Development of a generic analysis code of dynamic compartment model for evaluation of doses in terrestrial biosphere

The release rate of a nuclide from a reactor or a radioactive waste disposal plant at the accident is not steady, but varies with time. The various parameters of a nuclide migration into environment vary also day after day, or with the seasons. In such cases, dynamic behavior of the nuclide in the environment must be taken into consideration. It is difficult for a mathematical model to involve all of mechanisms for the nuclide migration. The environment for evaluation of doses are usually divided into some of compartments in which a nuclide concentration is uniform. Time variations of the nuclide concentration in the compartment are described in simultaneous differential equations. The nuclide concentration can be solved as a time function, and the radiation doses, therefore, can be estimated as a time function. Generic analysis code for dynamic compartment model (GACOM) is developed for the nuclide migration and the evaluation of doses in terrestrial biosphere. The code contains many items, such as atmospheric release, vertical migration between surface soil layers, lake system, nuclide concentrations in the compartment, internal doses by inhalation, internal doses by ingestion of drinking water, crops, animal products, aquatic products, and external doses. The GACOM has been confirmed by the analysis of international cooperational research program (BIOMOVS II): long term contaminant migration and impacts from uranium mill tailing. (Suetake, M.)