Experimental and numerical investigations of 99TcO4− diffusion in compacted SPV 200 bentonite

A Statistical Evaluation to Compare and Analyze Estimations of the Diffusion Coefficient of Pertechnetate (99TcO4−) in Compacted Bentonite

“…The samples had an average particle size ranging between 75 and 100 µm and a true density (t) of 2700 kg/m 3 [5,6]. The chemical composition of the simulated underground water (SGW) is listed in previous works [26,27], which comprised typical water samples obtained at a depth of 300-500 m from six boreholes drilled through crystalline rock [2]. The tracer standards were traceable to Packard Spec-ChecTM (Packard Machinery Co, Westford, MA, USA) and NIST SRM 4288A (NIST, Gaithersburg, MD, USA) for HTO and 99 TcO 4 − , respectively.…”

“…In the TD experiments, the daily activity (HTO or Tc concentration) obtained at the outflow reservoir was used as the input data in HYDRUS-1D for the estimation of Da and α under various bentonite densities [27]. HYDRUS-1D, a Microsoft Windowsbased modeling environment, was used to assess efforts to optimize the solute transport parameters of [32][33][34][35][36] in porous media saturated to various degrees.…”

“…However, a significant ambiguity in the choice of the numerical model or simulation often makes an accurate analysis of the diffusion transport difficult. Recently, there have been several numerical analysis or methods used to obtain diffusion parameters, including ANADIFF [19,20], quantum-behaved particle swarm optimization (QPSO) [21,22], fitting for diffusion parameters (FDP) [23,24], the dual period diffusion model (DPDM) [25], and a parameter identification process based on an iterative and analytical method (PIPIAM) [26] etc., and some commercial software programs (i.e., HYDRUS) used for groundwater transport simulations are also convenient tools that can be used to estimate the diffusion coefficients based on the experimental results of TD techniques [27]. In fact, there are always experimental errors and uncertainty associated with each type of numerical analysis or method, so it is necessary to summarize or determine a suitable way to examine radionuclide diffusion behavior.…”

An Improved Speciation Method Combining IC with ICPOES and Its Application to Iodide and Iodate Diffusion Behavior in Compacted Bentonite Clay

“…We developed and verified a precise and reliable apparatus with sandwich-like columns to conduct through-diffusion (TD) experiments, as shown in Figure 1. A similar experimental apparatus has been employed in several past studies [12,20,25]. The MX-80 bentonite sample dimension in thickness and cross-sectional area was 3 mm and 19.6 cm 2 , respectively.…”

“…In addition to transuranic elements (TRU), the possible environmental impact of long-lived radionuclides that exhibit a relatively high mobility under certain geochemical conditions must be taken into consideration when designing an HLW repository. In particular, weakly adsorbed radionuclide anions are the most important, for example 129 I, 99 Tc, and 79 Se [9][10][11][12]. As one of the primary fission products, 129 I is characterized by a long half-life (t 1/2 = 1.57 × 10 7 years), a high fission yield, easy volatilization, easy migration, a high radioactive toxicity, and a high bioavailability.…”