Makoto Takiue

Radioassay by an efficiency tracing technique using a liquid scintillation counter

Abstract The various nuclides other than 3H are radioaasayed with an efficiency tracing technique. It has been clarified in this study that the liquid scintillation efficiency tracing technique possesses the following advantages; (1) sample preparation is of simplicity (2) even a nuclide different from a nuclide to be measured can be used as a reference sample, and (3) many kinds of pure β- and β-γ-emitters can be effectively radioassayed with a small error. Moreover, this technique has been systematized and successfully computerized to be applicable for a routine radioassay.

Thermal neutron reaction cross section measurements for fourteen nuclides with a liquid scintillation spectrometer

Abstract The thermal (n, γ) reaction cross sections for fourteen nuclides have been determined by an activation method. Radioactivities of neutron-induced nuclides were accurately measured with a liquid scintillation counter. This technique has the advantage of measuring the radioactivities without any absorption loss and scattering of radiations under a 4π geometry, so that it is possible to find highly accurate values for the reaction cross sections. Most of results obtained have fairly small errors in comparison with values hitherto published. In this study, 59Co was used as a thermal neutron flux monitor.

A new approach to analytical radioassay of multiple beta-labeled samples using a liquid scintillation spectrometer

Abstract A new technique which allows the activities of multiple β-labeled samples to be analytically radioassayed has been proposed by using the most-probable-value theory. The requirements for this technique are a liquid scintillation counter equipped with a multichannel pulse height analyzer, and quenched standard sample sets to be analyzed. This technique has been applied to mixture samples of 3 H 14 C 45 Ca 32 P, and found to be practicable for routine radioassay with the help of computerized data processing.

Accuracy of Cerenkov measurements using a liquid scintillation spectrometer

Abstract Cerenkov counting efficiency varies with colour quenching and sample turbidity. The activity in a plastic vial can be determined accurately with a colour quenching correction technique, regardless of the presence or absence of turbidity in a sample. On the other hand, the error of the measured activity in a glass vial becomes large with increasing sample turbidity due to the dissimilarity of the quench correction curves for non-turbid and turbid samples.

α-ray measurement due to air luminescence employing a liquid scintillation spectrometer

Abstract A new α-ray counting method due to air luminescence has been proposed. The luminescence, caused by the excitation of nitrogen contained in air, is effectively measured with a liquid scintillation spectrometer. High counting efficiency can be obtained even without a wavelength shifter which is essential to an α-ray measurement with noble gases. This technique is conveniently applicable to routine analysis of α-ray emitting nuclides, since atmospheric air itself containing 78% nitrogen can serve as an α-ray detector.

Radioassay of dual-labeled samples by sequential Cherenkov counting and liquid scintillation efficiency tracing technique

Abstract A convenient technique, which allows the activities of dual-labeled samples to be simultaneously radioassayed, has been proposed by sequential Cherenkov counting and liquid scintillation efficiency tracing technique. The minimum requirements of this method are one set of Cherenkov color quenched standard samples and a liquid scintillation reference sample. In this case, as the reference sample, a radionuclide different from the nuclides to be measured can be used. This means that the present technique can be applied to various kinds of dual-labeled samples.

Reliability of the activity determined by the quenching correction method for two groups of emulsion scintillators

Abstract The reliability of the activity, determined using conventional quenching correction methods, has been studied for two groups of emulsion scintillators: (1) scintillators with three distinct water dilution criteria; and (2) scintillators forming a miscible solution with up to 50% water content. Whilst for the first group of scintillators the error of the activity measured very often becomes larger with increased water content, the measurements with the second group of scintillators fit the quenching correction curve.

Effect of air luminescence counts on determination of 222Rn by liquid scintillation counting

Abstract The pulse-height distributions from known amounts of 222 Rn and its daughters were measured as a function of the volume of the scintillator solution and compared with the air luminescence spectrum from α-particles in air. The results indicate that 222 Rn and its daughters in the gaseous space above the liquid scintillator produce the air luminescence counts which lead to errors in quantitative determination of 222 Rn by liquid scintillation counting unless necessary corrections for the counts are made. The error inherent in the conventional determination of 222 Rn by liquid scintillation counting is evaluated. Methods for correcting the air luminescence counts are discussed.

New emulsive scintillator for liquid scintillation measurements

Abstract A new emulsive scintillator for liquid scintillation measurements has been proposed, which removes the inherent disadvantages of conventional emulsive scintillators. The new scintillator never forms gels and two phases, both of which are very inconvenient for user, and maintains a state of soft sol within a water content from 0 to 50%. It also possesses excellent properties with respect to stability, solubility and chemiluminescence as compared with conventional scintillators.

Analytical measurements of multiple beta-emitter mixtures with a liquid scintillation spectrometer

The most probable value theory has been applied to analytical radioassay for mixture samples of six pure-beta emitters by using a liquid scintillation spectrometer. Activities of each nuclide in the mixture sample can be determined by solving normal equations which are derived from twelve observation equations, the number of which is twice that of nuclides to be radioassayed. Requirement for the technique is to construct quenching correction curves of the respective nuclides. This technique has been tested to3H−63Ni−14C−45Ca−36Cl−32P mixture samples, and found to be very useful with the aid of computerized data processing.