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Turkeltaub T, Weisbrod N, Zavarin M, Chang E, Kersting AB, Teutsch N, Roded S, Tran EL, Geller Y, Gerera Y, Klein-BenDavid O. Radionuclide transport in fractured chalk under abrupt changes in salinity. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 912:168636. [PMID: 37981163 DOI: 10.1016/j.scitotenv.2023.168636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Revised: 11/13/2023] [Accepted: 11/14/2023] [Indexed: 11/21/2023]
Abstract
Internationally, it has been agreed that geologic repositories for spent fuel and radioactive waste are considered the internationally agreed upon solution for intermediate and long-term disposal. In countries where traditional nuclear waste repository host rocks (e.g., clay, salt, granite) are not available, other low permeability lithologies must be studied. Here, chalk is considered to determine its viability for disposal. Despite chalk's low bulk permeability, it may contain fracture networks that can facilitate radionuclide transport. In arid areas, groundwater salinity may change seasonally due to the mixing between brackish groundwater and fresh meteoric water. Such salinity changes may impact the radionuclides' mobility. In this study, radioactive U(VI) and radionuclide simulant tracers (Sr, Ce and Re) were injected into a naturally fractured chalk core. The mobility of tracers was investigated under abrupt salinity variations. Two solutions were used: a low ionic strength (IS) artificial rainwater (ARW; IS ∼0.002) and a high IS artificial groundwater (AGW; IS ∼0.2). During the experiments, the tracers were added to ARW, then the carrier was changed to AGW, and vice versa. Ce was mobile only in colloidal form, while Re was transported as a conservative tracer. Both Re and Ce demonstrated no change in mobility due to salinity changes. In contrast, U and Sr showed increased mobility when AGW was introduced and decreased mobility when ARW was introduced into the core. These experimental results, supported by reactive transport modeling, suggest that saline groundwater solutions promote U and Sr release via ion-exchange and enhance their migration in fractured chalk. The study emphasizes the impact of salinity variations near spent fuel repositories and their possible impact on radionuclide mobility.
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Affiliation(s)
- Tuvia Turkeltaub
- The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Midreshet Ben Gurion 8499000, Israel.
| | - Noam Weisbrod
- The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Midreshet Ben Gurion 8499000, Israel
| | - Mavrik Zavarin
- Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94550, USA
| | - Elliot Chang
- Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94550, USA
| | - Annie B Kersting
- Glenn T. Seaborg Institute, Lawrence Livermore National Laboratory, PO Box 808, Livermore, CA 94550, USA
| | - Nadya Teutsch
- Geological Survey of Israel, 32 Yeshayahu Leibowitz St., Jerusalem 9371234, Israel
| | - Sari Roded
- The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Midreshet Ben Gurion 8499000, Israel
| | - Emily L Tran
- The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Midreshet Ben Gurion 8499000, Israel; Now at Shamir Research Institute, University of Haifa, Qatsrin 1290000, Israel
| | - Yehonatan Geller
- Geological and Environmental Science Department, Ben Gurion University of the Negev, Beersheva 8410501, Israel
| | - Yarden Gerera
- The Zuckerburg Institute for Water Research, The Jacob Blaustein Institutes for Desert Research, Ben Gurion University of the Negev, Midreshet Ben Gurion 8499000, Israel
| | - Ofra Klein-BenDavid
- Nuclear Research Center of the Negev, Negev, P.O. Box 9001, Beersheva 8419001, Israel; Geological and Environmental Science Department, Ben Gurion University of the Negev, Beersheva 8410501, Israel
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Multimodal Carbonates: Distribution of Oil Saturation in the Microporous Regions of Arab Formations. ENERGIES 2022. [DOI: 10.3390/en15031243] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Perhaps as much as 50% of the oil-in-place in carbonate formations around the world is locked away in the easy to bypass microporosity. If some of this oil is unlocked by the improved recovery processes focused on tight carbonate formations, the world may gain a major source of lower-rate power over several decades. Here, we overview the Arab D formation in the largest oil field on earth, the Ghawar. We investigate the occurrence of microporosity of different origins and sizes using scanning electron microscopy (SEM) and pore casting techniques. Then, we present a robust calculation of the probability of invasion and oil saturation distribution in the nested micropores using mercury injection capillary pressure data available in the literature. We show that large portions of the micropores in Arab D formation would have been bypassed during primary drainage unless the invading crude oil ganglia were sufficiently long. We also show that, under prevailing conditions of primary drainage of the strongly water-wet Arab formations in the Ghawar, the microporosity there was invaded and the porosity-weighted initial oil saturations of 60–85% are expected. Considering the asphaltenic nature of crude oil in the Ghawar, we expect the invaded portions of the pores to turn mixed-wet, thus becoming inaccessible to waterflooding until further measures are taken to modify the system’s surface chemistry and/or create substantial local pore pressure gradients.
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