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Gaseous fission products have been produced via thermal neutron irradiation of a highly-enriched uranium target and extracted using a custom gas processing system for measurement on a prototype, high-resolution β − γ coincidence detection system. The gas was extracted and measured in two stages in order to measure the prompt and β−–delayed fission products. This paper presents an overview of the system used to produce gaseous fission products, and the results of the advanced coincidence spectrometry techniques used to identify and quantify decays from the radionuclides produced, including the noble gases 85Kr, 85mKr, 88Kr, 133Xe, 135Xe, 133mXe and 135mXe, as well as 133I and 88Rb. The measurements were validated by determination of the nuclear decay half-lives, specifically for the ground state decay of 135Xe, which was found to be 9.15(49) hours and consistent with the literature value. This work demonstrates the UK capability to produce gaseous radionuclides for quality assurance and calibration purposes in Radionuclide Laboratories supporting the Comprehensive Nuclear-Test-Ban Treaty (CTBT).

The predatory “killer shrimp” Dikerogammarus villosus invaded Britain from mainland Europe in 2010. Originating in the Ponto-Caspian region, this invader has caused significant degradation of European freshwater ecosystems by predating and competitively excluding native invertebrate species. In contrast to continental Europe, in which invasions occurred through the migration of large numbers of individuals along rivers and canals, the invasion of Great Britain must have involved long distance dispersal across the sea. This makes the loss of genetic diversity and of debilitating parasites more likely. Analysis of nuclear microsatellite loci and mitochondrial DNA sequences of D. villosus samples from the four known populations in Britain reveal loss of rare alleles, in comparison to reference populations from the west coast of continental Europe. Screening of the British D. villosus populations by PCR detected no microsporidian parasites, in contrast with continental populations of D. villosus and native amphipod populations, most of which are infected with microsporidia. These findings suggest that the initial colonisation of Great Britain and subsequent long distance dispersal within Britain were associated with genetic founder effects and enemy release due to loss of parasites. Such effects are also likely to occur during future long-distance dispersal events of D. villosus to Ireland or North America.