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.

EELS characterization of zirconium hydrides

Abstract: The energy of the first plasmon loss peak has been determined for the ~-Zr hydride phase in pure Zr. The peak energy is sufficiently different from that of the 03B4-hydride to permit EELS "fingerprinting" with ease using a parallel EELS system, but with greater difficulty using serial EELS, because of drift associated with the slower collection rates. Experiments on Zr-2.5Nb alloys showed that the hydride phases can also be distinguished using EELS, facilitating the analysis of hydride precipitates and blisters in nuclear reactor pressure tubes.

Local and Average Structures and Magnetic Properties of Sr2FeMnO5+y, y = 0.0, 0.5. Comparisons with Ca2FeMnO5 and the Effect of the A-Site Cation

Abstract: Sr2FeMnO5+y was synthesized under two different conditions, in air and in argon, both of which resulted in a cubic, Pm3m, structure with no long-range ordering of oxygen vacancies. The unit cell constants were found to be a0 = 3.89328(1) A for argon (y = 0.0) and a0 = 3.83075(3) A for air (y = 0.5). In contrast, Ca2FeMnO5 retains long-range brownmillerite oxygen vacancy ordering for either air or argon synthesis. Remarkably, Sr2FeMnO5.0 oxidizes spontaneously in air at room temperature. A neutron pair distribution function (NPDF) study of Sr2FeMnO5.0(Ar) showed evidence for local, brownmillerite-like ordering of oxygen vacancies for short distances up to 5 A. Mossbauer spectroscopy results indicate more than one Fe site for Sr2FeMnO5+y(Ar and air), consistent with the noncubic local structure found by NPDF analysis. The isomer shifts and quadrupole splittings in both air- and argon-synthesized materials are consistent with the 3+ oxidation state for Fe in sites with coordination number four or five. This...

Interplay Between Residual Stresses, Microstructure, Process Variables and Engine Block Casting Integrity

Abstract: The replacement of nodular cast iron with 319 type aluminum (Al) alloys in gasoline engine blocks is an example of the shift towards the use of lighter alloys in the automotive industry. However, excessive residual stress along the cylinder bore may lead to bore distortion, significantly reducing engine operating efficiency. In the current study, microstructure, mechanical properties and residual stress were characterized along the cylinder bridge of engine blocks following thermal sand reclamation (TSR), T7 heat treatment, and service testing of the casting. Neutron diffraction was effectively used to quantify the residual stress along both the Al cylinder bridge and the adjacent gray cast iron cylinder liners in the hoop, radial, and axial orientations with respect to the cylinder axis. The results suggest that an increase in cooling rate along the cylinder caused a significant refinement in microstructure at the bottom of the cylinder. In turn, this suggested an increase in alloy strength at the bottom of the cylinder relative to the top. This increased strength at the bottom of the cylinder likely reduced the susceptibility of the cylinder to rapid relief of residual stress at elevated temperature. In contrast, the coarse microstructure at the top of the cylinder likely triggered stress relief at an elevated temperature.

A Superheated Droplet Detector for Dark Matter Search

Abstract: We discuss the operation principle of a detector based on superheated droplets of Freon-12 and its feasibility for the search of weakly interacting cold dark matter particles. In particular we are interested in a neutralino search experiment in the mass range from 10 to 10^4 GeV/c^2 and with a sensitivity of better than 10^-2 events/kg/d. We show that our new proposed detector can be operated at ambient pressure and room temperature in a mode where it is exclusively sensitive to nuclear recoils like those following neutralino interactions, which allows a powerful background discrimination. An additional advantage of this technique is due to the fact that the detection material, Freon-12, is cheap and readily available in large quantities. Moreover we were able to show that piezoelectric transducers allow efficient event localization in large volumes.