Determination of radioactive nuclides of uranium and thorium series and estimation of α-flux in LSI constituent materials

Gamma-rays of nuclides of uranium and thorium series in silicone resin and ceramics were measured with a Ge(Li) detector. The state of radioactive equilibrium was determined by comparing the concentrations of uranium and thorium with the radioactive concentrations of²¹⁴Pb and²¹²Pb. The radioactive equilibrium was attained in silicone resin but not in ceramics. The -flux was calculated from the concentrations of uranium and thorium and their daughter nuclides. The calculated values of -flux agreed with that of -flux measured.     

Determination of radioisotopes of Ce,Eu, Pu,Am and Cm in low-level-wastes from power reactors

Long-lived isotopes of lanthanides and actinides are very important for the disposal of low-level radioactive wastes. These nuclides serve for risk calculations of accidents. Their determination requires radiochemical separation from high activity main nuclides. Supervision of waste vessels is done by direct non-destructive -spectrometry of the key nuclides:⁶⁰Co for corrosion products and¹³⁷Cs as for fission products as for transuranic elements. The activity ratios of the long-lived nuclides to the key nuclides are called scaling factors. They have to be determined radiochemically in the laboratory in representative samples of each waste type. They are used for activity calculations of long-lived nuclides in the waste vessels. The scaling factors determined are of the order of magnitude of 10^–6 and due to the fact that we have used low-level measurement techniques, we could performe the necessary chemical separations in a laboratory not exceeding the 10-fold free-level limit.     

Systematic separation and determination of some neutron-activated nuclides and actinides in fallout samples

A method for systematic separation and determination of some neutron-activated nuclides and actinides is described. The method is designed to utilize stable isotopes and radioactive tracers as chemical yield monitors and to separate nuclides of interest from a single limited sample. Gravimetric, spectrophotometric, radiometric and X-ray fluorescence analysis were used for determination of chemical yields of the nuclides. Overall chemical yields generally ranged from 60–90%. Separated and purified nuclides were detected by -spectrometry or isotope dilution -spectrometry. The detection limit for neutron-activated nuclides is 10⁷ nuclides and the precision is better than 3% RSD.     

The correlations among various elements in neutron activation analysis — The evaluation of R-matrix and κ-matrix

The production rates (numbers of atoms per gram of the respective elements per second) of 40 radioactive nuclides of 34 elements by neutron capture reactions in a reactor were determined from about 130 photopeaks of the -ray spectra. The ratios of these production rates were called R-matrix elements. These production rates and the respective thermal neutron capture cross sections were used to calculate the respective apparent neutron fluxes at the position of irradiation and the -matrix elements which were the ratios of these apparent neutron fluxes. These matrix elements express clearly the correlations among various elements and thus may be used in the mono-standard or small-number-standards method in neutron activation analysis.     

Scaling factors for activated corrosion products in low-level-wastes from power reactors

Long-lived isotopes of corrosion products are very important for the disposal of low-level radioactive wastes. These nuclides serve for risk calculations of accidents. Their determination needs the radiochemical separation from high active main nuclides. Supervision of waste vessels is done by direct non-destructive -spectrometry of the key nuclide⁶⁰Co for corrosion products. The activity ratios of the long-lived nuclides to the key nuclides are called scaling factors. We have determined such factors radiochemically in evaporation residues of power water and cooling water. They are used for activity calculations of long-lived nuclides in the waste vessels. In case of⁵⁹Ni the obtained scaling factor was compared with a literature value and values calculated on the basis of nuclear data. Our value was in a good agreement with the calculated one. Due to the fact, that we have used low-level measurement techniques, we could perform the necessary chemical separations in a laboratory not exceeding the 10-fold free-level limit.     

On-line coupling of packed column supercritical fluid chromatography with multiple wavelength detector and radioactivity flow-through detector

Summary The coupling of packed column supercritical fluid chromatography with a commercial Radioactivity Flow-Through Detector for the sensitive and highly selective detection of radioactive nuclides (e.g.¹⁴C is described. The radioactivity flow-through detector showed no baseline shift when pressure or modifier (methanol) gradients were applied. The detector cell was pressure resistant even at high flow rates, over a period of approx. 100 hours and showed no leakage problems even at 40°C, 340 bar, 4.0 ml/min and a modifier content up to 20%.     

Chemical separation procedure for the nuclide analysis of a tantalum target irradiated for 500 days with 800 MeV protons

A rapid radiochemical separation procedure has been developed for the determination of long-lived and stable nuclides produced by spallation and activation in a tantalum target irradiated for 500 days with 800 MeV protons. In this procedure the matrix element tantalum and simultaneously the¹⁸²Ta activity, built-up by activation of the matrix with themalized spallation neutrons is removed from many elements. About 50 mg of the sample is dissolved in a mixture of concentrated nitric and hydrofluoric acid. After dilution tantalum is extracted with a solution of 0.2M tetrahexylammonium bromide in methyl isobutyl ketone (MIBK). The residual amount of tantalum and the remaining¹⁸²Ta activity are 0.0003% and the recoveries of 27 investigated elements are in the range of 96.0–99.9%. A further 22 elements are quantitatively separated according to their chemical behavior. In the final aqueous fraction the separated long-lived and stable nuclides of 49 elements can be measured with high sensitivity by -ray spectrometry and mass spectrometry (ICP-MS).     

Laboratory standard for radionuclides in nuclear waste

A laboratory standard for the determination of long-lived radionuclides in nuclear waste has been prepared using concrete as matrix. It will be used to check sample preparation procedures, chemical separations and methods for the determination of nuclides, e.g., nuclear counting techniques or mass spectrometry. The material chosen was a fine-grained ready-to-use cement mixture, to which the following radionuclides were added:⁶⁰Co and¹³⁷Cs as -ray-emitting nuclides,⁹⁹Tc,⁹⁰Sr and⁵⁵Fe as radionuclides emitting pure -radiation or low-energy electrons, and²³³U,²³⁷Np,²³⁸Pu and²⁴¹Am as -emitters. Care was taken to attain a homogeneous distribution of the nuclides in the standard material. Pieces of about 1 g were formed as suitable and representative samples. Repeated analyses were carried out with the standard to check its homogeneity. The analytical procedures are described in brief. The pieces of the standard material have the same content of nuclides within ±5% at a 95% level of confidence.     

Preparation of a radioactive multitracer solution from the reaction of selenium with 25 MeV nucleon40Ar ions

A radioactive multitracer solution was prepared from the reaction of selenium with 25 MeV/nucleon⁴⁰Ar ions. Using off-line -ray spectrometry, the solution containing 47 radioactive isotopes of 24 elements was obtained. The nucleide with the longest half-life was²²Na, and the shortest-lived one was⁸¹Rb⁸.     

Preparation of carrier-free group tracers from a gold target irradiated by high-energy heavy ions

A rapid radiochemical separation procedure has been finished by using of radiochemical separation and -spectrum measurement methods. In this isolation procedure, tantalum nuclides produced by the irradiation of natural tungsten targets with 14 MeV neutrons were extracted by methyl isobutyl ketone (MIBK) in the system of HF-HNO₃ mixed solutions. It has been found that tantalum was rapidly and efficiently separated in the isolation procedure and the decontamination factors of tungsten were more than 10⁴. The procedure is simultaneously used to separate tantalum from tungsten bombarded with intermediate energy (47 MeV/u)¹⁸O beams. The measured -spectra showed that tantalum can be separated from most elements produced in the nuclear reactions except for a few elements.     

Actinide uptake onto zeolite-L and SAPO-34

The characteristics of ion exchange of uranyl and americium, which are -emitting radioactive nuclides, were examined by batch and column methods. SAPO-34 showed good selectivity for uranyl ion at pH 2–3.5, and distribution coefficients of Am³⁺ and UO ₂ ²⁺ increased with equilibrium pH. -irradiation (2 MGy) did not show any significant effect on the uptake of both of actinide ions onto L and SAPO-34. Higher does of -irradiation (up to 10 MGy) created a change of equilibrium pH, and hence uptake, due to radiolysis of water and heat localization generated by -radiation and annealing processes.     

The role of induced secondary radiation in in situ sorption studies using β-, γ-emitting radionuclides

This article is focused on the effect of -induced radiation in in situ sorption measurements of⁶⁰Co (emitting -and -radiation). The results presented show that the intensity of solution background is primarily due to the -induced radiation (possibly caused by photoeffect and Compton-scattering) and does not change during cobalt accumulation. Experiments were carried out with a pure -emitting isotope (⁹⁹Tc) in order to elaborate a method for the separation of the intensities originating from -and -induced radiations. Various methods of evaluation of sorption measurements are discussed. The extension of the method to application of different radioactive nuclides is considered.     

Preparation of a radioactive multitracer solution from iron foil irradiated by 80 MeV/nucleon16O ions

Iron foil was irradiated with an 80 MeV/nucleon¹⁶O-ion beam. The foil was dissolved in hydrochloric acid, and Fe²⁺ in the solution was oxidized to Fe³⁺ with hydrogen peroxide. The solution was diluted to 6M in HCl and was passed through an anion exchange column. Washing with 6M HCl yielded a carrier- and salt-free multitracer solution covering radioactive nuclides of elements from sodium to manganese.     

Formation cross section of iron-60 with reactor neutrons in59Fe(n, γ)60Fe reaction

Ingrowth of⁶⁰Co radioactivity in an iron sample irradiated in a nuclear reactor has been measured for determination of formation cross section of⁶⁰Fe in the⁵⁹Fe(n, )⁶⁰Fe reaction with reactor neutrons. After 5 years cooling, the irradiated iron was purified from⁶⁰Co and other radioactive nuclides by an anion exchange separation method and isopropyl ether extraction in hydrochloric acid. The amount of⁶⁰Co ingrowth was measured by -spectrometry using a Ge-detector coupled to a multichannel pulse height analyzer 4 years after the purification of iron. Neutron flux of the irradiation position was calculated from the amount of⁵⁵Fe produced. The observed value of 12.5±2.8 barn is slightly greater than reported value for burnup cross section of⁵⁹Fe(n, x)X, where x refers , , d, p and 2n, and X is any nuclide produced by the above reactions.     

Multitracer study on permeation of rare earth elements through a supported liquid membrane

Separation by means of supported liquid membranes is a useful method for the preparation and preconcentration of radioactive nuclides. The permeation of rare earth elements through a bis(2-ethylhexyl) hydrogen phosphate-decalin membrane supported on a microporous polytetrafluoroethylene sheet was studied using a multitracer containing radioactive nuclides of Sc, Zr, Nb, Hf, Ce, Pm, Gd, Yb, and Lu. Permeation rates of these elements from feed solutions of various acidity to receiving solutions of 0.5 mol·dm⁻³ HCl were determined simultaneously. The feed solution at pH 1.4 gave the highest permeation rate for Ce, Pm, and Gd, amounting to about 95% of permeation for Ce and Pm, 80% for Gd, and 10% for Yb in 21 h. Scandium, Zr, Nb, Hf, and Lu were not transported at all from the feed solution. Permeation rates of Yb and Lu from the feed solution at pH 1.4 to receiving solutions of 0.75, 1.0, 2.3, and 4.0 mol·dm⁻³ HCl increased with the concentration. The results obtained indicate that the light rare earth elements can be separated from the heavy ones by this method.     

Thorium ore analysis by X-rays in neutron activation analysis

The possibility of using characteristic X-rays from radioactive elements in activatio analysis was investigated during this work with particular emphasis on (n, ) products. The detection sensitivities for some elements are determined by X-rays employing a²³⁵Pu-Be neutron source. The technique has been applied to the analysis of thorium ores from the Anatolia Region, with great accuracy.     

Nuclear systematics: II. The cradle of the nuclides

The nuclear energy surface is presented as three-dimensional (3-D) plots of mass or atomic number versus charge density versus average energy per nucleon. These plots reveal a trough or cradle of the nuclides. Stable and long-lived nuclides are located in the valley. Those that are radioactive or are easily destroyed by fusion or fission occupy higher positions. Separate modes of nucleosynthesis fill the cradle from different directions and produce distinct occupancy levels, i.e., different abundance patterns. The cradle can be used to estimate the properties of nuclear matter that cannot be studied in the laboratory.     

Tracer packet: A new conception for the production of tracers

The concept of tracer packet, which can be defined as a group of carrier-free radioactive isotopes of few elements, which have been produced together with an objective to study some particular physical, chemical or biological systems has been introduced in this paper. The tracer packet can be produced with low projectile energy (5-7 MeV/u) contrary to the multitracer technique. A thick cobalt foil has been irradiated consecutively with ¹⁶O, ⁷Li and ¹²C beams to produce the tracer packet containing carrier free radiotracers of Mn, Cu, Zn, Ga, Ge, As and Se which after removal of bulk cobalt can be used for further studies of essential micro nutrient elements.     

Production of tracer packet of heavy and toxic elements

Tracer packet, a group of carrier-free radioactive isotopes of few elements which are produced together with an objective to study some particular physical, chemical or biological systems is a new conception over the century old tracer technique and a decade old multitracer technique. This paper describes the production of a tracer packet of heavy and toxic metals containing carrier-free radionuclides of some heavy and toxic elements like mercury, thallium, lead, bismuth and polonium produced by medium energy ⁷Li and ¹²C irradiation on gold target and subsequent separation of bulk gold from the carrier-free products.     

Screening of plant species for comparative uptake abilities of radioactive Co, Rb, Sr and Cs from soil

In case of radioactive fallout, persistence of long lived nuclides in soil and subsequent transfer into the food chain through plants over a long period is the key factor. The possibility of phytoremediation is suggested to reduce the radionuclides in soil. To exploit the natural potential of some plants in absorbing or accumulating certain radionuclides and depleting the soil radioactivity, thirty-two plant species were tested under laboratory conditions for their comparative ability in taking up radioactive Rb, Co, Sr and Cs. Broccoli and tomato for Co, tomato, chard, sunflower and cucumber for Rb; cucumber, sunflower and turnip (Kyona) for Sr, and tomato, chard and cucumber for Cs were found to be effective compared to other species tested.