The recommended annual limit of equivalent dose to the lens of the eye has decreased to 20 mSv y−1 from the current limit of 150 mSv y−1. In terms of occupational exposure to radiation workers, exposure inhomogeneity plays an important role when estimating equivalent dose to the eye lens from readings of dosimeters worn by workers on their trunk. The authors focused on homogeneous exposure situations that radiation workers may encounter in nuclear and accelerator facilities. Moreover, the authors investigated how radiation workers are exposed non-homogenously in homogeneous exposure scenarios, where radiation workers may usually be encountered, regardless of their radiation works. In our previous study, we proposed a methodology to quantitatively evaluate the inhomogeneity of exposure. The homogeneity of exposure was evaluated by performing Monte Carlo calculations with a mathematical phantom under the isotropic and rotational irradiation geometries due to gamma and beta rays. Hp(3)eye/Hp(10)trunk exceeded 1.0 even in the case of homogenous exposure to gamma rays. Even in the homogeneous exposure scenarios, the Hp(3)eye might exceed the revised annual dose limit for radiation workers who are exposed close to annual dose limit. For exposure due to beta rays from 90Y, the equivalent dose of the lens of the eye might overestimate around four times when estimated from the Hp(0.07) measured on worker’s trunk.
In case of a measurement of reference air kerma rate for 192Ir HDR brachytherapy, source geometry factor ksg is required to correct the response of a well-type chamber. In this work we determined ksg by actual measurement using three sources (mHDR-V2, VS2000, Ir2.A85-2), which are used at Japanese hospitals. The correction factors to convert the calibration coefficient for mHDR-V2 to that of others were calculated to be 0.987 and 1.002, respectively. Since well-type chambers are calibrated using mHDR-V2 source in Japan, these correction factors enable Japanese users to measure reference air kerma rate of another source types.
Cosmic ray dose rate measurements were performed inside 25 reinforced concrete castle towers using a NaI(Tl) scintillation spectrometer. Approximating the shape of each tower with a multi-cylinder, a bulk density was calculated using inside/outside ratio of dose rate. The evaluated bulk density was multiplied by the volume of the tower to obtain its weight. The data of each tower necessary for analyses were elevation, total floor space, volume, outside and inside dose rates. Those data were listed along with the corresponding calculated bulk density and weight.
Soil samples were collected around the uranium deposit of Kitongo to determine activity concentrations of 238U, 232Th and 40K using a NaI(Tl) detector. Ambient dose equivalent rates were measured using a survey meter. 222Rn-220Rn discriminative measurements were performed using passive type monitors. The activity concentrations of 238U, 232Th and 40K ranged from 20±5 to 337±78 Bq kg−1, 14±4 to 53±13 Bq kg−1 and from 21±4 to 897±190 Bq kg−1 respectively, with the average values of 99±24, 27±4 and 592±125 Bq kg−1, respectively. Ambient dose equivalent rates ranged from 0.05 µSv h−1 to 6.20 µSv h−1. Higher values were recorded inside the two galleries of the uranium deposit. The maximum dose to prospective miners was calculated to be 15.2 mSv y−1. In case of the miner staying permanently inside the galleries, the external dose received would vary from 32 to 54 mSv y−1 with an average of 43 mSv y−1. Radon concentrations ranged from 416±13 to 523±14 Bq m−3 with the average value of 486±14 Bq m−3. Occupational inhalation dose ranged from 2.8 to 3.5 mSv y−1 with an average value of 3.2 mSv y−1.
The specific activity of natural origin to be less than 10 nCi/g (370 Bq/g) given by BSS in IAEA in 1962 plays the key roll in waste acceptance criteria for nuclides of natural origin. This paper extends the application of the specific activity concentration of 10 nCi/g(370 Bq/g) to the waste disposal containing trans-uranium elements. Such criteria is by chance discussed in the peak time of cold war competition, namely, mass production of PIT, a crucial part of warhead in nuclear weapon. AEC in U.S. was faced to solve the Pu bearing waste disposal problem with rational and acceptable level to dispose most of the waste safely in shallow burials. Then again the number of 10 nCi/g (370 Bq/g), a typical radium concentration in the crust quoted again to receive the consensus. Although it is somewhat rough, it may have some secret power to be accepted by the public. This report investigates the details of what happened in the cold war time and how the U.S. government agencies cleared the obstacles.
Radiation imaging technology is a promising research tool in plant science. In this review, we introduce the principles and applications of radiation imaging technology for plant science that is currently available. Specifically, static imaging methods such as radioluminography and microPIXE, and also dynamic imaging methods such as real-time radioisotope imaging system (RRIS), positron imaging and Compton camera are described.
This paper explains the derivation and application of uncertainty in measurement and related characteristic limits, including decision threshold, detection limit, and upper and lower limits of coverage interval, for low radioactive concentration measurement according to ISO 11929. These concepts are organized especially for clearance measurement, which is performed to evaluate materials to be released from control as radioactive waste.