Levels of radionuclide concentrations in benthic invertebrate species from the Balearic Islands, Western Mediterranean, during 2012-2018.

Baseline levels of radionuclides in the marine environment of the Balearic Islands in Western Mediterranean have not been reported in literature. Because of their ecological role and acknowledged sensitivity to pollutants, herein, the activity concentrations of 210Po, 40K, 210Pb, 90Sr, and 234Th were measured in two types of benthic invertebrate species (mussels and sea urchins) sampled during 2012-2018. The activity concentrations of 210Po, 40K, 210Pb, and 234Th ranged from 38 ±â€¯1 to 325 ±â€¯11 Bq kg-1 dry weight (d.w.), 220 ±â€¯10 to 996 ±â€¯46 Bq kg-1 d.w., ND (lower than the limit of detection) to 55 ±â€¯8 Bq kg-1 d.w., and ND to 70 ±â€¯15 Bq kg-1 d.w., respectively. In all cases, no artificial 90Sr activity was detected in the collected samples. The committed effective dose to humans was calculated to be in the range of 48-640 µSv year-1.

Geographical origin of bivalve molluscs in coastal areas using natural radioactivity fingerprinting and multivariate statistical analyses: Andalusian coast as case of study.

The presence of natural and artificial radionuclides in the marine environment produces the accumulation of radionuclides in bivalve molluscs consumed by humans, and therefore it could result in a radiological hazard. In this study, the activity concentrations of 210Po, 40K, 210Pb and 234Th were determined in different types of bivalve molluscs sampled during the period of May 2014-June 2015, along coastal areas from the Andalusian region (South of Spain), through alpha-particle spectrometry and low-level gamma-ray spectrometry. The activity concentrations of 210Po; 40K; 210Pb and 234Th varied between 40 ± 2 and 515 ± 9 Bq kg-1 dry weight (d.w.); 121 ± 7 and 674 ± 34 Bq kg-1 d.w.; ND (lower than limit of detection) and 73 ± 10 Bq kg-1 d.w.; and ND and 126 ± 27 Bq kg-1 d.w., respectively. The committed effective dose to humans was calculated to range from 41 to 479 µSv year-1. Both activity concentrations and dose levels were comparable to previous studies from other countries. Finally, a multivariate statistical analysis of natural radioactivity content allowed the discrimination between bivalve molluscs from Atlantic and Mediterranean coasts.

Baseline activity concentration of 210Po and 210Pb and dose assessment in bivalve molluscs at the Andalusian coast.

In this study, the activity concentrations of 210Po and 210Pb were determined in different types of bivalve molluscs sampled during the period of May 2014-June 2015 along the Andalusian littoral. Radioactivity concentrations of 210Po were determined through alpha-particle spectrometry using 209Po as an internal tracer. Radioactivity concentrations of 210Pb were determined through low-level gamma-ray spectrometry. The activity concentrations of 210Po and 210Pb varied between 40 ±â€¯2 and 515 ±â€¯9 Bq kg-1 dry weight (d.w.), and ND (lower than limit of detection) and 73 ±â€¯10 Bq kg-1 d.w., respectively. The committed effective dose to humans was calculated to range from 39 to 477 µSv year-1. Radioactivity and dose levels were compared with previous studies from other countries.

Comparison of solvent extraction and extraction chromatography resin techniques for uranium isotopic characterization in high-level radioactive waste and barrier materials.

The development of Deep Geological Repositories (DGP) to the storage of high-level radioactive waste (HLRW) is mainly focused in systems of multiple barriers based on the use of clays, and particularly bentonites, as natural and engineered barriers in nuclear waste isolation due to their remarkable properties. Due to the fact that uranium is the major component of HLRW, it is required to go in depth in the analysis of the chemistry of the reaction of this element within bentonites. The determination of uranium under the conditions of HLRW, including the analysis of silicate matrices before and after the uranium-bentonite reaction, was investigated. The performances of a state-of-the-art and widespread radiochemical method based on chromatographic UTEVA resins, and a well-known and traditional method based on solvent extraction with tri-n-butyl phosphate (TBP), for the analysis of uranium and thorium isotopes in solid matrices with high concentrations of uranium were analysed in detail. In the development of this comparison, both radiochemical approaches have an overall excellent performance in order to analyse uranium concentration in HLRW samples. However, due to the high uranium concentration in the samples, the chromatographic resin is not able to avoid completely the uranium contamination in the thorium fraction.

Isolation of 236U and 239,240Pu from seawater samples and its determination by Accelerator Mass Spectrometry.

In this work we present and evaluate a radiochemical procedure optimised for the analysis of 236U and 239,240Pu in seawater samples by Accelerator Mass Spectrometry (AMS). The method is based on Fe(OH)3 co-precipitation of actinides and uses TEVA® and UTEVA® extraction chromatography resins in a simplified way for the final U and Pu purification. In order to improve the performance of the method, the radiochemical yields are analysed in 1 to 10L seawater volumes using alpha spectrometry (AS) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Robust 80% plutonium recoveries are obtained; however, it is found that Fe(III) concentration in the precipitation solution and sample volume are the two critical and correlated parameters influencing the initial uranium extraction through Fe(OH)3 co-precipitation. Therefore, we propose an expression that optimises the sample volume and Fe(III) amounts according to both the 236U and 239,240Pu concentrations in the samples and the performance parameters of the AMS facility. The method is validated for the current setup of the 1MV AMS system (CNA, Sevilla, Spain), where He gas is used as a stripper, by analysing a set of intercomparison seawater samples, together with the Laboratory of Ion Beam Physics (ETH, Zürich, Switzerland).