Radiation doses around the Fukushima Dai-Ichi Nuclear Power Plant: measurements and novel methods of analysis
Date
2018
Authors
Seel, Peter James, author
Sudowe, Ralf, advisor
Brandl, Alexander, committee member
Miller, Charles W., committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The nuclear accident which occurred at the Fukushima Dai-Ichi Nuclear Power Plant in March of 2011 released an estimated 940 petabecquerels (PBq) of I-131 equivalent radioactive emissions, of which over 32 PBq were the longer-lived isotopes Cesium-134 and Cesium-137 (Half-lives: 2.06 years, and 30.01 years). Accurate means and methods of tracking the dose rates resulting from the deposition of these two isotopes are critical to understanding when former residents can move back into the area and the remaining potential health risks. Remote sensing stations, vehicle surveys, and airborne surveys were all analyzed and compared for their efficacy and utility in dose rate tracking. Remote stations were found to be useful for long-term temporal trends, but lack validity in generalizing beyond the immediate area of each site. Analysis of data provided by these stations showed a statistically significant drop in dose rate below that expected from radioactive decay alone. This implies that radioisotopes are moving out of the vicinity of stations, likely through environmental means. Vehicle surveys provide a middle ground of spatial resolution and frequency of data collection, and dose correction factor of 1.31 from car dose rate to ambient dose equivalent rate was modeled based on conducted vehicle surveys for field use by non-experts. Utilizing GIS analytical techniques, elevation and slope were found to be statistically influential factors in dose rate changes. Importantly, different types of environments were stratified and compared to show the relative loss of radiation within them, confirming that most forests retain radioisotopes more than the median level for the region, while urban area and bare land dose rates decrease more quickly. The GIS methods tested will be useful in analyzing further surveys results and could be used to plan future research and compare to other measurement types.