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.

Weak pion-nucleon coupling strength: New constraint from parity mixing in 18F

Abstract: The circular polarization of the 1.081 MeV γ rays from 18F has been measured to be (1.7±5.8)×10-4. 18F was produced by a 4.05 MeV 3He+ beam impinging on a recirculating water target with a thin entrance window. The circular polarization was measured with four magnetic transmission polarimeters, each backed by a 150 cm3 n-type Ge detector. A fast data acquisition system limited overall peak losses to 30% at a count rate of 60 kHz per detector. Supplementary experiments were carried out to investigate the sensitivity of the circular polarization measurement to systematic variations of beam position and intensity. These effects were found to be negligible relative to the statistical uncertainty. The experimental result is interpreted in terms of an isovector parity-nonconserving matrix element between the ‖0+,T=1,1.042 MeV〉 and ‖0-,T=0,1.081 MeV〉 states in 18F that is dominated by the weak pion exchange contribution. The present result for the weak pion-nucleon coupling strength is ‖fπ1‖=(0.4-0.4+1.4)×10-7, which is significantly smaller than recent theoretical predictions based on the Weinberg-Salam model.

Systematic study of the lattice dynamics of the uranium rocksalt-structure compounds.

Abstract: The phonon-dispersion relations of USe and UTe have been determined by the inelastic scattering of thermal neutrons. All existing phonon measurements for the UX series, viz., UC, UN, UAs, USb, US, USe, and UTe, have been fitted to the rigid-ion and shell models and dispersion relations have been predicted for UP. The U-X force constants dominate the lattice dynamics and are nearly constant for the series, whereas the U-U force constants vary systematically from being large and positive for the compounds with the smallest lattice parameter to being negative for the chalcogenide series. The negative U-U force constant is identified with destabilizing f-d interactions. Elastic constants, derived from the slopes of the dispersion relations and from ultrasound velocity measurements, have been determined. The bulk modulus decreases unusually rapidly as the lattice parameter increases and is in fair agreement with band-structure calculations.

The Chemistry of Iodine in Containment

Abstract: Recent investigations of iodine behavior under radiolytic conditions have demonstrated that kinetics, not thermodynamics, will govern iodine speciation and partitioning under conditions typical of those expected in a reactor containment during an accident. In the presence of radiation, iodine volatility is orders of magnitude higher than that expected based on thermodynamic calculations. Kinetic studies have contributed extensively to the existing database of iodine chemistry and have several implications for modeling iodine behavior for safety analyses. For example, as a result of these investigations, many uncertainties in the iodine database, such as those regarding thermal oxidation of iodine, which were formerly regarded as reactor safety issues, are now considered to be relatively unimportant. In contrast, previously unconsidered factors, such as the effect on aqueous chemistry of impurities originating from surfaces, are now recognized as playing major roles in determining iodine volatility. An updated review of the existing literature regarding iodine behavior is provided, with a focus on recent developments. A critical evaluation of the data in the context of developing a model for iodine behavior under reactor accident conditions is also provided.