Np(V) / Complex formation / Humic acids / Polyacrylic acid / Solvent extraction / Metal concentration effectSummary. By using 239 Np and/or 237 Np, the complexation of Np(V) with Aldrich humic acid and polyacrylic acid has been studied at the concentration of Np(V) from ∼ 10 −13 to ∼ 10 −4 M by the solvent extraction method using TTA and 1,10-phenanthroline in isoamyl alcohol. By defining the apparent formation constant as βthe total concentration of proton exchanging sites and α is the degree of dissociation, [M] and [ML] respectively denote the concentrations of free and bound NpO 2 + , log β α have been obtained at pH 6-7 in 0.1 and 1.0 M NaClO 4 . For both humate and polyacrylate, log β α slightly increased with the degree of dissociation, and slightly decreased with ionic strength. While the variation of Np(V) concentration had no appreciable influence on the log β α of polyacrylate (ranging from 1.8 to 3.0 depending on pH and ionic strength), log β α of humate decreased from 4.7-5.3 (depending on pH and ionic strength) at [M] < 10 −9 M to 2.8-3.1 at [M] = 10 −5 M, indicating the coexistence of weak and strong binding sites in the humic acid.
We present a technique—based on the Lutz, Winston, and Maleki test used in stereotactic linear accelerator radiosurgery—for verifying whether proton beams are being delivered within the required spatial coincidence with the gantry mechanical isocenter. Our procedure uses a proton beam that is collimated by a circular aperture at its central axis and is then intercepted by a small steel sphere rigidly supported by the patient couch. A laser tracker measurement system and a correction algorithm for couch position assures precise positioning of the steel sphere at the mechanical isocenter of the gantry. A film‐based radiation dosimetry technique, chosen for the good spatial resolution it achieves, records the proton dose distribution for optical image analysis. The optical image obtained presents a circular high‐dose region surrounding a lower‐dose area corresponding to the proton beam absorption by the steel sphere, thereby providing a measure of the beam alignment with the mechanical isocenter. We found the self‐developing Gafchromic EBT film (International Specialty Products, Wayne, NJ) and commercial Epson 10000 XL flatbed scanner (Epson America, Long Beach, CA) to be accurate and efficient tools. The positions of the gantry mechanical and proton beam isocenters, as recorded on film, were clearly identifiable within the scanning resolution used for routine alignment testing (0.17 mm per pixel). The mean displacement of the collimated proton beam from the gantry mechanical isocenter was 0.22±0.1 mm for the gantry positions tested, which was well within the maximum deviation of 0.50 mm accepted at the Proton Therapy Center in Houston.PACS numbers: 87.53.Xd, 87.53.Oc, 87.56.‐v, 87.66.‐a, 87.56.Fc
Based on the conceptual model of cation-humic interactions considering the heterogeneous composition and polyelectrolyte nature of humic acids, the description of the interaction by the expression, logis the concentration of the cation bound to the humic acid, [M] is the concentration of the free cation with charge z, and [R] is the concentration of the free anionic sites of the humic acid, [R] = (C R − z[M · ·(zR)])α (C R is a total concentration of proton exchanging sites and α is a degree of dissociation). log K , m, a and b are the constant parameters depending on the cation and the humic acid. The expression is successfully applied to the experimental results on the complex formation (or protonation) of humate and polyacrylate (a homogeneous polymeric weak acid) with H + , NpO 2 + , Eu 3+ , Ca 2+ , Fe 2+ and Fe 3+ obtained under the condition where hydrolysis of cations and saturation of the reacting sites can be neglected.
Carborne surveyAir dose rate Fukushima Daiichi nuclear power plant a b s t r a c t A carborne survey system, named as KURAMA (Kyoto University RAdiation MApping system), was developed as a response to the nuclear accident at TEPCO Fukushima Daiichi Nuclear Power Plant in 2011. Now the system has evolved into KURAMA-II, characterized by its compactness, autonomous operation, and acquisition of pulse-height spectrum data. A two-year field test of radiation monitoring by KURAMA-II on local buses, performed by Kyoto University, has successfully proceeded to the phase of official operation by the Fukushima prefectural government, supported by Kyoto University and JAEA (Japan Atomic Energy Agency). An outline and the current status of KURAMA-II, including some results of the continuous monitoring by KURAMA-II on local buses in Fukushima, are introduced.
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