Turbulent flow of liquid lead alloy in oxygen-controlled corrosion erosion test facility

The CORELLA (CORrosion Erosion test facility for Liquid Lead Alloy) facility allows corrosion erosion tests in molten lead alloys at controlled oxygen content and temperature under flowing conditions. Its exposure chamber consists of a cylindrical container, partially filled with the liquid metal. An inner rotating cylinder drives the liquid metal flow. The specimens of interest are fixed vertically inside the chamber such that the lead alloy flows around the specimens on both sides. In this numerical study, the turbulent flow of liquid lead–bismuth eutectic is solved for various specimen configurations, filling heights, and rotational speeds of the inner cylinder. Hereby, the deformation of the free liquid surface is taken into account using a rotationally symmetric approximation. Highly turbulent flow is found even for 200 rpm (revolutions per minute), the lowest rotational speed investigated. The velocity of the liquid metal along the specimens’ lateral surfaces reaches values up to 1.5 m/s for a rotational speed of 1200 rpm, the limit of experimentally stable conditions. Due to the sudden flow constrictions and expansions around the specimens, a much higher effect of the flow on corrosion erosion is expected than for simple pipe flow at the same bulk velocity

Influence of Si addition on the corrosion behaviour of 9 wt% Cr ferritic/martensitic steels exposed to oxygen-controlled molten Pb-Bi eutectic at 550 and 600 °C

Three 9 wt% Cr ferrite/martensite steels (two alloyed with Si) have been exposed to oxygen-controlled LBE at 550 and 600 °C, respectively. The passivating oxide scale consists of a spinel layer plus internal oxidation zone (IOZ). By adding Si, the thickness of spinel layer is decreased while the IOZ is enhanced. Moreover, a Si-rich oxide layer is observed underneath the spinel layer on Si-containing samples after 2000 h exposure at 600 °C. Besides, the less visible cracks/exfoliations on Si-containing samples indicate the positive role of Si addition on scale adherence

Solid Surface Structure Affects Liquid Order at the Polystyrene/SAM Interface

We present a combined x-ray and neutron reflectivity study characterizing the interface between polystyrene (PS) and silanized surfaces. Motivated by the large difference in slip velocity of PS on top of dodecyl-trichlorosilane (DTS) and octadecyl-trichlorosilane (OTS) found in previous studies, these two systems were chosen for the present investigation. The results reveal the molecular conformation of PS on silanized silicon. Differences in the molecular tilt of OTS and DTS are replicated by the adjacent phenyl rings of the PS. We discuss our findings in terms of a potential link between the microscopic interfacial structure and dynamic properties of polymeric liquids at interfaces

A Fast Modular Semiconductor-Based Marx Generator for Driving Dynamic Loads

The challenging demands of pulsed electron beam devices (such as the GESA device) with respect to their pulsed power supply have led to the development of a new semiconductor-based Marx generator. At a maximum output voltage of 120 kV and 600-A pulse current for a duration of up to 100 μS, stepwise arbitrary output waveforms are desired. A fast rise time of the generator is achieved by using fast switching circuitry, low inductance capacitors, and a low inductance stage arrangement. For low jitter triggering of all stages and efficient signal transmission, the generator uses an optical bus system for communication. Due to the inherent dynamic load characteristics of the GESA device, the generator features a fast overcurrent protection scheme. This paper presents selected design aspects of the generator and their validation in a small-scale assembly able of delivering up to 8 kV at 600-A load current