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- Author or Editor: A. Dyer x
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Cerenkov spectroscopic assay of fission isotopes
I. Assay for90Sr and89Sr in aqueous nitrate solutions in the presence of137Cs
Abstract
The procedure for the assay of90Sr or89Sr in the presence of a weak beta-emitter, such as137Cs is described which could be applicable in studies on the purification and decontamination of aqueous radioactive wastes by ion-exchangers. The influence of colour-quenchers on the counting efficiency of radiostrontium has also been investigated.
Abstract
We report here on the effect of nitric acid solutions on the structural stability and ion-exchange properties of a series of natural and synthetic zeolite molecular sieves. The implications of this work for the industrial application of zeolites in acidic aqueous systems are discussed.
Abstract
Studies were made on the uptake of zirconium, hafnium and niobium isotopes onto zeolites and amorphous zirconium phosphate. Ion exchange capacities and distribution coefficients were determined and the influence of pH examined. Kinetic experiments were made to determine the rates of uptake of the radioisotopes on the exchangers and to measure the leaching of isotopes from preloaded exchangers by synthetic sea water, simulated pond water and distilled water.
Abstract
The ability of zeolites to remove thorium-232 from naturally radioactive thorium nitrate solutions was studied by ion exchange, adsorption and surface phenomena. The best zeolites were a clinoptilolite from Mudhills, California, USA and a mordenite rich tuff from Eastgate, Nevada, USA. As the concentration of thorium in solution was increased the mechanism of thorium removal switches from that of partial ion-exchange to a surface precipitation. This was confirmed by electron probe microanalysis (EPMA) in conjunction with XRD and Energy Dispersive X-ray analysis (EDX). A Langmuir-type of adsorption occurred with the thorium-232 daughter isotopes at the same time as partial exchange/precipitation of the thorium parent which is in regular equilibrium with its natural daughters. Some experiments with234Th were carried out to confirm this hypothesis as well as column experiments to confirm the usefulness of the Th removal.
Removal of fission products from mixed solvents using zeolites
II. Caesium and strontium removal
Abstract
The solvents tributylphosphate (TBP) and odourless kerosene (OK) are widely used to extract plutonium(IV) and uranium(V) in nuclear processing plants. Their use depends upon their relatively low affinity for fission products, but small amounts of radioisotopes are taken up by them. To aid disposal/reuse of these solvents it is of use to study ways of removing radioisotopes of Cs and Sr from them. This paper describes simple distribution coefficient (K d ) measurements to test the ability of aluminosilicate zeolites to remove137Cs and90Sr/90Y from TBP, OK and their mixtures.
Removal of fission products from mixed solvents using zeolites
I. Ruthenium removal
Abstract
The solvents tributylphosphate (TBP) and odourless kerosene (OK) are widely used to extract plutonium(IV) and uranium(V) in nuclear processing plants. Although these solvents are chosen because of their low affinity for fission products it is, nevertheless, of value to study ways of removing the small quantities of fission products, such as isotopes of Cs, Sr and Ru, which can be present in the solvents. This paper describes simple distribution coefficients (K d) measurements made to test the ability of the aluminosilicate zeolites to remove106Ru from TBP, OK, and their mixtures.
The uptake of radioisotopes onto clays and other natural materials
II. Cesium, strontium and ruthenium onto soils and peat
Abstract
The ability of natural and simulated soils to take up radioisotopes of cesium, strontium and ruthenium was examined. Uptakes were assessed by distribution coefficients measured in the presence of different concentrations of Na, Ca, Mg and HN4 cations, and from synthetic groundwaters. Peat was included in similar studies for comparison purposes. Conclusions were drawn as to the effect of soil and ground water compositions on isotope uptake taking into account the results described in Part 1 of this series1 which estimated the distribution coefficients for137Cs,89Sr and106Ru (as chloride or nitrosyl) shown by illite and montmorillonite clays. These, or similar, clays were soil components in this study.
The uptake of radioisotopes onto clays and other natural materials
III. Leaching of cesium and strontium from clays
Abstract
The leaching of137Cs and90Sr from Surrey Earth montmorillonite and Silver Hill illite has been studied. Three forms of the clays, calcined and uncalcined and their composites with cement, were leached with four leachants, deionized water, and simulated sea ground and storage pond waters. Results were expressed as the cumulative fraction of activity leached against the square root of time, and used to compute diffusion coefficients. These suggested that all the leaching processes studied were slow (10−22 to 10−18 m2.s−1).
Abstract
Commercially available synthetic hydrous oxides (Ferrox, Zirox, Alumina, Oxti, and Oxtain) have been used to study the sorption of some anionic species from simulated radioactive waste. Results of the analysis showed varying degrees of uptake for the anions in various media solutions. Sorption was most effective in the solution pH 2–7 range following the amphoteric nature of these materials. The presence of competing anions had a marked effect on the sorption properties of the material.
Abstract
The uptake of sodium, caesium and rubidium onto Los Transcos clay was studied using the batch method. Sodium-22, rubidium-86 and caesium-137 were used as tracers. In most of the experiments cation concentrations used were 0.01 N. Triple distilled and deionized water were used and the grain size of all solid particles was 
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m. In all cases a few hours of shaking was enough to reach the equilibrium. The ion exchange isotherm experiments were performed by using ammonium forms of the clays. Results showed that the ammonium form of Los Trancos clay was selective for Cs and Rb uptake but Na was not prefered. Cation uptake kinetics were complete in 1 h.
