Surface purification of uranium by nano-second pulsed laser treatment

Abstract The corrosion of uranium and its alloy greatly restricts their engineering applications. Surface modification is the main way used to inhibit uranium from corrosion. However, there is a problem that many inclusions still exists on uranium surface after smelting purification, and corrosion sites have been found preferred to nucleate around these inclusions which destroy the integrity of protective coatings and even make it disabled. So, surface purification to deal with these inclusions is an effective method to improve the stability of surface modified layer. In this paper, Nano-second pulsed laser was induced on uranium surface to decrease the content of surface inclusions. The influence of experiment parameters on purification effect was studied by changing the laser energy and scanning speed. The corrosion resistance of uranium before and after laser treatment was tested through electrochemical polar test. The results suggest that the solid inclusion with small size eject out of uranium surface through hydrokinetics eruption caused by rapidly melting and expanding of uranium under and around the inclusion during the interaction process of laser pulse and uranium surface. The inclusion with large scale is covered by melting uranium around it, and then the covering uranium cools and curdles to form a uranium layer over the inclusion. The eruption of the small-sized inclusions and being covered of the large-sized ones reduce the impurity content and purify the surface of uranium. The covering effect on inclusions with large scale improves when the laser energy increases or the scanning speed decreases. After laser surface purification, the corrosion current density of uranium declines, which indicates that the corrosion resistance of uranium is enhanced.