Digital kVp meter, ion chamber, and x-ray films were used to study the tube voltage, beam output, and dose distribution for 29 x-ray units. Of which 14 units are equipped with single phase power supply and 15 with inverter frequency power supply. The experimental results show that the dose is dependent on tube voltage, tube current, field size except beyond 20×20cm2, exposure distance, and heel effect. The relationship between dose and tube voltage and exposure distance as well is non-linear, while that between dose and tube current is linear. The non-uniform and non-symmetric dose distribution depends on the heel effect of the x-ray beam. The measured voltage deviating from the default value may reach -2.4% to -9.1% depending on the power supply system used. The dose delivered from the units with inverter frequency power supply is 1.64 times higher than that with single phase power supply.

Low-level proton beams from a van de Graaff accelerator operated at 1-3MeV with proton dose from 1.48 to 94.56mGy using the Rutherford backscattering method were used to study the response of thermoluminescence dosimeter CaF2: Tm. The glow curves, TL output and sensitivity obtained were analyzed with respect to proton energy, dose and dose rate. The experimental results indicate that TLD CaF2: Tm may also be used as a proton dosimeter in the low energy range.

The intrinsic thermoluminescent response to ultraviolet radiation of CaF2:Dy phosphor is enhanced by pre-irradiation high-temperature annealing treatment. The thermoluminescent response is stabilized by adding a medium temperature annealing treatment after the previous annealing. The experimental results show that the annealing treatment of 1 h 850 degrees C high-temperature annealing followed by 1 h 350 degrees C medium-temperature annealing is the optimum treatment to have high thermoluminescent response and good stability. The results also show that (1) the thermoluminescent response to 253.7 nm ultraviolet radiation is increased and stabilized, (2) the thermoluminescent sensitivity and glow curve distribution to 235.7 nm ultraviolet radiation are retained, and (3) the thermoluminescent response to 253.7 nm ultraviolet is linear from 3 to 1 x 10(3) Jm(-2), but there is no linear response with respect to 365 nm ultraviolet.

The fading of three different thermoluminescent (TL) materials, CaF2:Tm (TLD-300), manocrystalline LiF:Mg,Ti (DTG-4) and MgB4O7:Dy,Na has been studied at room temperature and at 50°C of storage. The evolution as a function of the elapsed time of the whole glow curve as well as of the individual peaks has been analysed using the Computerised Glow Curve Deconvolution (CGCD) program developed at the NTHU. The analysis allows to predict the loss of the dosimetric information and to make any correction is necessary for using the TL dosimeters in practical applications. Furthermore, it is well demonstrated that using CGCD it is not necessary to anneal the peaks having a rapid fading to avoid, then, any interfering effect on the more stable peaks.

Some thermoluminescence characteristics of magnesium borate activated by Dy and Na are reported, namely the thermoluminescence (TL) response as a function of the absorbed dose and the fading behaviour. Furthermore, according to the fading results, the hypothesis of a continuous trap distribution is suggested to explain the evolution of the kinetics parameters, i.e. activation energy and kinetics order.

Because of the interaction between two postulated tectonic plates where Taiwan is situated, both earthquake and faults are very common in Taiwan. Due to the intensive studies of thermoluminescence dosimeter (TLD) in Taiwan in the past, TLDs were thought as the first choice for radon measurement at the beginning. Later on cellulose nitrate (CN) films had exclusively been used for radon measurements and the technique thus developed was applied to earthquake prediction and fault identification. A spark counter was developed for counting the alpha tracks in the chemically etched CN film. Other radon detectors such as CR-39 chips and electrets were also investigated for the same purpose. Some field experiments are given for illustration.

Neitaping cold spring is one of the recreation attractions in the northwestern part of Taiwan. It is located in Peipu Village of Hsinchu County about one-hour drive from the National Tsing Hua University. In summer time many tourists enjoy swimming in a small pool specially constructed for recreation purpose. There are several water sources situated in different places around the peal. The cold water flows into a creek called Shangping. All samples were taken from the sources, pool, and along the creek for a period starting in December 1996 and finished sampling in July 1997. During the eight-month monitoring period, electret ion chambers (EICs) have extensively been used.

This study describes the response of the thermoluminescent dosimeter CaF2:Tm to protons from a compact cyclotron with energies between 15 and 30MeV. Glow curve analysis indicates that the response of CaF2:Tm to protons depends on proton energy and proton current.

The aim of this paper is twofold. The first is to present the results concerning the kinetic parameters of a recent preparation of MgB4O7 which has a single well-defined peak. To determine the parameters, i.e., activation energy, E, frequency factor, s, and order of kinetics, b, by several different methods as the initial rise, the variable heating rates, the isothermal decay, the peak shape and the glow curve deconvolution methods. The second goal is to compare the results obtained using chips and powder and to put into evidence the thermal gradient effects on the kinetics parameters when using the variable heating rate.

Three kinds of common plant: bastard banian (Ficus retusa), hsianshih trees (Acacia confusa) and pine trees including their cones grown in semitropical areas were investigated to serve as bio-indicators for 137Cs contamination in soil in Taiwan. Gamma spectroscopy was performed to measure the concentration of 137Cs in soil and different parts of the plants. The results indicate that either the pendent rootlets of the bastard banian or the pine tree including its cones can be used as bio-indicators for environmental radioactivity monitoring. Though the effectiveness of the hsianshih tree as an indicator is known to be inferior to others, its popularity makes it a potential bio-indicator in semitropical area.

Fallout 137Cs activities in soils and trees were measured from samples taken in mountainous areas and along three cross-island highways in Taiwan. Typical concentration in near-surface samples is about 5 Bq kg−1 depending on soil density. No correlation was found between the concentrations of 137Cs and stable elements in soils. Mechanical disturbance and soil density were identified as major causes for redistribution of 137Cs in both forest soils and trees. The transfer coefficient of 137Cs from soil to bastard banian estimated is 0.23.

This paper describes a summary of results in a series of 10 international intercomparisons of environmental dosimeters held during 1974-1993 and another series of domestic Intercomparison studies held in Taiwan during 1980-1984. The field conditions were harsh. Even in semitropical Taiwan where high humidity and temperature in the field is usual, the performance of our TLD could pass all the rigid tests. The ANSI N13-29 (American National Standards Institute publication N13-29) dealing with standards for environmental dosimetry and the Horlick's triangle dealing with the accuracy and the precision of TLD were used to analyze the dosimeterc data.

In the present paper, fading and radiation quality effects on the kinetic parametes of dosimetric peaks were investigated. A nonlinear least-squares numerical fitting program based on the Levenberg-Marquardt algorithm was developed to analyze the glow curves. General-order kinetics formula with a single energy level of traps was adopted as the fitting function. The results indicate that both fading and photon energies have pronounced influence on the kinetic parameters. In the storage times experiments, change in traps distribution due to diffusion at room temperature may be the main reason causing the variations in activation energies. In the different sources experiments, different spatial distributions of trapped charge carries due to the different photoelectric effect of different photon energies may influence the binding energies. Other factors such as trapped charge conversion from one type of trap to another, competing non-radiation defect interaction and different photon energies may be used for interpreting the drift phenomenon of activation energies. Temperature dependence of frequency factor, variations of temperature lag and fluctuation and shift of the distribution frequency factor can be used to interpret the drift phenomenon of frequency factor. Kinetic order variation during the heating stage can also be used to interpret the drift phenomenon of kinetic order. Peak 3 of 55Fe (high LET radiation) irradiated samples exhibits a different character with respect to peak 3 of other source-related glow curves. This may be due to the invalidity of the general-order equation and the increase of retrapping probability.

The aim of this work was to investigate the naturally occurring radionuclides, U-series, Th-series, and 40K in soil samples taken from certain mountainous areas. The sampling sites of interest included the north cross-island highway, the mid cross-island highway, the south cross-island highway, and other major mountainous areas. In addition, cosmic radiation in the mountain, radon in hot springs in the valley, and special areas of interest with higher natural radiation were also investigated. The radioactive mineral named Peitou stone (Hokutolite) found in the streamlets of the Peitou hot spring in the suburb of Taipei shows higher radium content with 226Ra 36 ± 0.74 Bq kg−1 and 228Ra 9.3 ± 0.37 Bq kg−1.

Effective doses from typical radiopharmaceutical examinations were evaluated using new conversion factors based on the latest recommendations of the ICRP. These doses have been combined with information on the frequency of examinations to estimate that the per caput annual effective dose and the annual collective effective dose to the Taiwanese population from all radiodiagnostic examinations involving radioactive labelled materials are about 30 mu Sv and 600 man.Sv, respectively. The results obtained are discussed in terms of the possible radiological impact of the exposures incurred from radiopharmaceuticals and compared with the 1993 UNSCEAR Report.