Ultrasonic sensor to measure the density of a liquid or slurry during pipeline transport

This paper describes the design and testing of a computer-controlled sensor for the real-time measurement of the density of a liquid or slurry. It is to be deployed at the US Department of Energy's Hanford Site in Richland, WA, to monitor slurry properties during radioactive waste transfers. To demonstrate the sensor performance, tests were carried out using non-radioactive waste simulants and the results will be presented. The sensor is mounted flush with the pipeline wall in a nominal 5-cm (2-in.) pipe spool piece. The design pressure is 2.8 MPa (400 psi). The probe wedge in contact with the slurry was selected to operate up to pH 14, and the probe components were radiation tested at exposures of 1 x 10(6) R. The sensor is applicable for process control of all types of liquids or slurries in pipelines or in vessels.     

Some interruption criteria for short high-frequency vacuum arcs

If the contacts of a vacuum interrupter open shortly before a current zero, the transient recovery voltage (TRV) can cause a reignition and reestablish the arc. When the current in a diffuse vacuum arc passes through zero, there is a distinct pause before the TRV builds up (approximately 40 ns for copper). During this pause the gap carries conduction current only with an ion component which depends on dI /dt, varying between 3 A for dI/dt=60 A/μs and 60 A for dI/dt=1235 A/μs. The ion current subsequently decays in tens or hundreds of nanoseconds. It can be distinguished from the displacement current at this time by varying dV/dt, keeping the other parameters constant. Among the interruption criteria for short high-frequency vacuum arcs, dI /dt prior to current zero and initial dV/dt are the most important. High values of dI/dt are more likely to precipitate reignitions, but breakdowns can occur after lower dI/dt's if the gap has been subjected to a high current for a relatively long time (>100 μs)     

One-pot synthesis of novel 1,2,6,7-tetrahydro-3H-pyrazolo[4,3-c]pyridine-3,4(5H)-diones

A facile synthesis of novel 1,2,6,7-tetrahydro-3H-pyrazolo[4,3-c]pyridine-3,4(5H)-diones has been achieved. The operationally simple procedure, using readily available intermediates, allows for rapid derivatisation of the pharmacophore with alkyl, aryl and heteroaryl substituents.     

Preparation and structure of mixed tungsten bronzes containing tin and europium

An isothermal section has been established for the system Eu_xWO₃Sn_yWO₃ at 1000°C from X-ray powder and single-crystal data and Mössbauer spectroscopy and chemical analyses. A single-phase region with the (12 × 3) tetragonal structure has been established. Single-crystal X-ray analysis shows that the Sn and Eu occupy pentagonal tunnel sites. Mössbauer spectroscopy shows that both Sn(II) and Eu(II) are present. The extent of the single-phase field is controlled by two factors: First, the ratio $\text{Eu}\text{Sn}$ must be <1, and second, the supernumerary electron concentration per WO₃ must be <0.6.     

Harmonic renewal measures

Summary If C is a distribution function on (0, ) then the harmonic renewal function associated with C is the function . We link the asymptotic behaviour of G to that of 1–C. Applications to the ladder index and the ladder height of a random walk are included.     

A study of the magnetic superexchange interactions in the solid-solution series CaxSr1−xRuO3 by ruthenium-99 Mo¨ssbauer spectroscopy

Ruthenium-99 Mo¨ssbauer spectroscopy has been used to examine magnetic superexchange interactions in the distorted perovskite solid-solutions Ca_xSr_1?xRuO₃ (x = 0.1, 0.2, 0.3, 0.4, and 0.5). The end members of this series also have a slightly distorted perovskite structure but CaRuO₃ is Curie-Weiss paramagnetic, with only a single-line Mo¨ssbauer spectrum, whereas SrRuO₃ is ferromagnetic and shows a broad well-resolved hyperfine pattern. For x ? 0.2 a substantial proportion of the ruthenium atoms experience a magnetic flux density (hyperfine magnetic field) close to 35T, but inward collapse of the spectrum suggests that an increasing proportion of ruthenium atoms experience smaller flux densities. For samples with x ? 0.3 there is an intense central “paramagnetic” component which increases rapidly with increasing x. The observed behaviour is incompatible with a conventional localized electron structure but can be interpreted satisfactorily on a collective electron model in which the average spin moment and hence the magnetic flux density at any given ruthenium atom is proportional to the strength of the exchange interactions with the six nearest-neighbour ruthenium atoms. The results imply that the greater electron-pair acceptor strength (Lewis acidity) of Ca²⁺ compared to Sr²⁺ results in a more effective competition with ruthenium for the oxygen anion orbitals involved in the superexchange interaction. It appears that, for a ruthenium to have a coupled spin-moment, it must have at least two exchange interactions through cube faces containing at least three strontium atoms. Possible origins of the reduced magnetic moment of SrRuO₃ are discussed and it is suggested that the latter probably stems from spin-canting rather than from partial overlap of spin-up and spin-down bands.     

Parallel radioisotope collection and analysis in response to the Fukushima release

In order to co-recycle neptunium, uranium and plutonium using the PUREX process, numerical simulations were used to investigate the behaviors of neptunium in the first solvent extraction cycle. Counter-current extraction experiments using a miniature mixer-settler were performed to verify the simulation. Calculated results based on experiments show that the concentrations of nitric and nitrous acid, saturation of uranium, flow ratio and residence time have important effects on the pathway of neptunium, and accumulation of neptunium may appear with the presence of uranium and plutonium.     

Proton Magnetic Resonance Studies of Al(III) and Ga(III) Hydration Numbers in Aqueous Solution

Schweitzer and Stephens have recently suggested that the hydration numbers of Al³⁺ and Ga³⁺ and Ga³⁺ in aqueous solutions containing a considerable excess of chloride ion are probably less than six. Hydration numbers as low as 4.64 (in 1.44 M AlCl₃+ 2.15 M CaCl₂) or 4.61 (in 0.645 M GaCl₃+ 3.32 M CaCl₂) were obtained.¹ That Ga³⁺ forms chloro-complexes under these conditions is well known though interaction between Al³⁺ and chloride is considered unlikely in aqueous solution.^2–4