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| Titel |
Inverse modeling of April 2013 radioxenon detections |
| VerfasserIn |
Radek Hofman, Petra Seibert, Anne Philipp |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093343
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| Publikation (Nr.) |
 EGU/EGU2014-7975.pdf |
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| Zusammenfassung |
| Significant concentrations of radioactive xenon isotopes (radioxenon) were detected by
the International Monitoring System (IMS) for verification of the Comprehensive
Nuclear-Test-Ban Treaty (CTBT) in April 2013 in Japan. Particularly, three detections of
Xe-133 made between 2013-04-07 18:00 UTC and 2013-04-09 06:00 UTC at the station
JPX38 are quite notable with respect to the measurement history of the station. Our goal is to
analyze the data and perform inverse modeling under different assumptions. This work is
useful with respect to nuclear test monitoring as well as for the analysis of and response to
nuclear emergencies.
Two main scenarios will be pursued: (i) Source location is assumed to be known (DPRK
test site). (ii) Source location is considered unknown. We attempt to estimate the source
strength and the source strength along with its plausible location compatible with the data in
scenario (i) and (ii), respectively. We are considering also the possibility of a vertically
distributed source.
Calculations of source-receptor sensitivity (SRS) fields and the subsequent inversion are
aimed at going beyond routine calculations performed by the CTBTO. For SRS calculations,
we employ the Lagrangian particle dispersion model FLEXPART with high resolution
ECMWF meteorological data (grid cell sizes of 0.5, 0.25 and ca. 0.125 deg). This is
important in situations where receptors or sources are located in complex terrain
which is the case of the likely source of detections-the DPRK test site. SRS will be
calculated with convection enabled in FLEXPART which will also increase model
accuracy.
In the variational inversion procedure attention will be paid not only to all significant
detections and their uncertainties but also to non-detections which can have a large impact on
inversion quality. We try to develop and implement an objective algorithm for inclusion of
relevant data where samples from temporal and spatial vicinity of significant detections are
added in an iterative manner and the inversion is recalculated in each iteration. This
procedure should gradually narrow down the set of hypotheses on the source term, where the
source term is here understood as an emission in both spatial and temporal domains.
Especially in scenario (ii) we expect a strong impact of non-detections for the reduction of
possible solutions. For these and also other purposes like statistical quantification of
typical background values, measurements from all IMS noble gas stations north
of 30 deg S for a period from January to June 2013 were extracted from vDEC
platform.
We would like to acknowledge the Preparatory Commission for the CTBTO for kindly
providing limited access to the IMS data. This work contains only opinions of the authors,
which can not in any case establish legal engagement of the Provisional Technical Secretariat
of the CTBTO. This work is partially financed through the project "PREPARE: Innovative
integrated tools and platforms for radiological emergency preparedness and post-accident
response in Europe" (FP7, Grant 323287). |
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