Suchergebnisse

Within the licensing process of the KWU Atucha II PHWR (Pressurized Heavy Water Reactor), the BEPU (Best Estimate Plus Uncertainty) approach has been selected for issuing of the Chapter 15 on FSAR (Final Safety Analysis Report). The key steps of the entire process are basically two: (a) the selection of PIE (Postulated Initiating Events) and (b) the analysis by best estimate models supported by uncertainty evaluation. Otherwise, key elements of the approach are (1) availability of qualified computational tools including suitable uncertainty method, (2) demonstration of quality, and (3) acceptability and endorsement by the licensing authority. The effort of issuing Chapter 15 is terminated at the time of issuing of the present paper, and the safety margins available for the operation of the concerned NPP (Nuclear Power Plant) have been quantified.

The evaluation of uncertainty constitutes the necessary supplement of best-estimate calculations performed to understand accident scenarios in water-cooled nuclear reactors. The needs come from the imperfection of computational tools, on the one side, and the interest in using such a tool to get more precise evaluation of safety margins. The paper reviews the salient features of three independent approaches for estimating uncertainties associated with predictions of complex system codes. Namely, the propagations of code input error and calculation output error constitute the keywords for identifying the methods of current interest for industrial applications, while the adjoint sensitivity-analysis procedure and the global adjoint sensitivity-analysis procedure, extended to performing uncertainty evaluation in conjunction with concepts from data adjustment and assimilation, constitute the innovative approach. Throughout the developed methods, uncertainty bands can be derived (both upper and lower) for any desired quantity of the transient of interest. For one case, the uncertainty method is coupled with the thermal-hydraulic code to get the code with capability of internal assessment of uncertainty, whose features are discussed in more detail.

In the last four decades, large efforts have been undertaken to provide reliable thermal-hydraulic system codes for the analyses of transients and accidents in nuclear power plants. Whereas the first system codes, developed at the beginning of the 1970s, utilized the homogenous equilibrium model with three balance equations to describe the two-phase flow, nowadays the more advanced system codes are based on the so-called "two-fluid model" with separation of the water and vapor phases, resulting in systems with at least six balance equations. The wide experimental campaign, constituted by the integral and separate effect tests, conducted under the umbrella of the OECD/CSNI was at the basis of the development and validation of the thermal-hydraulic system codes by which they have reached the present high degree of maturity. However, notwithstanding the huge amounts of financial and human resources invested, the results predicted by the code are still affected by errors whose origins can be attributed to several reasons as model deficiencies, approximations in the numerical solution, nodalization effects, and imperfect knowledge of boundary and initial conditions. In this context, the existence of qualified procedures for a consistent application of qualified thermal-hydraulic system code is necessary and implies the drawing up of specific criteria through which the code-user, the nodalization, and finally the transient results are qualified.

The origins and nature of nationhood and nationalism continue to be topics of heated scholarly debate. This major new reference work with contributions from an international team of scholars provides a comprehensive account of ideas and practices of nationhood and nationalism from antiquity to the present. It considers both continuities and discontinuities, engaging critically and analytically with the scholarly literature in the field. The History also explores nationhood and nationalism's relationships with a wide variety of cultural practices and social institutions, in addition to the phenomenon's crucial political dimensions. Its wide range of regional case studies brings a truly global, comparative perspective to a field long constrained by Eurocentric assumptions. Volume I tracks turning points in the history of nationhood and nationalism from ancient times to the twentieth century. Volume II theorizes the connections between nationhood/nationalism and ideology, religion and culture. Together, they enable readers to understand the roots of how nationhood and nationalism function in the present day

This major new reference work with contributions from an international team of scholars provides a comprehensive account of ideas and practices of nationhood and nationalism from antiquity to the present. It considers both continuities and discontinuities, engaging critically and analytically with the scholarly literature in the field. Volume I starts with a series of case studies of classical civilizations. It then explores a wide range of pivotal moments and turning points in the history of identity politics during the age of globalization, from 1500 through to the twentieth century. This overview is truly global, covering countries in East and South Asia as well as Europe and the Americas.

This major new reference work with contributions from an international team of scholars provides a comprehensive account of ideas and practices of nationhood and nationalism from antiquity to the present. It considers both continuities and discontinuities, engaging critically and analytically with the scholarly literature in the field. Volume I starts with a series of case studies of classical civilizations. It then explores a wide range of pivotal moments and turning points in the history of identity politics during the age of globalization, from 1500 through to the twentieth century. This overview is truly global, covering countries in East and South Asia as well as Europe and the Americas.

This major new reference work with contributions from an international team of scholars provides a comprehensive account of ideas and practices of nationhood and nationalism from antiquity to the present. It considers both continuities and discontinuities, engaging critically and analytically with the scholarly literature in the field. In volume II, leading scholars in their fields explore the dynamics of nationhood and nationalism's interactions with a wide variety of cultural practices and social institutions – in addition to the phenomenon's crucial political dimensions. The relationships between imperialism and nationhood/nationalism and between major world religions and ethno-national identities are among the key themes explained and explored. The wide range of case studies from around the world brings a truly global, comparative perspective to a field whose study was long constrained by Eurocentric assumptions.