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Actinides accumulate within aquatic biota in concentrations several orders of magnitude higher than in the seawater [the concentration factor (CF)], presenting an elevated radiological and biotoxicological risk to human consumers. CFs currently vary widely for the same radionuclide and species, which limits the accuracy of the modeled radiation dose to the public through seafood consumption. We propose that CFs will show less dispersion if calculated using a time-integrated measure of the labile (bioavailable) fraction instead of a specific spot sample of bulk water. Herein, we assess recently developed configurations of the diffusive gradients in thin films (DGT) sampling technique to provide a more accurate predictor for the bioaccumulation of uranium, plutonium, and americium within the biota of the Sellafield-impacted Esk Estuary (UK). We complement DGT data with the cross-flow ultrafiltration of bulk seawater to assess the DGT-labile fraction versus the bulk concentration. Sequential elution of Fucus vesiculosis reveals preferential internalization and strong intracellular binding of less particle-reactive uranium. We find significant variations between CF values in biota calculated using a spot sample versus using DGT, which suggest an underestimation of the CF by spot sampling in some cases. We therefore recommend a revision of CF values using time-integrated bioavailability proxies., ACS ES&T Water, 2 (10), ISSN:2690-0637

Nuclear reactor process control is typically monitored for pure β-emitting radionuclides via manual sampling followed by laboratory analysis, leading to delays in data availability and response times. The development of an in situ microfluidic Lab on Chip (LoC) system with integrated detection capable of measuring pure β-emitting radionuclides presents a promising solution, enabling a reduction in occupational exposure and cost of monitoring whilst providing improved temporal resolution through near real-time data acquisition. However, testing prototypes with radioactive sources is time-consuming, requires specialist facilities/equipment, generates contaminated waste, and cannot rapidly evaluate a wide range of designs or configurations. Despite this, modelling multiple design parameters and testing their impact on detection with non-radioactive substitutes has yet to be adopted as best practice. The measurement of pure β emitters in aqueous media relies on the efficient transport of photons generated by the Cherenkov effect or liquid scintillators to the detector. Here we explore the role of numerical modelling to assess the impact of optical cell geometry and design on photon transmission and detection through the microfluidic system, facilitating improved designs to realise better efficiency of integrated detectors and overall platform design. Our results demonstrate that theoretical modelling and an experimental evaluation using non-radiogenic chemiluminescence are viable for system testing design parameters and their impact on photon transport. These approaches enable reduced material consumption and requirement for specialist facilities for handling radioactive materials during the prototyping process. This method establishes proof of concept and the first step towards numerical modelling approaches for the design optimisation of microfluidic LoC systems with integrated detectors for the measurement of pure β emitting radionuclides via scintillation-based detection.

Shelf sea sediments are natural, long-term carbon sinks that may be managed for Blue Carbon (BC) storage to offset greenhouse gas emissions and contribute to nations ‘Net Zero’ ambitions. The Isle of Man in the Irish Sea has territorial waters equivalent to approximately 85% of its total jurisdiction, and significant potential for BC offsetting through seabed management. The Island’s Government is developing a comprehensive BC management plan to maximise carbon sequestration and restore seabed biodiversity and wider ecosystem services. We determined the effects of disturbance on sedimentary carbon stocks and accumulation rates in the western territorial sea, a region of mud-dominated sediment with elevated disturbance from Nephrops norvegicus bioturbation and bottom-contact fishing activities. Sediment cores were collected from approximately 5 to 12 nautical miles off the west coast of the Isle of Man, at depths from 60 m to 120 m. The cores were sectioned and analysed using: elemental analysis and isotope ratio mass spectrometry to quantify organic and inorganic carbon stocks; and gamma-ray spectrometry and alpha spectrometry to identify and quantify radionuclides of Cs-137, Pb-210, Am-241 and Po-210 to determine sedimentation rates. Complete sediment cores were scanned using X-ray to generate radiographs and laminographs, to determine internal core structure and identify N. norvegicus burrows. The results show that organic/inorganic carbon and sedimentation rates in offshore sediments vary over time and space. Analysis is ongoing to ascertain if these variations are related to disturbance of the sedimentary system, using indicators of fishing intensities and N. norvegicus bioturbation. Results of this analysis will be presented to elucidate the effects of disturbance on sedimentary carbon stocks and accumulation.

Nuclear discharges to the oceans have given rise to significant accumulations of radionuclides in sediments which can later remobilise back into the water column. A continuing supply of radionuclides to aquatic organisms and the human food chain can therefore exist, despite the absence of ongoing nuclear discharges. Radionuclide remobilisation from sediment is consequently a critical component of the modelled radiation dose to the public. However, radionuclide remobilisation fluxes from contaminated marine sediments have never been quantitatively determined in-situ to provide a valid assessment of the issue. Here, we combine recent advances in the Diffusive Gradients in Thin Films (DGT) sampling technique with ultrasensitive measurement by accelerator mass spectrometry (AMS) to calculate the remobilisation fluxes of plutonium, americium and uranium isotopes from the Esk Estuary sediments (UK), which have accumulated historic discharges from the Sellafield nuclear reprocessing facility. Isotopic evidence indicates the local biota are accumulating remobilised plutonium and demonstrates the DGT technique as a valid bioavailability proxy, which more accurately reflects the elemental fractionation of the actinides in the biota than traditional bulk water sampling. These results provide a fundamental evaluation of the re-incorporation of bioavailable actinides into the biosphere from sediment reservoirs. We therefore anticipate this work will provide a tool and point of reference to improve radiation dose modelling and contribute insight for other environmental projects, such as the near-surface and deep disposal of nuclear waste., Water Research, 221, ISSN:0043-1354, ISSN:1879-2448

A numerical simulation method has been developed to describe the transfer of analytes between solid and aqueous phases and assessed for a commercially available extraction chromatography resin (UTEVA resin). The method employs an ordinary differential equation solver within the LabVIEW visual programming language. The method was initially developed to describe a closed batch system. The differential equations and kinetic rate constants determined under these conditions were then applied to the flow-through column geometry. This was achieved by modelling the resin bed as a series of discrete vertically stacked sections, thereby generating an array of solid and aqueous concentration values. Axial flow was simulated by the advancement of the aqueous phase values by one array position with the value advancing from the final array position representing the column output concentration. An investigation into the observed difference in breakthrough profiles obtained under repeated conditions revealed the relative tolerance of the numerical simulation method to errors in each input parameter. Additional physical processes such as backpressure and leaching of the extractant were considered as an explanation for observed inconsistencies between experimental and simulated datasets. An elution sequence featuring multiple eluents was also simulated, demonstrating that the prediction of analyte separation sequences is possible. The potential to develop the LabVIEW coding into user friendly software with an extendable kinetic database is also discussed. This software will be a useful tool to radiochemists particularly in the development of new analytical methods using automated separation systems.

A compact dual zone, two work-tube, vertical tube furnace system (Raddec Pyrolyser-Mini) has been designed for the determination of H-3 and C-14 in decommissioning wastes. An optimised methodology was developed following improvements to sample holder and bubbler trap design, sample loading and loading temperature, as well as length and style of heating programmes. A significant efficiency enhancement was obtained through 'hot-loading' of the sample into the furnace at 600 °C before finally ramping to 900 °C. Direct trapping of H-3 and C-14 in a scintillation vial located in a special anti-suck-back bubbler further improved operations, leading to a reduction in analysis time and measurement sensitivity. Co-trapping of the analytes and dual-label liquid scintillation counting also proved effective. Overall, the developed methodology led to a reduced analyte extraction/trapping time of 150 min whilst achieving limits of detection of

Quantitative extraction of tritium from a sample matrix is critical to efficient measurement of the low-energy pure beta emitter. Oxidative pyrolysis using a tube furnace (Pyrolyser) has been adopted as an industry standard approach for the liberation of tritium (Warwick et al. in Anal Chim Acta 676:93–102, 2010) however pyrolysis of organic-rich materials can be problematic. Practically, the mass of organic rich sample combusted is typically limited to

Liquid scintillation spectrometry is widely used for the analysis of alpha and beta emitting radionuclides. Robust calibration of liquid scintillation (LS) spectrometers is fundamental to accurate LS measurement but at the same time is time consuming and costly, particularly if a wide range of radionuclides are analysed by the laboratory. The frequency of the calibration varies in different laboratories and is based on many practical and operational factors. This work summarizes the observations regarding variations in 1220 Quantulus spectrometers efficiency calibrations performed annually using various radionuclides: 3H 63Ni, 55Fe, 36Cl, 45Ca, 147Pm, 241Pu, 99Tc for a period of 9 years and discusses the implication to calibration frequency.

Tritium is ubiquitous in and around nuclear plants, being formed via neutron capture by 2H, 6Li, 10B and 14N and via ternary fission. The highly mobile nature of 3H species results in widespread distribution of the radionuclide. Predictive modeling of 3H activity concentrations is challenging and direct measurement of 3H activities in materials is the preferred approach to underpin waste and environmental assessments. For well over a decade, the UK nuclear industry has engaged in a significant program of site decommissioning of its first generation reactors. This has resulted in a high demand for the rapid characterization of 3H in a diverse range of matrices, including concretes, metals, plastics, sludges, resins, soils and biota. To support such assessments, it has been necessary to develop dedicated instrumentation in parallel with robust radioanalytical methodologies; namely a multi-tube furnace and a high-capacity, closed (pressurized) oxygen combustion system. Data are presented on the development and validation of these instruments, designed specifically to enable the quantitative extraction of 3H (and other volatile radionuclides) from diverse sample types. Furthermore the furnace system has been employed as a tool to gain insights into the 3H association in decommissioning and environmental matrices exposed to 3H arising from nuclear power plant operations through tritium evolution with temperature profiling. The impact of the chemical speciation of 3H on analytical strategy is discussed. A major benefit of the multi-sample furnace is its ease of use and applicability to 3H determination in virtually any sample type. The complementary HBO2 oxygen combustion system has been developed for the quantitative oxidation of organic-rich samples (e.g. wood, plastic, oil, biota) and analytical data prove its effectiveness.

The ability to efficiently identify potential radiological threats or actual radioactive assaults on society and the environment demands a sophisticated and dedicated infrastructure comprising specialised personnel, mobile and fixed laboratories and advanced analytical instrumentation. Most developed countries have such systems but ensuring a long-term and resilient capability is recognised as a perennial challenge. National government laboratories specialising in nuclear forensics play a key role in maintaining capability but these organisations continue to benefit significantly from interdisciplinary and innovative contributions derived from universities and other research institutions. This review provides an insight into the range of technologies used and also provides a broad overview of applied techniques and instrumentation that contribute to rapid screening and analysis in the context of nuclear forensics and radiological emergencies.

The issue surrounding the shortage of reference materials has long been discussed and becoming progressively important as the nuclear industry faces the challenges of decommissioning, increasing the requirement for the analysis of a wide range of radionuclides in diverse sample types. To meet demand the radiochemical methods need to be flexible and robust whilst maintaining a high level of quality, essential to underpinning public and environmental safety in a highly regulated sector. Integral to the process of method development, validation, and performance evaluation is the use of reference materials which provide the confidence in the measurement. Currently there is an acute shortage of certified, solid, reference materials due to costs associated with production and availability of suitable material. An alternative to adopting the formal intercomparison exercise approach was explored by the UK’s Analyst Informal Working Group (AIWG). The members recognized the shortage of suitable, solid materials containing a range of alpha, beta and gamma emitters and identified three mixed biota samples. The molluscs, winkles and crustacea contained a mix of environmental activity level radionuclides (14C, 40K, 90Sr, 99Tc, 137Cs, 239+240Pu, 241Pu and 241Am) and were dispatched to 12 laboratories in the UK and Europe in the Summer of 2017. Following analysis, using several techniques, the results were evaluated in terms of levels of precision, sensitivity and limits of detection. The results of the study showed all the radionuclides were successfully analysed by the laboratories to a level of precision and accuracy consistent with that achieved through routine analysis. The exercise demonstrated the viability and benefits of adopting the intercomparison exercise approach, which uses consensus values, to produce fit for purpose reference materials to practically address the shortage.

Decommissioning and monitoring around nuclear sites presents challenges with regards to the range of sample matrices and radionuclides that must be accurately characterised. Over the last few decades, inductively coupled plasma mass spectrometry (ICP-MS) has been increasingly used in the nuclear sector as a rapid alternative to decay counting techniques for long-lived radionuclides, as well as an expanding range of shorter-lived radionuclides. The presence of various interferences still presents a major challenge in achieving accurate measurements, often necessitating extensive chemical clean-up prior to measurement. This study evaluates the potential application of tandem ICP-MS/MS for the measurement of a range of radionuclides of interest to nuclear decommissioning and waste management. The flexibility of the instrumental setup is shown in achieving improved interference removal compared to alternative instrument designs, improving sample throughput by reducing reliance on offline separation, and increasing the potential application of ICP-MS/MS for routine measurement of difficult-to-measure radionuclides.

Robust and reliable radiochemical analysis is the key factor in the appropriate disposal and management of radioactive wastes arising from the nuclear industry, decommissioning projects, medical, and scientific institutions. There is an ever increasing number of challenging projects that involve rapid analysis of large batches of samples and require rigorous quality control systems capable of positively identifying incorrect or questionable results which may lead to costly consequences at the latter stages of the waste disposal process. Combination of SQP(E) and SQPI LSC spectral parameters allows for quick and reliable checking of large datasets without the need for individual manual spectrum checks.

The application of Principal Components Analysis (PCA) to U and Th series gamma spectrometry data provides a discriminatory tool to help determine the provenance of illicitly recovered uranium ore concentrates (UOCs). The PCA is applied to a database of radiometric signatures from 19 historic UOCs from Australia, Canada, and the USA representing many uranium geological deposits. In this study a key process to obtain accurate radiometric data (gamma and alpha) is to digest the U-ores and UOCs using a lithium tetraborate fusion. Six UOCs from the same sample set were analysed ‘blind’ and compared against the database to identify their geolocation. These UOCs were all accurately linked to their correct geolocations which can aid the forensic laboratory in determining which further analytical techniques should be used to improve the confidence of the particular location.

Microplastics are an increasingly important contaminant in the marine environment. Depending on their composition and degree of biofouling, many common microplastics are less dense than seawater and so tend to float at or near the ocean surface. As such, they may exhibit high concentrations in the sea surface microlayer (SML – the upper 1–1000 μm of the ocean) relative to deeper water. This paper examines the accumulation of microplastics, in particular microfibres, in the SML in two contrasting estuarine systems – the Hamble estuary and the Beaulieu estuary, southern U.K., via a novel and rapid SML-selective sampling method using a dipped glass plate. Microplastic concentrations (for identified fibres, of 0.05 to 4.5 mm length) were highest in the SML-selective samples (with a mean concentration of 43 ± 36 fibres/L), compared to

International audience; Organically bound tritium (OBT) has become of increasing interest within the last decade, with a focus on its behaviour and also its analysis, which are both important to assess tritium distribution in the environment and dose consequences. After the first OBT International Workshop which was held in France in May 2012, an international working group was created. The expected benefits are the following remove or reduce uncertainty in OBT analysis results, provide better OBT model validation data and better public dose results, increase the number of potential measuring OBT laboratories, validate all of the stages of the procedures based on a larger population and more statistically significant results, and investigate the feasibility of CRM's and RM's production. In this framework, three OBT exercises were organised; the 1st one on potatoes was conducted in 2013 by the Canadian National Laboratories (former AECL) with about 20 participating labs from around the world, the 2nd one on a sediment was organised in 2014 by GAU Radioanalytical (University of Southampton) on a sediment with again about 20 participating labs and the third one on wheat was organised in 2015 by the Commissariat à l’énergie atomique (CEA) with about 25 participating labs. © 2017

Many methods allow analysing the various forms of tritium in environmental samples; however, there are no published standard methods for measuring organically bound tritium (OBT). Furthermore, there are no certified reference materials of OBT for environmental samples. In environmental samples (plants and animals), the measurement of the various tritium fractions requires extraction of the free water, often through freeze drying processes. Combustion of the dry sample is then carried out to recover organically bound tritium in the combustion water. By measuring these water fractions, the tissue-free water tritium (TFWT) and the OBT concentration can be assessed. However, these techniques are tricky and sometimes not available in all monitoring labs. Indeed, most of them measure only the TFWT fraction in food samples, such as wine or milk. Researches to promote the use of validated procedures are on-going in several countries. However, for almost all comparison exercise organisers it is difficult on a yearly basis to provide the samples and to realise the statistical treatment of the results. Therefore, to improve OBT analytical skills, an international task group devoted to the improvement of OBT analytical procedures was created to overcome these limitations. For the first exercise about 20 labs from 8 countries were registered. The samples, specially-prepared potatoes, were provided in March 2013 to each participant. Technical information and results from this first exercise are discussed here for all the labs which have realised the five replicates necessary to allow a reliable statistical treatment. From this work an optimised procedure can start to be developed to deal with OBT analysis and will guide subsequent planned OBT trials by the international group.

This paper describes an early-stage evaluation of a purpose-designed extraction / detection system that can be deployed by non-specialists either on-site or as part of a mobile laboratory. The system comprises three main components; (1) an optimised compact extraction system for recovery of radionuclides from the waste form; (2) an extraction test strip designed to recover the radionuclides from the waste digest; (3) a scintillation-based detection system capable of quantification of alpha, low energy beta and high energy beta emitting radionuclides. Data are presented on the preliminary assessment of the extraction / detection system for the measurement of 90Sr and 99Tc in aqueous wastes.

There is an increasing demand for rapid and effective analytical tools to support nuclear forensic investigations of seized or suspect materials. Some methods are simply adapted from other scientific disciplines and can effectively be used to rapidly prepare complex materials for subsequent analysis. A novel sample fusion method is developed, tested, and validated to produce homogeneous, flux-free glass beads of geochemical reference materials (GRMs), uranium ores, and uranium ore concentrates (UOC) prior to the analysis of 14 rare earth elements (REE) via laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The novelty of the procedure is the production of glass beads using 9 parts high purity synthetic enstatite (MgSiO3) as the glass former with 1 part of sample (sample mass ∼1.5 mg). The beads are rapidly prepared (∼10 min overall time) by fusing the blended mixture on an iridium strip resistance heater in an argon-purged chamber. Many elements can be measured in the glass bead, but the rare earth group in particular is a valuable series in nuclear forensic studies and is well-determined using LA-ICP-MS. The REE data obtained from the GRMs, presented as chondrite normalized patterns, are in very good agreement with consensus patterns. The UOCs have comparable patterns to solution ICP-MS methods and published data. The attractions of the current development are its conservation of sample, speed of preparation, and suitability for microbeam analysis, all of which are favorable for nuclear forensics practitioners and geochemists requiring REE patterns from scarce or valuable samples.

The efficient characterization of nuclear waste materials represents a significant challenge during nuclear site decommissioning, with a range of radionuclides requiring measurement in varied and often complex sample matrices. Of the available measurement techniques, inductively coupled plasma mass spectrometry (ICP-MS) has traditionally been applied to long-lived radionuclides, particularly in the actinide series. With recent advances in the technique, both the sensitivities achievable and number of radionuclides potentially measurable has expanded, with the reduced procedural time offering significant economic benefits to nuclear site waste characterization compared with traditional radiometric (typically alpha and beta spectrometry) techniques. This review provides a broad assessment of recent developments, improvements in capability and describes the advantages and drawbacks of ICP-MS with regards to sample introduction and instrument design. The review will be of interest to international agencies concerned with nuclear decommissioning as well as nuclear site laboratories, project managers and sites involved in environmental monitoring and nuclear forensics.

While both mass spectrometry and alpha-particle spectrometry have been widely used for measuring alpha activities, the former is preferred since many laboratories are not equipped with ICP-MS and MC-ICP-MS systems. In this study, three electrodeposition techniques using ammonium chloride, ammonium oxalate and ammonium sulphate as electrolyte solutions were applied and evaluated for the preparation of uranium, plutonium and americium sources for alpha-particle spectrometry. Changes in pH and temperature throughout the electrodeposition process were measured every 15 min, together with percentage deposition every 30 min. The percentage deposition in each method was checked at 300, 400 and 500 mA, and the optimised time and current were determined.

Traditionally in bioassay monitoring, 3H determinations in urine have been performed using either direct counting (with or without sample decolourisation) or distillation whilst 14C has been determined on separate sub-samples following chemical isolation of the carbon from samples. Although these techniques are relatively straightforward they do not permit simultaneous determination of 3H/14C. For 3H, direct counting can be significantly affected by variations in sample composition/colour resulting in varying degrees of sample quench, does not distinguish between aqueous/organically-bound 3H and is limited to small sample sizes. This study describes the use of purpose built multi-tube combustion furnace for the simultaneous extraction and determination of 3H and 14C. The technique is insensitive to sample composition and can be adapted to measure Tritiated water (HTO) and organically bound tritium separately. The development of a multi-tube system with integrated cool-down facility permits rapid throughput of high sample numbers and has been proven effective in decommissioning waste characterisation. In addition, the furnace-based technique is capable of processing larger sample sizes, increasing analytical sensitivity and accuracy of dose assessment.

Bacterioplankton are the primary consumers of dissolved organic matter in the ocean, thus the quantification of bacterioplankton production (BP) is essential to our understanding of carbon cycling in the largest ecosystems on Earth. We compared BP, measured as the rate of 14C-leucine or 3H-leucine uptake at close to saturating concentration (20 nmol L−1), with ambient uptake measured from dilution bioassays. We hypothesized that saturation with leucine would lead to its respiration as a carbon source, thereby not truly representing ambient BP. Seawater was collected from the photic zone throughout the Atlantic Ocean. Respiration as a proportion of total consumption (uptake + respiration) of close to ambient (0.4 nmol L−1) and close to saturating (20 nmol L−1) 14C-leucine concentrations were compared. Saturating 3H-leucine additions overestimated ambient leucine uptake at low rates (200% ± 100% ambient) and underestimated uptake at high rates (90% + 20% ambient). The proportion of total leucine uptake that was respired was threefold higher for 20 nmol L−1 14C-leucine additions than 0.4 nmol L−1 14C-leucine additions (15% ± 8% and 5% ± 4%, respectively). Consequently, microbial efficiency of leucine assimilation—an indicator of bacterioplankton growth efficiency—was significantly higher and more stable at close to ambient 14C-leucine additions than at saturating concentrations (95% ± 4% and 85% ± 8%, respectively). Thus, saturation of oligotrophic open Atlantic Ocean bacterioplankton with leucine, or other molecules indicative of microbial metabolism, leads to the measurement of a response to a nutrient addition, rather than an ambient measurement.

A straightforward and rapid method has been developed for the determination of 241Pu activities. Pu is chemically separated from the sample, purified and electrodeposited to produce a source for alpha spectrometric determination of 238Pu and 239,240Pu. Pu is stripped from the disc with concentrated nitric acid and extracted into tri-octylphosphine oxide (TOPO)/toluene. The organic extract is then mixed directly with commercial liquid scintillation cocktail without any further purification procedures and the sample counted on a Wallac 1220 Quantulus liquid scintillation counter (LSC). 241Pu activity is estimated via the 242Pu yield monitor acquired by alpha spectrometry measurement. Experimental results for the performance testing of a low-level liquid scintillation spectrometer and the data for the evaluation of the method using standard reference materials are presented.

Within the last ten years there has been increasing interest in tritium behaviour and distribution in the environment. This is based partly on empirical findings that tritium discharged mostly as HTO can become transformed into organic forms in environmental samples. An international workshop was convened in France in 2012 to gather the scientific community interested in organically bound tritium to share their experience and to establish a current state of knowledge. This paper summarises the outcome of the workshop, which aimed to improve skills concerning OBT (Organically Bound Tritium) determination, transfer and behaviour in the environment. In order to improve OBT measurement credibility, it was decided to conduct and promote OBT analysis through inter-laboratory exercises. This practice will reduce uncertainty in OBT analysis results, providing better OBT model validation data and public dose assessments. © EDP Sciences, 2013.

The macrotidal Severn Estuary (southwestern UK) has received a broad range of industrial discharges since the beginning of the Industrial Revolution. A more recent anthropogenic input to the estuary has been technogenic tritium (specifically organically bound tritium, OBT). This was derived from a specialized industrial laboratory producing custom radiolabeled compounds for life science research and diagnostic testing from 1980 until 2008. While it was generally acknowledged that the radiological impact of the tritium discharges into the Estuary was small, public concern motivated the company and regulatory agencies to commission several research studies from 1998 to 2005 to better understand their environmental impact. This study examined OBT interaction with estuarine sediment by acquiring a broad range of geochemical and sedimentological data from a suite of sediment cores collected from the northern side of the Estuary. Two important observations are that the OBT compounds are strongly bound to the clay/silt fraction of sediment and that the down-core OBT profiles in intertidal and subtidal sediments are broadly similar to the discharge record. Geochemical and chronometric methods (Cu, Pb and Zn elemental profiles, (210)Pb, (137)Cs) provide important corroboration of the OBT record. A key additional piece of evidence that firmly authenticated the established chronology was the discovery of a previously unreported sedimentary marker layer that was generated by a major storm surge that occurred on December 13, 1981. Although this study has provided clear evidence of systematic accumulation of OBT in sedimentary sinks of the region, an estimation of its depositional inventory shows it represents only a small fraction of the total discharge. This modest retention in the principal sedimentary sinks of the Severn Estuary system reflects the particular dynamics of this highly macrotidal sediment starved estuary.

Large volumes of potentially tritium-contaminated waste materials are generated during nuclear decommissioning that require accurate characterisation prior to final waste sentencing. The practice of initially determining a radionuclide waste fingerprint for materials from an operational area is often used to save time and money but tritium cannot be included because of its tendency to be chemically mobile. This mobility demands a specific measurement for tritium and also poses a challenge in terms of sampling, storage and reliable analysis. This study shows that the extent of any tritium redistribution during storage will depend on its form or speciation and the physical conditions of storage. Any weakly or moderately bound tritium (e.g. adsorbed water, waters of hydration or crystallisation) may be variably lost at temperatures over the range 100-300 °C whereas for more strongly bound tritium (e.g. chemically bound or held in mineral lattices) the liberation temperature can be delayed up to 800 °C. For tritium that is weakly held the emanation behaviour at different temperatures becomes particularly important. The degree of (3)H loss and cross-contamination that can arise after sampling and before analysis can be reduced by appropriate storage. Storing samples in vapour tight containers at the point of sampling, the use of triple enclosures, segregating high activity samples and using a freezer all lead to good analytical practice.

A novel manganese dioxide (MnO2) resin is suitable for the determination and decontamination of lead isotopes (208Pb, 207Pb, 206Pb) in aqueous solutions at trace concentrations. This is desirable due to the toxic nature and high abundance of lead in the environment. Current techniques are both time consuming, expensive and not suitable for low-level lead decontamination. The MnO2 resin has been demonstrated to pre-concentrate with extraction efficiency above 90% for a range of pH values, and with a mean extraction of 92.5% from fresh waters at a flow rate of 100 ml min−1. The lead distribution coefficient is 1.3 × 104 (pH 7) with tolerance to calcium and sodium. Adsorption isotherms have been investigated and the resin shown to follow the Langmuir adsorption isotherm with a saturation point of 41.5 mg per g of MnO2 resin.

Statistical analysis has been performed on the gross alpha- and beta-activity measurements of surface waters collected at the Atomic Weapons Establishment at Aldermaston (UK) during the period January 2002–September 2005. The results have been found to follow a lognormal distribution and this has important applications when considering gross activity exemption thresholds. This implies that the gross activity is the multiplicative product of many small independent factors, such as meteorology, flow conditions and site operations. The influence of meteorological parameters has been investigated using linear regression, and some correlation has been identified between gross beta-activity and parameters indicative of fine weather. Variations in gross activity have been considered on monthly, weekly and daily timescales and characterised using the geometric mean and geometric standard deviation in accordance with the properties of the lognormal probability density function.

A novel technique has been developed for determining the 212 Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from 212 Pb varies, and is difficult to experimentally measure due to its relatively short half-life ( t ½ = 10.6 h) and low environmental activity ( −1 ). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l −1 with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of 212 Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.

Sudden increases in the background gamma-radiation dose may occur due to the removal of (222)Rn and (220)Rn progeny from the atmosphere by wet deposition mechanisms. This contribution has been measured using a Geiger-Muller detector at the Atomic Weapons Establishment (Aldermaston, UK) during July 2005-April 2006. The results are approximated by a log-normal distribution and there were nine separate occurrences of the gamma-radiation dose exceeding 125% of the geometric mean value. The increases were associated with periods of heavy rainfall, although no correlation was evident between the dose rate and the amount of rainfall, as increased rainfall dilutes the activity further rather than increasing its atmospheric removal. The events were preceded by periods of fine weather and atmospheric stability that allow for the build-up of (222)Rn and (220)Rn progeny. Similar increases in gamma-radiation dose have been measured at a nearby monitoring station situated approximately 11 miles from Aldermaston. Increases in gamma-radiation dose during heavy rainfall have also been observed throughout the UK, that followed the trajectory of an air mass. All events decreased to typical values within 1-2 h as the water permeated into the ground below and the radioactivity decayed away.

The routine application of liquid scintillation counting to (41)Ca determination has been hindered by the absence of traceable calibration standards of known (41)Ca activity concentrations. The introduction of the new IRMM (41)Ca mass-spectrometric standards with sufficiently high (41)Ca activities for radiometric detection has partly overcome this although accurate measurement of stable Ca concentrations coupled with precise half-life data are still required to correct the certified (41)Ca:(40)Ca ratios to (41)Ca activity concentrations. In this study, (41)Ca efficiency versus quench curves have been produced using the IRMM standard, and their accuracy validated by comparison with theoretical calculations of (41)Ca efficiencies. Further verification of the technique was achieved through the analysis of (41)Ca in a reactor bioshield core that had been previously investigated for other radionuclide variations. Calcium-41 activity concentrations of up to 25 Bq/g were detected. Accelerator mass spectrometry (AMS) measurements of the same suite of samples showed a very good agreement, providing validation of the procedure. Calcium-41 activity concentrations declined exponentially with distance from the core of the nuclear reactor and correlated well with the predicted neutron flux.

35S-Methionine and 3H-leucine bioassay tracer experiments were conducted on two meridional transatlantic cruises to assess whether dominant planktonic microorganisms use visible sunlight to enhance uptake of these organic molecules at ambient concentrations. The two numerically dominant groups of oceanic bacterioplankton were Prochlorococcus cyanobacteria and bacteria with low nucleic acid (LNA) content, comprising 60% SAR11-related cells. The results of flow cytometric sorting of labelled bacterioplankton cells showed that when incubated in the light, Prochlorococcus and LNA bacteria increased their uptake of amino acids on average by 50% and 23%, respectively, compared with those incubated in the dark. Amino acid uptake of Synechococcus cyanobacteria was also enhanced by visible light, but bacteria with high nucleic acid content showed no light stimulation. Additionally, differential uptake of the two amino acids by the Prochlorococcus and LNA cells was observed. The populations of these two types of cells on average completely accounted for the determined 22% light enhancement of amino acid uptake by the total bacterioplankton community, suggesting a plausible way of harnessing light energy for selectively transporting scarce nutrients that could explain the numerical dominance of these groups in situ.

Iron leached from volcanic islands was hypothesised to naturally fertilise the high-nutrient low-chlorophyll (HNLC) waters of the Antarctic Circum Polar Current and to cause recurrent phytoplankton blooms or high-chlorophyll (HC) areas in the wake of the Crozet Islands. As part of CROZEX, the effect of Fe-fertilisation on microbial community was examined by comparing microbial standing stocks and microbial turnover rates of dissolved organic molecules and iron in the HNLC and HC waters in the vicinity of the Crozet Isles. Bacterioplankton and ultraplanktonic algae were enumerated by flow cytometry. Microbial turnover and ambient concentrations of amino acids and glucose in surface waters were bioassayed using an isotopic dilution technique. Microbial uptake of iron was estimated using a carrier-free 55Fe tracer approach. The data set generated did not reveal statistically significant seasonal changes above the observed high spatial variability in the studied area. Statistically significant higher biomass (1.5 times) of heterotrophic bacterioplankton (HB) as well as higher microbial turnover of organic molecules (10 times) were observed in the HC waters relative to the HNLC waters, while relative iron uptake was nearly eight times lower in the HC waters. However, the difference in HB standing stocks in the 100–200 m water layer between the two compared water types was statistically insignificant. Hence, the HC surface waters in austral summer showed higher microbial activity with decreased iron dependency relative to the HNLC waters of the Southern Ocean, in agreement with higher productivity of the waters to the north of the Crozet Islands.

A rapid and effective preparative procedure has been evaluated for the accurate determination of low-energy (40-200 keV) gamma-emitting radionuclides ((210)Pb, (234)Th, (226)Ra, (235)U) in uranium ores and uranium ore concentrates (UOCs) using high-resolution gamma ray spectrometry. The measurement of low-energy gamma photons is complicated in heterogeneous samples containing high-density mineral phases and in such situations activity concentrations will be underestimated. This is because attenuation corrections, calculated based on sample mean density, do not properly correct where dense grains are dispersed within a less dense matrix (analogous to a nugget effect). The current method overcomes these problems using a lithium tetraborate fusion that readily dissolves all components including high-density, self-attenuating minerals/compounds. This is the ideal method for dissolving complex, non-volatile components in soils, rocks, mineral concentrates, and other materials where density reduction is required. Lithium borate fusion avoids the need for theoretical efficiency corrections or measurement of matrix matched calibration standards. The resulting homogeneous quenched glass produced can be quickly dissolved in nitric acid producing low-density solutions that can be counted by gamma spectrometry. The effectiveness of the technique is demonstrated using uranium-bearing Certified Reference Materials and provides accurate activity concentration determinations compared to the underestimated activity concentrations derived from direct measurements of a bulk sample. The procedure offers an effective solution for initial nuclear forensic studies where complex refractory minerals or matrices exist. It is also significantly faster, safer and simpler than alternative approaches.

A rapid and robust procedure is described for the decomposition of Actinide™ resin permitting the routine application of this resin as a preconcentrator. Although the classical Fe(OH)3 precipitation is effective in scavenging actinides, the need for careful handling to recover the sticky precipitate makes the new method much more attractive. The known difficulty of decomposing Actinide™ resin, which is required prior to the subsequent separation of adsorbed actinides, is innovatively overcome by using a borate fusion attack. This procedure effectively solves the normally encountered problem by safely and speedily decomposing the resin in minutes rather than hours. The alternative and apparently simpler technique of direct ashing of the Actinide™ resin is not used since it leads to a residue that is not readily leachable. The new technique has been incorporated into a procedure for the isolation of Pu and U from natural water samples and their subsequent quantification by alpha spectrometry. The efficiency of loading of the elements onto Actinide™ resin has been tested using both batch and column-based approaches. The integrated method involving Actinide™ resin preconcentration, borate fusion, anion and UTEVA chromatography and electrodeposition provides limits of detection of 0.001 Bq L−1 and chemical recoveries in excess of 80% from groundwater and seawater samples as large as 5 L. Comparative data, presented for the analysis of independently analysed river, borehole and surface run-off waters using both the described procedure and other competing techniques, show very good agreement.

A novel extraction chromatographic resin based on diisobutyl ketone has been developed for the isolation of 55Fe. This material has been used in conjunction with a dimethylglyoxime-based resin for the sequential separation of 55Fe and 63Ni and isolation of these radionuclides from associated contaminants. The preparation and characterisation of these resins is described along with an assessment of their performance for the isolation of 55Fe and 63Ni from a mixture of nuclear activation products. In addition, a refined approach for the measurement of these nuclides by liquid scintillation counting is discussed. The findings of these studies have been combined to develop a robust procedure for the analysis of 55Fe and 63Ni in reactor effluents which is now the preferred method for a number of UK analytical laboratories.

A new method for analyzing gold at ultralow concentrations (10 pg/g) in geological samples has been developed involving HF-aqua regia acid digestion, chromatographic separation of Au from matrix elements using DIBK supported on an inert resin, and analysis by inductively coupled plasma-mass spectrometry (ICPMS). This method has an analytical detection limit of 2 parts per trillion (pg/g), significantly lower than most routinely used methods developed for analysis of ore samples with Au concentrations considerably higher than average crustal abundance ( approximately 2 ng/g). Such methods commonly have detection limits in the low nanogram per gram range. Many areas of geological research including ore genesis, crustal mobility and redistribution, planetary differentiation, and plume volcanism require quantitative analysis of geological materials with much lower Au concentrations. We present a rapid, easy to use method where Au is separated from matrix elements onto extractant primed chromatographic resin and analyzed by quadrupole ICPMS. The method is suitable for the relatively rapid analysis of a large number of samples and is reliable over a wide range of concentrations from picogram to microgram per gram level. Analysis of four different geostandards, GXR1, GXR4, CH-3, and SARM 7, yields concentrations within error of the published concentrations with accuracies of95%.

The UKAEA Winfrith site is in a phase of accelerated decommissioning and de-licensing which will generate significant volumes of metal wastes some of which may be suitable for disposal as exempt wastes. If contamination is present, it is often confined within the surface layers of the metal. The UKAEA Winfrith site operates a shot-blast facility (WACM) that removes paint and surface contamination from low carbon steel enabling surface contaminated painted metal to be processed and therefore certified as exempt. A study was conducted to determine whether tritium (as tritiated water vapour) has penetrated into the metal to levels exceeding the Radioactive Substances Act (1993), Substances of Low Activity (SoLA) Exemption Order criteria, and whether processing via the WACM removes sufficient tritium contamination that the SoLA Exemption Order criteria can be met. The results of sampling and analysis show that the tritium is mainly held in the paint or outer 40 microm layer of the metal and that processing through the WACM removes these layers along with sufficient tritium to meet the SoLA Exemption Order criteria.

Sector-field multi-collector inductively coupled plasma mass spectrometers, commonly referred to as MC-ICP-MS, can now be fitted with multiple ion counting detectors in tandem with the array of Faraday detectors. In this paper, for the first time, we utilise such an array to measure plutonium isotopes. The chief advantage of multiple ion counting is that it obviates the need to cycle a number of small ion beams through a single collector, and hence increases the efficiency of ion beam usage. This increase in efficiency, combined with the elimination of effects produced by ion beam instability, makes multi-channel analysis an ideal method for low-level plutonium isotope analysis. Mass bias and inter-detector bias can be corrected using an external standard solution, which can be uranium or plutonium based. Using minimised analytical times and desolvating nebulisation, 240Pu/239Pu can be reproduced to better than 3% 2s with less than 10 fg of Pu.

Plutonium and uranium isotope ratios can be used to differentiate the sources of nuclear contamination from nuclear weapon establishments (Environ. Sci. Technol. 34 (2000) 4496; Internal Report for AWRE Aldermaston, UK (1961)), weapon fallout (Geochim. Cosmochim. Acta 51 (1987) 2623; Earth Planet. Sci. Lett. 63 (1983) 202; Earth Planet. Sci. Lett. 22 (1974) 111; Geochim. Cosmochim. Acta 64 (2000) 989), reprocessing plants, reactor or satellite accidents (Science 105 (1979) 583; Science 238 (1987) 512) and in addition they provide markers for post-1952 geochronology of environmental systems. A good record of plutonium and uranium isotope ratios of the background resulting from atmospheric nuclear testing is essential for source characterisation studies. Using recently developed mass spectrometric techniques (J. Anal. At. Spectrom. 16 (2001) 279) we present here the first complete records between 1952 and the present day of northern temperate latitude 240Pu/239Pu and 238U/235U atom ratios for atmospheric deposition. Such information was not derived directly during the period of atmospheric testing because suitable mass spectrometric capability was not available. The currently derived records are based on an annual herbage archive and a core from an Alpine glacier. These studies reveal hitherto unseen fluctuations in the 238U/235U atmospheric fallout record, some of which are directly related to nuclear testing. In addition, they also provide the first evidence that plutonium contamination originating from Nevada Desert atmospheric weapon tests in 1952 and 1953 extended eastwards as far as northwestern Europe. The results presented here demonstrate that we now have the capability to detect and precisely identify sources of plutonium in the environment with implications for the development of atmospheric transport models, recent geochronology and environmental studies.

Over the past five decades, authorized low-level discharges from coastal nuclear facilities have released significant quantities of artificial radionuclides into the marine environment. In northwest Europe, the majority of the total discharge has derived from nuclear reprocessing activities at Sellafield in the United Kingdom and COGEMA-La Hague in France. At the Sellafield site, a significant amount of the discharges has been trapped in offshore fine sediment deposits, and notably in local coastal and estuarine sediments, and much research has been focused on understanding the distribution, accumulation, and reworking of long-lived radionuclides in these deposits. In contrast, there are few high-resolution published data on the vertical distribution of radionuclides in fine-grained estuarine sediments near, and downstream of, COGEMA-La Hague. This paper therefore examines the vertical distribution of a range of anthropogenic radionuclides in dated salt marsh cores from two estuaries, one adjacent to, and the other downstream of, the COGEMA-La Hague discharge point (the Havre de Carteret at Barneville-Carteret and the Baie de Somme, respectively). The radionuclides examined show a vertical distribution which predominantly reflects variations in input from COGEMA-La Hague (albeit much more clearly at Barneville-Carteret than at the Baie de Somme site), and Pu isotopic ratios are consistent with a La Hague, rather than weapons' fallout, source. Because of sediment mixing, the marshes apparently retain an integrated record of the La Hague discharges, rather than an exact reproduction of the discharge history. Sorption of radionuclides increases in the order 90Sr < 137Cs < 60Co < 239,240Pu, which is consistent with Kd values reported in the literature. In general, the radionuclide activities observed at the sites studied are low (particularly in comparison with salt marsh sediments near the Sellafield facility), but are similar to those found in areas of fine sedimentation in the central Channel. These marshes are not major sinks for discharged reprocessing wastes.

The adsorption of a number of radioactive ions from solution by a strongly magnetic iron sulfide material was studied. The material was produced by sulfate-reducing bacteria in a novel bioreactor. The uptake was rapid and loading on the adsorbent was high due to the high surface area of the adsorbent and because many of the ions were chemisorbed. The structural properties were examined with high-resolution imaging and electron diffraction by transmission electron microscopy. The adsorbent surface area was determined to be 400–500m2/g by adsorption of heavy metals, the magnetic properties, neutron scattering, and transmission electron microscopy. The adsorption of a number of radionuclides was examined at considerably lower concentration than in previous work with these adsorbent materials. A number of ions studied are of interest to the nuclear industry, particularly the pertechnetate ion (TcO4 −). 99Tc is a radionuclide thought to determine the long-term environmental impact of the nuclear fuel cycle bec...

Americium-241 and plutonium determinations will become of greater importance over the coming decades as 137Cs and 241Pu decay. The impact of 137Cs on environmental chronology has been great, but its potency is waning as it decays and diffuses. Having 241Am and Pu as unequivocal markers for the 1963 weapon fallout maximum is important for short time scale environmental work, but a fast and reliable procedure is required for their separation. The developed method described here begins by digesting samples using a lithium borate fusion although an aqua regia leachate is also effective in many instances. Isolation of the Am and Pu is then achieved using a combination of extraction chromatography and conventional anion exchange chromatography. The whole procedure has been optimized, validated, and assessed for safety. The straightforwardness of this technique permits the analysis of large numbers of samples and makes 241Am-based techniques for high-resolution sediment accumulation rate studies attractive. In addition, the technique can be employed for the sequential measurement of Pu and Am in environmental surveillance programs, potentially reducing analytical costs and turnround times.

Significant quantities of 55Fe, an activation product of stable iron, have been released into the environment following the atmospheric testing of nuclear weapons (mainly in the 1950s and 1960s) as well as through authorized discharges of radioactivity from nuclear power and reprocessing sites. Although some studies have been performed on the behavior of weapons' fallout-derived 55Fe in the environment and subsequent impact on humans, little has been published on the behavior of 55Fe released as a point source discharge from nuclear sites. This study presents data on the concentration and temporal variation of 55Fe in fucoid seaweeds, shellfish, crab, and lobster collected from Weymouth Bay and adjacent coastal areas, southern England. These areas have received authorized discharges of radionuclides originating from the operation of a now-decommissioned steam-generating, heavy water-type reactor at AEE Winfrith. The highest activities of 55Fe are found associated with marine sediments collected near the discharge pipeline and a rapid decline occurs away from the pipeline. This is consistent with rapid sorption of 55Fe by the sediment, and the data show there is only limited reworking and remobilization. Activities of 55Fe in biota generally decreased over time, due to a reduction in the amount of 55Fe discharged. The variation of 55Fe activity, revealed from the monthly sampling of seaweed, does not reflect the short-term fluctuations seen in the patterns of discharged 55Fe activity. Although discharges of 55Fe from AEE Winfrith exceeded other radionuclides, the radiological impact on local seafood consumers is considerably less than for other key radionuclides such as 60Co and 65Zn but of comparable magnitude to the global average population dose arising from fallout-derived 55Fe.

Plutonium isotope ratios have been determined on solutions with concentrations covering four orders of magnitude, 100 fg ml−1 to 600 pg ml−1, using multicollector ICP-MS (Micromass IsoProbe). Discrimination between different sources of anthropogenic plutonium requires both precise and accurate isotope ratio determination at environmental concentration levels. To achieve a precision of better than 1% at these concentrations, we have developed an analytical procedure in which an equal atom 236U–233U double spike was added to solutions to correct for drift in signal intensity between peak jump sequences. This double spike is also used to correct for instrument mass bias during each ratio determination. Analyses were made on about 1 ml of solution which, in the case of a 100 fg ml−1 sample with a fallout 240Pu/239Pu of about 0.18, means a 239Pu content of about 80 fg in the analyte. 240Pu/239Pu can be reproducibly measured to within 1.4% (2s) at 100 fg ml−1 and better than 0.3% at >3 pg ml−1. Using this same technique we have also successfully measured 242Pu/239Pu with a precision of better than 2% on solutions containing 30 fg of 242Pu and better than 10% with 5 fg of 242Pu.

Radioactive discharges from nuclear facilities are frequently made into the marine environment and their fate during and after cessation of discharges is a matter of interest and concern. This study examines the decline of the radionuclides 60Co and 65Zn along the southern U.K. coast, over the period 1988?1998, following the closure of the steam-generating heavy water (SGHW) reactor at AEA Winfrith, Dorset, UK. 60Co and 65Zn (and other activation products such as 63Ni and 55Fe) were widely dispersed in the marine environment off the central south coast of England, due to authorized releases from AEA Winfrith. Significant interaction occurred with clay-rich sediments and biota. A general exponential decline in 60Co activities (and in 65Zn activity) is found in intertidal mudflat sediments, seaweed and marine fauna in different areas along the south coast following closure of the reactor in 1990. Effective half-lives are determined which vary from 1 to 4 years in surface sediments (60Co only), 1?4 years in seaweed and 0.5?2.5 years in crustaceans, bivalves and molluscs. Physical mixing and bioturbation largely control the rate at which 60Co declines in surface sediments. Both 60Co and 65Zn show a relatively slow rate of decline in seaweed and in marine fauna, showing that even after the virtual cessation of discharge from nuclear facilities, contamination of these organisms may persist for a number of years, albeit at reduced activities. Reasons for this persistence are likely to include absorption of radionuclides from sediment, and release and recycling of radionuclides via breakdown of contaminated organic material.

The paper describes a method for the separation of uranium and plutonium isotopes using anion exchange resin and UTEVA ™ resin in stacked sequential columns for routine analysis of river water and liquid effluent samples. The optimisation of the UTEVA ™ column for separation of U is described and compared with the conventional anion exchange technique for the separation of U from Fe. The stacked anion exchange and UTEVA ™ column configuration facilitates a more rapid and efficient separation of Pu and U and also reduces the quantity of reagents required for the separation.

A straightforward technique involving sub-boiling distillation has been developed for the purification of river and effluent water samples prior to the determination of tritium ( 3 H ) by liquid scintillation analysis. The study evaluates the efficiency of sub-boiling distillation for decontaminating mixed β/γ emitters which could interfere with the tritium determination. The technique effectively purifies tritiated water in aqueous samples from the major contaminating radioisotopes including 22 Na , 54 Mn , 60 Co , 65 Zn , 88 Y , 137 Cs and 155 Eu . However, the technique requires less analyst set-up and supervision time than conventional distillation techniques and larger sample batches can therefore be routinely analysed. Recent improvements to the design of the sub-boiling unit and applications of the unit are also discussed.