Activity determination of the difficult to measure radionuclide 55Fe in operational radioative waste from the Angra Nuclear Power Plant

Abstract

Pressurized Water Reactors, PWR, are responsible for converting nuclear energy from the nuclear reactions, in the core, into thermal energy by heat exchange with the water in the primary system and then into mechanical energy by the pressure increase from the heat exchange and at last, electrical energy, from the turbine rotation due to the resultant pressure. In a reactor such as described, cool water must flow through the Primary System (where the nuclear core is located) in order to allow heat exchange for electrical energy generation and also to refrigerate the core, providing it will not to be melted or causing any acci dent. Materials that make up the internal part of the primary system such as the walls or core coating may suffer effects like drag force due to the high water pressure or neutron activation due to the high l evels of radiation. Therefore some of these nucl ides that compose these materials are expected to be present in the core water and so, a filtration system is required to reduce these nuclides concentrations. At Angra Nuclear Power Plant two types of filtration systems are used , ion exchange resin, respo nsible for adsorbing these nuclides and a polymer type filter responsible for withholding solid particles in suspension. After a while, these filters become saturated and must b e replaced; once replaced , the old ones become Radioactive Waste of Low or Medi um Activity. This study has evaluated the chemical yield of different procedures for 55 Fe determination by using anion exchange chromatography, to be further applied to determine the activity concentration in nuclear waste samples. The activity concentrati ons were determined by Liquid Scintillation Counting (LSC) and Gamma Spectrometry (GS). This project is part of a bigger objective that aims to fulfill several regulations from the Brazilian National Nuclear Energy Commission (CNEN) and the development of a repository for proper storage of radioactive waste materials