Haruo Fujii

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.

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.

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.

Liquid scintillation radioassay for multiple radionuclide mixtures by the most probable value theory

Multiple radionuclide mixtures which have similar scintillation pulse height distributions can be accurately radioassayed by the most probable value theory. This liquid scintillation technique is based on the construction of more observation equations than the number of nuclides to be analyzed. The technique has been applied to3H−14C−125I and3H−14C−51Cr mixture samples, and found to be very practicable with the aid of computerized data processing for mixture samples having a wide range (ca. 10 times) of activity ratios.

PPO-ethanol system as wavelength shifter for the Cherenkov counting technique using a liquid scintillation counter

Abstract 2, 5-diphenyloxazole (PPO) has been proposed as a wavelength shifter for Cherenkov counting. Since PPO is not incorporated with water, we have introduced the fluor into water in the form of micelle using a PPO-ethanol system. This technique makes it possible to obtain a high Cherenkov counting efficiency under stable sample conditions, attributed to the proper spectrometric features of the PPO. The 32 P Cherenkov counting efficiency (68.4%) obtained from this technique is large as that measured with a conventional Cherenkov technique.

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.

Radioassay of alpha- and beta-emitters by sequential Cherenkov and liquid scintillation countings

Abstract Alpha- and beta-activities in a sample can be determined by using Cherenkov counting and liquid scintillation efficiency tracing technique. This method does not require any modification of a conventional liquid scintillation counter, and analytical procedure is very simple. All that is required is one set of Cherenkov color quenched standard samples and a liquid scintillation reference sample. This technique has been applied to a 32 P- 241 Am pair, and found to be practicable for routine radioassay with the aid of computerized data processing.

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.