Review of concrete biodeterioration in relation to nuclear waste

Abstract

Storage of radioactive waste in concrete structures is a means of containing wastes and related radionuclides generated from nuclear operations in many countries. Previous efforts related to microbial impacts on concrete structures that are used to contain radioactive waste showed that microbial activity can play a significant role in the process of concrete degradation and ultimately structural deterioration. This literature review examines the research in this field and is focused on specific parameters that are applicable to modeling and prediction of the fate of concrete structures used to store or dispose of radioactive waste. Rates of concrete biodegradation vary with the environmental conditions, illustrating a need to understand the bioavailability of key compounds involved in microbial activity. Specific parameters require pH and osmotic pressure to be within a certain range to allow for microbial growth as well as the availability and abundance of energy sources such as components involved in sulfur, iron and nitrogen oxidation. Carbon flow and availability are also factors to consider in predicting concrete biodegradation. The microbial contribution to degradation of the concrete structures containing radioactive waste is a constant possibility. The rate and degree of concrete biodegradation is dependent on numerous physical, chemical and biological parameters. Parameters to focus on for modeling activities and possible options for mitigation that would minimize concrete biodegradation are discussed and include key conditions that drive microbial activity on concrete surfaces.

Microbially Induced Calcium Carbonate Precipitation (MICP) and Its Potential in Bioconcrete: Microbiological and Molecular Concepts

“…The industrial process involved in cement production from lime (precursor of concrete), consumes between 2 and 3% of the global energy demand, generating 0.73-0.99 t CO 2 /t of cement produced, which accounts for about 8-10% of the global anthropogenic emissions of CO 2 and 3.4% of the total CO 2 global emissions (Achal et al, 2016;Aprianti, 2017;Miller et al, 2018). Increase in consumption of concrete is a consequence of the susceptibility of infrastructures to physical, chemical and biological factors such as temperature variations, exposure to corrosive and radioactive substances, aggressive gases, natural disasters, and microbial activity (Jroundi et al, 2010;Narayanasamy et al, 2010;Achal et al, 2016;Siddique et al, 2016;Turick and Berry, 2016;Van Tittelboom et al, 2016). These factors cause microcracks formation, which affect mechanical and durability properties of concrete such as compressive strength, flexural strength, and permeability, consequently reducing the useful life of concrete and increasing the cost of the maintenance and repair of infrastructures.…”

Thermal Evolution near Heat-Generating Nuclear Waste Canisters Disposed in Horizontal Drillholes

“…To avoid the complexity of coupled thermal-hydrological-geochemical processes, which are exacerbated if a steam phase evolves, it is recommended that the maximum allowable temperature in the repository be below the boiling temperature curve shown in Figure 2. Note that a lower maximum temperature criterion may be advisable for other reasons, such as expansion and associated thermal stresses [18] or undesirable mineralogical alterations of the buffer material or host rock [7][8][9]. Avoiding steam also improves the corrosion performance of engineered barrier components, particularly that of canister materials.…”

“…The heat then dissipates into the nearby engineered structures and the host formation. Predicting the temperature evolution within the disposal section of the drillhole and the surrounding host rock is necessary as it may alter the properties of the multi-barrier system by accelerating the corrosion of the waste form [2,3] and of metal components comprising the containment systems [4][5][6], by degrading bentonite [7][8][9] or cement [10] used as backfill materials, and by affecting argillaceous host rocks [11,12]. Heat-driven degradation mechanisms may also make the retrievability of the waste canisters more difficult.…”

Overview of nuclear waste treatment and management

“…In order to achieve the above requirements, the cured product should have sufficient resistance to damage. It is easy to transport, store and finalize after curing [4].…”