Gamma-ray scanning of neutron activated geological sediments for studying elemental profile distributions

Gamma-ray scanning for application to elemental profile studies of geological samples was studied with a neutron activated Baltic Shield sediment. Profile distributions for seven elements were measured. The capabilities and limitations of gamma-ray scanning are discussed by comparing the results with profiles obtained after the mechanical subdivision of the sample and the activation of the appropriately sized separates.     

Production of75Br and77Br from enriched krypton: Excitation functions

Proton irradiation of enriched⁷⁸Kr and⁸⁰Kr to obtain⁷⁵Br and⁷⁷Br was investigated. Excitation functions of the different reactions involved are presented. Production methods for both bromine nuclides are briefly discussed.Supported by Kernforschungszentrum Karlsruhe GmbH, Eggenstein-Leopoldshafen.     

Optimization of instrumental neutron activation analysis for studying the chemical composition of silicate rocks

Software for optimization of instrumental neutron activation analysis of geological samples, preferentially silicate rocks, and a technique for evaluation and minimization of interference of gamma-ray lines are given. The maximum relevant signal-to-noise ratio was taken as a criterion for optimization by taking into account information available from a large number of lines in the gamma spectra studied.     

Optimization of instrumental neutron activation analysis for studying the chemical composition of silicate rocks

Software for optimization of instrumental neutron activation analysis of geological samples, preferentially silicate rocks, and a technique for evaluation and minimization of interference of gamma-ray lines are given. The maximum relevant signal-to-noise ratio was taken as a criterion for optimization by taking into account information available from a large number of lines in the gamma spectra studied. Received: 17 July 1997 / Revised: 7 November 1997 / Accepted: 16 November 1997     

Determination of the 238U spontaneous fission decay constant without neutron irradiation

We have developed a methodology for measuring the decay constant of the spontaneous fission of ²³⁸U, l_f, using nuclear particle track detectors where thermal neutron irradiation is unnecessary. This methodology is based on the fact that the radiation damage caused by spontaneous fission of trans-uranium elements bearing a mass number close to 238 are similar to ²³⁸U spontaneous-fission ones. Loading a thick source of uranium (thickness greater than the fission fragment range) with a small amount of a suitable trans-uranium element (for instance, ²⁴²Pu, which presents a spontaneous fission half-life of 6.75^.10¹⁰ y), it is possible to determine the observation efficiency of a particle-track detector for fission fragments. Procedures concerning our thick source manufacture and uniformity tests of the trans-uranium distribution are also presented. These results make it possible for the exposure of thick uranium sources (without trans-uranium element) to lead to a l_f value.     

A low cost spectrum multiscaling analyzer based on personal computer for studying the decay properties of short-lived nuclides

A low cost spectrum multiscaling analyzer system based on an IBM PC is described. Interrupt service routines were used to handle both the digital data converted by ADC and record the dead time profile. A dead time counter was provided to handle the dead time problem by counting the busy time of amplifier and ADC, which is important in correcting the decay rate of the short-lived nuclides during the counting interval.     

Spontaneous-fission decay constant of 238U measured by nuclear track techniques without neutron irradiation

A value of the decay constant for spontaneous fission of ²³⁸U, l_f, determined by particle-track detector techniques, is presented. The main source of systematic error in fission-track measurements of l_f, the so called neutron dosimetry, has been avoided. Instead of calibrating the neutron source and the usual mica detector through tracks of ²³⁵U fission induced by thermal neutrons, spontaneous-fission tracks and alpha-particle tracks of ²³⁸U and ²⁴²Pu were used. A value of l_f = (8.66±0.38)·10^-17 y^-1 has been obtained.     

Use of multivariate and neutron activation analysis on studying element interrelationships in Brazilian phosphorite

Methods to determine U, Th, and other constituent elements in mineral matrices through Instrumental Neutron Activation Analysis (INAA), have been widely utilized due to their capability to extract a large quantity of information from small samples. In the present work, an experimental methodology based on INAA associated to the cluster statistics technique was used to determine the uranium concentration and its correlation with other elements present in the mineral phosphorites from the northeast region of Brazil. Data for 22 elements including rare-earth elements are presented. A good correlation between uranium and rare-earth elements is observed. For the transition metals, correlation with uranium was not noted.     

Production of 177Lu by neutron activation of 176Lu

Production of the radiopharmaceutical nuclide ¹⁷⁷Lu, by direct thermal neutron activation of ¹⁷⁶Lu, poses a discrepancy between experimentally measured and theoretically predicted activities. It was found that in the irradiation at the pneumatic transfer tube (Rabbit) of the IRR-1 reactor, the exper./theor. ratio was 1.858± 0.051. This ratio was determined also by comparing the activities of ¹⁷⁷Lu and ^176mLu. The significant deviation of ¹⁷⁶Lu from the 1/v behavior explained this disagreement. The ratio exper./theor. is the Westcott g(T _n)-factor and was used to yield the neutron temperature T _n = 311±8 K.The assistance of Eyal Elish in performing the ICP-MS analyses of Lu is gratefully acknowledged.     

Production of 177Lu by neutron activation of 176Lu

Production of the radiopharmaceutical nuclide ¹⁷⁷Lu, by direct thermal neutron activation of ¹⁷⁶Lu, poses a discrepancy between experimentally measured and theoretically predicted activities. It was found that in the irradiation at the pneumatic transfer tube (Rabbit) of the IRR-1 reactor, the exper./theor. ratio was 1.858± 0.051. This ratio was determined also by comparing the activities of ¹⁷⁷Lu and ^176mLu. The significant deviation of ¹⁷⁶Lu from the 1/v behavior explained this disagreement. The ratio exper./theor. is the Westcott g(T _n)-factor and was used to yield the neutron temperature T _n = 311±8 K.The assistance of Eyal Elish in performing the ICP-MS analyses of Lu is gratefully acknowledged.     

Isomeric yield ratio of146La and84Br in thermal neutron induced fission of235U

The independent isomeric yield ratio of¹⁴⁶La and⁸⁴Br in the thermal neutron fission of²³⁵U is reported for the first time with the values of 0.058±0.017 and 0.62±0.20, respectively. the yields have been determined using a fast radiochemical separation technique followed by -spectroscopy. The deduced rms angular momentum of⁸⁴Br is 5.9 from the statistical model analysis and the rms angular momentum of¹⁴⁶La is found too low to be determined.     

Rate coefficient for the reaction: Br+Br2O→Br2+BrO

The room temperature rate coefficient for the reaction Br+Br₂O→Br₂+BrO (3) has been measured using the technique of pulse-laser photolysis with long-path transient absorption detection of the BrO reaction product. A value of k₃=(2.0±0.5)×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ was determined. The photolysis products of Br₂O at 308 nm were also examined. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 571–576, 1998     

Optimization of Linac-based neutron source for thermal neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - A 20 MeV electron Linac based neutron beam has been shaped for neutron activation analysis (NAA) technique. A beam shaping assembly (BSA)...     

A Simple and Rapid Method for the Preparation of 87Y/87mSr Generator

A simple and efficient process for the preparation of ⁸⁷Y/^87mSr generator with adsorption chromatography on -Fe₂O₃ was developed. A 0.25 g pallet of natural SrCl₂ was employed as a solid target which was irradiated at INER TR30/15 cyclotron. After irradiation the target was dissolved into a saline solution and adjusted with HCl/NaOH to a pH of 6.3. This solution was then passed directly through the column (1 cm×4 cm), loaded with appropriate amounts of -Fe₂O₃, at a flowrate of 1.0 ml/min for adsorption of ⁸⁷Y. Nonradioactive Sr was unadsorbed and washed out from the column. Above 90% of the available ^87mSr with a ⁸⁷Y breakthrough less than 10^–3% could be obtained with 10 ml of 0.9% saline solution per elution from the generator system. The chemical contaminants of Fe and Sr in the eluates were found below 0.04 and 0.1 ppm, respectively.     

Instrumentation for neutron spectroscopy

The basic principles of operation of most types of neutron spectrometers used by chemists are reviewed. The merits and constraints of each type is explained in terms of energy range, resolution, data rate and momentum transfer range so that the reader can understand why particular experiments are, or are not, done.