingår i: Journal of ASTM International. - 1546-962X. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- The quenching operation is a very critical part of the heat treatment process. Improper quenching parameters and drifting of the cooling characteristics during the working life of the quenchant will influence the quenching results. Sophisticated computer-based tools have made It possible to monitor, evaluate, and perform a continuous quality control of the quenchants' and the quenching systems' performance. The increasing and ever more sophisticated use of FEM simulation In order to optimize products and processes means that there Is also a growing need for accurate input data. In quenching simulations, the boundary conditions expressed as heat transfer coefficients based on measured cooling curves are of great importance In order to obtain accurate calculations. One system that offers these features is the ivf SmartQuench®system (SQ).4 This system encompasses data acquisition and a software module for analyzing the cooling curves. With the new, extended software module that was introduced in 2007, SQintegra (SQi), 4 It is now possible for the user to calculate heat transfer coefficients (e.g., for the ISO 9950 probe), as well as hardness and microstructure in a cross section of steel samples. Heat transfer calculations are made on the basis of an inverse analysis of the recorded cooling curve. The result is used as input for the calculation of microstructural constituents and the hardness profile of cylindrical samples of arbitrary diameter. Calculations can be made for several different steel grades. The system can be used for quality control of quenchants, troubleshooting, process follow-up, calculation of heat transfer coefficients, hardness calculations compared to verifying tests, and sensitivity analyses of quenchants. The system has also been used to evaluate the cooling performance In showers used for quenching after induction heating. The process window for a specific quenching shower was established for a polymer quenchant. Factors considered were flow rate, concentration and temperature of the quenchant. Copyright © 2009 by ASTM International.
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| 7. |
- Malerba, L., et al.
(författare)
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Modelling of radiation damage in Fe-Cr alloys
- 2007
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Ingår i: Journal of ASTM International. - 1546-962X. ; 4:6
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Tidskriftsartikel (refereegranskat)abstract
- High-Cr ferritic/martensitic steels are being considered as structural materials for a large number of future nuclear applications, from fusion to accelerator-driven systems and GenIV reactors. Fe-Cr alloys can be used as model materials to investigate some of the mechanisms governing their microstructure evolution under irradiation and its correlation to changes in their macroscopic properties. Focusing on these alloys, we show an example of how the integration of computer simulation and theoretical models can provide keys for the interpretation of a host of relevant experimental observations. In particular we show that proper accounting for two basic features of these alloys, namely, the existence of a fairly strong attractive interaction between self-interstitials and Cr atoms and of a mixing enthalpy that changes sign from negative to positive around 8 to 10% Cr, is a necessary and, to a certain extent, sufficient condition to rationalize and understand their behavior under irradiation. These features have been revealed by ab initio calculations, are supported by experimental evidence, and have been adequately transferred into advanced empirical interatomic potentials, which have been and are being used for the simulation of damage production, defect behavior, and phase transformation in these alloys. The results of the simulations have been and are being used to parameterize models capable of extending the description of radiation effects to scales beyond the reach of molecular dynamics. The present paper intends to highlight the most important achievements and results of this research activity.
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| 8. |
- Massih, Ali R, et al.
(författare)
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The effect of beta quenching in final dimension on the irradiation growth of tubes and channels
- 2005
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Ingår i: Journal of ASTM International. - 1546-962X. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- The effect of β-quenching performed in the final size of Zircaloy-4 guide tubes and Zircaloy-2 sheets during fabrication process on the products' mechanical properties, crystallographic texture, microstructure, and corrosion behavior has been investigated and presented in this paper. Moreover, the impact of this processing on the irradiation growth of pressurized water reactor Zircaloy-4 guide tubes in a test reactor and Zircaloy-2 fuel channels in boiling water reactors has been evaluated. The results indicate that the irradiation growth rates of the final dimension β-quenched (FDBQ) products are substantially lower than those fabricated by conventional (Standard) techniques. BWR channels irradiated up to a fast neutron fluence of about 9 × 1025 m−2 maintain this low growth behavior. Corrosion properties of FDBQ products have been made similar to that of the Standard material by performing an α-annealing step after the β-quenching. The annealing temperature and annealing time have been optimized in order to obtain good corrosion resistance. In-reactor data on Zircaloy-2 channels irradiated to a fuel assembly exposure of about 50 MWd/kgU indicate similar corrosion performance for the FDBQ and Standard materials. Finally, the in-reactor data on Zircaloy-2 channels show that bowing of the FDBQ and Standard channels is comparable up to a fast neutron fluence of about 7 × 1025 m−2.
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| 9. |
- May, Johannes, et al.
(författare)
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Extended mechanical testing of RPV surveillance materials using reconstitution technique for small sized specimen to assist Long Term Operation Extended mechanical testing of RPV surveillance materials using reconstitution technique for small sized specimen to assist Long Term Operation
- 2014
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X .- 1546-962X. ; STP:1576
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Tidskriftsartikel (refereegranskat)abstract
- For the Ringhals 3 and 4 PWR RPV, results from the irradiation surveillance program are available also for neutron fluences which cover long-term operation (LTO). These standard surveillance results are based on the RTNDT concept. The belt-line welds of both RPVs have an elevated nickel-content of 1.6 wt.-% and, as a consequence, irradiation response is higher than predicted by model equations. Therefore, the mechanical testing program has been expanded, exceeding the requirements of the standard testing program and covering both base and weld materials. To improve the understanding of the material behavior, extended Master Curve testing was performed on PCCV and subsize SE(B) specimens from irradiation surveillance capsules with the help of specimen reconstitution technique. Special care has been taken on the limited amount of weld material within the available broken Charpy halves before specimen reconstitution.Results have been compared to existing data on similar base and weld materials from the German research programs CARISMA and CARINA. Late-blooming effects or sudden saturation effects are not observed for base or weld materials under LTO conditions. The data for the four different weld materials of similar chemical composition indicate that not only the chemical composition, but also other influencing factors like e.g. the welding heat treatment may be important for the reference temperature of the unirradiated state as well as for the irradiation behavior. To investigate this effect more in detail, a future investigation program will be discussed including manufacturing of a surrogate weld material with the same chemical composition as in Ringhals 3 and 4 RPV. The influence of heat treatment condition can be investigated by applying different heat treatments and subsequently performing test reactor irradiation and mechanical testing. Specimen reconstitution will be required due to limited space inside the test reactor irradiation capsules.
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| 10. |
- Nygren, Olle, et al.
(författare)
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Development of a method for screening spill and leakage of antibiotics on surfaces based on wipe sampling and HPLC-MS/MS analysis
- 2011
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Ingår i: Journal of ASTM International. - : ASTM International. - 1546-962X. ; 8:6
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Tidskriftsartikel (refereegranskat)abstract
- A screening method for determination of spill and leakage of 12 different antibiotic substances has been developed. The method is based on wipe sampling where the sampling procedure has been simplified for screening purposes. After sample processing, the antibiotic substances are determined by liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). Twelve antibiotic substances can be determined in the screening method: Cefadroxil, Cefalexin, Ciprofloxacin, Demeclocyklin HCl, Diaveridin, Doxycyklin, Enrofloxacin, Flukonazol, Metronidazol, Norfloxacin, Ofloxacin, and Trimetoprim. These substances are active components in antibiotic drugs frequently used in Sweden. For screening investigations using collection of wipe samples, good or acceptable performance was obtained for ten substances on three or more surface materials. Although not fully acceptable, useful performance for screening purposes was also obtained on the other surface materials and for the other substances, except Demeclocyklin HCl, on all surface materials. By employing a classification procedure, where the samples are divided into groups according to increasing contamination of the sample surfaces, screening samples and the contamination level can simply be compared. This classification procedure will also help to circumvent any deficiency in recovery performance for some substances and surface materials.
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