Micro Heteregeneous Approaches for the Insertion of Reprocessed and Combined Thorium Fuel Cycles in a PWR System
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Micro Heteregeneous Approaches for the Insertion of Reprocessed and Combined Thorium Fuel Cycles in a PWR System Fabiana B. A. Monteiro1,2, Victor F. Castro1, Rochkhudson B. de Faria1, Ângela Fortini1, Clarysson A. M. Da Silva1, Claubia Pereira1,2 1 Departamento de Engenharia Nuclear – Escola de Engenharia Universidade Federal de Minas Gerais Avenida Antônio Carlos, 6627, Pampulha Belo Horizonte, MG, Brasil 2 Instituto Nacional de Ciências e Tecnologia de Reatores Nucleares Inovadores/CNPq, Brazil ABSTRACT A micro heteregenous reprocessed fuel spiked with thorium in a PWR fuel element considering (TRU-Th) cycle was simulated using three different configurations and different fissile materials that varied from 6.0% to 7.0%. The reprocessed fuels were obtained using the ORIGEN 2.1 code from a burned PWR standard fuel (33,000 MWd/tHM burned), with 3.1% of initial enrichment, which was remained in the cooling pool for five years and then reprocessed using UREX+ technique. The keff and plutonium generation during the burnup were evaluated and compared with the standard fuel. This study was performed using the SCALE 6.0.
INTRODUCTION The current focus of reducing environmental impact of nuclear waste and extending the reactor’s lifetime lead to new projects fuel-related, in order to get a high burn-up and natural resources utilization [1]. An important aspect of spent fuel management, which continues to be a challenge for many countries, is the presence of minor actinides and fission products, which contribute to long-term radiotoxicity. A suitable option to manage the spent fuel would be reprocessing and recycling it [2]. Thorium-based fuels can be used to reduce waste disposal of the conventional uranium cycle, as well to reduce concerns related to proliferation. The thorium’s potential as a nuclear fuel has been investigated since the beginning of the nuclear era, although the thorium fuel cycle as a whole has never been fully developed. Today, the opportunities and challenges that could arise from the use of thorium in the nuclear fuel cycle are still being studied in some countries and in the context of diverse international programs around the world [3]. The Departamento de Engenharia Nuclear (DEN) of Universidade Federal de Minas Gerais (UFMG) has been studying new fuels to PWR since the nineties, including the insertion of reprocessed fuels and thorium [4,5]. To get a higher burnup, the introduction of micro heterogeneous approach can be used. It is characterized by the spatial separation of a few millimeters or centimeters between thorium and uranium in a fuel element or throughout the assembly. As thorium has no fissile isotopes, its introduction in a reactor must be compensated by enriched uranium [6]. Today’s MOX fuels are comprised of approximately 5% plutonium for 95% natural or depleted uranium. While the irradiation tends to decrease the initial amount of plutonium, the presence of 238U leads to a partial reconstitution of the plutonium stockpile. The destruction of
plutonium can be speeded up by replac
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