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.     

Gas Chromatographic Measurements of Hydrogen Isotopes Mixture by Using Catalytic Oxidation Type Detector

A new type of gas chromatograph for quantitative measurements of hydrogen isotopes mixture has been developed through the adoption of catalytic oxidation type detector. Experiments using He as the carrier gas were successfully performed for the separation of D₂-HD and H₂-HD-D₂ mixtures. The minimum detection limits were 0.4–0.9 μl-STP for these components. The linear calibration curves were obtained in the range of 10 μl-STP–20 ml-STP. The sensitivities for H₂, HD and D₂ were 843, 774 and 654 (μl-STP)^?1, respectively. The maximum time needed for the analysis was about 16 min.     

Adsorption Isotherms of Hydrogen Isotopes on Molecular Sieves 5A at Low Temperature

Cryogenic Molecular Sieve Bed (CMSB) is considered to be applied to the bred tritium recovery system or the helium glow discharge exhaust gas cleanup system of nuclear fusion reactor. Molecular Sieves 5A (MS5A) is one of the most possible candidate adsorbents for CMSB. To design the CMSB, adsorption isotherm of hydrogen isotopes for MS5A must be investigated in liquid nitrogen temperature region (around 77 K) and above, and isotherm equation which can express the experimental data obtained in wide pressure range with good accuracy needs to obtaining. The present authors carried out the experiments using the volumetric method to obtain the adsorption isotherm of H₂ and D₂ for MS5A. Adsorption isotherms were obtained in the pressure range between about lPa and 0.2MPa at 77K (liquid nitrogen), 87K (liquid argon), 113K (isopentane), 143 K (n-pentane), 155 K (ethanol) and 195 K (dry ice/ethanol). Two Sites Langmuir Model was applied to understand adsorption isotherms, and was able to express the experimental observation with fairly good accuracy. The apparent heats of adsorption for two kinds of activated adsorption sites were obtained from temperature dependence of adsorption isotherms. Furthermore, parameters of adsorption isotherms for residual 4 hydrogen isotopes (HD, HT, DT and T2) were estimated using reduced mass.     

Hydrogen Concentration Dependence of Tritium Tracer Diffusion Coefficient in Alpha Phase of Niobium

In order to examine influences of coexistent hydrogen isotopes on diffusion behavior of tritium in niobium, tracer diffusion coefficients D_t of tritium in alpha phase of hydrogenated and deuterized niobium (α-NbH_xT_y and α-NbD_xT_y (x<0,8,y<<x)) have been measured at 473 K, 493 K and 553 K. The data on D_t show typical hydrogen concentration dependence: D_t of tritium for both α-NbH_xT_y, and α-NbD_xT_y, decreases with hydrogen concentration under all experimental conditions. The obtained concentration dependence of D_t of tritium differs from that of D_t of protium in α-NbH_x or of deuterium in α-NbH_xT_y. On the other hand, no appreciable differences in the concentration dependence of D_t of tritium between α-NbH_xT_y, and α-NbD_xT_y, are observed: there are no definite isotope effects due to the coexisting hydrogen isotopes. This result suggests that D_t of tritium for a tritiated niobium (α-NbT_x) is not very different from that for α-NbH_xT_y and α-NbD_xT_y. The chemical diffusion coefficient D* of tritium is also evaluated on the basis of the obtained D_t of tritium and of a literature value of a thermodynamic factor F for Nb-H and Nb-D systems.     

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.     

Significance of Covariance Matrices in Nuclear Data Evaluation

Tritium decontamination using ultra violet (UV) lamp and laser was performed. Simulated co-deposited layer on tungsten substrate was deposited by C₂H₂ or C₂D₂ glow discharge. The co-deposited layer was irradiated to UV lights from a xenon excimer lamp (172 nm) or ArF excimer laser (193 nm) and the in-situ decontamination behavior was evaluated by a mass spectrometer. After the UV irradiation, the hydrogen concentration in the co-deposited layer was evaluated by elastic recoil detection analysis (ERDA) and the depth profile was analyzed by secondary ion mass spectrometry (SIMS).

For the co-deposited layer formed by C₂D₂ glow discharge, it was found that M/e 3 (HD) gas was released mainly during the UV lamp irradiation while both M/e 3 (HD) and M/e 4 (D₂) gases were detected during the UV laser irradiation. Though the co-deposited layer was not removed by UV lamp irradiation, almost all the co-deposited layer was removed by UV laser irradiation within 1 min. The ratio of hydrogen against carbon in the co-deposited layer was estimated to be 0.53 by ERDA and the number of photon needed for removing 1 fim thick co-deposited layer was calculated to be 3.7×10¹⁸ cm^-2 for the UV laser by SIMS measurement. It is concluded that C-H (C-D) bond on the co-deposited layer were dissociated by irradiation of UV lamp while the co-deposited layer itself was removed by the UV laser irradiation.     

Simulation Procedure for Multistage Water/Hydrogen Exchange Column for Heavy Water Enrichment Accounting for Catalytic and Scrubbing Efficiencies

The present paper gives a simulation procedure for multistage water/hydrogen exchange columns for heavy water enrichment using hydrophobic catalysts. The Murphree-type efficiencies for H₂O, HDO and D₂O are used as the scrubbing efficiencies for sieve trays. The reaction rate of H₂+D₂?HD is assumed to be very rapid and equilibrated at the outlet of the catalyst bed. The catalytic efficiencies defined for H₂O(g) and D₂O(g) are considered for the nonequilibrated exchange reactions: H₂+HDO(g)?HD+H₂O(g) and H₂+D₂O(g)?D₂+H₂O(g). Those efficiencies are treated as input variables for the simulation. The main calculational loop is based on the Newton-Raphson iteration, but the order of the Jacobian matrix is just equal to the number of sieve trays for vapor/hydrogen scrubbing. The procedure is applicable to solution of operating problems in a wide range of input and output specifications.     

Hydrogen Isotope Separation by Plasma-Chemical Method

Deuterium transfer (exchange) reaction as shown in HDO+H₂=H₂O+HD was studied as a case similar to the tritium transfer reaction as shown in DTO+D₂=D₂O+DT, the first step in tritium isotope separation of the tritiated heavy water DTO. The transfer reaction was plasma-chemically catalyzed by allowing a gas mixture such as H₂O/D₂, D₂O/H₂, H₂O/HDO/H₂ or H₂O/D₂O/HDO/H₂ to flow through an atmospheric pressure discharge zone formed in a reaction chamber, the inner temperature of which was maintained just above 100°C. The plasma-chemical reactions diagnosed by infrared and emission spectroscopy revealed that the mixture underwent instantaneous deuterium transfer reactions as it passed the zone. The effectiveness of the method was demonstrated by high deuterium transfer rate, high separation factor of the transfer and a possibility of miniaturizing the separation facility.     

Surface mediated isotope exchange reactions between water and gaseous deuterium

Maintaining isotopic purity of hydrogen is one of the major tasks in tritium processing systems. The work with multiple isotopes and isotopomers is accompanied by isotope exchanges which is often accelerated by catalysts e.g. surfaces of various materials. In this work, densities of D₂O, HDO produced via isotope exchange reactions in the mixture of D₂, H₂, D₂O, H₂O, HD and HDO contained in a stainless steel (type SS304) vessel were measured as a function of time (40-36 000 s) and pressures near 3.5 × 10² Pa, using mass spectrometry. The derived rates of change of the isotopomers densities are described accurately by a postulated kinetic model.     

Molecular-sieving effect of zeolite 3A on adsorption of H2, HD and D2

Synthetic zeolite 3A has the molecular-sieving windows of nominal diameter 0.3 nm in its crystal lattice framework, which obstruct the crystalline adsorption of molecules of diameter larger than 0.3 nm, except water, hydrogen and helium. The window's diameter slightly varies with temperature, however, that is endorsed in experimental results that hydrogen cannot be adsorbed at the liquid-nitrogen temperature. Authors measured the range of temperature where zeolite 3A permits hydrogen adsorption, and revealed the temperature difference of several degrees in appearance of molecular sieving for H₂ and D₂. This difference is important because from a H₂–D₂ mixture one isotope could be isolated by adsorption if operated at a temperature regulated between the molecular-sieving appearance temperatures. We have reported large values of D₂/H₂ separation factor obtained from molecular-sieving experiments. In this study, the effect of sieving for the hybrid-atomic isotope HD is examined using a H₂–HD–D₂ mixture. We here report the experimental HD/H₂ separation factor evaluated between the D₂/H₂ factor and unity. This result is significant because where the effective molecular diameter concerning the sieving mechanism is suggested. From this knowledge, the isotopic effect of sieving for HT and DT can be predicted.     

Enrichment of Low Level Tritium from Hydrogen Using Potassium-Graphite Intercalation Compound (KC24)

A sorption-desorption process using potassium-graphite intercalation compound (K-GIC) was studied to verify its applicability to hydrogen isotope separation. Lowly concentrated tritium (7.55 MBq/mol-H₂) contained in about 1 l of H₂ gas was successfully enriched using 1 g of KC₂₄. Three cycles of the sorption-desorption process applied to the H₂)-HT gas mixture proved to enhance the tritium concentration by a factor of 3.9, with a concomitant reduction of volume to 1/14. The positive result obtained in this study promises for this type of sorption-desorption process using K-GIC very good prospects of useful application to hydrogen isotope separation. The experimental process was simulated by calculation based on the material balance of the two components, using data of equilibrium in single stage. The calculated values agreed very well with experimentally determined data, thus attesting the applicability of the above simulation procedure to designing K-GIC hydrogen isotopes separators.     

Numerical model for separation of H-D gas mixture in batch-type concentric-tube thermal diffusion columns

The modeling simulation for the separation of H-D gas mixture in batch-type concentric-tube thermal diffusion columns have been analyzed from the transport equation coupled with the application of mass balance. The most important assumption is that the concentrations of H₂, HD and D₂ are locally equilibrium at every points in the column as H₂ + D₂ ↔ 2HD. The concentration distribution equation was derived and the concentration difference between the bottom and top ends of the column could be estimated. The degree of separation and separation factor for recovery of deuterium from H-D gas mixture in the batch-type cryogenic-wall thermal diffusion column were estimated.     

氘气中氢同位素的低温气相色谱法测定

针对高纯氘气中H₂、HD与D₂等氢同位素气体间不易分离分析的特点,以5A分子筛微填充石英毛细管色谱柱,在－95℃下对氢同位素进行分离,以气相色谱-脉冲放电氦离子化检测器对氢同位素进行分析。研究建立的H₂、HD与D₂等同位素气体测定方法精密度小于15%,最小检出摩尔分数为1×10^－6。     

Overall Conductivity and Electromotive Force of SrZr0:9Yb0:1O3–a Cell System Supplied with Moist CH4

A proton-conducting ceramic cell for recovering tritium from process streams was investigated for its application to a fusion reactor system. The ceramic cell tested here was composed of a SrZr_0:9Yb_0.1O_3–a tube, one end of which was closed, and Ni/SiO₂ and NiO/SiO₂ porous electrodes. Its anode was supplied with moist CH₄ or H₂ and its cathode with moist O₂. All of the j-V curves obtained by a direct-current method were correlated to the relation V = E ₀ ? jd/σ at 600–700°C regardless of the two different conditions of the CH₄ + H₂O and H₂ + H₂O supply. The rate-controlling step of charged hydrogen ion transfer was determined from the dependences of the overall conductivity σ and the electromotive force E ₀ on the anode H₂O partial pressure and temperature. The E ₀ value under the condition of the CH₄ + H₂O supply was affected by the diffusion of reaction products of CH₄ + H₂O = CO + 3H₂ through the porous anode. On the other hand, the σ value was limited by the oxygen reduction rate at the cathode interface between the ceramic and the Ni electrode regardless of the different conditions between CH₄ + H₂O and H₂ + H₂O. These results were consistent with our results obtained by an alternating-current method. The activation energy of the overall conductivity was 60 kJ/mol.     

氢/氘气在改性分子筛上的吸附性能研究

在液氮温度下采用容积法研究了5A、ZSM-5及其改性沸石分子筛对氢同位素的吸附分离性能,探讨了过渡金属盐负载和球磨等改性方法对氢同位素气体吸附的影响。结果发现,改性后分子筛上气体的吸附量普遍降低,但某些改性有利于H₂和D₂的分离。     

Luminescence from low-energy impact of and ions (n = 1,2,3) on a Tore Supra carbon tile

The hydrogen Balmer series was observed when beams of H⁺, , and D⁺, , ions impinged at 100–1000 eV on a carbon fiber composite tile (Tore Supra). The excitation functions of the H_β (D_β) lines demonstrate the validity of the independent particle model. The logarithmic plot of the H_β (D_β) line intensity versus the reciprocal projectile ion velocity can be well reproduced by a model in which the hydrogen ion projectiles are neutralized in the entrance phase and subsequently electronically excited in collisions with carbon atoms. Finally, the excited hydrogen atoms leave the solid and emit the observed photons, unless they are quenched in non-radiative processes.     

Hydrogen and Deuterium Transport through Type 304 Stainless Steel at Elevated Temperatures

The permeation time-lag method have been used to determine the permeabilities, diffusion coefficients and solubilities of hydrogen and deuterium in type 304 stainless steel of three kinds of surface treated specimens; with oxide film, reduced by H₂ gas and Pd coated. For the specimen with a thin oxide film the permeability increased abruptly at the temperature higher than 1,050 K owing to reduction of the oxide film by H₂ gas introduced. The permeability and diffusion coefficient for hydrogen-reduced specimens agreed with those for Pd-coated specimens showing the data of bulk diffusion limited. The isotope effects for permeability Φ_H/Φ_D, diffusion coefficient D _H/D _D and solubility were about 1.4, 1.2 and 1.1, respectively. From these values θ(=hν/k)=1,530±50K and θ′(=hν/k)=2,740±20K were obtained by the quantum effect of a harmonic approximation.     

Room-Temperature Reactor Packed with Hydrophobic Catalysts for the Oxidation of Hydrogen Isotopes Released in a Nuclear Facility

A room-temperature reactor packed with hydrophobic catalysts for the oxidation of hydrogen isotopes released in a nuclear facility will contribute to nuclear safety. The inorganic-based hydrophobic Pt catalyst named H1P has been developed especially for efficient oxidation over a wide concentration range of hydrogen isotopes at room temperature, even in the presence of saturated water vapor. The overall reaction rate constant for hydrogen oxidation with the H1P catalyst in a flow-through system using a tritium tracer was determined as a function of space velocity, hydrogen concentration in carriers, temperature of the catalyst, and water vapor concentration in carriers. The overall reaction rate constant for the H1P catalyst in the range near room temperature was considerably larger than that for the traditionally applied Pt/Al₂O₃ catalyst. Moreover, the decrease in reaction rate for H1P in the presence of saturated water vapor was slight compared with the reaction rate in the absence of water vapor due to the excellent hydrophobic performance of H1P. Oxidation reaction on the catalyst surface is the rate-controlling step in the range near room temperature and the rate-controlling step is shifted to diffusion in a catalyst substratum above 313K due to its fine porosity. The overall reaction rate constant in the range near room temperature was dependent on the space velocity and hydrogen concentration in carriers. The overall reaction rate constants in the range of 1;000=T greater than 3.2 correlated to k _overall[s^?1] = 5.59 × 10⁷ × SV[h^?1] × exp (?67.7 [kJ/mol]/R_gT), where the space velocity range was from 600 to 7,200 h^?1.     

Effect of Absorbed Hydrogen on the Stress Corrosion Cracking (SCC) Susceptibility of Unirradiated Zircaloy Cladding

Effect of absorbed hydrogen on the stress corrosion cracking (SCC) susceptibility of unirradiated Zircaloy cladding was examined. The data obtained from literatures showed that the normalized ratios of SCC threshold stress (σ_th ) to 0.2% yield stress (σ_0.2.) claddings, from which the influence of σ_0.2 had been eliminated, increased with increasing hydrogen contents below 50ppm in unirradiated Zircaloy-2 and -4. For Zircaloy-4, the break point was observed in the relationship between normalized ratios of σ_th to σ_0.2 and hydrogen content in sample at hydrogen content of approximately 50ppm. Thermodynamic calculations were carried out for the reaction between iodine gas and zirconium containing hydrogen. The results suggested that the reactions hardly occurred at increased hydrogen content and zirconium reacted with iodine gas only below 100 ppm of hydrogen. Since these tendencies correspond to those of the normalized ratios of σ _th to σ_0.2 on the hydrogen content, it is considered that hydrogen affects the reactions between iodine gas and zirconium and reduces the SCC susceptibility of Zircaloy cladding.     

Spectroscopic quantitative analysis of the isotopic composition of gas mixtures containing hydrogen, deuterium, and tritium

A detailed experiment is carried through to construct a calibrating curve in the concentration interval from 0.7 to 97% H₂ in D₂. The results obtained are in good agreement with theory. It is shown that it is possible to perform an isotopic analysis of tritium in mixtures with hydrogen and deuterium. An investigation is performed of the relative intensity of the isotope lines as a function of the pressure in a discharge tube.