Fast Tool for Plume Migration of Radionuclide Decay Chain and Its Application to Dose and Health Risk Assessment

During the transport process, radionuclides can form mobile, toxic and harmful daughter products due to a series of decay reactions. None of the existing analytical models for single-species radionuclide transport are capable of accurately evaluating plume development of the daughter species of radionuclides because they do not account for mass accumulation from the parent species. Analytical models for multiple nuclides transport equations coupled with first-order sequential decay reactions can serve as fast and cost-effective tools for the predictions of the transport of the predecessor and successor species of radionuclide decay chain. In this project, we target to develop a rapid tool for rapidly predicting the plume behavior of an arbitrary length radionuclide transport decay chain. This fast tool is achieved based on generalized analytical solutions derived for a set of three-dimensional transient advection-dispersion equations (ADEs) coupled with sequential first-order decay reactions in a sem-infinite groundwater system. First, the coupled three-dimensional transient ADEs are converted to a set of ordinary differential equations (ODEs) via the Laplace transform and double finite Fourier cosine transforms. Subsequently, the solutions for each species are sequentially obtained by solving the resulting ODEs. The novel solutions will be expressed in terms of complementary error functions and exponential functions that are computationally efficient. Moreover, a graphical user interface (GUI) will be developed to facilitate the manipulation of the derived analytical model. Ultimately, we combine the derived analytical model with the health risk assessment model to evaluate the dose and risk. The model developed in this project will be a rapid tool for assessing the performance of deep geological disposal of radioactive waste or environmental impact of the accidental radionuclide releases such as the Fukushima nuclear disaster where multiple radionuclides leaked through the reactor, subsequently contaminating the local groundwater and ocean seawater in the vicinity of the nuclear plant.