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The purpose of this study was to estimate the uncertainty in the dose distribution for the (125)I source STM1251, as measured with a radiophotoluminescent glass rod dosimeter and calculated using the Monte Carlo code EGS5 in geometry that included the source structure reported by Kirov et al. This was performed at a range of positions in and on a water phantom 18 cm in diameter and 16 cm in length. Some dosimetry positions were so close to the surface that the backscatter margin was insufficient for photons. Consequently, the combined standard uncertainty (CSU) at the coverage factor k of 1 was 11.0-11.2% for the measurement and 1.8-3.6% for the calculation. The calculation successfully reproduced the measured dose distribution within 13%, with CSU at k ≤ 1.6 (P > 0.3). Dose distributions were then compared with those for the (125)I source Oncoseed 6711. Our results supported the American Association of Physicists in Medicine Task Group No. 43 Updated Protocol (TG43U1) formalism, in which STM1251 dose distributions were more penetrating than those of Oncoseed 6711. This trend was also observed in the region near the phantom surface lacking the equilibrium radiation scatter conditions. In this region, the difference between the TG43U1 formalism and the measurement and calculation performed in the present study was not significant (P > 0.3) for either of the source models. Selection of the source model based on the treatment plans according to the TG43U1 formalism will be practical., (© The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.)

The aim of this study is to demonstrate the feasibility of estimating the strength of the moving radiation source during patient implantation. The requirement for the counting time was investigated by comparing the results of the measurements for the static source with those for the source moving at 2, 5, 10 and 20 cm s(-1). The utilized source was (125)I with an air-kerma strength of 0.432 U (μGym(2)h(-1)). The detector utilized was a plastic scintillation detector (8 cm × 5 cm × 2 cm in thickness) set at 8 cm away from the needle to guide the source. Experiments were conducted in order to determine the most desirable counting time. Analysis using the maximum of the measured values while the source passed through the needle indicated that the results for the moving source increased more than those for the static source as the counting time decreased. The combined standard uncertainty, with the coverage factor of 1, was within 4% at the counting time of 100 ms. This investigation supported the feasibility of the method proposed for estimating the source strength during the implantation procedure, regardless of the source speed. The method proposed is a potential option for reducing the risk of accidental replacements of sources with those of incorrect strengths.

The effects of solar radiation on the ESR signals in human tooth enamel were investigated. Enamel samples were exposed to the sunlight in Hiroshima, Japan, on sunny days for a total of about 228 hours over one year. The intensity of the illuminating sunlight was measured with a light meter, which then was converted to the intensity of the solar radiation. Three types of signals caused by the solar radiation were identified. The signal named S1 is identical to the gamma ray radiation-induced axially symmetrical signal and contains two signals S1( perpendicular) and S1(//) corresponding to the perpendicular and parallel components of the g-tensor characterized by g( perpendicular) = 2.0018 and g(//) = 1.9975 respectively. In addition, two other peaks named S2 and S3 are induced by the solar radiation. S2 is very near the inherent signal with g = 2.0052, possibly created by the same paramagnetic centers as the natural signal, and S3 is a weaker signal with g = 2.010. On increasing the amount of solar radiation S1 increases linearly, but S2 and S3 reach saturation. The average effect of the solar radiation on the S1( perpendicular) signal is estimated by dose equivalent gamma ray irradiation as 7.8 +/- 0.5 mGy (MJ m(-2))(-1), which corresponds to 19.6 +/- 1.3 mGy h(-1) at the latitude of Hiroshima. Signals S2 and S3 may be used to recognize the effect of solar radiation on the enamel.

A characteristic hot-filament type X-ray generator was constructed for irradiation of cultured cells. The source provides copper K, iron K, chromium K, molybdenum L, aluminium K and carbon K shell characteristic X-rays. When cultured mouse m5S cells were irradiated and frequencies of dicentrics were fitted to a linear-quadratic model, Y = alphaD + betaD2, the chromosomal effectiveness was not a simple function of photon energy. The alpha-terms increased with the decrease of the photon energy and then decreased with further decrease of the energy with an inflection point at around 10 keV. The beta-terms stayed constant for the photon energy down to 10 keV and then increased with further decrease of energy. Below 10 keV, the relative biological effectiveness (RBE) at low doses was proportional to the photon energy, which contrasted to that for high energy X- or gamma-rays where the RBE was inversely related with the photon energy. The reversion of the energy dependency occurred at around 1-2 Gy, where the RBE of soft X-rays was insensitive to X-ray energy. The reversion of energy-RBE relation at a moderate dose may shed light on the controversy on energy dependency of RBE of ultrasoft X-rays in cell survival experiments.

There are still many differences in dose estimates depending on the applied methods of retrospective dosimetry in the areas, which were affected by nuclear tests at the Semipalatinsk nuclear test site (SNTS). In order to provide more correct estimation of radiation doses to population in proximity to the SNTS an International Intercomparison of Retrospective Luminescence Dosimetry (RLD) method had been proposed. It was suggested there be a comparison of the dose estimates for the brick samples from the buildings in the settlement, suffered following nuclear tests at the SNTS. With this purpose, during the September-October 2002 field mission, the team of specialists from Kazakhstan and Japan had collected four whole bricks for RLD International Intercomparison. Three buildings were selected as sampling locations in Dolon' village (Kazakhstan). The slices from these bricks were distributed between six laboratories in Finland, Germany, Japan, Russia, UK and USA for independent estimations by the RLD method of the accumulated dose of external irradiation. The descriptions of sampling, locations, data on geographical coordinates, dates of building construction, mode of cutting of samples for distribution, labeling, condition of transportation, order of the distribution of samples and information concerning 137Cs and 239+240Pu soil contamination density in the village and near sampling locations are presented in the paper.

We have applied the thermoluminescence dosimetry technique to measure the total external dose from all the nuclear explosions in a few locations near the Semipalatinsk nuclear test site in Kazakhstan. The technique was optimized at our laboratory by fundamental study of the method of thermoluminescence dosimetry. The measured values of each sample at 10 mm depth were 248+/-102 mGy (KSD-1), 30+/-76 mGy (2(1-3)), 222+/-63 mGy (2(3-2)), 217+/-55 mGy (2(4-1)). The results are part of an international intercomparison exercise using bricks collected from the areas surrounding the Semipalatinsk nuclear test site.

Residual 152Eu activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 m in the slant range and one control sample at 2,850 m from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of 152Eu are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of 60Co and 36Cl. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for 152Eu are also discussed.

Residual 60Co activity in five steel samples induced by neutrons from the Nagasaki atomic bomb has been measured within about 1000 m from the hypocenter. The chemical separation of cobalt and nickel from steel samples was performed, and cobalt-enriched samples were prepared for all samples. Gamma-ray measurements were carried out with a low-background well-type germanium detector. The gamma-ray spectra for five samples were compared with the spectrum of a control sample to ensure that the observed 60Co was actually induced by A-bomb neutrons. The activation of cobalt by environmental neutrons was also investigated. It has been shown that the present 60Co data are consistent with earlier Hashizume's data.

A criticality accident occurred at a uranium conversion facility in Tokai-mura, Japan on September 30, 1999, and fission neutrons were continuously emitted for about 20 hours. Materials of stainless steel or iron, and chemical reagents were collected at places between 2 m and 270 m from the criticality accident site on October 25 and 26, 1999, November 27, 1999 and February 11, 2000. Neutron-induced radionuclides. such as 54Mn and 58Co, in the materials exposed to fast neutrons from the accident were measured to estimate the neutron fluences and energy distributions. Highly sensitive y-ray spectrometry with a well-type Ge detector was performed after radiochemical separation of Mn and Co from the materials. An instrumental neutron activation analysis was mainly applied for determinations of the target elements and chemical yields. The concentrations of 54Mn and 58Co in a mesh screen of stainless steel collected at a location 2.0 m from the accident site were determined. The total number of fission events was evaluated to be 2.5 x 10(18) by Monte-Carlo calculations of neutron transfer by considering the observed values of 54Mn and 58Co. The results presented here are fundamental to estimate the neutron doses at various distances.

The validity of a method for individual dose reconstruction based on the anisotropic radiation distribution was confirmed by a comparison with the dose from Na-24 whole-body counting for seven persons at a neighboring company located on the western side of the JCO campus. The successful coincidence between Di (Na-24) and Di (present) also supports the validity of the second version of D(r) reported by the Head Office of Countermeasure. The present dose reconstruction for the 350 m zone at the western side showed an average value of 0.7 mSv and a maximal value of 3.1 mSv, as indoor-dose under the assumption of an effective transmittance of 0.4 for all of the houses. If all of the residents in 350 m zone were indoors during the accident, 83% of them might have received external doses of less than 1 mSv. The radiation exposure to the nearest residential area in the southern-west direction was significantly reduced with phi(theta(i)) between 0.4 and 0.2 by several buildings on the JCO campus. The present study on the public dose confirms that the official report on the public dose (the maximal value of 21 mSv for individual doses) from Head Office of Countermeasure is significantly overestimated due to their isotropic treatment of radiation from the source.

There has been a large discrepancy between the Dosimetry system 1986 (DS86) and measured data, some of which data in Hiroshima at about 1.5 km ground distance from the hypocenter are about 10 times larger than the calculation. Therefore its causes have long been discussed, since it will change the estimated radiation risks obtained based on the Hiroshima and Nagasaki data. In this study the contradiction was explained by a bare-fission-neutron leakage model through a crack formed at the time of neutron emission. According to the present calculation, the crack has a 3 cm parallel spacing, which is symmetric with respect to the polar axis from the hypocenter to the epicenter of the atomic bomb. We made also an asymmetric opening closing 3/4 of this symmetric geometry, because there are some data which shows asymmetry. In addition, the height of the neutron emission point was elevated 90 m. By using the asymmetric calculation, especially for long distant data located more than 1 km, it was verified that all of the activity data induced by thermal and fast neutrons, were simultaneously explained within the data scattering. The neutron kerma at a typical 1.5 km ground distance increases 3 and 8 times more than DS86 based on the symmetric and asymmetric model, respectively.

The relative biological effectiveness (RBE) of 252Cf neutrons and synchrotron-generated high-energy charged particles for mutation induction was evaluated as a function of linear energy transfer (LET), using the loss of heterozygosity for wing-hair mutations and the reversion of the mutant white-ivory eye-color in Drosophila melanogaster. Loss of heterozygosity for wing-hair mutations results predominantly from mitotic crossing over induced in wing anlage cells of larvae, while the reverse mutation of eye-color is due to an intragenic structural change (2.96 kb-DNA excision) in the white locus on the X-chromosome. The measurements were performed in a combined mutation assay system so that induced mutant wing-hair clones as well as revertant eye-color clone can be detected simultaneously in the same individual. Larvae were irradiated at the age of 3 days post oviposition with 252Cf neutrons, carbon beam or neon beam. For the neutron irradiation, the RBE values for wing-hair mutations were larger than that for eye-color mutation by about 7 fold. The RBE of carbon ions for producing the wing-hair mutations increased with increase in LET. The estimated RBE values were found to be in the range 2 to 6.5 for the wing-hair. For neon beam irradiation, the RBE values for wing-hair mutations peak near 150 keV/micron and decrease with further increase in LET. On the other hand, the RBE values for the induction of the eye-color mutation are nearly unity in 252Cf neutrons and both ions throughout the LET range irradiated. We discuss the relationships between the initial DNA damage and LET in considering the mechanism of somatic mutation induction.

Dosimetry studies have been made for neutrons from a neutron generator at Hiroshima University (HIRRAC) which is designed for radiobiological research. Neutrons in an energy range from 0.07 to 2.7 MeV are available for biological irradiations. The produced neutron energies were measured and evaluated by a 3He-gas proportional counter. Energy spread was made certain to be small enough for radiobiological studies. Dose evaluations were performed by two different methods, namely use of tissue equivalent paired ionization chambers and activation of method with indium foils. Moreover, energy deposition spectra in small targets of tissue equivalent materials, so-called lineal energy spectrum, were also measured and are discussed. Specifications for biological irradiation are presented in terms of monoenergetic beam conditions, dose rates and deposited energy spectra.