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|Type:||Artigo de periódico|
|Title:||Measurement Of The Spontaneous-fission Disintegration Constant Of 238u|
|Abstract:||Large-area muscovite mica foils, previously treated thermally, prepared and chemically pre-etched in HF, were exposed in juxtaposition to uranium cylinders (U3O8 density 7.16 g cm-3; 3.3 cm in diameter and 4.0 cm in height), for 0.525 yr. In this period the mica foils registered tracks from the spontaneous fission of 238U nuclei contained in the cylinders as well as a small contribution of induced-fission tracks in uranium. We show that the latter group of fission tracks-induced mainly by cosmic-ray neutrons and by fast neutrons from the spontaneous fissions that take place in the cylinder during the exposure-give rise to an increase of less than 2% in the total number of fission tracks detected by the mica foils. Afterwards the mica foils were properly etched in HF and analysed microscopically. Then, sandwiches of uranium-loaded nuclear emulsion, mica foils and uranium targets were irradiated with slow neutrons. In this irradiation, the nuclear emulsions were used as calibrators of the absolute neutron flux. The mica foils were etched in HF, the emulsions were developed, and both fission-track detectors were observed under a microscope. The uranium-loaded nuclear emulsions were made from gel KO from Ilford Ltd. We measured the uranium-loading by gravimetry and by observing, under a microscope, the uranium alpha-activity. We obtained the following result: λf = (8.6±0.4) × 10-17 yr-1. © 1981.|
|Citation:||Nuclear Tracks. , v. 5, n. 1-2, p. 45 - 52, 1981.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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