Wu Shao-Yong

Determination of the half-life of 79Se with the accelerator mass spectrometry technique

Abstract In the recent charts of the nuclides an accepted half-life of 79 Se is only an upper limit, 4 a. In this paper, we report a measurement of the half-life of 79 Se. The number of 79 Se atoms was determined from measured 79 Se Se ratios with the accelerator mass spectrometry technique and the decay rate of 79 Se was determined by counting the emitted β-rays with a liquid scintillation spectrometer. The half-life of 79 Se was measured to be (1.1 ± 0.2) × 10 6 a. We have also re-examined the 79 Se half-life value in the recent charts, which has been reported in Ref. [1], and have found that from the data related to the calculation of the half-life the upper limit of the half-life was re-calculated to be 6.5 × 10 5 a, other than 6.5 × 10 4 a as reported in the original paper in which a mistake could be made in the calculation.

Remeasurement of the Half-Life of 79Se with the Projectile X-Ray Detection Method

Remeasurement of the half-life of 79Se has been carried out with projectile x-ray detection (PXD) in accelerator mass spectrometry. We made two major improvements over our earlier 79Se half-life determination [Nucl. Instrum. Methods B 123 (1997) 403]. Firstly, the PXD technique has been used for separation of 79Se and 75Se from 79Br and 75As isobars respectively. Secondly, the half-life of 79Se has been measured relative to the known precise half-life of 75Se(119.79±0.04 d). A more reliable half-life of 79Se measured with the PXD technique is (2.95±0.38)×105 y, about a factor of one third lower than the previous value, 1.1 × 106 y. The problems in the previous measurement are discussed.

AMS Measurement of 53 Mn at CIAE

The long-lived isotope 53Mn cosmogenically produced in situ is a very useful indicator for geochronological dating. A new 53Mn accelerator-mass-spectrometry (AMS) measurement method is developed based on the HI-13 Tandem Accelerator and ΔE-Q3D detection system at China Institute of Atomic Energy. The performance of 53Cr isobar separation and suppression is tested by a series of 53Mn standards and commercial MnO samples. The results show that the ΔE-Q3D detection system brought about an overall suppression factor of more than 107 for the interfering isobar 53Cr.

Methodological Study on AMS Measurement of U Isotope Ratios in Nanogram U Samples

The determination of uranium isotopic composition in trace samples is important in different fields. A new measurement method that uses an accelerator mass spectrometry (AMS) technique has been developed for the analysis of uranium isotopic ratios in ultra-trace uranium samples at the China Institute of Atomic Energy. As a result, about 5-nanogram level uranium samples analyzed with AMS is achieved.

Methodological Study on Change in Half Life of 210Po Embedded in a Metallic Medium at Ultra-Low Temperature

It has been claimed that the half-life of radioactive nuclides embedded in metals may be significantly affected by the screening of quasi-free electrons provided by the metals, especially at the cryogenic temperature. We determine the α-decay half-life values of 210Po in high purity metallic bismuth at 4.2 K and 293 K. The results show that the α-decay half-life of 210Po at T = 4.2 K is about (24 ± 8)% shorter than that at room temperature.

Progress in AMS Measurement of 182Hf at CIAE

Accelerator mass spectrometry (AMS) is one of the most promising methods to detect minute amounts of 182Hf. However, the sensitivity of 5 × 10−11 for 182Hf/180 Hf obtained previously by the AMS method at China Institute of Atomic Energy (CIAE) cannot meet the requirement of some applications. We present some new improvements of measurement method for AMS measurement of 182Hf at the CIAE HI-13 tandem accelerator system. As a result, a sensitivity of 1.0 × 10−11 for 182Hf/180 Hf is achieved.

Determination of the number of atoms of the long-lived nuclide 126Sn by γ-ray spectrometry

By using HPGe γ-ray spectrometry, the activity of the long-lived fission product 126Sn in a SnOB2 sample was measured. The number of 126Sn atoms and the ratio of 126Sn to Sn were calculated based on the half-life value of 2.35×105a and the chemical stoichiometry. The result of the ratio of 126Sn to Sn, (1.033±0.037)×10−8, is consistent with the results measured by the accelerator mass spectrometry (AMS) within uncertainty limits, which confirms our procedures in the measurement of 126Sn by AMS and lays a foundation for the AMS measurement of 126Sn at much lower levels.

Application of41Ca Tracer and Its AMS Measurement in CIAE

The man-made calcium isotope 41Ca is an ideal tracer for the study of calcium metabolism. We represent the first application of accelerator mass spectrometry (AMS) measurement of 41Ca tracer in China. The technique is being applied to the research field of cell messenger at the China Institute of Atomic Energy (CIAE). The sample preparation methods and the AMS measurements are discussed and some interesting results are presented.

AMS Measurement of 36Cl with a Q3D Magnetic Spectrometer at CIAE

The ratio of 36Cl/Cl can determine the exposure age of surface rocks and monitor the secular equilibrium of 36Cl of sedimentary and igneous rock in groundwater. Due to the uncertainty effects of different chemical separation processes for removing 36S, there is a high degree of uncertainty in 36Cl accelerator mass spectrometry (AMS) measurements if the ratio of 36Cl/Cl is lower than 10−14. A 36Cl AMS higher sensitivity measurement has been set up by using a ΔE-Q3D method at the China Institute of Atomic Energy (CIAE). The performances of ΔE-Q3D method for 36Cl-AMS measurement had been systemically studied. The experimental results show that the ΔE-Q3D method has a higher isobar suppression factor. Taking advantage of direct removing 36S, the sample preparation can be simplified and the uncertainty effects of different chemical separation processes can be reduced in 36Cl AMS measurements.

Anomalously High Isotope Ratio 3He/4He and Tritium in Deuterium-Loaded Metal: Evidence for Nuclear Reaction in Metal Hydrides at Low Temperature

Anomalous 3He/4He ratios in deuterium-loaded titanium samples are observed to be about 1–4 × 10−1, much greater than the values (≤10−4) in natural objects. Control experiments with the deuterium-unloaded titanium sample and original industrial deuterium gas are also carried out, but no anomalous 3He/4He values are observed. In addition, anomalous tritium in deuterium-loaded titanium samples are also observed. To explain the excess 3He and tritium in the deuterium-loaded titanium samples, it is required that the deuteron-induced nuclear reaction occurs in the samples at low temperature.