Uranium dioxide / Photochemical reaction / Dissolution / Nitric acid SummaryIn this study, photodissolution tests of U0 2 powder, green pellet and sintered pellet were carried out in a nitric acid solution and at about 40 °C under UV irradiation. Light source is Hg-lamp emitting 254 nm wavelength. Nitric acid concentration ranged from 2 Μ to 4 M. As results, U0 2 powder and green pellet were rapidly dissolved within 2 h at 2 Μ HN0 3 while U0 2 sintered pellet was hardly dissolved. This was attributed to surface characteristics of the sintered pellet: U0 2 sintered pellet is very dense and has extremely low specific surface area. Accordingly, oxidizing species such as *NOj, N0 2 produced from N0 3 during photolysis have great difficulty to penetrate into the core of U0 2 sintered pellet. However, this was considerably improved by adding small amounts of H 2 0 2 , which could increase the surface area by etching the surface of U0 2 sintered pellet. Additionally, an increase in the number of pellets resulted in a rapid increase of uranium concentration in the solution even at 2 Μ nitric acid concentration and low temperature under irradiation.

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In general, boron recovery of 40-90% could be achieved by Reverse Osmosis (RO) membranes in neutral pH condition. As an emerging technology, Forward Osmosis (FO) membrane has attracted growing interest in wastewater treatment and desalination. The objective of this study is to evaluate the possibility of the boron removal in radioactive liquid waste by FO. In this study, the performance of FO was investigated to remove boron in the simulated liquid waste as the factors such as pH, osmotic pressure, ionic strength of solution, etc. The pH of feed solution is a major operating parameter which strongly influences to the permeation of boron and more than 80% of boron content can be separated when conducted at pH values less than 7. The water flux is not influenced but the boron flux and permeation rate tends to decrease in the low salt concentration of 1,000 mg/L. The boron flux increases linearly, but the permeation ratio of reducing boron is nearly constant even with changes in the draw solution concentration.