Nuclear Energy for New Europe 2009

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No: 908

Conference: Nuclear Energy for New Europe 2009

Title: Mathematical Modelling of Transport Pfenomena in Radioactive Waste-Cemement Matrix

Theme: Radioactive Waste Management

Author(s): Ilija Plećaš

Contact : Ilija Plećaš

E-mail: iplecas@vin.bg.ac.yu

Address: VINČA Institute of Nuclear Sciences
11001 Beograd

Country: Serbia

The leaching rate of 137Cs from spent mix bead (anion and cation) exchange resins in a cement-bentonite matrix has been studied. Transport phenomena involved in the leaching of a radioactive material from a cement-bentonite matrix are investigated using three methods based on theoretical equations. These are: the diffusion equation for a plane source an equation for diffusion coupled to a first-order equation and an empirical method employing a polynomial equation. Radioactive waste is waste material containing radioactive chemical elements which does not have a practical purpose. It is often the product of a nuclear process, such as nuclear fission. Waste can also be generated from the processing of fuel for nuclear reactors or nuclear weapons. The main objective in managing and disposing of radioactive (or other) waste is to protect people and the environment. This means isolating or diluting the waste so that the rate or concentration of any radionuclides returned to the biosphere is harmless. Storage as the placement of waste in a nuclear facility where isolation, environmental protection and human control are provided with the intent that the waste will be retrieved at a later time. Disposal as the emplacement of waste in an approved, specified facility (e.g. near surface or geological repository) without the intention of retrieval Typically processing involves reducing the volume of the waste (e.g. by incineration or compaction); solidifying non-solid wastes to make them physically stable, and packaging the waste to isolate it from the environment. Ion exchange resins may be used most successfully for the removal of radioactive and stable ions from dilute solutions. Ion exchange resins are polymers with cross-linking (connections between long carbon chains in a polymer). The resin has active groups in the form of electrically charged sites. At these sites ions of opposite charge are attacted but may be replaced by other ions depending on their relative concentrations and affinities for the sites. Spent mix bead exchange resins containing 60Co and 137Cs, represent a major portion of the solid radioactive waste in nuclear technology. [1,2,3,4,5]
The results presented in this paper are from a 30-year mortar and concrete testing project that will influence the design choices for radioactive waste packaging for a future Serbian radioactive waste disposal center.

Keywords : bentonite, cement , radioactive waste, composite, disposal, diffusion

No:	908
Conference:	Nuclear Energy for New Europe 2009
Title:	Mathematical Modelling of Transport Pfenomena in Radioactive Waste-Cemement Matrix
Theme:	Radioactive Waste Management
Author(s):	Ilija Plećaš
Contact :	Ilija Plećaš
E-mail:	iplecas@vin.bg.ac.yu
Address:	VINČA Institute of Nuclear Sciences 11001 Beograd
Country:	Serbia

The leaching rate of 137Cs from spent mix bead (anion and cation) exchange resins in a cement-bentonite matrix has been studied. Transport phenomena involved in the leaching of a radioactive material from a cement-bentonite matrix are investigated using three methods based on theoretical equations. These are: the diffusion equation for a plane source an equation for diffusion coupled to a first-order equation and an empirical method employing a polynomial equation. Radioactive waste is waste material containing radioactive chemical elements which does not have a practical purpose. It is often the product of a nuclear process, such as nuclear fission. Waste can also be generated from the processing of fuel for nuclear reactors or nuclear weapons. The main objective in managing and disposing of radioactive (or other) waste is to protect people and the environment. This means isolating or diluting the waste so that the rate or concentration of any radionuclides returned to the biosphere is harmless. Storage as the placement of waste in a nuclear facility where isolation, environmental protection and human control are provided with the intent that the waste will be retrieved at a later time. Disposal as the emplacement of waste in an approved, specified facility (e.g. near surface or geological repository) without the intention of retrieval Typically processing involves reducing the volume of the waste (e.g. by incineration or compaction); solidifying non-solid wastes to make them physically stable, and packaging the waste to isolate it from the environment. Ion exchange resins may be used most successfully for the removal of radioactive and stable ions from dilute solutions. Ion exchange resins are polymers with cross-linking (connections between long carbon chains in a polymer). The resin has active groups in the form of electrically charged sites. At these sites ions of opposite charge are attacted but may be replaced by other ions depending on their relative concentrations and affinities for the sites. Spent mix bead exchange resins containing 60Co and 137Cs, represent a major portion of the solid radioactive waste in nuclear technology. [1,2,3,4,5] The results presented in this paper are from a 30-year mortar and concrete testing project that will influence the design choices for radioactive waste packaging for a future Serbian radioactive waste disposal center. Keywords : bentonite, cement , radioactive waste, composite, disposal, diffusion