Liquid Plutonium Research Articles

ICONE19-43987 ATOMISTIC STUDY ON THE EUTECTICS FOR METALLIC FUEL AND COMPONENT MATERIALS IN CDAs OF SFRs : (3) SIMULATION OF THE ATOMIC DIFFUSION ACROSS THE INTERFACE BETWEEN PLUTONIUM AND IRON BY CLASSICAL MOLECULAR DYNAMICS

Eutectic melting between metallic fuel and steel cladding and/or steel structures is one of dominant phenomena for the progress of core disruptive accidents (CDAs) of SFRs. In this study the atomic diffusion at the interface between Pu and Fe was investigated by using classical molecular dynamics (CMD). The simulation was performed using Modified Embedded Atom Method (MEAM) (Baskes, 1992). For plutonium the potential model developed by Baskes (2000) was used and for iron that by Lee et al.(2001) was applied. The interactions between plutonium and iron atoms were calculated by using the potential model determined so as to reproduce the material properties of PuFe_2. The simulation was made with a system in which a semi-infinite, two-dimensional plate of iron with a thickness of 2.5 nm was in contact with solid or liquid plutonium with almost same thickness as the iron plate. The diffusion of atoms across the interface was observed for all the temperature conditions in the present study (900K〜1850K). The diffusion rate was increased exponentially with temperature. The diffusion rate depended on the plane direction of the surface of the iron plate as well as the temperature.

Dr Smith goes to Los Alamos

Long before the complex pressure-temperature phase diagram of plutonium (shown below) was determined, Cyril Stanley Smith’s suggestion that adding small amounts of some impurity atoms to liquid plutonium might retard its undesirable transformation to the brittle alpha phase enabled the fabrication of the world’s first nuclear device tested successfully in New Mexico on July 16, 1945.

Predicted transport properties of liquid plutonium

The fluid-phase transport properties, diffusivity and viscosity, are calculated by equilibrium and nonequilibrium techniques for plutonium, whose interatomic interactions are described by the modified embedded-atom method. The transport coefficients are evaluated at zero pressure, for temperatures between 950 K and 1300 K. We find the calculated viscosity to be noticeably higher than experiment, while the structure of liquid Pu appears to be similar to other liquid metals.

The optical properties of liquid plutonium at 632.8 nm

The optical properties and normal, spectral emissivity of liquid plutonium at 632.8 nm were measured over a temperature range of 2016–2189 K using rotating analyzer ellipsometry. The purity of the liquid was maintained in a containerless environment using electromagnetic levitation and heating. The material investigated contained 1 wt% Ga that was added during the casting process. The measured values of the optical property results are given as a function of temperature by ϵ λ =5.38×10 −5 T+0.250, n λ =−1.29×10 −4 T+3.82, and k λ =−7.04×10 −4 T+5.77 over the investigated temperature range.

Safety characteristics of the multipurpose fast reactor (MPFR)

The safety characteristics of a long-life multipurpose nuclear reactor (MPFR) with self-sustained liquid metallic fuel and lead coolant, which is proposed to meet the requirements for the energy production in the future, were investigated. The application of liquid plutonium–uranium metallic alloys used as a nuclear fuel demonstrated high potential to reach excellent reactor shutdown characteristics against anticipated transients without scram such as unprotected loss-of-flow and unprotected transient overpower. The calculations indicated that the thermal expansion of liquid fuels would cause the negative reactivity insertion that would be larger in magnitude than any other thermally induced reactivity changes. This created the reactivity balance for the passive shutdown and power stabilization capabilities of the MPFR core. It was found that MPFR satisfies such design characteristics to be a potential candidate providing the replacement of fossil fuels by alternative energy sources in the next century.

What's new on plutonium up to 4000 K?

The thermophysical properties of both solid and liquid plutonium have been investigated up to 4000 K and 0.12 GPa by use of the isobaric expansion experiment (IEX). Electrical resistivity, volume expansion (density), enthalpy, sound velocity, and equation of state parameters (bulk modulus, adiabatic and thermal compressibility, Grüneisen parameter, and the specific heat ratio) have been measured and extended in the whole liquid region up to nearly 4000 K, and are reported in this paper. Among numerous anomalies of Pu, the literature data have revealed that liquid Pu shows an atypical behavior by presenting a positive temperature coefficient for sound velocity up to 1225 K. We have confirmed such a behavior but also reported a drastic change of sound velocity at around 2000 K. Such results are interpreted in terms of the delocalization of the 5f electrons in liquid Pu.

The concept and neutronic characteristics of a multipurpose fast reactor (MPFR)

The paper describes a concept and its neutronic characteristics of a long-life multipurpose nuclear reactor with self-sustained liquid metallic fuel, which is proposed to meet the requirements for the energy production in the future. The application of the liquid plutonium–uranium metallic alloys as a nuclear fuel demonstrates high potential to reach excellent conversion characteristics and high burn-up values with relatively small reactivity swings. Considerations about the capability of in-vessel separation of the main fission products to prolong the core lifetime without fuel reloading or shuffling are also discussed from the viewpoint of the influence on core burn-up characteristics.

Criticality calculations for plutonium metal at room temperature in ionic liquid solutions

Critical mass calculations performed on two plutonium metal/ionic liquid mixtures are presented and the results are compared with similar calculations performed on aqueous systems. The ionic liquids considered are the 1-ethyl-3-methyl imidazolium (EMI)/ aluminum chloride (AlCl 3) and the EMI/tetrafluoroborate (BF 4) systems. Our calculations indicate at least an order of magnitude increase in the minimum critical concentration for the ionic liquid–plutonium mixtures over aqueous mixtures. The minimum critical concentrations calculated for Pu/EMIC/AlCl 3 and Pu/EMI/BF 4 mixtures are 150 and 1000 g/l, respectively.

Corrosion-resistant erbium oxide coatings by organometallic chemical vapor deposition

An organometallic chemical vapor deposition (OMCVD) process was developed for the preparation of protective erbium oxide coatings resistant to corrosion by liquid plutonium. The coatings were deposited from the precursor compound Er(tmhd) 3 using a standard hot-wall reactor. The substrates used for process development were 304 stainless-steel flats; coatings were subsequently deposited on the internal surfaces of high-aspect-ratio tubular parts, as well as a variety of curved samples. The coatings have the correct oxygen/erbium ratio, and small concentrations of carbon and hydrogen impurities. The impurities are present in the form of unreacted or partially-reacted precursor molecules, presumably concentrated at the grain boundaries of the material. The films are polycrystalline with a grain size of 40–50 nm, and exhibit excellent adhesion and mechanical toughness. The small grain size and the resultant favorable mechanical properties may be attributable in part to the presence of the organic fragments at the grain boundaries. Coatings deposited on stainless-steel flats are resistant to corrosion by liquid plutonium, although an erbia-thickness threshold is observed. The failure mechanism for samples with thicknesses below the threshold value is most likely related to flaws in the film morphology, for example large pinholes, rather than grain-boundary attack.

The thermodynamics of vaporization of neptunium and plutonium

The vapor pressure of liquid neptunium was determined over the temperature range 1540 to 2140 K by a combination of mass-effusion and mass-spectrometric measurements. The measured pressures are given by log 10 “p o(Np)/atm ’ = −(22370 ± 95)K T + (5.196 ± 0.056) and the resulting enthalpy and entropy of vaporization and the standard deviations therein are ΔH v o(Np, 1800 K) = (102.4 ± 0.4) kcal th mol −1 and ΔS v o(Np, 1800 K = (23.8 ± 0.3) cal th K −1 mol −1. The enthalpy of sublimation at 298 K is estimated as ΔH s o(Np, 298 K) = (110 ± 2) kcal th mol −1. The vapor pressure of plutonium was redetermined over the temperature range 1210 to 1620 K. The results yield log“p o(Pu)/atm’ = −(17120 ± 114)K T + (4.592 ± 0.082) , ΔH v o(Pu, 1400 K) = (78.3 ± 0.5) kcal th mol −1, and ΔS v o(Pu, 1400 K) = (21.0 ± 0.4) cal th K −1 mol −1. The measured pressures are 20 to 30 per cent less than those of two previously reported absolute measurements. Based on a recent assessment of the thermal functions for solid and liquid plutonium, the results of the present study show the best second-third law agreement, i.e., ΔH s o(II, Pu, 298.15 K) = (82.8 ± 0.5) kcal th mol −1 and ΔH s o(III, Pu, 298.15 K) = (83.3 ± 0.4) kcal th mol −1.

Distribution of americium between liquid plutonium and a fused salt. Evidence for divalent americium

The distribution of Am between liquid Pu metal and a fused salt of NaClKCl containing PuCl 3 has been studied at 698, 730 and 775°C over a PuCl 3 mole fraction range of 6 × 10 −3 to 2 × 10 −2. The distribution data are consistent with the following equation ▪ From the temperature dependence of the equilibrium constant, a value of −3.5 kcal is estimated for ΔH° for the above reaction.

Liquid Plutonium — A Review of its Physical Properties

The published measurements of the physical properties of liquid plutonium and its alloys are reviewed. The unusually high viscosity is noted along with the low value for the heat of fusion and the ...

Effect of Oxygen and Nitrogen in Tantalum on its Resistance to Corrosion by Liquid Plutonium Alloys

The effect of oxygen and nitrogen content of tantalum on its resistance to corrosion by molten plutonium-cerium-cobalt alloys was investigated. The impurity content of the tantalum ranged from 100-...

The Development of High Purity Tantalum and Alloys for Liquid Plutonium Containment in LAMPRE I

By combining arc casting and electron beam melting, spectroscopically pure tantalum and alloys, suitable for containment of molten Pu-Fe alloys, were produced. The 0.1% W alloy was used for the first LAMPRE loading. The effects of a large number of additives on the corrosion resistance of tantalum were tested. Additions of up to 10% tungsten gave increasing endurance. Specimens of tantalum irradiated with neutrons until 3% converted to tungsten were stitl satisfactory in mechanical properties for reactor use. Either tungsten or the traces of yttrium remaining after arc melting can raise the one-hour recryatatlization temperature of tantalum by 400 deg C. Effects of internal strain, critical strain and precipitation hardening in tantalum alloys were studied. High-temperature annealed tantalum had superior corrosion resistance, while impact extruded and ironed material was better than deep-drawn metal. Mechanical tests on tantalum with added interstitial elements showed that their presence to the extent expected in LAMPRE would be unlikely to weaken the tantalum. Evidence was found that oxygen promotes plutonium attack on tantalum. Small amounts of hydrogen, nitrogen and carbon had no effect on corrosion. (auth)

The Vapor Pressure of Plutonium Halides

Vapor pressure measurements have been made with three halides of plutonium by a modification of the Knudsen effusion method. Measurements with solid plutonium trifluoride from 1200°K to 1440°K give the vapor pressure-temperature relation log10pmm=12.468–21,120/T. Measurements with liquid plutonium trifluoride from 1440°K to 1770°K give log10pmm=11.273–19,400/T. Measurements with solid plutonium trichloride from 850°K to 1007°K give log10pmm=12.726–15,910/T; with liquid trichloride from 1007°K to 1250°K give log10pmm=9.509–12,590/T. Measurements with solid plutonium tribromide from 800°K to 929°K give log10pmm=13.386–15,280/T; with liquid tribromide from 929°K to 1100°K give log10pmm=10.321–12,360/T.