Development of alanine dose-reader is crucial for wide application of alanine/ESR dosimetry to routine dosimetry in radiation processing (1-100 kGy.) An alanine dose-reader was developed as an easy-handling and single purpose dose-reading system, which is composed by ESR spectrometer part, data processing auxiliary (interfaces), and a personal computer. ESR measurement parameters were optimized on the basis of data obtained by manual operation of the ESR spectrometer part. Computer programs of ESR measurement and data processing procedure were also designed for synchronizing the functions of the above three parts. The automated reader permits us to estimate doses in radiation processing level (1-100 kGy) with precision of ±2% (at 95% confidence level) and to readout one dosimeter within one minute.
A calibration method for radioactive gas monitoring instruments was studied. In the method, gaseous radioactivity standards were provided on the basis of the direct radioactivity measurement by the diffusion-in long proportional counter method (DLPC method) . The radioactivity concentration of the gas mixture through a monitoring instrument was determined by sampling the known volume of the gas mixture into the proportional counter used for the DLPC method. Since oxygen in the gas mixture decreased the counting efficiency in a proportional counter, the influence on calibration was experimentally estimated. It was not serious and able to be easily corrected. By the present method, the relation between radioactivity concentration and ionization current was determined for a gas-flow ionization chamber with 1.5l effective volume. It showed good agreement with the results in other works.
Lung disease risk from inhalation of radon can be enhanced by the presence of particulate pollutants in indoor air. The indoor concentration of radon and particulates were measured in homes, a department store, and offices in a high building in Tokyo metropolis, as well as in homes in both northern and western Japan. Passive radon monitors were located in living rooms and offices for more than three months at 99 sites during the winter of 1988 and 1989. Indoor radon concentration ranged from 11.1 Bq/m3to 148Bq/m3 (n=99) and averaged value S.D. was 36.5±14.2 Bq/m3.However, the average concentration in air conditional buildings was 21.8±9.51 Bq/m3 (n=17) . Simultaneously at 65 of the radon sites, indoor particulates were collected using personal dust samplers by impaction methods. Deposited particulate concentrations on the sampler were measured and calculated in a unit of μm/m3.Concentrations were determined for particle sizes above and below 2.5 μm, for both smoking or non smoking sites. Consequently, concentration of particle size below 2.5 μm was high in smoking rooms. Finally, it was considered that smoking was a complex indoor pollutant as adherence of radon daughter to aerosols.
An automatic sample changing system with a small robot has been developed and constructed for instrumental neutron activation analysis (INAA) . The developed system composed of a model A151 small robot (CRS Plus Inc., Canada), a NEC PC-9801m2 personal computer having two of 1 Mbyte floppy-disk drivers, a NAIG NLAB-MCA multichannel analyzer (Toshiba), Ge detector settled in a low background shield and a tray stored 20 dishes containing a sample. The robot has a five-axis articulated arm (reach: 560 mm, payload: 2 kg, speed : 17m/s, repeatability: 0.13 mm, weight: 17 kg) . The robot and the MCA are controlled by the personal computer via RS-232C or GP IB interface.
Experiments were made to determine the effect of sample grain size on theCO33-signal intensity and the effect of sample orientation in dental ESR dosimetry. Tooth enamel was separated from other parts of teeth, and irradiated with60Cogamma-rays up to about 1290×10-4C/kg (500 R) . The irradiated tooth enamel fragments were crushed, sifted and classified in 9 grain size groups. Three samples of each group were subjected to ESR measurements. For a grain size above 1400μm, directional dependence appeared remarkably. On the other hand, samples of grain size under 300μm showed distorted ESR spectra and gave smaller signal intensity. It is concluded that the sample sizes ranging 500-1400μm are most suitable for dental ESR dosimetry.