Effect of Carbonate on the Migration Behavior of Strontium in Compacted Bentonite
- PDF / 593,691 Bytes
- 7 Pages / 432 x 648 pts Page_size
- 79 Downloads / 175 Views
MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.81
Effect of Carbonate on the Migration Behavior of Strontium in Compacted Bentonite Kazuya Idemitsu, Ryota Yamada, Masayuki Hirakawa, Yuki Kakoi, Hajime Arimitsu, Yaohiro Inagaki, Tatsumi Arima Dept. of Applied Quantum Physics and Nuclear Engineering, Kyushu Univ., 744 Motooka, Nishi-ku, Fukuoka, Japan
ABSTRACT 㻌
The apparent diffusion coefficients of strontium in compacted bentonites were investigated at various concentrations of NaHCO3. Purified sodium bentonite Kunipia-F® was compacted with a jig into cylindrical pellets 10 mm in diameter and 10 mm high with dry densities of 1.0 to 1.6 Mg/m3. Each bentonite pellet was inserted into an acrylic resin column and saturated with carbonated water containing 0.1 to 1.0 M NaHCO3 for more than 1 month. The face of the bentonite specimen was spiked with 5 μL of 1.0 M SrCl2 tracer solution. After a few weeks, the strontium diffusion profiles were measured by inductively coupled plasma-mass spectrometry. The apparent diffusion coefficients of strontium decreased slightly with increasing dry density. NaHCO3 concentrations of 0.5 M decreased the apparent diffusion coefficients of strontium by half at a dry density of 1.0 Mg/m3 and quarter at 1.6 Mg/m3. At a higher NaHCO3 concentration of 1.0 M, no strontium diffusion profile was observed, whereas white precipitate was observed on the face of the bentonite specimen where it was spiked with strontium. This white precipitate could be strontianite, which is strontium carbonate. Diffusion experiments using cesium were carried out for comparison, and the presence of carbonate had no effect on the apparent diffusion coefficient.
INTRODUCTION To assess the safety of geological disposal of high-level radioactive waste and spent nuclear fuel in Japan [1], it is critical to understand the barrier function of the bentonite buffer and carbon steel overpack that forms the multi-barrier system. The transport of radionuclides in compacted bentonite is mainly controlled by diffusion, and thus it is important to determine the diffusion coefficients of these radionuclides.
1021
Downloaded from https://www.cambridge.org/core. Rice University, on 16 May 2020 at 11:02:04, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2019.81
Strontium forms a divalent cation that has strong affinity with carbonate ions and generates a positively charged bicarbonate complex, a neutral carbonate complex, and a strontianite precipitate depending on the carbonate concentration [2]. ܵ ݎଶା ܱܥܪଷି ֞ ܱܵܥܪݎଷା ǡ ܭௌுைయశ ൌ ܵ ݎଶା ܱܥଷଶି ֞ ܱܵܥݎଷ ǡ ܭௌைయబ ൌ
ሾௌுைయశ ሿ
ሾௌ మశ ሿሾுைయష ሿ
ሾௌைయబ ሿ
ሾௌ మశ ሿሾைయమష ሿ
ൌ ͳǤͳͺͶ,
ൌ ʹǤͺͲͷ,
ܵ ݎଶା ܱܥଷଶି ֞ ܱܵܥݎଷ ሺܿݎሻǡ ܭௌ௧௧௧ ൌ ሾܵ ݎଶା ሿሾܱܥଷଶି ሿ ൌ െͻǤʹͳ.
(1) (2) (3)
These complexes are expected to show different migration behavior in compacted bentonite because the size and charge of the comple
Data Loading...
