Half-lives Of Isotopes Research Articles

Study of iodine migration in zirconia using stable and radioactive ion implantation

The large uranium fission cross section leading to iodine and the behaviour of this element in the cladding tube during energy production and afterwards during waste storage is a crucial problem, especially for 129I which is a very long half-life isotope ( T = 1.59 × 10 7yr). Since a combined external and internal oxidation of the zircaloy cladding tube occurs during the reactor processing, iodine diffusion parameters in zirconia are needed. In order to obtain these data, stable iodine atoms were first introduced by ion implantation into zirconia with an energy of 200 keV and a dose equal to 8 × 10 15at cm −2. Diffusion profiles were measured using 3 MeV alpha-particle Rutherford Backscattering Spectrometry at each step of the annealing procedure between 700°C and 900°C. In such experiments a reduced iodine concentration was observed, which correlated to a diffusion-like process. Similar analysis has been performed using radioactive 131I implanted at a very low dose of 10 9 at cm −2. In this case the iodine release is deduced from gamma-ray spectroscopy measurements. The results are discussed in this paper.

Biodistribution of 111In-labelled SCN-bz-DTPA-BC-2 MAb following loco-regional injection into glioblastomas.

We analyzed the biodistribution of the 111In-labelled murine anti-tenascin-C MAb BC-2 after intralesional injection in 15 glioblastoma patients. The activated ligand DTPA was conjugated via the isothiocyanato-benzyl group onto BC-2. Conjugates were labelled with 111In, displaying immunoreactivity greater than 90% and labelling efficiency of 99 +/- 1%. In contrast to i.v. injections, excellent tumor uptake was obtained by direct intralesional injection of conjugates that showed only slow systemic release. In serum, conjugates were found to be intact; in urine, only low-molecular-weight decay products were detected. In 8 patients, outflow from the site of injection into systemic circulation was low; daily activity in the serum and urine was found to be below 2% of the total injected radioactivity; most of the injected activity was retained within the tumor, resulting in effective half-lives of 58 +/- 5 hr. In contrast, higher outflow up to 10% of regionally injected 111In-DTPA-BC-2 MAb into systemic circulation resulted in considerable shortening of the effective half-lives to 20 to 40 hr in 7 patients. This outflow was found to correlate with tumor size and blood/brain barrier disruption. In one patient, HPLC analysis of tumor cyst fluid 3 and 6 days after intralesional injection revealed conjugates to be intact and allowed the estimate of about 70% of the total injected 111In-DTPA-BC-2 to be confined to tumor tissue. We conclude that different outflow patterns can be observed following locoregional injection of 111In-DTPA-BC-2, leading to considerable variations in the effective half-lives of isotopes within the tumor, requiring adjustment of the radiation dose in therapeutic trials.

Intestinal absorption of trace amounts of aluminium in rats studied with 26aluminium and accelerator mass spectrometry.

1. Until recently studies of intestinal aluminium absorption used pharmacological amounts of stable 27Al. 2. To examine the intestinal absorption of trace amounts of different chemical compounds of aluminium, in the present study we have employed the long half-life isotope of aluminium, 26Al, and accelerator mass spectrometry. Trace amounts of 26Al (2.7-12.1 ng) as the hydroxide, citrate, citrate plus 1 mmol/kg sodium citrate, or maltolate respectively, were administered to four groups of rats (n = 9 per group) by gavage. Blood and urine samples were collected for 5 h and the 26Al content (as a percentage of the administered dose) determined by accelerator mass spectrometry. 3. The 5 h urinary 26Al excretion amounted to 0.1 +/- 0.02, 0.7 +/- 0.2, 5.1 +/- 1.5 and 0.1 +/- 0.1% of administered dose in the four groups respectively. There was a strong positive correlation between peak plasma 26Al (r = 0.98) and urinary 26Al excretion in individual animals (P < 0.001). 4. We conclude that the fractional intestinal absorption of trace oral doses of aluminium hydroxide is at least 0.1% (compared with the previous estimate of 0.01% using large 27Al oral loads). Absorption of aluminium citrate given alone is significantly greater (0.7%) and is further increased to 5% by the accompanying sodium citrate, consistent with an enhancing effect of added citrate upon mucosal aluminium permeability. Aluminium maltolate absorption approximates that of aluminium hydroxide (0.1%).

Radiostrontium-90 (90Sr) Ultra-Traces Measurements by Coupling Ionic Chromatography (HPIC) and on Line Liquid Scintillation Counting (OLLSC)

The important role of the beta emitter Strontium-90 in our environmental has been studied since the nuclear age. This long half-life isotope (28.1 years) is produced in a relatively high yield (5.8 % from Uranium-235) during the fission of heavy elements. It has been reported to be the major artificial source of internal irradiation of the human body. Its valence shell electron configuration is the same as Calcium and so this isotope is easily fixed in the bones. The classical analysis of this particular isotope requires several weeks since it produces Yttrium-90 which is also a beta emitter. We developed a new trace analysis method by coupling High Performance Ionic Chromatography (HPIC), to separate Strontium-90 from natural or power plant reactor water, and on-line liquid scintillation counting detector, measuring the beta emission of low concentration Strontium-90 before Yttrium-90 is formed in a significant amount. We report here some analysis parameters : HPIC setup, scintillation cocktail, window, counting efficiency, linearity, pre-concentration and detection limits. We were able to determine very low concentrations of Strontium-90. The minimum concentration detected without a pre-concentration system was 0.5 ppt from a 200 µL sample (6.3×10-12 mole/L). The analysis only requires a few hours.

Modelling of short-lived fission product release behaviour during annealing conditions

An analytical model has been developed to calculate the post-irradiation release of short-lived fission gases during high-temperature reactor accident conditions. The generalized treatment accounts for a time-dependent diffusivity, and is shown to reduce to the standard Booth diffusion model when the isotopic half-life is much longer than the anneal period. The present formalism is further extended to include the case where a steady-state fission product distribution has developed for the radioactive species in the fuel grain during an irradiation prior to the anneal. More tractable analytic formulas for analysis are also provided as short and long-time approximate solutions.

Fission Cross-Section Measurements of the Odd-Odd Isotopes 232Pa, 238Np, and 236Np

Transmutation of actinide waste into fission products could be enhanced by using resonance fission of odd-odd target materials; those of interest are 232Pa, 238Np, and 242Am. Fission cross-section measurements of two of these short-lived materials were performed at Los Alamos National Laboratory. Samples were produced by the (d,2n) reaction in the Los Alamos Ion Beam Facility followed by fast radiochemistry to separate the odd-odd target of interest. The fission cross section of the nanogram samples was measured in a high intensity pulsed neutron beam produced by 800-MeV proton spallation. Using this procedure, the fission cross sections of the 1.3-day 232Pa and 2.1-day 238Np were successfully measured in the energy range from 0.01 eV to 50 keV. The fission cross section of the relatively long-life isotope 236Np was also measured in the same system while the short half-life isotopes were being prepared. The results and resonance analysis are presented.

Natural Controls on NORM in Produced Water from Texas Reservoirs

Abstract Naturally occurring radioactive materials (NORM) in produced water; sludge, and scale from Texas oil, gas, and geothermal wells increase concerns for worker safety as well as costs for handling and disposal. We combined published data, new analyses, and geochemical modeling to explore geologic, geochemical, and geographic controls on this radioactivity. NORM are caused primarily by 226Ra and 228Ra, the alpha-decay products of 238U and 232Th, respectively, in water and barite (BaSO4) scale. Local variations in reservoir lithology are a major control on NORM levels because of the geologically short half-lives of the Ra isotopes, slow basinal fluid-flow velocities, short transport distances during reservoir production, and the naturally heterogeneous distribution of U and Th in reservoir rocks. High salinity in produced water primarily controls Ra mobility in solution. Formation water composition and reservoir temperature determine the type and amount of scale that can form. Scale mineralogy and Ra/Ba and Ba/SO4 solute ratios in turn determine the Ra activity of scale. Analysis of our data base reveals several associations of NORM activity with reservoir and formation water characteristics. These associations can be used to predict NORM levels at the play, field, and reservoir scale.

Uptake and release kinetics of134Cs by Goldfish (Carassius auratus) and137Cs by Zebra Fish (Brachydanio rerio) in controlled aquatic environment

The uptake and release kinetics of134Cs by Goldfish (Carassius auratus) and137Cs by Zebra Fish (Brachydanio rerio) from aquatic media of different ionic compositions and temperature was studied in controlled laboratory conditions. The accumulation of radiocesium in the case ofBrachydanio rerio is observed to be strongly dependent on the potassium ion concentration of the aquatic medium, but in the case ofCarassius auratus this dependence is quite weak. The biological half-lives of the cesium isotopes incorporated into the fish investigated in the present work vary from 19 to 80 days and are influenced by the temperature and the ionic composition of the aquatic medium.

Zero-field splitting of Cm3+ in LuPO4 single crystals.

Electron-paramagnetic-resonance (EPR) spectroscopy has previously been employed in investigating excited levels of the ground-state manifold of the 5${\mathit{f}}^{7}$-configuration ion ${\mathrm{Cm}}^{3+}$ diluted in single crystals of the tetragonal-symmetry, zircon-structure hosts ${\mathrm{LuPO}}_{4}$ and ${\mathrm{YPO}}_{4}$. The three intradoublet resonances that were observed in these earlier studies, however, were significantly broadened due to radiation damage arising from the use of the 18.1-yr half-life isotope $^{244}\mathrm{Cm}$. In the present work, the isotope $^{248}\mathrm{Cm}$ (${\mathit{T}}_{1/2}$=3.4\ifmmode\times\else\texttimes\fi{}${10}^{5}$ yr) with a significantly lower specific activity has been incorporated in ${\mathrm{LuPO}}_{4}$-host single crystals in order to reduce the internal radiation-induced damage that can broaden both EPR and optical transitions. By employing these $^{248}\mathrm{doped}$ ${\mathrm{LuPO}}_{4}$ samples, it has been possible to observe an additional interdoublet transition for ${\mathrm{Cm}}^{3+}$, to perform more accurate measurements of the various intradoublet transitions at higher microwave frequencies, and to obtain optical absorption and fluorescence data for this system. These EPR and optical results have led to a more complete and accurate determination of the energy-level structure of ${\mathrm{Cm}}^{3+}$. Additionally, it has been possible to detect magnetic resonance transitions for the ${\mathrm{Cm}}^{3+}$ ion at room temperature.

Cryogenic micro-calorimeters for low energy beta spectroscopy

We are using calorimeters with completely encapsulated sources to study low energy beta spectra. Our devices work as true calorimeters in the sense that they totally absorb and sum all the various quanta released in a decay into a single temperature pulse with amplitude proportional to the total energy deposited. We use a neutron transmutation doped (NTD) germanium thermistor as the temperature sensor and superconducting NbTi leads, which form a weak thermal link to the cold stage (≈80 mK). We have been using superconducting tin as our absorber material, and we discuss various techniques for source and absorber preparation. Annealing the absorber leads to shorter pulses with larger amplitude, and significantly improves detector performance. The production of a device to study the beta decay of107Pd presented special difficulties due to the low specific activity of this isotope (halflife 6.5×106 y), and the low enrichment (15%) that was available. This meant it was necessary to incorporate a large amount of palladium into our tin absorber. We found we could avoid a corresponding increase in heat capacity by forming a superconducting PdSn alloy.

Microscopic Predictions of β +/EC-Decay Half-Lives

Beta-decay half-lives for β +/EC (electron capture) decay for neutron-deficient nuclei with atomic numbers Z = 10-108 have been calculated up to the proton drip line. For this purpose a proton-neutron quasiparticle random-phase approximation model (pn-QRPA) has been used. Both particle-hole and particle-particle residual interactions are taken into account. The calculated half-lives are in good agreement with experimental data, indicating the applicability of the model to the prediction of half-lives of unknown isotopes. The results of the present calculation are also compared to earlier theoretical work. It is shown that the pn-QRPA leads to considerable improvement over gross theory calculations.

Nuclear Data Measurements for Yttrium Isotope Used for Activation Analysis and Neutron Metrology

In order to establish more accurate nuclear data for the yttrium isotope 89Y, joint experimental work has been conducted in four greatly different thermal-to-epithermal neutron flux ratios (Qth/Qepi). After carefully calibrating the neutron spectra in the irradiation channels used, nuclear constant K0, Ke,0 and Q0 remeasured and found to be: for E=202.5 keV K0=2.33×10-5 (1.9%), K0 according to the Cd-subtraction method=2.31×10-5 (1.7%) and Ke,0=8.76×10-6 (2%) for E=479.5 keV K0=2.19×10-5 (2%), K0 according to the Cd-subtraction method=2.18×10-5 (1.9%), and Ke,0=8.30×10-6 (2%) and Q0=6.20 (2.1%). The relevant effective resonance energies Ēr have been recalculated using the latest BNL neutron resonance parameters yielding Ē;r (89Y)=4302 eV (7%). The half life of the 90mY isotope has also been remeasured to give T1/2 (90mY)=3.185 h (0.5%) with 1σ limit.

PILIS: Post-ISOCELE Laser Isobar Separation — a high efficiency apparatus for laser spectroscopy

A new experimental setup PILIS II has been installed on line with the ISOCELE isotope separator (IPN, Orsay). The mass-separated ions are slowed from 30 kV to 500 V and implanted on a graphite collecting disk. The atoms are then thermally desorbed at the implantation region by Nd-YAG laser pulses and selectively ionised by three laser beams. The ions created are mass identified by a time-of-flight (TOF) system. Two versions of the TOP system with accelerating voltage of 1.5 and 30 kV were used to carry out hyperfine structure measurements. With the 30 kV system we obtained an overall detection efficiency of 8.4 × 10 −5. First measurements were performed on very light gold isotopes. It has been shown that PILIS II is well adapted to study very short half-life isotopes ( T 1 2 ∼ 1 s ).

PILIS: post-ISOCELE laser isobar separation; a high efficiency apparatus for laser spectroscopy

A new experimental setup PILIS II has been installed on-line with the ISOCELE isotope separator (IPN, Orsay). The mass-separated ions are slowed from 30 kV to 500 V and implanted on a graphite collecting disk. The atoms are then thermally desorbed at the implantation region by Nd: YAG laser pulses and selectively ionized by three laser beams. The ions created are mass identified by a time-of-flight (TOF) system. Two versions of the TOF system with accelerating voltages of 1.5 and 30 kV were used to carry out hyperfine structure measurements. With the 30 kV system we obtained an overall detection efficiency of 1.4 × 10 −5. First measurements were performed on very light gold and platinum isotopes. It has been shown that PILIS II is well adapted to study very short half-life isotopes ( T 1 2 ∼ 1 s ).

Identification of the rare neutron-rich isotope 117Rh.

In this paper we wish to report on the first observation of the beta decay of the very neutron-rich nucleus $^{117}\mathrm{Rh}$. It was produced via 23 MeV proton induced fission of $^{238}\mathrm{U}$ using the ion guide set-up of the LISOL separator. A beta half-life of 0.44\ifmmode\pm\else\textpm\fi{}0.04 s was measured for this nucleus from the decay of the beta-coincident K x rays of Pd. The half-lives of neutron-rich Rh isotopes are compared with the newest model calculations. Three gamma rays of 34.6, 131.7, and 481.6 keV were found to be associated with the decay of $^{117}\mathrm{Rh}$. Its proposed beta decay scheme and the decay of the recently discovered 19 ms isomer in $^{117}\mathrm{Pd}$ imply spin and parity of 11/${2}^{\mathrm{\ensuremath{-}}}$ for the isomer fed directly in fission.

Description of the ground-state pionic double charge exchange reaction on 128,130Te

The pionic double change exchange reactions 128,130Te( π +, π −) 128,130Xe are investigated within the proton-neutron random-phase approximation. The approach is fpund to give a satisfactory agreement of the calculated differential cross sections and angular distributions with recent data. A strong dependence of the calculated quantities on the strength g pp of the particle-particle force is observed. This behaviour is similar to that reported for the β + decay in neutron-dificient nuclei and the double beta decay. The role of the DCX for the interpretation of the ratio of the double beta decay half-lives of the tellurium isotopes is discussed.

A cumulative count method for determining the half-life of barium-137 and gallium-68 radioactive isotopes: A spreadsheet application

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA cumulative count method for determining the half-life of barium-137 and gallium-68 radioactive isotopes: A spreadsheet applicationElvin Hughes Cite this: J. Chem. Educ. 1991, 68, 2, A41Publication Date (Print):February 1, 1991Publication History Received3 August 2009Published online1 February 1991Published inissue 1 February 1991https://doi.org/10.1021/ed068pA41RIGHTS & PERMISSIONSArticle Views180Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

The Use of the 11 C Technique to Measure Plant Responses to Herbivorous Soil Nematodes

An advantage of the short half-life (20_3 min) isotope method is the simultaneous measurement of several crucial plant processes without hindering or destroying whole-plant function. The technique was used to examine the effects of the herbivorous soil nematode, Meloidogyne javanica (Treub) Chitwood, on carbon assimilation and redistribution in tomato (Lycopersicum esculentum L.) and in two ecotypes [grazing adapted (GA) and non-grazing adapted (NGA)], of an African C4 grass, Panicum coloratum L. Preliminary tests, based on nematode eggs and galls, showed that M. javanica reproduced differentially on both P. coloratum ecotypes and suppressed GA shoot growth (weight), but had little effect on fresh root weight. In tomatoes, control plants had a higher pool of labile C in the roots than the nematode-infected plants. With P. coloratum, there were no differences in parameters between ecotypes. Plants with herbivorous nematodes had a lower stem sink activity, root activity and root transport speed than control plants. The technique proved valuable for measuring instantaneous changes in photosynthate accumulation and movement induced by herbivorous soil nematodes. Key-words: Carbon allocation, phytophages, root herbivory, soil nematodes

PRODUCTION, STRUCTURE AND DECAY OF HYPERNUCLEI

PRODUCTION, STRUCTURE AND DECAY OF HYPERNUCLEI

Beta-decay half-lives of neutron rich Cu and Ni isotopes produced by thermal fission of235U and239Pu

The half-lives of very neutron rich isotopes of Ni and Cu have been measured. The isotopes are produced in very asymmetric thermal fission of235U and239Pu at the I.L.L. high flux reactor. They are separated by means of the Lohengrin spectrometer. They are identified with aΔE-E ionization chamber and implanted in one of the 8 Si planar detectors where theβ-particles are also detected. The time correlations between the implantation and the detection ofβ-particles provide the half-life. The values obtained are compared to current theoretical predictions.