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.

Structural and Magnetic Phase Transitions near Optimal Superconductivity in BaFe 2 ( As 1 − x P x ) 2

Abstract: In this study, we use nuclear magnetic resonance (NMR), high-resolution x-ray and neutron scattering to study structural and magnetic phase transitions in phosphorus-doped BaFe2(As1-xPx)2 Thus, previous transport, NMR, specific heat, and magnetic penetration depth measurements have provided compelling evidence for the presence of a quantum critical point (QCP) near optimal superconductivity at x = 03 However, we show that the tetragonal-to-orthorhombic structural (Ts) and paramagnetic to antiferromagnetic (AF, TN) transitions in BaFe2(As1-xPx)2 are always coupled and approach to TN ≈ Ts ≥ Tc (≈ 29 K) for x = 029 before vanishing abruptly for x ≥ 03 These results suggest that AF order in BaFe2(As1-xPx)2 disappears in a weakly first order fashion near optimal superconductivity, much like the electron-doped iron pnictides with an avoided QCP

The half-lives of 42Sc, 46V, 50Mn and 54Co

Abstract: As part of a broad program to determine f t values for superallowed O + → O − β transitions, the half-lives of 42 Sc, 46 V, 50 Mn and 54 Co have been measured with isotopically pure samples prepared with an on-line isotope separator. Emitted β + particles were observed with a large-solid-angle, high-efficiency, low-background gas proportional counter, from which signals were multiscaled. The counting electronics had a well-defined, non-extendable dead time. As no exact data analysis is possible, three different procedures were compared. The most stringent method involved regression analysis where a common half-life was simultaneously fitted to the individual decay curves of hundreds of samples and their Poisson statistical weights were distorted to reflect dead-time losses. The analysis procedures were tested on hypothetical decay data that were created by binning a time sequence of events, obtained from interval distributions reflecting the given half-lives and intensities of two decay components, and allowing for series and non-extendible dead times that reflected experimental conditions. On the basis of these tests it is demonstrated that the analysis does not introduce any bias at the 0.01% level. The deduced half-lives are 42 Sc : (680.67 ± 0.28) ms, 46 V : (422.57 ± 0.13) ms, 50 Mn : (283.29 ± 0.08) ms, 54 Co : (193.28 ± 0.07) ms. These results establish important elements in a demanding test of the Electroweak Standard Model.

TAF-ID: An international thermodynamic database for nuclear fuels applications

Abstract: The Thermodynamics of Advanced Fuels – International Database (TAF-ID) was developed using the Calphad method to provide a computational tool to perform thermodynamic calculations on nuclear fuel materials under normal and off-normal conditions. Different kinds of fuels are considered: oxide, metallic, carbide and nitride fuels. Many fission products are introduced as well as structural materials (e.g., zirconium, steel, concrete, SiC) and absorbers (e.g., B4C), in order to investigate the thermochemistry of irradiated fuels and to predict their chemical interaction with the surrounding materials. The approach to develop the database and the models implemented in the database are described. Examples of models for key chemical systems are presented. Finally, a few examples of application calculations on severe accidents with UO2 fuels, irradiated fuel chemistry of MOX and metallic fuels and metallic fuel/cladding interaction show how this tool can be used. To validate the database, the calculations are compared to the available experimental data. A good agreement is obtained which gives confidence in the maturity degree and quality of the TAF-ID database. The working version is only accessible to the participants of the TAF-ID project (Canada, France, Japan, the Netherlands, Republic of Korea, United Kingdom, USA). A public version is accessible by all the NEA countries. The current version contains models on the Am–Fe, Am–Np, Am-O-Pu, Am–U, Am–Zr, C–O–U-Pu, Cr–U, Np–U, Np–Zr, O–U–Zr, Re–U, Ru–U, Si–U, Ti–U, U-Pu-Zr, U–W systems. It is progressively extended with our published assessments. Information on how to join the project is available on the website: https://www.oecd-nea.org/science/taf-id/ .