Half-lives Of Isotopes Research Articles

Half-life measurements of 6He, 16N, 19O, 26F, 28Al, 77Senm and 110Ag

The half-life of different isotopes, activated by neutrons in the reactor R -0 by means of a pneumatic extent have been measured with a pulse height analyzer working in its multiscale mode of operation. A Nal(Tl)-scintillation spectrometer was used as detector. Least squares analysis calculated by the Mercury computer were performed for each measurement. The following weighted mean values of the half-lives are obtained: 6He, 0.862±0.017 sec; 36N, 7.31±0.04 sec; 3O, 29.1±0.3 sec; 20F, 11.56±0.05 sec; 28Al, 2.31±0.01 min; 77Senm, 18.83±0.04 sec; 110Ag, 34.42±0.14 sec.

Some techniques for the determination of isotopes of short half-life as applied to the activation analysis of beryllium: C. A. Baker, Atomic Energy Research Establishment, Harwell, U.K.

A technique suitable for the production of short-lived fission product halogens and rare gases is described. UO2 targets placed in a methane-filled chamber are irradiated in a neutron flux of 1011n/cm2·s in the thermal column of a Triga Mk II reactor. Iodine and bromine originating from the fission of 235U are brought to a gaseous phase through hot-atom reactions with methane. After the irradiation the radioactive gas mixture, which contains methyl halogenides, fission product rare gases and methane, is swept out of the reactor by a methane stream and transferred to chemical separation and counting apparatus. Gas transfer times shorter than 2 s can be achieved. The operation of the apparatus is fully automatised.The gamma spectra of the short-lived fission product isotopes produced with the aid of this device were investigated by means of a 20 cm3 Ge(Li) detector. Three new gamma lines were found. Transitions with energies 144.5±3.2 keV and 1223.0±3.9 keV and half-lives 1.7±0.25 s and 2.2±0.3 s, respectively, are supposed to belong to the isotope 92Kr. A 590.0±0.3 keV transition with half-life 6.9±2.4 s is tentatively assigned to the isotope 138I. A weak line at 1217±2 keV which was previously assigned to 137I1) was also seen.

Operational and system testing of SNAP III thermoelectric generator

Electrical performance of the SNAP III generator in a variety of environments has been defined accurately through test. A total of 2593 hr have been amassed during which these units have been subjected to the shock, acceleration and vibration fields anticipated during the boost phase of a satellite launching. Additional performance tests have provided voltage-amperage relationships with thermal input as the parameter in simulated space conditions. Ambient temperatures ranged from +70 to −100°F with the unit suspended in an evacuated chamber. A method developed to vary insulation conductivity with time provides a constant thermal input to the thermoelectric conversion unit. A constant electrical output is produced although the total thermal energy available decreases with time as a function of isotope half-life. An essential adjunct to performance definition has been determination of the safety of a radioisotope power unit in combination with a vehicle system. A brief summary of results of tests simulating the critical situations of any mission is presented.

Uranium migration and geochemistry of uranium deposits in sandstone above, at, and below the water table; Part 1, Calculation of apparent dates of uranium migration in deposits above and at the water table

The migration of U may be studied by the distribution of the radioactive daughter products, which serve as natural tracers in the migration of U. The distribution of the daughter products is determined by radiochemical analyses of samples from ore deposits in sandstone, and the apparent minimum and maximum dates of U introduction or redistribution may be calculated from the Pa 231 /Th 230 ratio. The primary assumption required is that the Pa and Th do not migrate in measurable quantities from the place where they were produced by the decay of the parent U isotopes. The upper limit of age determination is about 250,000 years, based on the half-lives of Pa 231 and Th 230 . The difference in the half-lives of these isotopes is reflected in their differential rates of growth and decay corresponding to migrations of the parent U during the time range considered. The growth and decay patterns, analyzed mathematically, are used to determine the apparent date of U migration. Calculations based on analyses of samples from the Hulett Creek area, Wyoming, illustrate the results for typical sandstone ore deposits that are above and at the water table.

Thallium isotopes 192 and 193

Half-lives of 192Tl and 193Tl have been determined by following the decay of conversion electron lines from mass separated sources in a β-spectrometer. From energy level systematics an (11·4 ± 1·4) min period is ascribed to a 7+ level in 192Tl; most likely the ground state has the same half-life within the limits of error. Predicted M4 isomers in 193Tl and 191Tl could not be confirmed. The ground state half-life of the former isotope was obtained as (22·6 ± 1·0) min, while that of the latter seems to be less than 10 min. An improved half-life of 191Au, (3·2 ± 0·1) hr, is reported.

New nucleide actinium-231

A new nucleide actinium-231 was identified from the reaction of Th 232(γ, p)Ac 231 induced by the 25-MeV bremsstrahlung. The activity was chemically separated from fission products with the aid of a recoil method. The half-life of this new isotope was found to be T 1 2 = 15±1 min and the end-point energy of the beta ray was E β = 2.1±0.1 MeV. Several weak gamma rays were also observed.

Protactinium-237

Protactinium-237 was produced from the reaction U238(γ,p)Pa237 by the 25-MeV bremsstrahlung. The activity produced was chemically separated with the aid of a recoil method from fission products. The half-life of this new isotope was found to be T12 = 39±3 main. The radiations were measured with a scintillation spectrometer. Three beta components were identified with the end-points of 2.30±0.05 MeV, 1.35 MeV, and about 0.8 MeV. Many gamma rays were also found. A decay scheme was constructed with the aid of Nilsson's unified model.

The half-lives of some short-lived isotopes

The half-lives of some short-lived isotopes

A graphical method for the determination of half-lives

Abstract The graphical determination of half-lives of radioactive isotopes can be made more accurate if the remaining number of counts, instead of the counting rate, is plotted as a function of time. This method has been used to measure the half-life of 27Si, for which the value 4.14±0.03 seconds has been obtained.

Demonstration of early renal uptake of potassium-42 by an autoradiographic method for water-soluble isotopes of short half-life.

STUDIES of the distribution of intravenously injected potassium-42 in rats have shown that the kidney takes up this cation from the plasma at considerably higher rates than does any other organ1,2. In the first few minutes after the injection, the specific activity in the renal tissues exceeds that of the plasma2,3. At 2 min., approximately 15 per cent1 and 10 per cent4 of the injected dose were found in rabbit kidneys and about 12 per cent (unpublished observations) in rat kidneys. These fractions are far greater than the expected equilibrium value. Analysis of these findings indicated that all the potassium arriving in the plasma in the kidney is exchanged with potassium from cells. Morel and Guinnebault have recently presented evidence that the renal cortex is the main site of this very rapid exchange3. From their experiments it appears that in the rabbit as much as 15 per cent of the total potassium present in the cortex is exchanged per minute. This was corroborated macroscopically by autoradiography in which X-ray films were exposed to 2-mm. thick frozen kidney slices. The resulting autoradiograms indicated that in the 5 min. following an intravenous injection, the intense activity emanated from a region roughly corresponding to the cortex.

Oak Ridge radioiodine (I131) for hyperthyroidism; tenth anniversary.

The United States Atomic Energy Commission first released radioiodine (I¹³¹) for general use in July, 1946. This material was made in the atomic pile at Oak Ridge. Investigations with the isotope were then initiated to determine the clinical value of the isotope in the diagnosis and treatment of hyperthyroidism, in addition to the studies in many other fields. Prior to this, radioiodine had been tried in the treatment of hyperthyroidism. Hertz and Roberts¹and later Chapman and Maloof²had available to them I¹³⁰, the 12-hour half-life isotope of stable iodine, made in the cyclotron. Hamilton and Lawrence³employed I¹³¹, the 8-day half-life isotope. Except for the few patients treated by Soley with these latter investigators, I¹³¹was not used further until the action of the Atomic Energy Commission; and at that time therapeutic interest in I¹³⁰virtually ceased. The highly successful initial

Half-Life and Radiations of the Long-Lived Isotope of Niobium (94Nb).

Half-Life and Radiations of the Long-Lived Isotope of Niobium (94Nb).

Spontaneous Fission Systematics

Previous correlations of spontaneous fission half-lives vs $\frac{{Z}^{2}}{A}$ predict that the half-lives of even-even isotopes increase with $A$. A deviation from the above correlation is discussed, and it is shown that the spontaneous fission half-lives of the even-even isotopes go through a maximum with increasing $A$. The shorter spontaneous fission half-lives beyond the maximum may be a result of the greater deformations of the larger-$A$ nuclides. Some comments are made on fission thresholds.

An Experiment Involving the Determination of the Half-Life of an Isotope

First Page

Evaluation of a thyroid panel; practical application of scintillation counter in diagnosis of diseases of the thyroid.

Since I 131 , the eight day, half-life isotope of iodine, became available on a large scale, its uptake by the thyroid gland has been used as a diagnostic test in the study of thyroid disorders. The thyroid uptake or diagnostic tracer study is generally afforded equal importance with the determination of serum protein-bound iodine (PBI), the basal metabolic rate, and the serum cholesterol level, the latter mainly in the diagnosis of hypothyroidism. Recent improvements in instrumentation and particularly the development of the sensitive, gamma detecting scintillation counter 1 have made possible the use of tracer amounts as small as one microcurie of I 131 for studying thyroid function. This amount is about one-hundreth of the dose that has been commonly used in the past and makes it possible, for the first time, to obtain repeat uptake values without exceeding a safe dosage level. This simple and reliable equipment, which is

Deuteron Bombardment ofC14

Bombardment of ${\mathrm{C}}^{14}$ by deuterons produces three nuclear reactions, yielding neutrons, $\ensuremath{\alpha}$-particles, and protons, and leads thereby to the formation of ${\mathrm{N}}^{15}$, ${\mathrm{B}}^{12}$, and a new radioactive isotope, ${\mathrm{C}}^{15}$. The half-life of this sixth isotope of carbon is 2.4 sec., and the end point of the $\ensuremath{\beta}$-ray spectrum lies at 8.8 Mev.Approximate values for relative yields from the various reactions are given, the neutron spectrum is obtained, and the nature of the $\ensuremath{\gamma}$-rays emitted during bombardment is reported.

Zur Frage nach dem Alter der Elemente

The abundance rules would probably allow the lower limit of the age of the elements to be more clearly defined if the half lives of long-lifed artificial isotopes, such as X129 Pd107 or Se79, were known with better accuracy. They would permit the upper limit for the age of the elements to be improved, if the abundance of bismuth were known with better accuracy. From the values of these quantities at present available not much can be said, except that it seems more probable than hitherto assumed, that the age of the elements lies between 4 and 5·109 years.

Radioactive Iodine: Its Use as a Tool in Studying Thyroid Physiology

IN 1915, MARINE and his associates (1-3) demonstrated that the thyroid is capable of concentrating iodine to an approximate level of 5,000 times that of the blood. This unique function has provided students of biology and medicine with a valuable means for studying the physiology of the thyroid. In recent years the physicists have provided dynamic tools, in the radioactive isotopes of iodine, with which certain functions of the thyroid can be investigated at physiologic levels never before obtained. Though several radioactive isotopes of iodine have been described, only three have been widely used in studies of thyroid function. The earliest studies with radioactive iodine were done with I128, an isotope having a half-life of only twenty-five minutes, which limited the time of study. This isotope is prepared by slow neutron bombardment of iodine. Iodine130; the twelve-hour half-life isotope, has been used in biological studies and in treating certain cases of Graves' disease. This isotope is a product of ...