Marten G. Barker

The solubilities of nickel, manganese and chromium in Pb17Li

Abstract The saturation solubilities of nickel and manganese in Pb17Li have been measured over the temperature range of interest for the use of Pb17Li as a coolant and tritium breeder in fusion reactors. Nickel was found to have a particularly high solubility in Pb17Li as given by the equation: Log 10 S (wppm) = 4.832−981.2/ T (K) for T = 520−728 K. The solubility of nickel in pure lead was also determined and found to be in good agreement with literature data. The solubility of manganese was found to be much lower than that of nickel in Pb17Li and is given by the equation: Log 10 s (wppm) = 6.732−2938/ T (k) for T = 531−783 K. The solubility of chronium was found to be very low and the data subject to too much scatter to be fitted to a sensible equation. The possibility of interference by oxygen dissolved in the Pb17Li is discussed. Equilibration measurements of the dissolution of Ni, Cr, Mn and Fe from Type 316 stainless steel are also described.

The interaction of chromium with nitrogen dissolved in liquid lithium

Abstract The ternary nitride, Li9CrN5, has been identified as the product of the reaction of paniculate chromium with nitrogen dissolved in liquid lithium, using X-ray powder diffraction (solid-state chemistry) and electrical resistivity (solution chemistry) methods; the minimum nitride activity required for the formation of this material is less than 0.0025 at 475°C. The reaction kinetics are first order with respect to dissolved nitride. Austenitic stainless steel (A1S1 316) also removes dissolved nitride from liquid lithium at 475°C with the formation of Li9CrN5 as the surface product. X-ray powder diffraction studies of the solid-state reactions between various molar ratios of lithium nitride and either chromium or chromium (III) oxide have been undertaken. Whereas reaction with chromium invariably yields Li9CrN5, reaction with chromium (III) oxide gives Li2O, CrN, Li9CrN5 and the solid-solution phase, Li 9 CrN 5 · 9 2 Li 2 O , in varying ratios. Differential thermal analysis of the lithium nitride-chromium reaction showed a large exothermic reaction at 706°C. The ternary nitride, Li9CrN5, and the solid-solution phase, Li 9 CrN 5 · 9 2 Li 2 O both crystallise with face-centered cubic anti-fluorite lattices with cell dimensions of 14.22 A and 4.72 A, respectively.

THe corrosion of chromium, iron, and stainless steel in liquid sodium

The corrosion products NaCrO/sub 2/ and Na/sub 4/FeO/sub 3/ were observed on the surfaces of chromium, iron, and stainless steel after exposure to liquid sodium at 600 deg C and above. The products were identified by x-ray diffraction without the removal of the covering sodium layer. (8 figures) (auth)

Layered ternary transition metal nitrides; synthesis, structure and physical properties

Abstract Two-dimensional structures are an emerging class of materials within nitride chemistry. We report here our systematic studies of two groups of these layered compounds: 1 Lithium transition metal compounds, Li3−x−y□yMxN (M=Co, Ni, Cu, □=Li vacancy) and 2 ternary transition metal nitrides of general formulation AMN2 (A=alkaline earth metal, M=Ti, Zr, Hf). Compounds in class 1 are based on the hexagonal Li3N structure, unique to nitrides. Compounds in group 2, by contrast, crystallise with oxide structures (α-NaFeO2 or KCoO2). Specific and unusual synthetic methods have been developed to reproducibly prepare these compounds. Compounds in series 1 contain ordered or disordered Li vacancies at increased levels relative to the parent Li3N, itself a Li+ fast ion conductor. Nitrides in series 2 should be nominally diamagnetic (S=0), yet magnetic measurements reveal behaviour seemingly inconsistent with this assumption.

The effects of carbon and nitrogen on the corrosion resistance of type 316 stainless steel to liquid lithium

Abstract Type 316 stainless steel plates have been exposed at 600°C to liquid lithium containing carbon and nitrogen at various chemical activities for periods of up to 672 h. The corrosion products Li 9 CrN 5 and M 23 C 6 have been identified on the plate surfaces and in the grain boundaries. Scanning electron microscopy has shown preferential nickel and chromium depletion at the steel surface in lithium with high nitrogen content. The diffusion coefficient of carbon in type 316 stainless steel from a lithium source was found to be 6.5 × 10 t 1 5 m 2 /s.

An electrical resistivity monitor for the detection of composition changes in Pb17Li

Abstract An electrical resistivity monitor for the detection of composition changes in the lithium-lead eutectic alloy, Pb17Li, has been developed. A miniature electromagnetic pump is used to sample alloy continuously from a pool or loop system and force it through a capillary section, within which the necessary resistance measurement are made, prior to its return to the bulk source. To calibrate the monitor, detailed resistivity-temperature and resistivity-composition data have been determined for PbLi alloys at temperatures from 600 to 800K and composition from 0 to 20.5 at% Li. The resistivity increases with both temperature and composition; for Pb17Li at 723 K, d ϱ /d T = 0.054×10 −8 ω K −1 and d ϱ /d[K] = 1.27×10 −8 ω m(at% Li) −1 . The sensitivity of the monitor is such that changes in composition of as little as ±0.05 at% Li can be detected and its response time is limited solely by the rate of sampling.

Corrosion of Type 316L stainless steel in Pb-17Li

Abstract Corrosion tests carried out in Pb-17Li in both capsules and a convection loop (hot leg temperature 768 K, cold leg temperature 748 K, flow rate 10 mm/s) have shown that Type 316 stainless steel undergoes almost complete loss of Ni and Mn, and extensive loss of Cr to form a porous ferritic zone. Ferritic zone depths measured on the loop samples exposed between 1000 and 4000 h were in good agreement with previous data. Some evidence was found for the interaction of chromium with oxygen dissolved in Pb-17Li. Examination of the cold leg samples revealed deposition products of iron and chromium but no deposits containing nickels were observed. These observations were rationalised in terms of recent measurements of the solubilities of metals in Pb-17Li.

Is Pb-17Li really the eutectic alloy? A redetermination of the lead-rich section of the Pb-Li phase diagram (0.0 < xLi(at%) < 22.1)

The lead-rich eutectic of the Li-Pb system has been shown to lie, not at 17 at% Li, but at 15.7(2) at% Li. In a reassessment of the phase boundaries (0 3.0 at% Li. The technological ramifications of the redetermined eutectic are limited since at 250°C, a single liquid phase is maintained over the composition range from 13.7 to 18.0 at% Li, and separation of a solid phase from, Pb-17Li will occur only at temperatures below 243°C.

An investigation of the sodium-cerium-oxygen system

Abstract A study of the sodium-cerium-oxygen system has been carried out at temperatures between 400 and 800° C, and a possible ternary phase diagram has been proposed. The system is characterized by two ternary compounds, Na 2 CeO 3 and NaCeO 2 ; the latter compound is reported for the first time.

The corrosion of molybdenum and tungsten in liquid sodium

Abstract The corrosion of molybdenum and tungsten has been examined in static and dynamic liquid sodium. Corrosion of molybdenum was not found to be oxygen dependent; no ternary oxide corrosion products were observed. Inclusion of labile carbon into the system containing molybdenum caused the formation of molybdenum carbide, Mo2C, which was identified by its powder X-ray diffraction pattern. The corrosion of tungsten was found to be strongly influenced by the initial concentration of dissolved oxygen in the liquid metal; at low oxygen levels in the dynamic system the cubic phase, Na3WO4 ( a 0 = 4.62 A ), was identified by its X-ray diffraction pattern recorded through a matrix of sodium, whereas, at initially very high oxygen levels in static systems, the orthorhombic phase, Na6WO6, was identified. The solid-state interaction of sodium oxide with molybdenum and tungsten metals under vacuum give the ternary phases Na4MoO5 and Na6WO6, respectively, together with unreacted refractory metal and sodium vapour.