Anthropogenic 236U in the North Sea - A Closer Look into a Source Region.

In this study we present new seawater data of 236U and 238U sampled in the North Sea in 2010. The North Sea has been and is still receiving a considerable input of anthropogenic radionuclides from nuclear reprocessing facilities located in La Hague (France) and Sellafield (Great Britain). It therefore represents an important source region for oceanographic tracer studies using the transient signal of anthropogenic 236U. A proper knowledge of the sources of 236U is an essential prerequisite for such tracer studies. The 236U data set presented in this study covers the transition regions of the North Sea to the Atlantic Ocean, to the Baltic Sea, and upstream the Elbe River. It is discussed in the context of available 236U data from the literature. Our results show that both 236U concentrations and 236U/238U ratios in surface waters of the North Sea can be explained by simple binary mixing models implying that 236U behaves conservatively in seawater. We further show that the input of 236U by the Elbe River is negligible, while there might be a maximum input of 12 g/yr via the Baltic Sea. The results of the mixing models suggest that this still unidentified 236U contamination could be supplied by fresh water input.

Sequential injection approach for simultaneous determination of ultratrace plutonium and neptunium in urine with accelerator mass spectrometry.

An analytical method was developed for simultaneous determination of ultratrace level plutonium (Pu) and neptunium (Np) using iron hydroxide coprecipitation in combination with automated sequential injection extraction chromatography separation and accelerator mass spectrometry (AMS) measurement. Several experimental parameters affecting the analytical performance were investigated and compared including sample preboiling operation, aging time, amount of coprecipitating reagent, reagent for pH adjustment, sedimentation time, and organic matter decomposition approach. The overall analytical results show that preboiling and aging are important for obtaining high chemical yields for both Pu and Np, which is possibly related to the aggregation and adsorption behavior of organic substances contained in urine. Although the optimal condition for Np and Pu simultaneous determination requires 5-day aging time, an immediate coprecipitation without preboiling and aging could also provide fairly satisfactory chemical yields for both Np and Pu (50-60%) with high sample throughput (4 h/sample). Within the developed method, (242)Pu was exploited as chemical yield tracer for both Pu and Np isotopes. (242)Pu was also used as a spike in the AMS measurement for quantification of (239)Pu and (237)Np concentrations. The results show that, under the optimal experimental condition, the chemical yields of (237)Np and (242)Pu are nearly identical, indicating the high feasibility of (242)Pu as a nonisotopic tracer for (237)Np determination in real urine samples. The analytical method was validated by analysis of a number of urine samples spiked with different levels of (237)Np and (239)Pu. The measured values of (237)Np and (239)Pu by AMS exhibit good agreement (R(2) ≥ 0.955) with the spiked ones confirming the reliability of the proposed method.

Which is the best 9Be carrier for 10Be/9Be accelerator mass spectrometry?

Commercial 9Be solutions used for chemical preparation of samples for accelerator mass spectrometry contain the cosmogenic long-lived radionuclide 10Be at elevated but different 10Be/9Be levels. Within a systematic study of recently produced solutions, comparison to published data and new data on customised solutions from minerals, we recommend - if no customised solution is available - the 9Be solutions from Australian Chemical Reagents (ACR) or from LGC. They contain 10Be/9Be at the 3.4 × 10-15 level, which is still suitable for the majority of Earth science applications, compared to customised solutions at the 10-16 level for lowest-level studies. Commercial solutions from Scharlab having different lot numbers, i.e. an identification number assigned to a particular lot of material from a single manufacturer, vary in 10Be/9Be by up to a factor of nine. Hence, it seems an advisable strategy to buy a bigger quantity of a single production batch (such as 10 × 100 ml bottles of 9Be at 1 g l-1) and have them tested once at any AMS facility before first use.•The best 9Be carrier for low-level 10Be/9Be applications is a customised one from minerals like phenakite.•The best 9Be carriers for medium- and high-level 10Be/9Be applications are currently from Australian Chemical Reagents (ACR) or from LGC.•As 9Be carriers from Scharlab of different batches (LOT) contain 10Be/9Be at different levels, it is advisable to buy a bigger number of bottles of the same LOT of commercial carriers after being identified to have reasonably low isotope ratios.

41Ca, 14C and 10Be concentrations in coral sand from the Bikini atoll.

Activation measurements of materials exposed to nuclear bomb explosions are widely used to reconstruct the neutron flux for retrospective dosimetry. In this study the applicability of coral CaCO3 as a biogenic neutron fluence dosimeter is tested. The long-lived radioisotopes (41)Ca, (14)C and (10)Be, which had been produced in nuclear bomb explosions, are measured in several coral sand samples from the Bikini atoll at the 600 kV and 200 kV AMS facilities of ETH Zurich. Elevated concentrations of all studied isotopes are found in a sample from the crater that was initially formed by the high-yield nuclear explosion Castle Bravo in 1954 and that had been used as site for several tests afterward. The observed (14)C concentration is considered too large to originate from neutron irradiation of CaCO3 alone. The relatively low concentration of (10)Be found in the crater sample indicates that production of (10)Be during nuclear bomb testing is generally minor. A simple neutron fluence reconstruction is performed on basis of the (41)Ca/(40)Ca ratio.

Isotopic signature of plutonium at Bikini atoll.

Atom ratios of the isotopes (239)Pu, (240)Pu, (241)Pu and (244)Pu were determined in sediments and soils from Bikini atoll using low energy Accelerator Mass Spectrometry. All samples had been contaminated by local fallout from nuclear weapon testing between 1946 and 1958 and show significant variations in the isotopic composition, which are ascribed to the different yields of single tests and to the mixture of material from various devices. Differences in the (244)Pu/(239)Pu ratio (2.8-5.7x10(-4)) are more pronounced than in the (240)Pu/(239)Pu ratio of the same samples and provide complementary information to distinguish the sources of contamination.