Very little data was available to construct the hydrogeological model. The available data suggests that the Dimitrovgrad site lies at the minimum of an extensive sedimentary basin. The region of interest thus has the hydrogeological features of an artesian basin. In order to investigate the discharge pathway a NAMMU model consisting of a two-dimensional vertical cross section through the site was set up. This cross section followed a NW-SE line, with the lowest point near the centre of the model, and higher ground at the NW and SE extremes. The model extended some 18km NW of the NIIAR site, and 20km SE of the site. This choice of cross-section also allowed the potentially significant hydrological feature of the Bol Cheremshan river to be represented in the model. The geological sequence below the NIIAR site comprises several relatively permeable layers (mainly limestones and dolomites), which are separated from each other by regionally extensive confining layers (which are generally agrillaceous). This sequence extends over distances of hundreds of kilometres around the NIIAR site, and it is believed that the confining layers act as regional confining beds.

In the former Soviet Union, deep borehole injection of liquid radioactive waste has been established practice at least since 1963. The liquid is injected into sandy or other formations with high porosity, which are isolated by water-tight layers. This technique has also been used elsewhere for toxic liquid waste and residues from mining operations.

In order to obtain a better understanding of this technique the European Commission has funded a study of the deep-well injection repository at the Research Institute for Nuclear Reactors (NIIAR) in Dimitrovgrad, Russia. The research activities of NIIAR generate liquid waste of complex chemical and radionuclide composition, the radionuclides being almost exclusively short-lived. The annual discharge rate during the last years of operation was 55,000 - 65,000 m³. The groundwater pathway is the natural route by which radionuclides may return to the environment, and so the study of the site included a calculation of the regional groundwater flow, and the local flow in the injection zones.

A significant feature of the site is the high salinity of the deeper groundwater, into which the waste has been injected. This salinity leads to density variations, which will have a significant influence on the regional groundwater flow. This required a fully-coupled groundwater flow and salt transport calculation to be undertaken.