Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Probing the Room Temperature Deuterium Absorption Kinetics in Nanoscale Magnesium Based Hydrogen Storage Multilayers Using Neutron Reflectometry, X-ray Diffraction, and Atomic Force Microscopy

Abstract: Magnesium hydride has high storage capacity (7.6 wt % H) but very slow sorption kinetics. Addition of catalytic phases on the surface as well as alloying with transition metals is known to improve the properties. In this study, the sorption kinetics of a 50-nm Mg layer and Mg-10%Cr-10%V layer, capped with a CrV/Pd bilayer catalyst, are compared using a combination of neutron reflectometry (NR), X-ray diffraction (XRD), and atomic force microscopy to elucidate the effects of alloying on the hydrogen storage properties of Mg at room temperature. From NR it is found that the Cr–V alloyed layer shows both a delay in expansion in the first absorption cycle and a delay in contraction in the first desorption, which indicates a delay in nucleation of MgD2 and formation of substoichiometric MgD2-δ, respectively. Compared to pure Mg, the kinetics are strongly improved as no blocking MgD2 layer is formed. XRD showed a strong reduction in the Mg grain size for the Cr–V alloyed layer after one cycle. For pure Mg, the ...

The CECE alternative for upgrading/detritiation in heavy water nuclear reactors and for tritium recovery in fusion reactors

Abstract: The Combined Electrolysis Catalytic Exchange (CECE) process, utilizing AECL`s wetproofed catalyst, is ideally suited for extracting tritium from water because of its high isotopic separation factor and near-ambient operating conditions. Several CECE options are compared with the more conventional DW-VPCE arrangements for heavy water upgrading and detritiation of CANDU nuclear reactors and for detritiation of fusion facilities such as ITER. For both applications, CECE offers a more economical alternative over conventional technology. Experimental data on catalyst activity and lifetime are also presented and past commercial applications of the AECL catalyst are reviewed. AECL has recently committed to assembly of a CECE upgrading/detritiation demonstration facility. 15 refs., 5 figs., 1 tab.

Evidence for anisotropic polar nanoregions in relaxor Pb(Mg1/3Nb2/3)O3: A neutron study of the elastic constants and anomalous TA phonon damping in PMN

Abstract: We use neutron inelastic scattering to characterize the acoustic phonons in the relaxor Pb(Mg${}_{1/3}$Nb${}_{2/3}$)O${}_{3}$ (PMN) and demonstrate the presence of a highly anisotropic damping mechanism that is directly related to short-range polar correlations. For a large range of temperatures above ${T}_{c}\ensuremath{\sim}210$ K, where dynamic, short-range polar correlations are present, acoustic phonons propagating along [1$\overline{1}$0] and polarized along [110] (TA${}_{2}$ phonons) are overdamped and softened across most of the Brillouin zone. By contrast, acoustic phonons propagating along [100] and polarized along [001] (TA${}_{1}$ phonons) are overdamped and softened for a more limited range of wave vectors $q$. The anisotropy and temperature dependence of the acoustic phonon energy linewidth $\ensuremath{\Gamma}$ are directly correlated with neutron diffuse scattering cross section, indicating that polar nanoregions are the cause of the anomalous behavior. The damping and softening vanish for $q\ensuremath{\rightarrow}0$, i.e., for long-wavelength acoustic phonons near the zone center, which supports the notion that the anomalous damping is a result of the coupling between the relaxational component of the diffuse scattering and the harmonic TA phonons. Therefore, these effects are not due to large changes in the elastic constants with temperature because the elastic constants correspond to the long-wavelength limit. We compare the elastic constants we measure to those from Brillouin scattering experiments and to values reported for pure PbTiO${}_{3}$. We show that while the values of C${}_{44}$ are quite similar, those for C${}_{11}$ and C${}_{12}$ are significantly less in PMN and result in a softening of (C${}_{11}\ensuremath{-}{C}_{12}$) over PbTiO${}_{3}$. The elastic constants also show an increased elastic anisotropy [2C${}_{44}$/(C${}_{11}\ensuremath{-}{C}_{12}$)] in PMN versus that in PbTiO${}_{3}$. These results are suggestive of an instability to TA${}_{2}$ acoustic fluctuations in PMN and other relaxor ferroelectrics. We discuss our results in the context of the current debate over the ``waterfall'' effect and show that they are inconsistent with acoustic-optic phonon coupling or other models that invoke the presence of a second, low-energy optic mode.

Isolation of cold-sensitive Chinese hamster cells.

Abstract: Six cold-sensitive variants have been isolated from Chinese hamster ovary cells by the BUdR-visible light selection technique. The properties of one of these lines have been studied in detail. This line stops dividing immediately after a shift from 39° C to 33° C though its doubling time at 39° C is only slightly longer than that of wild-type cells. The rates of DNA and protein synthesis are severely reduced at 33° C, but the rate of RNA synthesis is not significantly different from wild-type cells. This line may be defective in protein synthesis, but the results of sedimentation analysis indicate that it probably has normal ribosomal subunit assembly.