The Challenges and Methods for Source Term Estimation of the Airborne Radiation Release from the Fukushima Dai-ichi Nuclear Power Plant

On 11th of March 2011, a magnitude 9.0 earthquake off the east coast of Japan and subsequent tsunami caused widespread damage in north-eastern Japan and resulted in a cooling system failure, partial reactor core meltdown, and radiation release from the Fukushima Dai-ichi nuclear power plant (FD-NPP). An accurate estimate of the radiation released into the atmosphere from the FD-NPP plant is necessary for scientists and government officials to make informed decisions that impact the estimation of long-term doses and the safety of people living and working near Fukushima. There are currently several research grade solutions for making a source term estimates (STE) for atmospheric contaminant release, however they have rarely been applied to an operational radiological incident. The FD-NPP radiation release and contamination estimation problem poses unique challenges in the physics, available measurements, and STE methodology used. To address these ongoing challenges, the National Science Foundation (NSF) recently sponsored a workshop held at the National Center for Atmospheric Research (NCAR) that brought together an international group of researchers from Japan, Europe, and the United Sates with relevant expertise. The goal of the workshop was to: 1.) share/present current STE approaches, 2.) share/present available data, 3.) discuss how the current state-of-the-science STE methods can be extended to address the challenging unanswered questions related to the FD-NPP incident, and 4.) document these results in a peer-reviewed journal to inform the broader scientific community should a similar event occur again. This presentation will cover the findings that were derived from this workshop with a focus placed on the unique challenges to STE that are present in the FD-NPP problem and a survey of the methods that can be used to address these challenges.