@misc{oai:repo.qst.go.jp:00068107,
 author = {Yamamoto, Kazuhide and Sakashita, Tetsuya and Miyamoto, Kiriko and 山本 一英 and 坂下 哲哉 and 宮本 霧子},
 month = {Sep},
 note = {An international program for validation of the environmental model of tritium was completed in IAEA BIOMASS (Biosphere Modeling and Assessment, 1996-2001), and another program is continuing as IAEA EMRAS (Environmental Modeling for Radiation Safety, 2003-2006).  Although the site on which ITER (International Thermonuclear Experimental Reactor) will be constructed was not decided by the deadline for submitting this abstract, the international cooperation work for assessment of environmental safety of tritium, the fuel for ITER, is ahead of schedule.  In the present work, an atmospheric dispersion model of tritium was developed and validated using the additional data supplied by scenario writers from two countries after the official program of BIOMASS was finished.  The model focuses on short-term time variation of dispersion in the atmosphere, dry and wet deposition and re-emission from the soil surface, as the mobility of tritium in such processes is influenced much by short-term time variation of local meteorological factors in the case of accidental release.
The model in this work was based on a random walking particle type for the atmospheric dispersion, written with the Visual BasicTM language in the WindowsTM system.  Atmospheric dispersions of HT and HTO were simulated by the movements of particles with various fractions of HT and HTO radioactivities.  To reduce the time to calculate each radioactivity, the Kernel Density Estimator method was applied.  Time variation of dispersing locations of the particles and the fractions of HT and HTO could be followed visually by movement of circles with color gradation of red and blue mixture on a display screen.
The model was validated with the observed data of tritium concentrations in the soil water, in rain or snow, as well as in the atmospheric vapor in two countries.  Although the average values of tritium concentrations observed during a considerably long period were used for the model validation in the BIOMASS official program, the authors asked the scenario writers to supply individual time series data of tritium concentration observed, with which the calculated results were found to fit time dependently.  The authors also found that some minute variations in the observed data could be simulated by the model in this work with fine tuning of parameters., 第７回トリチウム科学技術国際会議},
 title = {Development and Validation of an Atmospheric Dispersion Model for Tritium Using the IAEA BIOMASS Scenario},
 year = {2004}
}