Application of Laser Raman Spectroscopy to Analysis of Isotopie C2 Hydrocarbons in Fusion Fuel Gas Processing

Gaseous C₂ hydrocarbons, which would be the major impurities after methane in plasma exhaust gases, were analyzed by laser Raman spectrometry. Deuterated C₂ hydrocarbons, which were prepared by mixing acetylene, ethylene or ethane with D₂ gas were experimentally measured. Suitable bands for quantitative analyses can be selected as the v₂ vibrations at 1,764~1,973 cm^?1, v₂ vibrations at 1,518~1,627 cm^?1 and some V₃ vibrations at 985~1,344 cm^?1, and V₃ vibrations at 842~994 cm^?1, for deuterated acetylenes, ethylenes and ethanes respectively. Those bands are based on the CC stretching vibrations, except for the deformation vibration V₃ of the ethylenes. Isotopie C₂ hydrocarbons in fusion fuel gas processing will be analyzed by using the same bands in laser Raman spectroscopy.     

Determination of the composition and instability constants of complex Pu+3oxalate ions

The solubility of Pu₂(C₂O₄)₃ · 9H₂O in aqueous solutions of K₂C₂O₄ of various concentrations (0.01–2.4 moles /liter) has been determined at constant ionic strength of the solution at 20. It was found that Pu⁺³ complexes are formed in these solutions. It was found from the results of Pu₂(C₂O₄)₃ · 9H₂O solubility determinations that in the region of K₂C₂O₄ concentrations studied the following complex ions are formed [Pu(C₂O₄)₂]^?, [Pu (C₂O₄)₃]^?3 and [Pu (C₂O₄)₄]^?5, the total instability constants of which are 4.9 · 10^?10; 4.10 · 10^?10 and 11.9 · 10^?11 respectively. The solubility of Pu₂(C₂O₄)₃ · 9H₂O in aqueous (NH₄)₂C₂O₄ solutions has also been determined in the range of ammonium oxalate concentrations from 0.07 to 0.7 mole/liter at 70 °. It is shown that the composition of the complex ions under these conditions corresponds to [Pu(C₂O₄)₂]^?, [Pu(C₂O₄)₃]^?3 and [Pu(C₂O₄)₄]^?5. The calculated total instability constants of these complex ions are 11.6 · 10^?9; 5.6 · 10^?9 and 2.5 · 10^?9 respectively. The heats of formation of complex Pu⁺³ oxalate ions have been calculated for the reaction Pu⁺³ + nC₂O₄ ^?2 ?[Pu(C₂O₄)_n]^3?2n Δ¯Q for the [Pu(C₂O₄)₂]^? ion is 1300 cal., for [Pu(C₂O₄)₃]^?3, 1200 cal., and for [Pu(C₂O₄)₄]^?5, 1300 cal.     

Preliminary Study of Isotopic Methanes Analysis by Laser Raman Spectroscopy for In-Situ Measurement at Fusion Fuel Gas Processing

Application of laser Raman spectroscopy for fusion fuel gas processing was studied by measuring isotopic methanes exchanged with hydrogen isotopes, which are considered to be a major impurities in the processing. For experimental gases, isotopically equilibrated deuterium and methane were prepared in the presence of solid catalyst. Large Raman scattering peaks of v ₁, bands were observed at 2,917 cm^?1 for CH₄ and at 2,100-2,200 cm_?1 for deuterated derivatives of methane C(H,D)₄. Under a spectral resolution of 5 cm_?1, the v ¹ bands of CH₃D and CH₂D₂ were observed as an overlapped peak, the relative absolute Raman intensity ratio of each isotopic methane was obtained as CH₄: CH₃D+CH₂D₂: CHD₃: CD₄=230: 74: 144: 100. On the other hand, the Raman intensity ratio obtained from pure deuterated standard methane was CH₄: CH₃D: CH₂D₂: CHD₃: CD₄=230: 53: 33: 115: 105. It was confirmed that isotopically equilibrated hydrogen isotopes and methane mixed gas would be applicable for an alternative standard gas for fusion fuel processing gas analyzing system.     

Pyrolytic Graphite Irradiated with 4 keV Hydrogen Ions Using Reflection High-Energy Electron Diffraction

Separation of barium isotopes with a selective two-step photoionization process was accomplished using a continuous wave dye laser and ultra-high pressure mercury lamp. Narrow line-width laser light was tuned to the 6s^{2 1}S₀--6s6p ¹P₁ resonance line (553.6 nm), and only a single isotopic component in an atomic beam was excited through the isotope shift. The excited atoms were successively ionized by uv radiation and deflected by a static electric field.

The spectrum of the ion current separated isotopically agreed well with spectroscopic data within the system resolution of 65 MHz. The isotopic enrichment of ¹³⁸Ba was 97%, which corresponded to the selectivity of 1.36. The ionization rate defined as what portion of the incident atoms was ionized was approximately 4x10^?5%. The photoionization cross section was estimated from the experimental results by using the least squares method. The resultant value was (4±1)x10^?23m².     

Investigation of the formation conditions and stability of complex Pu+3 compounds by a spectrophotometric method

The formation of Pu⁺³ complexes with C₂O₄ ^?2, CO₃ ^?2, C₆H₅O₇ ^?3 ions and with Trilon B has been demonstrated by a spectrophotometric method. It was found that their absorption spectra have the most characteristic maxima at the following wave lengths: 565, 605, 665, 780–790, 905–910, 1090 mμ.     

Laser annealing in combination with mass spectroscopy, a technique to study deuterium on tokamak carbon samples, a tool for detritiation

In this study, a method is presented based on mass spectroscopy to measure the areal density of deuterium on a graphite surface exposed to tokamak discharges. The studied sample was cut from a bumper limiter exposed in the TEXTOR tokamak and annealed by a 1 J Excimer laser (KrF). The energy used was 400 mJ cm⁻², which is below the threshold for ablation, 1 J cm⁻². The release of HD and D₂ was measured by a mass spectroscopy set-up and no other species released from the sample were detected in this experiment. The amount of D released from the sample after 20 laser pulses was measured to 7 × 10¹⁶ D atoms per cm⁻² (for this particular sample) and most of the hydrogen at the surface was released in the first pulse, as checked by nuclear reaction analysis (NRA) techniques, which gave changes of the amount of deuterium before and after laser annealing. The sensitivity in this experiment was 5 × 10¹⁴ atoms per cm⁻² for HD and 5 × 10¹³ atoms per cm⁻² for D₂.     

The solid film lubrication by carbon ion implantation into α-Al2O3

Improvement in tribological performance by C⁺110 keV implantation can be achieved by having a more graphite-like carbon structure on Al₂O₃. It was shown that fracture toughness and critical peeling load increased for a fluence of 5 × 10¹⁷C⁺/cm² because of residual compression stress and amorphism of surface. The testing in a different implantation dose indicated that the friction and wear mechanism in Optimol fretting wear machine (SRV) was a combination of surface structure and its abrasive wear. Raman shift shows that the amorphous graphite with 5 × 10¹⁷–1 × 10¹⁸ C⁺/cm² implantation dose was formed on Al₂O₃ surface, so that it reduced friction coefficient and wear of Al₂O₃, also it is noticed that the failure of lubrication due to graphite-like film wear is much earlier in the implantation sample with 1 × 10¹⁷C⁺/cm² dose.     

Calculation of Symmetric Stretching Frequency in Molten BeF2 by Molecular Dynamics Method

The molecular dynamics method was applied to molten BeF₂, in which the pair potentials of the Born-Mayer-Huggins type were employed. The Fourier transform of the distances between a Be²⁺ ion and its nearest neighboring F^? ions averaged over total 12 Be²⁺ ions gave the frequency of about 175 cm^?1 as the symmetric stretching frequency which is in satisfactory agreement with 282 cm^?1 obtained with Raman spectroscopy.

The self-diffusion coefficients of Be²⁺ and F^? ions were estimated to be 2×l0^?10m²/sec and the internal energy was ?2,559 kJ/mol at 973 K.     

Polarographic investigation of complex plutonium oxalates

The composition and stability of complex ions of tri- and tetravalent plutonium in oxalate solutions were investigated polarographically. The complexes Pu(C₂O₄)₄ ^?4 (preponderant amount) and Pu (C₂O₄)₄ ^?5 were formed in solutions of potassium oxalate with pH 3.5–6. Under these conditions, Pu⁺⁴ gave a well expressed reverse reaction wave, suitable for the quantitative polarographic determination of plutonium. The oxidation-reduction potential of this reaction in 1 M potassium oxalate was equal to 0.205 v (relative to a saturated calomel electrode at a temperature of 25 ° C). Two Pu⁺⁴ complexes were simultaneously present in solutions at pH 6–8. From data on the solubility of Pu(C₂O₄)₃, we determined the instability constants of the complex oxalate ions Pu(C₂O₄)₃ ^?3 and Pu(C₂O₄)₄ ^?5, and from the polarographic data those forPu(C₂O₄)₄ ^?4 ions:

$$K_{Pu(C_2 O_4 )_4 ^{ - 3} } = 2.4 \cdot 10^{ - 12} .K_{Pu(C_2 O_4 )_3 ^{ - 3} } = 2.2 \cdot 10^{ - 11} .K_{Pu(C_2 O_4 )_4 ^{ - 4} } = 33 \cdot 10^{ - 23} $$     

Argon ion impact desorption cross sections of chlorine and carbon from molybdenum

Total desorption cross sections have been measured for Cl (σ_Cl) and C(σ_C) on molybdenum by argon ion bombardment for an incidence angle of 60° from the surface normal. For the bombardment an ion gun with low current density (i₀ ~ 1 × 10 ^?7 A cm^?2) at low system pressure (~10^?9 Torr) was used. The detection was performed by AES and the data were sensitivity factor corrected. The AES analysis of the surface after adsorption showed that Mo, C and Cl contributed to more than 94% of the atomic composition. With known i₀, it is possible to obtain σ from the adsorbate signal vs ion bombardment time curve. For ion energies between 0.2 keV to 1.0 keV the measured value for σ_Cl and σ_C are 0.5?3 × 10^?15 cm² and 0.2?4 × 10^?15 cm², respectively. The possible effects of the surface roughness due to prebombardment are discussed.     

Oxidation kinetics of magnesium alloys treated by tantalum ions implantation

AZ31 magnesium alloys were implanted with tantalum ions with doses of 1 × 10¹⁶, 5 × 10¹⁶ and 1 × 10¹⁷ ions/cm², using a metal vapor vacuum arc (MEVVA) at an extraction voltage of 45 kV. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) analysis suggested that tantalum ions implantation promoted the formation of the pre-oxidation layer and a new Ta₂Al phase was formed in the implanted layer. Then, the oxidation kinetics of the implanted specimens was investigated by isothermal oxidation at 773 K in pure O₂ up to 90 min. The results showed that after implantation treatments the oxidation resistance of the specimens was significantly improved and the specimen with the highest dose had the best oxidation resistance. Finally, the mechanism of the anti-oxidation effects was also discussed.     

The influence of the microstructure evolution on the surface morphology in the annealing process of helium-implanted spinel

Single-crystalline spinel (MgAl₂O₄) specimens were implanted with helium ions of 100 keV at three successively increasing fluences of (0.5, 2.0 and 8.0) × 10¹⁶ ions/cm² at room temperature. The specimens were subsequently annealed in vacuum at different temperatures ranging from 500 to 1100 °C. Different techniques, including Fourier transformed infrared spectroscopy (FTIR), thermal desorption spectrometry (TDS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to investigate the specimens. It was found that the absorbance peak in the FTIR due to the stretching vibration of the Al-O bond shifts to smaller wave numbers with increasing fluence, shifting back to larger wave numbers with an increase of annealing temperature. The absorbance peak shift has a linear relationship with the fluence increase in the as-implanted state, while it does not have a linear relationship with the fluence increase after the annealing process. Surface deformation occurred in the specimens implanted with fluences of 2.0 and 8.0 × 10¹⁶ ions/cm² in the annealing process. The phenomena described above can be attributed to differences in defect formation in the specimens.     

Raman spectroscopy characterization of actinide oxides (U1−yPuy)O2: Resistance to oxidation by the laser beam and examination of defects

Structural changes in four (U_1−yPu_y)O₂ materials with very different plutonium concentrations (0 ? y ? 1) and damage levels (up to 110 dpa) were studied by Raman spectroscopy. The novel experimental approach developed for this purpose consisted in using a laser beam as a heat source to assess the reactivity and structural changes of these materials according to the power supplied locally by the laser. The experiments were carried out in air and in water with or without hydrogen peroxide. As expected, the material response to oxidation in air depends on the plutonium content of the test oxide. At the highest power levels U₃O₈ generally forms with UO₂ whereas no significant change in the spectra indicating oxidation is observed for samples with high plutonium content (²³⁹PuO₂). Samples containing 25 wt.% plutonium exhibit intermediate behavior, typified mainly by a higher-intensity 632 cm⁻¹ peak and the disappearance of the 1LO peak at 575 cm⁻¹. This can be attributed to the presence of anion sublattice defects without any formation of higher oxides. The range of materials examined also allowed us to distinguish partly the chemical effects of alpha self-irradiation. The results obtained with water and hydrogen peroxide (a water radiolysis product) on a severely damaged ²³⁸PuO₂ specimen highlight a specific behavior, observed for the first time.     

Analysis of Tritium Behavior in Very High Temperature Gas-Cooled Reactor Coupled with Thermochemical Iodine-Sulfur Process for Hydrogen Production

The tritium concentration in the hydrogen product in Japan's future very high temperature gas-cooled reactor (VHTR) system coupled with a thermochemical water-splitting iodine-sulfur (IS) process (VHTRIS system), named GTHTR300C, was estimated by numerical analysis. The tritium concentration in the hydrogen product significantly depended on undetermined parameters, i.e., the permeabilities of a SO₃ decomposer and a H₂SO₄vaporizer made of SiC. Thus, the estimated tritium concentration in the hydrogen product for the conservative analytical condition ranged from 3.4 × 10^?3 Bq/cm³ at STP (38 Bq/g-H₂) to 0.18 Bq/cm³ at STP (2,000 Bq/g-H₂). By considering the tritium retained by core graphite and the reduction in permeation rate by an oxide film on the heat transfer tube of the IHX and the HI decomposer, the tritium concentration in the hydrogen product decreased to the range from 3.3 × 10^?5 Bq/cm³ at STP (0.36 Bq/g-H₂) to 5.6 × 10^?3 Bq/cm³ at STP (63 Bq/g-H₂), which were smaller than those for the conservative analytical condition by factors of about 3.2 × 10^?2 and 9.6 × 10^?3, respectively. The effectof the helium flow rate in the helium purification system on the tritium concentration in the hydrogen product was also evaluated.     

A magnetically insulated negative ion source for neutral beam heating

A new, magnetically insulated negative ion source has recently been discovered which can produce pulsed negative ion beams (H^?, Li^?, and C^?) with intensities of of 100–300 A/cm² at 1–4 MeV. This source may provide the basis for a high energy neutral beam system for heating large tokamaks.     

Infrared spectroscopic analysis of OH− and OD− in crystalline Li2O as a function of chemical treatment

Infrared spectroscopy has been used to study the chemical form and approximate concentration of OH^? and OD^? in Li₂O single crystals as a function of chemical treatment. Infrared absorption maxima at $\text{(3671±0.5)}\text{cm}{}^{\mathrm{?1}}\text{and}\text{(2711±3.3)}\text{cm}{}^{\mathrm{?1}}$ were observed for OH^? and OD^?, respectively. The absorption coefficient for OD^? was determined to be $\text{4.0±0.4}$ absorbance units per mol part per million OD^? per mm of sample thickness. Vacuum baking of Li₂O crystals reduced the OH^? and OD^? concentrations to <50 mppm; baking in a low moisture-level D₂ environment at 600 to 800°C appeared to lead to volatilization of LiD from the Li₂O crystals; and baking in D₂ containing ($\text{350±50}$) mppm D₂O at 600 to 800°C produced a measurable quantity of LiOD. In all cases, the observed spectra indicated the presence of only one distinguishable form of OH^? or OD^? in the Li₂O lattice. Because of the close correspondence of the observed absorption maxima to reported values for pure LiOH and LiOD, the most consistent (although not conclusive) interpretation is that the OH^? and OD^? are present as a separate LiOH or LiOD phase at room temperature. Only limited conclusions can be drawn regarding the chemical state of OH^? and OD^? during the elevated temperatures exposures. An estimate of the approximate value for the solubility of tritium in Li₂O at 800°C was made using data from D₂/Li₂O isothermal exposure experiments — this value was ? 25 wppm.     

Application of laser-induced breakdown spectroscopy for characterization of material deposits and tritium retention in fusion devices

Laser-induced breakdown spectroscopy (LIBS) is discussed as a possible method to characterize the composition, tritium retention and amount of material deposits on the first wall of fusion devices. The principle of the technique is the ablation of the co-deposited layer by a laser pulse with P (power density) ≥ 0.5 GW/cm² and the spectroscopic analysis of the light emitted by the laser induced plasma. The typical spatial extension of the laser plasma plume is in the order of 1 cm with typical plasma parameters of n_e ≈ 3 × 10²² m^?3 and T_e ≈ 1–2 eV averaged over the plasma lifetime which is below 1 μs. In this study “ITER-Like” mixed deposits with a thickness of about 2 μm and consisting of a mixture of W/Al/C and D on bulk tungsten substrates have been analyzed by LIBS to measure the composition and hydrogen isotopes content at different laser energies, ranging from about 2 J/cm² (0.3 GW/cm²) to about 17 J/cm² (2.4 GW/cm²) for 7 ns laser pulses. It is found that the laser energies above about 7 J/cm² (1 GW/cm²) are needed to achieve the full removal of the deposit layer and identify a clear interface between the deposit and the bulk tungsten substrate by applying 15–20 laser pulses while hydrogen isotopes decrease strongly after the first laser pulse. Under these conditions, the evolution of the spectral line intensities of W/Al/C/hydrogen can be used to evaluate the layer composition.     

应用可调谐外腔半导体激光器测量锂同位素比率

采用中心波长固定的可调谐外腔半导体激光器作为光源,通过激光吸收光谱法对锂原子同位素比率进行测量。该方法利用PID温控器实现锂金属蒸发温度的控制和测量。采用激光斜入射的方式消除光路调试过程中产生的标准具效应。实验测量给出了6组不同腔体温度下⁶Li和⁷Li在671 nm附近的吸收光谱,通过对⁶LiD₁和⁷LiD₂吸收峰进行积分吸收计算,得到⁶Li/⁷Li同位素比率测量精度可达2.5%。     

Development of Deuterium-Tritium Loading Vessel for Laser Fusion Target

Tritium permeation at 350°C through stainless steel wall of a vessel filled with deuterium-tritium gas of 6.1 × 10⁶ Pa pressure was practically suppressed by Au plating of 20μm thick applied to the outside surface. The apparent diffusivity of hydrogen through plated Au layer, derived from the experimental data, was 2 x 10^?11 cm²/s for 470°C, which is 10^?5–10^?6 times smaller than what would be expected from values reported for wrought Au, and the apparent solubility was very significantly higher than similarly expected level. Gas analysis of the Au layer indicated that the effective suppression of tritium permeation is attributable to trapping of hydrogen by C contained in the Au as impurity. Adequate tightness against tritium leakage has been achieved by Au plating on a vessel used for loading glass microspheres with deuterium-tritium gas, intended for laser fusion targets.     

Distribution and Fixation of Cesium and Strontium in Zeolite A and Chabazite

The selective removal and fixation of Cs and Sr have been studied in zeolite A and chabazite. Cesium ion was preferentially distributed into chabazite with a high distribution coefficient (K _Cs>10³ cm³·g^?1) in the presence of NaCl (10^?1 mol·dm^?3). The K _Sr values for zeolite A attained about 10³ cm³·g^?1 in the pH range of 8～10, and they gradually decreased with an decrease in pH.

The initial rate of Cs adsorption was fairly fast in chabazite, and the adsorption ratio reached almost 100% within a few hours. The adsorption ratio of Sr in binderless A zeolite reached almost 100% after 15 h. The adsorption of Cs and Sr on these zeolites was followed by Langmuir-type isotherm. Cesium forms of these zeolites recrystallized to pollucite (CsAlSi₂O₆) above 900°C for zeolite A and above 1,200°C for chabazite. As for Sr forms, these zeolites changed to SrAl₂Si₂O₆ above 900°C.

These recrystallized phases were suitable hosts for the immobilization of Cs and Sr in the nuclear waste solutions.