No abstract available

[en] After the Fukushima nuclear disaster, social concern about radiocesium (¹³⁷Cs and ¹³⁴Cs) contamination in food increased. However, highly efficient instruments that can measure low level radioactivity are quite expensive and heavy. A compact, lightweight, and reliable radiation detector that can inexpensively monitor low level radiocesium is highly desired. We developed a compact and highly efficient radiocesium detector to detect ∼32 keV X-rays from radiocesium instead of high energy gamma photons. A 1-mm thick GAGG scintillator was selected to effectively detect ∼32 keV X-rays from ¹³⁷Cs to reduce the influence of ambient radiation. Four sets of 25 mm×25 mm×1 mm GAGG plates, each of which was optically coupled to a triangular-shaped light guide, were optically coupled to a photomultiplier tube (PMT) to form a square-shaped well counter. Another GAGG plate was directly optically coupled to the PMT to form its bottom detector. The energy resolution of the GAGG well counter was 22.3% FWHM for 122 keV gamma rays and 32% FWHM for ∼32 keV X-rays. The counting efficiency for the X-rays from radiocesium (mixture of ¹³⁷Cs and ¹³⁴Cs) was 4.5%. In measurements of the low level radiocesium mixture, a photo-peak of ∼32 keV X-rays can clearly be distinguished from the background. The minimum detectable activity (MDA) was estimated to be ∼100 Bq/kg for 1000 s measurement. The results show that our developed GAGG well counter is promising for the detection of radiocesium in food

[en] The feasibility of the ScintiVial method to measure radioactivity was investigated. The counting efficiency for ³²P was 40-10% and that for ¹²⁵I was 8-4%. This method is quite simple, needs no scintillation cocktail, is less expensive, and do not produce any radioactive organic liquid waste. Furthermore, the sample can be reused. (author)

[en] A new in vivo thyroid ¹³¹I monitoring method was devised by using an imaging plate (IP). A thyroid image obtained with a realistic neck-thyroid phantom showed a unique shape characteristic of the thyroid gland. A ¹³¹I thyroid imaging allows visual confirmation of thyroid accumulation of ¹³¹I. The detection limit of the IP system of 290 Bq was about ((1)/(100)) of the screening level of 30 kBq in cases of public emergencies. The IP system is applicable for thyroid ¹³¹I monitoring

No abstract available

[en] The thermal neutron cross section of the ⁹⁹Tc(n,γ)¹⁰⁰Tc reaction has been measured by means of an activation method for the purpose to obtain fundamental data for the research of the transmutation of nuclear waste. Targets containing about 370 kBq of ⁹⁹Tc were irradiated for 2 m with reactor neutrons. Activation detectors of Co/Al and Au/Al alloy wires were irradiated to monitor the neutron flux and the Westcott's epithermal index r(T/To)^1/2. Spectra of γ-rays from the irradiated Tc samples were measured with a high purity Ge detector. Decay of the 540-keV and the 591-keV γ-rays were followed. A half-life of the decay of the γ-rays was 15.56 ± 0.30 s and in good agreement with the half-life of ¹⁰⁰Tc. The amount of the produced ¹⁰⁰Tc was obtained from the intensities of the 540-keV and the 591-keV γ-rays. The specific activity of ⁹⁹Tc in the targets were obtained by measuring the specific β-activity of sample solution by the liquid scintillation counting method. Then, the amount of ⁹⁹Tc in the targets were determined. A cross section of the ⁹⁹Tc(n,γ)¹⁰⁰Tc reaction was determined from the number of ⁹⁹Tc atoms of the target, the activity of the produced ¹⁰⁰Tc and the neutron flux data. The cross section obtained is 18 ± 2 b and is almost same as the value reported in references. The resonance integral was also measured by a Cd-ratio method. (author)

[en] The thermal neutron capture cross sections (σ₀) and resonance integrals (I₀) of ¹²⁹I were measured to obtain the fundamental data for the transmutation of ¹²⁹I (one of fission products), by the neutron capture. The amount of target nucleus was determined from the specific activity and the weight of the target. Gamma-rays from the produced nuclei, ¹³⁰I and ^130mI, were measured by a high purity Ge detector to deduce the amount of ¹³⁰I and ^130mI. Results obtained are as follows: For formation of ^130mI; σ₀²⁺ = 17.5 ± 0.8 (b), I₀²⁺ = 17.9 ± 0.9 (b), For formation of ¹³⁰I; σ₀⁵⁺ = 12.6 ± 0.5 (b), I₀⁵⁺ = 15.5 ± 0.9 (b). (author)

[en] This system was composed of a personal computer, a liquid scintillation counter and a well-type NaI(Tl) scintillation counter. The radioactivity of smear samples was automatically measured by these counters. The personal computer received raw signals from the counters through an interface of RS-232C. The software for the computer evaluated the surface concentration of each nuclide, and printed out that value along with other items as a report. The software was programmed in Pascal language. This system was successfully applied to routine survey for contamination in our facility. (author)

No abstract available

[en] Precise relative γ-ray intensities of ⁵⁶Mn and ⁷²Ga produced by neutron irradiation of natural Mn₃O₄ and enriched ⁷¹Ga₂O₃ (99.8%) were measured by an HPGe detector with highly-precisely calibrated detection efficiencies. As both nuclides exhibit no β branch to the ground state, the absolute emission probabilities of the 846.8 keV γ ray for ⁵⁶Mn and 834.0 keV γ ray for ⁷²Ga were determined to be 0.9888±0.0014 and 0.9553±0.0005, respectively