In order to estimate the internal exposure dose at the time of breaking the seal of the vial containing3H-and14C-labeled compound, the radioactivity in the air spaces of the vials was measured using our revised experimental apparatus and the radiochemical purity was measured using high performance liquid chromatography. 14C-Labeled compounds were decomposed slower than3H-labeled compounds. However, the radioactivity in the air spaces of14C-labeled compound vials was higher than that of3H-labeled compound vials, the estimated internal exposure dose of14C-labeled compounds was higher than that of3H-labeled compounds.
Technetium-99 has a long half-life (2.1×105y) and relatively high fission yield. For these reasons, the element is one of the most important radionuclides released from nuclear facilities, such as reprocessing plants and waste disposal facilities. When99Tc in environmental samples is analyzed, 95mTc or99mTc is added to them to obtain chemical recovery of99Tc. However, it is not clearly known whether these tracers have an aging effect, that is, whether they show the same behavior as that of99Tc. An incineration procedure to pre-treat sample for99Tc analysis is usually carried out to decompose organic matter. In the present study, the aging effect of Tc in soil was investigated by following this procedure at 450°C. Samples were soils contaminated with95mTc for 6 months and those freshly contaminated respectively; losses of the nuclide were determined. Although, no loss of95mTc from the aged soil was observed during an 8 h incineration, loss of the isotope due to volatilization from the freshly contaminated soil was constant after more than 4 h incineration. The loss ratio was about 10% of the initial activity in the soil.
The characteristics, spectroscopic energy resolution as well as intrinsic detection efficiency, of radiation detectors using a Photodiode, Hamamatsu Photonics PIN S 1723-06, are experimentally examined for X- or gamma-ray measurements. The two versions of CsI-PD and PD detector are examined, in which the Photodiode attached with and without a 10 mmφ×10 mmt CsI scintillator, respectively. Both a reference gamma-ray source set, Amersham X. 245 type QCR 1, and a 50 kV X-ray tube and exchangeable radiator assembly for producing K X-rays from the radiators are employed to prepare incident photons of wide energy range. The CsI-PD detector has the energy resolution (FWHM) of 7.9% for 662 keV137Cs gamma-rays and the PD detector has that of 7.1% for 59.5 keV241Am gamma-rays. The photons of 150-700 keV and 15-50 keV are detectable by the CsI-PD and the PD detectors, respectively, with the efficiency higher than 1%.
We are using a medical compact cyclotron for PET (positron emission tomography) and PIXE (particle induced X-ray emission) analysis in Nishina Memorial Cyclotron Center. The cyclotron vault is covered by concrete wall of 1.5 m thickness. However, a big penetrating window of 1.8 m square was needed at the concrete wall between the cyclotron vault and the PIXE room for beam transport equipment. This window was closed by packing materials of iron shots, small grained polyethylenes mixed with boron and lead grains for shielding of neutrons and γ-rays. Several measurement data have showed that this method is useful for shielding of radiations from the compact cyclotron.