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  • Author or Editor: Y. Murakami x
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Abstract  

A new counting method was developed to determine226Ra in environmental samples by separating the equilibrated222Rn into a liquid scintillator. The integral counting method, which was originally developed for isolated individual radionuclides, was extended to the mixture of222Rn and its daughters in equilibrium. The optimum measurement conditions were established by examining the energy spectrum, counting time and quenching effect. An absolute counting was practiced by extrapolating the integral counting rate-bias voltage curve with the highest gain to zero bias. The detection limit thus obtained was 3 to 4·10−13 Ci.

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Abstract  

77As(III) and77As(V) were separated from neutron-irradiated GeO2 by a thin-layer chromatographic method, in which silica gel was used as adsorbent and a 2∶1 mixture of methanol and 5N HCl as developer. The Rf values of these nuclides were as follows: 0.00 for77Ge, 0.50 for77As(III) and 0.94 for77As(V). The influence of As(III) carrier added before the separation was investigated on the oxidation state of77As recoiled from the parent nuclide. The radiochemical purity of77As thus separated was more than 99.9% and the activity due to77As could easily be eluted with water from the adsorbent, with 93% recovery.

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Abstract  

The separation of daughter nuclides in the carrier-free state from90Sr−90Y and140Ba−140La aqueous solution systems was performed by thin-layer chromatographic methods. (1) When a silica gel adsorbent and a developer of 1N NaCl, KCl, NH4Cl, CaCl2, SrCl2 or BaCl2 solutions was employed,90Y and140La were retained at the origin, while90Sr and140Ba advanced with the developer front. Addition of gypsum as binder to the silica gel prevented the separation of the140Ba−140La system, retaining both components at the origin. (2) When the140Ba−140La system was developed with water on a silica gel adsorbent containing 5% of gypsum, which was treated with various concentrations of nitric acid, the Rf value of140La increased with the concentration of nitric acid used, reaching a maximum of 0.98 at 0.1 N. The Rf value then decreased on the further increase of the concentration of nitric acid. When the same process was applied to the90Sr−90Y system, there was no separation. The radiochemical purities of90Y and140La obtained in the above two ways were more than 99%.

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Abstract  

A new method is described for the determination of Rn in soil gas. Open vials containing a liquid scintillator solution, suspended in a hole of the ground surface, absorb a fixed proportion of Rn present in soil gas. This allows the total Rn concentration to be determined. The method described is rapid, simple and reproducible. It should have many kinds of field application.

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Abstract  

A new determination method for222Rn and220Rn in water sample was developed by extracting radon with toluene and applying the integral counting method with a liquid scintillation counter. The essential characteristics of the methods are, (1) extraction of radon with toluene from water, (2) finding absolute counts and making corrections for the quenching effect by the adoption of the integral counting method, (3) the determination of222Rn and220Rn was performed by counting the activity of220Rn with its descendants and of ThB (212Pb) with its descendants in a radioactive equilibrium, respectively, (4) realizing high sensitivity by simultaneous counting of α, β particles emitted from the decay products formed in toluene. The lowest detection limit obtained by the present method was 5.0·10−13 Ci/l for222Rn and 6.8·10−8 Ci/l for220Rn in water.

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Abstract  

Environmental effects on plants caused by geothermal resource development were studied. Neutron activation method was found most suitable for this kind of multi-element analysis, and 24 elements could be identified and determined without any chemical separation. When the amounts of chemical elements detected in plants were plotted against the distance from the source well, clear correlations sould be observed for Na, Cl, Rb, Cs, As and Sb. Those turned out to be the elements especially concentrated in the geothermal hot water. From the present studies it was concluded that plants growing within the radius of 300 to 400 meters from the source well were affected by chemical pollutants carried over by mist particles.

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Abstract  

Environmental effects of geothermal waste water discharged into the neighbouring streams were investigated by ordinary chemical analyses and by the neutron activation method. Results show that serious effects of a large amount of discharge in the past are still retained in the sediments of the near-by water system. It was also found that As and Cs are the best chemical species for tracing the long-standing effects of past discharge.

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Abstract  

Neutron activation analyses were performed for the newly issued reference rocks, GSJ JA-1 and JB-2, and also for the widely distributed GSJ JG-1 and JB-1. The contents of fourteen elements could be newly determined for the former two rocks and those of eleven elements were re-determined for the latter rocks.

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Abstract  

An attempt was made to see if there is any correlation between the trace element concentrations in the human blood serum and some specific disease. The serum samples of the patients suffering from cancer, Down syndrome, and Banti syndrome were analyzed by the neutron activation method and compared with the trace element concentrations observed among the clinically healthy men. The cancer patients gave below normal concentrations in Rb, Mn, Fe, Co, Cu, Zn, Al and Se. The Down syndrome patients were found to have similar deficiencies in Cr, Mn, Fe, Co, Zn, Cu and Sb.

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Abstract  

The improvement obtained by epithermal neutron activation analysis was studied in terms of the detection sensitivity and precision in the γ-ray spectrometry for geological and biological reference samples. For geological samples, small improvement was observed only for the elements As, Ba, Sb, Se and U. For biological samples, however, large improvement was observed for As, Br, Sb and U. The ratio of the resonance integral to the effective thermal-neutron capture cross section was observed for 19 nuclides. The effect of the (n, p) reaction to the determination of Al and Mg by the ordinary reaktor-neutron activation analysis was estimated.

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