Global fallout levels of 99Tc and activity ratio of 99Tc/137Cs in the Pacific Ocean

Global fallout levels of 99Tc and 137Cs of surface seawater in the Pacific Ocean were measured. The 99Tc concentrations ranged from 0.62 to 3.33 mBq.m-3 and 5 of 6 samples showed less than 1 mBq.m-3 except one sample taken in the Great Barrier Reef, Australia. The 137Cs concentrations ranged from 2.13 to 3.14 Bq.m-3, showing a gradual decrease in the North Pacific toward the equator and a constant level in theSouth Pacific. The 99Tc/137Cs activity ratios ranged from 2.5.10-4 to 2.9.10-4, which is very close to that calculated theoretically from the fission yiel

Distribution and behavior of Tc-99 and Cs-137 in surface seawater of Pacific Ocean

International Conference on Radioactivity in the Environmen

Development of Field Estimation Technique and Improvement of Environmental Tritium Behavior Model

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

Preliminary Investigation of Pretreatment Methods for Liquid Scintillation Measurements of Environmental Water Samples Using Ion Exchange Resins

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^ 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)

Behavior of Environmental Tritium at NIFS Toki Site of Japan

The levels of tritium in the atmosphere are nowadays almost only of natural origin and of the same range as before the era of the nuclear tests. In order to appraise the influence of tritium released from nuclear facilities to the environment, it is necessary to confirm the effect of tritium appearing overlapped on background tritium levels. Tritium concentrations and stable isotopes of oxygen and hydrogen in rain water, stream water and groundwater at the NIFS (National Institute for Fusion Science, Gifu prefecture, Japan) site were analyzed to understand behavior of the natural tritium in coupling with rain event. Conductivity, temperature and flow rate of the stream were monitored continuously. The range of tritium concentrations in rain for three year period was 0.09-0.78 Bq/l (average 0.37 +- 0.14 Bq/l). The tritium concentrations of stream water and groundwater were almost constant, 0.34 Bq/l and 0.25 Bq/l, respectively. The isotopic ratio of oxygen and hydrogen showed a typical seasonal pattern observed in Japan. Two component separation analysis was carried out for the stream water at the time of rain using isotopic ratio, conductivity and tritium concentration