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A dissimilar metal weldment consisting of SA508-309L-308L-304L is widely used in light-water nuclear reactors. These weldments demonstrate dissimilar susceptibility to stress corrosion cracking that are related to the microstructure, properties, and residual stress. In this work, microstructures, hardness, and the residual stress distribution of the dissimilar metal weldments were investigated, with the correlation of increased hardness in the heat-affected zone (HAZ) to the microstructure. 304L HAZ demonstrated similar grain morphology as the base material, and the increase in hardness was primarily attributed to the increased dislocation density. SA508 HAZ demonstrated a change of grain morphology resulting from the different peak temperatures and cooling rates. The increased hardness in the SA508 HAZ was attributed to the refined grain morphology, higher dislocation density, and higher number density of precipitates. A ~ 20–30-μm-wide martensitic zone formed at the fusion boundary of SA508-309L, where Cr-rich carbide precipitates were observed, with the average size and the number density of 44.1 ± 16.9 nm and 1.5 × 1021 m−3, respectively. Residual stress results demonstrated the largest tensile stress at 309L butter, indicating its high cracking susceptibility.

The diffusivity of hydrogen is an important property of light water nuclear reactor (LWR) fuel cladding. LWR cladding absorbs hydrogen during normal operation, a contributing factor to embrittlement that decreases the lifetime of the fuel. Mass transport of hydrogen is dictated by an Arrhenius behavior typical of solid state diffusion and the associated activation energy is therefore a property relevant to LWR fuel performance. We have used incoherent quasi-elastic neutron scattering (QENS) to directly measure the diffusivity of hydrogen in recrystallized Zircaloy 2 with a hydrogen concentration of 170 μg/g. We rely upon the low-Q expansion for long-range diffusion to determine diffusivity as a function of temperature between 572 and 780 K. We find the diffusivity is given by D(T) = 0.0067 exp (-0.461 eV/kT) [cm2/s] below 670 K and by D(T) = 0.0012 exp (-0.36 eV/kT) [cm2/s] above 670 K. Our activation energy below 670 K agrees with the value typically used to assess hydrogen diffusivity in LWR cladding [Kearns, Journal of Nuclear Materials 43 (1972) 330], but is approximately 20% lower above 670 K. The two different activation barriers are attributed to impurity trapping of hydrogen solutes at lower temperature that ceases to influence diffusivity at higher temperature. The application of the Oriani model for diffusion with impurity trapping to our system demonstrates the plausibility of this hypothesis. We believe this mechanism may be responsible for historical discrepancies of measured hydrogen diffusivity in Zr-based alloys. The elastic intensity versus temperature in fixed window scans exhibit inflection points that are in good agreement with the published terminal solid solution solubility limits for hydrogen in Zircaloy 2.

Dry age-related macular degeneration (dAMD) is a chronic degenerative ophthalmopathy that leads to serious burden of visual impairment. Antioxidation in retinal pigment epithelium (RPE) cells is considered as a potential treatment for dAMD. Our previous studies have showed that naringenin (NAR) protects RPE cells from oxidative damage partly through SIRT1-mediated antioxidation. In this study, we tested the hypothesis that the Nrf2 signaling is another protective mechanism of NAR on dAMD. NaIO3-induced mouse retinopathy and ARPE-19 cell injury models were established. Immunochemical staining, immunofluorescence, and western blotting were performed to detect the protein expressions of Nrf2 and HO-1. In addition, ML385 (activity inhibitor of Nrf2) and zinc protoporphyrin (ZnPP, activity inhibitor of HO-1) were applied to explore the effect of NaIO3 or NAR. The results showed that NAR increased the protein expressions of Nrf2 and HO-1 in the retinas in mice exposed to NaIO3 at the early stage. NAR treatment also resulted in a stronger activation of Nrf2 at the early stage in NaIO3-treated ARPE-19 cells. Moreover, inhibition of HO-1 by ZnPP weakened the cytoprotective effect of NAR. The constitutive accumulation and activation of Nrf2 induced by NaIO3 led to the death of RPE cells. However, NAR decreased the protein expressions of Nrf2 and HO-1 towards normal level in the mouse retinas and ARPE-19 cells exposed to NaIO3 at the late stage. Our findings indicate that NAR protects RPE cells from oxidative damage via activating the Nrf2 signaling pathway.

The stability of intermetallic second-phase particles (SPPs) in coated Zircaloy-2 was studied in 700 °C steam environments up to 20 hours. Hydrogen generated from high-temperature steam oxidation of uncoated Zr-induced δ-hydrides formation in the Zircaloy matrix. Synchrotron XRD demonstrated that longer exposure times increased hydride peak intensity and decreased intermetallic SPPs’ peak intensity. Cross-sectional SEM analysis verified the intermetallic SPPs’ volume fraction reduction. The size distribution of intermetallic SPPs was characterized and larger particles were dissolved at longer oxidation time. A correlation between the hydrogen concentration and the volume fraction of intermetallic SPPs at 700 °C steam environment was found, with the volume fraction of SPPs decreasing as hydrogen concentration increases.

Zirconium-based alloys are common materials for light water reactor (LWR) fuel cladding. These alloys readily absorb hydrogen and are subjected to lose ductility due to hydride accumulation. A phase-field modeling code with Calphad-based free energy functions, Hyrax, has been used to model the hydrogen solvus in α -zirconium solution and the formation of the δ zirconium-hydride phase in the α -zirconium matrix. The modeled hydrogen solvus was compared against published experimental data; this is considered the first direct validation of Hyrax output. The effect of external stress on hydrogen solvus and hydride formation has also been modeled. A tensile stress was uniformly applied to a single zirconium crystal and a bi-crystal system. We observed that the stress does not affect hydrogen solvus but does cause hydride to accumulate in the crystalline which has the c-axis parallel to the stress direction. This is because the external stress creates a strain energy gradient across the system; the δ -hydride preferentially precipitates in the low strain energy region which yields more lattice misfit strain to compensate the gradient.

High-resolution neutron radiography has been used to image bulk circumferential hydride lens particles in unirradiated Zircaloy 4 tubing cross section specimens. Zircaloy 4 is a common light water nuclear reactor (LWR) fuel cladding; hydrogen pickup, hydride formation, and the concomitant effect on the mechanical response are important for LWR applications. Ring cross section specimens with three hydrogen concentrations (460, 950, and 2830 parts per million by weight) and an as-received reference specimen were imaged. Azimuthally anisotropic hydride lens particles were observed at 950 and 2830 wppm. The BISON finite element analysis nuclear fuel performance code was used to model the system elastic response induced by hydride volumetric dilatation. The compressive hoop stress within the lens structure becomes azimuthally anisotropic at high hydrogen concentrations or high hydride phase fraction. This compressive stress anisotropy matches the observed lens anisotropy, implicating the effect of stress on hydride formation as the cause of the observed lens azimuthal asymmetry. The cause and effect relation between compressive stress and hydride lens anisotropy represents an indirect validation of a key BISON output, the evolved hoop stress associated with hydride formation.

In situ neutron diffraction is utilized to study the deuteride (hydride) precipitation behavior in a cold-worked stress-relieved (CWSR) Zircaloy-4 material upon cooling from 420 °C to room temperature with a 78 MPa external stress applied along the rolling direction (RD) of the material. Two banks detector capture the diffraction signal from two principal directions of the specimen, the normal direction (ND) and the rolling direction (RD). The evolution of deuterium concentration in zirconium solid solution along the two specimen directions is measured by studying the δ -(220) peak intensity, applying the Rietveld refinement method to the diffraction data and using the measured zirconium c-axis lattice distortion. The deuterium concentration is observed to be higher for zirconium grains in the ND than the RD. The terminal solid solubility of precipitation (TSSp) for deuterium in the solution is then described using the Arrhenius equation. It is observed that the applied stress reduces the energy term Q in the Arrhenius equation when compared with the unstressed Q values from the work of others. A model by Puls is applied to study the effect of stress on deuterium solubility, with polycrystalline hydride precipitation strain calculated using the Kearns factor representative of the studied material. The experimental result does not agree with the model prediction of Puls.

Advanced ODS alloys provide exceptional radiation tolerance and high-temperature mechanical properties when compared to traditional ferritic and ferritic/martensitic (F/M) steels. Their remarkable properties result from ultrahigh density and ultrafine size of Y–Ti–O nanoclusters within the ferritic matrix. In this work, we applied a high-energy synchrotron radiation X-ray to study the deformation process of three advanced ODS materials including 14YWT, MA957, and 9-Cr ODS steel. Only the relatively large nanoparticles in the 9-Cr ODS were observed in the synchrotron X-ray diffraction. The nanoclusters in both 14YWT and MA957 were invisible in the measurement due to their non-stoichiometric nature. Due to the different sizes of nanoparticles and nanoclusters in the materials, the Orowan looping was considered to be the major strengthening mechanism in the 9-Cr ODS, while the dispersed-barrier-hardening is dominant strengthening mechanism in both 14YWT and MA957, This analysis was inferred from the different build-up rates of dislocation density when plastic deformation was initiated. Finally, the dislocation densities interpreted from the X-ray measurements were successfully modeled using the Bergstrom's dislocation models.

Background Dry age-related macular degeneration (dAMD) leads to serious burden of visual impairment and there is no definitive treatment. Previous studies have showed that naringenin (NAR) significantly increased electroretinography (ERG) c-wave in sodium iodate (NaIO3)-treated rats and viability of NaIO3-treated ARPE-19 cells. But the underlying mechanism is still unknown. Purpose We tested the hypothesis that anti-oxidation mediated by Sirtuin 1 (SIRT1) was important to the protective effect of NAR on dAMD. Study design/Methods NaIO3-induced mice retinopathy and ARPE-19 cells injury models were established. In vivo, the protective effect of NAR eye drops on retina was evaluated by flash ERG (FERG) recording and histopathological examination. In vitro, viability of ARPE-19 cells, and the levels of lactic dehydrogenase (LDH), reactive oxygen species (ROS) and carbonyl protein were detected. Protein expression of SIRT1 was analyzed by immunochemical staining, immunofluorescence and western blotting. Results NAR eye drops improved retinal function and morphology and normalized the protein expression of SIRT1 in mice exposed to NaIO3. NAR promoted the survival of ARPE-19 cells in a concentration-dependent manner. NAR up-regulated SIRT1 protein expression, and decreased levels of ROS and carbonyl protein. Moreover, EX527, a selective inhibitor of SIRT1, abolished the effects of NAR on the cell viability and ROS. In addition, SRT1720, a selective agonist of SIRT1, improved the viability of cells and suppressed the production of ROS. Conclusion Our findings indicate that SIRT1-mediated anti-oxidation contributes to the protective effect of NAR eye drops on dAMD.

We report on an inelastic neutron scattering study of the proton dynamics in ZrH0.0155 and e-ZrH2. In particular, we present measurements of the incoherent dynamic structure factor, generalized vibrational density of states, and proton momentum distribution of these two materials. Our results are generally consistent with theoretical predictions of Elsasser et al. [Mat. Res. Soc. Symp. Proc. 453 221–226 (1997)]. They argued that the effective Born-Oppenheimer potential experienced by the hydrogen atoms in e-ZrH2 is nearly isotropic and harmonic at energies below 0.3 eV, but becomes anisotropic and anharmonic for higher energies. At low temperatures, the proton momentum distribution is dominated by the quantum-mechanical ground state of the protons. We find that it assumes a Gaussian shape, consistent with the concept that the potential surface is approximately harmonic for small displacements of the hydrogen atoms. However, the anharmonicity of the potential becomes readily apparent in the excited states of the hydrogen atoms, as the harmonic approximation breaks down in the description of the multiphonon bands.

Small-angle neutron scattering (SANS) measurements have been performed under ambient conditions to characterize deuteride (hydride) particles in Zircaloy 4, a fuel cladding material used in pressurized light-water nuclear reactors. Hydrogen pickup by the cladding leads to a rim structure in which large circumferential hydride plate-like particles preferentially form on the cooler water-side region of the cladding. Deuterium substitution has been used to increase the coherent response and decrease the incoherent background of the SANS measurements. Four bulk deuterium concentrations were investigated, approximately 100, 400, 500 and 1000 parts per million by weight (w.p.p.m.) deuterium, as well as a zero-deuterium-concentration reference sample. The net SANS response from the deuteride phase was determined at all concentration values after subtraction of the reference SANS response, which effectively subtracted the strong scattering from second-phase particles in as-received Zircaloy. The net SANS response consisted of strong Porod scattering from deuteride particles over the entire measured Q range (0.005–0.4 Å−1). The net SANS response was anisotropic at concentrations greater than 100 w.p.p.m. and required elliptical averaging analysis. A significant sample orientation effect on the intensity of the SANS response was observed, due to preferential alignment of deuteride particles. The effect of ex situ applied stress at elevated temperature on deuteride phase dissolution and reprecipitation was investigated; a weak effect was observed with SANS that could not be confirmed by optical microscopy.

Hydrogels based on Poly(vinyl alcohol) (PVA) were synthesized using the combining method of chemical agent and freezing-thawing cycle. Sodium Trimetaphosphate (STMP) is a kind of crosslinking agent in this reaction. The resulting hydrogels were characterized in terms of tensile properties and compression stress-strain testing. The influences of STMP and water content on mechanical properties of hydrogels were investigated. It is suggested that PVA hydrogel has excellent tensile strength, higher elongation at break and viscoelastic materials’ stress-strain curve. Tensile strength of specimens without STMP increases from 4 to 6.8 MPa, as well as elongation increase from 300% to 458%, respectively. When the strain changes from 10% to 50%, tangent compressive modulus dramatically increases from 0.58 to 9.9 MPa for hydrogels with 80wt % water and 0.41 to 5.4 MPa for 85wt % water. Meanwhile, the addition of STMP can further improve the mechanical properties of PVA hydrogel.

High-energy synchrotron X-ray diffraction was utilized to study the mechanical response of the f.c.c $\delta$-hydride phase, the intermetallic precipitation with hexagonal C14 lave phase and the $\alpha$-Zr phase in the Zircaloy-4 materials with a hydride rim/blister structure near one surface of the material during in-situ uniaxial tension experiment at 200 \si{\degreeCelsius}. The f.c.c $\delta$ was the only hydride phase observed in the rim/blister structure. The conventional Rietveld refinement was applied to measure the macro-strain equivalent response of the three phases. Two regions were delineated in the applied load versus lattice strain measurement: a linear elastic strain region and region that exhibited load partitioning. Load partitioning was quantified by von Mises analysis. The three phases were observed to have similar elastic modulus at 200 \si{\degreeCelsius}.

To investigate effects of Danhong Huayu Koufuye (DHK), insulin and their combination on diabetic cardiomyopathy (DC) in streptozotocin (STZ, 50 mg/kg, ip)-induced diabetic rats.Rats were divided into five groups: normal control, diabetic treated with vehicle, insulin, DHK, and DHK plus insulin. The animals were treated once daily for 15 weeks starting one week after STZ injection.The combination of DHK with insulin significantly reduced cardiac index (P0.05), serum LDH (P0.05), AST(P0.05), ALT(P0.05) and HDL-C (P0.05) level, and promoted pancreatic and cardiac morphological changes as compared with the model group.It is suggested that DHK may be a valuable adjuvant therapy for DC.

To study the effects of danhong huayu koufuye (DHK) on fasting blood glucose (FBG) and diabetic retinopathy (DR) in streptozotocin (STZ)-induced type 1 diabetic rats to facilitate the rational usage of this drug.Diabetic rats were induced by injection of a single dose of STZ intraperitoneally at 50mg/kg. Flash electroretinogram (FERG) and oscillatory potentials (OPs) were used to measure retinal function. The microvascular perfusion of ears was performed to study the microcirculation in rats. FBG, body-weight, and 24-h urine volume, water intake and diet intake were also assessed.DHK had no effect on FBG in normal rats. However, STZ + DHK group were significantly different from those of Model and moved toward those of normal control. It reversed the increase in diet intake (P≤0.05 vs model control) and the loss in body-weight (P≤0.05 vs model control) in diabetic rats. DHK decreased the FBG of diabetic rats by 25.6% (P≤0.05) and 37.9% (P≤0.01) after 14 and 21 days administration as compared with the model control, respectively. Moreover, DHK significantly increased the FERG b-wave amplitude by 80% (P≤0.05 vs model control) and decreased the FERG b-wave latency by 15.3% (P≤0.01 vs model control) after 24 days administration. The OP(1) and OP(2) amplitudes in DHK group were 2.6 (P≤0.01) and 2.0 (P≤0.01) times of model group after 24 days of DHK treatment, respectively. At the same time, OP1 and OP2 latencies in DHK group reduced by 16.0% (P≤0.001) and 14.7% (P≤0.001) as compared with the model control, respectively. Furthermore, the microvascular perfusion of DHK group was 2.4 times of model group (P≤0.001) after 21 days administration.DHK had no effect on normal FBG. But it had antihyperglycemic activity, and had a preventive and therapeutic effect on DR in diabetic rats.