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- Author or Editor: A. Chin x
- Chemistry and Chemical Engineering x
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Abstract
High energy medical linear accelerators (>10 MV) are increasingly used in radiotherapy. At such high photon energies neutron production via photonuclear reactions in the heavy elements which compose the linac head is inevitable. Neutrons from linacs can contribute to an additional dose to staff, patients and the general public. Our intention is two-fold; to provide shielding against the neutron contamination and to establish the depthdose curve of thermal neutrons within human tissue, with an aim to utilise linacs in boron neuron capture therapy (BNCT). In our studies neutron measurements were undertaken, with a Varian Clinac 2100C/D linear accelerator operating at 15 MV nominal energy, by irradiating 18 cm thick 30×30 cm2 block of tissue equivalent material. Measurements were taken using indium and aluminum activation foil at the centre of the block. Our results show that by leaving the linac jaws open neutron production is increased compared to the case when these are shut, for one minute exposure at 400MU. In this work we present a comparison between our results and existing literature and attempt to explore some sharp contrasts.
Abstract
A laser-induced optical fiber fluorimetry has been reported for the analysis of ultralow level of uranium. The fluorescence spectrometer includes five major components: a pulsed nitrogen laser, optical fibers, an optrode, a detector, and a boxcar. The fluorescence intensity of uranyl ions is linear with respect to the concentration of uranium. The detection limit of uranium in 1M phosphoric acid is 24 ppb. This technique can be used for the remote, on-line measurement of low level uranium.
Abstract
Laser-induced optical fiber fluorimetry has been first used to analyze uranium(VI) concentration in the kinetic studies on the extraction of uranium(VI) between 0.5 mol/l H3PO4 solution and HDEHP-cyclohexane system with a Lewis cell. The effects of stirring speed, temperature and concentrations of uranium(VI) and HDEHP on the rate of extraction were examined. These data show that the extraction rate of uranium(VI) in this system is controlled by the chemical reaction at the interface. The rate equations and the rate constants of forward and reverse extraction are obtained. The mechanism of the extraction is discussed.
