Development and analysis of a dynamic compartment model to predict carbon-14 behavior in rice paddy field for dose assessment of atmospheric release

Abstract

Abstract Carbon-14 is one of the critical radionuclides for the dose estimation from nuclear fuel reprocessing plants and nuclear waste disposal facilities. To assess the impact on public health caused by carbon-14 released from these nuclear facilities in Japan, a reasonable estimation of internal dose from the rice ingestion is necessary because rice is a staple food. Therefore, we are developing a dynamic compartment model to predict carbon-14 behavior in atmosphere – paddy soil – rice plant system and carbon-14 concentration in rice by using a migration prediction code, MOGRA. In this model, growing curves of “leaf and stem part” and “ear part” of a rice plant were fitted to sigmoid curves. The transfer coefficients between the compartments were estimated by using sub-models and parameters which describe transfer mechanisms of carbon in a rice paddy field, such as photosynthesis, translocation and respiration in a rice plant. A validation study of the model, carried out with “Rice Scenario” presented by the IAEA EMRAS (Environmental Modelling for RAdiation Safety) project, showed that the developed model can be practically used to predict the carbon-14 concentration in rice. The model was also applied for hypothetical releases of carbon-14 from nuclear fuel reprocessing plant. In addition, parameter sensitivity analyses were carried out to select critical parameters.