Inorganic ion exchangers in radioactive waste management

The removal behavior of stannic and zirconium phosphates was assessed for Sr(II) ions as a function of sorptive concentration, temperature and pH. It was observed that an increase of these parameters enhanced the removal of Sr(II) ions from aqueous solutions. First order uptake of Sr(II) followed the Freundlich adsorption isotherm for the entire range of sorptive concentration (10^-2 to 10^-8 mol^.dm^-3). The study of temperature dependence showed that the endothermic and irreversible type of uptake proceeds by an ion-exchange type mechanism.     

Ion exchangers in radioactive waste management VII. Radiotracer studies on adsorption of Ba(II) and Sr(II) ions on hydrous thorium oxide

Hydrous thorium oxide (HTO) was synthesized and laboratory study was conducted to address its applicability for decontamination of barium and strontium ions from radioactive liquid wastes using radiotracer technique. The adsorption of Ba(II) and Sr(II) on HTO has been investigated as a function of pH, concentration and temperature of the adsorptive solution and the results obtained show that these parameters affect the extent of adsorption very appreciably. Pre-treatment of oxide adsorbent with neutrons and -radiation from a 11.1 GBq Ra–Be neutron source reduces its adsorption capacity upto 24 hours of irradiation and then enhances it on further irradiation. The nature and mechanism of adsorption are discussed.     

Inorganic ion exchangers for strontium removal from radioactive waste : a review

Journal of Radioanalytical and Nuclear Chemistry - 90Sr is the most hazardous radioactive isotope of strontium that is produced during the normal operation of nuclear reactors. It can also spread...     

Mathematical modeling of physico-chemical characteristics of cement-waste composites in radioactive waste management

An optimization of mortar (as matrix), improved with bentonite clay, used for immobilization of radionuclides⁶⁰Co,¹³⁷Cs,⁸⁵Sr and⁵⁴Mn, is presented. A relatively simple mathematical model is given, which permits minimization of leach rate and permeability and maximization of compressive strength. An optimal solution, based on experimental data, is given. These results will be used for a future Yugoslav radioactive waste storing center.     

Selective separation of palladium from simulated intermediate radioactive waste nitrate by IRA-410 and IRA-900 anion exchangers

Selective efficient method have been for separation of palladium by strong basic anion exchangers IRA-410 and IRA-900 from intermediate radioactive nitrate medium. The different conditions for exchange behaviour of palladium from [ILLW] solutions containing numbre of elements were investigated by batch technique. Selective recovery of palladium from the [ILLW] solution was achieved using column technique. The elution of palladium was carried out via reduction with formic acid where the rate of the reduction process was increased by decreasing the formic acid concentration till 50% followed by dissolving the separated palladium by nitric acid.     

Ion exchangers containing phosphorus in their functional group

Summary Uranium or thorium separations from a number of various ions were studied by means of cation exchangers containing phosphorus in their functional group. These ion exchangers adsorb selectively only UO₂ ²⁺ or Th⁴⁺ ions from the mixture studied in a medium of >0.4 N nitric or hydrochloric acid. Several di- and trivalent cations are not sorbed under these conditions. In the absence of UO₂ ²⁺ and Th⁴⁺ ions, Me²⁺ may be more easily separated quantitatively from Me³⁺ in 0.2 N nitric or hydrochloric acid than with cation exchangers containing the -SO₃H group.

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Zusammenfassung Die quantitative Trennung von UO₂ ²⁺ oder Th⁴⁺ von einer Reihe anderer Ionen wurde mit Hilfe phosphorhaltiger Kationenaustauscher untersucht. Diese Ionenaustauscher sorbieren selektiv nur UO₂ ²⁺ oder Th⁴⁺-Ionen aus einem Medium von >0,4 N HNO₃ oder HCl. Eine Reihe verschiedener zwei- und dreiwertiger Kationen wird unter diesen Bedingungen nicht sortiert. Bei Abwesenheit von UO₂ ²⁺- und Th⁴⁺-Ionen kann man Me²⁺ in 0,2 N HNO₃- oder HCl-Lösung quantitativ von Me³⁺ trennen, und zwar leichter als mit -SO₃H-haltigen Austauschern.

     

Characterization of deep sea sediments by INAA for radioactive waste management purposes

An instrumental neutron activation analysis method, using both reactor flux and epi-cadmium neutrons, has been developed for the determination of major, minor and trace elements in sub-seabed sediments. The method involves two different irradiations followed by three different counting periods using high-resolution Ge(Li) and low-energy photon detectors. The list of elements determined includes Ag, Al, As, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Dy, Eu, Fe, Ga, Gd, Hf, Hg, I, In, K, La, Lu, Mg, Mn, Mo, Na, Nd, Ni, Pt, Rb, Re, Rh, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Th, Ti, Tm, U, V. W, Yb, Zn, and Zr. The accuracy of the method has been evaluated by analyzing four different standard reference materials. The method has been applied to core samples collected from the Great Meteor East and the South Nares Abyssal Plain which are being evaluated as potential sites for the possible disposal of vitrified highly active waste.     

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.     

Ion exchangers based on vinyloxyethylamine and epoxy-phenol-aldehyde compounds

A method for preparing highly permeable polyelectrolytes by the reaction of homo-and copolymers of vinyloxyethylamine with various glycidyl ethers of phenol-aldehyde compounds was developed. The physicochemical characteristics of these polyelectrolytes were studied.     

Current status of radioactive waste disposal

This paper describes the technical issues involved in the development of a feasible solution toward permanent radioactive waste disposal. Recent progress on internationally collaborative research efforts concerning the multibarrier concept, in situ experiments, computer modeling and natural analogues are discussed.     

Denitration of simulated radioactive liquid waste

Journal of Radioanalytical and Nuclear Chemistry - Radioactive liquid wastes containing large amounts of nitric acid (approx. 4–7 M) generated in the nuclear fuel cycle are very...     

Fixation of radioactive isotopes on bentonite as radioactive waste treatment step

Fixation of¹³⁷Cs,¹⁴⁴Ce,⁶⁰Co,⁹⁰Sr,²⁴⁰Th and²³³U from aqueous and phosphate media on bentonite clay was studied. The fixation of the radioactive ions on bentonite surfaces was dependent on the pH behavior of the metal ions. A method was proposed to use bentonite as an absorbent of ions from simulated radioactive waste as a treatment step.     

Separation of palladium from simulated intermediate radioactive waste/chloroacetic acid/nitrate medium by IRA-410 and IRA-900 anion exchangers

Separation of palladium by strongly basic anion exchangers IRA-110 and IRA-900 from intermediate radioactive liquid waste in chloroacetic acid/nitrate medium containing thirteen elements have been achieved. Different conditions have been studied, the effect of NaNO₃ as salt content, chloroacetic acid and hydrogen ion concentration have been investigated. Selective recovery of palladium from the [ILLW] solution was achieved using the column technique. The selectivity increased by using chloroacetic acid/nitrate than in nitrate medium. The elution of palladium was carried out via reduction with formic acid where the rate of the reduction process was increased by decreasing the formic acid concentration till 50% followed by dissolving the separated palladium by nitric acid.     

Comparison of mathematical interpretation in radioactive waste leaching studies

Transport phenomena involved in the leaching of a radioactive material from a concrete composite matrix into surrounding water are investigated using three methods based on theoretical equations. These are: a diffusion equation derived for a plane source model, a rate equation for diffusion coupled with a first-order reaction and an empirical method employing a polynomial equation. The results are compared with respect to their applicability to the ¹³⁷Cs leaching data. The results presented in this paper are part of those obtained in a 25-year mortar and concrete testing project which will influence the design of radioactive waste management for a future Serbian radioactive waste disposal center.     

Treatment of radioactive waste phenol with Fenton's oxidation

A new procedure was developed for the waste treatment of radioactive phenol on a laboratory scale. Waste phenol was dissolved in water (2% as phenol), and ferrous ion (10 mg/l as Fe2+) was added. Hydrogen peroxide (6% as H2O2) was added separately in three steps, 20, 30, and 50% of the volume, in order to avoid rapid reaction. The solution was heated at 80-90 degrees C for several hours in a beaker covered with a watch glass till the color of the solution changes from red purple to pale yellow. Then, the solution was neutralized with sodium hydroxide and heated for 1 h to decompose excess hydrogen peroxide. When the procedure is carried out with four 2 l beakers on a hot plate, 100 ml of phenol (1,200 ml of the aqueous solution saturated with phenol) can be oxidized simultaneously.     

Analysis of 36Cl in Savannah River Site radioactive waste

The present work shows the activity levels of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that ⁴⁰K and ²²⁸Ra concentration is nearly uniform throughout the studied area while ²²⁶Ra and ¹³⁷Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of ²²⁶Ra/²²⁸Ra ratio (0.72) in the sediments indicates that ²³⁸U has relatively greater solubility and mobility than ²³²Th. Similarly, low activity ratio (0.18) for ¹³⁷Cs/⁴⁰K reflects the presence of very high content of ⁴⁰K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between ²²⁶Ra and ²²⁸Ra and ¹³⁷Cs and ⁴⁰K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.     

Ion exchangers based on homo-and copolymers of vinyloxyethylamine and glycidyl methacrylate

An efficient method is developed for synthesis of highly permeable ion-exchange resins through the reaction of glycidyl methacrylate with polyvinyloxyethylamine and its copolymers with nitrogen-containing monomers with preservation of the nitrogen functional groups in the latter monomers. The synthesis conditions are optimized, and physicochemical and sorption properties of the resulting polymers are examined.     

Ion exchangers based on homo-and copolymers of vinyloxyethylamine and epoxy compounds

A method was developed for synthesis of highly permeable polyelectrolytes through the reaction of polyvinyloxyethylamine with various glycidyl derivatives of dihydroxybenzenes, aminophenols, and aromatic diamines. The physicochemical and sorption properties of the resulting polymers were examined.