Detailed deposition density maps constructed by large-scale soil sampling for gamma-ray emitting radioactive nuclides from the Fukushima Dai-ichi Nuclear Power Plant accident.
Soil deposition density maps of gamma-ray emitting radioactive nuclides from the Fukushima Dai-ichi Nuclear Power Plant (NPP) accident were constructed on the basis of results from large-scale soil sampling. In total 10,915 soil samples were collected at 2168 locations. Gamma rays emitted from the samples were measured by Ge detectors and analyzed using a reliable unified method. The determined radioactivity was corrected to that of June 14, 2011 by considering the intrinsic decay constant of each nuclide. Finally the deposition maps were created for (134)Cs, (137)Cs, (131)I, (129m)Te and (110m)Ag. The radioactivity ratio of (134)Cs-(137)Cs was almost constant at 0.91 regardless of the locations of soil sampling. The radioactivity ratios of (131)I and (129m)Te-(137)Cs were relatively high in the regions south of the Fukushima NPP site. Effective doses for 50 y after the accident were evaluated for external and inhalation exposures due to the observed radioactive nuclides. The radiation doses from radioactive cesium were found to be much higher than those from the other radioactive nuclides.
Effective dose conversion factors in paediatric interventional cardiology.
Conversion factors for effective dose (CF(E) = effective dose/dose-area product (mSv (Gy cm2)(-1)) in paediatric interventional cardiology were estimated retrospectively for 249 patients using the dose-area product (DAP), irradiation geometry, exposure parameters and tissue-weighting factors (TWFs) from the International Commission on Radiological Protection (ICRP) 60. Two methods for estimating the conversion factors, which differed in the description of the irradiation geometry, were evaluated. The effective doses obtained with the two methods were almost identical. The results showed that irradiation geometry had no significant impact on the CF(E), and a single factor was defined for both diagnostic and interventional examinations. In addition, the effect of the new tissue-weighting factor for breast tissue (TWF(b)) given in ICRP 103 on the effective dose was assessed. The CF(E) was 3.7+/-0.2 mSv (Gy cm2)(-1) (neonate), 1.9+/-0.2 mSv (Gy cm2)(-1) (1 year), 1.0+/-0.1 mSv (Gy cm2)(-1) (5 years), 0.6+/-0.1 mSv (Gy cm2)(-1) (10 years) and 0.4+/-0.1 mSv (Gy cm2)(-1) (15 years). Applying these CFs to the individual DAP values of each patient yielded mean effective doses of 13.0 mSv (neonate), 8.6 mSv (1 year), 6.4 mSv (5 years), 8.6 mSv (10 years) and 12.7 mSv (15 years). The maximum estimated skin dose (15 patients) did not exceed 60 mGy. With the new ICRP value for TWF(b), increases in the CFs in the order of 10-30%, and in the effective dose of 10-20%, were indicated. The results indicated that the effective dose in paediatric interventional cardiology is of much greater concern than the skin dose. Furthermore, age-dependent CF(E) values are required so as not to underestimate the doses to very young patients.
Tools for Sediment Management in Rivers
Sediment management, including supply and continual redistribution of sediments for channel maintenance and channel forming, is critical for effective environmental water programs. Many tools have been developed to more effectively manage sediment in rivers for ecosystem maintenance and improvement. This chapter reviews some of these tools, including sediment mobilization theory, environmental water requirements for geomorphic maintenance, and complementary options. Sediment mobilization theory addresses entrainment, transport, and deposition of sediment particles. Environmental flows assessment approaches that support geomorphic processes include threshold-based approaches, field/laboratory methods, and holistic methods. Complementary options for sediment management include catchment-scale conceptual models and budgets for sediment, basin land management (e.g., reforestation, better agriculture practices, etc.), sediment management through dams, and sediment augmentation below dams. These complementary options often have cobenefits with other management objectives. The chapter emphasizes that sediment management is generally complex, such that continual research is needed, ranging from improved sediment mobilization models to large-scale river experiments.