Tradescantia (clone KU-7) were grown at three points near a site of nuclear power plants and somatic mutation frequencies in Tradescantia stamen hairs were investigated for three years. The two points are located in the prevailing down-wind sector of the site. Mutational events in stamen hair cells were scored every day from the end of April to October for three years. In parallel with this observation, factors which have been thought to affect mutation induction, such as temperature, humidity, insolation, pollutants, radioactivity in the buds were measured at the three points. The daily exposure and radioactive concentration at three points due to the amount of the radioactive nuclide released from the nuclear power plant were calculated. Mutation frequencies fluctuated daily, but they were estimated rather constant on average at three sites. Increase of radioactivities in the buds or other plant tissues was not detected during this experiment. The daily exposure and radioactive concentration were very low, for example, the ratio of the maximum daily exposure to the doubling dose was less than 1×10-7. It has been definitely shown by this field experiment that radionuclide released from the nuclear power plants can not induce significant mutation of Tradescantia. It was concluded that Tradescantia stamen hair system was not appropriate to monitor the environmental radiation from the power reactor.
In this paper, the possibility of the biological monitoring by Tradescantia for radiation effluents from a power reactor site is considered. Data for analysis were obtained through the experimental study which had been conducted by Expert Committee on Biological Effects of Environmental Radiation and carried out from 1979 to 1981 near to Takahama Nuclear Power Plant in Fukui Prefecture. Measurements had been taken on the mutation frequency in Tradescantia stamen hairs and environmental factors including evaluated radioactive airborne effluents, natural airborne radioactivity, weather conditions and air pollution indices. This paper is coupled with Yamaguchi et al. (1985); while the latter tackles the problem, mainly by comparing the observed (calculated) concentration levels of radioactive effluents with biological thresholds, this paper presents the results of statistical data analysis which revealed the following: (1) There is highly significant negative correlation between temperature before blooming and mutation frequency. (2) After adjusting the effect of temperature, there is no significant association between radioactive effluents and mutation frequency.
Two Important problems about commonly-used neutron rem-counter have been discussed in evaluating the neutron dose equivalent in pulsed and mixed radiation fields around an electron linear accelerator. One is the overestimate of dose equivalent due to false pulses generated by intense burst X-rays. In order to eliminate the false pulses, three techniques based on (1) anti-coincidence counting, (2) pulse height discrimination, and (3) correction factor have been employed. It was pointed out that the first technique was most effective and the third was most convenient for practical applications. The other problem is the underestimate of dose equivalent due to counting loss in a high-fluence-rate field. It was confirmed that the time variation of counting rate was an important factor for dead-time correction in pulsed radiation fields. A comparison between dose equivalent values evaluated with rem-counter and those with Indium activation detector has also been carried out. A validity of proposed correction methods was confirmed from the experimental results of the proportionality of the corrected dose equivalent values to the relative activity of Indium detectors.
A method for estimating the gamma-ray exposure received by non-occupational persons was devised. The method is based on the idea of using bearing quartz oscillator from the wrist watch, as monitor sample for tests on their thermoluminescence (TL). An average coefficient of variation in 15 samples was about 13% of the mean yield. The TL intensity from the quartz oscillator per 100R was from about 0.05 to 3 times of the background noise from the TLD reader.
The concept of population dose is of importance and of interest at the point of radiation protection of puplic. We devided it into two categories, source-related population dose and individual-related population dose, and estimated each population dose of Japan. We surveyed all sources that caused exposure to Japanese population. A number of sources, both naturally-occuring and man-made, contributed to population exposure. According to source-related dose assessment, average annual effective dose equivalent was about 3.3mSv, and about half of which, i. e. 1.6mSv, was given from medical exposure. And from the results of individual-related dose assessment we proposed the allocation of the annual dose limit of public for each controllable source, that is, 2.5mSv/yr to nuclear faculties, 1.0mSv/yr to miscellaneous sources, 1.5mSv/yr to probablistic exposure.