The design and synthesis of selective adsorbents for nuclear fission product removal using continuous chromatography: A new concept in nuclear reprocessing and waste management

The current nuclear fuel reprocessing technique -PUREX -has remained in operation, unchallenged for over 50 years. The underlying reason for this is that development of alternative processes have not achieved the required criteria. The PUREX process hashowever, some inherent challenges that hinder its efficiency for separating uranium and plutonium from other radionuclides in spent nuclear fuel liquors which are discussed within this thesis. In addition, the PUREX process produces High Level Waste (HLW)which contains both relatively short lived beta/gamma emitters (cesium and strontium) and longer lived minor actinides (neptunium and americium) which ultimately present waste disposal challenges. An Alternative Reprocessing Technique (ART) is described for efficient separation of radionuclides from spent fuel dissolver liquors which could potentially eliminate High Level Waste and enhance the efficiency –or even replace -the PUREX process. A highly selective phosphate (ammonium molybdophosphate, AMP) has been shown to remove cesium for nitric acid liquors but not containing greater concentrations of uranium and/or plutonium. This research is split into 3 main parts; [1] optimisation of the synthesis of AMP/PAN (polyacrylonitrile) to maximise ion exchange performance; [2] focus on synthesis and development of mixed metal phosphates/polyacrylonitrile composites for strontium adsorption and [3] scoping the capabilities of a Simulated Moving Bed Chromatography technique to be applied to ART for the downstream extraction of fission products from spent fuel dissolver liquors following the removal of cesium. Previously studies of cesium and strontium adsorbents for their extraction from HLW were reviewed. These adsorbents are evaluated for their ion exchange performance as a function of selectivity, stability, kinetics and capacity. The outstanding material for cesium extraction from spent fuel dissolver liquors is currently AMP as it displays a high affinity for cesium with high capacities and rapid ion exchange kinetics whilst exhibiting high thermal and radiolytic stability. It can also be encapsulated into a polyacrylonitrile support for synthesis of spherical beads that are more applicable to an industrial process. The preparative routes were varied in order to produce optimised composite spherical beads that had superior selectivity, uptake and kinetics compared with previously prepared material. There is a wide library of selective strontium adsorbent materials but do not possess all the characteristics required for applications in nuclear reprocessing. This study was therefore designed to address the preparation and development of novel highly selective materials that could be used in ART and to evaluate Simulated Moving Bed Chromatography for radionuclide extraction. A selection of mixed metal phosphate powders was provided, untested for their strontium uptake capabilities. The powders were encapsulated in PAN to mimic the AMP/PAN composite in the hope they would display comparatively uptake capacities and kinetics for strontium. Initial results of AMP/PAN synthesis optimisation revealed that beads of 1-2mm in diameter exhibited limited uptake in 1 M and 3 M HNO3with a cesium concentration of 5 mM. Smaller beads <1 mm in diameter produced using anew bead preparative technique displayed an increase in cesium uptake by almost 10 fold from a similar concentration cesium solution. In addition, the selectivity of cesium was also high in the presence of a large excess of ceriumions. The uptake of cesium when the oxidation state of cerium was increased to 4+, was noticeably lower but reasons for this are inconclusive as of yet. The results were compared to previously produced AMP/PAN composites. The modified AMP/PAN beads showed evidence of more internal voids, but less ordered channels and greater surface area. These characteristics resulted in a significant, greater cesium uptake. A series of untested mixed metal phosphate powders synthesised via a fast flow synthesis were selected for their uptake capabilities for strontium. Most of the adsorbents exhibited rapid uptake kinetics with near complete adsorption of strontium in pH values of ~5. They were subsequently encapsulated into a polyacrylonitrile matrix to produce spherical beads ~0.5 –1mm in diameter and re-tested for their ion exchange performance. Kinetics results were constant with the starting powders but capacities and Kd values decreased. Their stability in acidic media was also limited. Various commercial Purolite resins were investigated using an isocratic SMBC technique using a multi-ion feed solution (Zr, Mo, Ce). Initial results were compared to previous single column work performed with the same resins. The elution of the different ions displayed some very distinctive differences to single column results due to the different underlying fundamentals of SMB. Ce was used in high excess as a uranium simulant and presented competitive adsorption behaviours. These preliminary studies were used to gain an initial insight to its potential use in spent fuel nuclear reprocessing

Fact versus Conjecture: Exploring Levels of Evidence in the Context of Patient Safety and Care Quality

Evidence-based medicine (EBM) can be defined as the integration of optimized clinical judgment, patient values, and available evidence. It is a philosophical approach to making the best possible clinical decisions for individual patients. Based on objective evaluation and categorization of methodological design and data quality, all existing literature can be organized according to a hierarchy of “evidence quality” that helps determine the applicability and value of scientific findings in terms of clinical implementation and the potential to change existing patterns of practice. In terms of general categorization of scientific impact, randomized controlled trials (RCTs) are placed on top of the hierarchy, followed by systematic reviews of randomized controlled trials (RCTs), quasi-randomized designs, observational studies including retrospective case series, and finally case reports and expert opinion. Each study design is susceptible to certain limitations and biases, highlighting the importance of both clinical and scientific acumen of the interpreting provider. Such approach is critical to determining the value and the applicability of study recommendations in everyday practice. Evidence-based practice (EBP) has become one of the fundamental components of modern medicine and plays an indispensible role in the development (and improvement) of patient care and safety worldwide. Furthermore, organizations that create guidelines and policies for the management of specific conditions, often base the content and strength of their recommendations on the quality of evidence available to expert decision-makers. Therefore, understanding the “state of the science” upon which those recommendations are based will help guide the medical practitioner on “if, when and how” to apply evidence-based guidelines in his or her everyday medical or surgical practice. This chapter focuses on clinically relevant application of levels of scientific evidence (LSE) and the corresponding levels of clinical recommendation (LCR) in the context of care quality and safety

A genome-wide association study identifies risk alleles in plasminogen and P4HA2 associated with giant cell arteritis

Giant cell arteritis (GCA) is the most common form of vasculitis in individuals older than 50 years in Western countries. To shed light onto the genetic background influencing susceptibility for GCA, we performed a genome-wide association screening in a well-powered study cohort. After imputation, 1,844,133 genetic variants were analysed in 2,134 cases and 9,125 unaffected controls from ten independent populations of European ancestry. Our data confirmed HLA class II as the strongest associated region (independent signals: rs9268905, P = 1.94E-54, per-allele OR = 1.79; and rs9275592, P = 1.14E-40, OR = 2.08). Additionally, PLG and P4HA2 were identified as GCA risk genes at the genome-wide level of significance (rs4252134, P = 1.23E-10, OR = 1.28; and rs128738, P = 4.60E-09, OR = 1.32, respectively). Interestingly, we observed that the association peaks overlapped with different regulatory elements related to cell types and tissues involved in the pathophysiology of GCA. PLG and P4HA2 are involved in vascular remodelling and angiogenesis, suggesting a high relevance of these processes for the pathogenic mechanisms underlying this type of vasculitis

Multiple novel prostate cancer susceptibility signals identified by fine-mapping of known risk loci among Europeans

Genome-wide association studies (GWAS) have identified numerous common prostate cancer (PrCa) susceptibility loci. We have fine-mapped 64 GWAS regions known at the conclusion of the iCOGS study using large-scale genotyping and imputation in 25 723 PrCa cases and 26 274 controls of European ancestry. We detected evidence for multiple independent signals at 16 regions, 12 of which contained additional newly identified significant associations. A single signal comprising a spectrum of correlated variation was observed at 39 regions; 35 of which are now described by a novel more significantly associated lead SNP, while the originally reported variant remained as the lead SNP only in 4 regions. We also confirmed two association signals in Europeans that had been previously reported only in East-Asian GWAS. Based on statistical evidence and linkage disequilibrium (LD) structure, we have curated and narrowed down the list of the most likely candidate causal variants for each region. Functional annotation using data from ENCODE filtered for PrCa cell lines and eQTL analysis demonstrated significant enrichment for overlap with bio-features within this set. By incorporating the novel risk variants identified here alongside the refined data for existing association signals, we estimate that these loci now explain ∼38.9% of the familial relative risk of PrCa, an 8.9% improvement over the previously reported GWAS tag SNPs. This suggests that a significant fraction of the heritability of PrCa may have been hidden during the discovery phase of GWAS, in particular due to the presence of multiple independent signals within the same regio

The Effect of Gamma Irradiation on the Ion Exchange Properties of Caesium-Selective Ammonium Phosphomolybdate-Polyacrylonitrile (AMP-PAN) Composites under Spent Fuel Recycling Conditions

The caesium radioisotopes 134Cs, 135Cs, and 137Cs are highly problematic medium-lived species produced during nuclear fission, due to their high radioactivity and environmental mobility. While many ion exchange materials can readily isolate Cs+ ions from neutral or basic aqueous solutions, only ammonium phosphomolybdate (AMP) functions effectively in acidic conditions, removing caesium even down to trace levels. Composites of AMP in a porous polymeric support such as polyacrylonitrile (PAN) can be used to selectively remove Cs+ ions from acidic aqueous decontamination liquors as well as other liquid wastes, and are promising for the isolation of Cs+ isotopes in spent fuel reprocessing. While both AMP and PAN have demonstrable acid stability, and PAN has known resistance to gamma radiation, AMP-PAN composites have received only a limited analysis of their physiochemical and ion exchange performance following irradiation. In this publication, we explore the effect of high levels of gamma irradiation on the ion exchange properties of AMP and AMP-PAN as a Cs+-selective adsorbent under spent fuel dissolver liquor concentrations and acidity. We demonstrate no significant reduction in performance with respect to uptake kinetics or capacity upon irradiation, abiding by the same absorption mechanism observed in the established literature

Removal of Cesium from Simulated Spent Fuel Dissolver Liquor

With a resurgence of the nuclear industry’s fortunes, waste management will be an even greater consideration; reducing wastes, better segregation and treatment that lower the impact on waste storage facilities and repositories, in particular geological repositories will help the sustainability of the industry. We at the University of Central Lancashire (UCLan) proposed in a previous publication a sequential chromatographic separation process, Alternative Reprocessing Technology (ART) for Fission Products (FPs) and Minor Actinides (MAs) separation from spent fuel dissolver liquor, as an improvement to/replacement for PUREX (Plutonium Uranium Redox Extraction). This publication addresses the removal of one particular fission product, cesium, and its impact on waste management, and down-stream PUREX operations. Although our proposed process is still in its infancy, its impact on the PUREX process could be significant, with major gains in the separation circuit, waste management of High Level Waste (HLW) and subsequently waste disposal to and design of a geological repository. This paper briefly describes; our concept, some preliminary experimental data and why re-classification of the bulk of HLW (High Level Waste) to Intermediate Level Waste (ILW) would be possible

The Effect of Gamma Irradiation on the Physiochemical Properties of Caesium-Selective Ammonium Phosphomolybdate–Polyacrylonitrile (AMP–PAN) Composites

Managing certain by-products of the nuclear fuel cycle, such as the radioactive isotopes of caesium: 134Cs, 135Cs and 137Cs is challenging due to their environmental mobility and radioactivity. While a great many materials can isolate Cs+ ions from neutral or basic aqueous solutions via ion exchange, few of these, with the exception of ammonium phosphomolybdate (AMP), function effectively in acidic media. The use of AMP, and its porous composite in polyacrylonitrile (PAN) for management of Cs radioisotopes in various nuclear wastes have been known for decades and are well studied, yet the effects of radiation on the physiochemical properties of such composites have only received limited attention to date. In a previous publication, we demonstrated that a 100 kGy gamma irradiation dose has negligible effect on the ion exchange performance of AMP and AMP−PAN with respect to capacity or kinetics under the Cs+ concentrations and acidity found in spent nuclear fuel (SNF) recycling. As a continuation of this prior study, in this publication we explore the effects of gamma irradiation on the physiochemical properties of AMP and AMP−PAN using a range of characterisation methods. The effects of the same gamma dose on the oxidation state of Mo in AMP and AMP−PAN, the thermal degradation of both AMP and AMP−PAN, combined with a first study into the high-temperature degradation AMP, are reported. The implications of irradiation, its possible mechanism, the conditions present in SNF recycling, and for the end-of-life disposal or recycling of these materials are also discussed

Effectiveness of Screening and Treatment Approaches for Schistosomiasis and Strongyloidiasis in Newly-Arrived Migrants from Endemic Countries in the EU/EEA: A Systematic Review

We aimed to evaluate the evidence on screening and treatment for two parasitic infections—schistosomiasis and strongyloidiasis—among migrants from endemic countries arriving in the European Union and European Economic Area (EU/EEA). We conducted a systematic search of multiple databases to identify systematic reviews and meta-analyses published between 1 January 1993 and 30 May 2016 presenting evidence on diagnostic and treatment efficacy and cost-effectiveness. We conducted additional systematic search for individual studies published between 2010 and 2017. We assessed the methodological quality of reviews and studies using the AMSTAR, Newcastle–Ottawa Scale and QUADAS-II tools. Study synthesis and assessment of the certainty of the evidence was performed using GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. We included 28 systematic reviews and individual studies in this review. The GRADE certainty of evidence was low for the effectiveness of screening techniques and moderate to high for treatment efficacy. Antibody-detecting serological tests are the most effective screening tests for detection of both schistosomiasis and strongyloidiasis in low-endemicity settings, because they have higher sensitivity than conventional parasitological methods. Short courses of praziquantel and ivermectin were safe and highly effective and cost-effective in treating schistosomiasis and strongyloidiasis, respectively. Economic modelling suggests presumptive single-dose treatment of strongyloidiasis with ivermectin for all migrants is likely cost-effective, but feasibility of this strategy has yet to be demonstrated in clinical studies. The evidence supports screening and treatment for schistosomiasis and strongyloidiasis in migrants from endemic countries, to reduce morbidity and mortality

Inhaled hypertonic saline in infants and toddlers with cystic fibrosis: short-term tolerability, adherence, and safety

Inhaled hypertonic saline (HS) is an attractive agent for chronic maintenance therapy in infants and toddlers with cystic fibrosis (CF) because it improves defective mucociliary clearance. Prior to undertaking a clinical trial of HS efficacy in young children with CF, tolerability, adherence and safety must be established

INHALED HYPERTONIC SALINE IN INFANTS AND CHILDREN LESS THAN SIX YEARS OF AGE WITH CYSTIC FIBROSIS: THE ISIS RANDOMIZED TRIAL

Inhaled hypertonic saline is recommended as therapy for cystic fibrosis (CF) patients 6 years of age and older, but its efficacy has never been evaluated in CF patients <6 years of age