NEW TRENDS IN THE RAD WASTE

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New Trends in Utilizing Chemi-Sorbents
in Radioactive Liquid Waste Treatment

• Ahmed Mohamed El-Kamash
• Hot Laboratories and Waste Management Center
• Atomic Energy Authority

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ABSTRACT

• This review presents in brief the radioactive
  waste management system and provides an overview
  on the technical options available for the
  treatment of these wastes.
• The sorption technique, as one of the most widely
  used techniques for the treatment of liquid
  radioactive wastes will be presented.
• The progress in utilizing chemi-sorbents in
  radioactive liquid waste treatment will be
  highlighted.

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CONTENTS

• Radioactive waste management
• Utilization of sorption in Radioactive waste
  treatment
• New trends for utilizing chemi-sorbents in liquid
  radioactive waste treatment
• Authors contributions

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Radioactive wastes

• Radioactive waste generally consists of a mixture
  of discarded materials or components arising from
  the production or use of radioactive material

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Nuclear Fuel Cycle
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Objective of RWM Policy

• To collect, handle, treat, condition, store,
  transport, and dispose RW in a manner that
  protects the human and the environment without
  imposing undue burden on future generation.

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Principles of RWM Policy

• Establishing a national legal framework,
• Control of radioactive waste generation,
• Safety of facilities,
• Waste generator pays,
• Sound decision-making based on scientific
  information,
• Risk analysis and optimization of resources,
• International cooperation

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Classification of RW The IAEA has suggested the
following classification system based upon
specific activity
Category Activity (m-3) Mixed ?/? emitters Remarks
1 lt 37 KBq No treatment required released after measuring
Low-Level 2 37 KBq to 3.7 MBq Treated, no shielding required
3 3.7 MBq to 3.7 GBq Treated, shielding sometimes required according to radionuclide composition
Intermediate-Level 4 3.7 GBq to 370 TBq Treated, shielding necessary in all cases
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Activities in RWM System
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Treatment
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    Selection of Treatment System

• Selection of a liquid waste treatment
  system involves a set of decisions related to the
  following factors. 
• Characterization of arising waste,
• Discharge requirements for
  decontaminates,
• Available technologies and their costs,
• Conditioning of the concentrates, and
• Storage and disposal of conditioned
  concentrates

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Treatment of liquid wastes

• The processes commonly used for treatment of
  liquid radioactive wastes fall generally into
  three main categories 
• Chemical precipitation,
• Sorption/ Ion exchange, and
• Evaporation.

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Treatment of Aqueous waste
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Sorption
Physical sorption. no exchange of electrons
occur, rather intermolecular attractions occur
between valency happy sites and are therefore
independent of the electronic properties of the
molecules involved. Chemical sorption. Chemical
adsorption, or chemisorption, involves an
exchange of electrons between specific surface
sites and solute molecules, which results in the
formation of a chemical bond. Electrostatic
sorption (ion exchange). This is a term reserved
for coulombic attractive forces between ions and
charged functional groups and is more commonly
classified as ion exchange. In addition to being
ion exchangers, ion exchange materials can also
act as chemi-sorbents..
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Theory of Sorption

• Sorption equilibrium
• Sorption kinetics and dynamics
• Thermodynamic considerations

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Sorption equilibrium

• Sorption isotherm is the fundamental concept in
  sorption science that is considered as the
  primary source of information on the sorption
  process.
• It is defined as the equilibrium relation between
  the quantity of the sorbed material and the
  concentration in the bulk fluid phase at constant
  temperature and pH.

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Sorption equilibrium modeling

• Large numbers of simplified equations have been
  developed to study the sorption isotherm. These
  equations based on experimental data under
  certain conditions would probably serve best the
  purpose of equilibrium modeling and in a further
  step of a commercial-scale operation design.
• The most common cases for liquid phase sorption
  systems are the Langmuir and Freundlich isotherms
  that are used to give insight on the sorption
  nature and mechanism.

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• Sorption kinetics and dynamics
• The sorption dynamics studies describe the solute
  uptake rate and evidently this rate controls the
  residence time of sorbate uptake at the
  solid/solution interface.
• The data of the kinetics of different ions sorbed
  into sorbents can be analyzed using
• Pseudo-first order rate model
• Pseudo-second order rate model
• Homogeneous particle diffusion model

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Thermodynamic considerations In order to gain
insight into the thermo-dynamic nature of the
sorption process, several thermodynamic
parameters for the sorption system should be
calculated
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Sorbent materials

• Sorbents can be divided into two large
  categories
• Those that have hydrophobic properties and
  therefore adsorb the molecules dissolved in the
  solution in contact with the sorbent,
• Those that eliminate solutes by chemical
  affinity
• A wide range of materials is available for the
  sorption treatment of radioactive liquids

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• Natural inorganic sorbents
• Clays (bentonite and kaolinite), vermiculite and
  zeolites ( chabazite and clinoptilolite)
• Disadvantages
• Low sorption capacities
• Low abrasion resistance and mechanical
  durability
• Non-controllable pore size
• Peptization
• Decomposed in acids or alkalis

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• Natural organic sorbents
• Polysaccharides (cellulose and algic acid),
  proteins (keratin and collagen) and carbonaceous
  (charcoals and, lignites)
• Disadvantages
• Swelling and tendency to peptize,
• Limited radiation stability
• Weak physical structures,
• Non-uniform physical properties,
• Non-selective,
• Unstable outside a moderately neutral pH range

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• Synthetic sorbents
• Zeolites
• Zeolites are crystalline aluminosilicate based
  materials
• Advantages of synthetic zeolites
• Can be engineered with a wide variety of
  chemical properties and pore sizes, and
• Stable at higher temperatures.

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• Limitations of synthetic zeolites
• They have a relatively high cost compared with
  natural zeolites
• They have a limited chemical stability at extreme
  pH ranges
• The materials tend to be brittle, which limits
  their mechanical stability.

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Silicotitanates
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• Synthetic organic sorbents
• Advantages
• High capacity,
• Wide applicability, and
• Low cost.
• Limitations
• Limited radiation and thermal stabilities.

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• Composite materials
• Consist of one or more sorbents combined with
  another material, which can be inorganic or
  organic and may itself be a sorbent
• The reason for manufacturing a composite material
  is to produce a granular material, with
  sufficient strength for column use, from sorbents
  that do not form, or only form weak, granules
  themselves

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• PAN is inorganic ion exchanger-modified
  polyacrylonitrile binding matrix,
• Its beads are highly porous and can accommodate
  very high loadings of ion exchange material
  (595)
• PAN advantage
• Improved kinetics and sorbent capacity
• Easy modification of physico-chemical properties
  (hydrophilicity, porosity, mechanical strength)
• Simplified production.

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• Chelating resins
• The chelating groups are either impregnated into
  the pores of the solid polymeric matrix of the
  resin or covalently bonded to the polymeric
  surface.
• Advantages of inorganic supports
• Good selectivity,
• No swelling,
• Rapid sorption of metal ions, and
• Good mechanical stability.

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• Nano-sized magnetic materials
• Nano-sized magnetic chemi -sorbents can be
  promising candidate materials for treatment of
  low-level effluents resulting in effective
  decontamination and very high volume reduction of
  radioactive wastes. These sorbents also enhance
  the kinetics of radionuclide separation from
  liquid radioactive wastes

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• Fiber chemi-sorbents materials
• Fiber chemi-sorbents materials are new class of
  chemi-sorbents consist of a polymer matrix with
  active ion-exchange groups and a fiber filter
  with reactive groups.
• Manufactured by poly condensation filling in a
  small number of stages, these materials have
  stable physico-mechanical and sorption properties
  in preliminary preparation and treatment of
  liquid media

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• Solvent impregnated resins (SIR )
• Solvent impregnated resins are relatively new
  types of ion selective exchanger based on the
  solvent extraction.
• These reagents have some potential advantages
  over solvent extraction due to their high
  selectivity and ease of handling.

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• Ion exchange membrane
• Various membrane separation processes have been
  developed and utilized in the field of potable
  water purification and more recently in the
  treatment of various process and waste liquors
• There are two types of ion- exchange membranes
• Heterogeneous
• Homogeneous.

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Authors contributions

• Natural inorganic sorbents
• Thermodynamics of Radio Strontium Exchange with
  Certain Zeolites, HAWA98, Cairo (Egypt)1998.
• Prediction of Ion-Exchange Equilibria in Binary
  Aqueous System, J. Radiochem. Acta 1999.
• Simulation of Zeolite Fixed Bed Columns Used for
  Treatment of Liquid Radioactive Wastes ,
  J. Radiochem. Acta 2000.
• Prediction of Multicomponent Ion-Exchange
  Equilibria for a Ternary System from Data of
  Binary Systems, J. Sep. Sci. Technol. 2000.

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• Numerical Simulation of Multicomponent Ion
  Exchange Radwaste Treatment in Fixed- Bed Columns
  RETBE 2000.
• Diffusion Kinetics of Some Radioactive Ions
  Adsorbed onto Local Clay Soils. Arab J. of Nuc.
  Sci. Appl. 2003.
• Thermodynamic and Kinetic Studies for the Removal
  of Radio-Europium Ions from Waste Solution Using
  Some Local Clay Minerals
• Sorption Potential of Bentonite and Sandstone for
  Removal of 137Cs and 60Co Radionuclides from
  Radioactive Waste Solutions Arab J. of Nuc. Sci.
  Appl. 2007.

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• Synthetic inorganic sorbents
• Thermodynamics of Zinc and Cadmium Ions Removal
  from Waste Solutions Using Zeolite A, Arab J. of
  Nucl. Sci. Appl.2003.
• Kinetics Studies on the Removal of Cesium and
  Strontium Ions From Aqueous Solutions Using
  Prepared Zeolite Arab J. of Nucl. Sci. Appl.
  2005.
• Modeling Batch Kinetics and Thermodynamics of
  Zinc and Cadmium Ions Removal from Waste Solution
  Using Synthetic Zeolite A J. Haz. Mat. 2005.
• Thermodynamic Modeling for the Removal of Cs,
  Sr2, Ca2, and Mg2 Ions from Aqueous Waste
  Solution Using Zeolite A, J. Radioanal. Nuc.
  Chem. 2006.

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• Effect of Temperature on the Removal of Cesium
  and Strontium Ions from Aqueous Solutions
  Using Zeolite A, ZAGAZIG Conf. 2006.
• Evaluation of Zeolite A for the Sorptive Removal
  of Cs and Sr2 Ions from Aqueous Solutions Using
  Batch and Fixed Bed Column Operations J. Haz.
  Mat. 2007
• Preparation and Evaluation of Cerium (IV)
  Tungstate Powder as Inorganic Exchanger in
  Sorption of Cobalt and Europium Ions from Aqueous
  Solutions J. Haz. Mat. 2007.
• Two-Step Method for Preparation of NaA-X Zeolite
  Blend from Fly Ash for Removal of Cesium ions J.
  Haz. Mat. 2007.

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• Solvent impregnated resins
• Thermodynamics of Uranium Extraction from Nitric
  Acid Solution by TBP Loaded on Inert Supporting
  Material, J. Radioanal. Nuc. Chem. 2002
• Modeling of Uranium Extraction Chromatography
  from Nitric Acid Solution Using TBP Impregnated
  Resin, Arab J. of Nucl. Sci. Appl.2003.
• Sorption of Uranium and Thorium Ions from Nitric
  Acid Solution Using HDEHP-Impregnated Activated
  Carbon, Arab J. of Nucl. Sci. Appl. 2005.
• Kinetics and Thermodynamics Studies of the
  Sorption of Uranium and Thorium Ions from Nitric
  Acid Solution Onto a TBP Impregnated Sorbent, J.
  Radioanal. Nuc. Chem. 2006

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• Planning and design improvements for RWM system
• Modeling and Validation of Radionuclides Releases
  from an Engineered Disposal Facility. J. of Rad.
  Waste Manag. Environ. Res.2002.
• Planning Closure Safety Assessment for the
  Egyptian Near Surface Disposal Facility, IAEA
  Conf. Japan 2005.
• Disposal A Last Step towards an Integrated Waste
  Management System in Egypt, IAEA Conf. Japan
  2005.
• Planning for a Solid Waste Management Quality
  Assurance Program in Egypt, Qual. Assu. J. 2007
• Design of a Decouplar Controller for Forced
  Circulation Evaporator Used in a Radioactive
  Waste Treatment Plant, Minia International
  Conference 2005
• Design of an Effective Level Controller System
  for Forced Circulation Evaporator Used in a
  Radioactive Waste Treatment Plant, RETBE 2006.

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• Leaching Kinetics of 137Cs and 60Co Radionuclides
  Fixed in Cement and Cement- Based Materials J.
  Cem. Conc. Res. 2002.
• Immobilization of Cesium and Strontium
  Radionuclides in Zeolite-Cement Blends, J. Haz.
  Mat. 2006.
• Modeling the Long-Term Leaching Behavior of
  137Cs, 60Co, and 152-154Eu Radionuclides from
  Cement-Clay Matrices, J. Haz. Mat. 2007.
• Leaching Behavior of 137Cs and 60Co Radionuclides
  from Stabilized Waste Matrices, Int. J. of Phys.
  Sci. 2007.

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Thank you