[en] The very high thermal gradient metamorphism in western Namaqualand apparently developed in a compressional setting, requiring a very favourable combination of factors: the convergence of very thin, hot lithosphere, substantial additions of magmatic material, and a relatively short overall time-scale (approx < 30 Ma) for accretion and prograde metamorphism. Field relations and present-day crustal structure are most consistent with basic additions not exceeding 30 km to the lower crust, combined with the emplacement at shallow levels of acid magmas, generated by lower crustal melting. This shallow accretion zone is partly responsible for the P increase recorded in the metasediments. Field and isotopic evidence from eastern Namaqualand for the formation of volcanic arc rocks around 1300 Ma ago, and their accretion onto the Kaapvaal Craton suggests that the tectonic development of the Namaqua Province over much of the mid-Proterozoic can be understood in terms of alternating episodes of extension and convergence at a long-lived active continental margin . 3 figs., 7 refs

[en] Laboratory investigations into the precipitation of uranium from an ion exchange eluate by hydrogen peroxide are presented. Factors affecting the precipitation (pH, ratio of hydrogen peroxide to uranium and temperature) were examined, leading to the production of a yellowcake with higher purity and better handling characteristics than cakes produced by ammonia precipitation techniques. Pilot scale experiments have been carried out to determine the relative filtrability and handling characteristics of ammonium diuranate and uranium peroxide. A brief comparison of the costs of various precipitation methods is also presented

[en] The overall objectives were: to review the mechanisms, implications and consequences of the radioactive contamination of soils, sediments and water sources with an agricultural use following the release and transport of radioactive materials from a deep repository at Sellafield; and to produce illustrative dose calculations for identification of the relative importance of exposure pathways to provide information for MAFF in their independent QA assessment of Nirex proposals. (author)

[en] A retrospective analysis of 85 dogs with hemangiosarcoma (HSA) that underwent complete necropsy, including gross examination of the brain, was conducted. Grossly identifiable intracranial lesions were present in 17 dogs. Twelve of 85 dogs (14.2%) had brain metastases. Four of 85 dogs (4.7%) had hemorrhagic lesions and/or ischemic necrosis without identifiable tumor. One dog had a primary central nervous system tumor. Signs of intracranial disease were present in six of 85 dogs (7.1%) with HSA; four had brain metastases and two had nonneoplastic lesions. Metastases had a propensity for cerebrum and gray matter. Dogs with brain metastases had more widely disseminated disease than dogs without brain metastases (P less than 0.001). Dogs with pulmonary metastases were at greater risk for developing brain metastases than dogs without pulmonary metastases (odds ratio = 8.31). Although thoracic radiography accurately identified ten of 12 dogs (83%) with pulmonary metastases, too few cases were available to assess the applicability/accuracy of thoracic radiography in predicting the presence or absence of brain metastases in dogs with malignancy and signs of intracranial disease

[en] The design of an engineered barrier system (EBS) for the containment of radioactive waste buried at depth incorporates a wide range of decisions based on quantitative engineering science, site specific hydrological information and expert judgement. Even at the concept design and planning stage of the EBS, there may be some key alternatives or choices which, though usually considered from an executive engineering perspective, may have a large impact upon the success of the programme as a whole. Therefore it is of interest to ask open-quotes what are the key attributes?close quotes of the design process from the perspective of those experts working in the perception/communication fields, as well as the supporting research assessments and programmes. This involves the consideration of subjective expert opinions in various disciplines, and the identification of differences in the structure of their cognitive reasoning regarding the EBS. This report describes how a group of experts responded to a range of EBS designs

[en] An experimental program has been carried out by the Australian Atomic Energy Commission to compare the effectiveness of Caro's acid as an alternative oxidant to pyrolusite in the leaching of uranium ores from the Alligator Rivers region of northern Australia. Batch leaching tests on Ranger, Nabarlek, Koongarra and Jabiluka ores showed that uranium extraction was unaffected by choice of oxidant, but that Caro's acid reduced acid requirements by 15-25%. Lime requirements for neutralization of tailings liquors were reduced by 20-30%. The batch studies were extended to a four-stage continuous leaching circuit with a capacity of 400 g ore h^-1. Comparative leaching tests confirmed the reagent savings obtained in the batch tests. Following these encouraging laboratory results, Interox Chemicals Pty Ltd carried out plant trials using Caro's acid. Reagent savings in the mill were similar to, or better than, those obtained in laboratory testwork. The trials also established that Caro's acid has a number of operational advantages over pyrolusite

[en] An experimental program has been carried out by the Australian Atomic Energy Commission to compare the effectiveness of Caro's acid as an alternative oxidant to pyrolusite in the leaching of uranium ores from the Alligator Rivers region of northern Australia. Batch leaching tests on Ranger, Nabarlek, Koongarra and Jabiluka ores showed that uranium extraction was unaffected by choice of oxidant, but that Caro's acid reduced acid requirements by 15 -25%. Lime requirements for neutralization of tailings liquors were reduced by 20 - 30%. The batch studies were extended to a four-stage continuous leaching circuit with a capacity of 400 g ore h^-1. Comparative leaching tests confirmed the reagent savings obtained in the batch tests. Following these encouraging laboratory results, Interox Chemicals Pty Ltd carried out plant trials using Caro's acid. Reagent savings in the mill were similar to, or better than, those obtained in laboratory testwork. The trials also established that Caro's acid has a number of operational advantages over pyrolusite

[en] Laboratory leach tests of Nabarlek uranium ore carried out to compare the effectiveness of Caro's Acid (permonosulphuric acid) as an alternative oxidant to pyrolusite indicated reduced acid consumption in leaching and lime savings in neutralisation of tailings liquors. A plant trial confirmed that significant savings in acid and lime could be achieved and also demonstrated that improved redox potential control was possible

[en] Laboratory leach tests have been carried out to compare the effectiveness of Caro's acid (permonosulphuric acid) as an alternative oxidant to pyrolusite in the leaching of uranium ores. Results demonstrated that Caro's acid reduced acid consumption in leaching and the time required for neutralisation of tailings liquor. The uranium extraction was unaffected by choice of oxidant. A plant trial confirmed that significant savings in acid and lime usage can be achieved under plant conditions. Plant operations also demonstrated that Caro's acid has a number of significant operating advantages over pyrolusite. Queensland Mines Ltd. have recently decided to convert their leaching process from pyrolusite to Caro's acid

[en] Pyrolusite (manganese dioxide) was originally chosen as the oxidant at the Nabarlek Mill in northern Australia. Subsequent laboratory and plant trial investigations showed that if Caro's acid were to replace pyrolusite, acid consumption in the leaching circuit could be reduced by 15-20% for the same uranium extraction. Lime required to neutralize the tailings/raffinate slurry could also be similarly reduced. A Caro's acid generator was commissioned at Nabarlek in April 1983. Caro's acid is manufactured at the mill site by reaction of hydrogen peroxide with concentrated sulphuric acid. This installation is the first commercial utilization of Caro's acid in uranium processing. The system has operated successfully for three months and reagent savings have resulted in a reduction in operating costs of greater than $3.t^-1 ore processed. (author)