Methods For Estimating The Atmospheric Radiation Release From The Fukushima Dai-Ichi Nuclear Power Plant

Abstract

WHat: A multidisciplinary group of scientists and engineers from academia/private industry/ government/national laboratories in the United States, Japan, and Europe convened to discuss the Fukushima Dai-ichi nuclear power plant incident, observations of the radiation deposition patterns, and methods to use these measurements to better estimate the total radioactive material released into the atmosphere. WHEn: 22–23 February 2012 WHErE: National Center for Atmospheric Research, Boulder, Colorado O n 11 March 2011, a 9.0-magnitude earthquake off the east coast of Japan and subsequent tsunami caused widespread damage in northeastern 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). Following the devastating earthquake and tsunami that severely damaged the nuclear power plant in Fukushima, Japan, an unknown quantity of radioactive material was released into the air and water surrounding the crippled nuclear power plant. Assessments of the remaining nuclear fuel following the incident have allowed the scientific community to approach a consensus on the total amount of radioactive material released from the FD-NPP. What is still unclear, however, is the timing of the releases and how much of the radioactive material was released into the atmosphere versus directly into the nearby ocean. The complexity of this disaster—which included disabled observation systems; multiple intermittent explosive releases of radioactive materials combined with a long-duration continuous release of radiation at an unknown rate; and changes in boundary layer depth, wind speed/direction, and precipitation in the region surrounding the FD-NPP—complicates these estimates. An accurate estimate of the radiation released into the atmosphere from the FD-NPP 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. While extensive observational surveys of the radiation fallout pattern have been made, using these measurements to estimate the magnitude and timing of radiation released into the atmosphere versus the ocean remains a challenging undertaking. Despite the large number of observations available, they cover only a small fraction of the area and time period. Consequently, current estimates include a large degree of uncertainty, resulting in correspondingly large uncertainties regarding the total amount of radiation fallout and associated environmental impacts, which significantly hamper the Japanese