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Adsorption of Carbon-14 on Mortar

Published online by Cambridge University Press:  15 February 2011

Junko Matsumoto ,
Tsunetaka Banba  and
Susumu Muraoka
Junko Matsumoto
Affiliation:
Department of Environmental Safety Research, Japan Atomic Energy Research Institute, To-kai, Ibaraki 319–11, Japan.
Tsunetaka Banba
Affiliation:
Department of Environmental Safety Research, Japan Atomic Energy Research Institute, To-kai, Ibaraki 319–11, Japan.
Susumu Muraoka
Affiliation:
Department of Environmental Safety Research, Japan Atomic Energy Research Institute, To-kai, Ibaraki 319–11, Japan.
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Abstract

The sorption experiments of carbon-14 on the mortar grain (grain size : 0.50 – 1.0 mm) focused on the chemical form of the carbon-14 were carried out by the batch method. Three kinds of carbon-14 chemical form were used for the experiments : sodium carbonate (Na214CO3) as the inorganic radiocarbon, and sodium acetate (CH314COONa) and acetaldehyde (14CH314CHO) as the organic radiocarbons. 0.30 gram samples of mortar were soaked in the solution with carbon-14 at 15°C for periods of up to 160 days. At the end of each run, carbon-14 concentrations in the supernatants were determined before and after centrifugation (3,500 rpm., 1 hr.).

In the mortar-sodium carbonate system, the retention process of carbon-14 related to reaction on the surface of the mortar was speculated as follows. First, 3CaO-SiO2. and 2CaO-SiO2, of the mortar components contact with water and produce Ca(OH)2. Ca(OH)2 produces Ca2+ and OH− in the solution. Then, calcite forms from Ca2+ and CO32− in the solution. Thus, the sorption ratio of carbon-14 onto mortar will be high until mortar nas been completely carbonated because Ca2+ is rich in the mortar and the solubility of calcite is low.

In the mortar-organic carbon system, the soluble organic carbon-14 is hardly sorbed on the surface of the mortar. Therefore, the cementitious materials may not inhibit the release of organic radiocarbons from the low-level radioactive wastes, contrary to the case of inorganic radiocarbon.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 353: Symposium – Scientific Basis for Nuclear Waste Management XVIII , 1994 , 1029
Copyright
Copyright © Materials Research Society 1995

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References

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