[en] Plutonium as the other actinides was distributed in the environment as a result of nuclear testing, nuclear fuel production and reprocessing, nuclear accidents and due to a lesser extent accidental releases. Pu aerosols due to wet and dry deposition contaminated environment. It has become necessary to investigate an impact of this actinide on the ecosystems. The first step in that case was to determine the activity level of Pu isotopes in samples material and second to find isotopic composition like: "2"3"8Pu/"2"3"9"+"2"4"0Pu identifies as a fingerprint of nuclear accident. This specific activity ratio for Japanese background (global fallout) was close to 0.03 before FDNPP disaster. Every higher result than those, can be considered as a signal of burned nuclear fuel and due to presence of the other artificial radionuclides (e.g. "1"3"7Cs, "1"3"4Cs, "9"0Sr etc.) can be linked to the Fukushima accident. This study focused on the determination of Pu isotopes in soil samples collected during first few days after FDNPP accident

[en] The National Inst. of Radiological Sciences (NIRS) has developed passive radon (²²²Rn)-thoron (²²⁰Rn) discriminative detectors for a large-scale survey and has established a thoron chamber to calibrate such detectors. In order to establish quality assurance and quality control for the ²²⁰Rn measurement at NIRS, intercomparison studies have been carried out. The intercomparisons using a scintillation cell method, which has been used as a standard for ²²⁰Rn measurement at NIRS, were conducted at New York Univ. (NYU, USA) and Physikalisch-Technische Bundesanstalt (PTB (Germany)). As a result, it was found that the result from the NIRS was in good agreement with that from the NYU. On the other hand, it was observed that the relative discrepancy between the ²²⁰Rn concentrations from the NIRS and PTB monitors was, on average, > 50%. Using the NIRS ²²⁰Rn chamber, the international intercomparison experiment for passive ²²⁰Rn detectors started in 2008. (authors)

[en] Nowadays, artificial 'radon spa sources' for home baths are commercially available. Although these sources could give a potential radiation exposure to the users, few studies have been reported on their radiological measurements. In the present study, five types of radon spa sources were collected and their radiological characterization was investigated. The followings were estimated for these samples: (1) radon emanation coefficients (dry and water-saturated conditions), (2) surface γ-ray dose rate, (3) surface count rates for α- and β-rays, (4) activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, and (5) concentrations of radon and thoron generated from the sources located in an air flow system. The activity concentrations were very high (except for one sample (named 'sample B'), although radon emanation coefficient was low compared with soil. This leads to high concentrations of radon/thoron generated from the sample. The maximum surface γ-ray dose rate was observed for sample A (2.7 μGy h^-1). If people stay very close to the sample for a long time, the exposure might be significant. (author)

[en] Room experiments were conducted to investigate the effects of an air cleaner on radon mitigation. Radon concentration, equilibrium equivalent radon concentration and unattached fraction were measured during the experiments. Two types of filtration were tested using the air cleaner which has a high efficiency particulate air filter (HEPA-filter) and a deodorizing activated carbon (carbon-filter). One is the filtration with the HEPA-filter plus carbon-filter and the other is the filtration with only the HEPA-filter. The effective doses from radon progeny were significantly decreased. Both filtration methods were effective for the mitigation of effective dose due to radon progeny. (author)

No abstract available

[en] From the viewpoint of radiation protection, determination of natural radionuclides e.g. thorium and uranium in soil samples are important. Accurate methods for determination of Th and U is gaining importance. The geochemical behavior of Th, U and rare earth elements (REEs) are relatively close to one another while compared to other elements in geological environment. Radioactive elements like ²³²Th and ²³⁸U along with their decay products (e.g. ²²⁶Ra) are present in most of the environmental matrices and can be transferred to living bodies by different pathways that can lead to sources of exposure of man. Therefore, it is necessary to monitor these natural radionuclides in weathered soil samples to assess the possible hazards. The activity concentrations of ²²⁶Ra, ²²⁸Th, and ⁴⁰K in soils have been measured using a g γ-ray spectroscopy system with high purity germanium detector. The thorium, uranium and REEs were determined from the same sample using inductively coupled plasma mass spectrometry (ICP-MS). Granitic rocks contain higher amounts of Th, U and light REEs compared to other igneous rocks such as basalt and andesites. Therefore, it is necessary to understand the interaction between REEs and nature of soils, as soils are complex heterogeneous mixture of organic and inorganic solids, water and gases. In this paper, we have discussed about distribution pattern of ²²⁶Ra, ²³²Th and ²³⁸U along with REEs in soil samples of weathered acid rock (granite and ryolite) collected from two prefectures in Japan: 1. Gifu and 2. Okinawa. (author)

[en] Intercomparisons of radon/thoron detectors play an important role not only for domestic radon/thoron survey but also for international or inter-regional discussion about radon/thoron mapping in dwellings as well as that in the soil. For these purposes, it is necessary to improve and standardise technical methods of measurement and to verify quality assurance by intercomparisons between laboratories. Therefore, the first thoron international intercomparison was provided at the NIRS (National Inst. of Radiological Sciences (Japan)) thoron chamber with a 150 dm³ inner volume. In addition, a second intercomparison of radon detectors was conducted at NIRS with a 24.4 m³ inner volume walk-in radon chamber. Only etched-track detectors were used during thoron intercomparison as well as three types for the radon intercomparison: etched track, charcoal and electret. In general, 45% results for thoron experiment do not differ more than 20% from the reference value of thoron concentration and 69% for radon. (authors)

[en] The main aim of this present study is to evaluate the level of thorium and uranium activity as well as rare earth elements in a natural high background radiation area (HBRA) near Chhatrapur of Orissa state in India. Soil samples collected from HBRA were analyzed by γ-ray spectrometry as well as inductively coupled plasma mass spectrometry (ICP-MS). The radioactivity is found to be mainly contributed from thorium. Concentration of thorium and TiO₂ is reported to be very high compared to normal abundance in crystal rocks. A large variation in absorbed gamma dose in air was observed

[en] An extraordinary earthquake of magnitude 9.0 followed by Tsunami on 11 March 2011 caused serious nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP) about 250 km north to Tokyo, capital of Japan. This resulted in radioactive contamination due to deposition of long-lived radionuclides. Contaminated soil can cause an enhanced radiation exposure even after many years. Depending upon environmental conditions radionuclides can be mobilized to aquatic systems. Therefore, the fate and transfer of these radionuclides in the soil water system is very important for radiation protection and dose assessment. In the present study, emphasis has been given on isotope ratio measurement of uranium that may give some idea about its contamination during accident. Soil and water samples were collected from contaminated areas around FDNPP. Inductively coupled plasma mass spectrometry (ICPMS) is used for total uranium concentration and thermal ionization mass spectrometry (TIMS) has been used for uranium isotopes measurement. Extraction chromatography has been used for the separation of uranium. We have observed, isotope ratio ²³⁵U/²³⁸U is of natural origin, however in a few soil samples ²³⁶U has been detected. For the migration behavior, its distribution coefficient (K_d) has been determined using laboratory batch method. Depleted uranium is used as tracer for uranium K_d estimation. Chemical characterization of soil with respect to different parameters has been carried out. The effect of these soil parameters on distribution coefficient of uranium has been studied in order to explain the radionuclide mobility in this particular area. The distribution coefficient values for uranium are found to vary from 30-35679 L/Kg. A large variation in the distribution coefficient values shows the retention or mobility of uranium is highly dependent on soil characteristics in the particular area. This variation is explained with respect to pH, Fe, Mn, CaCO₃ and organic content. There is a very good correlation of uranium K_d obtained with Fe content. There is a variation with uranium activity ratio whereas no enrichment of ²³⁵U has been noticed in the studied area. However, contaminated water used for cooling the reactor vessel stored near the reactor after accident, may contain radioactive uranium. Therefore, it is of concern to understand leaching of U in the groundwater system. In that context, this study will be very much useful. Document available in abstract form only. (authors)

[en] Characteristics of radon and its progeny were investigated in different air conditions by turning four types of indoor air appliances on and off in a two-story concrete Japanese dwelling. The four appliances were air conditioner, air cleaner, gas heater and cooker hood. The measurements were done using two devices: (1) a Si-based semiconductor detector for continuous measurement of indoor radon concentration and (2) a ZnS(Ag) scintillation counting system for equilibrium-equivalent radon concentration. Throughout the entire experiment, the cooker hood was the most effective in decreasing indoor radon concentration over a long period of time and the less effective was the air conditioner, while the air cleaner and gas heater did not affect the concentration of radon. However, the results measured in each air condition will differ according to the lifestyles and activities of the inhabitants. In this study, indoor radon and its progeny in a Japanese dwelling will be characterised by the different air conditions. (authors)