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

The undeclared release and subsequent detection of ruthenium-106 (106Ru) across Europe from late September to early October of 2017 prompted an international effort to ascertain the circumstances of the event. While dispersion modeling, corroborated by ground deposition measurements, has narrowed possible locations of origin, there has been a lack of direct empirical evidence to address the nature of the release. This is due to the absence of radiological and chemical signatures in the sample matrices, considering that such signatures encode the history and circumstances of the radioactive contaminant. In limiting cases such as this, we herein introduce the use of selected chemical transformations to elucidate the chemical nature of a radioactive contaminant as part of a nuclear forensic investigation. Using established ruthenium polypyridyl chemistry, we have shown that a small percentage (1.2 ± 0.4%) of the radioactive 106Ru contaminant exists in a polychlorinated Ru(III) form, partly or entirely as ß-106RuCl3, while 20% is both insoluble and chemically inert, consistent with the occurrence of RuO2, the thermodynamic endpoint of the volatile RuO4 Together, these findings present a clear signature for nuclear fuel reprocessing activity, specifically the reductive trapping of the volatile and highly reactive RuO4, as the origin of the release. Considering that the previously established 103Ru:106Ru ratio indicates that the spent fuel was unusually young with respect to typical reprocessing protocol, it is likely that this exothermic trapping process proved to be a tipping point for an already turbulent mixture, leading to an abrupt and uncontrolled release.

Spanning pairs of Rh2(acetate)4 units with Ru(II) complexes.

A synthetic route to linear pairs of Rh2 "paddlewheel" dimers bridged by Ru(II) complexes is presented. A bis(4'-(4-carboxyphenyl)-terpyridine)Ru(II) complex spans two Rh2 dimers and displays a 26 A separation between the dimers. Increased electronic interaction is found for the dimer of dimers without the phenyl groups using bis(4'-(4-carboxy)-terpyridine)Ru(II) as the bridging complex.

A REVIEW OF NATURAL RADIONUCLIDES IN CANADIAN DRINKING WATER (1975-16).

Historical results of natural radioactivity in drinking water were reviewed for a total of 21 communities across Canada from 1975 to 2016. Analyses for 226Ra, 210Pb and total uranium were carried out on monthly composite samples of drinking water from selected Canadian municipalities. Generally speaking, levels of 226Ra, 210Pb and total uranium were found to be low compared to national and international standards for drinking water quality. Because levels were low, federal monitoring programs were discontinued in most communities in 1986 except for Regina, Elliot Lake and Port Hope. The population-weighted average levels for these three communities, using data from the most recent 5 years, are <1 mBq/L for 226Ra, <5 mBq/L for 210Pb and <0.4 µg/L for total uranium. The average effective dose resulting from drinking water intake at these levels would be <4.3 µSv per year.

Heteroleptic ruthenium(ii) chromophores based on tunable polytopic 4'-(benzamidinato)-2,2':6',2''-terpyridines.

A modulable and simple approach towards heteroleptic ruthenium(ii) complexes of amidine-based polypyridine ligands is presented. New complexes 1 and 2 ([(terpyridine)Ru(terpyridine-C6H4-C(NR)(NHR))]2+ with R = propyl and R = phenyl derivatives, respectively) were characterized by NMR spectroscopy in solution and by X-ray diffraction, which confirmed the obtention of the (E) stereoisomer alone. Depending on the bulkiness of the R-substituents introduced on the amidine moiety, rotational isomerism around the C-N bond could be observed at r.t. Spectroscopic and electrochemical studies showed that the nature of the R-substituents introduced on the amidine moiety can significantly influence the redox and ground-state acido-basic properties of the complexes, while maintaining their electronic features. This particular tunability of polytopic 4'-(amidinato)-terpyridines offers an interesting perspective for photoactive units in larger multi-functional arrays.

The determination of Fukushima-derived cesium-134 and cesium-137 in Japanese green tea samples and their distribution subsequent to simulated beverage preparation.

Health Canada's Radiation Protection Bureau has identified trace quantities of (134)Cs and (137)Cs in commercially available green tea products of Japanese origin. Referenced to March 11, 2011, the activity ratio ((134)Cs/(137)Cs) has been determined to be 1:1, which supports an origin from the Fukushima Dai-ichi Nuclear Power Plant accident. The upper limits of typical tea beverage preparation conditions were applied to the most contaminated of these green tea samples to determine the proportion of radiocesium contamination that would be available for human consumption. The distribution of radiocesium among the components of the extraction experiments (water, residual tea solid, and filter media) was determined by both conventional and Compton-suppressed gamma spectroscopy. The latter aided tremendously in providing a more complete radiocesium distribution profile, particularly for the shorter-lived (134)Cs. Cesium extraction efficiencies of 64 ± 7% and 64 ± 5% were determined based on (134)Cs and (137)Cs, respectively. Annual, effective dose estimates from ingestion of (137)Cs and (134)Cs (1.8-3.7 µSv), arising from the consumption of tea beverages prepared from the most contaminated of these samples, are insignificant relative to both total (∼ 2.4 mSv) and ingested (∼ 0.28 mSv) annual effective doses received from naturally occurring radioactive sources. As such, there is no health concern arising from the consumption of green tea beverages contaminated with radiocesium at the levels encountered in this study.

A report on radioactivity measurements of fish samples from the west coast of Canada.

Even though many studies have shown that radioactive caesium levels in fish caught outside of Japan were below experimental detection limits of a few Bq kg(-1), significant public concern has been expressed about the safety of consuming seafood from the Pacific Ocean following the Fukushima-Daiichi nuclear accident. To address the public concerns, samples of commonly consumed salmon and groundfish harvested from the Canadian west coast in 2013 were analysed for radioactive caesium. None of the fish samples analysed in this study contained any detectable levels of (134)Cs and (137)Cs under given experimental setting with the average detection limit of ∼2 Bq kg(-1). Using a conservative worst-case scenario where all fish samples would contain (137)Cs exactly at the detection limit level and (134)Cs at half of the detection limit level (to account for much shorter half-life of (134)Cs), the resulting radiation dose for people from consumption of this fish would be a very small fraction of the annual dose from exposure to natural background radiation in Canada. Therefore, fish, such as salmon and groundfish, from the Canadian west coast are of no radiological health concern.

Cytotoxicity of a series of water-soluble mixed valent diruthenium tetracarboxylates.

BACKGROUND: Mixed-valent diruthenium tetracarboxylate complexes were shown to have slight antineoplastic activity against P388 leukemia cell lines. However these complexes suffered from poor water-solubility, which may have detrimentally affected their activity. MATERIALS AND METHODS: Mixed-valent diruthenium tetracarboxylates of the type [Ru2(O2CR)4(L)2] (PF6) with L = imidazole, 1-methylimidazole and H2O when R = CH3, L = ethanol when R = Fc (ferrocenyl) or Fc-CH=CH- and of the type M3[Ru2(O2CR)4(H2O)2]4H2O, M = Na+ when R = m-C6H4SO3- and M = K+ when R = p-C6H4SO3-, were tested for cytotoxicity against HeLa and multidrug resistant CoLo 320DM human cancer cell lines. Cell survival was measured by means of the colorometric 3-(4,5dimethylthiazol-2-yl)-diphenyltetrazodium bromide assay. RESULTS: The mean drug concentration from 3 experiments causing 50% cell killing, ie, IC50 values, varied between 120 and 950 micromol dm(-3). CONCLUSION: The antineoplastic activity of the highly water-soluble m-sulpho derivative was the highest, while the poorly water-soluble imidazole derivatives did not exhibit any cytotoxic properties. The CoLo 320DM cancer cells were 5 times more prone to drug-induced cell death than the HeLa cells.

A divergent strategy for covalently-tethered (tpy)2Ru(II) systems based on Rh2(N,N'-diphenylbenzamidinates)4.

A tetra Ru(II) bis(terpyridine) complex has been synthesized from Rh2(N,N'-diphenyl-4-bromobenzamidinate)4 in excellent yield using a modified Buchwald-Hartwig C-N bond forming protocol followed by efficient amide bond formation.

Luminescent polynuclear assemblies.

This tutorial review consists of five main sections. The first gives a general introduction and then a discussion about the need for luminescent assemblies. The next four sections present the various assemblies based on the metal ions used to assemble the final structures. Each of these sections gives a brief overview of the design principles, synthesis, and ground and excited-state properties of the ligands and complexes in question. The review concludes with some suggestions for future avenues of research.

Self-assembled light-harvesting systems: Ru(II) complexes assembled about Rh-Rh cores.

Ru(II) polypyridine species have been assembled about dirhodium(II, II) tetracarboxylate cores. The complexes prepared have general formulas [{(terpy)Ru(La)}n{Rh2(CH3COO)4-n(CH3CN)2}]2n+ (a-type compounds: terpy = 2,2':6',2' '-terpyridine; La = 4'-(p-carboxyphenyl)-2,2':6',2' '-terpyridine; n = 1, 1a; n = 2, cis-2a and trans-2a-cis and trans refer to the arrangement of the Ru(II) species around the dirhodium core; n = 3, 3a), [{(Lb)Ru(La)}n{Rh2(CH3COO)4-n(CH3CN)2}]2n+ (b-type compounds: Lb = 6-phenyl-2,4-di(2-pyridyl)-s-triazine; n = 1, 1b; n = 2, an inseparable mixture of cis-2b and trans-2b; n = 3, 3b; n = 4, 4b), and [{(terpy)Ru(Lc)}{Rh2(CH3COO)3(CH3CN)2}]2+ (1c; Lc = 6-(p-carboxyphenyl)-2,4-di(2-pyridyl)-s-triazine). As model species, also the mononuclear [(terpy)Ru(La)]2+ (5a), [(La)Ru(Lb)]2+ (5b), and [(terpy)Ru(Lc)]2+ (5c) have been prepared. All of the complexes have been characterized by several techniques, including NMR and mass spectra, and the stability of the various species is discussed. The absorption spectra of all of the compounds are dominated by the Ru(II) polypyridine moieties, showing intense ligand-centered (LC) bands in the UV region and intense metal-to-ligand charge-transfer (MLCT) bands in the visible. The compounds exhibit several metal-centered oxidation and ligand-centered reduction processes, which have been assigned to specific subunits. Both absorption and redox data indicate a supramolecular nature of the assembled systems. Efficient energy transfer from the MLCT triplet state of the Ru-based components to the lowest-energy excited state of the dirhodium core takes place for the a-type compounds at 298 K in acetonitrile solution, whereas such a process is inefficient for the b-type and c-type species, which exhibit the typical MLCT emission. At 77 K in butyronitrile matrix, Ru-to-Rh2 energy transfer is partly efficient for both the a-type and the b-type compounds and is inefficient for 1c. The reasons for such behavior are discussed by taking into account arguments concerning the driving force and reorganization energy of the complexes.