The cause of the low detection efficiencies of Cherenkov radiation by the liquid scintillation counter was investigated. The detection limit of the liquid scintillation counter was assumed and the increase of counting rates for the increase of refractive index was calculated from Cherenkov photo yields and -distribution.
To understand the behaviour of Tl/II/ and the bridging group SO
in radiation induced electron exchange reactions we have investigated the rate constants and mechanisms of reaction of Tl/II/ with Tl/I/ and Tl/III/ in perchloric acid solutions. The results indicated that Tl/II/ is an intermediate in the -ray induced electron exchange process of T1/I/–T1/III/. Sulfate ions at [SO
]>-0.02M serve as bridging groups and play an important role in accelerating the T1/II/–T1/I/ reaction. A cooperative effect was found between hydrogen peroxide and sulfate ion at low sulfate ion concentration, [SO
]0.02M in perchloric acid solution.
The rate constants for thallium(I)-thallium(III) exchange with various alcohols in sulfuric acid solution were determined. In all cases involving alcohols, methanol, ethanol, 2-propanol, 2-methyl-2-propanol, the reaction rates were not accelerated. The larger the formation constants of solvato-complexes for 2-propanol and 2-methyl-2-propanol lead to lower reaction rates in the solution. The mechanism of the exchange reaction was also studied.
The counting efficiency of Cherenkov radiation by the liquid scintillation counter is studied in several solvents. The relation between the strength of the pulse height by the Cherenkov radiation and the maximum energy of -rays was fairly proportional. The colour quenching can be corrected by measuring the absorbance of solution.
The values of Sb(III), Tl(I), Te(IV), and biological substance, DNA determined by sub- and super-equivalence method of isotope dilution analysis (SSE-IDA) and substoichiometric isotope dilution analysis (Subst-IDA) under the same condition were compared. From the results, it was proved that SEE-IDA did not need the strict condition necessary for Subst-IDA and the determination by SEE-IDA was possible within the error of a few percent, and the range of determination was wider than that of Subst-IDA. The various variants of SSE-IDA reported so far were classified into SEE-Reverse-IDA and SEE-Direct-IDA. Finally, the characteristics of SEE-IDA allowing accurate determination were discussed and summarized.
The rate constant of radiation induced exchange reaction between thallium(I) and thallium(III) ions has been studied for elucidating the mechanisms which are responsible for (T1(II) intermediates or bridging groups (SO
) in sulfuric acid and perchloric acid solutions. It was found that the radiation induced exchange reaction is accelerated by the sulfate ion, and the rate of the thallium(II)-thallium(I) reaction is faster than that of the thallium(II)-thallium(III) process in perchloric acid solution.
A new sub-superequivalence method of radiometric analysis is proposed, which is derived by combining the sub-superequivalence method of isotope dilution analysis with substoichiometric radiometric analysis. This method using redox reaction is applied for the determination of trace amount of antimony and was proved to be an excellent technique. The fundamental problems of this method are discussed analytically.
Authors:K. Shinotsuka, H. Yoshioka, T. Omori, and K. Hasegawa
The reduction reaction mechanism of carrier-free125Sb in HCl solution was studied kinetically. Sb(III) and Sb(v) were separated by solvent extraction using n-benzoyl-n-phenylhydroxylamine(BPHA) in chloroform at different constant time in interval and the reaction rate was determined by measuring the radioactivities of125Sb in both organic and aqueous phases. Plot of log[125Sb(V)/ [125Sb(III)+125Sb(V)] against the elasped time do not give straight lines. The curves can be solved to be ABC type reactions by a non-linear squares. On the basis of dependence of the reactions, overall reactions can be expressed as follows;
Authors:K. Norisuye, K. Okamura, Y. Sohrin, H. Hasegawa, and T. Nakanishi
The present paper describes a new analytical method for determining the 240Pu/239Pu isotopic ratio and 238Pu/239+240Pu α -activity ratio in seawater, both of which are important parameters for determining Pu sources in the ocean. Plutonium
isotopes were preconcentrated from a large volume of seawater (4700-10800 liter) by solid phase extraction using MnO2-impregnated fibers and eluted into 3M HCl. After the elution, the Pu species of all oxidation states were converted to Pu(IV)
using NaNO2, purified by solvent extraction using thenoyltrifluoroacetone (TTA)-benzene, and concentrated in 5 ml of 0.2M HNO2. The 240Pu/239Pu and 238Pu/239+240Pu ratios in the 5-ml final solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and α-spectrometry,
respectively. A pg level of Pu, which was a sufficiently large amount for the determination, was obtained by the solid phase
extraction. Through the redox conversion and solvent extraction, the Pu species, such as Pu(III), Pu(IV) and Pu(VI), were
collected at a high recovery of 96±2% (n=3) despite the presence of large amounts of Mn, and interfering 238U (3.3 µg. l-1in seawater) was effectively removed with a decontamination factor of 1.7·107. The accuracy of the method for the 240Pu/239Pu ratio was verified using reference materials of seawater and a terrestrial soil sample. The present technique was applied
to the determination of the 240Pu/239Pu and 238Pu/239+240Pu ratios in coastal and oceanic water.
Authors:K. Masumoto, M. Hara, D. Hasegawa, E. Iino, and M. Yagi
The internal standard method coupled with the standard addition method has been applied to photon activation analysis and proton activation analysis of minor elements and trace impurities in various types of iron and steel samples issued by the Iron and Steel Institute of Japan (ISIJ). Samples and standard addition samples were once dissolved to mix homogeneously, an internal standard and elements to be determined and solidified as a silica-gel to make a similar matrix composition and geometry. Cerium and yttrium were used as an internal standard in photon and proton activation, respectively. In photon activation, 20 MeV electron beam was used for bremsstrahlung irradiation to reduce matrix activity and nuclear interference reactions, and the results were compared with those of 30 MeV irradiation. In proton activation, iron was removed by the MIBK extraction method after dissolving samples to reduce the radioactivity of56Co from iron via56Fe(p,n)56Co reaction. The results of proton and photon activation analysis were in good agreement with the standard values of ISIJ.