Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-206
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
16 Mar 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Bayesian inverse modeling and source location of an unintended I-131 release in Europe in the fall of 2011
Ondřej Tichý1, Václav Šmídl1, Radek Hofman1, Kateřina Šindelářová1, Miroslav Hýža2, and Andreas Stohl3 1Institute of Information Theory and Automation, Czech Academy of Sciences, Prague, Czech Republic
2National Radiation Protection Institute, Prague, Czech Republic
3NILU: Norwegian Institute for Air Research, Kjeller, Norway
Abstract. In the fall of 2011, iodine-131 (I-131) was detected at several radionuclide monitoring stations in Central Europe. After investigation, the International Atomic Energy Agency (IAEA) was informed by Hungarian authorities that I-131 was released from the Institute of Isotopes Ltd in Budapest, Hungary. It was reported that a total activity of 342 GBq of I-131 was emitted between September 8 and November 16, 2011. In this study, we use the ambient concentration measurements of I-131 to determine the location of the release as well as its magnitude and temporal variation. Although the location of the release became eventually known, its temporal variation is still uncertain and only partial information is available. For our source reconstruction, we use no prior knowledge. Instead, we estimate the source location and emission variation using only the available I-131 measurements. Subsequently, we use the information about the source term for validation of our results. For the source determination, we first perform backward runs of atmospheric transport models and obtain source-receptor-sensitivity (SRS) matrices for each grid cell of our study domain. We use two dispersion models, Flexpart and Hysplit, driven with meteorological analysis data from the global forecast system (GFS) weather forecast model. Second, we use a recently developed inverse method, least-squares with adaptive prior covariance (LS-APC), to determine the I-131 emissions and their temporal variation from the measurements and computed SRS matrices. For each grid cell of our simulation domain, we evaluate the probability that the release was generated in that cell using Bayesian model selection. The model selection procedure also provides information about the most suitable dispersion model for the source term reconstruction. Third, we select the most probable location of the release with its associated source term and perform forward calculation to study the consequences of the iodine release. Results of these procedures are compared with the known release location and reported information about its time variation. We find that our algorithm could successfully locate the actual release site. The estimated release period is also in agreement with the values reported by IAEA, while our estimate for the total released activity (490 GBq) is higher than the reported one (342 GBq). Nevertheless, even using our larger source term, dose amounts were very low and never exceeded regulatory limits.

Citation: Tichý, O., Šmídl, V., Hofman, R., Šindelářová, K., Hýža, M., and Stohl, A.: Bayesian inverse modeling and source location of an unintended I-131 release in Europe in the fall of 2011, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-206, in review, 2017.
Ondřej Tichý et al.
Ondřej Tichý et al.
Ondřej Tichý et al.

Viewed

Total article views: 310 (including HTML, PDF, and XML)

HTML PDF XML Total Supplement BibTeX EndNote
217 66 27 310 10 12 25

Views and downloads (calculated since 16 Mar 2017)

Cumulative views and downloads (calculated since 16 Mar 2017)

Viewed (geographical distribution)

Total article views: 310 (including HTML, PDF, and XML)

Thereof 310 with geography defined and 0 with unknown origin.

Country # Views %
  • 1

Saved

Discussed

Latest update: 29 Apr 2017
Publications Copernicus
Download
Short summary
In the fall of 2011, iodine-131 (I-131) was detected at several radionuclide monitoring stations in Central Europe. We estimate the source location and emission variation using only the available I-131 measurements. Subsequently, we use the IAEA report about the source term for validation of our results. We find that our algorithm could successfully locate the actual release site. The findings are also in agreement with the values reported by IAEA.
In the fall of 2011, iodine-131 (I-131) was detected at several radionuclide monitoring stations...
Share