Radioactive waste sampling by Laser Ablation Sample Transfer (LAST)

The appropriate handling and storing of radioactive waste are important for the protection and safety of human lives and to avoid environmental impacts. For this purpose, correct characterization of the contaminants is fundamental as it impacts the storage methods and the personal protective equipment necessary to handle it. Said characterization pertains to determining the chemical and physical characteristics of the desired material, along with its radioactivity. The most common method is scrubbing, in which an operator utilizes a porous material, such as a paper filter, to rub against the surface of the target whilst applying pressure. The material becomes a sample, which is then meticulously analyzed in search of specific radionuclides. This method, however, is unable to consistently ascertain the amount of contaminants present in the original material as it heavily relies on the dexterity of the operator, the amount of pressure applied, the texture of the material and the chemical interactions between the radionuclides and the material's surface. This project seeks to develop a new method of sampling metallic surfaces for radiological contaminants through laser ablation. Laser ablation is a process in which the energy emitted by a laser is focused into a small area. This concentration of energy deposition is capable of making the material around the center of the laser-affected area heat up above its point of vaporization. Consequently, part of the material's surface is removed in the form of gas, plasma, liquid or small solid molecules. These can then be deposited in another surface such as a microscope glass slide in a process often referred to as Laser Ablation Sample Transfer (LAST). (author)