Bayesian inverse modeling and source location of an unintended I-131 release in Europe in the fall of 2011

Abstract

In the fall of 2011, iodine-131 (I-131) was detected at several radionuclide monitoring stations in Central Europe.of I-131 to determine the location of the release as well as its magnitude and temporal variation. Although the location of 5 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 sourcereceptor-sensitivity (SRS) matrices for each grid cell of our study domain. We use two dispersion models, Flexpart and Hysplit, 10 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 15 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 20 and never exceeded regulatory limits.1 Atmos. Chem. Phys. Discuss.,

Atmospheric modeling and source reconstruction of radioactive ruthenium from an undeclared major release in 2017

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Potential Source Apportionment and Meteorological Conditions Involved in Airborne 131I Detections in January/February 2017 in Europe

“…23 Several significant 131 I emissions from radiopharmaceutical production units have already been reported in the literature as a result of incidents during the past decade, leading to a similar widespread detection of 131 I at trace levels (tenths to tens of μBq m −3 ) on the European scale. 8,9,14,27 In August 2008, an incident release of ca. 48 GBq of gaseous molecular 131 I occurred at the Institut national des RadioEleḿents (IRE) in Belgium.…”

“…48 GBq of gaseous molecular 131 I occurred at the Institut national des RadioEleḿents (IRE) in Belgium. 8,9 This amount was released at once and corresponded to the yearly 131 I release authorization. The incident was rated 3 on the International Nuclear and radiological Event Scale (INES).…”

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