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Tritium monitoring would be required at the site of the fusion test facility from the viewpoints of radiation safety and public acceptance. As one of the tritium monitoring items, atmospheric tritium monitoring in the environment is conducted and has three chemical forms: tritiated water vapor (HTO), tritiated molecular hydrogen (HT), and tritiated methane (CH3T). It is well-known that the specific activity of HT and CH3T is much higher than that of HTO. To investigate the cause of high specific activity, we focus on the behavior of molecular hydrogen (H2) in the atmosphere and develop a measurement system based on a gas chromatograph. Monitoring results showed that the range of the H2 mixing ratio at the NIFS Toki site was 0.4 ∼ 0.6 ppm over the observation period. Atmospheric H2 concentrations were higher during the daytime and long daylight seasons, suggesting the generation of hydrogen by photochemical reactions. Preliminary results suggest that there does not appear to be a clear correlation between the concentration of atmospheric HT and the concentration of H2 in the atmosphere. This suggests that the source of HT is different from the source of H2 in the atmosphere., source:http://doi.org/10.1585/pfr.18.2405038, identifier:0000-0001-9941-1958

The conventional method for FWT and OBT analysis is a liquid scintillation counting method after freeze-drying and combustion of the sample. However, pretreatment for FWT and OBT analysis are complicated and time consuming processes over weeks. Thus, we propose the application of microwave heating technique to save time and effort of the pretreatment of plant samples for FWT analysis. To understand the behavior of the combustion and drying of organic samples, we conducted TG/DTA analysis of pine needle samples. It is found that the sample has to be heated up to 100 - 110 ℃ for complete drying under N2 gas flow condition. Then, we tried the water recovery from fresh pine needle samples by the multi-mode microwave heating system. As a results, it was provided to good recovery yield achieved more than 97% under these experimental conditions. This result shows more preferable for the pretreatment of organic samples by microwave irradiation method than the conventional method., source:https://doi.org/10.1585/pfr.11.2405017, identifier:0000-0001-9074-115X

We have developed a rapid sampling system for measuring the tritium in atmospheric water vapor. The system consists of a high-efficiency particulate air filter cartridge, an oil-free compressor, a water-vapor-separating module with hollow fiber membranes, two cold traps, and an oil-free rotary pump. Compressed air (0.4 - 0.7 MPa) is introduced into the water-vapor-separation module, which consists of a stainless steel column containing polyimide membrane tubes. Water vapor permeates through the tubes and is collected by cold traps cooled with dry ice and ethanol. The module is heated with a flexible heater to control its temperature. We have determined the recovery yields under various sampling conditions and find that this system can collect atmospheric water vapor with a recovery yield of > 99 %. This system can thus be a useful tool for understanding short-term observations of tritium in atmospheric water vapor., source:https://doi.org/10.1585/pfr.13.3405064, identifier:0000-0001-9074-115X

To estimate the environmental transfer of tritium into the atmosphere and to establish tritium analysis techniques, this study improves our previous compartment model and proposes new analytical technique based on the microwave heating method and a water-sample purification technique using ion resin. This article introduces a new conceptual approach for estimating environmental tritium behavior., source:https://doi.org/10.1585/pfr.14.3405099, identifier:0000-0003-3140-1061

This paper presents an evaluation of a rapid pretreatment method for tritium analysis, that uses ion exchange resins (the batch method). The standard water samples were prepared with river water collected in Okinawa, Japan. Powdex resin was used in this study, which is an ion exchange resins in the form of powder beads. First, 100 mL of the standard sample was stirred with the cation exchange (PCH) and anion exchange (PAO) resins, as well as with activated carbon. To determine the optimal stirring time, we tested stirring times of 5, 10, 20 and 30 min. Additionally, to determine a suitable amount of ion exchange resin for environmental water samples, variations in the amount of resin and activated carbon were tested. Under the conditions of Experiment-3 (0.3 g, 0.3 g and 0.6 g of PCH, PAO and activated carbon, respectively) and with a stirring time of 5 min, electrical conductivity values of less than 1 mSm−1 were achieved. These results demonstrate the effectiveness of the removal of impurities in the sample water by ion exchange resins and confirm that such an effect can be achieved during a short period of time (i.e., in 5 min)., source:https://doi.org/10.1585/pfr.15.2405027, identifier:0000-0002-0580-0328