Water Bubbler Research Articles

Detritiation of the Organic Material in the MSO Process

Tritium is a radioactive isotope of hydrogen, and due to its limited supply and related high price, it is necessary to recover it from tritiated materials via detritiation technologies. The number of tritiated materials arises during fusion. Tritium from fusion reactors is deposited in the outer layer of plasma-facing materials, which must be dealt with during maintenance or decommissioning processes. A second source of waste is laboratory equipment that could be contaminated with tritium. High-temperature treatment in an oxidation environment can achieve the release of tritium from metals or organic materials. The tritiated vapor is then captured in a series of water bubblers and reprocessed into pure T2. One of the high-temperature methods is molten salt oxidation (MSO), which uses high temperatures, alkaline salt, and an oxidative environment for flameless oxidation of different types of waste. This work aimed to simulate the detritiation processes of tritiated organic materials in MSO technology. First, a series of experiments with D2O absorbed in ion resins was conducted. The organic waste was decomposed within the molten salt, and the flue gas was measured to determine the oxidation efficiency. The D2O was captured in a series of water bubblers, and the water was then analyzed with attenuated total reflectance (ATR)–Fourier transform infrared spectroscopy (FTIR). The results showed that all deuterium in the form of D2O was caught in the first water bubbler. The capture efficiency ranged from 22.32% to 61.13%. The lower efficiency capture can be explained as D2O in water can form a HDO molecule and its correct determination is problematic. The second type of experiment was carried out with T2O with an activity of 851 Bq and with tritiated oil with an activity of 2495 Bq. The T2O was added to the set amount of ion resins and dosed into MSO. A peristaltic pump dosed the tritiated oil. The flue gas was measured to determine oxidation efficiency, and the T2O was captured within the water bubblers. The water was analyzed with liquid scintillation spectroscopy. The capture efficiency ranged between 76.42% to 97.87%. The results showed that this technology is suitable for the detritiation of tritiated organic materials.

Degassing Dissolved Oxygen through Bubbling: The Contribution and Control of Vapor Bubbles

An innovative yet sustainable approach for industrial deaeration is proposed, with demonstrated results and analyses, to contribute to finding solutions to improve energy efficiency in this field. Vacuum bubbling deaeration, sharing the same working principles of solubility control and the mass diffusion through vapor (or steam) with conventional thermal deaeration processes, works, however, at lower vacuum pressures. It neither resorts to heating nor requires any third-party materials such as membranes or gases, achieving orders of magnitude of reduction in the expected energy consumption in a simple and concrete way. In this study, the mechanisms of vapor bubble generation and retention were discussed by employing a vacuum bubbling model based on the experimental apparatus at Kongju National University, which uses a venturi-nozzle bubbler. The four parameters influencing vapor bubble generation and retention were identified as vessel pressure p1, nozzle depth Δh, nozzle performance p4−p3, and water temperature Tw. A series of deaeration experiments using the present approach for a tap water sample of 360~400 L were conducted under four different conditions to investigate the effects of the water temperature, vessel pressure, and bubbler nozzle depth. Final dissolved oxygen (DO) concentrations close to zero could be achieved with a vessel pressure of p1=1 kPa, with different bubbling times to reach a zero mg/L reading of DO concentration (case 2 and 3), which demonstrates the vital roles of the vapor bubble generation condition of (psat−p3) and retention condition of (p4−psat) in achieving the lowest DO concentration. Analysis of the test results, based on the discrete-bubble model with the measured DO concentrations and degassing rates, showed promising results in reproducing the experimental data. Though the potential of vacuum bubbling deaeration is demonstrated, for the first time, to its full extent, further research efforts are encouraged in many areas, including more case-specific validation test cases with optimum operating conditions along with the study of more detailed modeling for performance prediction, including energy analysis.

Investigation of process parameters for solar fuel production using earth-abundant materials

Photoreduction of CO2 to solar fuels and chemicals offers a sustainable method to produce net zero energy vectors. For large-scale applications, it is crucial to develop an improved understanding of the influence of reaction conditions on the design and optimisation of the photoreactor. The performance of CuO impregnated on BaTiO3 photocatalyst was investigated and compared to pristine BaTiO3, and CuO impregnated on commercial P25 (CuO/P25) and ZnO. The influence of irradiance, CO2 and H2O flow and partial pressure, and CO2/H2O ratio on the product yield and selectivity were examined. Using Design of Experiments and Computational Fluid Dynamic modelling, the optimised reaction conditions were irradiance of 125 mW cm−2, with a CO2 flow of 0.09 mL min−1, and water bubbler temperature of 25 °C. At these conditions, a 2 and 10-fold increase of CO and CH4 production, respectively, were obtained, compared to baseline conditions as well as exhibited the highest CO and CH4 production rate compared to previous reports. Among the earth-abundant photocatalysts, CuO/P25 had the highest quantum yield for CH4 (φCH4: 0.47), whilst CuO/BaTiO3 exhibited highest φCO (0.09) and stability for CO production. The under-performing of BaTiO3 and CuO/BaTiO3 was attributed to the presence of amorphous phase in BaTiO3. This work reveals that the combination of catalyst design, reaction engineering, and modelling can improve the efficiencies of CO2 photoreduction.

Dissolving Diamond: Kinetics of the Dissolution of (100) and (110) Single Crystals in Nickel and Cobalt Films

We report a study of the kinetics of dissolution of (100) and (110) single-crystal diamond plates (“D(100)” and “D(110)”) in thin films of nickel (Ni) and cobalt (Co). This dissolution occurs at the metal–D(100) or metal–D(110) interface and was studied in the presence and also in the absence of water vapor at temperatures near 1000 °C. The single-crystal D(100) dissolves in Ni, and also in Co, in the temperature range 900–1050 °C. The dissolution is too slow to measure below 900 °C. In an argon (Ar) atmosphere (under an Ar(g) flow at 1000 sccm and 1 atm pressure, with no water vapor present in the reaction chamber) and at any temperature in the range 900–1050 °C, the metal film is rapidly saturated with dissolved carbon (C), thin graphite films form on the free metal surface and at the metal–D interface during heating at or above 650 °C, and the dissolution of the diamond then stops. For addition of water vapor, its partial pressure was controlled by using a water bubbler immersed in a constant temperature bath and Ar(g) was used as the carrier gas. We discovered two different regimes (I and II) for the kinetics of dissolution of D(100) and D(110), in which the rate-determining step was the removal of carbon atoms on the open metal surface (regime I, lower partial pressure of water vapor) or dissolution of diamond at the metal–diamond interface (regime II, higher partial pressure of water vapor) that yielded different Arrhenius parameters. Time-of-flight-secondary ion mass spectrometry depth profiles show the concentration gradient of C from a certain depth into the metal film surface down to the M–D(100) interface, and residual gas analyzer measurements show that the gas products formed in the presence of water vapor on the metal surface are CO and H2. It was found that the rate of dissolution of diamond in Co was higher than that in Ni for both D(100) and D(110) and for both regimes I and II, and possible reasons are suggested. We also found that D(111) could not be dissolved at the Ni/D(111) and Co/D(111) interface in the presence of water vapor (over the same range of sample temperatures). The reaction paths for dissolution of C at the M–D(100) or M–D(110) interface and for removal of C from the free surfaces of Ni and Co were assessed through density functional theory modeling at 1273 K.

Morphology and Growth Region Analysis of Carbon Nanotubes Growth in Water-Assisted Flame Synthesis

ABSTRACT Water has been proven to be an effective additive to enhance the growth rate and purity of the synthesized carbon nanotubes (CNTs) in the chemical vapor deposition (CVD) method. Due to similar CNT growth parameters in CVD and flame environment, it is expected that a similar effect can be replicated in CNT flame synthesis to a certain degree. The present study analyzes the effect of water addition to the fuel stream toward the CNT growth in methane diffusion flame under atmospheric conditions. Water vapor was introduced into the fuel gas by passing the methane gas through a water bubbler, and the growth condition was analyzed based on a cross-sectional analysis of the grown CNT on top of nickel wire. The water addition to the fuel reduces the axial extent of the growth region due to the reduction in flame height. Even though the spatial distribution of the growth region in the flame with water additive changes compared to that of the flame without water, the average growth region temperature is relatively identical for both flames at a similar height above the burner. The synthesized CNT morphology did not change with the addition of water due to similar temperatures within the growth region and inhomogeneity of catalyst nanoparticle formation. Remarkably, the thickness of the amorphous carbon layer in the growth region decreases by almost 20% in water-assisted flame due to the reduction of carbon supply caused by the modification of gas-phase chemical reaction and water vapor etching effects that happen within the growth region. Numerical simulation of the flame structure shows that addition of water vapor in the fuel stream lowers the methane concentration within the CNT growth region and simultaneously promotes water etching effects on the amorphous carbon layer.

Design and Analysis of Exhaled Breath Condenser System for Rapid Collection of Breath Condensate

Breath analysis has attracted a lot of interest for noninvasive health diagnostics method by detecting disease biomarkers. However, the exhaled breath collection process remains a challenge. Specifically, the effective separation of the water vapor from the breath sample, which is necessary to avoid humidity interference in gas detection system and to preserve the liquid condensate for other analysis. In this paper, an analytical model is developed to obtain the optimized condenser for portable breath collection system to effectively provide both dry gas phase sample and exhaled breath condensate. The mathematical model is verified by using a heated water bubbler as warm and humid air generator (in vitro). Furthermore, the performance of the device is tested by using actual human breath (in vivo). The in vitro test result shows the temperature and moisture concentration values have a good agreement with the measured values with margin of error ±15%, and ±30% for amount of collected condensate. The in vivo result shows, with the thermoelectric element cooled up to 8.5 °C, a moisture removal efficiency of 62.4% is achieved. In this case, the system can collect exhaled breath condensate of 0.457 ± 0.092 ml and dry gas (RH 47.8% at 27 °C) for 10 exhalations.

Sugar sweetened beverages and increasing prevalence of type 2 diabetes in the Indigenous community of Australia

AimsThe aim of this viewpoint was to discuss a profound health gap in type 2 diabetes that exists between Indigenous and non-Indigenous Australians. Data synthesisIn Australia, type 2 diabetes is ranked as the fastest growing chronic condition, with the rates of type 2 diabetes higher among Indigenous than non-Indigenous Australians. Improvements to diet could aid in reducing overweight and obesity in the Indigenous community, with sugar sweetened beverages (SSBs) examples of discretionary foods that contain a high amount of sugar. The marked increase in type 2 diabetes, obesity and consumption of SSBs in the Indigenous community may suggest that type 2 diabetes may result from weight gain caused by SSB consumption. Recent evidence suggests that higher consumption of SSBs was associated with greater incidence of type 2 diabetes independent of adiposity. Some determinants influencing increased SSBs consumption in the Indigenous population include advertising, marketing, availability and affordability. ConclusionsThe prevalence rates of type 2 diabetes continue to be higher among Indigenous than non-Indigenous Australians and overall, a link between SSBs and risk of type 2 diabetes is reported. Three solutions to high SSBs consumption in Indigenous communities include increased availability, affordability, and accessibility of healthy food and drink, engagement of Indigenous people in offering solutions including discussion of a sugar tax on SSBs framed with Indigenous input, and the provision of clean community water supply and water bubblers.

Design and Analysis of Breath Collection System for Rapid Analysis of Breath Condensate

Introduction Breath analysis has attracted a lot of interest as a less-invasive method for health diagnostics and the detection of biomarker for various illnesses. A number of research studies have examined miniaturization of the sensing devices to achieve portability and lower the cost so that point of care application can be considered [1]. However, one major issue in breath analysis is that the breath sample needs some preconditioning before sensing can be carried out. Specifically, the water droplets and water vapor fraction should be separated from the volatile organic compounds. [2]. For that reason, a miniaturized water vapor and suspended droplet extraction device would be useful for a portable breath analysis system. The device must be able to provide a dry breath sample gas at the outlet as well as collecting the extracted condensate which contains biomarkers for diseases [3]. In this paper, a serpentine-type mini channel [4] is proposed as miniaturized water vapor extraction device. An analytical model is developed to obtain the height, width, and length values of the channel that is sufficient to remove moisture content in exhaled breath as it is cooled by using thermoelectric element. Method An analytical mathematical model is developed to calculate the optimized channel dimensions with design objectives of maximum condensing water vapor, minimum overall space, and minimum pressure drop. Based on calculation, the geometrical dimensions of 3 x 0.5 x 30 mm (width x height x length) are selected. The mini channel is made of serpentine-patterned aluminum sheet and a lid made of PMMA (Figure 1a). The aluminum sheet and PMMA are hermetically bonded by using cyanoacrylate adhesive. To verify the calculated outlet temperature and water vapor concentration of breath flow as well as liquid collection rate of the device, an experiment using artificial breath flow is conducted with the setup as shown schematically in figure 1a. An artificial breath flow is generated by pumping ambient air at 0.06 L/s using a mini diaphragm pump (SparkFun Electronics RP 10398) through a water bubbler heated with a strip heater (HT640). It generates a humid air with RH 100% and temperature varied from 27-38oC in the mini channel inlet. The mini channel is cooled by a thermoelectric (Peltier) element (CP85438 40x40 mm) to a cold side temperature of 16oC. At the inlet and outlet side of the mini channel, a DHT22 sensor is attached to measure temperature and humidity value at both ends. Results and Conclusions Figure 1b and 1c shows the plot of temperature and water molecule concentration at the inlet and outlet side of the channel. Based on the result, the calculated temperature and water vapor concentration values have a good agreement with the measured values with margin of error ±10%. With the thermoelectric element cooled up to 16 oC, a moisture removal efficiency of 69.5% is achieved. In this case, the steady state liquid collection rate is 2 x 10-3 ml/s. It produces gas phase breath sample with RH 58% at room temperature (25 oC). Using the same model, calculation is further carried to obtain that theoretical removal efficiency of 90% can be achieved by cooling down the Peltier element to 0oC. In this case, the steady state liquid collection rate is 2.4 x 10-3 ml/s, and the device will produce gas phase breath sample with RH 18% at room temperature.

Tritium release behavior from neutron-irradiated FLiNaBe mixed with titanium powder

FLiNaBe is a promising liquid blanket material for a fusion reactor. Since hydrogen solubility for FLiNaBe is low, one concern is the permeation of bred tritium. In order to increase effective solubility of hydrogen, the addition of Ti powder was proposed. In this study, the influence of Ti addition on the behavior of tritium generated inside FLiNaBe by neutron irradiation was investigated. The samples of FLiNaBe and FLiNaBe mixed with Ti of 5 wt% and 0.5 wt% were prepared and the solid-state samples were irradiated by thermal neutrons at Kyoto University Research Reactor. The neutron-irradiated samples were heated to 700 °C in an Ar gas flow. The released tritium was collected by a water bubbler and the temporal variation of TF and HT release was observed. Initially, the most of tritium was released as HT from both FLiNaBe with and without Ti but eventually, the most of released tritium was HT after long time heating from FLiNaBe with Ti. This result suggests that the addition of Ti can decrease the release of TF very much. The amount of tritium released from FLiNaBe with Ti was lower than that from FLiNaBe without Ti. This result suggests that the addition of Ti can suppress the release rate of tritium from FLiNaBe.

Oxidation processes of NO for production of reactive nitrogen species in plasma activated water

To understand the mechanisms for selective productions of NO2− and NO3− as reactive nitrogen species (RNS) in plasma activated water, we studied the oxidation reactions of NO as the primary species supposing O, O2, O3, OH, and H2O2 as possible oxidants. A coaxial-type dielectric barrier discharge reactor was employed in cascade connection to a reservoir and/or a water bubbler. First, the densities of NO and NO2 in the gas phase were measured with gas sensors in two gas systems: N2 admixed with water vapor and N2 admixed with O2, for comparison. It was found that while the density of NO in the latter case was one third of that in the former case owing to the difference in the first-step oxidation to NO2 or HNO2, the total yields of RNS in both cases were comparable. To investigate the oxidation pathways, admixing NO and NO2 in the downflow of the reactor was attempted to estimate their reactions with those oxidants and accomodation behaviours on the water surface. Injecting the effluent gas from discharge plasma into solutions of O2, O3, and H2O2, and injecting O3 into PAW, vice versa, were attempted to inspect the reactions in the liquid phase or at the gas–water interface. Based on the obtained results, it was found that, in the N2-H2O gas system, OH functions as the oxidant of NO to HNO2, exclusively yielding NO2− in solution with no effective second-step oxidation to NO3 or HNO3. On the other hand, in the N2-O2 gas system, O3 functions as the major oxidant in the successive oxidation from NO to NO2 to NO3, producing NO3− predominant PAW; however, the second-step oxidation in the gas phase is competing with the oxidation reactions in the liquid phase.

Exhaust behavior of tritium from the large helical device in the first deuterium plasma experiment

ABSTRACT The tritium exhaust behavior from the Large Helical Device (LHD) was observed in the first deuterium plasma experimental campaign. Tritium in the exhaust gas was monitored at the conducted by use of the ionization chamber and water bubbler system with the discrimination of chemical forms. The observation results indicated that (i) tritium on the surface of the first wall and divertor tiles as plasma facing components was released by the hydrogen isotope exchange reaction of the glow discharge cleaning operation and the diffusion-limited process was suggested in the tritium release behavior from the bulk, (ii) the amount of tritium release from the LHD vacuum vessel was about one-third of the produced tritium and the mostly produced tritium was still retained at the end of plasma experimental campaign, (iii) the ratio of exhausted tritium from the LHD vacuum vessel was larger than that in the case of JT-60U based on the carbon materials as the plasma-facing components. It indicated that the tritium inventory would be reduced and controlled by the kind of plasma-facing materials.

Investigating the Reactivity of an SnO2 Metal Oxide Semiconductor Gas Sensor Under Siloxane Exposure

Introduction The impact of siloxane exposure on SnO2 based gas sensors is highly important in many applications due to the frequent occurrence of these substances in ambient air. This process is usually called poisoning since siloxane exposure leads to permanently impaired sensors, changing selectivity and decreasing sensitivity to gases [1] except for hydrogen [2]. The often observed first increase in sensitivity led to the complex interpretation of several surface sites [3]. Two independent investigations on the effect of siloxanes on the commercially available UST GGS 1530 (Umweltsensortechnik GmbH, Geschwenda, Germany) were conducted yielding the same output: the reactivity of the sensor’s surface is continuously reduced during siloxane exposure. Experimental The first investigation focused on the effects on the dynamic operation called differential surface reduction (DSR, described in [4]), where the sensor is alternating between a high temperature oxidation phase and a low temperature reduction phase, which enables the independent measurement of both processes. The rate constant for reducing gases reacting on the sensor surface is evaluated through the first derivative of the logarithmic conductivity ln(G) on the low temperature phase. Turning the DSR method around allows the evaluation of the differential surface oxidation (DSO) through the dynamic behavior of ln(G) during the high temperature phase. The second investigation targeted gas sensors for monitoring methane concentrations (<4.4 %) in harsh environments contaminated with siloxane.The measurements were performed in a gas mixing system similar to the system described in [4] consisting of mass flow controllers and valves. During the first investigation the humidity was always held at 50 % R.H, the second investigation included measurements at 0, 10 and 65 % R.H., supplied by a water bubbler at 20 °C.further described in [5]. (table 1) and increasing sensor temperature were performed, gas measurements with 2 ppm of hydrogen were conducted in between. The second investigation used the most abundant siloxane OMCTS (octamethylcyclotetrasiloxane) and the 2 l/min dilution MFC was omitted due to the low vapor pressure. The sensor was constantly operated at 400 °C. conducted, several methane concentrations and backgrounds were measured in between as seen in figure (Fig. 2). Results The main result from the first investigation on hydrogen is given in Fig. 1. Features from both DSR (middle, 300 °C) and DSO (right, 450 C°) are declining with increasing siloxane dosage, while the sensor response (left, 300 °C) shows no distinct trend. This indicates that siloxane exposure gradually slows down both surface reactions, which corresponds to a deactivation of active sites, i.e. a lower reactivity of the sensor surface, whereas the static equilibrium is shifted in different directions depending on the relative effect on hydrogen and oxygen reactivity at each treatment step.The deactivation of active surface sites can also be observed in steady state operation by an exposure to a high concentration of reducing gas, e.g. methane. The reaction (“combustion”) of methane creates excess heat reducing the heater power at constant temperature similar to a pellistor [6]. This effect is offset by the change in thermal conductivity of the surrounding gas which increases the heater power for higher methane concentrations. Siloxane exposure reduces the reaction rate and therefore the equilibrium between both effects is shifted towards thermal conductivity, thus increasing the power consumption. This is shown in Fig. 2, where the heater power difference in different gas compositions compared to dry air is plotted vs. the OMCTS dose. Results for 1 % methane in dry air shift from the combustion dominated (up to 10 ppmh OMCTS) to the thermal conductivity dominated (from 500 ppmh) region. At 65 % R.H., the thermal conductivity effect is always dominant independent of the OMCTS dosage, but also increases with siloxane exposure.Both described methods show independently that siloxane exposure decreases the reaction rates on the sensor surface affecting reduction and oxidation process, which can be exploited for sensor self-monitoring. In temperature cycled operation the resulting deterioration could be determined by evaluating the high temperature dynamic behavior, which is mainly reflecting the surrounding oxygen concentration. In atmospheres with varying oxygen concentration or other circumstances which interfere with the DSO evaluation, a reference gas mixture could be used to determine the balance between combustion and thermal conductivity as an indicator of the sensor state. Acknowledgement Part of this research was done within the project “GasMOS” funded by the European Regional Development Fund (ERDF). We want to thank our project partner Schaller automation GmbH & Co. KG for their ongoing support.

Does the Bubbler Scrub Key Toxicants from Waterpipe Tobacco Smoke?: Measurements and Modeling of CO, NO, PAH, Nicotine, and Particulate Matter Uptake.

Waterpipe tobacco smoking is a global epidemic. A persistent perception among users is that the water bubbler filters the smoke, reducing its risk profile. The objectives of this study were to quantify the purported filtering effect by comparing toxicant yield when a waterpipe was machine smoked with and without the smoke passing through the water bubbler. We found that the water bubbler did not reduce CO, NO, polycyclic aromatic hydrocarbons (PAHs), or dry particulate matter (DPM) yields but did reduce nicotine and carbonyl compounds (CCs) yields by approximately 50%. These mixed results were consistent with theoretical simulations of the mass transport processes involved.

Assessment of drinking water quality in regional New South Wales, Australia

Abstract There is a substantial research gap relating to the quality of drinking water in regional Australia and identifying possible improvements. In particular, the quality of water available in public places (washing and drinking), such as water bubblers installed in regional parks, schools, rest areas and railway stations, is poorly investigated. This paper discusses the primary and secondary water quality of eight water distribution networks in New South Wales (NSW) regional towns. An analysis of a large number of drinking water samples (more than 11,000) identified that maintaining microbial water quality and the required free chlorine level (&amp;gt;0.2 mg/L) are challenging issues for regional water distribution networks. Sixty-three per cent of the samples collected from the water outlets available in public places of a regional town showed free chlorine levels of &amp;lt;0.2 mg/L, and 30% of samples showed positive results for total coliform. All heavy metal levels of the samples were within the safe level. Water temperature was identified as the most problematic secondary water quality parameter in public water bubblers. Stainless steel was the common material used in bubblers where surface temperatures exceeded 50 °C during summer. This study identifies possible design and operational modifications to improve regional drinking water quality and make public water bubblers more usable.

Characterization of dielectric barrier discharges with water in correlation to productions of OH and H2O2 in gas and liquid phases

Using several types of dielectric barrier discharges, we studied the production mechanisms of H2O2 molecules in gas and liquid phases. Water vapor was supplied by a water bubbler in a gas-feed line or vaporization of water filling a lower electrode well. Densities of OH radicals were measured by optical emission and laser-induced fluorescence spectroscopic methods and correlated with the H2O2 production in gas phase. The energy yield of H2O2 obtained in the gas-phase synthesis with the supply of water vapor through the bubbler was on the 0.1 g kWh−1 order, while that in the synthesis with liquid electrode was larger than 1 g kWh−1. We investigated also the transport of OH and H2O2 species from gas phase to liquid phase, using additional supply of H2O2 through the outside bubbler and ethanol as an OH scavenger admixed either in the bubbling water or electrode water. From those results, we conclude that the production of H2O2 mainly proceeds in gas phase and the difference in the yields is attributed to the efficiency of extracting the product out of the discharge region before being decomposed by the repetitive discharge, which depends on the reactor schemes.

Determination of tritium activity and chemical forms in the exhaust gas from a large fusion test device

A water bubbler system that can distinguish chemical forms of tritium was proposed for long-term tritium monitoring of the exhaust gas of a large fusion test device. The characteristics and performance of the water bubbler system were evaluated under operational conditions and confirmed to be suitable for tritium monitoring. For the tritium measurements, the water bubbler system determined the tritium activity and distinguished the chemical forms of tritium. The tritium activity and chemical forms in the exhaust gas provided helpful information to understand the tritium behavior in the large fusion test device.

Tritium release from molten salt FLiNaK under low flux neutron irradiation with an AmBe neutron source

For examination of tritium transport in a self-cooled liquid blanket system using fluoride molten salt breeder/coolants, a series of neutron irradiation experiments have been conducted under the low flux neutron environment with an AmBe neutron source at the OKTAVIAN facility of Osaka University in Japan. Tritium release from molten salt FLiNaK (LiF-NaF-KF) at 773 K is evaluated with the neutron source, energies of which are up to 10.7 MeV and the intensity is ∼2 × 106 n/s. To measure the amount of tritium released from FLiNaK and permeating through an Inconel crucible, TF and/or T2O, and T2 are recovered separately using water bubblers and CuO oxidation beds. The amount of tritium recovered for one week in a steady state, 12.0 Bq, has closed to the calculated value, 10.6 Bq, obtained with MCNP6. More than 98% of the recovered tritium from FLiNaK has been TF and/or T2O. The overall mass transfer coefficients for tritium released from a FLiNaK free surface have been evaluated from the transient changes in recovered tritium and those are comparable to the value for HF released from FLiBe previously reported in the literature.

Separation of weighable amounts of 10Be from proton irradiated graphite

Large amounts of 10Be are produced at the PSI muon production facility by high-energy proton spallation in polycrystalline graphite. For the extraction of 10Be out of large amounts of carbon, pyrolysis followed by chemical purification has been performed. Approx. 270g of graphite from Target E92, which had received a total proton charge of 29 Ah between 2002 and 2005, have been burned at 1000°C in a stream of oxygen. The volatile radioactive oxidation product 3H2O was trapped in 3 water bubblers connected in series. The remainder, a white hygroscopic solid material mainly consisting of 7Li2O, 9/10BeO and 10/11B2O3, was dissolved in HF and subsequently purified by ion exchange chromatography. Radioactive impurities such as 22Na, 44Ti, 54Mn, 60Co, 101Rh, 133Ba and 172Hf have been separated from the final product. The purified material represents a mixture of approx. 6.5mg 9Be and 3.5mg (3.3MBq) 10Be. It is ready to be used for scientific investigations requiring large amounts of this precious isotope.

Performance of tritium analysis system using inorganic-based hydrophobic platinum catalyst

A method combined oxidation catalytic reactor and water bubbler is the most quantitative analysis method for gaseous tritium. We developed a tritium measurement system with high accuracy using an organic-based hydrophobic platinum catalyst previously. However, the previous measurement system had a shortcoming that the catalyst was combustible over 100°C. To overcome the shortcoming, we developed an inorganic-based hydrophobic platinum catalyst (Pt/SiO2) which was noncombustible. The developed Pt/SiO2 catalyst was specially enhanced the hydrophobicity to prevent adsorption of water vapor on the surface of catalyst. To oxidize tritium efficiently, the particle diameter of 1mmϕ was selected for the catalyst and hydrogen was intentionally added at the inlet of the catalytic reactor to be the optimal concentration for oxidation. The performance tests showed that a modified quantitative tritium analysis system using by the hydrophobic Pt/SiO2 catalyst provides tritium measurement with high accuracy more than 99.9%. We have confirmed the modified quantitative tritium analysis system is available in various conditions.

Infrared Study of Room Temperature Atomic Layer Deposition of SnO2 Using Sn(CH3)4 and Plasma Excited Humidified Argon

Tin oxide (SnO2) is an oxide semiconductor material with an excellent optical transparency, where it is used as transparent conducting films. It is also used as a channel material for gas sensors. Recently atomic layer deposition (ALD) of SnO2 has been studied intensively since ALD allows the conformal deposition of the oxide film with an atomic level precision. However, the high process temperature in excess of 100 °C in the conventional SnO2 ALD is a major problem for its application for flexible electronics. We developed a room temperature deposition technique with a precursor of tetramethyl tin (Sn(CH3)4, TMT) and plasma excited humidified argon. The surface reaction of the precursor adsorption and its oxidization were monitored by infrared absorption spectroscopy (IRAS) with a multiple-internal-reflection (MIR) geometry.A p-type Si(100) substrate with a resistivity of 8-12 Ωcm was used as a sample. Prior to the experiment, the sample was cleaned with buffered HF acid and sulfuric acid-hydrogen peroxide mixture solutions. The Sn precursor of TMT was introduced with a variable leak valve. A plasma excited humidified argon source was installed to the ALD chamber as shown in Fig. 1. The source gas for OH-radical is a mixture of H2O vapor and Ar made by a water bubbler. The plasma was generated in a glass tube with an induction coil with a frequency of 13.56MHz and a RF power of 30 W. Before the ALD process, the substrate surface was treated with the plasma excited humidified argon for 5 min to be terminated with Si-OH. For the SnO2 deposition, we repeated the cycle of TMT saturation and plasma excited humidified argon at RT. The condition of TMT saturation and oxidization were determined by the MIR-IRAS experiment. In this experiment, the TMT saturation exposure and oxidization time were 2×105 Langmuir and 10 min, respectively. The oxidation state of the SnO2 film was evaluated by X-ray photoelectron spectroscopy (XPS). The thickness of the grown film was measured by spectroscopic ellipsometry.In Fig. 2, we show Sn 3d XPS spectra obtained from the RT grown SnO2 film, where we confirm the evolution of full oxidized state peak according to the increase in the ALD cycle number. We calculated the growth per cycle as 0.02 nm/cycle. In the conference, we present the results of RT ALD of SnO2 and discuss the surface-reaction mechanism based on the IRAS observation. Acknowledgement; This work was partly supported by JST-CREST, JSPS KAKENHI Grant Numbers 15H03536 and 15K13299. Figure 1