Temperature pattern in deep burial of liquid radioactive waste

Abstract

Deep burial of liquid radioactive wastes in porous rocks is one of the methods of dealing with waste used in Russia [1]. Reliability in localizing wastes in such stores is determined primarily by the geological parameters, which should guarantee isolation from the surface and aquifers. The wastes represent a complicated multicomponent system, which may influence geochemical equilibria and alter the conditions in an underground store [2, 3]. Therefore, long-time forecasting for the state of such a store is impossible unless one knows the main transformations occurring in the waste-groundwater-rock system [4, 5].There is evidence on the main parameters governing the trends and extents of physicochemical processes in the thermal and radiation fields from the behavior of major components of the wastes and the radionuclides, including sorption on rocks, coprecipitation on solids, and so on [6][7][8][9]. The stratal temperature can be monitored periodically in injection and observation boreholes. These data characterize individual points but do not give a general picture of the temperature pattern and do not define zones of maximum heating or the temperatures there. To forecast component states at various times after deposition, one needs to know the distributions of the heat and dose levels throughout the store.Descriptions have been given [10] of ways of determining energy release and radiation doses in deep storage. Methods have been given [11] for calculating temperature patterns in storing liquids with the addition of cement involving hydraulic stratal fracturing. That form differs considerably from the storage of liquid wastes because the cement converts them to the solid state, which radically alters heat transfer. Thermal calculations on liquid waste storage [4, 7, 12] have shown that agreement is obtained with experiment when one considers the detailed technology, which includes not only depositing the wastes but also the injection of preparatory and displacing solutions. That is fairly obvious because the supply of large amounts of inactive solutions substantially reduces the radionuclide concentrations, as the radionuclides are the sources of heat and affect the heat-transfer conditions. Unfortunately, those papers give no details of the models, and the software used remains unknown, so one cannot perform calculations for other storage conditions.The data show that one can characterize the state of an underground waste store from a model that includes the following: 1) description of deposition in the storage rock; 2) calculation of energy production and radiation dosage; 3) calculation of temperature pattern at various times; 4) a physicochemical model for the state of the components that includes sedimentation, sorption, coprecipitation, and so on; and 5) calculations on component migration underground.

Mathematical Simulation of the Behavior of Spent Organic Extracting Agent in the Near-Well Region in the Case of Deep Burial

“…3. Specific activity in the reservoir bed versus the distance from the well: 1, 2 and 3, 4) short-and long-lived radionuclides, respectively; 1, 3) in the year when operation stopped; 2, 4) after 10 yr (3, 4 magnified by a factor of 10, 2 -by a factor of 1000). mined by the interphase distribution coefficients.…”

“…As a result, filtration of the wastes occurs along individual most highly permeable intercalations, and not along the entire thickness of the opening of the well or water-bearing level. Different mathematical models, for example [2][3][4][5][6], are used to predict the migration of radionuclides and the dynamics of the temperature field in a reservoir bed for burying water wastes. However, they describe single-phase filtration and cannot be used to investigate the behavior of organic wastes in an underground water-bearing formation.…”

“…2. Concentration of TBP (1, 2) and hydrocarbon diluent (4,5) in the organic phase, degree of saturation of the organic phase (3,6) in the reservoir bed as a function of distance from the wells: 2, 5,6) in the year when operation stops; 1, 3, 4) 10 yr after operation stopped. Fig.…”

“…After the operation of the well is terminated, the total activity of the short-lived radionuclides decreases rapidly and the contribution of long-lived radionuclides to the energy release becomes dominant. Temperature (1, 2) and specific intensity of energy release (3,4) versus distance from the well: 1, 3) in the year when operation stopped; 2, 4) after 10 yr. At the completion of the displacement of the organic phase and its immobilization, the amount of initial organic substances in the formation decreases as a result of radiolysis and hydrolysis. The region with the highest rate of decomposition of organic macrocomponents coincides with the region of maximum activity.…”

Gas release from deeply buried liquid radioactive wastes

“…We used the computer program NEAT [6,7] to perform calculations of the time dependences of the temperature in the reservoir formation for an 11-stage run for buring wastes into well N-2 (Fig. 2).…”