Publicación: Análisis Modal Operacional de señales de ruido neutrónico para la caracterización mecánica del núcleo de un PWR
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2022
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Universidad Nacional de Educación a Distancia (España), Universidad Politécnica de Madrid. Departamento de Ingeniería Mecánica
Resumen
Las técnicas de Análisis Modal Operacional (OMA) son ampliamente utilizadas para el estudio de propiedades dinámicas e identificación modal de sistemas y estructuras, y se basan únicamente en las medidas de la respuesta mecánica del sistema bajo estudio. Normalmente estas medidas se obtienen de acelerómetros dispuestos sobre la estructura. En el caso de un reactor nuclear comercial, no es posible introducir acelerómetros en el núcleo, pero es posible medir la respuesta mecánica indirectamente utilizando los detectores de neutrones. Además, no es posible conocer directamente las excitaciones de entrada, ya que son muy variadas y de naturaleza tanto mecánica como termohidráulica. La excitación global puede asumirse de naturaleza aleatoria como ruido blanco gaussiano. Se conoce como ruido neutrónico a las fluctuaciones en el tiempo de la población de neutrones en una región. Esta magnitud está relacionada con la potencia del reactor y proporciona también información sobre los fenómenos que tienen lugar en el interior del núcleo. La fuerte relación que existe entre la neutrónica, la mecánica y la termohidráulica, permite que a través del análisis y seguimiento del ruido neutrónico se pueda apreciar una gran cantidad de fenómenos al mismo tiempo. El ruido neutrónico es recogido por una matriz de contadores de neutrones repartidos dentro y fuera del núcleo. El número de sensores puede rondar los 50 o más, según el diseño. El presente trabajo expone el uso de la técnica EFDD (Enhance Frecuency Domain Decomposition) sobre datos reales para caracterizar una resonancia en el entorno de los 8 Hz. Esta región tradicionalmente se asocia a un modo de vibración de la vasija, conocido como “Beam Mode”. Los resultados obtenidos son prometedores y muestran que la metodología proporciona información de manera eficiente que permite caracterizar este tipo de resonancias y ayuda a identificar los orígenes físicos de las mismas. En línea con estudios anteriores, se comprueba que la resonancia analizada no parece corresponder a un movimiento pendular en los reactores de tipo KWU.
Operational Modal Analysis (OMA) techniques are widely used for the study of dynamic properties and modal identification of systems and structures, and are based solely on measurements of the mechanical response of the system under study. Normally these measurements are obtained from accelerometers arranged on the structure. In the case of a commercial nuclear reactor, it is not possible to introduce accelerometers into the core, but it is possible to measure the mechanical response indirectly using neutron detectors. In addition, it is not possible to know the input excitations directly, since they are very varied and are both mechanical and thermohydraulic in nature. The global excitation can be assumed to be random in nature as Gaussian white noise. Neutron noise is known as the fluctuations in time of the population of neutrons in a region. This magnitude is related to the power of the reactor and also provides information on the phenomena that take place inside the core. The strong relationship that exists between neutronics, mechanics and thermohydraulics, allows a large number of phenomena to be appreciated at the same time through the analysis and monitoring of neutron noise. The neutron noise is picked up by an array of neutron counters spread inside and outside the core. The number of sensors can be around 50 or more, depending on the design. This paper exposes the use of the EFDD (Enhance Frequency Domain Decomposition) technique on real data to characterize a resonance around 8 Hz. This region is traditionally associated with a vibration mode of the vessel, known as "Beam Mode". The results obtained are promising and show that the methodology efficiently provides information that allows to characterize this type of resonances and helps to identify their physical origins. In line with previous studies, it is verified that the analyzed resonance does not seem to correspond to a pendular movement in KWU type reactors.
Operational Modal Analysis (OMA) techniques are widely used for the study of dynamic properties and modal identification of systems and structures, and are based solely on measurements of the mechanical response of the system under study. Normally these measurements are obtained from accelerometers arranged on the structure. In the case of a commercial nuclear reactor, it is not possible to introduce accelerometers into the core, but it is possible to measure the mechanical response indirectly using neutron detectors. In addition, it is not possible to know the input excitations directly, since they are very varied and are both mechanical and thermohydraulic in nature. The global excitation can be assumed to be random in nature as Gaussian white noise. Neutron noise is known as the fluctuations in time of the population of neutrons in a region. This magnitude is related to the power of the reactor and also provides information on the phenomena that take place inside the core. The strong relationship that exists between neutronics, mechanics and thermohydraulics, allows a large number of phenomena to be appreciated at the same time through the analysis and monitoring of neutron noise. The neutron noise is picked up by an array of neutron counters spread inside and outside the core. The number of sensors can be around 50 or more, depending on the design. This paper exposes the use of the EFDD (Enhance Frequency Domain Decomposition) technique on real data to characterize a resonance around 8 Hz. This region is traditionally associated with a vibration mode of the vessel, known as "Beam Mode". The results obtained are promising and show that the methodology efficiently provides information that allows to characterize this type of resonances and helps to identify their physical origins. In line with previous studies, it is verified that the analyzed resonance does not seem to correspond to a pendular movement in KWU type reactors.
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Categorías UNESCO
Palabras clave
OMA, FDD, EFDD, Beam Mode, ruido electrónico, reactor PWR
Citación
Centro
E.T.S. de Ingenieros Industriales
Departamento
Mecánica