Plutonium and uranium contamination in soils from former nuclear weapon test sites in Australia

The British government performed a number of nuclear weapon tests on Australian territory from 1952 through to 1963 with the cooperation of the Australian government. Nine fission bombs were detonated in South Australia at Emu Junction and Maralinga, and a further three fission weapons were detonated in the Monte Bello Islands off the coast of Western Australia. A number of soil samples were collected by the Australian Radiation Laboratories in 1972 and 1978 during field surveys at these nuclear weapon test sites. They were analysed by gamma spectrometry and, for a select few samples, by alpha spectrometry to measure the remaining activities of fission products, activation products and weapon materials. We have remeasured a number of these Montebello Islands and Emu Junction soil samples using the ANTARES AMS facility, ANSTO. These samples were analysed for plutonium and uranium isotopic ratios and isotopic concentrations. Very low ²⁴⁰Pu/²³⁹Pu ratios were measured at both sites (∼0.05 for Alpha Island and ∼0.02 for Emu Field), substantially below global fallout averages. Well correlated but widely varying ²³⁶U and plutonium concentrations were measured across both sites, but 233U did not correlate with these other isotopes and instead showed correlation with distance from ground zero, indicating in situ production in the soils. © 2012 Elsevier B.V. All rights reserved.5 page(s

THE MICROSCOPIC STRUCTURE OF THE M1 MODE IN DY-164

Analyzing probability distributions from water level time series and calculating the first passage time distributions gives the probability of firstly exceeding a given threshold corresponding to a flood or general disaster event. The method will be applied to the water level recordings of the Danube river from which since 100 years very accurate notes exist. The method is transferred to time series of traffic volumes interpreting traffic breakdowns as extreme events and opening a probabilistic interpretation of the capacity of a highway

High-sensitivity isobar-free AMS measurements and reference materials for 55Fe, 68Ge and 202gPb

Isobaric interference represents one of the major limitations in mass spectrometry. For a few cases in AMS with tandem accelerators, isobaric interference is completely excluded like the well-known major isotopes 14C, 26Al, 129I. Additional isotopes are 55Fe (t1/2=2.74years), 68Ge (t1/2=270.9days) and 202Pb (t1/2=52.5kyr), with 68Ge and 202Pb never been used in AMS so far. Their respective stable isobars, 55Mn, 68Zn and 202Hg do not form stable negative ions. The exceptional sensitivity of AMS for 55Fe, 68Ge and 202gPb offers important insights into such different fields like nuclear astrophysics, fundamental nuclear physics and technological applications. VERA, a dedicated AMS facility is well suited for developing procedures for new and non-standard isotopes. AMS measurements at the VERA facility established low backgrounds for these radionuclides in natural samples. Limits for isotope ratios of <10−15, <10−16 and ⩽2×10−14 were measured for 55Fe/56Fe, 68Ge/70Ge and 202Pb/Pb, respectively. In order to generate accurate isotope ratios of sample materials, AMS relies on the parallel measurement of reference materials with well-known ratios. A new and highly accurate reference material for 55Fe measurements with an uncertainty of ±1.6% was produced from a certified reference solution. In case of 68Ge dedicated neutron activations produced a sufficiently large number of 68Ge atoms that allowed quantifying them through the activity of its decay product 68Ga. Finally, for 202Pb, the short-lived isobar 202Tl was produced via neutron activation and served as a proxy for 202Pb AMS measurements. © 2012 Elsevier B.V