Radioactive Liquid Waste Treatment Research Articles

Inorganic Sorbent for Selective Treatment of Liquid Radioactive Wastes

Physicochemical characteristics of Termoksid-35 inorganic sorbent are given and its performance as a sorbent for radiocesium is studied. Termoksid-35 demonstrates high selectivity for radiocesium even in highly saline neutral and alkaline solutions, allowing its application to selective treatment of liquid radioactive wastes.

Application of Chitin and Zeolite adsorbents for treatment of low level radioactive liquid wastes

Two types of Shrimp Chitin derivatives and two types of Iranian natural Zeolite derivatives (Firuzkooh Clinoptiliolite) were studied for adsorption and treatment of low-level radioactive liquid waste (LLW). Chitin with lowers than 10% and Chtiosan with higher than 90% deacetylation factor were selected as natural organic adsorbents. Natural Cliniptilolite of Firuzkooh area and Na form derivatives of it were selected as natural inorganic adsorbents. The static and dynamic ion exchange experimental results show that the adadsorption efficiency depend on particle size, PH, adsorbent type, deacetylation factor (in Chitin adsorbents) and cation type. The best Cs adsorption occurred in Na form Clinoptilolite. Nevertheless Chitin derivatives, particularly Chitosan, are more efficient than Zeolite adsorbents for removing of radionuclides such as 137Cs, 54Mn, 90Sr and 60Co. Adsorption performance was discussed and compared with each other.

Globule formation of a clay mineral and a rapid method for the treatment of liquid radioactive waste

Summary A technique has been proposed for the grain formation of a naturally available clay mineral (inorganic sorbent). The clay mineral was processed to form the globules to ease the decontamination of low and intermediate levels of liquid radioactive wastes. The purpose of this study is to develop a new form of inorganic sorbing material in the form of beads for the treatment of liquid radioactive waste originating from different types of nuclear installations. This material in the form of spherical beads can also be used for the immobilization of secondary waste that results as a byproduct from processing of nuclear wastes. As it is a major radiotoxic nuclide present in the nuclear wastes, the sorption of cesium from the low level liquid radioactive waste has been described. The potential utilization of this porous clay as an inexpensive material for the final disposal of radioactive wastes has been suggested.

Trace perchlorates in a radiological liquid-waste treatment facility

Waste management programs at the Radioactive Liquid Waste Treatment Facility (RLWTF) at the Los Alamos National Laboratory (LANL) are concerned with the levels of perchlorates due to the effects it can have on the environment and resultant regulations. The RLWTF treats industrial and radioactive wastes generated at multiple research and production facilities across the LANL. Perchloric acid is the major source of the perchlorate ion in the RLWTF used in the analytical chemistry laboratories and for metal dissolution. Perchlorate is present in the influent to the RLWTF at concentrations up to several thousands μg/l level. Ion chromatography is the method of choice to analyze the concentrations of perchlorate in the wastewater generated at the RLWTF. Perchlorate was separated by elution through a CS16/CG16 with an EG40 eluent generator. To minimize background conductivity and enhance analyte conductance, an anion self-regenerating suppressor was used. The method achieved a perchlorate method detection limit of 1 μg/l. The method is successfully being used to monitor the perchlorate levels at the RLWTF and provide data for the pilot tests to remove perchlorate from the RLWTF effluent.

Composite CFC-PU foam ion exchanger in the removal of radioactive cesium

The potential use of copper ferrocyanide - polyurethene foam (CFC-PU foam) developed in our laboratory was investigated in the treatment of radioactive liquid waste for the removal of cesium. The pilot plant scale studies were carried out so that these studies can be further extended to the plant scale operations. Decontamination factors obtained were found to be function of total dissolved solids. A correlation studies on results obtained from pilot plant and laboratory scale were made and observed that they are in good agreement with each other.

Physicochemical Reasons for the Use of TiOHPO4 for Treatment of Liquid Radioactive Waste

Heterogeneous exchange of the proton of hydrated titanyl hydrogen phosphate with Li, Na, K, Rb, and Cs cations in aqueous solutions was studied potentiometrically. The sorption equations were proposed. The concentration and thermodynamic equilibrium constants were calculated. The optimal pH range of the solution providing effective sorption of radioactive cesium on hydrated titanyl hydrogen phosphate was determined. The decrease in the efficiency of radiocesium sorption from liquid waste with a high content of competing nonradioactive alkali metal cations is due to a decrease in the pH of this solution in the course of the sorption. To provide efficient sorption removal of radiocesium, the pH should be maintained in the range 4-7, or the sodium form of the sorbent should be used. The selectivity of radiocesium sorption on TiOHPO4 in the presence of excess sodium cation was estimated.

Sorption of Cesium on Titanium and Zirconium Phosphates

Titanium and zirconium phosphates were prepared from the mineral raw materials of the Kola Peninsula. Their capability to recover cesium cations from the model solutions and liquid radioactive waste (LRW) was studied. Titanium phosphate prepared from solutions formed by titanite breakdown exhibits greater distribution coefficients of cesium as compared to zirconium phosphate. Titanium phosphate, as being cheaper and possessing greater sorption capacity, was recommended for treatment of LRW to remove cesium.

A comparison of the acidity and the complexing ability of ( o-hydroxyphenyl) bis- and ( o-hydroxyphenyl) mono-methylenephosphonic acids towards lanthanide(III) ions

The characterization of the acid–base properties of a family of three phenoldimethylenephosphonic acids differently substituted by auxo- or chromophoric groups was studied. These ligands may be considered as pentaacids. Their p K a were determined in aqueous solution at 25 °C and constant ionic strength 0.1 mol dm −3 by potentiometry and UV–visible spectrophotometry. Eventually, the complexing power of these molecules with lanthanide cations, Ce 3+, Pr 3+, Nd 3+, Sm 3+ and Eu 3+, was studied keeping in view the possible application to the treatment of radioactive liquid waste. The number, the nature of the species in solution, their stability constants and their individual electronic spectra as restored by computation have been determined. In all cases, complexes of 1:1 stoichiometry accompanied by hydroxy and protonated species are postulated. The comparison of tri- and pentaacids confirms that the acids having the methyl group at the para position with respect to the phenolic OH, have the highest complexing power.

Technetium(VII) transport across supported liquid membranes (SLMs) containing 2-nitrophenyl octyl ether (NPOE)

Technetium is one of key issues in the treatment of radioactive liquid waste because of its long half-life in combination with high fission yield and its geochemical mobility. For the removal of Tc(VII) from water and concentrated alkaline solutions, 2-nitrophenyl octyl ether (NPOE) is a very effective extractant. In this paper we describe the application of supported liquid membranes (SLMs) impregnated with NPOE for the removal of Tc(VII) from these solutions by using 1.5 M HNO3 receiving phase solutions. Transport of Tc(VII) across a SLM was evaluated with a mechanistic model using a permeability coefficient P to describe the rate of transport. SLM transport of Tc(VII) with NPOE is completely membrane diffusion limited and that there are no aqueous resistances. The membrane diffusion coefficient D m was calculated to be D m =6.4×10-13 m2/s. Permeability is highest for transport from pure water source solution, with P = 3.2×10-4 cm/s. From NaOH solutions the permeability decreases slightly. For acidic source phase the permeability is even lower due to the poor extraction yields of Tc(VII) from acidic solutions into NPOE. Counter current transport of H+ does not affect the extraction and permeability. The Tc(VII)-NPOE system is very robust, only small quantities of NPOE are needed, and the membrane distribution and permeability coefficients are sufficiently large for practical applications.

Membrane processes in nuclear technology-application for liquid radioactive waste treatment

Membrane methods can be considered as the most energy-saving separation techniques. Separation abilities of membranes allow the elimination of many non-effective and energy consuming methods and their replacement by new, modern technologies, friendly environment friendly. An application of membrane methods for liquid radioactive wastes treatment requires solving many problems connected with the proper selection of the membranes, membrane modules and other equipment according local conditions: chemical and radiochemical composition of the effluents treated, their activity and total salinity. The installations working in nuclear industry have to fulfil very strict requirements. They ought to be reliable, constructed from special materials defined by separate regulations. Only small number of manufacturers of membrane devices has for their products the certificates of International Atomic Energy Agency. Reverse osmosis (RO) as a method for liquid waste treatment has been examined at laboratory and pilot plant installations. The experience with the process led to design and construction of the industrial plant, 1 m3 capacity, composed of three RO stages. The plant will be included into the system for liquid radioactive wastes purification operating at Institute of Atomic Energy in Swierk near Warsaw, treating the liquid waste from all of Poland. Membrane distillation (MD) can be an alternative for liquid radioactive waste concentration. On the basis of previous laboratory tests a pilot plant for liquid radioactive wastes concentration employing direct contact MD was constructed. Pilot plant experiments showed MD is interesting solution for liquid low-level radioactive waste treatment. As MD is characterised by high retention, large decontamination factors were obtained in separation of radionuclides, which are present in liquid low-level radioactive wastes mainly in an ionic form. The RO and MD plants for liquid low level radioactive wastes treatment are presented in the paper and the evaluation of both methods, as well.

Sorption Recovery of Strontium from Seawater

Sorption recovery of strontium from seawater and prospects of using selective sorbents for treatment of seawater or mixtures of liquid radioactive wastes (LRW) with seawater to remove 90Sr are examined. A comparative analysis is made of characteristics of various sorbents. The most of the sorbents studied demonstrate low distribution coefficients and selectivity with respect to strontium, being unable to provide efficient removal of 90Sr from seawater. The exceptions are new sorption reagents developed by the authors, which show promise for treatment of LRW to remove strontium. The possible mechanism of strontium sorption with these sorbents is suggested.

Simulation of zeolite fixed bed columns used for treatment of liquid radioactive wastes

In treatment of liquid radioactive wastes by ion exchange technique, specific attention is drawn to the simulation of exchange system behavior. Mathematical models are particularly useful in the design and optimization of ion exchange columns to predict the characteristics of the breakthrough curve under a given set of conditions. A systematic mathematical model for prediction of the concentration profile of in-going cation (strontium) to a zeolite fixed bed as a function of time or eluted volume, to obtain the shape of the exchange zone, has been developed. The model was verified by experiments of 0.2 N sodium nitrate solution with 5×10-5 Sr2+ using three different types of natural zeolites. A Fortran-77 computer program was designed to run the model on IBM computer. The model was used to examine how the concentration profiles are affected by the operating parameters. A rough calculation of Reynolds Number was carried out to check the flow regime operating on the used column.

On-line monitoring of wastewater using ion chromatography.

Ion Chromatography (IC) has been used for the on-line determination of anions and cations in a variety of process streams. On-line monitoring of process and wastewater streams optimizes the control of treatment methods by providing early indications of problems that could increase discharges of hazardous compounds to the environment. It is important for the immediate detection and remediation of process upsets in critical streams. The waste flow to the Radioactive Liquid Waste Treatment Facility at the Los Alamos National Laboratory (LANL) is processed before discharge and requires monitoring. Process chromatography is used to monitor the trends of contaminants in real time. The purpose of this study is to develop an automated on-line IC procedure for the simultaneous determination of anions in LANL wastewater.

Concentrating Low-Level Tritiated Water through Isotope Exchange

Trapping of tritium on polymers with specific functional groups was investigated as a means of treating waste streams containing low levels of tritium. Chemical exchange of tritium with hydrogen on the functional group was used as the mechanism for trapping. The polymers tested include Aurorez polybenzimidazole resin beads, Chelex 100 resin beads, Duolite GT-73, microcrystalline cellulose, and polyethylenimine. The tests were performed under simulated operating conditions on water obtained from the Radioactive Liquid Waste Treatment Facility at Los Alamos National Laboratory. Tritiated water from the Tritium Systems Test Assembly is discharged to this plant. Polyethylenimine is a water-soluble polymer that was tested using a stirred membrane cell with an ultrafiltration membrane. All of the polymers except polyethylenimine took up tritium from the water. Polybenzimidazole demonstrated the highest tritium uptake. The results are explained on the basis of the type of functional group, hydrogen bonding, and rigidity of the molecular structure of the polymer. The theoretical calculations indicate that significant isotope discrimination requires high-frequency modes with hydrogen bonding contribution and support the experimental findings. Modeling suggested trends that may lead to structures that are more efficient in trapping tritium.

Concentration of radioactive components in liquid low-level radioactive waste by membrane distillation

The paper addresses some aspects of liquid low-level radioactive waste (LLLW) purification. Since the volume of liquid low-level wastes is usually large and the activity is rather low, the radioactive substances separated from the non-active portion have to be concentrated into the small volume for subsequent conditioning and disposal. The need for the improvement of decontamination and minimisation of the costs have led to new specific methods being under examination and development. The method proposed in the paper is membrane distillation. The experimental work described below supports the statement that membrane distillation can be an attractive alternative for liquid radioactive waste treatment. The advantages of membrane distillation over the other processes commonly used for the processing of LLLW are discussed in the paper.

Complexation of uranyl ion by three polyacrylamide type polymers: Electrochemical preparation and leaching tests investigations

We describe an original process for the treatment of low level activity radioactive liquid wastes. It deals with the electrochemical preparation of three polyacrylate polymers: polyacrylamide (PAam), polyacrylamidoglycolic acid (PAAG), polyacrylamidomethylpropanesulfonic acid (PAMPS) which are capable of complexing uranyl ions. We have demonstrated the complexation of uranyl by FT-IR and UV-Visible spectroscopy. All these complexes are soluble in water and we insolubilize in turn the complexes by crosslinking or by neutralization of positively charged complexes by the addition of polyanions to the medium. We have then done dynamic and static leaching tests on these insoluble complexes.

An experimental study on liquid radioactive waste treatment process using inorganic ion exchanger

Using commercial inorganic, organic sorbents and activated carbons, the treatment of low level liquid radwaste in nuclear power plant was studied. The batch, column and pilot tests were performed using simulants and actual liquid radwaste. The tests were focused on the removal capacity of the sorbents under sodium ion concentration since the liquid radwaste commonly contains a large amount of sodium ion which may affect the removal capacity of ion exchangers. The target ions to remove with sorbents were radionuclides such as Co‐58, Co‐60, Cs‐134, and Cs‐137 which are the major species in the liquid radwaste. The fundamental experiments showed that the inorganic sorbents and activated carbons have a better efficiency under sodium ion concentration for a cesium removal than a cobalt removal, whereas the organic resin is better for the cobalt removal. A new process for liquid radioactive waste treatment was proposed here based upon the experimental results. That is composed of a filter, activated carbon, inorganic ion exchanger, organic cation exchanger and organic anion exchanger in series. The process showed that the activated carbon was not effective for the cobalt removal, but had the ability to reduce the COD of liquid waste. The organic anion exchanger was used to control pH and to remove radioactive iodine if present. This combined process of using the inorganic ion exchanger was 4∼8 times more effective than that of the conventional organic ion exchanger.

Membrane technologies for liquid radioactive waste treatment

The paper deals with some problems concerning reduction of radioactivity of liquid low-level nuclear waste streams (LLLW). The membrane processes as ultrafiltration (UF), seeded ultrafiltration (SUF), reverse osmosis (RO) and membrane distillation (MD) were examined. Ultrafiltration enables the removal of particles with molecular weight above cut-off of UF membranes and can be only used as a pre-treatment stage. The improvement of removal is achieved by SUF, employing macromolecular ligands binding radioactive ions. The reduction of radioactivity in LLLW to very low level were achieved with RO membranes. The results of experiments led the authors to the design and construction of UF+2RO pilot plant. The development of membrane distillation improve the selectivity of membrane process in some cases. The possibility of utilisation of waste heat from cooling system of nuclear reactors as a preferable energy source can significantly reduce the cost of operation.

Feasibility study of the applicability of the activated sludge process to treatment of radioactive organic liquid waste

We used an activated sludge process to treat radioactive organic liquid waste. Organic liquid waste is difficult to treat by conventional radioactive liquid treatment processes, but in order to reduce long-term irradiation of the public the removal of radionuclides from such waste is preferable to dilution. Activated sludge processes are widely used for the biological treatment of sewage and are considered appropriate means for treating radioactive organic liquid waste. In this process, the fate of radionuclides eluted by treated water or immobilized by activated sludge, is extremely important for public safety and for the treatment of radioactive organic liquid waste. We performed uptake and desorption behavior experiments on the three short half-life radionuclides 134Cs, 57Co and 85Sr, and used three nutritive types of artificial sewage as the feed solution. On the basis of the results, we discuss the uptake-desorption behavior of these radionuclides in an activated sludge process. We conclude that treatment of radioactive organic liquid waste by an activated sludge process is possible, but improvements must be made in the process if it is to be more effective.

Use of Selective Sorbents for Liquid Wastes Treatment

ABSTRACTAcidic salts of polyvalent metal antimonates(M-antimonates(M-Sb); M=Cerium, Tin, Titanium and Silicon) have been synthesized under different conditions( 1,2). The products were characterized by powdered X-ray diffraction patterns, Differential Thermal Analysis(DTA) and infrared spectrometry. Chemical stability of the product materials were studied by mixing 50 mg of the prepared materials with 50 ml of the desired medium(H20, HNO3 and HCI) with determination for the concentration of the metalions dissolved(Sb, Ce, Sn, Ti and Si) which showed high chemical stabilities in water and acid media up to I OM HNO 3 and 6M HCI.The data of the distribution coefficients showed that the selectivity decrease in the order; Eu3+> Co2+> Sr2+> Cs+ for cerium(IV) antimonate(CeSb), tin(IV) antimonate(SnSb) and silicon(IV) antimonate(SiSb), while the selectivity decrease in the order UO22+>Th4+ for titanium(IV) antimonate(TiSb). Besides, the effect of EDTA, citric acid, ferric nitrate and sodium nitrate as interfering ions in solution on the distribution coefficient of the studied cations for CeSb and SnSb were studied under certain conditions. The results showed that, the Kj values of CS+, Co2+ and Eu3+ are decreases with increasing the concentrations of ferric and sodium nitrates in the feed solutions for both materials and also Kd values are effected to some extent in case of EDTA and citric acid. Based on the obtained results, practical separation experiments on column were performed(3).The following figures represents the break-through curves for CeSb and SnSb columns for some radionuclides 60Co (10-3M ) as example. From the above studies we conclude that, CeSb and SnSb have been successfully used for the quantitative separation of cesium which suggests its use in the treatment of radioactive liquid waste.