[en] To elucidate the various characteristic and their availabilities of the radioactivity and negative air ion originated from an artificial thoron hot spring, we simulated a hot spring, we simulated a hot spring condition using a monazite powder and measured the negative air ions and radioactivities in the condition. In the result, the radioactivity of the thorium series nuclide (²⁰⁸Tl) in monazite was 5.3 times of that of the uranium series nuclide (²¹⁴Bi). For the pH(3.5-12.5) dependence of the leaching nuclides from monazite in water, the thorium series nuclides (²²⁸Ac, ²¹²Pb) were well leached on the strong acid side because the monazite includes the rare earth element (REE) which was high ionization tendency and was substituted by the radioactive nuclide. On the other side, the uranium series nuclides (²¹⁴Bi, ²¹⁴Pb) leached in water were not detected because the specific activities of the uranium series nuclide are lower relative to those of the thorium series nuclide. Moreover, there were many negative air ions originated from monazite in the place within 10 cm away from the monazite surface. This is suggested that most negative ions exist within the range of the radiated α rays. Negative air ions increased with increasing atmospheric relative humidity (35-60%). This is suggested that negative air ions stably existed in the hydration type such as O₂-bar(H₂O)_n. Furthermore, for the hydrous rate dependence of the negative air ions originated from monazite, the negative air ions without supernatant fluid were larger than those with supernatant fluid, because α rays ionized water on the surface of monazite. (author)

[en] Radon emanation means the escape of radon atoms from solid grains into pore space; it is the very first process that may lead to radon exposure in the environment. Experimental and numerical studies of radon emanation have been diligently carried out since its recognition as a carcinogen. Our previous review of the measured data showed a wide range of radon emanation fractions from natural substances, and then we discussed the effects of environmental factors such as pore water. The present paper provides an overview of the approaches and progress of radon emanation modeling that may be useful for the interpretation of measured data. Recoil and/or diffusion of radon in solid following alpha decay of radium, which underlies the mechanisms of radon emanation, have been incorporated into numerical models. In the calculation based on recoil-based emanation, radium distribution and pore size were the most important parameters, which govern the magnitudes of radon ejections from the birth grain and of radon embedding into another solid surface, respectively. The solid diffusion appeared significant only at a temperature higher than several hundred degrees Celsius. A model is now desired to be developed that incorporates the transport process of radon atoms that are still settled in solid after alpha recoil, considering radiation damage and its resulting inner path network. (author)

[en] Many studies of background levels in gamma-ray measurements using a high-purity germanium detector have been reported from various aspects such as its reduction and variation. In the present work, natural gamma-ray background was thoroughly measured in a year (283.5 days in total, n=271). One measurement time was almost all either 86,400 sec (1 day) or 100,000 sec. The data was first discussed in relation to radon concentrations in the laboratory. No correlations were found between the gamma-ray count rates from "2"1"4Pb and "2"1"4Bi and radon concentrations, meaning that radon just around the germanium detector was reduced to the negligible level by the introduction of nitrogen gas. Also, the count rates of major nuclides appeared to fluctuate with the normal distribution or its similar distribution, without seasonal variations. The coefficient of variance of a few up to several tens of percent was seen, which were larger than those calculated from counting statistics alone. Furthermore, summing of all gamma-ray spectra allowed us to see neutron-induced peaks that cannot be detected in usual short-term measurements. All data obtained here would be the knowledge useful for the practice of gamma-ray measurements. (author)

[en] This paper gives an outline of the current status of uranium measurements and their related techniques at the Ningyo-toge Environmental Engineering Center of Japan Atomic Energy Agency. The JAWAS-N and the Q"2 system have been adopted to evaluate uranium contents in the wastes. About 10 g or more of uranium in a 200 ℓ drum can be evaluated by these systems. The equivalent model developed to correct the evaluation results with Q"2 system is not available to less than dozens of grams of uranium in a 200 ℓ drum. The paper illustrates the advantage of use of the improved equivalent model which evaluates uranium content from full energy peak of 1001 keV and its Compton spectrum in order to correct the inhomogeneous distribution of uranium in measuring objects. The use of model achieved the limit of uranium quantitative determination under one tenth of those of previous evaluation methods. To determine U-235, it was demonstrated that the shielding factor, X_g_e_o_m_e_t_r_y for evaluation of 1001 keV gamma-ray is also possible to use for evaluation of 186 keV gamma-ray. The measurement systems adopting the model have been introduced to other nuclear operators in Japan. In addition, it is also examined to use for clearance. As a related technique, feasibility studies on machine learning algorithms have been performed to classify the waste drums depending on their gamma-ray spectrum. (author)

[en] Ambient dose rates are continuously monitored in Ningyo-toge Environmental Engineering Center, Japan Atomic Energy Agency. The present study discussed the variations in ambient dose rates, observed from April 2014 to March 2015, due to snowfall as well as rainfall. It is much snowy as one of climatic features in this area. Rain or snow was sampled for a certain period in the day of interest (17 cases in total), and then the concentration of radon progeny was measured. With the measured data, the variation in ambient dose rate was calculated considering the accumulation of the radon progeny on the ground. As a whole, this calculation was found to reasonably reproduce the time trends of observed dose rates, except for four cases. Based on the backward trajectory analysis, it was explained that the discrepancy in two cases out of the four was induced by changes of radon progeny concentration in precipitation around sampling period. It was suggested that the other two cases were caused by the run-off of rain from the ground surface. (author)

[en] Tottori University and Japan Atomic Energy Agency started a joint study to develop an environmental remediation technique for agricultural soil. Nine plants were water-cultured and examined for screening. A few were selected as candidates for demonstrations in fields. Preselected plants were mainly halophytes that can specifically absorb more Na than K, and others like sunflower demonstrated for domestic large-scale tests. Easily cultivated and harvested plants without harmful effect on new agriculture were also considered. Seedings prepared were first grown for a certain term. Additive-free, ¹³³Cs and ⁸⁸Sr groups, which are both stable isotopes, were then made. Cs (CsCl) and Sr (SrCl₂·6H₂O) contents in cultures were 1.6836 mg/L (0.01 mM) and 266.62 mg/L (1 mM), respectively. Stems, leaves and roots were harvested, in principle, two weeks after the addition, to measure K, Ca, Mg, Sr and Cs concentrations in them. Considering the examination period, a content rate (i.e. element amount per dry sample weight) was regarded as an index. It was concluded that New Zealand spinach and ice plant were most adequate for removing contaminants from surface soil. The two accumulate Cs and Sr mostly in the shoots, are prostrate, and spread the roots shallowly. For valid application, growth-phase dependences of absorption and distribution, growth property and root distribution should be elucidated. Plants that meet the present purpose are ones that specifically absorb object substances, or that show normal absorption but high removal rate per area due to the large bulk size. The latter view also needs to be evaluated when the field test is conducted, since developing stages of the plants used in the present work were not correspondent. Finally, the application study plan was developed based on the screening test results. (author)

[en] Radon inhalation using our radon exposure device activated anti-oxidative function in some organs of mouse. To assess the possibility of its application to veterinary care, healthy dogs and cats with chronic renal failure were inhaled radon at a concentration of 5500 Bq/m³ for 30 minutes every 2 days for 30 days. In result, radon inhalation within a relatively long time period significantly decreased the triglyceride level of dogs. On the other hand, some cats increased the volume of drinking water by radon inhalation and the creatinine level in blood of these cats was decreased to normal level. These findings suggest that radon inhalation may have curative properties against chronic renal failure. (author)

[en] We isolated the luminous bacterium Vibrio phosphoreum H1 as a tool for education in radiation safety. It emits strong and steady luminescence. It is nonpathogenic, cannot be grown under normal low-salt conditions, and can be handled without any special equipment or reagents. We can cultivate it on a desk at room temperature, and can use a home-made broth containing a high salt concentration. Heat treatment at 37°C kills the bacterium, leading to its loss of luminescence. Although X-ray irradiation clearly kills it as the exposure dose increases, luminescence remains intact for some time, suggesting a delayed appearance of the biological effect of radiation exposure. We showed that the luminous bacterium Vibrio phosphoreum H1 can be used as a tool for teaching and learning about the effects of radiation. We proposed a practical plan that can be employed at high schools as well as universities. (author)

No abstract available

[en] There are a lot of life style diseases that are related to reactive oxygen species in indications of the radon therapy, and, the further clarification of mechanism is expected. Therefore, in this study, we investigated the activation of antioxidation function in some organs of mice by radon inhalation using the new radon exposure device. It was enable that this device was the adjustments of radon concentration by changing the air flow rate to the specially processed radon source and so on. The mice were made to inhale the radon of 400 Bq/m³ or 4000 Bq/m³ with this device. Results show that in brain, lungs, liver, and kidney, both the activities of superoxide dismutase (SOD) and catalase increased, and lipid peroxide levels decreased. This suggests that radon inhalation enhanced the antioxidation function. These findings are important in understanding the mechanism of diseases in which radon therapy is used as treatment, and most of which are called activated oxygen-related diseases. (author)