3,997 research outputs found

    Gas Concentration Measurements in Underground Waste Storage Tanks

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    Currently over 100 underground tanks at the Hanford facility in eastern Washington state are being used to store high-level radioactive waste. With plans for a long-term nuclear-waste repository in Nevada in place (though not yet approved), one promising use for these underground storage tanks is as a temporary waystation for waste destined for the Nevada repository. However, without a reasonable understanding of the chemical reactions going on within the tanks, transporting waste in and out of the tanks has been deemed to be unsafe. One hazard associated with such storage mechanisms is explosion of flammable gases produced within the tank. Within many of the storage tanks is a sludge layer. This layer, which is a mixture of liquid and solids, contains most of the radioactive material. Radioactive decay and its associated heat can produce several flammable materials within this layer. Two components of particular concern are hydrogen (H2) and nitrous oxide (N2O), since they are highly volatile in the gaseous phase. Though the tanks have either forced or natural convection systems to vent these gases, the possibility of an explosion still exists. Measurements of these gases are taken in several ways. Continuous measurements are taken in the headspace, which is the layer between the tank ceiling and the liquid (supernatant) or sludge layer below. In tanks where a supernatant layer sits atop the sludge layer, there are often rollovers or gas release events (GREs), where a large chunk of sludge, after attaining a certain void fraction, becomes buoyant, rising through the supernatant and releasing its associated gas composition to the headspace. Such changes trigger a sensor, and thus measurements are also taken at that time. Lastly, a retained gas sample (RGS) can be taken from either the supernatant or sludge layer. Such a core sample is quite expensive, but can yield crucial data about the way gases are being produced in the sludge and convected through the supernatant. Unfortunately, the measurements from these three populations do not seem to match. In particular, the ratio r = [N2O]/[H2] varies from population to population. r also varies from tank to tank, but this can more readily be explained in terms of the waste composition of each tank. Since H2 is more volatile than N2O (and since there are more sources of oxygen in the headspace), lower values of r correspond to more hazardous situations. This variance in r is troubling, since we need to be able to explain why certain values of r are lower (and hence more dangerous) in certain areas of the tank. In this report we examine the data from three tanks. We first verify that the differences in r among populations is significant. We then postulate several mechanisms which could explain such a difference

    Transparent Metal-Salt-Filled Polymeric Radiation Shields

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    "COR-RA" (colorless atomic oxygen resistant -- radiation shield) is the name of a transparent polymeric material filled with x-ray-absorbing salts of lead, bismuth, cesium, and thorium. COR-RA is suitable for use in shielding personnel against bremsstrahlung radiation from electron-beam welding and industrial and medical x-ray equipment. In comparison with lead-foil and leaded-glass shields that give equivalent protection against x-rays (see table), COR-RA shields are mechanically more durable. COR-RA absorbs not only x-rays but also neutrons and rays without adverse effects on optical or mechanical performance. The formulation of COR-RA with the most favorable mechanical-durability and optical properties contains 22 weight percent of bismuth to absorb x-rays, plus 45 atomic percent hydrogen for shielding against neutrons

    Build an app and they will come? Lessons learnt from trialling the GetThereBus app in rural communities

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    Acknowledgements The research described here was supported by the award made by the RCUK Digital Economy programme to the dot.rural Digital Economy Hub; award reference: EP/G066051/1.Peer reviewedPostprin

    Recovery capital pathways : modelling the components of recovery wellbeing.

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    In recent years, there has been recognition that recovery is a journey that involves the growth of recovery capital. Thus, recovery capital has become a commonly used term in addiction treatment and research yet its operationalization and measurement has been limited. Due to these limitations, there is little understanding of long-term recovery pathways and their clinical application. We used the data of 546 participants from eight different recovery residences spread across Florida, USA. We calculated internal consistency for recovery capital and wellbeing, then assessed their factor structure via confirmatory factor analysis. The relationships between time, recovery barriers and strengths, wellbeing and recovery capital, as well as the moderating effect of gender, were estimated using structural equations modelling. The proposed model obtained an acceptable fit (χ(2) (141, N=546)=533.642, p<0.001; CMIN/DF=3.785; CFI=0.915; TLI=0.896; RMSEA=0.071). Findings indicate a pathway to recovery capital that involves greater time in residence ('retention'), linked to an increase in meaningful activities and a reduction in barriers to recovery and unmet needs that, in turn, promote recovery capital and positive wellbeing. Gender differences were observed. We tested the pathways to recovery for residents in the recovery housing population. Our results have implications not only for retention as a predictor of sustained recovery and wellbeing but also for the importance of meaningful activities in promoting recovery capital and wellbeing. [Abstract copyright: Copyright © 2017 Elsevier B.V. All rights reserved.

    Sport psychological skills training and psychological well-being in youth athletes

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    In sport, psychological skills training is as important as physical training. Psychological skills training (PST) package programs aim to train a variety of psychological skills simultaneously. While extensively utilized overseas, PST programs are seldomly conducted with South African elite sportspeople and are generally not available to local youth athletes. Furthermore, the impact of PST programs on life and general health and the related components of biological, psychological, social and spiritual well-being has been typically neglected, with research in this regard minimal or non-existent. For example, before this thesis, the impact of PST on the core health component of psychological well-being had not been evaluated, nor had the conceptual and/or empirical relationship between psychological skills and psychological well-being been investigated. Although PST is often conducted individually because of its specific and personal nature, group training should not be overlooked especially in South Africa where communal living is a way of life and community interventions are an important part of health promotion. The value of broad base PST programs is that they train psychological skills as life skills thus aiding overall biopsychosocialculturalspiritual development. With these considerations in mind a triangulated design involving individual, group and community interventions, as well as elite and expert case studies was utilized to evaluate the effectiveness of a PST program and to investigate the relationship between psychological skills and psychological well-being. Results based on quantitative and qualitative outcome and process measurements indicated general improvement in psychological skills, psychological well-being and sporting performance. Psychological skills and psychological well-being were found to be interrelated concepts, with overlapping components. Recommendations for ongoing and future research at individual, group and community level are made.Thesis (DPhil)--University of Pretoria, 2008.Biokinetics, Sport and Leisure Sciencesunrestricte
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