Results 1 - 10 of 121
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[en] Energy absorption build-up factor (EABF) values have been calculated for vital human organs such as brain, heart, kidney, liver, lung, ovary, pancreas, spleen, and tongue, for the photon energy range 0.015–15 MeV and for penetration depths up to 40 mean free paths (mfp). The five-parameter geometric progression (G-P) fitting approximation and ANSI/ANS-6.4.3-1991 (American National Standard) library have been used to calculate EABF. The EABF has been studied as functions of incident photon energy and penetration depth. It is also found that the EABF of human organs significantly change by varying the incident photon energy and the penetration depth. These changes are due to the dominance of different photon interaction processes in different energy regions. (author).
[en] This paper presents the accelerated oxidation and hydriding processes of zirconium alloys (Zircaloy-4 and Zr-2.5%Nb) in connection with testing temperature. The corrosion tests have been performed by autoclaving in demineralized water (pH 6.8-7), at 310 and 350°C and in steam at high temperature (400-600°C) and pressure 10-11MPa. The samples used in the oxidation tests were cut from Zircaloy-4 sheaths and Zr-2.5%Nb pressure tube in the same metallurgical state as the sheaths and pressure tubes of the CANDU-Reactor. On the basis of determinations of weight gains, the corrosion kinetics and the constant values of corrosion kinetics were estimated. They were compared to those obtained at 310°C and 350°C. The thickness of oxides determined on metallographic cross sections was in accordance with the thickness resulting from weight gains. The aspect of oxides and hydrides formed at different temperatures were relieved by metallographic microscopy. By scanning electron microscopy the oxidized surfaces and metal/oxide interfaces of tested samples were examined. The electrochemical impedance spectroscopy determinations obtained on oxides formed at 400, 500 and 600°C relieved differences between oxides depending on formation temperature. The experimental data allowed correlation between the process of accelerated oxidation and hydriding of Zircaloy-4 and Zr-2.5%Nb alloy and testing temperature. (author).
[en] In this work, the Entrance Surface Dose (ESD) free in air was measured to establish baseline patient dose data in AP abdomen projection through implementing quality control (QC) program initiated individually by University Radiation Safety Committee (URSC) at King Abdul-Aziz University Hospital (KAUH)-Saudi Arabia, and Al Demerdash Hospital - Egypt. A total of 9 X-ray machines at KAUH and 7 X-ray machines in Al-Demerdash hospital were analysed according to the protocol for the quality control of conventional X-ray units issued by the association of the Medical Physicists in this study. The ESD to the patient was calculated based on the measurement of the Entrance Surface Exposure (ESE). The study provides useful information for the selection of the optimum value for the exposure parameters that can be used to examine abdomen projection with good image quality. Results have shown wide variations in ESD for AP abdomen X-ray projection. The optimum value for the exposure parameters was determined. Additional measures were applied to reduce the patient dose to reach a dose reduction up to 82 % in KAUH and 25% in Al-Demerdash Hospital keeping the image quality without variation. The calculated ESD had a range from 1.5 to 6.6 mGy with a mean value of 4.3 mGy in KAUH and ranged from 2.5 to 3.5 mGy with a mean value of 3.0 mGy in Egypt. The measured values were compared with those given by the international recommendations. The results obtained by this study will be useful to establish the national guidance levels for each country and they confirmed the need for Quality Assurance propagation both in KSA and Egypt. (author).
[en] This paper estimates the levelised (long-run average) cost of uranium enrichment using discounted cash flow modelling for a range of centrifuge facility scenarios in Australia. The analysis involves adjusting the assumptions used in international comparisons of enrichment costs, for the size of facilities likely required for Australia in order to determine the Separative Work Unit (SWU) costs range. Further modelling is also undertaken in order to consider the impact on the cost of Uranium enrichment when incorporating decommissioning, Uranium hexafluoride (UF6) tails disposal and specific domestic costs. Average costs of international centrifuge facilities are used to determine a broad capital cost range for similar size facilities in Australia. For the purpose of estimating the levelised SWU cost, the higher end of the First-ofa-Kind (FOAK) and Nth-of-a-Kind (NOAK) cost range is selected as Australia lacks the Nuclear Fuel Cycle (NFC) supply chain experience and resources available to the international enrichment facilities that the average cost ranges are based on. While the FOAK levelised cost range for enrichment in Australia is estimated to be significantly above the more advanced nuclear nations, efforts to develop Australia’s nuclear skills and supply chain capabilities may lower the levelised cost range to a level closer to the estimated NOAK range. While this paper estimates the costs of enrichment in Australia relative to international facilities under current conditions, it does not predict the costs of U enrichment at a future point in time when either domestic demand or the international market is sufficient to require such facilities in Australia. (author).
[en] The energy of alpha particles can be estimated by the residual energy (RE) without the need for a surface barrier detector. In the present work, Energy-Range data were used to produce energy-distance curves for alpha particles, in different air pressure conditions. These curves help to calibrate the residual energy of alpha particle incident on the detector after travelling a distance in air. To this end, we introduce a new approach to compute the residual energy for alpha particle. In this approach, the SRIM-2003.26 and Matlab programs were used to calibrate the residual particle energy under different pressure conditions. Results have shown that a good fitting formula for the residual energy as function of air pressure was obtained. There was also observed a good agreement between the calculated values and the experimental published ones, available from the literature. (author).
[en] In the frame of Euratom FP7 NEWLANCER project SWOT (Strengths, Weaknesses, Opportunities and Threats) analysis was performed by each partner from New Member States (NMS) in order to provide valuable input for the development of policies aimed to increase the participation of the NMS in Euratom programmes on the following topics: Generation III and IV systems and materials, Nuclear safety, Radioprotection, Radioactive waste management, and Education and training. The paper presents SWOT analysis for the Nuclear Safety topic performed for Romanian case and taking into consideration national, organizational, and researcher levels. Also the paper includes the description of the process and some methodological aspects. The final objective of SWOT analysis was to propose strategies, in order to reduce the influence of identified negative factors and to enhance the influence of identified positive factors, regarding Romanian participation in Euratom programmes. (author).
[en] The optimal energy resolution of solid state nuclear track detectors (SSNTDs) for low energy alpha particles in vacuum has been studied. CR-39 plastic track detector was employed to resolve the peaks of alpha particles energy when it irradiated under vacuum. It was found that the detector resolution is low dependent on the energy of alpha particle if the irradiation is performed in high vacuum. The energy resolution has been observed to be about 82 keV in the investigated energy range, where the geometrical configuration of the source and detector arrangement was taken into consideration. The results showed that the resolution of CR-39 plastic track detector for alpha particle energy in vacuum increases by three folds compared to that in air. Results of the present work are discussed within the framework of alpha particle interaction with track detector. (author).
[en] In order to provide an insight into the conditions for cracking of steels T91 and 15-15Ti in Heavy Liquid Metals (HLM), mechanical testing of various specimens in contact with leadbismuth eutectic (LBE) was carried out. Constant Extension Rate Tensile (CERT) tests were performed with flat tapered specimens in LBE at 300°C. When steels are in contact with HLM, the Liquid Metal Embrittlement (LME) occurs. The tapered specimens were used in order to evaluate the threshold stress of the crack initiation in LBE. Under these experimental conditions T91 steel showed a tendency to crack initiation. On the other hand, the austenitic 15-15Ti steel was not affected by the environment. However, even in the case of the steel T91, experiments showed that the crack initiation is not leading to a brittle failure and that LME crack do not occur before the maximum load point (UTS), which confirms that LME develops well beyond design loading conditions (require plastic deformation). (author)
[en] Zirconium chemical states have been assessed using X-ray photoelectron spectroscopy (XPS) measurements on Zy-4 fuel cladding tube hydrided at 96 ppm in order to explore the surface chemical modifications. In-depth chemical profiling reveals an increasing zirconium hydride content from 1.9% to 3.0% due to a decreased ubiquitous carbon surface contaminant. Additionally, the diminishing OH groups concentration was successfully associated with the decreasing ZrOx(OH)y chemical state content, from 98.1% to 76.7%, respectively, suggesting a depleted moisture amount with depth. Furthermore, by depth profiling the surface for 30s, the zirconium fully oxidized (ZrO2) was highlighted indicating the presence of the passivating oxide layer.(author)
[en] Scarce uranium resources stimulate interest in U recovery from secondary resources as potential raw materials. Industrial wastes and by-products, and phosphate rocks were considered as a source of uranium in these studies. Two types of Polish industrial wastes: flotation tailings from the copper industry, phosphogypsum from the fertilizer industry and phosphate rocks from Morocco, Tunisia and Syria, used in POLICE phosphate fertilizers factory, were examined. Uranium, thorium and other metals were recovered using classical leaching methods (with acidic or alkaline solutions) and percolating leaching followed by solid-liquid separation. (author).