Membrane extraction for preconcentration of radionuclides

Membrane extraction is treated as an analogue of solvent extraction in three-phase distribution systems. Its advantages and drawbacks are discussed with respect to separation and preconcentration of radionuclides, fission products of uranium and uranium itself.     

Experimental measurements of short-lived fission products from uranium,neptunium, plutonium and americium

Fission yields are especially well characterized for long-lived fission products. Modeling techniques incorporate numerous assumptions and can be used to deduce information about the distribution of short-lived fission products. This work is an attempt to gather experimental (model-independent) data on short-lived fission products. Fissile isotopes of uranium, neptunium, plutonium and americium were irradiated under pulse conditions at the Washington State University 1 MW TRIGA reactor to achieve ~10⁸ fissions. The samples were placed on an HPGe (high purity germanium) detector to initiate counting in less than 3 min post irradiation. The data was analyzed to determine which radionuclides could be quantified and compared to the published fission yield data.     

Volatility of tellurium and various fission products in heated nitric acid solutions

The volatility of tellurium and some other fission products was radiochemically studied in heated nitric acid solutions. As tracers ¹²¹Te produced by bremsstrahlung of an electron LINAC and other fission products produced by neutron irradiation were used. The distribution rate of radionuclides between the mother solution and the condensate, was considered as volatility, and was determined. The volatility of tellurium was found to be small and close to that of cesium. Volatilization tests were also performed in the presence of large amounts of solutes.The authors wish to thank Mr. Roy Jacobus for his help in preparing this paper.     

Volatility of tellurium and various fission products in heated nitric acid solutions

The volatility of tellurium and some other fission products was radiochemically studied in heated nitric acid solutions. As tracers ¹²¹Te produced by bremsstrahlung of an electron LINAC and other fission products produced by neutron irradiation were used. The distribution rate of radionuclides between the mother solution and the condensate, was considered as volatility, and was determined. The volatility of tellurium was found to be small and close to that of cesium. Volatilization tests were also performed in the presence of large amounts of solutes.The authors wish to thank Mr. Roy Jacobus for his help in preparing this paper.     

Determination of long-lived fission products and actinides in Savannah River Site HLW sludge and glass for waste acceptance

Savannah River Site (SRS) is immobilizing the radioactive, high-level waste sludge in Tank 51 into a borosilicate glass for disposal in a geologic repository. A requirement for repository aceeptance is that SRS report the concentrations of certain fission product and actinide radionuclides in the glass. This paper presents measurements of many of these concentrations in both Tank 51 sludge and the final glass. The radionuclides were measured by inductively coupled plasma mass spectrometry and α, β, and γ counting methods. Examples of the radionuclides are⁹⁰Sr,¹³⁷Cs,²³⁸U and,²³⁹Pu. Concentrations in the glass are 3.1 times lower due to dilution of the sludge with a nonradio-active glass forming frit in the vitrification process. Results also indicated that in both the sludge and glass the relative concentrations of the long lived fission products insoluble in caustic are in proportion to their yields from the fission of²³⁵U waste in the SRS reactors. This allowed the calculation of a fission yield scaling factor. This factor in addition to the sludge dilution factor can be used to estimate concentrations of waste acceptance radionuclides that cannot be measured in the glass. Examples of these radionuclides are⁷⁹Se,⁹³Zr, and¹⁰⁷Pd.     

Aerosol radioactivity monitoring in Bratislava following the Chernobyl accident

The radiation situation in Bratislava following the Chernobyl accident is discussed. Measurement results of - and -radioactivity of aerosols are presented. The evolution of the activity ratios in air for some radionuclides is discussed. Their distribution indicates different transport and deposition properties for the volatile and nonvolatile fission products. The results are compared with long-term measurements of anthropogenic radionuclides released to the atmosphere by nuclear bomb tests.     

Determination of short-lived radionuclides in fresh fall-out debris for identification of nuclear weapon tests

Radiochemical procedures for the assay of short-lived fission and activation products are described. They are rapid and quantitative and the radionuclides separated are radiochemically pure. Ratios of some of the short-lived radionuclides obtained by these measurements for selected Chinese and French nuclear tests are given and provide information about the fissile material used in the tests.     

Rapid separations of corrosion and fission products

A separation scheme of a complex mixture of radiohygienically important radionuclides of corrosion and fission products has been worked out. Rapid separation by means of solvent extractions with metal (sodium, antimony, zinc) diethyldithiocarbamates has been achieved. Chloroform containing metal diethyldithiocarbamates has been used as the organic phase. The procedure permits to separate selectively the representative radionuclides. The selectivity of separation was verified by gamma spectrometry.     

Radiochemical determination of cadmium isotopes in radioactive debris

(109)Cd and (113m)Cd were produced in a high altitude nuclear explosion during 1962. Analysis of filters from aircraft and balloon samplers enables the products of this single detonation to be traced. A radiochemical procedure is presented which allows determination of the cadmium radionuclides in the course of a sequential analysis for fission products and activation products from nuclear weapons tests. The sensitivity, recovery and decontamination from other radionuclides are adequate.     

Preliminary investigation into suitable techniques to measure the chemical yield of radionuclides in thermal neutron irradiated samples at AWE (Atomic Weapons Establishment)

Radiochemical separation methods are required for the accurate measurement of radionuclides in complex matrices. To be able to quantify the results after the separation of radionuclides, known amounts of either radioactive tracers or inactive carrier solutions are added at the start of the separation. The added isotopes/elements are then measured at the end of the analysis to calculate the chemical yield for the element or isotope. The chemical yield data is applied to the counting data of the analytes of interest to produce quantified results. Recently, changes have been made to the techniques used to measure chemical yields at the Atomic Weapons Establishment for samples containing fission products. Preliminary development work using wavelength dispersive X-ray fluorescence and inductively coupled plasma–atomic emission spectrometry is discussed, including a comparison of results and evaluation of measurement uncertainty. The use of the techniques to measure fission products in a thermal neutron irradiated uranium sample is described.     

Actinides and Long-Lived Radionuclides in Tissues of the Japanese Population: Summary of the Past 20-Year Studies

Radioactive fallout constitutes the major source of contamination of the environment with fission products. Our primary interest was in selected fission products, such as ¹³¹I, ⁸⁹Sr, ⁹⁰Sr, and ¹³⁷Cs, and neutron activation products, such as ³H and ¹⁴C. Plutonium-239,240, ²⁴¹Am and ⁹⁰Tc are generated from nuclear tests, and they are important by-products of nuclear industries. Polonium-210, ²¹⁰Pb and ²³²Th, ²³⁰Th and ²²⁸Th occur widely in nature. These radionuclides enter the human body through inhalation and the ingestion through food and water. These nuclides may cause radiation doses to certain organs of the body. Assessment of the resulting health hazards is an essential public health activity, which demands reliable techniques for the assay of the various radionuclides in man and his environment. In this paper, we present the accumulation of radionuclides from man-made sources and primordial radionuclides in various tissues of the Japanese population. The studies were performed at the Department of Public Health, Akita University School of Medicine, during the periods from 1973 to 1995.     

The role of NAA in nuclear chemistry education

One of the missions of our Institute is the promotion of basic nuclear teaching for students as well as professional teaching for workers in nuclear industry and research. For nuclear chemistry education, we present here a one day teaching course on radioactive decay and nuclear reactions, and a two or three days course based on reactor irradiation of uranium oxide, instrumental and radiochemical analysis of fission products. In the first experiment, the neutron capture is presented as an example of nuclear reaction; the neutron activation of a silver coin with a Am-Be neutron source, followed by γ-ray spectrometry, is used to identify three radionuclides of silver and to calculate their half-lives. In the second experiment, our teaching reactor is used as a neutron source with a flux about 10¹⁰ n·cm⁻²·s⁻¹ at a low thermal power (10 kW). This low flux allows us to irradiate a small uranium sample which is usable for spectrometry after a short cooling time of about two hours. The first day is reserved for instrumental analysis of the fission products and a second day for the radiochemical separation of a fission radionuclides. With these experimental results, the students have to calculate the number of fissions in the irradiated sample. On optional third day for postgraduate students is devoted to the presentation of NAA and some applications as uranium determination by the fission product spectrometry.     

Direct assay techniques for comprehensive radionuclide quantification of radwaste packages

Battelle, Pacific Northwest Laboratories has recently developed, tested and field-demonstrated a technology for the direct assay of transuranic radionuclides (TRU), fission products, and activation products in a variety of radwaste packages generated at commercial nuclear power plants. This technology involves non-destructive passive neutron counting for determination of nanocurie/gram quantities of the TRU radionuclides. Direct gamma spectrometry combined with thermoluminescent dosimetry (TLD) and correlation analysis is also utilized to determine the concentrations of the fission and activation products present in the radwaste packages. Employing counting times of 10 to 20 minutes, a complete analysis of all radionuclides specified for assay by the U.S. Nuclear Regulatory Commission (in 10CFR61) prior to shallow-land disposal of commercial radwastes can be measured at concentrations at least tenfold below the least restrictive Class A waste catagory.     

Fixation mechanism between zeolite and some radioactive elements

Fixation of some fission products and actinide elements from aqueous solutions on zeolite was investigated. Studies showed that the interaction between the radionuclides and zeolite followed the exchange and the adsorption mechanisms. The relative importance of each depends on the type, the nature, and the size of the radioelement.     

A study of radionuclides in vegetation on abandoned uranium tailings

A study has been carried out of the uptake of uranium and other radionuclides by plants growing on abandoned tailings from an uranium mining operation. Assay methods included instrumental neutron activation analysis, delayed neutron counting, fission track imaging, and counting of natural radioactivity. Care was taken to avoid contamination of the plant material and a number of methods are described to identify such contamination. All plants observed showed high uptake of radionuclides, compared to plants studied from naturally uraniferous and control areas. Graminoid (grass-like) plants showed significant uptake in the above-ground parts while woody plants showed exceedingly high uranium accumulation in the root portions. These results have significance in determination of the spread of radioactive material from such sites.     

Mixing of atmospheric <Superscript>210</Superscript>Pb and <Superscript>7</Superscript>Be and <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr fission products in four characteristic soil types

Depth distribution of atmospheric ²¹⁰Pb and ⁷Be and ⁹⁰Sr and ¹³⁷Cs fission products was measured in two types of aeolian soils (desert dust and volcanic ash), irrigated paddy soil and strongly acidic soil. The depth dependence of ²¹⁰Pb, ⁷Be and ¹³⁷Cs show that these radionuclides have been diffused as solid soil particles in surface soil layers. In aeolian soil layers, about 50% of ⁹⁰Sr were diffused in surface soil layer and the remaining 50% had penetrated to deeper layers. The half of the fission particles containing ⁹⁰Sr were shown to have decomposed over the past 35 years.     

Occurrence of natural radionuclides and fallout cesium-137 in dry-season agricultural land of South Western Nigeria

The radioactivity of the Opa river — irrigated farmlands in the south western Nigeria was determined using an HpGe based, low-level passive gamma-counting system. With the exception of two isotopes, the main radionuclides analysed in the sample were the progenies of²³⁸U and²³²Th. The other two isotopes were the naturally occurring⁴⁰K and the anthropogenic¹³⁷Cs. The result obtained showed elevated levels of radioactivity from all detected radionuclides compared to the published data for this area. Enhanced levels of naturally occurring radionuclides is attributed to the use of phosphatic fertilizers for dry season vegetable cultivation along this river banks. The presence of the fission product¹³⁷Cs could be traced to the fallouts occasioned by the various French nuclear tests in the Sahara desert, and probably, some effect of the more recent nuclear reactor accident at Chernobyl in 1986.     

Production of radionuclides for nuclear therapy and environmental studies

This work is devoted to the production of the radionuclides used in nuclear medicine and as radiotracers for environmental research. Production methods for high LET radionuclides (⁶⁷Ga, ⁷⁷Br, ¹¹¹In, ²¹¹At) that are promising for radioimmunotherapy are proposed. Production techniques for short-lived analogues of highly radiotoxic long-lived fission products (Tc, Se, Sr) are developed. The techniques are based on extraction and chromatographic separation from a cyclotron target irradiated by α-particles and deuteron beams.     

Evaluation of Ge(Li) Compton suppression spectrometers for non-destructive radiochemical analysis

Ge(Li) Compton suppression spectrometers are evaluated relative to the specific needs of the analytical radiochemist. Their application to the analysis of radionuclides found in neutron activation, fission product, and environmental radionuclide analyses is discussed. This paper is based on work performed under United States Atomic Energy Commission Contract AT(45-1)-1830.