Potential Containment Materials Research Articles

Materialographic Preparation of Salt

Abstract Molten salt containing systems gain in importance for sustainable energy use and production. For research and development, interactions of molten salts with potential container materials are of major interest. This article introduces preparation procedures to display an intact metal and salt microstructure and their interface using light optical microscopy and scanning electron microscopy. The exemplary material combination is the ternary salt mixture NaCl-KCl-MgCl2 and the low alloyed steel 1.4901 (T92) with a maximum service temperature of 550 °C. These are potential elements/materials for use in latent heat thermal energy storages.

Experimental investigation of low velocity and high temperature solid particle impact erosion wear

Next generation Concentrating Solar Power (CSP) plants utilizing solid particles as the heat transfer medium (HTM) are expected to achieve greater operational efficiencies. However, the erosion from the solid particles can cause significant damage to component materials. Low particle speeds (1–2 m/s) are proposed as a means of preventing excessive damage to containment materials. Within the current investigation, solid particle erosion of three potential containment materials, stainless-steel grade 316L, a nickel alloy (Inconel 740H), and a refractory material (Tufcrete 60 M), are examined at a particle impact speed of 1.6 m/s. CarboBead-HSP 40/70 particles, a candidate HTM for CSP systems, impact the specimens at a relatively high impact angle of 60° based on containment design criteria. Experiments were conducted at ambient temperature and 800 °C to examine erosion of the materials at very low impact speeds and determine how temperature effects erosion. Initial results revealed surprising outcomes inconsistent with available literature: ambient temperature erosion of SS316L is an order of magnitude lower than IN740H, but erosion (erosion-corrosion) of SS316L at 800 °C surpasses IN740H by two orders of magnitude. Results suggest removal of oxide layers (erosion-corrosion) is responsible for the significant erosion that was observed even at these low particle speeds.

Review of liquid metal corrosion issues for potential containment materials for liquid lead and lead–bismuth eutectic spallation targets as a neutron source

Lead (Pb) and lead–bismuth eutectic (44Pb–56Bi) have been the two primary candidate liquid metal target materials for the production of spallation neutrons. Selection of a container material for the liquid metal target will greatly affect the lifetime and safety of the target subsystem. For the liquid lead target, niobium–1 wt% zirconium (Nb–1Zr) is a candidate containment material for liquid lead, but its poor oxidation resistance has been a major concern. In this paper, the oxidation rate of Nb–1Zr was studied based on the calculations of thickness loss resulting from oxidation. According to these calculations, it appeared that uncoated Nb–1Zr may be used for a 1-year operation at 900°C at P O 2 =1×10 –6 Torr, but the same material may not be used in argon with 5-ppm oxygen. Coating technologies to reduce the oxidation of Nb–1Zr are reviewed, as are other candidate refractory metals such as molybdenum, tantalum, and tungsten. For the liquid lead–bismuth eutectic target, three candidate containment materials are suggested, based on a literature survey of the materials’ compatibility and proton irradiation tests: Croloy 2-1/4, modified 9Cr–1Mo, and 12Cr–1Mo (HT-9) steel. These materials seem to be used only if the lead–bismuth is thoroughly deoxidized and treated with zirconium and magnesium.

Evaluation of the containment properties of geological and engineered barriers by pore-water extraction and characterization

Abstract In the construction of underground repositories for the disposal of potentially toxic wastes, it is critical to the development of a safety case that the chemical composition of waters flowing through the proposed containment barrier is fully understood. Because the barrier material is usually chosen to have low permeability, to minimize the risk of long-term transport of toxic material into the biosphere, it is often not possible to obtain sufficient flowing groundwater samples to allow complete hydrogeochemical characterization. In order to study the chemical composition of the water in these formations it is necessary, therefore, to use specialized pore-water extraction techniques. In this study, the practicalities of three methods for extracting and characterizing porewaters from potential containment materials are discussed. These are: (i) mechanical squeezing using a hydraulic press; (ii) centrifugation using a heavy liquid displacent; and (iii) aqueous leaching of residual salts from crushed core material. Three case studies are presented which demonstrate how each of the different pore-water characterization methods may be applied practically, and how the data obtained can prove invaluable in understanding the hydrogeochemistry of sites.

Compatibility of potential containment materials with molten lithium hydride at 800°C

A series of compatibility experiments has been performed for several stainless steels, carbon steels, and a nickel-base alloy in molten lithium hydride at 800°C for comparison with previous experiments on type 304L stainless steel. The results indicate that the mechanism of corrosion is the same for each of 304L, 304, 316L, and 309 stainless steel and that very similar corrosion in molten LiH is expected for each stainless alloy. Deviation from parabolic kinetics at extended exposure time for each stainless alloy is attributed in part to weight gains associated with lithium penetration. Stabilized (Nb and Ti) low carbon (< 0.06%) steels are observed to be essentially inert in LiH at 800°C with stable carbides and no grain growth. Mild steel (type 1020) is decarburized rapidly and exhibits extensive grain growth in LiH at 800°C. Both steels exhibit weight gains during exposure to molten LiH that are also related in part to lithium penetration. Alloy X (UNS N06002) exhibits extreme corrosion with essentially linear kinetics and dissolution of nickel sufficient to form subsurface voids.

Filler metals for containers holding irradiated fuel bundles

One of the procedures being considered for the disposal of Canada deuterium uranium (CANDU) irradiated fuel bundles is to place the bundles in containers, fill the containers with metal, and place them underground. This investigation deals with the selection of the filler metal with particular reference to the reaction rate with, and bonding of the filler metal to, the fuel sheathing (Zircaloy 4) and potential container materials. Lead, zinc, and aluminium alloys were examined as potential filler metals. It was observed that liquid lead and lead alloys do not react with Zircaloy 4, titanium, or Inconel 600, but do react with copper. Liquid zinc reacts with all the materials considered, at a rapid rate with copper, and at slower rates with the other materials. Liquid aluminium reacts very rapidly with all the materials examined, making it unsuitable as a filler metal. However, adding 7% silicon to the aluminium markedly decreased the reaction rate, except with copper. The bonding between the filler metal and the fuel sheath and container materials was directly related to the reaction which occurred. When no reaction occurred there was no bonding; with some dissolution there was good bonding. It was observed that the reaction rate did not change when the Zircaloy 4 was immersed in filler metal under stress, nor in the vicinity of Zircaloy 4 spacers brazed onto the fuel sheathing.