The session gathers geoscientific aspects and results on the dynamics and processes related to radioactive materials released from nuclear accidents, particularly the Fukushima and Chernobyl nuclear power accidents, covering global transport of radioactive material over atmosphere, ground and water system, and its reaction with the soil-bio system. The session consists of updated observations, new theoretical developments including simulations, methods or tools which could improve our predictive capabilities during eventual future nuclear emergencies. The session also includes evaluations of existing tools at the example of past nuclear accidents and/or other data sets (e.g., tracer experiments).

Radioactive contamination due to massive accidental release of nuclear material from the Fukushima and Chernobyl accidents has a large geophysical impact and hence is a multi-disciplinary geoscience problem involving inter-alia, (i) Atmospheric Science (emissions, transport, pollution, ions); (ii) Hydrology (surface water, ground water, soil-water interaction); (iii) Oceanology; (iv) Soil System; (v) Forestry; (vi) Natural Hazard (warning system, risk assessments including geophysical variability); (vii) Measurement Technique (e.g., analyses of multipoint data); and Ecosystem (natural removal/migration of radionuclides). Not only as the polluting materials that are hazardous to human society, the radioactive materials are also an ideal marker in understanding dynamics in the environment.

By combining >30 year (halftime of Cesium 137) monitoring data of the Chernobyl Accident in 1986 and >5 year dense measurement network data by the most advanced instrumentation for the Fukushima Accident, our knowledgebase on both the behavior of radioactive materials and its environmental contamination have significantly improved. These knowledges should also be used in developing improved monitoring systems including emergency time, acute sampling/measurement schemes, and remediation schemes for a future accident.