钯在氢同位素分离和纯化工艺中的应用

在迄今所知的金属-氢体系中，钯氢体系的同位素效应最强，因此，钯被广泛用于氢同位素处理工艺中。文章简述了钯氢体系的同位素效应，综述了钯及其合金在氢同位素分离和纯化工艺中的主要应用及其发展。     

An investigation of energy balances in palladium cathode electrolysis experiments

A series of experiments was performed at the Idaho National Engineering Laboratory (INEL) to investigate mechanisms that may contribute to energy flows in electrolysis cells like those of Fleischmann and Pons. Ordinary water (H₂O), heavy water (D₂O), and a mixture of the two were used in the INEL experiments. Cathodes used include a 51-m Pd foil and 1-mm diameter extruded wire Pd rods in straight and coiled configurations. Energy balances in these experiments revealed no significant net gain or net loss of energy. Cell overpotential curves were fit well with a Tafel equation, with parameters dependent on electrode configuration, electrolyte composition, and temperature. Water evaporation and interactions of hydrogen isotopes with the Pd cathode were evaluated and found not to be significant to energy balances. No ionizing radiation, tritium production, or other evidence of fusion reactions was observed in the INEL experiments.Work supported by U.S. Department of Energy, Director of Energy Research, under DOE Contract no. DE-AC07-76ID01570.     

More searches for cold fusion

Following the announcement of cold nuclear fusion being observed in electrochemical cells by Fleischmann and Pons¹ and by Jones,² we have searched for the characteristic radiations of thed+d andp+d fusion reactions in cells similar to those described in Refs. 1 and 2. No fusion product neutrons or gamma rays have been observed from either palladium or titanium cathodes. From measured D/Pd ratios in the systems with the palladium cathodes, we set upper limits on the fusion rates for our systems.     

Nuclear and thermal effects during electrolytic reduction of deuterium at palladium cathode

In a galvanostatic experiment of charging deuterium in a palladium cathode, nuclear and thermal effects were found. A sintered palladium electrode shaped as parallelepiped was used. After 6 days of electolysis at 200 mA/cm², a simultaneous emission of neutrons, tritium excess in the electrolytic solution, and temperature rapid increase was observed. During the event which lasted 4 minutes, we counted 7.2×10⁵ neutrons while the electrode temperature reached 150°C. Electrochemical procedure for charging the palladium electrode by deuterium using galvanostatic pulses as well as the associated electrode temperature trends are shown.     

Experimental study on cold fusion using deuterium gas and deuterium ion beam with palladium

A series of experiments using deuterium gas and low energy deuteron beam with palladium has been designed at Mississippi State University to allow for the observation, if it exists, of cold fusion. Three experiments were performed. One involved the diffusion transient of deuterium gas into palladium. The gas was cooled by liquid nitrogen, and its temperature was permitted to rise to room temperature, changing from near –34°C to 19°C in 75 minutes. A spherical lithium neutron detector, 21 cm from the palladium, gave an audible indication of neutron levels approximately twice the background. A second experiment used a deuterium ion beam (1 kev) which bombarded a palladium target. An average counting rate of 36±6 counts for 2 minutes was measured by a BF₃ tube with a paraffin moderator, 50 cm from the target. The background varied from 1–7 counts for each 2 minutes of counting period and averaged 4±2 counts in 2 minutes. A nitrogen ion beam impinging on the same palladium target produced 6 counts for a 2-minute counting period. A third experiment used a hydrogen ion beam first, then a nitrogen ion beam, finally a deuterium ion beam to bombard the same palladium target. These ion beams had energy less than 1 kev, and created neutron counts in the range of background. The palladium specimens were a piece of foil and a tube which used to be the palladium leak in a neutron generator. These preliminary experiments will be repeated, improved, and extended later.     

In situ ERDA measurements of hydrogen isotope concentrations in palladium at atmospheric pressure

In situ elastic recoil detection analysis (ERDA) measurements in gases at atmospheric pressure have been carried out using 15 MeV ⁴He ion beams. The beams are extracted through a molybdenum foil having a thickness of 5 μm. The maximum depth of analysis is about 4 μm for the palladium hydride and palladium deuteride (PdH_x and PdD_x, x = 0.7-0.8) samples. The temperature of the samples rises stepwise from room temperature to 180 °C. ERDA spectra are obtained every 2 min. Hydrogen and deuterium in the samples are discharged in the temperature range of 120-140 °C in a vacuum. Decrease in the hydrogen concentration in the PdH_x sample heated in a vacuum follows a first order in the value of x and an apparent activation energy of discharge of hydrogen is 1.05 eV. On the other hand, the hydrogen and deuterium concentrations decrease at about 80 °C in air. No isotope effects are observed in both a vacuum and air. The temperature at which the hydrogen concentration decreases in helium gas is almost the same as that in a vacuum. It indicates that hydrogen and deuterium atoms are discharged by chemical reactions with air and that there are no effects of cooling of the thermocouple by convection of air.     

Neutron emission and the tritium content associated with deuterium-loaded palladium and titanium metals

An experimental investigation has been conducted on samples of palladium and titanium metals which have been loaded with deuterium through the electrolysis of D₂O and by absorption of D₂ gas. In approximately 200 experiments on 25 cells, statistically significant evidence for neutron emission was obtained in three separate experiments from one palladium cathode. Observed rates are 3–4 times the background rate and correspond to source strengths up to 50 neutrons/min. The pulse height response of the NE213 liquid scintillator-based detectors corresponds to that expected for 2.45 MeV neutrons. Tritium has been identified in nine Pd−Ni electrolytic cells, at levels corresponding 10¹²–10¹⁶ atoms. Activity buildup curves indicate that the apparent production occurs over a time period as short as a few hours. This work supported by the Office of High Energy and Nuclear Physics of the U.S. Department of Energy under Grants DE-FG05-86ER40256 and DE-FG05-88ER40437     

Cross section measurements of the Li(d,α0)He reaction

Differential cross-section measurements of the ⁶Li(d,α₀)⁴He reaction have been performed for deuteron energy between 900 and 2000 keV in steps of 25 keV. The reaction α particles were detected at four backward angles from 140° to 170° in steps of 10°. A qualitative discussion of the observed variations in the reaction cross sections through the influence of resonances in the d + ⁶Li compound system is presented. The results are also compared to existing data, when present, and are validated through benchmarking experiments using high-purity, thick, mirror-polished natural LiF and LiAlO₂ targets.     

Cyclotron production of the Ag, Pd, Rh radionuclides by Pd(p,x) nuclear processes

Production cross-sections of the ^105g+m,106mAg, ^100,101Pd, and ^{100g+m,101m,105g+m}Rh radionuclides through proton-induced reactions on natural palladium were measured up to 40 MeV by using a stacked-foil activation technique combined with high-resolution γ-ray spectrometry. The production cross-sections of ¹⁰¹Pd and ^{100g+m,105g+m}Rh radionuclides have been reported here for the first time from the ^natPd(p,x) nuclear processes. The present results are compared with the available literature values as well as the theoretical data calculated by the TALYS and the ALICE-IPPE computer codes. A quantitative comparison of the present results with the theoretical data has also been done with several deviation factor definitions. Optimal production pathways of the therapeutic ^105gRh radionuclide with minimal contamination using cyclotrons are discussed elaborately.     

Contribution of thermal neutrons to radiation hardening of pure copper

The paper presents the results of an experiment the aim of which was to estimate directly the effect of the thermal neutron fluence on pure copper hardening. Identical specimens were irradiated in two reactors (SM-2 and RBT-6) in the dose range 10⁻³-10⁻¹ dpa at T_irr=80 °C under substantially different, by a factor of 5, thermal neutron fluences, with other irradiation parameters being close. The results show that the elevated thermal fluence in the SM-2 reactor increases the radiation hardening of pure copper by 50% at a dose of about 10⁻³ dpa as compared with specimens irradiated in the RBT-6 reactor. The contribution of thermal neutrons proved to be much more considerable than the theoretical estimates.     

Formvar characterization by use of forward elastic scattering

The validity of the concentrations of carbon and oxygen reported in formvar previously and the underlying assumption that these elements are uniformly distributed in our formvar films have been checked. New elastically scattered 13 MeV ⁶Li+¹²C and 13 MeV ⁶Li+¹⁶O cross-sections have been measured at 17.5°, 25° and 28°. By use of these cross-sections, carbon and oxygen concentrations, a factor of 10 higher than previously reported values, have been determined for the first time in our formvar backings with a dispersion per backing not greater than 7%.     

Lithium isotope effects upon electrochemical lithium insertion to host material from ionic liquid medium

Lithium was electrochemically inserted from a Li⁺ ion containing ionic liquid into graphite or tin to observe lithium isotope effects that accompanied the insertion. While no preferential uptake of the lithium isotopes was detected with graphite, the lighter isotope, ⁶Li, was preferentially fractionated into tin with the single-stage lithium isotope separation factors, S, ranging from 1.004 to 1.008 at 25 °C. It was speculated that a Li⁺ ion was inserted into graphite together with an anionic component of the ionic liquid and, upon the reduction of the Li⁺ ion to a lithium atom, the anion was released from graphite, while a Li⁺ ion alone was inserted into tin. Molecular orbital calculations supported this speculation in a qualitative fashion.     

Solidification of radioactive wastes by fusion in basalt

It is shown that fused bagalt is suitable for immobilizing radioactive wastes having high specific activity. It has been found that recrystallization of the vitreous fused basalt phase improves the properties of the material, principally the mechanical strength and the chemical stability. The calculated diffusion coefficients vary from 10^–15 to 10^–17 cm²/sec at temperatures of 30–70°C.Institute of Nuclear Studies, Czechoslovakian Academy of Sciences, Rzhezh near Prague, Czechoslovakia. Translated from Atomnaya Énergiya, Vol. 21, No. 4, pp. 285–289, October, 1966. The scientific research work on this subject is being done under an agreement with the International Atomic Energy Agency.     

Changes in hardness and elasticity of a Ti6Al4V alloy under helium irradiation

Ti₆Al₄V specimens have been irradiated at different temperatures with 200 keV He ions. Microhardness and elastic modulus of the unirradiated and irradiated specimens were measured by means of the nano-indentation technique and analyzed using the Oliver-Pharr method. The indentation depth of all samples is 700 nm, which is comparable in magnitude to the ion range. The subsurface structure of the Ti₆Al₄V specimens was investigated by the X-ray diffraction technique. The measurements indicate that the microhardness increased with the irradiation temperature from room temperature to 600 °C while the elastic modulus almost monotonically decreased. The Irradiation at 700 °C, however, caused softening and slight increase of the elastic modulus within the surface layer of the specimens. The hardening and reduction of the elastic modulus of the Ti₆Al₄V alloy under irradiation conditions used in this study is tentatively explained by a model based on the presence of point defects and dispersed obstacles of β-precipitates. The softening and slight increase of elastic modulus of helium-irradiated Ti₆Al₄V at 700 °C might be related to the coarsening of β-precipitates and formation of the hybrid γ-TiH phase in α-phase.     

In search of nuclear fusion in electrolytic cells and in metal/gas systems

It has been reported recently in the literature that unexpected thermal and nuclear effects (production of excess heat, neutrons, γ-rays, and tritium) can occur during the electrolysis of heavy water at palladium or titanium electrodes, or during temperature and pressure cycling of the titanium/deuterium gas system. We have attempted to reproduce some of these experiments. A variety of electrochemical cells having palladium cathodes in the form of wires, tubes, sheets, and rods have been used to electrolyze heavy water containing 0.1 mol.dm⁻³ LiOH, 0.1 mol.dn⁻³ LiOD or 0.5 mol.dm⁻³ D₃PO₄. Current densities of up to 200 mA.cm⁻² were applied. The mass of the palladium cathodes covered the range from 1–40 grams and the surface area varied from 8–140 cm². Neutron detection systems with low constant backgrounds were used to search for neutron emission during electrolysis. These included³He- and¹⁰BF₃-based detectors. After running some of the cells for more than 30 days, no neutron emission above background could be detected. This puts upper limits of 0.5 s⁻¹ and 2×10⁻²³ fus. D-D.s⁻¹ on the neutron emission and the fusion rate, respectively. A sensitive and accurate heat-flow calorimeter was built and used to monitor the energy balance of some of the cells during electrolysis. No unexpected heat effects were observed. This puts an upper limit of 0.13 W.cm⁻³ on the specific excess power. No enrichment of the electrolyte in tritium was evident after electrolysis. Experiments were also performed with the titanium/ deuterium gas system. These consisted of exposing titanium metal to a deuterium gas pressure of 40 atmospheres, lowering the temperature to −196°C, releasing the pressure and gradually warming the titanium to room temperature. No neutron emission above background was observed during these experiments, which puts upper limits of 0.5 s⁻¹ and 4×10⁻²⁵ fus.D-D.s⁻¹ on the neutron emission and fusion rate, respectively. Submitted toJournal of Fusion Energy as part of the Proceedings of the Workshop on Cold Fusion Phenomena held in Santa Fe in May 1989.     

Tensile fracture characteristics of nanostructured ferritic alloy 14YWT

High temperature tensile fracture behavior has been characterized for the nanostructured ferritic alloy 14YWT (SM10 heat). Uniaxial tensile tests were performed at temperatures ranging from room temperature to 1000 °C in vacuum at a nominal strain rate of 10⁻³ s⁻¹. Comparing with the existing oxide dispersion strengthened (ODS) steels such as Eurofer 97 and PM2000, the nanostructured alloy showed much higher yield and tensile strength, but with lower elongation. Microstructural characterization for the tested specimens was focused on the details of fracture morphology and mechanism to provide a feedback for process improvement. Below 600 °C, the fracture surfaces exhibited a quasi-brittle behavior presented by a mixture of dimples and cleavage facets. At or above 600 °C, however, the fracture surfaces were fully covered with fine dimples. Above 700 °C dimple formation occurred by sliding and decohesion of grain boundaries. It was notable that numerous microcracks were observed on the side surface of broken specimens. Formation of these microcracks is believed to be the main origin of the poor ductility of 14YWT alloy. It is suggested that a grain boundary strengthening measure is essential to improve the fracture property of the alloy.     

Determination of Tritium Concentration in Fuel Reprocessing Liquid Waste by Vacuum Freeze Distillation

Abstract

The vacuum freeze distillation method was successfully applied to the preparation of radiochemically pure water samples used for determining the tritium concentration in highly radioactive liquid waste produced in nuclear fuel reprocessing.

This method yielded a decontamination factor exceeding 10⁵ for radioruthenium and other long-lived fission products. The isotope effect on the tritium concentration was corrected by applying an enrichment factor determined from experiment.

A small portion of the high level liquid waste solution was taken from the Reprocessing Plant of the Japan Atomic Energy Research Institute, neutralized with 2 N sodium hydroxide, and subjected to the vacuum freeze distillation. The distillate was subsequently analyzed for tritium by liquid scintillation counting. The tritium concentration in the waste solution was found to be approximately 0.13 μCi/ml, which corresponded to about 70% of the total tritium contained in the original spent fuel rods.     

Measurement and analysis of neutron and gamma-ray emission rates,other fusion products,and power in electrochemical cells having Pd cathodes

Results of experiments intended to reproduce cold fusion phenomena originally reported by Fleischmann, Pons, and Hawkins are presented. These experiments were performed on a pair of matched electrochemical cells containing 0.1×9 cm Pd rods that were operated for 10 days. The cells were analyzed by the following means: (1) constant temperature calorimetry, (2) neutron counting and γ-ray spectroscopy, (3) mass spectral analysis of⁴He in effluent gases, and⁴He and³He within the Pd metal, (4) tritium analysis of the electrolyte solution, and (5) x-ray photoelectron spectroscopy of the Pd cathode surface. Within estimated levels of accuracy, no excess power output or any other evidence of fusion products was detected.     

Differential cross-section measurements for the C(d, p0)C reaction and applications to surface analysis of materials

This work involves surface analysis by nuclear techniques, which are non-destructive, and computer simulation. The “energy analysis” method for nuclear reaction analysis is used. Energy spectra are computer simulated and compared to experimental data, giving target composition and concentration profile information. Measured values are presented for the differential cross-section of the ¹²C(d, p₀)¹³C reaction in the deuteron energy range 0.81-2.07 MeV for laboratory detection angles of 165° and 135°, using self-supported two-layered targets consisting of high purity thin films of typically 13 μg/cm² natural carbon and 65 μg/cm² gold. The error in the absolute differential cross-section values is generally ∼6%. The method, using these values, is successfully applied to determination of uniform concentration profiles of ¹²C, along considerable depths, for a thick flat target of high purity pyrolitic graphite. It is characterised a thin surface film of carbon on a thick flat quartz target. Uniform concentration profiles of ¹⁶O are also obtained from (d, p) and (d, α) reactions.     

Void-swelling in 20% cold-worked FV548 austenitic stainless steel irradiated with 22 MeV C2+ ions or 46.5 MeV Ni6+ ions

A study has been made of the void-swelling behaviour of 20% cold-worked FV548 steel irradiated with 22 MeV C²⁺ or 46.5 MeV Ni⁶⁺ ions in the Harwell Variable Energy Cyclotron after room-temperature pre-injection with 10 ppm helium. The dose dependence of void-swelling under 46.5 MeV Ni⁶⁺ irradiation at 500 and 600°C, and the temperature dependence of void-swelling of specimens irradiated with 22 MeV C²⁺ ions in the range 500–650°C have been established. In addition the temperature dependence of void-swelling in specimens aged for 1000 h at 650° C before irradiation has also been studied. Subsidiary annealing experiments have demonstrated the high recovery resistance of the 20% cold-worked structure in FV548, compared with types 316 and 321 steels.The void-swelling behaviour is interpreted in terms of the balance between the dislocation and NbC point defect sink strengths and the observed resistance to recovery of the cold-worked structure in FV548.