1 Method development and validation for simultaneous determination of IEA- R1 reactor’s pool water U and Si content by ICP OES João Cristiano Ulrich 1 , Sabine Neusatz Guilhen 1 , Marycel Elena Barboza Cotrim 1 , Maria Aparecida Faustino Pires 1 1 Instituto de Pesquisas Energéticas e Nucleares, IPEN-CNEN/SP - Av. Prof. Lineu Prestes, 2242 - Cidade Universitária - CEP: 05508-000 - São Paulo/SP. E-mail: jculrich@ipen.br Abstract: IPEN’s research reactor, IEA-R1, an open pool type research reactor moderated and cooled by light water. High quality water is a key factor in preventing the corrosion of the spent fuel stored in the pool. As a safety management policy, IPEN has adopted a water chemistry control which periodically monitors the levels of uranium (U) and silicon (Si) in the pool’s reactor. An analytical method was developed and validated for the determination of U and Si by ICP OES. This work describes the validation process including the parameters selectivity, linearity, quantification limit, precision and recovery. Keywords: validation, uranium, silicon 1. INTRODUCTION IEA-R1, an open pool type research reactor moderated and cooled by light water, was commissioned 1957 and is located at the Instituto de Pesquisas Energéticas e Nucleares, IPEN/CNEN-SP, a Brazilian agency managed by the National Nuclear Energy Commission. The reactor’s fuel elements use low enriched uranium (LEU) targets, i.e., up to 20% enriched uranium ( 235 U isotope), assembled as fuel plates of U3Si2 dispersed in Al [1]. Spent fuel is provisionally stored in the pool until relocation to a final disposal site or until the decay heat is low enough to allow migration to a dry storage facility. Systematic treatment and purification of the pool water is required to its quality assurance, a key factor in preventing corrosion of aluminum clad fuel elements and other structural components in water [2-4]. Also, dispersed impurities in the water may become activated by neutron flux as the water circulates through the reactor core, impairing radiological shielding and, consequently, the attenuation of the radiation emitted by the reaction in the core. This way, specifying requirements and operational limits for water treatment and purifications systems is essential for the management of water quality in research reactors. Therefore, the Research Reactor Center (CRPq/IPEN) has established sampling procedures and physical- chemical parameters to periodically monitor the water quality. The Chemistry and Environment Center (CQMA/IPEN) provides assistance concerning the water chemistry control, in which the levels of silicon and uranium in the pool’s reactor are determined. This way, the detection of either of these elements in the water may indicate a possible leakage of the fuel to the reactor’s pool.