Stability of a Nanofiltration Membrane After Contact with a Low-Level Liquid Radioactive Waste

This study investigated the treatment of a liquid radioactive waste containing uranium (235U + 238U) using nanofiltration membranes. The membranes were immersed in the waste for 24–5000 h, and their transport properties were evaluated before and after the immersion. Surface of the membranes changed after immersion in the waste. The SW5000 h specimen lost its coating layer of polyvinyl alcohol, and its rejection of sulfate ions and uranium decreased by about 35% and 30%, respectively. After immersion in the waste, the polyamide selective layer of the membranes became less thermally stable than that before immersion.

Evaluation of Transport Properties of Nanofiltration Membranes Exposed to Radioactive Liquid Waste

The application of membrane separation processes (PSM) for treatment of radioactive waste requires the selection of a suitable membrane for the treatment of waste, as the membrane will be directly exposed to the radioactive liquid waste, and also exposed to ionizing radiation. The nanofiltration membrane is most suitable for treatment of radioactive waste, since it has high rejection of multivalent ions. Usually the membranes are made of polymers and depending on the composition of the waste, type and dose of radiation absorbed may be changes in the structure of the membrane, resulting in loss of its transport properties. We tested two commercial nanofiltration membranes: NF and SW Dow/Filmtec. The waste liquid used was obtained in the process of conversion of uranium hexafluoride gas to solid uranium dioxide, known as "carbonated water". The membranes were characterized as their transport properties (hydraulic permeability, permeate flux and salt rejection) before and after their immersion in the waste for 24 hours. The surface of the membranes was also evaluated by SEM and FTIR. It was observed that in both the porosity of the membrane selective layer was altered, but not the membrane surface charge, which is responsible for the selectivity of the membrane. The NF membranes and SW showed uranium ion rejection of 64% and 55% respectively.

Employment of the Technique of Radiotracers for Analysis of Industrial Filters

The main aim of this work is to develop a methodology to evaluate the characteristics of porous media in filter using the radio-tracing technique. To do this, an experimental prototype filter made up of an acrylic cylinder, vertically mounted and supported on the lower side by a controlled leaking valve was developed. Two filters (spheres of acrylic and silica crystals) were used to check the movement of the water through the porous media using 123I in its MIBG (iodine-123-meta-iodo benzyl-guanidine) form. Further up the filter an instantaneous injection of the substance makes it possible to see the passage of radioactive clouds through the two scintillatory detectors NaI (2x2)” positioned before and immediately after the cylinder with the filtering element (porous media). The are caused by the detectors on the passage of the radioactive cloud are analyzed through statistical functions using the weighted moment method which makes it possible to calculate the Residence-Time (the amount of time the tracer takes to thoroughly pass through the filter) per the equation of dispersion in tubular flow and the one-directional flow of the radiotracer in the porous media.

Preparation of Excitation Sources to Portable X-Ray Spectrometer by Recovering 241am from Radioactive Lightning Conductor

With the prohibition of the use of radioactive lightning conductor in Brazil, this material passed to be collected and stored as radioactive waste in the waste deposits of The Brazilian National Nuclear Energy Commission (CNEN). The majority of these lightning conductor used as radioactive source 241Am with activity varying of 1 the 5 mCi. In this work are presented preliminary studies by recovering of 241Am through the electroplating technique, in order to posterior use as sources to portable X-rays fluorescence spectrometer. The 241Am sources have been removed from lightning conductor and dissolved in acid solution. The solution presented an activity of 0,6 Ci L-1. Small amounts of this solution were added to some electrolytes and tested in order to evaluate optimum electrolyte for deposition of 241Am. It was studied as electrolytes: HNO3 (0,2 mol L-1), NH4Cl (5,0 mol L-1) and a mixture of KCN and K2CO3 (in the rate of 2,0 g of each per liter). Yields of up to 90% were obtained applied a current density of 50 mA cm-2.