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: Neutron & Zirconium alloy. The organization has 4845 authors who have published 4826 publications receiving 102951 citations.

Dynamics of Flexible Cylinders in Axisymmetrically Confined Axial Flow

Abstract: Experiments are described in which flexible cylinders placed centrally within a narrow cylindrical flow channel were subjected to axial flow. The dynamic behavior of such cylinders, either cantilevered or supported at both ends, is described, both in liquid and in simulated two-phase flows; the effect of several parameters, such as the annular confinement, was investigated. It was observed that, with increasing flow, the cylinder is subject sequentially to instabilities of increasing mode number, confinement severely destabilizing the system. The experimental observations are compared to a theoretical model for the dynamics of such systems. In the case of liquid flow, agreement is qualitatively good and quantitatively fair - keeping in mind the experimental difficulties. In the case of two-phase flows, theory and experiment do not agree.

A model for fission gas release and fuel oxidation behavior for defected UO2 fuel elements

Abstract: This paper is based on a number of in-and out-of-reactor experiments at the Chalk River Nuclear Laboratories, a physically based model developed to predict the activity release of radioactive noble gases from defected UO{sub 2} fuel elements during steady-state reactor conditions. This model has been interfaced with the ELESIM fuel-performance code, and verified against all-effects experiments in the National research Experimental reactor with defected elements containing various sizes and types of sheath failure, and operating at linear powers ranging from 22 to 67 kW/m up to a maximum burnup of 278 MW {center dot} h/kg U.

Kinetic energy and condensate fraction of superfluid 4 He

Abstract: A new method for the experimental determination of the condensate fraction, ${n}_{0}$, of superfluid $^{4}\mathrm{He}$ is presented. This method, which depends on the temperature variation of the average kinetic energy per atom, is applied to available neutron and x-ray data and yields values of ${n}_{0}$ that are consistent with those obtained from two previous methods. An analysis of the ${n}_{0}$ results from all methods gives the value ${n}_{0}=(13.3\ifmmode\pm\else\textpm\fi{}1.2)%$ at $T=0$. This value is in excellent agreement with the value obtained recently by Campbell from the observed surface tension but is slightly higher than most theoretical estimates. The temperature variation of ${n}_{0}$ near the $\ensuremath{\lambda}$ point, ${T}_{\ensuremath{\lambda}}=2.17$ K, is consistent with the expected form ${n}_{0}\ensuremath{\simeq}{({T}_{\ensuremath{\lambda}}\ensuremath{-}T)}^{2\ensuremath{\beta}}$ and the critical exponent is estimated to be $2\ensuremath{\beta}=0.5\ifmmode\pm\else\textpm\fi{}0.2$.

Neutron Capture γ-Rays from Titanium, Chromium, Iron, Nickel, and Zinc

Abstract: The neutron capture $\ensuremath{\gamma}$-rays emitted by the even-charge elements, from titanium to zinc, have been investigated with the aid of a pair spectrometer.Titanium emits a very simple spectrum. Two strong $\ensuremath{\gamma}$-rays, 6.756\ifmmode\pm\else\textpm\fi{}0.006 and 6.412\ifmmode\pm\else\textpm\fi{}0.006 Mev, are produced by capture in ${\mathrm{Ti}}^{48}$. Neither the direct transition to the ground state of ${\mathrm{Ti}}^{49}$, nor the transitions to the ground states of ${\mathrm{Ti}}^{48}$ and ${\mathrm{Ti}}^{50}$ were detected. From chromium the $\ensuremath{\gamma}$-rays corresponding to transitions to the ground state (9.716\ifmmode\pm\else\textpm\fi{}0.007 Mev) and to the first excited state (8.881\ifmmode\pm\else\textpm\fi{}0.007 Mev) of ${\mathrm{Cr}}^{54}$ are prominent and have intensities of 13 and 35 photons per 100 captures in ${\mathrm{Cr}}^{53}$. The direct transition to the ground state of ${\mathrm{Cr}}^{51}$ was not detected. The iron spectrum is dominated by a strong $\ensuremath{\gamma}$-ray with the energy 7.639\ifmmode\pm\else\textpm\fi{}0.004 Mev resulting from neutron capture in ${\mathrm{Fe}}^{56}$. This $\ensuremath{\gamma}$-ray is produced in the transition in ${\mathrm{Fe}}^{57}$ either to the ground state or to the excited state at 14 kev. Two weaker $\ensuremath{\gamma}$-rays with nearly equal energies close to 6 Mev are also produced in this isotope. The ground state $\ensuremath{\gamma}$-ray and the $\ensuremath{\gamma}$-rays leading to the first two excited states of ${\mathrm{Fe}}^{55}$ have been identified. Of these, the groundstate $\ensuremath{\gamma}$-ray (9.298\ifmmode\pm\else\textpm\fi{}0.007 Mev) is strong, about 50 photons per 100 captures in ${\mathrm{Fe}}^{54}$. A part of the counting rate ascribed to this $\ensuremath{\gamma}$-ray, however, may be due to the $\ensuremath{\gamma}$-ray producing the first excited state of ${\mathrm{Fe}}^{58}$ in a direct transition. The ground state $\ensuremath{\gamma}$-ray in ${\mathrm{Fe}}^{58}$ (10.16\ifmmode\pm\else\textpm\fi{}0.04 Mev) accounts for about 5 percent of all captures by ${\mathrm{Fe}}^{57}$. The nickel spectrum contains an intense $\ensuremath{\gamma}$-ray with an energy of 8.997\ifmmode\pm\else\textpm\fi{}0.005 Mev, which is produced in 50 percent of the captures in ${\mathrm{Ni}}^{58}$. Another prominent $\ensuremath{\gamma}$-ray at 8.532\ifmmode\pm\else\textpm\fi{}0.008 Mev may represent the transition to the ground state in ${\mathrm{Ni}}^{61}$; if so, it accounts for some 80 percent of captures in ${\mathrm{Ni}}^{60}$. From considerations of intensity, five of the remaining nickel $\ensuremath{\gamma}$-rays can be ascribed to transitions to excited states in ${\mathrm{Ni}}^{59}$. In the spectrum of zinc, few discrete $\ensuremath{\gamma}$-rays can be discerned above a background of unresolved radiations. Of these, a very strong $\ensuremath{\gamma}$-ray, with an energy to 7.876\ifmmode\pm\else\textpm\fi{}0.007 Mev, probably producing directly the ground state of ${\mathrm{Zn}}^{65}$, is emitted in 40 percent of neutron captures by ${\mathrm{Zn}}^{64}$.