Atomic Energy of Canada Limited

About: Atomic Energy of Canada Limited is a company organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Zirconium alloy & Neutron. The organization has 4845 authors who have published 4826 publications receiving 102951 citations.

Fluidelastic Instability and Work-Rate Measurements of Steam-Generator U-Tubes in Air–Water Cross-Flow

Abstract: The dynamic response of U-tubes to two-phase cross-flow has been studied in tests involving a simplified U-tube bundle with a set of flat-bar supports at the apex, subjected to air-water cross-flow over the mid-span region. Tube vibration and the interaction between tubes and supports were measured over a wide range of void fractions and flow rates, for three different tube-to-support clearances. The vibration properties and tube-to-support work-rates could be characterized in terms of the relative influence of fluidelastic instability and random-turbulence excitation. For the first time, in a U-bend tube bundle with liquid or two-phase flow, fluidelastic instability was observed both in the out-of-plane and in the in-plane direction. This raises the possibility of higher-than-expected tube-to-support work-rates for U-tubes restrained by flat bars, particularly if fluidelastic instability, random turbulence and loose supports combine adversely.

Phonon Frequencies in NaBr

Abstract: The frequencies of phonons in NaBr at 295\ifmmode^\circ\else\textdegree\fi{}K propagating along the [001], [110], and [111] directions have been obtained from measurements of slow-neutron scattering made with a time-of-flight spectrometer and with a triple-axis spectrometer. The results have been fitted by least-squares techniques to both rigid-shell and deformable-shell models. The most satisfactory fit is obtained using a rigid-shell model with six disposable parameters and no second-neighbor force constants. Frequencies given by a variety of models with parameters determined by macroscopic constants are compared with the measured frequencies, and the effect of using zero-sound elastic constants is examined. The agreement is comparable to that found in other polarizable alkali halides. Finally, the frequency distribution at room temperature is obtained, and the temperature dependence of the specific heat and of the reduced moments are calculated with allowance for temperature-dependent quasiharmonic frequencies.

The influence of prior deformation on hydride precipitation in zircaloy

Abstract: Precipitation of hydrides has been studied in samples of Zircaloy subjected to prior tensile or compressive deformation before charging with hydrogen. The mean residual stress pattern in the alloys prior to charging was assessed by neutron diffraction techniques and provided a rough guide as to the preferred site of hydride nucleation. Heterogenous hydride nucleation at grain boudaries or twin boundaries was commonly found in samples subjected to 4% prior deformation, while transgranular hydrides were most frequently observed after a prior 1/2% compressive deformation or an annealing. The local stress state at grain boundary facets or twins is thought to be the deciding factor in determining where hydrides nucleate and how hydride stacks form.