Takashi Natake

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.

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.

Elimination of chemiluminescence in liquid scintillation measurement

Abstract A new liquid scintillation technique which allows the interference of chemiluminescence to be analytically subtracted has been proposed. This technique makes it possible to find the precise activity and to estimate the contribution of chemiluminescence for prepared samples. All that is required in this technique is one set of quenched standard samples and a chemiluminescent sample. The technique has been applied to 3 H measurements and found to be practicable for routine radioassay.

Nuclide identification of β-emitter by a double ratio technique using a liquid scintillation counter

Abstract A liquid scintillation technique for nuclide identification of unknown β-activity samples has been developed by using a double ratio technique. Minimum requirements for this technique are a liquid scintillation counter and sets of quenched standard samples for the nuclides to be analyzed. The procedure outlined here is readily carried out without any modification of the liquid scintillation counter. When this technique is combined with a quenching correction method with the aid of a computer system, it is possible to identify the nuclide of the sample and to determine its activity automatically.

Double ratio technique for determining the type of quenching in liquid scintillation measurement

Abstract A new double ratio technique which enables the detection of whether prepared samples for liquid scintillation measurement are predominantly colour- or chemical-quenched has been proposed. This technique makes it possible to determine the quenching correction curve to be employed in finding the activities of samples, resulting in reduction in the error which may arise from the difference between colour and chemical quenchings. This technique has been applied to the cases of 3 H and 14 C radioassays, and found to be practicable.

USEFULNESS OF FLOATING RADIOLUMINOGRAPHY TO TRITIATED SAMPLES

Abstract A new technique of radioluminography for 3 H is shown, where by a spacer is inserted between the imaging plate and the radioactive sample in order to avoid radioactive contamination of the plate for repeated use. Also, elevation of the detection efficiency has been realized by improvement in the evacuation to minimize the absorption of 3 H β-rays. The technique has been studied systematically for space distance (1 spacer thickness) and for air pressure. By evacuation, the detection sensitivity can be elevated to more than 15 times. This technique is highly suitable for microplate and filter samples.

NUCLIDE IDENTIFICATION FOR PURE BETA-EMITTING RADIONUCLIDES WITH VERY SIMILAR BETA END-POINT ENERGIES USING A LIQUID SCINTILLATION SPECTROMETER

Abstract Pure-beta emitting radionuclides with very similar beta end-point energies can be identified by using a liquid scintillation pulse height analysis. Besides a liquid scintillation spectrometer, quenched sample sets for the nuclides to be analyzed are all that are required for this technique. It is important to determine the optimal channel settings in order to detect the slight difference in the scintillation pulse height distributions of the nuclides.In this study, the technique has been applied to the nuclide identification for 14 C and 35 S, and the lower detection limit with 95% confidence level was estimated to be 0.3 Bq/ml based on 5 ml activity sample and 60 min counting time.

Liquid scintillation radioassay for low-activity beta-emitter mixtures by the method of least squares

From the practicable viewpoint for environmental radioactivity measurement and monitoring, the liquid scintillation radioassay has been applied to low-level pure-beta and γ-emitter mixtures by using the most probable value theory. In low activity measurement, it is required to select a suitable emulsion scintillator and to deal with the calculated data statistically. Detection limit for a solution sample has been roughly estimated to be 10−2 Bq ml−1.

Nuclide identification of pure-beta emitter mixtures with liquid scintillation spectrometry

Abstract A useful nuclide identification technique for samples containing plural pure-beta emitting nuclides has been proposed by using the most probable value theory. The technique consists of two processes: (1) dpm calculation corresponding to registered nuclides by a liquid scintillation spectrometer; (2) nuclide identification by adopting two detection criteria to the calculated dpm. All that are required are to construct quenching correction curves for the registered nuclides in many more channel regions than the number of the nuclides. The technique has been applied to relatively lower level radionuclide mixtures, and found to be practicable with the aid of computerized data processing.