scholarly journals First direct determination of the 93Mo half-life

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
I. Kajan ◽  
S. Heinitz ◽  
K. Kossert ◽  
P. Sprung ◽  
R. Dressler ◽  
...  
Keyword(s):  
Half Life ◽  
Liquid Scintillation ◽  
Specific Activity ◽  
High Resolution Mass Spectrometry ◽  
Direct Determination ◽  
Chemical Separation ◽  
Decontamination Factor ◽  
Nuclear Facilities ◽  
Analysis Techniques

AbstractThis work presents the first direct measurement of the 93Mo half-life. The measurement is a combination of high-resolution mass spectrometry for the determination of the 93Mo concentration and liquid scintillation counting for determining the specific activity. A 93Mo sample of high purity was obtained from proton irradiated niobium by chemical separation of molybdenum with a decontamination factor larger than 1.6 × 1014 with respect to Nb. The half-life of 93Mo was deduced to be 4839(63) years, which is more than 20% longer than the currently adopted value, whereas the relative uncertainty could be reduced by a factor of 15. The probability that the 93Mo decays to the metastable state 93mNb was determined to be 95.7(16)%. This value is a factor of 8 more precise than previous estimations. Due to the man-made production of 93Mo in nuclear facilities, the result leads to significantly increased precision for modelling the low-level nuclear waste composition. The presented work demonstrates the importance of chemical separations in combination with state-of-the-art analysis techniques, which are inevitable for precise and accurate determinations of nuclear decay data.

scholarly journals Dating of Polar Ice By 32Si

1973 ◽  
Vol 12 (66) ◽  
pp. 411-416 ◽  
Author(s):  
Henrik B. Clausen
Keyword(s):  
Half Life ◽  
Specific Activity ◽  
Greenland Ice Sheet ◽  
Cosmic Ray ◽  
Polar Ice ◽  
Poor Knowledge ◽  
The Poor ◽  
Glacier Ice ◽  
Cosmic Ray Flux

32Si dating of glacier ice has hitherto been complicated by the poor knowledge of the half life. Furthermore, fall-out of bomb-produced 32Si impedes the determination of the specific activity of cosmic-ray produced 32Si in recent precipitation. Measurements on well-dated pre-bomb samples from the Greenland ice sheet establish a calibration for 32Si dating of up to 1 000 year old polar ice samples of the magnitude of 1 metric ton. If the technique is used on temperate glaciers, samples of pre-bomb deposits (or from after 1970) must be collected for comparison with samples of old ice, using an apparent half life of 295±25 years. Due to secular cosmic-ray flux variations, the true half life of 32Si is estimated at the slightly higher value of 330±40 years.

Determination of the specific ?-activity and the half-life of U233

Atomic Energy ◽  
1960 ◽  
Vol 6 (1) ◽  
pp. 41-41
Author(s):  
Ya. P. Dokuchaev ◽  
I. S. Osipov
Keyword(s):  
Half Life ◽  
Specific Activity

DEFINITIVE IDENTIFICATION OF MICROQUANTITIES OF RADIOACTIVE STEROIDS BY RECRYSTALLIZATION TO CONSTANT SPECIFIC ACTIVITY

1965 ◽  
Vol 49 (2_Suppl) ◽  
pp. S7-S77 ◽  
Author(s):  
Leonard R. Axelrod ◽  
Charles Matthijssen ◽  
Joseph W. Goldzieher ◽  
Jean E. Pulliam
Keyword(s):  
Liquid Scintillation ◽  
Specific Activity ◽  
Inorganic Materials ◽  
Dual Isotope ◽  
Advantages And Disadvantages ◽  
Yield Values ◽  
Solvent Systems ◽  
Identification Techniques ◽  
Constant Specific Activity

ABSTRACT Studies of steroid metabolism using isotopically-labeled compounds at physiological levels present unique problems in the identification of the metabolites and in the demonstration of their radiochemical purity. The submicrogram quantities of material available preclude the use of classical identification techniques. The character of the evidence obtained, the advantages and disadvantages of chromatographic and countercurrent distribution methods are discussed. Crystallization to constant specific activity is a recognized method for demonstrating that a substance is not radiochemically impure. Its parameters have never been accurately defined. Its true power is achieved only when it is preceded by extensive purification of the material to be characterized. In this way, the unknown material is first categorized by its migration rate in various solvent systems, and then by its crystalline identity with the carrier compound. The likelihood of two dissimilar steroids being both isopolar and isomorphic is held to be remote. Liquid scintillation spectrometry and gravimetry are the techniques used for the determination of constant specific activity. This method for measurement of radioactivity is extremely flexible, sensitive, and lends itself to dual-isotope experiments. Gravimetry under standardized conditions is suitably precise and much more generally applicable than spectroscopic quantitation. The parameters of the technique of rapid, forced microcrystallization are analyzed. In particular, the problem of contamination of crystals is analyzed in detail, and it is pointed out that classical concepts of purification by crystallization, developed chiefly in connection with ionic inorganic materials, must be modified when applied to nonionic steroid compounds. A mathematical analysis of the errors inherent in this technique indicates that 3 successive crystallizations of a pure radioactive compound should yield values for the specific activity which are within ± 5 % of the average of the 3 values.

Half-Life Determination of 41Ca and Some Other Radioisotopes

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 436-446 ◽  
Author(s):  
Walter Kutschera ◽  
Irshad Ahmad ◽  
Michael Paul
Keyword(s):  
Mass Spectrometry ◽  
Electron Capture ◽  
Half Life ◽  
Specific Activity ◽  
Low Energy ◽  
X Rays ◽  
Weighted Mean ◽  
Electron Capture Decay

We have performed a new determination of the half-life of 41Ca by measuring the specific activity of an enriched Ca material with known 41Ca abundance. We measured the activity via the 3.3-keV X-rays emitted in the electron capture decay of 41Ca, and the 41Ca abundance was measured by low-energy mass spectrometry. The result, t1/2 = (1.01 ± 0.10) × 105 yr, agrees with the recent ‘geological’ half-life of Klein et al., (1991), t1/2 = (1.03 ± 0.07) × 105 yr, and with the corrected value of Mabuchi et al. (1974), t1/2 = (1.13 ± 0.12) × 105 yr. We recommend the weighted mean of these three measurements, t1/2 = (1.04 ± 0.05) × 105 yr, as the most probable half-life of 41Ca. We also discuss the situation of the radioisotopes, 32Si, 44Ti, 79Se and 126Sn, whose half-lives, though still uncertain, are potentially interesting for future AMS studies and other applications.

Direct determination of the specific activity of RNA uniformly labeled with 32P

1987 ◽  
Vol 162 (2) ◽  
pp. 521-528
Author(s):  
David M. Mueller ◽  
Godfrey S. Getz
Keyword(s):  
Specific Activity ◽  
Direct Determination

Improvements in the determination of the turnover rate of plasma thyroxine in avian species: application to the Japanese quail

1987 ◽  
Vol 114 (2) ◽  
pp. 191-198 ◽  
Author(s):  
E. J. Cookson ◽  
J. Glover
Keyword(s):  
Japanese Quail ◽  
Half Life ◽  
Turnover Rate ◽  
Specific Activity ◽  
Simple Procedure ◽  
High Specific Activity ◽  
Future Application ◽  
Sodium Thiocyanate ◽  
Plasma Samples

ABSTRACT The disappearance of the thyroid hormone thyroxine (T4) from plasma in fully grown male Japanese quail can be described as a first order process with a rate constant of 0·178 ± 0·013/h (mean±s.e.m., n = 8), which represents a half-life of 3·90 h. A small amount of [125I]T4 in relation to total circulating T4 was injected i.v. into Japanese quail and plasma samples were taken at appropriate time-intervals for the determination of residual plasma radioactivity. The rate of disappearance of [125I]T4 was subsequently equated to the turnover rate of the endogenous hormone. Previous methods were modified to overcome problems arising from possible disturbance of plasma T4 metabolism, recirculation of radiolabelled iodide, and to purify the [125I]T4 from the plasma samples. By using labelled T4 of very high specific activity, the amount of [125I]T4 administered was kept much smaller than has been used in previous studies on Japanese quail, thus limiting any interference with plasma T4 dynamics. To minimize any disturbance of plasma T4 metabolism, only four blood samples were taken, at three-hourly intervals after the injection of [125I]T4. The rapid turnover of T4 produced a large amount of labelled inorganic iodide, the re-entry of which into the plasma T4 pool was inhibited by s.c. administration of sodium thiocyanate 1 h before injection of[125I]T4. Assay of the true [125I]T4 turnover was significantly improved over that used in previous studies by purifying the [125I]T4 from the plasma samples chromatographically. The samples were applied to small Sephadex G-25 columns with sodium hydroxide (0·1 mol/l) as the eluant. This simple procedure clearly separated the [125I]T4 from the other radioiodinated plasma components such as free iodide, non-hormonal iodinated proteins and triiodothyronine (T3), thus enabling a more accurate assessment of the residual labelled T4 concentration in the plasma and hence the T4 half-life. The future application of this method to the study of plasma T4 turnover under various experimental conditions is discussed and the possible involvement of T4 turnover studies in the assessment of T4 to T3 conversion is considered. J. Endocr. (1987) 114, 191–198

Half-life of rhenium: geologic and cosmologic ages

1984 ◽  
Vol 62 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Stanley N. Naldrett
Keyword(s):  
Organic Compound ◽  
Decay Rate ◽  
Liquid Scintillation Counting ◽  
Half Life ◽  
Liquid Scintillation ◽  
Scintillation Counting ◽  
Beta Emission

The transition by beta emission of 187Re to 187Os would offer an attractive method of determining geologic and cosmologic ages if the decay rate of 187Re was known. An improvement in the determination of the decay rate has been accomplished using an organic compound of rhenium in liquid scintillation counting that is monitored by standards of other pure beta emitting isotopes. The half-life of 187Re is estimated to be (3.5 ± 0.4) × 1010 yr.

A rapid method for determining the specific activity of methylene-14C citric acid in cell extracts

1969 ◽  
Vol 47 (12) ◽  
pp. 1137-1140 ◽  
Author(s):  
B. T. Hodgson ◽  
J. G. Aldous ◽  
A. H. Patterson
Keyword(s):  
Citric Acid ◽  
Rapid Method ◽  
Spectrophotometric Method ◽  
Liquid Scintillation ◽  
Specific Activity ◽  
Cell Extracts ◽  
Large Numbers

The microchemical spectrophotometric method for the determination of citric acid has been found to be sufficiently specific to permit its use for the measurement of specific activity, provided the labelling occurs in the noncarboxyl carbon atoms of the molecule. The simplicity of the method permits determinations to be carried out simultaneously on large numbers of samples especially if liquid-scintillation techniques are employed for the measurement of radioactivity.

Sign in / Sign up

Export Citation Format

Share Document