Impact of plastic deformation on plasma induced damage and deuterium retention in tungsten

ABSTRACTRecent theoretical and subsequent experimental studies suggest that the uptake and release of deuterium (D) in tungsten (W) under high flux ITER-relevant plasma exposure is controlled by dislocation microstructure. Thanks to numerical calculations, a comprehensive mechanism for the nucleation and growth of D bubbles on dislocation network was proposed. The process of bubble nucleation can be described as D atom trapping at a dislocation line, its in-core migration, the coalescence of several D atoms into a multiple cluster eventually transforming into a nano-bubble. This view implies that the initial microstructure might be crucial for D uptake and degradation of the sub-surface layer under prolonged plasma exposure. In this work, we apply several experimental techniques to investigate the microstructure and mechanical properties of surface and sub-surface layer of W in recrystallized and plastically-deformed condition exposed to the high flux plasma. We use transmission and scanning electron microscopy, thermal desorption spectroscopy as well as nano-indentation measurements.

U, Th, Eu and colloid mobility in a granite fracture under near-natural flow conditions

SummaryLaboratory core migration experiments were performed in a granite fracture from the Grimsel Test Site (GTS, central Swiss Alps). The flow velocity was varied (46 m yr

Temperature-dependence of intramolecular coupling of active sites in pyruvate dehydrogenase multienzyme complexes

Intramolecular coupling of active sites in the pyruvate dehydrogenase multienzyme complexes of Escherichia coli, ox heart and Bacillus stearothermophilus was measured at various temperatures. As the temperature was raised, the extent of active-site coupling was found to increase, approaching a maximum near the physiological growth temperature of the organism. Under these conditions, a single pyruvate dehydrogenase (lipoamide) dimer appeared able to cause a rapid (20s) reductive acetylation of probably all 24 polypeptide chains in the dihydrolipoamide acetyltransferase core of the enzyme complex from E. coli at 37 degrees C, and of most if not all of the 60 polypeptide chains in the dihydrolipoamide acetyltransferase cores of the enzymes from ox heart and B. stearothermophilus at 37 degrees C and 60 degrees C respectively. Experiments designed to measure the inter-core and intra-core migration of enzyme subunits suggested that, in the bacterial enzymes at least, this was not a major contributor to active-site coupling.