Improvement of multi jet low pressure impactor for high collection efficiency of UF5 in the molecular laser isotope separation of uranium

Abstract

A numerical and experimental study for the collection of photo-produced UF 5 particles was performed for the low pressure impactors which have different design factors at typical flow conditions (upstream pressure of the impactor = 10–15 Torr, pressure ratio of downstream to upstream of the impactor, P down P up = 0.2–0.5 ) in the molecular laser isotope separation of uranium at RIKEN (RIMLIS). Smaller H W ratios (the distance between the impactor orifice exit and the impaction plate, H, divided by the orifice diameter of the impactor, W) and the smaller P down P up were found to be preferable to obtain a higher collection efficiency from both numerical and experimental investigations. In addition it was experimentally demonstrated that the use of a 16 μm laser system for the selective reaction of 235UF 6 to form 235UF 5 was not relevant for the study of the collection of UF 5 particles. So, we used an ultraviolet laser system (fourth harmonic YAG laser (266 nm) and an excimer laser (KrF, 248 nm)) which was more convenient to cope with various operating conditions. The collection efficiency was found to increase with the initial concentration of UF 5 molecules produced. Applying the improved impactor stage, we obtained a collection efficiency which was approximately 10 times higher than that of our previous work. Higher collection efficiencies of photo-produced UF 5 particles enriched in 235U reduce the enrichment cost.