2) Diffusion coefficients (D
a&De) ：Sr
Retardation behavior of Sr and Cs in Crushed and Intact Rocks：
Two potential LLW repository Taiwan host rocks
Ming-Chee Wu
1 ,*, Chuan-Pin Lee
1, Ching-Yuan Liu
2, Tsuey-Lin Tsai
31,*Department of Earth Sciences, National Cheng Kung University, Tainan ,Taiwan
2 Department of Chemical and Materials Engineering, National Central University, Taoyuan, Taiwan 3 Chemical Division, Institute of Nuclear Energy Research, Taoyuan, Taiwan
The “
multi-barrier”concept has been adopted to deal with issues related to
nuclear waste repository, such as the use of clays as a buffer/backfill material
because of their high sorption capacities.
This study investigates sorption and diffusion of Strontium (Sr) and Cesium (Cs)
in two potential host rocks (granite from Kinmen Island and basalt from Penghu
Island) by using batch and through-diffusion methods in order to establish a
reliable safety assessment methodology. The purpose of this study is to determine
whether it is possible to compare K
dvalues determined by the batch and static
diffusion methods.
Introdection
Introdection
Experiments
A
A
pparatus
pparatus
Polar microscopy &Autoradiography
Polar microscopy &Autoradiography
1) Basalt Cs
2) Granite Cs
Results and discussion
Results and discussion
Batch
Batch
& Column Comparison
& Column Comparison
Conclusions
Conclusions
The distribution coefficient (Kd) of Sr and Cs in various concentrations
(~10−2–10−7 M) obtained from batch tests indicated a higher sorption
capacity in basalt than that in granite because of the 10% Fe–Mg mineral content.
The diffusion of Sr and Cs both in crushed granite and basalt reach steady state after 110 days and apparent diffusion coefficient (Da) were
3.29×10-11m2/s (for Sr in crushed granite), 4.17×10-12m2/s (for Sr in
crushed basalt), 2.86×10-11m2/s (for Cs in crushed granite), 1.82×10-12
m2/s (for Cs in crushed basalt), respectively.
It showed that major retardation of Sr and Cs depended on the microporous structure of tested media, such as decreases of constrictivity (δ) and increases of tortuosity (τ).
In fact, the solid/liquid (S/L) ratio decreased as is the case when switching from batch to column experiments and the sorption effect on minerals became even more negligible in retardation of radionuclide migration.
Cs > Sr Basalt >Granite
The
The88th International Conference onth International Conference onNuclear andNuclear andRadiochemistryRadiochemistry（（NRC 8NRC 8））
No.66
Penghu
Kinmen
Materials
Materials
G or B
shaking
An aqueous solution (30 mL ) containing Sr (or Cs) in thepresence of 10-2~ 10-7M was
contacted with 1 g of rock at 25±1ºC for 14 d.
1) Batch Method（
ASTM D4319-83）
2) Column Diffusion （
Crank. J, 1975）
Liquid remove in the
source cell (C0)
Liquid remove in the diffusion cell (C)
L
3) Basalt Sr
4) Granite Sr
C (M)
1e-8 1e-7 1e-6 1e-5 1e-4 1e-3 1e-2 1e-1
K d (m L /g ) 0.1 1 10 100 1000 10000 50~100mesh B 50~100mesh G 200~270mesh B 200~270mesh G <50 mesh B <50mesh G (b) Cs C (M)
1e-8 1e-7 1e-6 1e-5 1e-4 1e-3 1e-2 1e-1
K d (m L /g ) 0.1 1 10 100 1000 10000 50~100mesh B 50~100mesh G 200~270mesh B 200~270mesh G <50mesh B <50mesh G
1) Distribution Coefficients (K
d) ：Sr and Cs
Time (d) 0 20 40 60 80 100 120 Σ C /C o 0.0 0.1 0.2 0.3 0.4 0.5 Granite Basalt yG= 0.0019x - 0.001 R-square = 0.99 yB= 0.0012x - 0.005 R-square = 0.99 (a) 0.45 N.A 4.52 35.7 td 12.1 N.A 2.00 0.32 Kd 59.9 N.A 10.7 2.6 Rf 1.10 N.A 1.65 2.62 2D e×10−11(m2/s) 0.05 N.A 0.42 3.29 1D a×10−11(m2/s) Basalt Granite Basalt Granite
Intact
Crushed
Parameters
Time (d) 0 20 40 60 80 100 120 140 160 Σ C /C o 0.0 0.1 0.2 0.3 0.4 0.5 Granite Basalt yB= 0.0008x - 0.0279 R-square = 0.99 (b) Time(d) 0 20 40 60 80 100 120 140 160 Σ C /C o 0.0 0.1 0.2 0.3 0.4 0.5 Crushed Granite Crushed Basalt Intact Granite Intact Basalt (c) 59.9 N.A 689.9–1193.8 119.6–1485Rf
12.1 N.A 13.63–23.60 0.96–12.03K
dIntact (B)
Intact (G)
Basalt
Granite
Diffusion
Batch
Item
Kd （Batch）> Kd(Column) ；Kd （Intact）> Kd(Crush) 10.7 2.60 67.30–115.8 6.57–70.85
