Transport of Sellafield-derived C-14 from the Irish Sea through the North Channel

Since the early 1950s, the Sellafield nuclear fuel reprocessing plant in Northwest England has released radio-carbon into the Irish Sea in a mainly inorganic form as part of its authorized liquid effluent discharge. In contrast to the trend in which the activities of most radionuclides in the Sellafield liquid effluent have decreased substantially, C-14 discharges have increased since 1994-95. This has largely been due to a policy change favoring marine discharges over atmospheric discharges. C-14 is radiologically important due to its long half life, mobility in the environment, and propensity for entering the food chain. Current models for radionuclide dispersal in the Irish Sea are based on a reversible equilibrium distribution coefficient (k(d)), an approach which has been shown to be inadequate for C-14. Development of predictive models for the fate of Sellafield-derived C-14 requires a thorough understanding of the biogeochemical fluxes between different carbon reservoirs and the processes controlling the net flux of C-14 out of the Irish Sea, through he North Channel. In this study., both an empirical and a halving time approach indicate that close to 100% of the C-14 that is discharged from Sellafield is dispersed beyond the Irish Sea on a time-scale of months in the form of DIC, with little transfer to the PIC, POC, and DOC fractions, indicating that the "dilute and disperse" mechanism is operating satisfactorily. This is consistent with previous research that indicated little transfer of C-14 to Irish Sea sediments, While significant C-14 enhancements have been observed in the biota of the Irish Sea, this observation is not necessarily in conflict with either of the above as the total biomass has to be taken into account in any calculations of C-14 retention within the Irish Sea

Sellafield-derived anthropogenic C-14 in the marine intertidal environment of the NE Irish Sea

The intertidal biota from Parton beach, close to the Sellafield nuclear fuel reprocessing plant, were all found to be enriched in radiocarbon relative to ambient background. The degree of enrichment appears to reflect the positions of the biota in the food chain once the dilution in seaweed from atmospheric uptake is taken into account. Close to the low-water mark, the order was mussels gt limpets gt anemones congruent to winkles gt seaweed. The same order was observed close to the high-water mark, except that anemones were absent from this area. The activities in the biogeochemical fractions of the water column reflect the fact that discharges are primarily in the form of dissolved inorganic carbon (DIC), which is subsequently transferred to the particulate organic carbon (POC) and, to a lesser extent, the dissolved organic carbon (DOC), and finally, the particulate inorganic carbon (PIC). Analysis of intertidal sediment suggests that there is likely to be a gradual increase in the specific activity of C-14 in the inorganic component of this material as Sellafield contaminated organisms die and their shells are ground down by natural processes

Sources of anthropogenic C-14 to the North Sea

The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthropogenic radiocarbon to the UK coastal environment. In a mid-1990s study of C-14 distribution around the UK coast, the pattern of dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high C-14 activities in marine biota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determine whether this C-14 enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucus sp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derived from natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfer times for Tc-99 between Sellafield and various points on the UK coast to determine likely Sellafield- derived C-14 contributions to the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only marginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the significant C-14 enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamental design, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting that there is an input of C-14 to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related. However, there is no other authorized site in the area that could account for the observed C-14 enrichments; therefore, further research is required to ascertain the source of this C-14

Spatial and temporal variations in Pb concentrations and isotopic composition in road dust, farmland soil and vegetation in proximity to roads since cessation of use of leaded petrol in the UK

Results are presented for a study of spatial distributions and temporal trends in concentrations of lead (Pb) from different sources in soil and vegetation of an arable farm in central Scotland in the decade since the use of leaded petrol was terminated. Isotopic analyses revealed that in all of the samples analysed, the Pb conformed to a binary mixture of petrol Pb and Pb from industrial or indigenous geological sources and that locally enhanced levels of petrol Pb were restricted to within 10 m of a motorway and 3 m of a minor road. Overall, the dominant source of Pb was historical emissions from nearby industrial areas. There was no discernible change in concentration or isotopic composition of Pb in surface soil or vegetation over the decade since the ban on the sale of leaded petrol. There was an order of magnitude decrease in Pb concentrations in road dust over the study period, but petrol Pb persisted at up to 43% of the total Pb concentration in 2010. Similar concentrations and spatial distributions of petrol Pb and non petrol Pb in vegetation in both 2001 and 2010, with enhanced concentrations near roads, suggested that redistribution of previously deposited material has operated continuously over that period, maintaining a transfer pathway of Pb into the biosphere. The results for vegetation and soil transects near minor roads provided evidence of a non petrol Pb source associated with roads/traffic, but surface soil samples from the vicinity of a motorway failed to show evidence of such a source

Linear Field Dependence of the Normal-State In-Plane Magnetoresistance of Sr2RuO4

The transverse and longitudinal in-plane magnetoresistances in the normal state of superconducting Sr2RuO4 single crystals have been measured. At low temperatures, both of them were found to be positive with a linear magnetic-field dependence above a threshold field, a result not expected from electronic band theory. We argue that such behavior is a manifestation of a novel coherent state characterized by a spin pseudo gap in the quasi-particle excitation spectrum in Sr2RuO4.Comment: 4 pages + 5 figure

Law, politics and the governance of English and Scottish joint-stock companies 1600-1850

This article examines the impact of law on corporate governance by means of a case study of joint-stock enterprise in England and Scotland before 1850. Based on a dataset of over 450 company constitutions together with qualitative information on governance practice, it finds little evidence to support the hypothesis that common-law regimes such as England were more supportive of economic growth than civil-law jurisdictions such as Scotland: indeed, levels of shareholder protection were slightly stronger in the civil-law zone. Other factors, such as local political institutions, played a bigger role in shaping organisational forms and business practice

Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity

The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx} orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized description of the in-plane electron correlations the superconducting order parameter is found to be a orbital-singlet spin-triplet with two spatial components. The spatial anisotropy is 7%. The different components of the order parameter give rise to two-dimensional gapless fluctuations. The phase transition is of third order. The temperature dependence of the pair density, specific heat, NQR, Knight shift, and susceptibility are in agreement with experimental results.Comment: 20 pages REVTEX, 3 figure

Magnetic field - temperature phase diagram of quasi-two-dimensional organic superconductor lambda-(BETS)_2 GaCl_4 studied via thermal conductivity

The thermal conductivity kappa of the quasi-two-dimensional (Q2D) organic superconductor lambda-(BETS)_2 GaCl_4 was studied in the magnetic field H applied parallel to the Q2D plane. The phase diagram determined from this bulk measurement shows notable dependence on the sample quality. In dirty samples the upper critical field H_{c2} is consistent with the Pauli paramagnetic limiting, and a sharp change is observed in kappa(H) at H_{c2 parallel}. In contrast in clean samples H_{c2}(T) shows no saturation towards low temperatures and the feature in kappa(H) is replaced by two slope changes reminiscent of second-order transitions. The peculiarity was observed below ~ 0.33T_c and disappeared on field inclination to the plane when the orbital suppression of superconductivity became dominant. This behavior is consistent with the formation of a superconducting state with spatially modulated order parameter in clean samples.Comment: 10 pages, 8 figures, new figure (Fig.5) and references added, title change

Domain wall generation by fermion self-interaction and light particles

A possible explanation for the appearance of light fermions and Higgs bosons on the four-dimensional domain wall is proposed. The mechanism of light particle trapping is accounted for by a strong self-interaction of five-dimensional pre-quarks. We obtain the low-energy effective action which exhibits the invariance under the so called \tau-symmetry. Then we find a set of vacuum solutions which break that symmetry and the five-dimensional translational invariance. One type of those vacuum solutions gives rise to the domain wall formation with consequent trapping of light massive fermions and Higgs-like bosons as well as massless sterile scalars, the so-called branons. The induced relations between low-energy couplings for Yukawa and scalar field interactions allow to make certain predictions for light particle masses and couplings themselves, which might provide a signature of the higher dimensional origin of particle physics at future experiments. The manifest translational symmetry breaking, eventually due to some gravitational and/or matter fields in five dimensions, is effectively realized with the help of background scalar defects. As a result the branons acquire masses, whereas the ratio of Higgs and fermion (presumably top-quark) masses can be reduced towards the values compatible with the present-day phenomenology. Since the branons do not couple to fermions and the Higgs bosons do not decay into branons, the latter ones are essentially sterile and stable, what makes them the natural candidates for the dark matter in the Universe.Comment: 34 pages, 2 figures, JHEP style,few important refs. adde