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Dióxido de uranio fundido estructura y dinámica de la estructura y dinámica del uranio fundido

L B Skinner¹, C J Benmore², J K R Weber³

¹X-ray Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. Mineral Physics Institute, Stony Brook University, Stony Brook, NY 11794-2100, USA. Materials Development, Inc., 3090 Daniels Court, Arlington Heights, IL 60004, USA. lawrie.skinner@gmail.com.

Science (New York, N.Y.)

|November 22, 2014

Resumen

Los investigadores estudiaron el dióxido de uranio fundido (UO2), un combustible nuclear, utilizando técnicas avanzadas. Descubrieron que el UO2 fundido tiene un número de coordinación uranio-oxígeno más bajo, lo que afecta su comportamiento durante los accidentes de reactor.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Ingeniería Nuclear Ingeniería Nuclear.
Química de altas temperaturas para la química de altas temperaturas.

Sus antecedentes:

El dióxido de uranio (UO2) es el combustible principal en los reactores de fisión nuclear.
Comprender el comportamiento del UO2 fundido es fundamental para la seguridad de los reactores nucleares durante accidentes graves.
Las altas temperaturas y la reactividad del UO2 fundido han limitado históricamente los estudios estructurales.

Objetivo del estudio:

Para investigar la estructura atómica del dióxido de uranio sólido y fundido (UO2) a temperaturas extremas.
Para determinar los cambios de coordinación del uranio y el oxígeno al fundirse.
Proporcionar datos para mejorar el modelado del comportamiento del combustible nuclear durante accidentes.

Principales métodos:

Utilizó técnicas de calentamiento láser y levitación de muestras para lograr altas temperaturas (>3140 K).
Empleó la difracción de rayos X de sincrotrón para realizar mediciones de la función de distribución de pares (PDF).
Desarrolló y refinó modelos de dinámica molecular (DM) basados en datos estructurales experimentales.

Principales resultados:

Se observó un aumento del desorden de oxígeno en UO2 sólido cerca de la transición lambda (2670 K) con un cambio mínimo en la coordinación U-O.
Se determinó una caída significativa en la coordinación media U-O de 8 a 6.7 ± 0.5 después de la fusión.
Las simulaciones de MD predijeron una mayor movilidad U-U en el estado fundido en comparación con los fundidos de 8 coordenadas.

Conclusiones:

El estudio proporciona los primeros conocimientos estructurales sobre el UO2 fundido.
La reducción de la coordinación U-O y el aumento de la movilidad U-U son características clave del UO2 fundido.
Estos hallazgos son cruciales para evaluaciones precisas de seguridad y simulaciones de accidentes en plantas de energía nuclear.

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