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.

Neutron-Capture γ Rays from Various Elements

Abstract: Neutron-capture $\ensuremath{\gamma}$-ray spectra have been measured in the energy range 0.3 to 3 Mev by means of a two-crystal Compton scintillation spectrometer. The efficiency of the instrument as a function of energy was determined experimentally. The uniqueness of the 2.23-Mev $\ensuremath{\gamma}$ ray following capture of a neutron by hydrogen has been confirmed, and this $\ensuremath{\gamma}$ ray was used as a standard to establish the absolute intensity of $\ensuremath{\gamma}$ rays from other elements.Most of the $\ensuremath{\gamma}$ rays observed can be understood in terms of known levels, and many appear to be emitted in transitions from such levels to the ground state. In many cases, the information obtained complements high-energy data in establishing preferred modes of decay of the product nucleus.In sodium a very strong $\ensuremath{\gamma}$ ray is emitted from the first excited state of ${\mathrm{Na}}^{24}$ at 0.47 Mev, and another ground-state $\ensuremath{\gamma}$ ray appears to be emitted from the level at 1.34 Mev. The strongest $\ensuremath{\gamma}$ ray in the magnesium spectrum is an $E1$ transition between the levels at 3.41 and 0.58 Mev in ${\mathrm{Mg}}^{25}$. The aluminum spectrum is very complex, and only a few peaks have been resolved. A ground-state transition is seen from the level at 2.27 Mev in ${\mathrm{Al}}^{28}$.In silicon two $E1$ transitions are observed from the capturing level to the levels at 4.93 and 6.38 Mev, and a ground-state transition is seen from the first excited state at 1.28 Mev. Ground-state transitions are observed from the levels at 0.52, 1.15, and 2.18 Mev in ${\mathrm{P}}^{32}$. In sulfur, there is a strong ground-state $\ensuremath{\gamma}$ ray from the first excited state at 0.84 Mev, and a strong $E1$ transition to this level from that at 2.34 Mev.In chlorine almost all of the observed $\ensuremath{\gamma}$ rays can be understood as ground-state transitions from known levels in ${\mathrm{Cl}}^{36}$ at 0.79, 1.16, 1.95, 2.47, and 2.87 Mev. In ${\mathrm{K}}^{40}$ the decay scheme involves several level to level transitions. $\ensuremath{\gamma}$ rays to the ground state are observed from the levels at 2.05 and 3.40 Mev in ${\mathrm{K}}^{40}$, and possibly from the 1.18-Mev level in ${\mathrm{K}}^{42}$.The spectra from calcium and titanium are very simple. A strong $\ensuremath{\gamma}$ ray occurs almost once per capture in ${\mathrm{Ca}}^{40}$ from the 1.95-Mev first excited state of ${\mathrm{Ca}}^{41}$, and a strong $\ensuremath{\gamma}$ ray from the 1.39-Mev first excited state of ${\mathrm{Ti}}^{49}$ occurs almost once per capture in ${\mathrm{Ti}}^{48}$.In ${\mathrm{V}}^{52}$ most of the observed $\ensuremath{\gamma}$ rays are emitted by levels below 1 Mev. Ground-state transitions occur from the levels at 0.42 and 0.83 Mev. In ${\mathrm{Cr}}^{54}$ a very strong $\ensuremath{\gamma}$ ray to the ground state is emitted by the level at 0.84 Mev, and a weak transition may be from the 0.54-Mev level in ${\mathrm{Cr}}^{53}$ to the ground state.$\ensuremath{\gamma}$ rays to the ground state are observed from levels at 0.42 and 0.88 Mev in ${\mathrm{Ni}}^{59}$. No definite identification can be made of the four $\ensuremath{\gamma}$ rays observed from zinc. The ${\mathrm{Cd}}^{114}$ spectrum contains many unresolved radiations; by far the most intense is the 0.56-Mev $\ensuremath{\gamma}$ ray which is emitted from the first excited state.

Verification of a model for in-reactor creep transients in zirconium

Abstract: Time-dependent solutions to the rate equations describing the vacancy and interstitial concentrations in an irradiated metal have been used to predict the transients in the in-reactor creep rate of zirconium that would occur during reactor start-up or shut-down. It is predicted that both the application and removal of flux causes the in-reactor creep rate to exceed the steady-state rate. Experiments using a creep rig designed to be able to move in and out of the reactor core have shown that the flux enhancement of creep begins immediately and that the creep rate decreases continuously until steady state is reached. Similarly, the removal of flux causes the creep rate initially to increase, before decreasing to a negligible value. The good agreement between theory and experiment gives strong support to a model of flux-enhanced climb plus glide for the in-reactor creep of zirconium.

A mesh generator for automatically subdividing irregular polygons into quadrilaterals

Abstract: A method for meshing an irregular polygon with an arbitrary number of sides into quadrilaterals is described. The polygon is defined with reference to the coordinates of a set of primary nodes. The polygon sides are the lines joining these nodes and can be straight lines or arcs of circles. Each side may be further subdivided into an arbitrary number of equal length segments. The interior of the polygon is automatically subdivided into quadrilaterals with specification of the primary nodes, side subdivision and side curvature being the only requirements.