Adelikhah Mohammademad

Numerical and Experimental Investigation of Radon and Progeny in Residential Areas

Pannon Egyetem

Kémiai és Környezettudományi Doktori Iskola

Kovács Tibor

egyéni

PhD

Geological repositories for disposal of high-level nuclear wastes generally rely on a multi-barrier system to isolate radioactive wastes from the biosphere. The multi-barrier system typically consists of the natural barrier system, which includes the repository host rock and its surrounding subsurface environment, and the engineered barrier system (EBS). The EBS represents the man-made, engineered materials placed within a repository, including the waste form, waste canisters, buffer materials, backfill, and seals. The EBS plays a significant role in the containment and long-term retardation of radionuclide release. The main component of the EBS used in a number of countries is bentonite or a bentonite-sand mixture. Bentonite is a clay with a high content of smectite minerals, having properties very suitable for isolating radioactive waste canisters. It has a very low hydraulic conductivity and very low anion diffusion capacity and low transport capacity of positive charged radionuclides. Thus it can serve as a good buffer around the waste canisters. Mechanically, its high swelling potential makes possible self-sealing of openings within the EBS system and of gaps between the bentonite with the rock and with the radioactive waste canister. The transport of radioactive contaminants through bentonite layers is expected to be dominated by diffusion processes. Hence, laboratory diffusion testing is an important component for the design of waste containment barriers. As the basis of nuclear fuel, uranium is one of the primary elements to be considered in performance assessments for nuclear waste repositories. Furthermore, other radionuclides that are bound in the fuel matrix can only be released at the same rate as uranium dissolves and diffuses through the EBS. Hence, a fundamental understanding of uranium diffusion through bentonite is essential. In addition, in conceptual diffusion studies, uranium can serve as a useful ‘analog’ for other radioactive contaminants, such as Pu, Np, and Am. The primary goal of this study is to (1) characterize U (VI) sorption and diffusion behavior in terms of chemical solution conditions (pH, salt composition, ionic strength, total carbonate concentration) and degree of clay compaction, and (2) provide experimental data for reactive U (VI) diffusion model. The laboratory-scale experiments use to evaluate U (VI) sorption and diffusion behavior in different chemical conditions. The different nuclear measurements will use in these experiments.

2018-09-01

2022-08-01

fokozatot szerzett

Numerical and Experimental Investigation of Radon and Progeny in Residential Areas

Numerical and Experimental Investigation of Radon and Progeny in Residential Areas

2023-04-14 13:30

2023-05-04