Influence of oxide films on primary water stress corrosion cracking initiation of alloy 600

In the present study alloy 600 was tested in simulated pressurised water reactor (PWR) primary water, at 360 °C, under an hydrogen partial pressure of 30 kPa. These testing conditions correspond to the maximum sensitivity of alloy 600 to crack initiation. The resulting oxidised structures (corrosion scale and underlying metal) were characterised. A chromium rich oxide layer was revealed, the underlying metal being chromium depleted. In addition, analysis of the chemical composition of the metal close to the oxide scale had allowed to detect oxygen under the oxide scale and particularly in a triple grain boundary. Implication of such a finding on the crack initiation of alloy 600 is discussed. Significant diminution of the crack initiation time was observed for sample oxidised before stress corrosion tests. In view of these results, a mechanism for stress corrosion crack initiation of alloy 600 in PWR primary water was proposed

Is international emissions trading always beneficial?

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).Economic efficiency is a major argument for the inclusion of an international emission permit trading system under the Kyoto Protocol. Using a partial equilibrium framework, energy system models have shown that implementing tradable permits for greenhouse gases internationally could reduce compliance costs associated with the emission targets. However, we show that international emission trading could be welfare decreasing under a general equilibrium framework. We describe a case of immiserizing growth in the sense of Bhagwati where the negative terms of trade and tax-interaction effects wipeout the primary income gains from emission trading. Immiserizing emission trading occurs only when there are pre-existing distortions in the economy. Simulation results based on a CGE model developed at MIT (the EPPA model) show that under an EU-wide emission trading regime the introduction of a permit trading system cause welfare losses for some of the trading countries

PERFORMANCE OF TIMBER BOARD MODELS FOR PREDICTION OF LOCAL BENDING STIFFNESS AND STRENGTH – WITH APPLICATION ON DOUGLAS FIR SAWN TIMBER

Efficient utilization of structural timber requires accurate methods for machine strength grading. One of the most accurate methods presented this far is based on data of local fiber orientation on board surfaces, obtained from laser scanning. In this paper, two potential improvements of this method are examined. The first one consists of replacing a model based on simple integration over cross sections of boards for calculation of local bending stiffness by a 3D solid finite element (FE) model from which local bending stiffness is derived. The second improvement concerns replacement of a simple model for the fiber orientation in the interior of board by a more advanced one taking location of pith and growth direction of knots into account. Application of the alternative models on a sample of more than 200 Douglas fir boards, size 40 mm X 100 mm X 3000 mm, cut from large logs, show that each of the evaluated model improvements contributes to improved grading accuracy. When local bending stiffness is calculated utilizing the herein suggested FE model in combination with the improved model of fiber orientation in the interior of boards, a coefficient of determination to bending strength as high as 0.76 is obtained. For comparison, a coefficient of determination of 0.71 is obtain using the simpler original models

Modeling the Transport Sector: The Role of Existing Fuel Taxes in Climate Policy

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).Existing fuel taxes play a major role in determining the welfare effects of exempting the transportation sector from measures to control greenhouse gases. To study this phenomenon we modify the MIT Emissions Prediction and Policy Analysis (EPPA) model to disaggregate the household transportation sector. This improvement requires an extension of the GTAP data set that underlies the model. The revised and extended facility is then used to compare economic costs of cap-and-trade systems differentiated by sector, focusing on two regions: the USA where the fuel taxes are low, and Europe where the fuel taxes are high. We find that the interplay between carbon policies and pre-existing taxes leads to different results in these regions: in the USA exemption of transport from such a system would increase the welfare cost of achieving a national emissions target, while in Europe such exemptions will correct pre-existing distortions and reduce the cost.Supported by the US Department of Energy, Office of Biological and Environmental Research [BER] (DE-FG02-94ER61937); the US Environmental Protection Agency (X-827703-01-0); the Electric Power Research Institute; and by a consortium of industry and foundation sponsors

Russia's role in the Kyoto Protocol

Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).As a result of the allocation of emissions reductions, and the differential willingness of countries to ratify, it turns out that Russia is a central player in the Kyoto Protocol. With the U.S. out and Japan and the EU ratifying, the Protocol cannot enter into force without Russian ratification. In part, U.S. rejection of the Kyoto Protocol resulted from the fact that, had the U.S. been in, its least costly road to implementation would have involved large purchases of emissions credits from Russia. With the U.S. out, Russian credits are worth much less but Russia may be able to exploit monopoly power to increase the value of those permits, or Russia could bank permits on the expectation that prices will rise in the future, perhaps as a result of the U.S. reentry into the Protocol in later periods. The Russian decision is more complex, however, in that it is also a major fossil fuel exporter. To the extent it withholds permits from the market, fossil energy prices are depressed further, and the value of its exports of energy are reduced. Thus, Russia faces a tradeoff between maximizing its permit revenue and its revenue from fossil energy exports. We develop this problem as a simple dynamic optimization problem and calibrate the model to the results of two CGE models (EPPA and GEMINI-E3) that fully capture interactions of energy trade, permit trade, and permit and energy prices. We show that carbon prices are relatively insensitive to Russia's behaviors when the U.S. is assumed to participate. It also shows that, in the absence of U.S. participation, the impact of market power by Russia and Ukraine is largely dependent on the elasticity of demand for permits. Finally, we focus on the uncertainty about the supply of CDM by developing countries. It is shown that permit prices are relatively insensitive to CDM supply in the short run but not in the long run

Relation between composition, microstructure and oxidation in iron aluminides

The relation between chemical composition, microstructure and oxidation properties has been investigated on various FeAl based alloys, the aim being to induce changes in the microstructure of the compound by selective oxidation of aluminium. Oxidation kinetics that was evaluated on bulk specimens showed that, due to fast diffusion in the alloys, no composition gradient is formed during the aluminium selective oxidation. Accordingly, significant aluminium depletion in the compound could be observed in the thinnest part of oxidised wedge-shape specimens. Another way to obtain samples of variable aluminium content was to prepare diffusion couples with one aluminide and pure iron as end members. These latter specimens have been characterised using electron microscopy and first results of oxidation experiments are presented

Correspondences, an exhibition of installations : Peter Burgess et al

Correspondences, an exhibition of installations : Peter Burgess et al Catalogue of Exhibition held at the Tasmanian School of Art, University of Tasmania 4 July-20 July, 1984 Works by Peter Burgess, Peter Callas, Adrian Hall, Maryrose Sinn, Gregory Smith, Neil Stevenson, Alain Viguier, John Youn

Microstructural Characterization of Graphite Spheroids in Ductile Iron

The present work brings new insights by transmission electron microscopy allowing disregarding or supporting some of the models proposed for spheroidal growth of graphite in cast irons. Nodules consist of sectors made of graphite plates elongated along a hai direction and stack on each other with their c axis aligned with the radial direction. These plates are the elementary units for spheroidal growth and a calculation supports the idea that new units continuously nucleate at the ledge between sectors