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.

Strong Influence of the Diffuse Component on the Lattice Dynamics in Pb(Mg1/3Nb2/3)O3

Abstract: The temperature and zone dependence of the lattice dynamics in Pb(Mg 1/3 Nb 2/3 )O 3 is characterized using neutron inelastic scattering. Through a detailed study of the phonon lineshape and a comparison of the structure factors to SrTiO 3 , we conclude that the coupling between the acoustic and optic modes is weak. However, based on a direct comparison between the (110) Brillouin zone where the diffuse scattering is strong to the (220) zone where the diffuse scattering is weak, a strong coupling between the diffuse component and low-energy acoustic phonon mode is observed. We conclude that the coupling to the diffuse component is the reason for several recent conflicting interpretations of the lattice dynamics based on data from zones with a strong diffuse component.

Beta-ray dose distributions from point sources in an infinite water medium.

Abstract: The ACCEPT Monte Carlo code has been used to calculate radial dose distributions around isotropic point sources of monoenergetic electrons between 0.01 and 10 MeV in an infinite water medium. The results were averaged over beta spectra to derive distributions for 147 beta emitters of which 32 are presented. More extensive tables of distributions will be presented in a report. Distributions for monoenergetic electrons agree with recent ETRAN-code calculations of Berger and Seltzer within 2%, except at very short distances where there are differences up to several percent. Results calculated by the EGS4 code differ by up to a few percent. Distributions for beta emitters are in excellent agreement with both experimental results and ETRAN and EGS4 calculations, except at very short distances.

Comparison of three different techniques for measuring the residual stresses in an electron beam-welded plate of Waspaloy

Abstract: The longitudinal, transverse, and through-thickness (short-transverse) residual stresses in an electron beam-welded plate of WASPALOY, a high-strength nickel-based superalloy, have been characterized using neutron diffraction, X-ray diffraction, and a hole-drilling method. Where possible, the results from the different techniques, and the associated uncertainties, have been compared. For the neutron measurements, the γ/γ′ {111} peak was used for the determination of lattice strains. The X-ray measurements were carried out using Fe Kα radiation, the sin2ψ technique, and the {311} γ/γ′ composite peak. The Matthar-Soete method was used for the incremental hole-drilling measurements. Unfortunately, due to texture effects, it was not possible to detect the residual stresses within the weld metal by the diffraction-based methods. For the estimation of residual stresses, plane-specific values of the Young’s modulus and Poisson’s ratio were determined from tensile testpieces using in situ neutron diffractometry. When these data are used, it is found that the neutron, X-ray, and hole-drilling residual stress data are mutually consistent, although the absolute certainties vary with the method employed. The results indicate that, next to the weld, the longitudinal residual stresses approach 1000 MPa and are typically far greater (up to 5 times) than those in the transverse and through-thickness directions. Measurements of the longitudinal strain with distance along the welding direction indicate that the stress state reaches a steady state over the central portion of the plate; for this reason, the majority of the diffraction measurements have been made in the plane perpendicular to the weld at the center of the plate. A simple analysis of the thermal cycles and the extent of plastic deformation induced in the specimen is presented. The plastic “upset zone” has a size which is at least 3 times greater than the cross-sectional area of the weld metal; this suggests that, for accurate analysis of weld-induced distortion, attention should be paid to the evolution of residual stresses in the heat-affected zone as well as the fusion zone.