Determination of total I and 129

Total iodine and129-iodine in rivers and lakes of Argentina were measured by means of inductively coupled plasma mass spectrometry and accelerator mass spectrometry respectively. The obtained isotopic ratios, higher than the natural level, are explained as the delayed signal from nuclear weapon atmospheric tests. Besides, deposition fluences in catchment areas of the lakes are analyzed. Their latitudinal dependence, similar to the dependence of annual precipitation rates, favours wet deposition as the main 129I fallout mechanism for this region

Probing core polarization around 78Ni: intermediate energy Coulomb excitation of 74Ni

The study of the evolution of nuclear shells far from stability provides fundamental information about the shape and symmetry of the nuclear mean field. Nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Of particular interest is the region of 78Ni where the large neutron excess coincides with a double shell closure. We have recently measured the B(E2; 0+ → 2+) of the 74Ni nucleus in an intermediate-energy Coulomb excitation experiment performed at the National Superconducting Cyclotron Laboratory of the Michigan State University. The 74Ni secondary beam has been produced by fragmentation of 86Kr at 140 AMeV on a thick Be target. Selected radioactive fragments impinged on a secondary 197Au target where the measurement of the emitted γ-rays allows to extract the Coulomb excitation cross section and related structure information. Preliminary B(E2) values do not point towards an enhancement of the transition matrix element and the comparison to what was already measured by Aoi and co-workers in [1] opens new scenarios in the interpretation of the shell evolution of the Z=28 isotopes

Depth profile of 236U/238U in soil samples in La Palma, Canary Islands

The vertical distribution of the 236U/238U isotopic ratio was investigated in soil samples from three different locations on La Palma (one of the seven Canary Islands, Spain). Additionally the 240Pu/239Pu atomic ratio, as it is a well establish tool for the source identification, was determined. The radiochemical procedure consisted of a U separation step by extraction chromatography using UTEVA® Resin (Eichrom Technologies, Inc.). Afterwards Pu was separated from Th and Np by anion exchange using Dowex 1x2 (Dow Chemical Co.). Furthermore a new chemical procedure with tandem columns to separate Pu and U from the matrix was tested. For the determination of the uranium and plutonium isotopes by alpha spectrometry thin sources were prepared by microprecipitation techniques. Additionally these fractions separated from the soil samples were measured by Accelerator Mass Spectrometry (AMS) to get information on the isotopic ratios 236U/238U, 240Pu/239Pu and 236U/239Pu, respectively. The 236U concentrations [atoms/g] in each surface layer (∼2 cm) were surprisingly high compared to deeper layers where values around two orders of magnitude smaller were found. Since the isotopic ratio 240Pu/239Pu indicated a global fallout signature we assume the same origin as the probable source for 236U. Our measured 236U/239Pu value of around 0.2 is within the expected range for this contamination source

Investigation of the 236U/238U Isotope Abundance Ratio in Uranium Ores and Yellow Cake Samples

Uranium ores and yellow cake samples of known geographic origin were investigated for their n(236U)/n(238U) isotope abundance ratio. Samples from four different uranium mines in Australia, Brazil and Canada were selected. Uranium was separated by UTEVA® Resin and was measured by Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA). The measurement of the isotope abundance ratio n(236U)/n(238U) will be used to investigate possible correlations between the original mineral (uranium ore) and the intermediate product (yellow cake). Such correlations are useful indicators for nuclear forensic or for non-proliferation purposes.JRC.DG.E.8-Nuclear Safeguards and Forensic

Pairing and Blocking in High-K Isomers: Variation of the Collective Parameter gR

Using the principle of additivity, the quasi-particle contribution to magnetism in high-K isomers of Lu - Re has been estimated. Based on these estimates band structure branching ratio data is used to explore the behavior of the collective contribution as the number and neutron/proton nature (Np, Nn), of the quasi-particle excitations, change. A striking systematic variation of the collective g-factor gR with the difference, Np – Nn, is revealed. Basic ideas of pairing, its quenching by quasi-particle excitation and the consequent changes to moment of inertia and collective magnetism are discussed. The new found systematic behaviour of gR opens a fresh window on these effects amenable to detailed theoretical investigation

The first use of 236U in the general environment and near a shutdown Nuclear Power Plant

We present a first effort to investigate 236U in the environment near a shutdown nuclear power plant far away from highly contaminated sites, by using accelerator mass spectrometry. The detection limit of about 1 pg 236U allowed us to identify a minimal increase of the 236U/238U isotopic ratio correlated to a peak of 137Cs in river sediments downstream of the nuclear power plant, and to detect anthropogenic 236U also upstream, where it is probably not related to the power plant but to global fallout. The 236U content shoved variations of the 236U/238U isotopic ratio in relation to the chemical-physical characteristics of the sediments. This demonstrates the potential of 236U as an environmental tracer, and as an indicator for releases from nuclear facilities