Theory of a quodon gas. With application to precipitation kinetics in solids under irradiation

Rate theory of the radiation-induced precipitation in solids is modified with account of non-equilibrium fluctuations driven by the gas of lattice solitons (a.k.a. quodons) produced by irradiation. According to quantitative estimations, a steady-state density of the quodon gas under sufficiently intense irradiation can be as high as the density of phonon gas. The quodon gas may be a powerful driver of the chemical reaction rates under irradiation, the strength of which exponentially increases with irradiation flux and may be comparable with strength of the phonon gas that exponentially increases with temperature. The modified rate theory is applied to modelling of copper precipitation in FeCu binary alloys under electron irradiation. In contrast to the classical rate theory, which disagrees strongly with experimental data on all precipitation parameters, the modified rate theory describes quite well both the evolution of precipitates and the matrix concentration of copper measured by different methodsComment: V. Dubinko, R. Shapovalov, Theory of a quodon gas. With application to precipitation kinetics in solids under irradiation. (Springer International Publishing, Switzerland, 2014

Effect of radiation-induced emission of Schottky defects on the formation of colloids in alkali halides

Formation of vacancy clusters in irradiated crystals is considered taking into account radiation-induced Schottky defect emission (RSDE) from extended defects. RSDE acts in the opposite direction compared with Frenkel pair production, and it results in the radiation-induced recovery processes. In the case of alkali halides, Schottky defects can be produced as a result of the interaction of extended defects with excitons, as has been suggested previously. We consider a model that takes into account excitonic mechanisms for the creation of both Frenkel and Schottky defects, and which shows that although the contribution of the latter mechanism to the production of primary defects may be small, its role in the radiation-induced evolution of microstructure can be very significant. The model is applied to describe the evolution of sodium colloids and the formation of voids in NaCl, which is followed by a sudden fracture of the material, presenting a potential problem in rock salt-based nuclear waste repositories. The temperature, dose rate and dose dependence of colloid growth in NaCl doped with different types of impurities is analyzed. We have found that colloid growth may become negative below a threshold temperature (or above a threshold dose rate), or below a certain impurity concentration, which is determined by the RSDE, that depends strongly on the type and concentration of the impurities. The results obtained with the model are compared with experimental observations.

Plastische vervorming van wolfraam onder blootstelling aan een fusie-plasma-omgeving

Tesis de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, leída el 11-06-2018Using Nuclear Fusion to produce price-competitive electricity is an important element in the European Research and Development Agenda. The next big step is to create ‘first plasma’ in ITER – the key facility for development of commercial fusion power. While this fusion test-bed is under construction, a number of technical and scientific challenges remain problems that must be solved to enable the efficient and safe operation of ITER. Ensuring proper functioning of the divertor is one of those challenges. The field lines of a diverted plasma deflect particles, in particular impurities, in the scrape-off layer (the region from the vessel region up to the magnetic separatrix, which is the boundary of the confined plasma region) towards the divertor, where they are to be neutralized and removed through a pumping system. The divertor exhausts the heat produced by the fusion reactions and enables the removal of helium and other impurities by apumping system, hence it is a vital component of the whole system...Het gebruik van kernfusie om prijsconcurrentiële elektriciteit te produceren is eenbelangrijk element in de Europese Onderzoeks- en Ontwikkelingsagenda. De volgendegrote stap is het creëren van het eerste plasma in ITER - de belangrijkste faciliteit voorde ontwikkeling van commerciële fusiecentrales. Terwijl deze fusie testreactor inaanbouw is, blijven er een aantal technische en wetenschappelijke uitdagingen,problemen die moeten worden opgelost om de efficiënte en veilige werking van ITERmogelijk te maken.Het verzekeren van een goede werking van de divertor is een van die uitdagingen. Develdlijnen van een afgeleid plasma leiden de deeltjes om, in het bijzonderonzuiverheden, in de afscheidingslaag (het gebied in het vacuümvat tot aan demagnetische separatrix, die de grens van het afgesloten plasmagebied vormt) naar dedivertor, waar ze worden geneutraliseerd en verwijderd via een pompsysteem. Dedivertor vormt de uitlaat voor de warmte die door de fusie reacties wordt veroorzaakten maakt het mogelijk om He en andere onzuiverheden te verwijderen doo..Fac. de Ciencias FísicasTRUEunpu