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Abstract : Modeling of Tests of Primary Water Stress Corrosion Cracking of Alloy 182 of Pressurized Water Reactor According to EPRI and USNRC Recommendations
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Abstract: One of the main degradation mechanisms which cause risks to safety and reliability of pressurized water nuclear reactors is the primary water stress corrosion cracking (PWSCC) in nickel alloys, such as Alloy 600 (75Ni-15Cr-9Fe), and its weld metal Alloy 182 (67 Ni-15Cr-8Fe). It can appear at several reactor nozzles dissimilarly welded with Alloys 182/82 between steel ASTM A-508 G3 and stainless steel AISI316L, among others. The hydrogen which is dissolved to primary water to prevent radiolysis, can also have influence on the stress corrosion cracking behavior.In this article one departs from a study of Lima based in experimental data obtained from CDTN-Brazilian Nuclear Technology Development Center, in slow strain rate test (SSRT). It was prepared and used for tests a weld in laboratory, similar to dissimilar weld in pressurizer relief nozzles, operating at Brazilian NPP Angra 1. It was simulated for tests, primary water at 325oC and 12.5 MPa containing levels of dissolved hydrogen: 2, 10, 25, and 50 cm3 STP H2/kgH2O. The objective of this article is to propose an adequate modeling based on these experimental results, for PWSCC crack growth rate according to the levels of dissolved hydrogen, based on EPRI-MRP-263 NP. Furthermore, it has been estimated the stress intensity factor applied for these tests: according with these, some another models described on EPRI-MRP-115, and an USNRC Technical Report, have been tested. According to this study, CDTN tests are adequate for modeling comparisons within EPRI and USNRC models. Keywords: Hydrogen Effect, Modeling, Pressurized Water Stress Corrosion Cracking, Slow Strain Rate Tests, Weld Nickel Alloys 82/182.Download Full Article |
Abstract : Comprehensive Evaluation of Biomass Energy Technologies in China
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Abstract: Based on a comprehensive review of the different biomass energy technologies in China, a hybrid evaluation model founding on Analytic Hierarchy Process(AHP) is proposed to offer a comprehensive evaluation of a variety of biomass energy technologies in China. In this model, three evaluation criteria, including the applicability of technology, economic viability and environment-friendly, are defined and nine indicators, including resources supply, equipment and technology, energy efficiency, energy grade,production cost, economic benefit, ecological impact, environmental pollution and social benefit,are devised. Priorities are established in this study based on pairwise comparisons of the elements. In addition, the model has been validated byvarious utilization technologies reported in literatures. Results show that environmental pollution, social benefit, ecological impact and resources supply greatly impact on the application of biomass technologies, followed by economic benefit. Besides, it is demonstrated that integrated technologies of biomass energy, which is closely related with residential daily life and compatible with local ecological environment, possess evident superiority. Furthermore, the outcome can be supportive for guidingfuture development of biomass energy in China. Keywords: Biomass energy technologies,analytic hierarchy process, comprehensive evaluation, development, China.Download Full Article |
Abstract : Performance of Clay Wood Cook Stove: An Analysis of Cost and Fuel Savings
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Abstract: The assessment of cooking energy cost and efficiency of improved woodfuel clay cookstoves in Nigeria have been considered in this study. Two improved wood burning clay cookstove models were compared to the 3-stone fire stove using the water boiling test and controlled cookingtest. The following parameters: specific fuel consumption (SFC), thermal efficiency, ebulution time and cooking energy cost were considere as key indicators for comparison. The results show that the fire power for the cold starts phases were 7.72KW, 8.59KW and 9.78KW for the stove with grate, modified stove without grate and the 3-stone open fire (TFS) respectively. The thermal efficiencies ranges between 19-35%, 13.8-26.8% and 11.7-22.8% for the cold start, hot start and simmer phases for mud stove with grate (MSWG), mud stove no grate (MSNG) and three stone open fire (TFS) respectively. MSWG, showed the highest savings potential on wood fuel consumption with the lowest total wood cost of N127.80 and sfc of 1.632Kg of fuel/kg of food cooked. While MSNG and TFS, have a total wood fuel cost and SFCof N207.70 , N269.20, and 2.141, 1.632kg of fuel/kg of food cooked respectively. Keywords: Cooking energy, efficiency, improved stove, cost, Nigeria.Download Full Article |
Abstract : Generation Scheduling in Power Systems with Hydro Electric Plants
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Abstract: Medium-term generation scheduling is an important component of power systems operation and management. The traditional problem statement aimed at reducing the total production cost can hardly correspond to the market environment. The paper considers specific features of the problem statement for a wholesale electricity market environment. An approach is suggested to solve the problem on the basis of bi-level optimization models. Such models take into account possible distortion of economic and technical parameters of generating units. The proposed technique obtains equilibrium of the generation company’s interests to simulate the competitive behavior under the oligopoly electricity market. A mathematical statement of the problem supposes the application of a dynamic programming method. An algorithm for the stochastic dynamic programming application is developed. A numerical example is presented to demonstrate the applicability of the method and algorithm. The efficiency of the proposed approach is shown in comparison with the traditional generation scheduling technique. Keywords: Power system management; medium-term scheduling; market environment; bi-level approach; dynamic programming.Download Full Article |
