Temperature dependence of apparent thermal conductivity of compacted bentonites as buffer material for high-level radioactive waste repository

Xu, Yunshan; Li, Jingpei; Zeng, Zhaotian; Li, Haibo

doi:10.1016/j.clay.2019.03.017

Cited by 58 publications

(17 citation statements)

References 20 publications

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“…A compilation of 121 measured values for GMZ bentonite from five studies [21][22][23][24][25] and 143 measurements for MX80 bentonite from seven studies [11,15,21,22,[26][27][28] were selected to test the accuracy of seven compacted bentonite thermal conductivity models. The parameters for models such as ZZ2021, LC2016, TC2008, and CZ2015 were fine-tuned for optimal alignment with the measured data.…”

Section: Performance Of Thermal Conductivity Model Of Compacted Bento...mentioning

confidence: 99%

A review and evaluation of thermal conductivity model of compacted bentonite and its mixture

Ye,

Shao,

Chen

2024

IOP Conf. Ser.: Earth Environ. Sci.

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The thermal conductivity of bentonite plays a crucial role in analyzing the heat transfer process and determining the temperature field distribution within deep geological repositories. Despite considerable efforts in modeling the thermal conductivity of compacted bentonite and its mixtures, a comprehensive synthesis of these studies has not been previously undertaken. This research aimed to thoroughly review predictive models for the thermal conductivity of compacted bentonite and its mixtures, assessing their performance against a substantial dataset comprising 495 measurements of GMZ and MX80 bentonite. Through a systematic compilation and evaluation of seven models for compacted bentonite and three models for bentonite mixtures, the study identified TC2008 and LC2016 as the most accurate models for GMZ and MX80 compacted bentonite, respectively, whereas PT2021 emerged as the superior predictor for GMZ and MX80 bentonite mixtures. This exploration revealed the absence of a single, universally accurate model capable of predicting the thermal conductivities across all bentonite variants, highlighting the necessity for researchers to judiciously select the most fitting model for predicting the thermal conductivity of bentonite. Furthermore, we expressed the inherent limitations in current thermal conductivity models for compacted bentonite and its mixtures, and proposed directions for future inquiry in this domain.

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Section: Performance Of Thermal Conductivity Model Of Compacted Bento...mentioning

confidence: 99%

A review and evaluation of thermal conductivity model of compacted bentonite and its mixture

Ye,

Shao,

Chen

2024

IOP Conf. Ser.: Earth Environ. Sci.

View full text Add to dashboard Cite

show abstract

“…The impact of dry density on thermal conductivity, as depicted in figure 4 [14,[16][17][18][19], reveals nearly linear correlations between thermal conductivity and dry density. Nonetheless, these relationships and the corresponding formulas vary with water content, complicating their application in the management of HLW repositories.…”

Section: Dry Densitymentioning

confidence: 99%

“…The impact of saturation degree on the thermal conductivity of various unsaturated bentonite types is portrayed in figure 5, wherein the thermal conductivity increased with the degree of saturation, thereby maintaining a constant dry density [16][17][18][19]. Specifically, thermal conductivity may enhance two to threefold from a dry state to full saturation.…”

Section: Degree Of Saturationmentioning

confidence: 99%

A review on thermal conductivity of unsaturated bentonite

Ye,

Shao,

et al. 2024

IOP Conf. Ser.: Earth Environ. Sci.

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As unsaturated bentonite is used a buffer/backfill material in the construction of engineered barriers for high-level nuclear waste disposal, understanding its thermal properties is crucial for maintaining the operational stability of the repository. This review paper synthesizes research on the thermal conductivity of unsaturated bentonite, encompassing aspects of heat transfer mechanisms, measurement techniques, influencing factors, and prediction models. The results highlight that the transient and steady-state methods have emerged as the predominant techniques for measuring the thermal conductivity of unsaturated bentonite owing to their efficiency and the prevention of water redistribution within the sample throughout the testing phase. Factors such as dry density, degree of saturation, additive content, and temperature were observed to positively influence the thermal conductivity of unsaturated bentonite, whereas an increase in the ion concentration of the pore fluid decreased the thermal conductivity. The prediction models for the thermal conductivity of unsaturated bentonite are categorized into empirical, normalized, and theoretical models. Although empirical and normalized models provide some insight, they suffer from a lack of theoretical foundation, and the parameters they incorporate often lack clear physical significance, complicating their practical application despite their capacity to represent the multifield coupling characteristics of thermal conductivity. The advancements in microscopic testing methods and computational technology herald the potential of mesoscale models and machine learning as formidable tools for predicting the thermal conductivity of unsaturated bentonite, suggesting a promising direction for future research.

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“…These layers have a negative charge balanced by cation exchange, providing the bentonite with most of its physico-chemical properties (Abdullahi and Audu, 2017;García-Romero et al, 2019). Bentonite from multiple locations has been widely studied as a buffer material for DGRs (MX80 from United States, FEBEX from Spain, FoCa from France and GMZ from China, among others; Xu et al, 2019).…”

Section: Bentonite Biogeochemical Transformationsmentioning

confidence: 99%

Impact of microbial processes on the safety of deep geological repositories for radioactive waste

et al. 2023

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To date, the increasing production of radioactive waste due to the extensive use of nuclear power is becoming a global environmental concern for society. For this reason, many countries have been considering the use of deep geological repositories (DGRs) for the safe disposal of this waste in the near future. Several DGR designs have been chemically, physically, and geologically well characterized. However, less is known about the influence of microbial processes for the safety of these disposal systems. The existence of microorganisms in many materials selected for their use as barriers for DGRs, including clay, cementitious materials, or crystalline rocks (e.g., granites), has previously been reported. The role that microbial processes could play in the metal corrosion of canisters containing radioactive waste, the transformation of clay minerals, gas production, and the mobility of the radionuclides characteristic of such residues is well known. Among the radionuclides present in radioactive waste, selenium (Se), uranium (U), and curium (Cm) are of great interest. Se and Cm are common components of the spent nuclear fuel residues, mainly as 79Se isotope (half-life 3.27 × 105 years), 247Cm (half-life: 1.6 × 107 years) and 248Cm (half-life: 3.5 × 106 years) isotopes, respectively. This review presents an up-to-date overview about how microbes occurring in the surroundings of a DGR may influence their safety, with a particular focus on the radionuclide-microbial interactions. Consequently, this paper will provide an exhaustive understanding about the influence of microorganisms in the safety of planned radioactive waste repositories, which in turn might improve their implementation and efficiency.

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Temperature dependence of apparent thermal conductivity of compacted bentonites as buffer material for high-level radioactive waste repository

Cited by 58 publications

References 20 publications

A review and evaluation of thermal conductivity model of compacted bentonite and its mixture

A review and evaluation of thermal conductivity model of compacted bentonite and its mixture

A review on thermal conductivity of unsaturated bentonite

Impact of microbial processes on the safety of deep geological repositories for radioactive waste

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