Cast Stone Oxidation Front Evaluation: Preliminary Results For Samples Exposed To Moist Air

The rate of oxidation is important to the long-term performance of reducing salt waste forms because the solubility of some contaminants, e.g., technetium, is a function of oxidation state. TcO{sub 4}{sup −} in the salt solution is reduced to Tc(IV) and has been shown to react with ingredients in the waste form to precipitate low solubility sulfide and/or oxide phases. Upon exposure to oxygen, the compounds containing Tc(IV) oxidize to the pertechnetate ion, Tc(VII)O{sub 4}{sup −}, which is very soluble. Consequently the rate of technetium oxidation front advancement into a monolith and the technetium leaching profile as a function of depth from an exposed surface are important to waste form performance and ground water concentration predictions. An approach for measuring contaminant oxidation rate (effective contaminant specific oxidation rate) based on leaching of select contaminants of concern is described in this report. In addition, the relationship between reduction capacity and contaminant oxidation is addressed. Chromate (Cr(VI) was used as a non-radioactive surrogate for pertechnetate, Tc(VII), in Cast Stone samples prepared with 5 M Simulant. Cast Stone spiked with pertechnetate was also prepared and tested. Depth discrete subsamples spiked with Cr were cut from Cast Stone exposed to Savannah River Site (SRS) outdoor ambient temperature fluctuations and moist air. Depth discrete subsamples spiked with Tc-99 were cut from Cast Stone exposed to laboratory ambient temperature fluctuations and moist air. Similar conditions are expected to be encountered in the Cast Stone curing container. The leachability of Cr and Tc-99 and the reduction capacities, measured by the Angus-Glasser method, were determined for each subsample as a function of depth from the exposed surface. The results obtained to date were focused on continued method development and are preliminary and apply to the sample composition and curing / exposure conditions described in this report. The Cr oxidation front (depth to which soluble Cr was detected) for the Cast Stone sample exposed for 68 days to ambient outdoor temperatures and humid air (total age of sample was 131 days) was determined to be about 35 mm below the top sample surface exposed. The Tc oxidation front, depth at which Tc was insoluble, was not determined. Interpretation of the results indicates that the oxidation front is at least 38 mm below the exposed surface. The sample used for this measurement was exposed to ambient laboratory conditions and humid air for 50 days. The total age of the sample was 98 days. Technetium appears to be more easily oxidized than Cr in the Cast Stone matrix. The oxidized forms of Tc and Cr are soluble and therefore leachable. Longer exposure times are required for both the Cr and Tc spiked samples to better interpret the rate of oxidation. Tc spiked subsamples need to be taken further from the exposed surface to better define and interpret the leachable Tc profile. Finally Tc(VII) reduction to Tc(IV) appears to occur relatively fast. Results demonstrated that about 95 percent of the Tc(VII) was reduced to Tc(IV) during the setting and very early stage setting for a Cast Stone sample cured 10 days. Additional testing at longer curing times is required to determine whether additional time is required to reduce 100 % of the Tc(VII) in Cast Stone or whether the Tc loading exceeded the ability of the waste form to reduce 100 % of the Tc(VII). Additional testing is required for samples cured for longer times. Depth discrete subsampling in a nitrogen glove box is also required to determine whether the 5 percent Tc extracted from the subsamples was the result of the sampling process which took place in air. Reduction capacity measurements (per the Angus-Glasser method) performed on depth discrete samples could not be correlated with the amount of chromium or technetium leached from the depth discrete subsamples or with the oxidation front inferred from soluble chromium and technetium (i.e., effective Cr and Tc oxidation fronts). Residual reduction capacity in the oxidized region of the test samples indicates that the remaining reduction capacity is not effective in re-reducing Cr(VI) or Tc(VII) in the presence of oxygen. Depth discrete sampling and leaching is a useful for evaluating Cast Stone and other chemically reducing waste forms containing ground granulated blast furnace slag (GGBFS) or other reduction / sequestration reagents to control redox sensitive contaminant chemistry and leachability in the near surface disposal environment. Based on results presented in this report, reduction capacity measured by the Angus-Glasser Ce(IV) method is not an appropriate or meaningful parameter for determining or predicting Tc and Cr oxidation / retentions, speciation, or solubilities in cementitious materials such as Cast Stone. A model for predicting Tc(IV) oxidation to soluble Tc(VII) should consider the waste form porosity (pathway for oxygen ingress), oxygen source, and the contaminant specific oxidation rates and oxidation fronts. Depth discrete sampling of materials exposed to realistic conditions in combination with short term leaching of crushed samples has potential for advancing the understanding of factors influencing performance. This information can be used to support conceptual model development

Long pulse excitation thermographic non-destructive evaluation

A comprehensive analysis of the defect detection performance of long pulse excitation thermographic NDE is presented. An analytical procedure for predicting the thermal image contrasts of defects of specified size and depth is developed and validated by extensive experimental studies of test pieces having a wide range of thermal properties. Results obtained using long pulse (~5 s) excitation are compared with those obtained using traditional flash excitation. The conditions necessary for the success of the long pulse method are explained and illustrated by both modelling and experimental results. Practical advantages of long pulse excitation are discussed

Multi-scale analysis and validation of the Envisat MERIS Terrestrial Chlorophyll Index (MTCI) in woodland

Satellite remote sensing can be used to estimate and monitor the chlorophyll content of vegetation canopies which are a key and dynamic component of global terrestrial ecosystems. The red-edge algorithm can be used to estimate chlorophyll content from remotely sensed data but is unsuitable for use with most satellite sensor imagery. To overcome this problem, the new Envisat MERIS Terrestrial Chlorophyll index (MTCI) has been developed. It is the only operational satellite chlorophyll index and MTCI data are available as a Level 2 product from the European Space Agency. However, there is a need to ‘validate’ the MTCI over a wide range of environmental conditions. This paper reports on research that attempts to validate the MTCI using Compact Airborne Spectrographic Imager (CASI) imagery and ground data of chlorophyll content. The study site was predominantly woodland in the south of England (New Forest National Park) and had a wide range of chlorophyll contents. A transfer function derived from CASI data was used to produce a reference map of chlorophyll content, when aggregated it was compared to MERIS MTCI data and used to derive the MTCI – chlorophyll content relationship (R squared = 0.56)

Website design: Technical, social and medical issues for self-reporting by elderly patients

There is growing interest in the use of the Internet for interacting with patients, both in terms of healthcare information provision and information gathering. In this paper we examine the issues in designing healthcare websites for elderly users. In particular this paper uses a year-long case study of the development of a web-based system for self-reporting of symptoms and quality of life with a view to examine the issues relating to website design for elderly users. The issues identified included the technical, social and medical aspects of website design for elderly users. The web-based system developed was based upon the EQ5D health-status questionnaire, a commonly used tool for patient self-reporting of quality of life, and the more specific CROQ (coronary revascularisation outcome questionnaire) questionnaire. Currently self-reporting is generally administered in the form of paper-based questionnaires to be completed in the out-patient clinic, or at home. There are a variety of issues relating to elderly users that imply that websites for elderly patients may involve different design considerations to other types of websites

DISTRIBUTION COEFICIENTS (KD) GENERATED FROM A CORE SAMPLE COLLECTED FROM THE SALTSTONE DISPOSAL FACILITY

Core samples originating from Vault 4, Cell E of the Saltstone Disposal Facility (SDF) were collected in September of 2008 (Hansen and Crawford 2009, Smith 2008) and sent to SRNL to measure chemical and physical properties of the material including visual uniformity, mineralogy, microstructure, density, porosity, distribution coefficients (K{sub d}), and chemical composition. Some data from these experiments have been reported (Cozzi and Duncan 2010). In this study, leaching experiments were conducted with a single core sample under conditions that are representative of saltstone performance. In separate experiments, reducing and oxidizing environments were targeted to obtain solubility and Kd values from the measurable species identified in the solid and aqueous leachate. This study was designed to provide insight into how readily species immobilized in saltstone will leach from the saltstone under oxidizing conditions simulating the edge of a saltstone monolith and under reducing conditions, targeting conditions within the saltstone monolith. Core samples were taken from saltstone poured in December of 2007 giving a cure time of nine months in the cell and a total of thirty months before leaching experiments began in June 2010. The saltstone from Vault 4, Cell E is comprised of blast furnace slag, class F fly ash, portland cement, and Deliquification, Dissolution, and Adjustment (DDA) Batch 2 salt solution. The salt solution was previously analyzed from a sample of Tank 50 salt solution and characterized in the 4QCY07 Waste Acceptance Criteria (WAC) report (Zeigler and Bibler 2009). Subsequent to Tank 50 analysis, additional solution was added to the tank solution from the Effluent Treatment Project as well as from inleakage from Tank 50 pump bearings (Cozzi and Duncan 2010). Core samples were taken from three locations and at three depths at each location using a two-inch diameter concrete coring bit (1-1, 1-2, 1-3; 2-1, 2-2, 2-3; 3-1, 3-2, 3-3) (Hansen and Crawford 2009). Leaching experiments were conducted with a section of core sample 3-2. All cores from location 3 were drilled without using water. Core sample 3-2 was drilled from approximately six inches to a depth of approximately 13 inches. Approximately six inches of the core was removed but it broke into two pieces during removal from the bit. At the time of drilling, core material appeared olive green in color (Smith 2008). The fact that the samples were cored as olive green and were received after storage with a gray outer layer is indicative that some oxidation had occurred prior to leaching studies

Forensic investigation of social networking applications

Social networking applications such as Facebook, Twitter and Linkedin may be involved in instances of misuse such as copyright infringement, data protection violations, defamation, identity theft, harassment, and dissemination of confidential information and malware that can affect both organizations and individuals. In this paper we examine the computer forensic process of obtaining digital evidence from social networking applications and the legal aspects of such. Currently there do not appear to be commonly available guidelines for organizations aimed specifically at the computer forensic process of investigation of social networking applications

Initial teacher training to promote health and well-being in schools – a systematic review of effectiveness and barriers and facilitators

Objectives: to conduct a systematic review of effectiveness, and barriers and facilitators, of initial teacher training to promote health and wellbeing in schools. Design: systematic review of the literature Method: a total of 20 bibliographic databases were searched, including Medline, Embase, and the Social Science Citation Index. Studies were included if they reported research into the processes and/or outcomes of initial (pre?service) teacher training to promote health. Results: a total of 20 studies met the inclusion criteria, mainly from the UK and Australia. Twelve studies assessed outcomes, commonly using uncontrolled before and after assessment designs. Sixteen studies evaluated the processes of training. Training was diverse in terms of content, format and health topics. The studies demonstrated short?term increases in trainee teachers’ factual knowledge of health issues, a general increase in teachers’ confidence to teach about health and to identify and help children with specific health issues. There was an increase in teachers’ positive beliefs about their role in promoting children’s health. None of the studies assessed changes in pupil outcomes. The training was generally considered acceptable and adequate by trainee teachers. However, some of trainees felt that they still lacked knowledge and confidence to address sensitive health issues on entering teaching practice. Conclusion: this systematic review identified some evidence for the effectiveness of teacher training for health, and highlighted factors which facilitate and inhibit effective training. Further evaluation, using controlled trial designs with long?term follow?up of teacher and pupil outcomes, may enable teachers to effectively address the health and education needs of school pupils <br/