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Abstract  

The half life of57Ni has been measured by Ge/Li/ -ray spectroscopy. The57Ni radionuclide was created by bremsstrahlung impinging a sample of elemental Ni. Time change of the activity of the 1377.6-keV -ray following decay of57Ni was analyzed to obtain a half life of 35.54±0.05 h for57Ni.

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Abstract  

The half life of128I in I2, KI, KIO3 and KIO4 was measured. Contrary to recent claims no variation of half life with the chemical environment could be detected within the limits of experimental error.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: R. Van Schandevijl, R. Van Grieken, and J. Hoste

Abstract  

The half-life of28Al was redetermined on aluminium samples of different origin. Three different counting techniques were applied. The availability of highly purified samples (up to 99.9999%), the use of very fast electronic counting equipment and a complete automatisation allowed a good precision to be obtained in the final result of 2.2405 min.

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Abstract  

In the course of making high-accuracy measurements of arsenic, we found that the most recently published and compiled half-life of 76As did not agree with our data as well as the earlier accepted value. To redetermine this parameter, 76As sources were measured on four Ge gamma detector systems, and an exponential function was fitted to the decay data by two different nonlinear least-squares methods. We obtained T 1/2 = 1.09379 days with a standard uncertainty of 0.00045 days. This result is 1.5% higher than the most recent value, but is in agreement with the older, less precise, consensus value.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Huang Donghui, Wang Pingsheng, Chen Xilin, Tian Weizhi, Ni Bangfa, Zhang Lanzhi, Zhang Guiying, Liu Cunxiong, and Liu Likun

Summary  

The half-life of 97Zr, used for the calculation of thermal/epithermal neutron flux ratio in k 0-NAA, is re-determined using three measurement systems with different pulse processing principles. The result of 16.755±0.013 hours clarifies the discrepancy between two widely used literature values, 16.744±0.011 and 16.90±0.05 hours. Different dead-time correction methods used on various measurement systems are evaluated. Factors influencing precise measurement of relative peak counting rates are discussed in time-series measurements over a dynamic range of 1000-fold radioactive intensities (10 half-lives).

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Abstract  

The half-life of134Cs obtained by gamma spectrometry from the change of the134Cs to137Cs activity ratio is 2.04±0.03 years.

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Abstract  

Half-life of241Pu is of great importance in nuclear technology. In view of large variation in the values (13–15 y) reported till 1974 in literature, efforts have been made in different laboratories to determine this half-life with high precision and accuracy. In our laboratory, it has been determined by different methods which may be classified in two categories, viz. (1) parent decay method, and (2) daughter growth method. In the parent decay method, change in isotope ratios241Pu/239Pu,241Pu/240Pu and241Pu/242Pu was studied periodically by a thermal ionization mass spectrometer. Single as well as double ratio method was used to calculate the half-life. In the daughter growth method, the half-life was obtained in four independent ways. These were (1) alpha spectrometry taking239Pu and242Pu separately as reference isotopes and studying periodically the increase in alpha activity ratio, (2) alpha proportional counting for observing periodically the change in total alpha activity, (3) isotope dilution alpha spectrometry using243Am as a spike, (4) isotope dilution mass spectrometry using243Am as a spike. In all these methods, synthetic mixtures were prepared for achieving high precision and accuracy in different measurements. Based on the results obtained in this laboratory and the values reported by other laboratories, a half-life value of 14.4±0.1 y is recommended. The paper reviews the past history, puts forth the present status, highlights the current trends for studying the effect of chemical composition of plutonium on the half-life of241Pu and presents the future requirements for achieving higher accuracy in the half-life of241Pu.

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Abstract  

The half-life of38Cl obtained by thermal neutron capture was measured to be 37.236±0.009 min. Values of the energy levels of38Ar from decay of38Cl were determined with a better precision than those available in the literature.

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Summary  

An approach for half-life determination using the reference source method associated with gamma-spectrometry with a Ge detector is presented. The method reduces the contribution of the type B component of the total uncertainty. The independence of the method regarding the instrumental interferences or radiochemical impurities was evidenced. However, there are some limitations when the method is applied for a genetically-related impurity with the same or very similar energy to that of the radionuclide to be measured, e.g., if 99Mo in a 99mTc sample is present. The measured half-life values are in good agreement with those of the literature and the associated uncertainties are lower than 0.1%.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Judah Friese, Rosara Payne, Larry Greenwood, Chuck Soderquist, and Stephanie Garofoli

Abstract  

The measurement of the decay of 153Sm was observed by gamma spectrometry, liquid scintillation counting and gas proportional counting in an attempt to confirm the half life and gamma abundance ratios for this isotope. Recent changes in the published nuclear decay data indicate that historical literature values may be biased. The 153Sm was made by the neutron activation of ultra-pure isotopically enriched 152Sm to create 153Sm. The decay measurements were made over a three week period and no other isotopes were detected during this time. The gamma abundance ratio for the 103 keV gamma was measured to be (27.9%) which is 4% lower than the published data. In addition, the half life was 1.9308 days, which is 0.34% lower than the published data.

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