Tsuguo Genka

Determination of gamma-ray emission probabilities for 75Se, 166mHo and 192Ir by a self-consistent method

Abstract The gamma-ray emission probabilities for 75 Se, 166m Ho and 192 Ir have been measured precisely using a 4πβ(ppc)-γ(HPGe) coincidence system. When determining the gamma-ray detection efficiency function, these nuclides were used as secondary standards in conjunction with a few primary standard sources. This method is considered to give self-consistent results and to be effective when there are insufficient suitable standards.

GAMMA-RAY EMISSION PROBABILITIES OF 182TA

Abstract 182 Ta sources were produced, and the disintegration rate and γ -ray emission probabilities were measured as an aid in using this radionuclide as a calibrant for HPGe detectors. Metal powders proved to be the most appropriate sources, and the disintegration rate was determined with an uncertainty of less than 0.4%. Improved data with reduced uncertainties were also obtained for the γ -ray emission probabilities.

Radioactivity standards for 192Ir brachytherapy sources

Abstract Absolute radioactivities of brachytherapy 192 Ir metallic sources of single pin and hairpin types are nondestructively determined with a microcalorimeter. In order to convert the complete decay energy evolved from the sources into thermal energy, a radiation absorber made of tungsten is used. Overall uncertainties of the activity determinations are estimated to be ±3.1% for the single pin source and ±4% for the hairpin source at the level of 3σ.

Radioactivity measurements of 192Ir wire sources with a microcalorimeter

Abstract Radioactivities of metallic 192 Ir sources are measured with a microcalorimeter nondestructively. In order to convert the complete decay energy evolved from the source into thermal energy, a tungsten block is used as radiation absorber. The sample sources measured are four thin wires of Ir/Pt alloy with dimensions of 0.1 mm o × 10 mm 1 , each coated by 0.1 mm thick platinum, giving the final diameter of 0.3 mm o . Overall uncertainty of the measurement for some 60 MBq activity is ±3.2%. Measurements of the wire sources with an ionisation chamber give smaller activities which are smaller by 10% than those from microcalorimetry mainly because of the autoattenuation effect.

Analytical calculations on radioactivity measurements of 192Ir metallic sources with a calibrated ionization chamber

Abstract The self-attenuation of photons was analytically calculated for an 192 Ir metallic wire source and an aqueous standard source. The influence of the self-attenuation on the current of the calibrated ionization chamber was also evaluated. The self-attenuation did considerably affect the ionization current. It was concluded that the apparent radioactivity must be multiplied by a correction factor larger than unity (1.09±0.01 in the present case) to get the true radioactivity when the radioactivity of the 192 Ir metallic wire source was measured with the ionization chamber calibrated with the aqueous standard source of 192 Ir.

Radioactivity measurements of 153Gd pellet sources by calorimetric methods

Abstract The thermal power generation per 37 MBq (1 mCi) of 153 Gd is 0.839 μW. The activity of a sealed 153 Gd source can be determined by absorbing all radiations within a calorimeter to be converted into the thermal power. Sources are sintered pellets (3 mm diameter, 2 mm thickness) of Gd 2 O 3 ·Al 2 O 3 which are encapsulated in titanium capsules of 7 mm diameter and 10 mm length. A cylindrical radiation absorber made of solid copper having a space in the center for the 153 Gd source is used and the temperature rise of the absorber is measured. Uncertainties are added up to ±2.9% for a 3σ confidence interval in the final result for the measurement of the activity of an approximately 1.5 GBq (40 mCi) pellet source of 153 Gd in a fully nondestructive way.

Combination source for gamma-ray spectrometry

Abstract An acrylic-resin-made one-eight-sector source in which radioactive material was mounted at the angular position was constructed. The sources of this type may be used in various combinations of up to eight sources of the same or different kinds of nuclides, performing nearly point source configuration. Characterization and performance as well as applications of the combination source were discussed.