Sorption Behavior of Radionuclides on Calcium-Leached Mortar

2000 ◽  
Vol 663 ◽  
Author(s):  
Nobuo Ashikawa ◽  
Takatoshi Tajima ◽  
Hiroshi Saito ◽  
Ai Fujiwara
Keyword(s):  
Radioactive Waste ◽  
Safety Assessment ◽  
Electrical Potential ◽  
Potential Gradient ◽  
Extended Period ◽  
Distribution Coefficients ◽  
Sorption Behavior ◽  
Degradation Degree ◽  
The Relationship ◽  
Low Level Radioactive Waste

ABSTRACTLow-level radioactive waste (LLRW) is disposed of by shallow land burial. Reinforced concrete is used as the radioactive waste repository. However, the concrete structure is in contact with water and will gradually degrade over an extended period of time due to leaching.It is important to investigate the interaction between radionuclides and degraded concrete in the safety assessment of nuclear waste disposal. The authors measured the distribution coefficients (Kd) of various radionuclides for calcium-leached mortars. The calcium-leached mortars were prepared by an accelerated leaching test for mortar based on the electrical potential gradient. These degraded conditions are similar to that of degraded concrete in contact with water for a long period of time. The degradation degree of calcium-leached mortar is evaluated by the CaO/SiO2 molarratio (Ca/Si ratio) of calcium silicate hydrate (C-S-H).As a result, the relationship between Kd and the Ca/Si ratio in C-S-H can be roughly grouped into the following three types:1.137Cs and 85Sr – Kd decreases with an increase in the Ca/Si ratio.2. 95mTc and 110mAg – There is no correlation between Kd and the Ca/Si ratio.3. 14C, 241Am and 125I – Kd increases with an increase in the Ca/Si ratio.

Sorption Behavior of Nickel and Palladium in the Presence of NH3(aq)/NH4+

2013 ◽  
Vol 1518 ◽  
pp. 231-236
Author(s):  
Taishi Kobayashi ◽  
Takayuki Sasaki ◽  
Ken-you Ueda ◽  
Akira Kitamura
Keyword(s):  
Thermodynamic Data ◽  
Safety Assessment ◽  
Sorption Behavior ◽  
Ammine Complexes ◽  
Surface Complexation Model ◽  
Nuclear Reprocessing ◽  
D Values ◽  
The Impact ◽  
Pumice Tuff ◽  
Low Level Radioactive Waste

ABSTRACTIt is necessary to assess the impact of nitrate salts and their reduction products (e.g. NH3(aq)/NH4+) contained in low-level radioactive waste generated from nuclear reprocessing process for the safety assessment of geological disposal of the waste. In the present study, sorption behavior of Ni and Pd on pumice tuff was investigated in the presence of NH3(aq)/NH4+. Under various NH3(aq)/NH4+ concentration, pH and ionic strength conditions, distribution coefficient (Kd) of Ni and Pd on pumice tuff was determined by a batch experiment. For Ni system, the Kd values showed no significant dependence on initial NH4+ concentration ([NH4+]ini < 1 M) in neutral pH region, which agreed with the prediction from thermodynamic data. For Pd system, the Kd values decreased with an increase of [NH4+]ini, suggesting the formation of stable ammine complexes (Pd(NH3)m2+ (m: 1 – 4)). The obtained Kd values for Ni and Pd were analyzed using a surface complexation model. By taking complexes predicted by thermodynamic data into account, sorption behavior of Ni and Pd in the presence of NH3(aq)/NH4+ were well explained.

Comparative study of cesium sorption on crushed and intact sedimentary rock

2006 ◽  
Vol 94 (9-11) ◽  
Author(s):  
Xiaobin Xia ◽  
Kazuki Iijima ◽  
Gento Kamei ◽  
M. Shibata
Keyword(s):  
Radioactive Waste ◽  
Sedimentary Rock ◽  
Safety Assessment ◽  
Distribution Coefficients ◽  
Assessment Methodology ◽  
Sorption Data ◽  
Geological Disposal ◽  
Cesium Sorption ◽  
Sorption Method ◽  
High Level

For establishing a reliable safety assessment methodology for high-level radioactive waste (HLW) geological disposal, it is essential to clarify the applicability of sorption data determined with a conventional batch sorption method to an actual repository environment. In the present study, sorption data represented as distribution coefficients (

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