Understanding and simulating the material behavior during multi-particle irradiations

A number of studies have suggested that the irradiation behavior and damage processes occurring during sequential and simultaneous particle irradiations can significantly differ. Currently, there is no definite answer as to why and when such differences are seen. Additionally, the conventional multi-particle irradiation facilities cannot correctly reproduce the complex irradiation scenarios experienced in a number of environments like space and nuclear reactors. Therefore, a better understanding of multi-particle irradiation problems and possible alternatives are needed. This study shows ionization induced thermal spike and defect recovery during sequential and simultaneous ion irradiation of amorphous silica. The simultaneous irradiation scenario is shown to be equivalent to multiple small sequential irradiation scenarios containing latent damage formation and recovery mechanisms. The results highlight the absence of any new damage mechanism and time-space correlation between various damage events during simultaneous irradiation of amorphous silica. This offers a new and convenient way to simulate and understand complex multi-particle irradiation problems.

Borosilicate Nuclear Waste Glass Alteration Kinetics: Chemical Inhibition and Affinity Control

The objective of this work was to develop a more representative mathematical formulation of the alteration kinetics of the borosilicate SON68 glass by combining three approaches: (1) Compare extensive prior experimental static leaching results for SON68 glass with the first-order kinetic law in which silica is the predominant element, (2) Assess the exact role of dissolved silica on the alteration rate under conditions near and far from saturation, by means of dynamic leach tests and, (3) Compare the new data with the general kinetic law for silicates in which the reaction affinity, catalysis and inhibition are the three influencing factors.

[Utilization of a transferred arc-plasma rotating furnace to melt and found oxide mixtures at around 2000 degrees C (presentation of the film VULCANO)]

Unless security measures are taken, a hypothetical accident resulting from the loss of the cooling circuit in a pressurized water nuclear reactor could cause the heart of the reactor to melt forming a bath, called the corium, mainly composed of uranium, zirconium and iron oxides as well as the structural steel. This type of situation would be similar to the Three Mile Island accident in 1979. In order to limit the consequences of such an accident, the Atomic Energy Commission has implemented a large study program [1] to improve our understanding of corium behavior and determine solutions to stabilize it and avoid its propagation outside the unit. The VULCANO installation was designed in order to perform the trials using real materials which are indispensable to study all the phenomena involved. A film on the VULCANO trials was presented at the Henri Moissan commemorative session organized by the French National Academy of Pharmacy. The rotating furnace used to melt and found the mixture simulating the corium is a direct descendant of the pioneer work by Henri Moissan. An electrical arc is directed at the center of the load to melt which is maintained against the walls by centrifugal force. After six high-temperature trials performed with compositions without uranium oxide, the first trial with real corium showed that the magma spread rather well, a result which is quite favorable for cooling.

Chromosomal assignment of 14 genomic probes for highly polymorphic loci

Over 500 probes revealing restriction fragment length polymorphisms (RFLPs) have been isolated by Schumm et al. (1988). We describe here the chromosomal assignment of 14 of the most highly polymorphic markers in that set of probes, with polymorphism information content values of up to 0.98. The probes were mapped using a panel of human x rodent somatic cell hybrids and were found to be distributed among nine different autosomes. Chromosome localization of such highly polymorphic markers has been an important step in the construction of the human genetic map, as a large number of RFLP probes has now been localized by genetic linkage studies to these loci.