Bond between structural transitions on a surface and in a volume of crystals

The object to be attained is to establish a deep analogy between the mechanisms of structural transitions in two- and three-dimensional systems, use elaborated representations on mechanisms of transitions on a surface of crystals for description of critical phenomena in volume systems. New theories and models of such phenomena as reconstruction of semiconductor surface, melting of two-dimensional and three-dimensional crystals, transition to superionic state, solidification of eutestic alloys have been constructed. New methods of external effect on the crystals for a change of their physical-chemical properties have been first predicted; a method of creation of macroscopic laminated films with important technological properties has been proposedAvailable from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio

Modelling of Grain Growth Kinetics in Porous Ceramic Materials under Normal and Irradiation Conditions

Effect of porosity on grain growth is both the most frequent and technologically important situation encountered in ceramic materials. Generally this effect occurs during sintering, however, for nuclear fuels it also becomes very important under reactor irradiation conditions. In these cases pores and gas bubbles attached to the grain boundaries migrate along with the boundaries, in some circumstances giving a boundary migration controlled by the movement, coalescence and/or sintering of these particles. New mechanisms of intergranular bubble and pore migration which control the mobility of the grain boundary under normal and irradiation conditions are reviewed in this paper

Investigation of core degradation (COBE)

International audienceThe COBE project started in February 1996 and finished at the end of January 1999. The main objective was to improve understanding of core degradation behaviour during severe accidents through the development of computer codes, the carrying out of experiments and the assessment of the computer codes’ ability to reproduce experimental behaviour. A major effort was devoted to quenching behaviour and a substantial achievement of the project was the design and commissioning of a new facility for the simulation of quenching of intact fuel rods. Two tests, carefully scaled to represent realistic reactor conditions, were carried out in this facility and the hydrogen generated during the quenching process was measured using two independent measuring systems. The codes were able to reproduce the results in the first test, where little hydrogen was generated but not the second test, where the extra steam produced during quenching caused an invigorated Zircaloy oxidation and a substantial hydrogen generation. A number of smaller parametric experiments allowed detailed models to be developed for the absorption of hydrogen and the cracking of cladding during quenching. COBE also investigated other areas concerned with late-phase phenomena

Investigation of Core Degradation (COBE).

Abstract not availableJRC.(ISIS)-Institute For Systems, Informatics And Safet

Core Loss during a Severe Accident (COLOSS).

Abstract not availableJRC.F-Institute for Energy (Petten