To evaluate the effects of environmental-burden substances such as radioactive contaminants, it is essential to identify the migration patterns and behaviors of these substances in the environments that comprise the earth's ecosystem. The mechanisms affecting substance migration patterns and behaviors are very complicated and cover a wide range of disciplines (Fig. 9-4). In addition, as the ecosystem contains a mixed variety of land usage modes (including forests, farm fields and rice paddies), the migration patterns of the substances in each of the various land usage classifications are quite diverse. As a means of analyzing and predicting the migration of the substances under the above conditions, we have developed the fundamentals of the Migration Of GRound Additions (MOGRA) code. MOGRA consists of computational codes that are applicable to various evaluation target systems and can be used on personal computers. This code has a dynamic compartment model analysis block at its core, a graphical user interface (GUI) for computation parameter settings and results displays, data files, and so on. The compartments are obtained by classifying various natural environments into groups that exhibit similar properties. The system features near-universal applicability and excellent expandability for computations of various nuclides. An evaluation begins with a classification of the target land biosphere according to a land usage classification called a module (Fig. 9-5). Next, desired compartments are set within each module (Fig. 9-6) together with the selection of migration patterns of substances between modules. The flow of environmental-burden substances between compartments is expressed in the formulae obtained from theoretical considerations and/or scientific experimental results. When a compartment in a module is subject to pollution by an environmental-burden substance (for example when water in a rice paddy is polluted), these codes can be used to evaluate how and to what extent the surrounding environments will be polluted in the future (Fig. 9-7).
|