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Direct measurements of airborne particle mass concentrations or mass loads are often used to estimate health effects from the inhalation of resuspended contaminated soil. Airborne particle mass concentrations were measured using a personal sampler under a variety of surface-disturbing activities within different depositional environments at both volcanic and nonvolcanic sites near the Sunset Crater volcano in northern Arizona. Focused field investigations were performed at this analog site to improve the understanding of natural and human-induced processes at Yucca Mountain, Nevada. The level of surface-disturbing activity was found to be the most influential factor affecting the measured airborne particle concentrations, which increased over three orders of magnitude relative to ambient conditions. As the surface-disturbing activity level increased, the particle size distribution and the majority of airborne particle mass shifted from particles with aerodynamic diameters less than 10 mum (0.00039 in) to particles with aerodynamic diameters greater than 10 mum (0.00039 in). Under ambient conditions, above average wind speeds tended to increase airborne particle concentrations. In contrast, stronger winds tended to decrease airborne particle concentrations in the breathing zone during light and heavy surface-disturbing conditions. A slight increase in the average airborne particle concentration during ambient conditions was found above older nonvolcanic deposits, which tended to be finer grained than the Sunset Crater tephra deposits. An increased airborne particle concentration was realized when walking on an extremely fine-grained deposit, but the sensitivity of airborne particle concentrations to the resuspendible fraction of near-surface grain mass was not conclusive in the field setting when human activities disturbed the bulk of near-surface material. Although the limited sample size precluded detailed statistical analysis, the differences in airborne particle concentration over 900-y weathered volcanic and nonvolcanic deposits appeared to be potentially significant only under heavy surface disturbances.

After the collapse of the Soviet Union and consequently the termination of the Cold War and the disarmament agreements, many nuclear warheads are in a queue for dismantling. As a result, substantial number of nuclear submarines equipped with ballistic missiles will be also withdrawn from service. However, Russian nuclear submarines have suffered from reactivity accidents five times. In the paper, a reactivity accident on a nuclear submarine that happened at Chazhma Bay located between Vladivostok and Nakhodka on August 10, 1985, has been described. In addition, the characteristics of submarine nuclear reactors, procedures of refueling, and the possibility of a similar accident are given. Further, the radiological risk to Japan and neighboring countries has been assessed by using an atmospheric pollutant transport code, WSPEEDI, developed by Japan Atomic Energy Research Institute. The radiological risk has been evaluated for the Chazhma Bay accident and for a hypothetical reactivity accident of a retired submarine during defueling, assuming winter meteorological conditions. The analyses have shown that the radioactive material might be transported in the atmosphere to Japan in one to several days and might contaminate wide areas of Japan. Under the assumptions taken in the paper, however, the radiological dose to population in the area might be not significant.

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