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.

Residual stresses in steel and zirconium weldments

Abstract: Three-dimensional scans of residual stress within intact weldments provide insight into the consequences of various welding techniques and stress-relieving procedures. The neutron diffraction method for nondestructive evaluation of residual stresses has been applied to a circumferential weld in a ferritic steel pipe of outer diameter 114 mm and thickness 8.6 mm. The maximum tensile stresses, 250 MPa in the hoop direction, are found at mid-thickness of the fusion zone. The residual stresses approach zero within 20 mm from the weld center. The residual stresses caused by welding zirconium alloy components are partially to blame for failures due to delayed-hydride cracking. Neutron diffraction measurements in a GTA-welded Zr-2.5 Nb plate have shown that heat treatment at 530 C for 1 h reduces the longitudinal residual strain by 60%. Neutron diffraction has also been used to scan the residual stresses near circumferential electron beam welds in irradiated and unirradiated Zr-2.5 Nb pressure tubes. The residual stresses due to electron beam welding appear to be lower than 130 MPa, even in the as-welded state. No significant changes occur in the residual stress pattern of the electron-beam welded tube, during a prolonged exposure to thermal neutrons and the temperatures typical of an operating nuclearmore » reactor.« less

Relationship between the unbinding and main transition temperatures of phospholipid bilayers under pressure.

Abstract: Using neutron diffraction and a specially constructed high pressure cell suitable for aligned multibilayer systems, we have studied, as a function of pressure, the much observed anomalous swelling regime in dimyristoyl- and dilauroyl-phosphatidylcholine bilayers, DMPC and DLPC, respectively. We have also reanalyzed data from a number of previously published experiments and have arrived at the following conclusions. ~a! The power law behavior describing anomalous swelling is preserved in all PC bilayers up to a hydrostatic pressure of 240 MPa. ~b! As a function of increasing pressure there is a concomitant decrease in the anomalous swelling of DMPC bilayers. ~c! For PC lipids with hydrocarbon chains >13 carbons the theoretical unbinding transition temperature T ! is coupled to the main gel-to-liquid crystalline transition temperature TM . ~d! DLPC is intrinsically different from the other lipids studied in that its T ! is not coupled to TM . ~e! For DLPC bilayers we predict a hydrostatic pressure ( .290 MPa) where unbinding may occur.