Determination of ultra-low 236U in environment samples using ICP-MS/MS measurement and chemical separation

Presence of 236U,237Np and 239,240Pu in shells from the coast of the south of China

This study reports first results on uranium (236U), neptunium (237Np) and plutonium (239Pu and 240Pu) isotopes in shell samples (i.e. oyster, clam and scallop shells) from the coast of the South of China. The 240Pu/239Pu and 236U/238U atom ratios are used for source identification, and the 237Np/239Pu, 237Np/236U and 236U/239Pu non-isotopic atom ratios to study the relative bioaccumulation of Np, Pu and U during the shell formation. The obtained concentration levels are in the 104-106 atoms g-1 range in every case. Clear regional differences are observed in the case of the 240Pu/239Pu atom ratio, with average values lower along the coast of East China Sea (average 0.227 ± 0.120, n = 5) compared to the South China Sea (average 0.258 ± 0.018, n = 7), showing a possible influence of the Pu released at the Pacific Proving Ground nuclear test site. 236U/238U ( × 10-8) atom ratios range from 0.046 ± 0.009 to 0.524 ± 0.135, in agreement with the expected levels in surface seawater from the China Sea. 237Np/239Pu (average 4.1 ± 2.6, n = 13) and 237Np/236U ratios (average 14 ± 10, n = 13) in the oyster shells are clearly enhanced compared to the estimated one in the surface seawater, pointing out higher bioaccumulation of Np compared to Pu and U.

Deciphering sources of U contamination using isotope ratio signatures in the Loire River sediments: Exploring the relevance of 233U/236U and stable Pb isotope ratios

A broad range of contaminants has been recorded in sediments of the Loire River over the last century. Among a variety of anthropogenic activities of this nuclearized watershed, extraction of uranium and associated activities during more than 50 years as well as operation of several nuclear power plants led to industrial discharges, which could persist for decades in sedimentary archives of the Loire River. Highlighting and identifying the origin of radionuclides that transited during the last decades and were recorded in the sediments is challenging due to i) the low concentrations which are often close or below the detection limits of routine environmental surveys and ii) the mixing of different sources. The determination of the sources of anthropogenic radioactivity was performed using multi-isotopic fingerprints (²³⁶U/²³⁸U, ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb) and the newly developed ²³³U/²³⁶U tracer. For the first time ²³³U/²³⁶U data in a well-dated river sediment core in the French river Loire are reported here. Results highlight potential sources of contamination among which a clear signature of anthropogenic inputs related to two accidents of a former NUGG NPP that occurred in 1969 and 1980. The ²³³U and ²³⁶U isotopes were measured by recent high performance analytical methods due to their ultra-trace levels in the samples and show a negligible radiological impact on health and on the environment. The determination of mining activities by the use of stable Pb isotopes is still challenging probably owing to the limited dissemination of the Pb-bearing material marked by the U-ore signature downstream to the former U mines.

A review of anthropogenic radionuclide 236U: Environmental application and analytical advances

²³⁶U is an anthropogenic radionuclide that is produced from nuclear reactions of ²³⁵U(n, γ) and ²³⁸U(n, 3n). It has gained extensive attention in the field of environment, geology, nuclear emergency, and nuclear forensics. Due to the unique physical and chemical character and the distinct fingerprint character from different sources, ²³⁶U has been successfully applied in the environmental tracer, nuclear material source appointment, and environmental assessment. Until now, few reviews were published about the database, application, and the latest analytical technology development of ²³⁶U. In this review, the ²³⁶U concentration and ²³⁶U/²³⁸U isotope ratio were summarized, and the data were classified into four categories, including soil and seawater samples affected by global fallout and nuclear incidents. Furthermore, the development of environmental application and pretreatment methods were also summarized. The advanced pretreatment technology using alkali fusion and flow injection was especially discussed to introduce the development of a rapid analytical method. Finally, the research challenge and direction of ²³⁶U were proposed for further research, such as the tracer application combining ²³⁶U with other radionuclides in the terrestrial environment and the precise analysis of minor isotopes in ultra-trace uranium samples. We hope this review will help scholars to have a deep research on the analysis and application of ²³⁶U.