Chemical and radioanalytical investigations of 106Ru-containing air filters from Vienna in fall 2017: searching for stable element anomalies

Abstract

Related to the recent nuclear release of radioactive ruthenium isotopes in fall 2017, we analyzed air filters from Vienna for irregularities in the (stable) elemental composition of particulate matter from this period. Methods were SEM/EDXS and INAA. For comparison, a reference filter from 2007 and blank filters were used. The chemical fingerprint encompassed 28 elements. The results show no indication for a considerable change in the elemental composition of the suspended matter. For example, no anomalies in the abundance of platinum group elements were found. The results suggest that the release of 106Ru had not been accompanied by a release of detectable amounts of (activatable) stable elements.

Airborne concentrations and chemical considerations of radioactive ruthenium from an undeclared major nuclear release in 2017

“…Thus, we conclude that the release most likely involved RuO 4 , which either was released directly or possibly underwent chemical processing for its stabilization (e.g., trapping in NaOH or HCl) before its release into the environment. The fact that no apparent stable element anomalies were found in addition to the release supports the assumption that the release was limited to the isotopes of Ru (16).…”

“…Instead, the origin of 103,106 Ru is rather associated with nuclear fuel reprocessing or with (medical or technical) radioactive sources. In addition, no unusual (stable) element contamination was found on a 106 Ru-containing filter from Vienna (Austria) (16).…”

Non-natural ruthenium isotope ratios of the undeclared 2017 atmospheric release consistent with civilian nuclear activities

“…However, alongside the radioisotopes, almost any nuclear release also contains stable isotopes of the same element, but with anomalous, non-natural abundances that reflect production by nuclear fission and capture reactions. We investigated the stable isotopic compositions of a few nanograms of airborne Ru collected by a series of air filters from Vienna, Austria, including one sample that incorporated radioactive Ru from the atmospheric release in 2017 24 using multicollector inductively coupled plasma mass spectrometry (see Methods). Four other filters from air collections between 2015 and 2018 (Supplementary Table 1) are used to characterize the typical background Ru isotopic composition of particulate matter sampled at that specific air filter station ( Fig.…”

“…While it would have been possible to meet the specifications of the 144 Ce source by using spent fuel with low burnup 2 , the Ru stable isotope signature confirms that spent fuel at the end of its lifetime was reprocessed [32][33][34] . In this case, the cooling time of the nuclear fuel must have been decreased to ≤2 years to achieve the required high specific activity of 144 Ce in the compact CeO 2 source 18,33 24 . Air sampling is performed at this station with an air collection time of usually 1 day or up to 1 week.…”

Identification of a chemical fingerprint linking the undeclared 2017 release of 106 Ru to advanced nuclear fuel reprocessing

“…From a radiological perspective, there is none. Samples have been shown to be radiopure and to carry the stable ruthenium isotopic signature of civilian spent nuclear fuel (10), while stable elemental analysis by scanning electron microscopy and neutron activation has revealed no detectable anomalies compared to aerosol filter media sampled prior to the advent of the 106 Ru contaminant (1,11). We are, then, left with the definition of a limiting case for a nuclear forensic investigation.…”