Aluminophosphate glass with a batch composition of 30 CaO⋅15 A12O3⋅5 Fe2O3⋅25 PbO⋅25 P2O5was prepared as a potential host for the high-level nuclear wastes. This“base glass”consists of highly heat-resistant 60CaO⋅ (40-x) A12O3⋅xFe2O3glass and water-resistant lead metaphosphate glass, Pb (PO3) 2, which is known to have -103 times higher water-resistivity than conventional borosilicate glass. Two crystallization temperatures (Tc) of 650-671 and 668-693°C were determined from the differential thermal analysis (DTA) of the“base glass”. Large activation energies of 4.2 and 4.9 eV were obtained from a Kissinger plot of the Tc values. Nuclear waste“model glass” containing 10 stable isotopes with the mass numbers of 90-100 (Sr, Y, Zr, Nb, Mo) and 135-145 (Ba, La, Ce, Pr, Nd) also shows high heat-resistivity.57Fe Mössbauer spectrum indicates that Fe (III) and Fe (II) are ionically bonded to distorted PO4tetrahedra at the sites of network modifier.
We want to establish a system of volume reduction by the incineration of the combustible radioactive solid wastes from radioisotope usage at the utilization facility. We have been performing experiments using an experimental incineration system to examine the distribution of radionuclides during incineration and to collect basic data. To reproduce the realistic conditions of incineration of low-level radioactive wastes in an experimental system, we adopted new incineration methods in this study. Low level radioactive samples (LLRS) were set up in a mesh container of stainless steel and incinerated at high temperature (over 800°C) generated by two sets of high calorie gas burners. Low energy β-emitters35S, 45Ca, 33P, and a high energy β-emitter32P were used for the experiment. Their translocation percentages in exhaust air and dust were estimated using the Imaging Plate. Distribution of radionuclides during the incineration was similar to that estimated by conventional methods by our study or to that reported in incineration of liquid scintillation cocktail waste. We concluded that the use of the Imaging Plates is a simple and reliable method for estimation of the distribution of low energy β-emitters in incineration gas and ash.
The method of calibrating a portable surveymeter for air absorbed dose rates of natural environmental gamma-rays and cosmic-rays is described. The records taken for a week for seven people leading their respective normal lives are discussed. Examples of measurements taken during domestic journeys and overseas trips are presented. It is emphasized that these kinds of data are important for (1) re-evaluation of the population doses, (2) discovery of anomalous man-made radioactivity in the living environment, such as from building materials containing contaminated recycled steels, and (3) educating the public about radiation.
In order to estimate the effective dose (E) of a person who may come into close contact to the99mTc-GSA patients. Radiation dose rates around 21 adult patients (male: 14, female: 7) were measured with three ionization surveymeters (Aloka, ICS-301) at distances of 0.05, 0.5, 1.0 and 1.5 m from the patients. Measurements were carried out at 0.75, 3.0, 6.0 and 24.0h after the administrations of99mTc-GSA.Surveymeters were set up to the first cervical vertebrae (Level I), xiphoid process (Level II) and anterior superior iliac spine (Level III) of the patients with their standing erect, The maximum dose equivalent (Hlcm) rate of 64.98μSvh-1per 185 MBq was recorded in the LevelII. Effective half life of99mTc-GSA was 5.8h. Total E around the patients were calculated by the initial Hlcmrates and the effective half life. Total E were 285, 62, 23 and 13μSv per 185 MBq at distances of 0.05, 0.5, 1.0 and 1.5m, respectively. E for the first 24h was corresponding to 94.3% of the total E.