Diffusion characteristics of HTO and 99TcO_4^- in compacted Gaomiaozi(GMZ) bentonite  

作　　者：Tsuey-Lin Tsai Shih-Chin Tsai Yu-Hung Shih Liang-Cheng Chen Chuan-Pin Lee Te-Yen Su 

机构地区：[1]Chemistry Division, Institute of Nuclear Energy Research,No. 1000, Wenhua Rd., Jiaan Village, Longtan District,Taoyuan, China [2]Nuclear Science and Technology Development Center,National Tsing Hua University, Hsinchu, China [3]Department of Earth Sciences, National Cheng Kung University, No. 1, University Road, Tainan, China

出　　处：《Nuclear Science and Techniques》2017年第5期60-67,共8页核技术（英文）

基　　金：the Nuclear Backend Management Department at Taiwan Power Company for financially supporting this research

摘　　要：The characteristics of diffusion are essential to the transport of radionuclides through buffer/backfill materials, such as bentonite, which are commonly found in waste repositories. This study used through-diffusion techniques to investigate the diffusion behavior of HTO and ^(99)TcO_4^- on GMZ bentonite of various densities. Diffusion rates were calculated by measuring the diffusion coefficients(De, Da), plotting breakthrough curves and interpreting experiment data. The apparent and effective diffusion coefficients of HTO ranged from(1.68 ± 0.40) 9 × 10^(-11) to(2.80 ± 0.62) 9 × 10^(-11) m^2/s and from(4.61 ±1.28) 9 × 10^(-12) to (16.2 ± 2.50) 9 × 10^(-12) m^2/s, respectively.The apparent and effective diffusion coefficients of^(99)TcO_4^-ranged from(5.26 ± 0.16) 9 × 10^-12to(7.78 ± 0.43) 9× 10^-12m^2/s and from(1.49 ± 0.002) 9 × 10^(-12) to(4.16 ±0.07) 9 × 10^(-12) m^2/s, respectively. The distribution coefficients of HTO and^(99)TcO_4^-ranged from(0.70 ± 0.12) 9× 10^(-2) to(1.36 ± 0.53) 9 × 10^(-2) mL/g and from(1.12 ±0.06) 9 × 10^(-2) to(5.79 ± 2.22) 9 × 10^(-2) mL/g, respectively.The Deand Kdvalues were shown to decrease with an increase in the bulk dry density of compacted bentonite. Our results show that HTO and ^(99)Tc could be considered nonsorbent radionuclides. The data obtained in this studyprovide a valuable reference for the safety assessment of waste repositories.The characteristics of diffusion are essential to the transport of radionuclides through buffer/backfill materials, such as bentonite, which are commonly found in waste repositories. This study used through-diffusion techniques to investigate the diffusion behavior of HTO and ⁹⁹TcO₄ ⁻ on GMZ bentonite of various densities. Diffusion rates were calculated by measuring the diffusion coefficients (D _e, D _a), plotting breakthrough curves and interpreting experiment data. The apparent and effective diffusion coefficients of HTO ranged from (1.68 ± 0.40) × 10⁻¹¹ to (2.80 ± 0.62) × 10⁻¹¹ m²/s and from (4.61 ± 1.28) × 10⁻¹² to (16.2 ± 2.50) × 10⁻¹² m²/s, respectively. The apparent and effective diffusion coefficients of ⁹⁹TcO₄ ⁻ ranged from (5.26 ± 0.16) × 10⁻¹² to (7.78 ± 0.43) × 10⁻¹² m²/s and from (1.49 ± 0.002) × 10⁻¹² to (4.16 ± 0.07) × 10⁻¹² m²/s, respectively. The distribution coefficients of HTO and ⁹⁹TcO₄ ⁻ ranged from (0.70 ± 0.12) × 10⁻² to (1.36 ± 0.53) × 10⁻² mL/g and from (1.12 ± 0.06) × 10⁻² to (5.79 ± 2.22) × 10⁻² mL/g, respectively. The D _e and K _d values were shown to decrease with an increase in the bulk dry density of compacted bentonite. Our results show that HTO and ⁹⁹Tc could be considered non-sorbent radionuclides. The data obtained in this study provide a valuable reference for the safety assessment of waste repositories.

关 键 词：Distribution COEFFICIENT Apparent DIFFUSION COEFFICIENT Effective DIFFUSION COEFFICIENT COMPACTED BENTONITE Through-diffusion 

分 类 号：TL941[核科学技术—辐射防护及环境保护]