Experiments on investigating the thermodynamics properties of palladium hydride after aging as palladium tritide with different storage periods upto 6.5 years have been performed. By analyzing the experimental results, it is found that during the formation and the decomposition of palladium hydride the entropy changes maintain a linear relationship with the helium content in solid, whereas the enthalpy changes keep constant. The sum of interstitial sites in the host palladium matrix is expected to be affected by helium, resulting in the modification on the entropy changes.

The separation factors of the palladium-hydrogen system were experimentally measured at different temperatures ranging from 248 to 303 K after aging for up to 3.5 years by tritium. The results showed a remarkable hydrogen isotope effect in the aged palladium-hydrogen system compared to the raw system. The hydrogen-deuterium separation factor of the palladium-hydrogen system aged by tritium was correlated to temperature and hydrogen/deuterium ratio in the solid phase of palladium hydride. (C) 2017 Elsevier B.V. All rights reserved.

Palladium is an important functional material in tritium treating technology. Tritium decay and its product, helium-3, will decrease the properties of hydrogen storage of palladium. In this paper, the PCT curves of absorbing/desorbing protium and deuterium were measured by a varying temperature method for aged palladium after 1.6 years tritium storage. The experimental results of fresh sponge palladium were provided for comparison; furthermore, thermodynamics of the aged palladium absorbing/desorbing protium and deuterium was analyzed. Comparing with the fresh palladium, tritium aging compels a phase zone to shift right, decreases the plateau pressures of aged Pd-H and Pd-D systems as narrowing down the scope of the plateau pressures. The tritium aging weakens the hysteresis effect of palladium absorbing/desorbing hydrogen and affects the enthalpy and entropy changes of the formation of palladium hydride.

The recombination of hydrogen and oxygen with molar ratio of 2:1 and flow rate of 2 Nm3/h has been investigated in the fluidized bed reactor. It has been observed that the quick mixing of hydrogen and oxygen in Pt/Al2O3 catalyst is free of explosion and allows the effective recombination at the temperature of 373-873K. However, this highly exothermic reaction brings the much high temperature gradient result in the fluidized bed. And the hot spot in reactor is sometimes higher than 1173K, causing the rapid deactivation of the catalyst and lead to the dangerous explosion. As adopting the multistage gas distributor, the concentration of hydrogen in the pristine gas distributor region (always in the bottom of the reactor) is effectively reduced and the temperature in the catalyst dense phase can be controlled to 673-873K, allowing a stable and effective conversion of hydrogen up to 99.9997%. The present work provides a novel fluidization technology for the recombination of hydrogen and oxygen with high concentrations.

Palladium tritides at the initial tritium/palladium (T/Pd) atomic ratio of 0.65 were prepared by gaseous P–V–T method. The 3He release behavior in the aged palladium tritides for 604, 1265 and 2168days with the initial tritium/palladium atomic ratio of 0.65, has been studied by the methods of D–T isotopes exchange and aqua regia dissolution separately. The results of D–T exchange experiment show that the 3He release ratios in these three different time aged palladium tritides are 1.7%, 2.1% and 3.3%, leaving more than 96.7% 3He kept in palladium tritides Lattice. A similar result can also been obtained by aqua regia dissolution method, and the 3He release ratios are 2.0%, 2.9% and 3.3% by comparison. The similarity reveals a strong 3He retain ability of palladium tritides. The experimental data by two methods agree well with each other.

The pressure of tritium gas as a function of time during it was being absorbed either by 5.9-year-aged palladium powder with helium-to-palladium atomic ratio 0.199 or by fresh palladium powder was experimentally measured for initial pressure 350 kPa tritium gas.Mechanism of palladium tritium-absorption and aging effects on palladium tritium absorption rate were analysed.The results indicate that the tritium absorption pressure of fresh palladium decreases rapidly in 5 s and the tritium absorption pressure of 5.9-year-aged Pd of which the atomic ratio to He is 0.199 decreases slowly.The atomic ratio of tritium and palladium of fresh palladium reaches to 0.3 in 5 s,and the atomic ratio of tritium and palladium of aged palladium is just 0.07.The tritium absorption rate of fresh palladium maxes out to 0.11/s in 2 s,and falls down rapidly to 0.02/s in 6 s.The tritium absorption rate of aged palladium reaches to maximum value at 0.02/s in 1 s,and then falls down slowly.The tritium absorption rate of fresh palladium maxes out at α+β-phase,and the tritium absorption rate of aged palladium at α-phase.The 3He that emerges from the decay of tritium blocks the diffusion of tritium and influences the tritium absorption rate.

The application of thermohydrogen processing (THP), the use of hydrogen as temporary alloying element to modify the microstructure and improve the final mechanical properties of several uranium alloys, was studied. It was found that after thermohydrogen processing, a refinement in microstructure with less nonmetallic impurities and more pure phase constituents was achieved. The microstructural refinement resulted in improved ductility, without a large loss of strength. Some possible mechanisms of the effects of THP on the microstructure and the mechanical properties of uranium alloys are proposed.

In this paper, studies have been made concerning the poisoning mechanism. The processes of poisoning of LaNi47Al0.3 alloy are analyzed in detail by means of X-ray photoelectron spectroscopy (XPS), second ion mass spectroscopy (SIMS), Auger-energy spectroscopy (AES) and X-ray diffraction (XRD). The changes of the valence and the concentration distribution of the elements of the alloy LaNi47Al0.3 poisoned by CO are studied. The process and the mechanism of CO's poisoning of alloy LaNi47Al0.3 are proposed as follows: CO is absorbed on the surface of alloy, part of which reacts with La forming LaC2 and La2O3, or reacts with Ni forming NiO and C in the surface layer, the rest of the CO is decomposed into C and O, which diffuse into the bulk to react with La, Ni and Al. These results in phase-split reaction in surface layer of the particle, and enrichment of La and impoverishment Ni on the surface have taken place. The poisoning effect decreases with a increase of depth. The diffusion depth of C is within 600 Angstrom in the surface layer, and that of 0 is within 1000 Angstrom.The oxide film and carbonizing film prevent the H-storage alloys from further absorbing hydrogen, which leads to a deceleration of the H-storage capability. Moreover, The formation of a new phase with poor H-absorption capability is caused by the phase split reactions, which is one of reasons for the decrease of H-absorption property of the H-storage alloys.

Hydrogen absorption–desorption properties of the UZr0.29 alloy and uranium metal were investigated in detail at hydrogen pressures as high as to 0.4 MPa and over the temperature range of 300–723 K. Both UZr0.29 alloy and uranium metal showed similar hydrogen isotopic effect and hysteresis effect. UZr0.29 alloy absorbed hydrogen (deuterium) up to 2.3H (2.18D) atoms per F.U. (formula unit) by only one-step reaction and hence each desorption isotherm had a single plateau over nearly the whole hydrogen composition range. The UZr0.29 alloy showed a little lower dissociation pressure than that of pure uranium; however, it exhibited high durability against powdering upon hydrogenation and may have good heat conductivity. The UZr0.29 hydride has the potentiality to substitute pure uranium hydride as a material for tritium treatment and storage.

Hydrogen absorption-desorption properties of the UZr0.29 alloy and uranium metal were investigated in detail at hydrogen pressures as high as to 0.4 MPa and over the temperature range of 300-873 K. Both UZr0.29 alloy and uranium metal showed similar hydrogen isotopic effect and hysteresis effect. UZr0.29 alloy absorbed hydrogen (deuterium) up to 2.3H (2.18D) atoms per F.U. (formula unit) by only one-step reaction and hence each desorption isotherm had a single plateau over nearly the whole hydrogen composition range. While for those with large amount of zirconium, such as U2Zr and UZr2.3, more stable hydrides than UH3 were formed, which brought some additional plateaus to the desorption isotherms. Uranium-zirconium alloys had a little lower dissociation pressure than that of pure uranium; and the larger the amount of zirconium added to the alloys, the lower the dissociation pressure. However, the uranium-zirconium alloys showed high durability against powdering upon hydrogenation and may have good heat conductivity.

Carbon disulfide is a well-known occupational hazard in the viscose industry, and studies have shown considerable health effects when workers are exposed to high concentrations of this reagent. At exposure levels below the TLV-TWA(31 mg/m(3)), findings remain contradictory, probably due to deficient exposure data. The present study tries to identify the occupational hazards and thoroughly assess the exposure levels in a Chinese viscose rayon plant.Methods: An industrial hygienic field survey and a sampling campaign were carried out, including multi-gas monitoring, on-line measurements, and stationary assessment in the spinning hall as well as personal exposure sampling for spinners (by charcoal tube absorbing and GC-FPD analysis). All data was introduced into Foxpro database, and analyzed by Epi info (6.04) and SPSS,Results: On-line measurement showed that the geometric mean (GM) of carbon disulfide exposure amounted to 12.73 mg/m(3) in 'exposure' and 0.08 mg/m(3) in 'non-exposure' worksites. These concentrations in the air were related to the subject's activities showing the highest levels when they had to open the shield windows of the spinning machines. Stationary exposure measurements of carbon disulfide in the spinning hall amounted to 23.29 mg/m(3) GM (range 5.8-97.94 mg/m(3)). Personal exposure of spinners was about 17.3 mg/m(3) GM. Comparing these methods, the personal exposure sampling could exactly express the exposure levels of the worker's contacting situation. The on-line measurement by multi-gas monitor might also be recommended to the factory as it has its own advantages of rapid and independent assessment, but it under-estimates the exposure level.

This article presents the results of carbon disulfide exposure measurements in a Chinese viscose rayon factory. The objectives of the study were to identify the external exposure levels at a large factory and to investigate the 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the subjects who were exposed to carbon disulfide in the working place atmosphere. The metabolism of carbon disulfide in the exposed subjects was also studied in order to demonstrate the best points in time for the internal exposure sampling. The measurement of the amount of personal exposure to carbon disulfide in the air of the workplace was performed by GC-FPD; the presence of TTCA in the workers urine was analyzed by use of a modified HPLC method. The kinetics of TTCA excretion was studied by analyses at different time-points both during and after exposure to carbon disulfide in the subjects. A total of 155 personal samples were obtained. The carbon disulfide concentration in the staple viscose hall was 13.72 +/- 1.12 mg m-3 in terms of the geometric mean +/- geometric standard deviation, and was 20.05 +/- 1.33 mg m-3 in the filament spinning hall. The TTCA values in the subjects who worked in the staple spinning hall were 1.18 +/- 0.43 mg g-1 creatinine and 1.07 +/- 0.38 mg g-1 creatinine for subjects working in the filament spinning hall. The best time for TTCA sampling is at the end of the working shift, the TTCA excretion was stable for a period of 4-12 h after exposure of the subjects to the carbon disulfide. It might be that the Chinese have different anthropometric characteristics; a sampling bias may therefore appear among different races.

This paper describes a candidate NIOSH EPA method for the determination of carbon disulfide in the air of workplaces with capillary gas chromatography using an orthogonal design. This method is designed to replace the packed column of the NIOSH method with a capillary column. The first part of this work concerned the setup of the method, particularly the choice of chromatographic parameters and finding their main favorable working ranges. The second part, using the statistical method orthogonal design, focused on optimizing the GC conditions, which were: column temperature, T(c) = 90 degrees C; injector temperature, T(i) = 140 degrees C; U section detector temperature, FPDU = 160 degrees C; L section detector temperature, FPDL = 210 degrees C; flow rate of carrier gas, F(c) = 20 cm/s; split ratio = 1/70; and injection volume = 1 microL. The quality control test showed that the coefficient of intra-day variation (CV) was 2.21%. A good logarithm linear correlation between the standard solutions and their peak areas was obtained. In general, the method reported here seems a valid candidate for a NIOSH EPA method due to its high precision and accuracy.