Preliminary safety assessment for planning near surface disposal of low-level radioactive waste in Greece.

This paper presents the approach, assumptions, and computational analysis of the preliminary safety assessment, regarding the post-closure period for the disposal of radioactive waste in Greece. The assessment was implemented in the context of the National Program for the disposal of radioactive waste in the country, which is currently in the early stage for the investigation of facility siting. The basis scenario selected for this investigation was the leaching of radionuclides and the exposure in a residence offsite. Moreover, a scenario involving the intrusion in the facility and construction of a dwelling that disturbs the disposal zone is also considered. Due to the significant uncertainties in the current phase, the simulations related to leaching of the waste both in the offsite and intrusion scenarios are based on an uncertainty analysis with 25 site and scenario related parameters. The most important contribution is attributed to Ra-226 with an annual dose equal to about 2 and 3 µSv per MBq disposed, for the offsite and intrusion scenario, respectively. Th-232, Cl-36, C-14, Ag-108m and Pu-239 follow with a dose one order of magnitude less, compared to Ra-226. In the leaching scenarios examined, and for the most dose relevant radionuclides, the exposure related to drinking water from the well and the use of this water to irrigate fruits and vegetables are by far the dominant pathways due to the environmental transfer of the radionuclides and their associated dose coefficients. Th-232 dominates the direct exposure pathways (direct external radiation and plant contamination from the contaminated surface soil) in the intrusion scenario with an annual dose of about 1.4 mSv per Bq/g disposed. Ra-226, Cl-36 and Ag-108m cause exposure levels higher than 0.2 mSv/y per Bq/g disposed in the facility. A wide range was considered for the uncertainty parameters that led to a significant variation in the predicted doses that is expected to envelope the potential exposure for each radionuclide.

Novel determination of the total phenolic content in crude plant extracts by the use of 1H NMR of the -OH spectral region.

A novel method for the determination of the total phenolic content using (1)H NMR spectroscopy in the -OH spectral region is presented. The use of DMSO-d(6), which is an aprotic and strongly hydrogen bonding solvent, allows the "appearance" of the relative sharp resonances of phenolic hydroxyl protons in the region of 8-14 ppm. The determination of the total phenolic -OH content requires three steps: (i) a 1D (1)H NMR spectrum is obtained in DMSO-d(6); (ii) a subsequent 1D (1)H NMR spectrum is recorded with irradiation of the residual water signal which results in the elimination or reduction of the phenolic -OH groups, due to proton exchange; and (iii) 1D (1)H NMR spectra are recorded with the addition of a progressively increased amount of salt, NaHCO(3), which results in extensive linebroadening of the COOH resonances thus allowing the discrimination of the phenolic from the carboxylic acid signals. Integration, with respect to the internal standard TSP-d(4), of the signal resonances between 14 and 8 ppm in spectrum (i) which are either eliminated or reduced in intensity in steps (ii) and (iii) allows the quantitation of the total phenolic content. The method was applied to model compounds, a mixture of them and several extracts of natural products. The results of the proposed (1)H NMR method were compared to the Folin-Ciocalteu (FC) reagent method. Additionally, since (1)H NMR refers to the total phenolic hydroxyl protons, a reaction factor, A(e), is proposed that corresponds to the hydroxyl reactivity. The (1)H NMR method is rapid and accurate bearing the inherent advantages of the NMR spectroscopy and can be applied directly in complex extracts. Furthermore, it can be applied in a wide range of matrixes from crude plant extracts and food products to biological samples.

Indications of in vivo transfer of an epidemic R plasmid from Salmonella enteritidis to Escherichia coli of the normal human gut flora.

The presence of conjugative R plasmids as well as the possible similarities among them were studied in nine ampicillin-resistant Salmonella enteritidis isolates and nine ampicillin-resistant Escherichia coli isolates from the normal fecal flora that were simultaneously isolated from nine epidemiologically unrelated outpatients. It was found that in eight patients, ampicillin resistance in S. enteritidis was encoded by ca. 34-MDa transferable plasmids very similar to those found in a recent study of the epidemiology of ampicillin-resistant S. enteritidis in Greece (A.C. Vatopoulos, E. Mainas, E. Balis, E.J. Threlfall, M. Kanelopoulou, V. Kalapothaki, H. Malamou-Lada, and N.J. Legakis, J. Clin. Microbiol. 32:1322-1325, 1994). Moreover, transferable R plasmids with the same molecular size and restriction pattern were found in the normal flora E. coli of two of these patients. This finding, if confirmed by further studies, is consistent with the hypothesis that normal flora E. coli could act as a reservoir of resistant genes and, consequently, as a factor in the dissemination of these genes among pathogens of human and animal origin such as Salmonella spp. and needs to be examined further.