Laboratory Heating Research Articles

Glomalin‐related Soil Protein Response to Heating Temperature: A Laboratory Approach

AbstractForest fires are a recurrent natural phenomenon in the Mediterranean basin. Fires can affect physical, chemical and biological soil properties. The effects on soil properties are closely controlled by fire severity, which is a consequence of temperatures reached and the length of residence of heat in the soil. In this study, the response of glomalin‐related soil protein (GRSP) − a glycoprotein produced by arbuscular mycorrhizal fungi − to heating temperature has been studied. Laboratory heating treatments were carried out at 180°C, 200°C, 250°C, 300°C, 400°C and 500°C in soil samples from eight different sites in SE Spain. The sites selected had mainly different soil characteristics. The results of heating on soil water repellency and soil organic carbon (SOC) were also included in the study. GRSP response to temperature was different between sites. Redundancy analyses divided sandy soils from the rest of soil types. Total content of aggregates, SOC and clay and sand content were the most significant properties explaining the response of GRSP to heating treatments. Results showed that GRSP was affected even at low temperature. SOC response to temperature was very similar between sites. Soil water repellency did not appear after heating in wettable soils and disappeared in water‐repellent ones at temperatures over 200°C. Our results indicate that GRSP could provide relevant information about fire severity. Copyright © 2015 John Wiley & Sons, Ltd.

Influence of wildfire severity on soil physical degradation in two pine forest stands of NW Spain

This study examined the effect of wildfire on the physical degradation of two forest soils in NW Spain and compared this against changes produced by controlled laboratory heating experiments in which unburned soils from neighbouring sites were exposed to five different heating regimes. The physical soil degradation was considered with respect to organic carbon content, dry aggregate size distribution, water aggregate stability, water repellency, and hydraulic conductivity. The results of this analysis show that the changes in the physical properties of the wildfire-affected soils were similar to the changes observed in the heating experiments. However, the wildfire had contrasting effects in terms of soil physical degradation at the two study sites, which can be attributed to differences in soil heating regimes and fire severity. At one study site, the wildfire did not produce marked changes in organic carbon content or in aggregation, except for a slight fragmentation of macro-aggregates into micro-aggregates. Also, soil water repellency remained very strong after the wildfire, resulting in low hydraulic conductivity. Based on the laboratory experiments, the soil at this site was not exposed to temperatures above 220°C. The wildfire at the other study site resulted in more pronounced degradation of the soil, as shown in the reduction of organic carbon content by almost 50%, resulting in reduced stability of the aggregates. The wildfire also reduced soil water repellency considerably, but hydraulic conductivity did not increase noticeably. In this case the soil could be exposed to temperatures between 220 and 380°C.

Reply to the comment of Lovera et al. (2015) on “Systematic variations of argon diffusion in feldspars and implications for thermochronometry” by Cassata and Renne

In this reply we address remarks from Lovera et al. (2015) regarding experiments that we conducted on K-feldspar from Madagascar and their previously published diffusion experiments. Observations of curvature on Arrhenius plots obtained from multiple-domain K-feldspars, as discussed by Lovera et al. (2015), are consistent with the general conclusion of our paper that both sub-grain domains and structural modifications associated with laboratory heating cause deviations from linearity on Arrhenius plots. We review observations of non-linearity that are inconsistent with multiple-domain theory (e.g., upward curvature on plagioclase Arrhenius plots) to support our contention that structural transitions are an important consideration.

Flow Maldistribution in Industrial Air Heaters and Its Effect on Heat Transfer

Flow maldistribution in cross-flow heat exchangers used for industrial air heaters or recuperators is fairly common and can lead to a number of undesirable effects, one of which is deterioration in the thermal performance. The effect of gross flow maldistribution and the improvement in the thermal performance of flow correction guide vanes is investigated using a laboratory heat exchanger apparatus. The thermal performance deterioration from maldistribution was up to around 30 %. Modest improvements in the overall heat transfer coefficient and heat exchanger effectiveness when vanes were used was found for the range of air-side Reynolds numbers tested. Vanes were found to reduce the deterioration in thermal performance by up to 60 % compared to a perfectly uniform flow situation. Based on the e-NTU correlations the thermal performance deterioration is predicted to decrease as the number of tube rows (i.e. NTU) increases. The effective heat transfer area and therefore thermal performance of industrial air heaters and recuperators can be improved by using flow correction devices, such as guide vanes.

Comparative mineralogical study of thermally-altered coal-dump waste, natural rocks and the products of laboratory heating experiments

Research on rocks formed due to pyrometamorphism of waste in burning coal-mine dumps (BCMD) mainly in the Upper Silesian Coal Basin has enabled identification of a large number of different mineral species. These species are usually well-known minerals, e.g., olivines, plagioclases and clinopyroxenes. However, their crystal chemistry is often unique. Mineralogical- and chemical similarities between the BCMD and non-anthropogenic geological environments are outlined here. To better understand the crystallization processes of the minerals occurring in the BCMD, three types of heating experiments were performed. For these, ten protolith (thermally-unchanged) dump samples, mostly shales and carbonate rocks, were heated alone and mixed together and with a CaF2 flux. Quantitative chemical analyses of the synthesized mixtures have shown that they are mineralogically similar to the rocks found in the BCMD. They are also similar in terms of their crystal chemistry, e.g., synthesized clinopyroxenes are rich in diopside and esseneite components and may capture phosphorus, plagioclase is rich in anorthite and contains iron and magnesium, and wüstite exists as a solid solution with periclase and is doped with calcium and other elements. Highly variable amounts of indialite–ferroindialite were formed in some samples due to solid-phase transformations or melt crystallization, depending on the experimental conditions and the protolith used.

Numerical analysis of thermal impact on hydro-mechanical properties of clay

As is known, high-level radioactive waste (HLW) is commonly heat-emitting. Heat output from HLW will dissipate through the surrounding rocks and induce complex thermo-hydro-mechanical-chemical (THMC) processes. In highly consolidated clayey rocks, thermal effects are particularly significant because of their very low permeability and water-saturated state. Thermal impact on the integrity of the geological barriers is of most importance with regard to the long-term safety of repositories. This study focuses on numerical analysis of thermal effects on hydro-mechanical properties of clayey rock using a coupled thermo-mechanical multiphase flow (TH2M) model which is implemented in the finite element programme OpenGeoSys (OGS). The material properties of the numerical model are characterised by a transversal isotropic elastic model based on Hooke's law, a non-isothermal multiphase flow model based on van Genuchten function and Darcy's law, and a transversal isotropic heat transport model based on Fourier's law. In the numerical approaches, special attention has been paid to the thermal expansion of three different phases: gas, fluid and solid, which could induce changes in pore pressure and porosity. Furthermore, the strong swelling and shrinkage behaviours of clayey material are also considered in the present model. The model has been applied to simulate a laboratory heating experiment on claystone. The numerical model gives a satisfactory representation of the observed material behaviour in the laboratory experiment. The comparison of the calculated results with the laboratory findings verifies that the simulation with the present numerical model could provide a deeper understanding of the observed effects.

Insights into magmatic processes and hydrothermal alteration of in situ superfast spreading ocean crust at ODP/IODP site 1256 from a cluster analysis of rock magnetic properties

AbstractWe analyze magnetic properties from Ocean Drilling Program (ODP)/Integrated ODP (IODP) Hole 1256D (6°44.1' N, 91°56.1' W) on the Cocos Plate in ∼15.2 Ma oceanic crust generated by superfast seafloor spreading, the only drill hole that has sampled all three oceanic crust layers in a tectonically undisturbed setting. Fuzzy c‐means cluster analysis and nonlinear mapping are utilized to study down‐hole trends in the ratio of the saturation remanent magnetization and the saturation magnetization, the coercive force, the ratio of the remanent coercive force and coercive force, the low‐field magnetic susceptibility, and the Curie temperature, to evaluate the effects of magmatic and hydrothermal processes on magnetic properties. A statistically robust five cluster solution separates the data predominantly into three clusters that express increasing hydrothermal alteration of the lavas, which differ from two distinct clusters mainly representing the dikes and gabbros. Extensive alteration can obliterate magnetic property differences between lavas, dikes, and gabbros. The imprint of thermochemical alteration on the iron‐titanium oxides is only partially related to the porosity of the rocks. Thus, the analysis complements interpretation based on electrofacies analysis. All clusters display rock magnetic characteristics compatible with an ability to retain a stable natural remanent magnetization suggesting that the entire sampled sequence of ocean crust can contribute to marine magnetic anomalies. Paleointensity determination is difficult because of the propensity of oxyexsolution during laboratory heating and/or the presence of intergrowths. The upper part of the extrusive sequence, the granoblastic dikes, and moderately altered gabbros may contain a comparatively uncontaminated thermoremanent magnetization.

Effect of applied EHD on in-tube condensation of R-134a within an assembled experimental rig including a laboratory heat exchanger

Effects of applied EHD1Electrohydrodynamic.1 on in-tube condensation of R-134a refrigerant in a double pipe heat exchanger are experimentally investigated to present applicability of the EHD technique in vertical position. The refrigerant’s vapor was flowed inside of the inner tube and cooling water was counter currently flowed in annulus section. Tests were performed at different mass flow rates 35–65kg/m2s of refrigerant and different electrical field strengths (0–8kV), under their identified breakdown strengths for two various electrode diameter sizes (4 and 6mm), while the average saturation temperature was 43 and 33°C respectively. Experimental results demonstrate a remarkable potential in utilizing EHD to enhance condensation heat transfer. It is concluded that the enhancement is driven by the effective removal of the condensate through EHD induced liquid extraction and dispersion phenomena. For the presence of the electrodes, the experimental results indicate that the maximum heat transfer ER2Enhancement ratio.2 is around 14% and 31% respectively for electrodes with diameter of 4mm (10.7mm electrode gap) and 6mm (9.7mm electrode gap), while power expenditure was negligible.

Two-Dimensional Ablation and Thermal Response Analyses for Mars Science Laboratory Heat Shield

This paper examines transient simulations performed to predict in-depth thermal response and surface recession of the proposed heat shield material for the Mars Science Laboratory entry capsule, that is, phenolic impregnated carbon ablator. The finite volume material response code used in this paper solves the time-dependent governing equations, including energy conservation and a three-component decomposition model, with a surface energy-balance condition and a moving grid system to predict shape change due to surface recession. The predicted in-depth thermal response of heat shield material generally agrees well with the thermocouple data under various arcjet conditions. Also, two-dimensional computations using aerothermal environment for Mars entry (derived from a proposed three-sigma trajectory) are performed around the heat shield shoulder region, where high heating occurs as the result of angle of attack. Parametric studies are conducted to examine the effects of carbon-fiber orientation, material properties, and surface recession on heat shield bondline temperature history. It is proved that the fiber orientation configuration of the baseline heat shield has the lowest maximum bondline temperature.

On estimating the efficiency of a neural optimizer for the parameters of a PID controller for heating objects control

In this work, we consider the problems of estimating the energy efficiency of applying a neural optimizer to tune a PID controller in controlling a laboratory heating furnace for cast bars. We estimate the electric power savings achieved when running the technological process with the optimizer as compared to a regular PID controller.

Laboratory study of non-aqueous phase liquid and water co-boiling during thermal treatment

In situ thermal treatment technologies, such as electrical resistance heating and thermal conductive heating, use subsurface temperature measurements in addition to the analysis of soil and groundwater samples to monitor remediation performance. One potential indication of non-aqueous phase liquid (NAPL) removal is an increase in temperature following observations of a co-boiling plateau, during which subsurface temperatures remain constant as NAPL and water co-boil. However, observed co-boiling temperatures can be affected by the composition of the NAPL and the proximity of the NAPL to the temperature measurement location. Results of laboratory heating experiments using single-component and multi-component NAPLs showed that local-scale temperature measurements can be mistakenly interpreted as an indication of the end of NAPL–water co-boiling, and that significant NAPL saturations (1% to 9%) remain despite observed increases in temperature. Furthermore, co-boiling of multi-component NAPL results in gradually increasing temperature, rather than a co-boiling plateau. Measurements of gas production can serve as a complementary metric for assessing NAPL removal by providing a larger-scale measurement integrated over multiple smaller-scale NAPL locations. Measurements of the composition of the NAPL condensate can provide ISTT operators with information regarding the progress of NAPL removal for multi-component sources.

Mars Science Laboratory Heat Shield Aerothermodynamics: Design and Reconstruction

The Mars Science Laboratory heat shield was designed to withstand a fully turbulent heat pulse using information from ground testing and computational analysis on a preflight design trajectory. Instrumentation on the flight heat shield measured in-depth temperatures to permit reconstruction of the surface heating. The data indicate that boundary-layer transition occurred at five of seven measurement locations before peak heating. Data oscillations at three pressure measurement locations may also indicate transition. This paper presents the heat shield temperature and pressure data, possible explanations for the timing of boundary-layer transition, and a comparison of reconstructed and computational heating on the actual trajectory. A smooth-wall boundary-layer Reynolds number that was used to predict transition is compared with observed transition at various heat shield locations. A single transition Reynolds number criterion does not uniformly explain the timing of boundary-layer transition observed during flight. A roughness-based Reynolds number suggests that transition due to discrete or distributed roughness elements occurred. However, the distributed roughness height from acreage heat shield material would have needed to be larger than expected. The instrumentation confirmed the predicted location of maximum turbulent heat flux near the lee-side shoulder. The reconstructed heat flux at that location is bounded by smooth-wall turbulent convective heating, indicating that a significant augmentation due to surface roughness did not occur. Turbulent heating on the downstream side of the heat shield nose exceeded smooth-wall convective levels, assuming a supercatalytic surface, indicating that roughness may have augmented heating. The stagnation region heating also exceeded calculated convective heating; the cause of elevated heating may be attributed to a combination of shock-layer radiation and a heating augmentation of unknown origin that was also evident in ground test data.

Temperature limits for preservation of primary calcite clumped isotope paleotemperatures

Solid-state reordering of C–O bonds in the calcite lattice can alter the clumped isotope composition of paleotemperature archives such as fossil brachiopod shells without inducing significant changes in shell microstructure and trace element concentrations, metrics commonly used to gauge preservation quality. To correctly interpret the paleoenvironmental significance of clumped isotope-derived paleotemperatures, it is necessary to understand the temperature–time domain in which solid-state C–O bond reordering is important. We address this question using a combination of laboratory and natural geological experiments on Paleozoic brachiopod shells. The laboratory experiments involve heating fossil brachiopod calcite at different temperatures and times to directly observe rates of 13C–18O bond reordering. The resulting Arrhenius parameters are indistinguishable from values previously determined for an optical calcite with similar trace element compositions. We develop an alternative kinetic model for reordering that accounts for non-first-order reaction progress observed during the initial several hundred minutes of laboratory heating experiments, and show that the simplified first-order approximation model (Passey and Henkes, 2012) predicts reaction progress equally well for temperatures and timescales relevant to sedimentary basins. We evaluate our laboratory-based rate predictions by studying brachiopod calcite from several sedimentary basins with independently constrained burial temperature histories. Specifically, we use the laboratory-derived Arrhenius parameters to predict the evolution of brachiopod calcite clumped isotope compositions during successive one million-year time steps reflecting the burial and exhumation temperature paths of each basin. While this exercise is limited by the relatively large uncertainties in the temperature histories of these basins, we find general correspondence, within error, between predicted and observed clumped isotope values. We present simplified temperature–time diagrams for calcite showing domains where primary clumped isotope compositions will be preserved, partially reordered, and fully reordered. In conclusion, calcite samples dwelling at ∼100°C or lower for 106–108 year timescales should not be affected by solid-state C–O bond reordering.

Impact of Vanadium Addition on API X100 Steel

Laboratory heats of an API X100 steel (Mn–Mo–Nb) with two levels of vanadium (0.004% and 0.063%) were melted and control rolled simulating a coiled plate production process. Extensive microstructural analyses were performed, including optical, EBSD and TEM. Texture analyses of the two alloys were also compared. Mechanical properties were determined for various rolling and pipe axis orientations. Only minor differences in microstructure and texture properties were observed between the two alloys. Yet the 0.063% V alloy had from 8 to 14% higher yield and tensile strengths in all directions, while the toughness and ductility measurements were similar for both alloys. Higher strength of the V added pipeline steel was partially due to its smaller grain size and larger fraction of subgrain boundaries. Some, but perhaps not all, of the strength differences could be related to the observed smaller precipitate size of the higher vanadium steel. The vanadium addition was necessary in this alloy to ensure meeting the required strength properties of X100 steel.

Synthesizing higher nitride of molybdenum (Mo) and iron (Fe) in ammonia (NH3) gas stream under irradiation of concentrated solar beam in a solar furnace

AbstractFlowing gaseous ammonia NH3 with suppressed extent of dissociation (un‐cracked NH3) is acknowledged to function as a powerful nitriding medium to realize formation of metal nitride MNx with considerably high N/M ratio x that cannot be achieved through reaction of M with N2 gas. For example, mono‐nitride δ‐MoN of Mo and ε‐FeNx phase of Fe with x = 0.33 ˜ 0.50 (i. e. hypo‐stoichiometric sub‐nitride ε‐Fe2N) were reported to be difficult to prepare in N2 gas environment even at elevated pressure but might be synthesized in flowing NH3 gas at normal pressure when reaction temperature and NH3 gas flow rate were set adequately. In the present work, nitriding experiments for Mo and Fe were carried out in flowing NH3 gas under irradiation with concentrated solar beam. The acquired experimental evidences demonstrated that temperature range for formation of δ‐MoN was somewhat extended in flowing NH3 gas under heating with concentrated solar beam compared with that under heating in conventional laboratory or industrial electric furnace. On the other hand, no such merit of extending temperature range for formation of ε‐Fe2N in flowing NH3 gas was detected in the present work under heating with concentrated solar beam.

Cementing agents involved in the macro- and microaggregation of a Mediterranean shrubland soil under laboratory heating

The heating effect on aggregation and cementing agents of a Mediterranean soil was studied in two fractions (macro- and microaggregates) in different environments: under Quercus coccifera soil (UQ), under Rosmarinus officinalis soil (UR) and between plants or bare soil (BS). Samples were heated under laboratory conditions at different temperatures (220, 380, 500, 750 and 1000°C) to establish their effects on the studied soil properties by comparison with unheated control samples (25°C). Increasing temperature treatments caused significant changes in most soil variables. In both soil fractions, the presence of vegetation contributed to increase of the soil organic matter (SOM) content, which, in general, tended to decrease as temperature increased in all soils, reducing also their soil macroaggregate stability (SMS). Reduction in the stability of microaggregates (MSA) was not significant, possibly because the organic matter only controlled the stability of some of their fractions.Up to 500°C, the mean weight diameter (MWD), calcium carbonate (CaCO3) and extractable iron contents of macroaggregates presented different tendencies in all soils, but at 750°C relative maxima were observed in these three parameters, indicating a possible relationship between the potential re-aggregation of medium size macroaggregates into larger ones, and the increasing CaCO3 and extractable Fe contents. However, these newly formed “aggregates” would show low resistance to erosion as the decrease in SMS values suggested. The CaCO3 and extractable Fe contents of microaggregates in all soils tended to increase up to 750°C while their mean diameter (MMD) and stability hardly changed or tended to decrease. At 1000°C, the cementing agents showed their lowest values in each soil, while the macroaggregate stability tended to increase, and the mean diameter and stability of microaggregates reached their maximum values. This fact could be due to the possible re-aggregation of small fractions into large ones and some “hardening” processes that could have occurred. In general, the macro- and microaggregate stability appeared to depend on the organic matter content in all studied soils but, particularly, in those under canopy. The mean size of both fractions seemed to be controlled mainly by the calcium carbonate and iron contents.

Experimental simulation of oxygen isotopic exchange in olivine and implication for the formation of metamorphosed carbonaceous chondrites

AbstractWe have conducted hydration–dehydration experiments on terrestrial olivine to investigate the behavior of oxygen isotopic fractionation to test the hypothesis that multiple cycles of aqueous and thermal processing on a parent asteroid comprise a genetic relationship between CM2s and metamorphosed carbonaceous chondrites (MCCs). Two experiments were undertaken. In the first experiment, serpentine was obtained by hydrating terrestrial olivine (Fo90.9) in the laboratory. During this experiment, olivine was reacted with isotopically heavy water (δ18O 21.5‰) at T = 300 °C, = 300 bar, for 100 days. The oxygen isotopic composition of the experimental serpentine was enriched in 18O (by 10 ‰ in δ18O) due to exchange of oxygen isotopes between olivine and the 18O‐rich water. Dehydrated serpentine was then produced during laboratory heating experiment in vacuum, at T = 930 °C, for 1 h. The oxygen isotopic composition of the dehydrated serpentine was enriched in 18O by a further 7 ‰. The net result of the hydration–dehydration process was an enrichment of 18O in the final material by approximately 17‰. The new experimental results suggest that the oxygen isotopic compositions of MCCs of the Belgica‐like group, including Dhofar 225 and Dhofar 725, could be derived from those of typical CM2 chondrites via several cycles of hydration–dehydration caused by aqueous alteration and subsequent thermal metamorphism within their parent asteroids.

Plant species influence on soil microbial short-term response after fire simulation

Plant species can influence fire intensity and severity causing different immediate and long-term responses on the soil microbial community. The main objective of this work was to determine the role of two representative Mediterranean plant species as soil organic matter sources, and to identify their influence on microbial response before and after heat exposure. A laboratory heating experiment (300 A degrees C for 20 min) was performed using soil collected under Pinus hallepensis (PIN) and Quercus coccifera (KER). Dried plant material was added before heating for a total of six different treatments: non-heated control samples amended with the original plant material (PIN0 and KER0); PIN samples heated with pine (PINp) or kermes oak litter (PINk); KER samples heated with kermes oak (KERk) or pine litter (KERp). Heated soils were inoculated with the original fresh soil and different microbial parameters related to abundance, activity and possible changes in microbial community composition and chemical soil parameters that could be conditioning microbial response were measured for 28 days after inoculation. The effect of heating on the soil microbial parameters studied was influenced to a small extent by the plant species providing fuel, being evident in soil samples taken under pine influence. Nevertheless heating effect showed marked differences when plant species influence on soil origin was analyzed. In general, samples taken under pine appear to be more negatively affected by heating treatment than samples collected under kermes oak, highlighting the importance of vegetation as a fresh organic matter source in soil ecosystems before and after fire. (Less)

Development of Lean Duplex Stainless Steels (LDSS) with Superior Mechanical and Corrosion Properties on Laboratory Scale

Low-Ni and Ni-free varieties of duplex stainless steels (DSSs) have been successfully developed for the first time on laboratory scale in SAIL. The alloy compositions for Ni-free and low-Ni (<1.5 wt%) DSSs were evolved through formulation of appropriate chromium and nickel equivalents to achieve an optimum phase balance of 55 vol% austenite and 45 vol% ferrite in stainless steel microstructures. Laboratory heats were made achieving target chemistries and cast into 100 mm square cross-sectioned ingots. The ingots were subsequently soaked at 1150 °C for 3 hrs for thermal/ compositional homogenization and hot rolled in number of passes to 6 and 16 mm strips in Hillé experimental rolling mill with finish rolling temperatures of 950-980 °C. The hot rolled strips were eventually conferred solution annealing treatment by soaking them at 1060 °C for 2 hours followed by rapid quenching in water to prevent precipitation of deleterious intermetallic compounds (IMCs) and secondary phases. The new steels revealed an exceptional combination of properties: higher yield strength (488 MPa for low-Ni DSS and 501 MPa for Ni-free DSS), higher tensile strength (664 MPa for low-Ni DSS and 677 MPa for Ni-free DSS) and superior Charpy V-notch impact toughness (230 and 129 Joules at room temperature and -20°C, respectively, for low-Ni DSS as against 80 and 52 Joules at similar temperatures for Ni-free DSS). The yield strength of the steels was assessed to be about 1.6-1.8 times that of conventional austenitic grades AISI 304 L and AISI 316 L in annealed condition. The low-Ni and Ni-free DSS showed remarkable corrosion resistance and have been found to exhibit passivity, corrosion rates as low as 0.08-0.11 mpy, pitting potentials in the range of 482-596 mV and charge transfer resistances of the order of 106 W.cm2 in highly corrosive environment of 3.5% NaCl. The steels have been thus found to be superior in pitting/ localized corrosion resistance to AISI 304 L with pitting potential of 437 mV and comparable in performance with AISI 316 L with its high pitting potential of 602 mV. Even in the strongly reducing environment of 0.1 N H2SO4, the new steels have revealed tendency to passive film formation, breakdown potentials of 1127-1153 mV and passive film impedances of 104 W.cm2, comparable to the standard austenitic grades AISI 304 L and AISI 316 L. In boiling MgCl2 solutions, the low Ni DSS has been found to resist stress corrosion cracking (SCC) up to 24 h; the time for crack initiation being intermediate to that for AISI 304 L (3 h) and AISI 316 L (32 h). The Ni-free DSS, on the other hand, was found to exhibit no signs of SCC failure even after 72 h of exposure to the test solution. The degree of sensitization (DoS) for both low Ni and Ni-free DSSs has been quantified to be £ 0.05 in 0.5 M H2SO4 + 0.01 M KSCN, which has revealed their insusceptibility to intergranular corrosion (IGC). The steels have been found to be free from deleterious intermetallic phases such as sigma (s), chi (c), etc. and this has been ascertained from corrosion rates of <10 mdd in ferric chloride corrosion testing as per ASTM A 923 Method C.

Development of IFAC-1 SS: An Advanced Austenitic Stainless Steel for Cladding and Wrapper Tube Applications in Sodium-Cooled Fast Reactors

Fuel cycle cost of sodium cooled fast reactors (SFRs) is strongly dependent on the in-reactor performance of core structural materials, i.e., cladding and wrapper tube materials of the fuel subassembly, which are subjected to intense neutron irradiation during service, leading to unique materials problems like void swelling, irradiation creep and helium embrittlement. In order to increase the burnup of the fuel and thereby reduce the fuel cycle cost, it is necessary to employ materials which have high resistance to void swelling as well as better high temperature mechanical properties. The Indian fast reactor program began with the commissioning of the 40 MWtFast Breeder Test Reactor (FBTR). The core structural material of FBTR is 20% cold worked 316 austenitic stainless steel (SS). For the 5000 MetPrototype Fast Breeder Reactor (PFBR) which is in an advanced stage of construction at Kalpakkam, 20% cold-worked alloy D9 (14Cr-15Ni-Ti SS) has been selected as the cladding and wrapper tube material for the initial core. The target burnup of the fuel is 100 GWd/t. Advanced austenitic stainless steel and oxide dispersion strengthened steels are being developed for achieving fuel burnup higher than 100 GWd/t. An advanced alloy D9 containing controlled amounts of titanium, silicon and phosphorous has been developed. This alloy named as IFAC-1 (Indian Fast Reactor advanced Clad-1) SS is aimed at thermal creep properties comparable to that of alloy D9, and superior void swelling resistance upto a target burn-up of about 150 GWd/t. The nominal chemical composition of IFAC-1 SS is 14Cr-15Ni-.25Ti-.75Si-.04P. The chemical composition has been optimized after extensive evaluation of the tensile, creep and microstructural stability of fifteen laboratory heats with different amounts of titanium, silicon and phosphorous. Void swelling behavior was studied using ion irradiation. IFAC-1 SS contains higher levels of low melting eutectic phase forming elements such as phosphorous, and so is susceptible to solidification cracking. Extensive pulsed TIG welding trials have been carried out on IFAC-1 SS/316LN SS weld joints with varied weld parameters to find out the feasibility of obtaining solidification crack-free welds and the optimum welding parameters have been established. This paper gives an overview of the development of this advanced core structural material for SFRs.