bluuebunny/crossref_metadata_2025 huggingface dataset:
The unique activity of bone morphogenetic proteins in bone: a critical role of the Smad signaling pathway
Authors: Katagiri Takenobu , Tsukamoto Sho
Published: January 2013

Bone morphogenetic proteins (BMPs) are multifunctional cytokines that belong to the transforming growth factor-β family. BMPs were originally identified based on their unique activity, inducing heterotopic bone formation in skeletal muscle. This unique BMP activity is transduced by specific type I and type II transmembrane kinase receptors. Among the downstream pathways activated by these receptors, the Smad1/5/8 transcription factors appear to play critical roles in BMP activity. Smad1/5/8 transcription factors are phosphorylated at the C-terminal SVS motif by BMP type I receptors and then induce the transcription of early BMP-responsive genes by binding to conserved sequences in their enhancer regions. The linker regions of Smad1/5/8 contain multiple kinase phosphorylation sites, and phosphorylation and dephosphorylation of these sites regulate the transcriptional activity of Smad proteins. Gain-of-function mutations in one BMP type I receptor have been identified in patients with fibrodysplasia ossificans progressiva, a rare genetic disorder that is characterized by progressive heterotopic bone formation in the skeletal muscle. The mutant receptors activate the Smad signaling pathway even in the absence of BMPs, therefore novel inhibitors for the BMP receptor – Smad axis are being developed to prevent heterotopic bone formation in fibrodysplasia ossificans progressiva. Taken together, the data in the literature show that the BMP type I receptor – Smad signaling axis is the critical pathway for the unique activity of BMPs and is a potential therapeutic target for pathological conditions caused by inappropriate BMP activity.
Hypoxia-inducible factor prolyl 4-hydroxylases: common and specific roles
Authors: Myllyharju Johanna , Koivunen Peppi
Published: January 2013

Hypoxia-inducible transcription factor (HIF), an αβ dimer, is the key inducer of hypoxia-responsive genes that operate both during normal development and pathological processes in association with decreased oxygen availability. The products of HIF target genes function in, e.g., hematopoiesis, angiogenesis, iron transport, glucose utilization, resistance to oxidative stress, cell proliferation, survival and apoptosis, extracellular matrix homeostasis, and tumorigenesis and metastasis. HIF is accumulated in hypoxia, whereas it is rapidly degraded in normoxic cells. The oxygen-sensing mechanism behind this phenomenon is provided by HIF prolyl 4-hydroxylases (HIF-P4Hs, commonly known as PHDs and EglNs) that require oxygen in their reaction. In normoxia, two prolines in the oxygen-dependent degradation domain of the HIFα subunit become hydroxylated by the HIF-P4Hs. The 4-hydroxyproline residues formed serve as recognition sites for the von Hippel-Lindau E3 ubiquitin ligase complex and result in subsequent ubiquitination and instant proteasomal degradation of HIFα in normoxia. The HIF-P4H reaction is inhibited in hypoxia. HIFα evades degradation and forms a functional dimer with HIFβ, leading to activation of the HIF target genes. The central role of HIF-P4Hs in the regulation of the hypoxia response pathway has provided an attractive possibility as a drug candidate for treatment of, e.g., severe anemias and ischemic conditions, and several companies are currently carrying out clinical studies on the use of HIF-P4H inhibitors to treat anemia in patients with a kidney disease. Therefore, it is important to understand the effects of individual HIF-P4H isoenzymes on the hypoxia response and potential other pathways in vivo. The common and specific functions of the HIF-P4H isoenzymes are discussed in this review on the basis of available data from cell biological studies and gene-modified animals.
Interactions of graphene and graphene oxide with proteins and peptides
Authors: Zhang Yan , Wu Congyu , Guo Shouwu , Zhang Jingyan
Published: January 2013

This review selectively describes the recent progress in the interactions of proteins (enzymes) and short-chain peptides with graphene and graphene oxide (GO). Particularly, the advances of the immobilization mechanisms of enzymes on graphene and GO, the catalytic properties of the immobilized enzymes, and their applications are summarized in detail. The interfacings of the peptides with graphene and GO, the as assembled conjugates, and their potential applications are discussed briefly. The possible ongoing development for the assembly of conjugates of graphene and GO with proteins and peptides in a controlled manner is speculated upon.
Surfactant-free solution-based synthesis of metallic nanoparticles toward efficient use of the nanoparticles’ surfaces and their application in catalysis and chemo-/biosensing
Authors: Kawasaki Hideya
Published: January 2013

The choice of stabilizer and the stabilizer-to-precursor ions molar ratio during metal nanoparticle synthesis are important for controlling the shape, size, and dispersion stability of the nanoparticles. However, the active sites on the nanoparticles surfaces may be blocked by the stabilizing agents used, resulting in a less-than-effective utilization of the surfaces. In this review, various surfactant-free solution-based methods of synthesizing metal nanoparticles are described, along with the applications of such nanoparticles in catalysis and sensing. “Surfactant-free” synthesis does not imply truly bare metal nanoparticles synthesis but implies one where the metal nanoparticles are prepared in the absence of additional stabilizing agents such as thiolate and phosphine compounds, surfactants, and polymers. These metal nanoparticles are stabilized by the solvents or the simple ions of the reducing agents or low-molecular-weight salts used. Surfactant-free synthesis of metal nanoparticles via photochemical-, ultrasonochemical-, and laser ablation-mediated synthesis methods is also described. Because of the effective utilization of their surfaces, metal nanoparticles prepared without surfactants, polymers, templates, or seeds are expected to exhibit high performance when used in catalysis (synthetic catalysis and electrocatalysis) and sensing (surface-enhanced Raman scattering (SERS)), surface-assisted laser desorption/ionization-mass spectrometry (SALDI-MS)).
Approach of He/dpa Synergistic Effects in Iron-Based Materials Using JANNUS
Authors: Trocellier P. , Serruys Y. , Miro S. , Bordas E. , Martin H. , Beck L. , Pellegrino S. , Chaâbane N. , Vaubaillon S. , Meslin E. , Barbu A. , Brimbal D. , Henry J. , Robertson C. , Décamps B. , Fluss M. , Tumey S. , Hsiung L. , Schaüblin R. , Panigrahi B. K.
Published: January 2013

The JANNUS Saclay facility results from the coupling of three accelerators: a 3-MV Pelletron “Épiméthée,” a 2-MV Tandem “Japet,” and a 2.5-MV Van de Graaff “Yvette.” The Joint Accelerators for Nanosciences and Nuclear Simulation (JANNUS) Orsay facility is composed of a 200-kV TEM connected with two accelerators: a 2-MV Van de Graaff/tandem “Aramis” and a 190-kV ion implanter “Irma.” In the first part of this paper, after a brief description of both facilities, the performances allowed in terms of suppress the irradiation configuration will be presented and discussed. Then, we will illustrate the experiments that have been yet carried out involving accumulation damage (dose per atom (dpa)) and simultaneous He or He and H ion-beam irradiation. These experiments mainly concern pure α-Fe, model Fe–Cr alloys and Fe–Cr oxide-dispersion-strengthened (ODS) alloys. Finally, we will conclude by showing the near-future prospects scheduled to study He (+H)/dpa synergistic effects on ODS alloys and advanced ceramics and composites.
Modeling and TEM Investigation of Helium Bubble Growth in RAFM Steels Under Neutron Irradiation
Authors: Gaganidze E. , Dethloff C. , Weiß O. J. , Svetukhin V. , Tikhonchev M. , Aktaa J.
Published: January 2013

A model is developed to describe homogeneous nucleation and growth of helium bubbles in reduced activation ferritic/martensitic (RAFM) steels under neutron irradiation for timescales relevant to operation of a future fusion reactor. The model is based on kinetic rate equations for helium clustering, which are numerically solved by using a Fortran code. Model calculations are performed with helium production rates and helium contents adapted to ARBOR irradiation experiment, where helium effects were studied by irradiation of EUROFER97 based experimental steels doped with different contents of natural boron and separated 10B-isotope. The calculations, which are performed with effective helium diffusivity as a free parameter, yield the time evolution of the size distribution of helium clusters. The simulation results are very sensitive to the model parameters used. The simulated peak bubble diameter at the end of the irradiation experiments for different boron doped steels is between 2 and 8 nm depending on the model parameter. The transmission electron microscopy (TEM) investigation of a neutron irradiated boron doped steel revealed a homogeneous distribution of helium bubbles with no sign of preferential nucleation at microstructural sinks. Predominantly spherical appearance of the bubbles indicates a low helium density in the bubbles. By fitting the parameters the model yields a proper magnitude of peak bubble diameter and peak bubble density, though it still fails to properly reproduce the shape of the bubble size distribution. Possible reasons for this observation are discussed.
(U)HMWPE as Neutron Radiation Shielding Materials: Impact of Gamma Radiation on Structure and Properties
Authors: Wolff Dietmar , von der Ehe Kerstin , Jaunich Matthias , Böhning Martin , Goering Harald
Published: January 2013

Due to their extreme high hydrogen contents, high molecular weight (HMW-) and ultra-high molecular weight (UHMW-) polyethylene (PE) are a comprehensible choice as neutron radiation shielding material in casks for storage and transport of radioactive materials. But as a direct consequence of inserting radioactive material in such casks, gamma radiation occurs. Hence, the impact of gamma radiation on the molecular structure of polyethylene has to be taken into consideration. Consequently, PE has to withstand any type of gamma radiation induced degradation affecting safety relevant aspects in order to be applicable for long term neutron radiation shielding purposes during the whole storage period (in Germany, for instance, up to 40 years). The scope of our investigation comprises an estimation of the impact of gamma radiation and temperature on the molecular and supra molecular structure of the two types of PE used as neutron radiation shielding cask components. A further point which is worth exploring is to what extent these changes are detectable by conventional analysis methods. Therefore, thermoanalytical measurements were performed such as differential scanning calorimetry (DSC), thermo mechanical analysis (TMA), dynamic mechanical analysis (DMA), and thermo gravimetric analysis (TGA). Additionally optical and weighing methods were applied. With those methods it is possible to detect structural changes in polyethylene induced by exposure to gamma radiation. The observed amounts of changes of the irradiated material are not safety relevant for the application of polyethylene as neutron radiation shielding material; moreover, some properties actually improve via irradiation.
Long Term Irradiation Effects on the Mechanical Properties of Reactor Pressure Vessel Steels from Two Commercial PWR Plants
Authors: Efsing Pål , Rouden Jenny , Lundgren Martin
Published: January 2013

The Swedish nuclear power plants all have plant specific surveillance programs which includes samples from all relevant materials that are subjected to a fluence-level that exceeds 1*1017 n/cm2 over the estimated period of operation for the specific power plants. The Swedish pressurized water reactor (PWR)-plants are currently planning for a service period beyond 50 years of operation. As a portion of that, two of the three PWR units at the Ringhals site are conducting a major effort to verify the fitness to service of the reactor pressure vessel (RPV). In this case it is the weld in the belt-line region of the RPV, which is the apparent limiting factor. The weld metal contains high Nickel and high Manganese levels, not commonly used in other PWR-reactors. The effort includes a densified testing of the available surveillance capsule material in order to better understand the degradation phenomena and also an extended testing scope. A spin off effect of this program is that high fluence data for the base material also is made available from the testing. The chemical composition of the base metal is valid for many of the currently operating PWR-vessels. This study is an analysis of both the weld and the base material data extracted from the surveillance program. The results are evaluated against currently available data and correlation curves. In general, the results point out that the current Regulatory Guide 1.99 revision 2-correlation regarding the prediction of as-irradiated transition temperature is under-conservative for the tested material. The transition temperature shift, here evaluated as the temperature shift at 41J, is under-predicted by the correlation by as much as 70°C in some cases and increases with increasing fluences. However, prediction made by the French average irradiation embrittlement prediction formula, FIM-formula, is consistently better but still slightly under conservative.
Fracture Mechanics Characterisation of Forged Base Metal Ring of the Decommissioned Reactor Pressure Vessel of NPP Greifswald WWER-440 Unit 4
Authors: Viehrig Hans-Werner , Houska Mario , Altstadt Eberhard , Kuechler Roland
Published: January 2013

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant (NPP) representing the first generation of Russian type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs represent different material conditions, viz., irradiated, annealed and irradiated, and annealed and re-irradiated. This paper presents test results from measurements of the trepan taken from forged base metal ring 0.3.1. located in the reactor core region of the unit 4 RPV. This unit was shut down after 11 years of operation and represents the irradiated condition. The key part of the testing is focused on determination of the reference temperature T0 following ASTM E1921-10. The T0 of 11 thickness locations from the inner to the outer RPV wall varies between −112°C and −130°C, with a mean value of −121°C. These are very low values for WWER RPV steel irradiated with fluences between 5.4 and 1.2 × 1019 n/cm2 (E > 0.5 MeV) from the inner to the outer RPV wall. The fracture toughness values at cleavage failure KJc measured on LS oriented pre-cracked and side-grooved Charpy size SE(B) specimens from defined thickness locations of the forged ring show strong scatter. More than the allowed 2 % of the specimen size adjusted KJc-1T values lie below the fracture toughness curve for 2 % fracture probability. The application of modified master curve (MC)-based evaluation methods indicates that the material is non-homogeneous. Because of very low KJc values, the Structural Integrity Assessment Procedures for European Industry step 3 evaluation gave a maximum T0SINTAP of −40°C. The multimodal MC evaluation of KJc values from all thickness locations gives a T0MM of −118°C and a standard deviation of 25 K. The course of the fracture toughness curves evaluated via a multimodal approach also does not represent the measured KJc values, as more than 2 % lie below the fracture toughness curve for 2 % fracture probability. The reason for the occurrence of very low KJc values is intergranular planes detected on the fractured surfaces of the specimens.
Use of Vegetable Oils and Animal Oils as Steel Quenchants: A Historical Review—1850-2010
Authors: Simencio-Otero Rosa L. , Canale Lauralice C. F. , Totten George E.
Published: January 2013

Vegetable oils and animal oils have been used as quenchants for metals for thousands of years; however, it hasn't been until relatively recently that their cooling properties have been studied in a thorough, quantitative manner. This review will focus on the published data relating to the use of triglycerides from various animal and vegetable sources to quench-harden steels. Particular focus will be on the traditional selection and use of different vegetable and animal oils for steel hardening applications and the cooling time-temperature behavior of these fluids to characterize their quenching performance. This information has not been previously reviewed in this manner.
Explosion Cladding: An Enabling Technology for Zirconium in the Chemical Process Industry
Authors: Banker John G.
Published: January 2013

Zirconium is a commonly used material for containment of corrosive media by the chemical process industry (CPI). Zirconium's corrosion resistance is exceptional in a broad range of aggressively corrosive environments. However, zirconium is significantly more expensive than most of the alternative, but often inferior, corrosion resistant alloys. Explosion cladding has enabled CPI companies to cost effectively benefit from the superior performance features of zirconium in heavy-wall pressure vessels and heat exchangers. Explosion cladding is a unique technology that uses the energy of an explosive detonation to produce a metallurgical bond between metal plates. Since its discovery and industrialization in the 1960s, explosion cladding has proven to be a highly reliable, robust manufacturing technology. Zirconium clad has become a broadly accepted material of construction for a significant range of chemical process equipment. Zirconium clad equipment is used in manufacture of an extensive range of chemical products or intermediates including nitric acid, acetic acid, urea, and various organic acids. Zirconium clad and related design, manufacture, and fabrication processes have been shown to be highly reliable and to reduce both capital and operating cost.
Performance of Zirconium Alloys in Light Water Reactors with a Review of Nodular Corrosion
Authors: Franklin David G.
Published: January 2013

This paper provides historical context and future direction on selected contributions to understanding zirconium-alloy deformation and corrosion in light water reactors. More detailed discussion of the relative importance of electrochemical potential and hydrogen pickup on nodular corrosion is provided. Since nodular corrosion was observed about 50 years ago, several explanations have been proposed. None have explained all the observations, especially the sharp transition between nodular-free and nodular-covered regions of some fuel rods, with the transition being reversed between high- and low-power regions. However, the effect of electrochemical potential dominates any effects of hydrogen, other than the effect of hydrogen on electrochemical potential.
The Evolution of Microstructure and Deformation Stability in Zr-Nb-(Sn,Fe) Alloys Under Neutron Irradiation
Authors: Shishov V. N.
Published: January 2013

A review is given on the effect of neutron irradiation on the microstructure and properties of Zr–Nb and Zr–Nb–Fe (Sn,O) alloys. The in-reactor performance of Zr alloys is dependent on their composition and microstructure, and even small changes in the composition and processing lead to substantial changes in properties as a result of evolution of precipitates and matrix composition. The development of a new generation of alloys of Zr-Nb-Fe (Sn,O) system (that show higher resistance to the irradiation-induced growth, creep, and corrosion) required an examination of their micro-structure during the manufacturing process and evolution after neutron irradiation. The basic irradiation phenomena involve irradiation-induced damages (formation of the a- and c-component dislocations) and redistribution of alloying elements. The influence produced by precipitates containing Zr, Nb, and particularly Fe on the properties under irradiation is demonstrated. Relationships between composition, microstructure, and irradiation-induced growth of the Zr–Nb–Fe–Sn are described. An increased content of iron (over limit of the solubility) in Zr–Nb alloys leads to lower irradiation growth and creep and to strengthening of the matrix as a result of Fe leaving Laves phase (HCP) particles with their transformation into β-Nb (bcc). β-Nb precipitates become depleted in niobium (or enriched in zirconium), and finely dispersed irradiation-induced secondary particles enriched in niobium are formed. The basic microstructures that illustrate neutron damage structures, precipitates instability, evolution, and irradiation growth are shown and discussed.
Dynamic Recrystallization in Zirconium Alloys
Authors: Chakravartty J. K. , Kapoor R. , Sarkar A. , Banerjee S.
Published: January 2013

In this investigation, the characteristics of dynamic recrystallization (DRX) in five Zr-alloys, namely, commercial pure zirconium (CP-Zr), Zircaloy-2 (Zr–Sn), Zr-2.5Nb (Zr–Nb), Zr-2.5Nb-0.5Cu (Zr–Nb-Cu), and Zr-1Nb-1Sn-0.1Fe (Zr–Nb–Sn–Fe), have been examined. For this purpose, processing maps were constructed using strain rate sensitivity (m) data as a function of temperature and strain rate. This has been done using compression tests carried out at constant true strain rate. The processing maps revealed the bounds of DRX domain as iso-contour of m in strain rate-temperature plane. Optical microscopy and transmission electron microscopy (TEM) were used to analyze the evolution of the microstructure and to ascertain the nature of dislocation mechanisms in deformed and quenched samples from the DRX domain. For all the alloys studied, TEM revealed complete modification of β-transformed microstructure to an equiaxed morphology containing dislocation substructure within. The variation of grain size with strain rate and temperature, high ductility, and a linear variation of log(grain size) with log(Z) (where Z is the Zener-Hollomon parameter) are some important characteristic features associated with DRX domains of Zr-alloys. While Nb exhibited strong influence on lowering the strain rate for the occurrence of DRX of CP-Zr, Sn addition (Zr–Sn) did not alter DRX characteristics. TEM observations neither revealed the nature of nucleation event nor identified the dislocation mechanism involved in the DRX process. In order to ascertain the rate controlling dislocation mechanism, the flow stress data were analyzed using a model of thermally activated flow. On the basis of the magnitudes of activation energy and apparent activation area, the cross-slip of screw dislocation has been identified as the rate controlling mechanism involved in the DRX process. The activation energy has been found to increase by alloying elements, which is expected to lower stacking fault energy (SFE) and increase separation between the partials. Further analysis of the data using Friedel's model revealed that the activation energy for the cross-slip process can be decomposed into two parts—one related to the process of forming a constriction in the dissociated dislocations and the other needed for recombining the dissociated dislocations. While the former component (related to SFE) is dominant in Nb containing Zr-alloys, both the components are involved in controlling the deformation behavior of CP-Zr and Zr–Sn alloys. The effects of alloying elements on DRX characteristics and on the evolution of dislocation structure have been rationalized on the basis of cross-slip as the rate controlling dislocation mechanism in a qualitative manner. The importance of dynamic recovery in DRX process has been emphasized in view of this.
Measurement and Modeling of Second Phase Precipitation Kinetics in Zirconium Niobium Alloys
Authors: Ivermark Maria , Robson Joseph , Preuss Michael
Published: January 2013

Commercial zirconium alloys contain second phase particles (SPPs) that are precipitated during processing. These particles not only influence mechanical properties but more crucially also have a profound influence on the corrosion performance. To understand how to control evolution and size distribution of SPPs, it is necessary to know how alloy composition and process variables influence the precipitation kinetics. In this work, a detailed study has been performed of the precipitation kinetics in binary Zr-1 wt % Nb, Zr-2.6 wt % Nb, and ternary variants with added iron and tin. A numerical model has also been developed to predict the precipitation kinetics of β-Nb in niobium containing zirconium alloys. Precipitation has been tracked by synchrotron X-ray diffraction measurement of lattice parameter change in the zirconium matrix as solute is removed into SPPs. The X-ray data has been complemented by thermoelectric power measurements. The combination of these two approaches is shown to be effective in quantifying the overall precipitation kinetics of SPPs. The results confirm previous observations that without prior deformation, precipitation kinetics is very sluggish in the binary Zr-Nb system. Deformation accelerates precipitation, and this effect is much stronger for the 1 wt % Nb alloy than for 2.6 wt % Nb, because the supersatu-ration is least. Ternary additions also have a profound effect on the overall precipitation kinetics. Iron accelerates the rate of niobium loss from solution, whereas tin additions appear to increase the incubation time for the onset of precipitation of niobium.
Damage Build-Up in Zirconium Alloys During Mechanical Processing: Application to Cold Pilgering
Authors: Gaillac A. , Lemaignan C. , Barberis P.
Published: January 2013

Cold pilgering of zirconium alloys containing high content of alloying elements may be a critical issue regarding surface defects or serious cracks. A better knowledge of damaging mechanisms during pilgering is a way for optimizing the cold forming routes of cladding tubes. Behavior of Zircaloy-4, M5™ (M5™ is a trademark of AREVA NP) and Zr-Nb-Sn-Fe alloys under damaging conditions were investigated for this purpose. Cold pilgering is a cyclic deformation process. Depending on its position inside the grooves of the rolls, material is strained alternately in compressive and tensile modes. Thus, materials were first tested under low cycle fatigue (LCF) deformation routes. LCF tests showed that the differences observed in the number of cycles to failure between alloys are mainly a function of the differences in fracture toughness. Fractography of the fatigue and toughness tests samples also showed that the final propagation of the crack is always ductile, meaning that toughness is the function of the ductile tearing damage mechanisms at the crack tip. Therefore, tensile tests of notched axisymmetric samples were used to study the ductile damage build-up mechanisms, by varying the stress triaxiality. A detailed analysis of the fractured samples was used to quantify a ductile damage accumulation parameter, function of the deformation and the stress triaxiality. Size and repartition of second phase particles, grain to grain misorientations, grain size, and texture were identified as the main metallurgical parameters having an effect in the ductile damage by nucleation, growth, and coalescence of voids. These experimental results, combined with the material mechanical history, provided by numerical modeling of the cold pilgering process, are now used to improve the forming routes of cladding tubes, both by a mechanical way (cold pilgering stress state) and a metallurgical one (microstructure of alloys used for tubes rolling).
Statistical Analysis of Hydride Reorientation Properties in Irradiated Zircaloy-2
Authors: Valance S. , Bertsch J. , Alam A. M.
Published: January 2013

The orientation of hydrides in fuel cladding determines the anisotropic fracture behavior of Zircaloy and the failure modes of cladding tubes. Approach coupling experiments using the cladding tube deformation test and finite element analysis have successfully led to the quantification of the stress influencing reorientation of hydrides in unirradiated samples. An improved version of this procedure was applied to six samples of irradiated Zircaloy-2 from two different rods with three classes of thermo-mechanical loading. It was found that at medium maximum temperature, when no more than half of the hydrides were dissolved, the mechanical loading showed no measurable effect. When most of the hydrides were dissolved, the orientation and location of the hydrides depended strongly on the mechanical loading: The hydrides spatial location followed the hoop tensile stress. When the number of loading cycles was raised, the fraction of radial hydrides increased even for very low hoop tensile stress. The inner side of the cladding showed a marked depletion of hydrides whatever the size of the hoop stress. Since our test setup involved a tri-axial stress state, the possible influence of the other components of the stress tensor was evaluated. Through the use of a classical nucleation law, it was shown that for our test setup, the hoop stress was the important mechanical quantity. Therefore, the inner side depletion of hydrides may be attributed to three other factors: Residual stress, a memory effect, and a pumping effect by the inner liner.
Optimization of Zry-2 for High Burnups
Authors: Garzarolli F. , Cox B. , Rudling P.
Published: January 2013

Two major high burnup boiling water reactor (BWR) issues today are (1) shadow corrosion (hydrogen) induced fuel channel bowing and (2) accelerated hydrogen pickup fraction, HPUF of fuel claddings. Both these issues occur only at high burnups. Several factors impact the tendency for fuel channel bowing, the most recent one that is responsible for the current issue of difficulties to insert control rods is due to differences in hydrogen pickup of the different facing surfaces of the fuel channel. Accelerated HPUF of fuel cladding at high burnups may result in reducing fuel clad integrity during reactivity initiated accidents and cask drop accident during dry storage conditions. Some fuel vendors are now shifting from Zry-2 to Zry-4 in structural components to mitigate the fuel channel bowing issue. All BWR fuel vendors are also looking into new alloys (other than Zry-2 and Zry-4) for structural materials. However, one should keep in mind that it is imperative that a mechanistic understanding of the accelerated HPUF is developed to understand the accelerated HPUF tendency in Zry-2. Without such an understanding, it is not possible to rule out that accelerated HPUF can occur also for the new alloys under certain in-pile conditions. This paper summarizes the state of knowledge on the accelerated HPUF and provides suggestions on (1) the mechanism responsible for the accelerated HPUF of Zry-2 at high burnups and (2) how the currently used Zry-2 material for fuel rods and structural materials in BWRs can be modified to delay the accelerated HPUF at high burnups.
Impact of Irradiation Damage Recovery During Transportation on the Subsequent Room Temperature Tensile Behavior of Irradiated Zirconium Alloys
Authors: Bourdiliau B. , Onimus F. , Cappelaere C. , Pivetaud V. , Bouffioux P. , Chabretou V. , Miquet A.
Published: January 2013

Zirconium alloys are commonly used in pressurized water reactor as fuel rod cladding tubes. After irradiation and cooling in pool, the spent nuclear fuel assemblies are either transported for wet storage to a devoted site or loaded in suitable casks for dry storage on a nuclear power plant site. During dry transportation or at the beginning of dry storage, at temperatures around 400C, the cladding experiences a creep deformation under the hoop stress induced by the internal pressure of the fuel rod. During creep, a recovery of the radiation damage can occur that can affect the subsequent mechanical properties. The mechanical behavior of the cladding has been investigated in laboratory on two neutron irradiated cladding materials: fully recrystallized Zr-1 % Nb and stress-relieved Zircaloy-4. Creep tests under internal pressure were conducted at 400 and 420C. After depressurization and cooling, ring tensile tests were carried out at room temperature. In addition, transmission electron microscopy observations have been performed after testing. The post-creep mechanical response exhibited a decrease of the strength compared to the as-irradiated material. This decrease is associated with a significant recovery of the ductility, which becomes close to the ductility of the unirradiated material. The transmission electron microscopy examinations, conducted on recrystallized Zr-1 % Nb ring samples, revealed that the radiation defects have been annealed. It was also observed that as for the unirradiated material, the deformation occurred homogeneously throughout the grains. No dislocation channeling was observed contrary to the asirradiated material. These observations explain the recovery of the strength and of the ductility after post-irradiation creep that may also occur during dry transportation or at the beginning of dry storage.
Shadow Corrosion-Induced Bow of Zircaloy-2 Channels
Authors: Mahmood Sheikh T. , Cantonwine Paul E. , Lin Yang-Pi , Crawford Douglas C. , Mader E. V. , Edsinger K.
Published: January 2013

For the past 10 years, the frequency of channel-control blade interference has been greater than before because of shadow corrosion-induced bow. Shadow corrosion-induced bow is caused by differential hydrogen concentration on channel sides adjacent to and away from the control blade. The differential hydrogen concentration is a result of increased shadow corrosion on the channel side adjacent to the control blade, hence the description of this mechanism as shadow corrosion-induced bow. Channel bow measurements and post-irradiation examinations (PIEs) confirmed that shadow corrosion-induced bow occurs independent of fluence gradient-induced bow. Specifically, bow of channels that experienced early-life control (i.e., shadow corrosion) was significantly greater than expected assuming only fluence gradient-induced bow. In addition, it was found that plants with smaller channel-to-channel gaps had greater channel bow, consistent with the gap dependence of shadow corrosion. PIE revealed that the elevated hydrogen concentrations in the metal were found only on those channel sides and elevations that experienced shadow corrosion. A model was developed that related this measured differential hydrogen to the observed channel bow that supports the increased volume of hydrides as the underlying cause. However, questions about the time/exposure dependence of shadow corrosion-induced bow remain. The PIE of shadow corrosion-induced bow at low exposure (one cycle) indicates that little shadow corrosion-induced bow occurs after the first cycle even though shadow corrosion is observed on the side adjacent to the control blade. The differentials in oxide thickness and hydrogen concentration between opposite channel sides are considerably less than those measured later in service lifetime (i.e., after additional cycles of operation). The data indicate that the larger differential hydrogen at high exposure/residence time is a result of a larger difference in oxide thickness and a corresponding increase in percent hydrogen pick up that developed at higher exposures/residence times.
RIA Failure of High Burnup Fuel Rod Irradiated in the Leibstadt Reactor: Out-of-Pile Mechanical Simulation and Comparison with Pulse Reactor Tests
Authors: Grigoriev V. , Jakobsson R. , Schrire D. , Ledergerber G. , Sugiyama T. , Nagase F. , Fuketa T. , Hallstadius L. , Valizadeh S.
Published: January 2013

A high burnup boiling water reactor fuel rod was subjected to reactivity initiation accident (RIA) tests in a research reactor. Two ramp tests were carried out under almost identical irradiation conditions, resulting in cladding failure in a room temperature test, while no failure was observed in a high temperature test. An adjacent segment of the same rod was used for mechanical expansion-due-to-compression (EDC) testing simulating the pellet-cladding mechanical interaction loadings on the cladding during an in-reactor RIA. The EDC tests show the existence of a transition temperature where an abrupt increase in the specimen hoop strain at failure occurs. Additional tests revealed that the transition temperature depends on hydrogen concentration. A possible effect of the rapid heating, which is a specific condition for an in-reactor RIA compared to the static heating in the EDC tests, was verified in the rapid heating/loading tests on unirradiated hydrided Zircaloy, when both loading and heating are performed simultaneously within 50–80 ms. It was shown that strain to failure is dependent on the instantaneous material temperature and is not affected by the pre-heating history. The results show good consistency between the EDC and in-reactor pulse test data. It is concluded that the EDC test can provide valuable information to predict the in-reactor RIA fuel failure.
Fire Pattern Repeatability: A Study in Uncertainty
Authors: Madrzykowski Daniel , Fleischmann Charles
Published: January 2013

The National Institute of Standards and Technology (NIST) is conducting a multi-year study, with the support of the National Institute of Justice (NIJ) and the NIST Office of Law Enforcement Standards (OLES), to examine the repeatability of fire patterns. The primary objective of the study is assessing the repeatability of fire patterns on gypsum board exposed to a limited range of source fires. The focus of this paper is an overview of the uncertainties of the measurements. The study required the use of a variety of measurements to determine the repeatability of the source fires in terms of heat release rate, temperature, heat flux, and flame height. Replicate source fire experiments were conducted in an oxygen consumption calorimeter in order to examine the repeatability of the fires in terms of the heat release rate. The flame movement and height for each fire were recorded with photographs and videos. The fire pattern experiments were conducted in a threewalled structure with a full floor and partial ceiling constructed from wood framing and lined with painted gypsum board. The source fires were positioned against the rear wall, midway along its length. Replicate experiments were conducted with each fuel. The fire patterns were documented and analyzed for repeatability. The fire pattern height results are then compared to the mean flame height results to examine the level of agreement.
Sexual Consent as Voluntary Agreement: Tales of “Seduction” or Questions of Law?
Authors: Vandervort Lucinda
Published: January 2013

This article proposes a rigorous method to map the law on to the facts in the legal analysis of sexual consent using a series of mandatory questions of law designed to eliminate the legal errors often made by decision makers who routinely rely on personal beliefs about and attitudes toward “normal sexual behavior” in screening and deciding cases. In Canada, sexual consent is affirmative consent, the communication by words or conduct of “voluntary agreement” to a specific sexual activity, with a specific person. As in many jurisdictions, however, the sexual assault laws are often not enforced. Reporting is lowest and non-enforcement highest in cases involving the most common type of assailants, those who are not strangers but instead persons the complainant knows, often quite well—acquaintances, supervisors or coworkers, and family members. Reliance on popular narratives about “seduction” and “stranger-danger” leads complainants, police, prosecutors, lawyers, and trial judges to truncate legal analysis of the facts and leap to erroneous conclusions about consent. Wrongful convictions and perverse acquittals, questionable plea bargains and ill-considered decisions not to charge, result. This proposal is designed to curtail the impact of prejudgments, assumptions, and biases in legal reasoning about voluntariness and affirmative agreement and to produce decisions that are legally sound, based on the application of the rule of law to the material facts. Law has long had better tools than the age-old and popular tales of “ravishment” and “seduction.” Those tools can and should be used.
Pilloried in the Press: Rethinking the Constitutional Status of the American Perp Walk
Authors: Paciocco Palma
Published: January 2013

The perp walk is the practice, common among some American law enforcement agencies, of “walking” a criminal suspect before the press to be filmed. Perp walks have been challenged under the Fourth Amendment as unreasonable seizures of the person, but with limited success. This article examines the governing Fourth Amendment case law on perp walks. It finds the cases have deviated from conventional Fourth Amendment doctrine, instead establishing a bright-line rule based on an overstated distinction between different types of perp walks. The cases also overestimate the perp walk’s informative value while overlooking its punitive effects. Drawing on media studies, the article questions the claim that perp walks increase public access to the criminal justice system, arguing that they are necessarily distortionary media events. Drawing on both legal and anthropological sources, it goes on to suggest that perp walks are also inherently punitive events, akin to traditional shaming sanctions. Finally, the article offers a prescriptive analysis of how the perp walk cases can be brought back into line with Fourth Amendment doctrine and made to account for the perp walk’s distortionary and punitive effects.
Rapid Identification and Molecular Characterization of Phytoene Desaturase Mutations in Fluridone-Resistant Hydrilla (Hydrilla verticillata)
Authors: Benoit Lori K. , Les Donald H.
Published: January 2013

Florida hydrilla populations have shown an alarming increase in resistance to fluridone, an herbicide used extensively for controlling invasive US hydrilla populations. A rapid PCR and sequencing method was developed to identify and screen hydrilla genomic DNA for three previously identified phytoene desaturase (pds) gene mutations that confer resistance to fluridone. Ninety hydrilla accessions were screened for fluridone resistant genotypes including 46 accessions from the US and 44 accessions from 15 other countries. In Florida, hydrilla from five of nine sites tested was heterozygous for wild-type and herbicide-resistant alleles. Additionally, a new resistant population was identified from Lake Seminole in Georgia, the first genetically confirmed strain of resistant hydrilla outside of Florida. All resistance-conferring mutations were located on the same homologous haplotype of US dioecious hydrilla. All other hydrilla samples tested possessed only wild type alleles, including monoecious strains that had been exposed to fluridone. Management implications are discussed.
Growth Response of Itchgrass (Rottboellia cochinchinensis) to Water Stress
Authors: Chauhan Bhagirath S.
Published: January 2013

Greenhouse studies were conducted to evaluate the growth response of itchgrass to water stress. Itchgrass plants produced the greatest aboveground biomass and seeds at 75% of field capacity and these parameters at 50 and 100% of field capacity were similar. With further increase in water stress, seed production was sharply reduced, but itchgrass was still able to produce an average of 63 and 9 seeds plant−1at 25 and 12.5% of field capacity, respectively. Itchgrass plants responded to increasing water stress with increased leaf weight ratio; it was 2.5 times greater at 12.5% of field capacity than at 100% of field capacity. In another study, compared with daily irrigation, intervals of 9 d between irrigations reduced aboveground biomass of itchgrass by 27% and 12-d intervals reduced aboveground biomass by 67%. Compared with the daily irrigation regime, itchgrass seed production was reduced by 61% at intervals of 12 d between irrigations; however, the weed plants produced a considerable number of seeds (153 seeds plant−1) at the 12-d intervals. The ability of itchgrass to produce biomass and seeds under water stressed conditions necessitates strategies that minimize weed survival while maximizing irrigation efficiency for the crop at the same time.
Impact of Soil pH on Bahiagrass Competition with Giant Smutgrass (Sporobolus indicusvar.pyramidalis) and Small Smutgrass (Sporobolus indicusvar.indicus)
Authors: Rana Neha , Sellers Brent A. , Ferrell Jason A. , MacDonald Gregory E. , Silveira Maria L. , Vendramini Joao M.
Published: January 2013

Smutgrass is an invasive, well-rooted perennial that has long been recognized as an aggressive weed throughout Florida and in the subtropical regions of the United States. Small smutgrass and giant smutgrass are the two predominant smutgrass varieties found in Florida. The native soil pH of Florida flatwoods is 4.5 to 5.0 which is lower than the level of soil pH recommended for optimum bahiagrass growth. Therefore, replacement series experiments were conducted in a greenhouse in 2010 and 2011 to compare the competitive ability of bahiagrass with each of the two varieties of smutgrass at three levels of soil pH (4.5, 5.5, and 6.5), two densities; 4 (low) and 8 (high) plants pot−1, and at five planting ratios of 100 : 0, 75 : 25, 50 : 50, 25 : 75, and 0 : 100. Relative competitive ability and aggressivity of giant smutgrass was greater than bahiagrass across all pH levels and densities, whereas relative competitive ability and aggressivity of bahiagrass was greater than small smutgrass in all pH levels and densities, except at pH 6.5. At pH 5.5, biomass accumulation of giant smutgrass was at least 73% higher than bahiagrass, whereas small smutgrass biomass was at least 46% lower than bahiagrass at equal planting ratios of both low and high densities. Differential responses were observed on bahiagrass competitive ability with small and giant smutgrass. Amending soil pH is not a likely option to increase the growth and competitive ability of bahiagrass over giant smutgrass. However, for small smutgrass, it is likely to increase the aggressivity of bahiagrass in bahiagrass–small smutgrass mixture, unless the soil pH is raised above 5.5.
Herbicide Resistance Endowed by Enhanced Rates of Herbicide Metabolism in Wild Oat (Avenaspp.)
Authors: Ahmad-Hamdani M. S. , Yu Qin , Han Heping , Cawthray Gregory R. , Wang Shao F. , Powles Stephen B.
Published: January 2013

The biochemical basis of resistance to the acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicide diclofop-methyl was investigated in a resistant wild oat population (R1), which does not exhibit a resistant ACCase. Rates of foliar uptake and translocation of [14C]-diclofop were the same in the R1 vs. susceptible (S) populations. However, the level of phytotoxic diclofop acid was always found to be lower in the R1 vs. S plants, with a concomitant higher level (up to 1.7-fold) of nontoxic polar diclofop metabolites in R1 relative to the S plants. These results indicate that a non–target-site-based mechanism of enhanced rate of diclofop acid metabolism confers resistance in population R1. Moreover, the high-performance liquid chromotography elution profile of the major diclofop metabolites in R1 is similar to that of wheat, suggesting resistance in individuals of population R1 involves a wheat-like detoxification system mediated by cytochrome P450 monooxygenases. In addition, lower level of tissue diclofop acid was also observed using nonradioactive ultra-performance liquid chromatography–mass spectrometry analysis in resistant individuals of three other resistant wild oat populations (R2, R3, and R4) known to posses ACCase gene resistance mutations. These results establish that either one or at least two independent resistance mechanisms (target-site ACCase resistance mutations and non–target-site enhanced rates of herbicide metabolism) can be present in individual wild oat plants.