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Watanabe, Norio
Nihon Genshiryoku Gakkai Wabun Rombunshi, 3(4), p.396 - 406, 2004/12
The U. S. Nuclear Regulatory Commission has been carrying out the Accident Sequence Precursor (ASP) Program to identify and categorize precursors to potential severe core damage accident sequences using the PSA technique. The ASP Program has identified a lot of risk significant events as precursors that occurred at U. S. nuclear power plants. The results from the ASP Program include valuable information that could be useful for obtaining risk significant insights and for monitoring risk trends in nuclear power industry. The present study examines and discusses quantitative risk trends for the industry level, using two indicators, that is, the occurrence frequency of precursors and the annual core damage probability, deriving from the ASP analysis results. It is shown that the core damage risk at U.S. nuclear power plants has been lowered and the likelihood of risk significant events has been remarkably decreasing. Also, the present study demonstrates that two risk indicators used here can provide quantitative information useful for monitoring risk trends in nuclear power industry.
Nomura, Yasushi; R.Leicht*; P.Ashton*
Journal of Nuclear Science and Technology, 31(8), p.850 - 860, 1994/08
Times Cited Count：4 Percentile：53.92(Nuclear Science & Technology)no abstracts in English
Hada, Kazuhiko; Fujimoto, Nozomu; Sudo, Yukio; Wada, Hozumi*
Proc. of the 1st JSME/ASME Joint Int. Conf. on Nuclear Engineering,Vol. 2, p.291 - 298, 1991/00
no abstracts in English
Battulga, B.; Atarashi-Andoh, Mariko; Koarashi, Jun
no journal, ,
Plastic debris has been recognized as an emerging contaminant in the global ecosystem. Although microplastics (MPs) have received special attention from the scientific community owing to their widespread distribution, application of highly sensitive techniques to evaluate the characteristics of MPs is still under consideration. In this study, we demonstrate multiple analytical approaches including microscopic, spectroscopic, and isotopic analyses to track MP characterization obtained from coastal river environment. We selected two sampling sites from coastal areas in Japan and collected visible plastic samples. At the same time, surface water and coastal sand samples were collected to evaluate the seasonal variations in MP occurrence and composition. Seasonal differences in occurrence and morphotypes of MPs were detected in both sampling sites, suggesting variations in geographical patterns and consumption of plastic materials in the studied region. We also found differences in carbon isotopic composition between the MPs composed of the same polymer (i.e., polyethylene and polypropylene) but with different colors. Preliminary results of 
Cs activity concentrations revealed that plastics serve as carriers for radionuclides mediated by biofilms in the coastal river environment. Furthermore, occurrences and differences in the composition of the MPs in the study areas indicate that point and nonpoint sources of MPs strongly affect their concentration in the aquatic environment.
