Surface blistering and flaking of sintered uranium dioxide samples under high dose gas implantation and annealing

International audienceHigh helium contents will be generated within minor actinide doped uranium dioxide blankets which could be used in fourth generation reactors. In this framework, it is essential to improve our understanding of the type of damage which a pellet could incur as a result of extensive helium build-up. This paper is an attempt at tackling this issue. Sintered uranium dioxide disks have been implanted with helium ions then annealed at various temperatures. Above a concentration of 0.4 at.% and above 1000°C, optical images of the sample surface revealed swollen grains and extensive areas which have exfoliated. Nuclear reaction microanalyses and atomic force microscopy observations were performed to demonstrate that helium has substantially precipitated within the swollen grains. Massive precipitation of the gas leads under these conditions to sample surface blistering which appears to precede flaking. Deuterium ion irradiations have also been performed at ambient and a direct flaking of the sample surface was observed, but for this phenomenon to be observed required much higher doses than in the He study, indicating that temperature could be an essential ingredient for gas to migrate and cause extensive precipitation. Such phenomena could possibly lead to degradation of the fuel

A Weak Bargaining Set for Contract Choice Problems

In this paper, we consider the problem of choosing a set of multi-party contracts, where each coalition of agents has a non-empty finite set of feasible contracts to choose from. We call such problems, contract choice problems. The main result of this paper states that every contract choice problem has a non-empty weak bargaining set. The need for such a solution concept which is considerably weaker than the core arises, since it is well known that even for very simple contract choice problems, the core may be empty. We also show by means of an example that the bargaining set due to Mas-Colell (1989), as well as a weaker version of it, may be empty for contract choice problems, thereby implying that the weakening we suggest is in some ways tigh

Alpi e patrimonio industriale : cultura e memoria, XIX-XX sec. = Alpes et patrimoine industriel : culture et mémoire, XIXe-XXe siècles = Alpen und industrielles Erbe : Kultur und Erinnerung, 19.-20. Jahrhundert

Cosa racconta il passato industriale delle Alpi? I vari studi contenuti in questo volume si interrogano su differenze e similitudini della patrimonializzazione dell’industria rispetto all’evoluzione della memoria e della costruzione patrimoniale promossa in questi ultimi decenni nel mondo alpino

Entry and Exit Strategies in Migration Dynamics

This work is devoted to study the role of combined entry and exit strategies in the migration process. We develop a real option model in which the community of immigrants in the host country is described as a club and the immigrants benefits is a U-shaped function, depending on the dimension of the district. There exist two threshold levels: the first one triggers the migration choice, while the second triggers the return to the country of origin. The theoretical results show that the phenomenon of hysteresis is amplified by the existence of a community both in the entry case and in the exit case. Furthermore, the community can reduce the minimum wage level required to trigger both exit and entry: this fact could explain why in some cases we observe migration inflows with a low wage differential and also with underunemployment. We show also some possible further extensions of the model: in one case we introduce a possible way to select the entrants skills and in another case we show some theoretical implementations to include possible policy shocks in the migrants choice

Ethnic Minorities Rewarded: Ethnostratification on the Wage Market in Belgium

Several previous researches have confirmed the hypothesis of ethnostratification, which holds that the labour market is divided into different ethnic layers. While people of a European origin are over-represented in the top layers (the primary market), people with non-European roots and/or nationalities are more concentrated in bottom layers (the secondary market). Relative to the primary market, this secondary market is characterized by a higher chance of unemployment, lower wages, poorer working conditions and greater job insecurity. This paper deals with a very important condition of work: the wage. Does origin have an impact on the level of wage? We make a distinction between nine origin groups: Belgians, North en West Europeans, South Europeans (from Greece, Spain, Portugal), Italians, East Europeans, Moroccans, Turks, Sub Sahara Africans and Asians. The first part of this article briefly describes the database used for the analyses and presents a few general figures for the total Belgian population. In the second part we examine the impact of origin on wage levels. For each origin group we will give an overview of the average daily wages and the partition over the wage classes. For the weaker populations, gender and age are taken into account. Finally, by means of a regression analysis, we will examine the influence of origin while controlling a few other variables that may influence the wage level

Empirical Analysis of National Income and So2 Emissions in Selected European Countries

Data on GDP per capita and sulfur emissions for twelve European countries were analyzed to determine the relationship between emissions and income in these countries. As a whole, the relationship between sulfur emissions and per capita income is a fourth order polynomial and not a quadratic one as found in most studies. When countries were examined individually, seven out of the twelve countries depicted the same relationship. Looking closely at the regulations restricting sulfur emissions in the UK, the impact of all regulations supported the inverted U-shaped Kuznets curve. Individually, however, it is found that only two regulations have statistically significant impacts: Smoke Abatement Act in 1926 (reduced the amount of sulfur associated with a given level of GDP); and Clean Air Act in 1956 (increased the amount of sulfur emissions associated with a given level of GDP)