Uncertainty Quantification on Spent Nuclear Fuel with LMC

The recently developed method Lasso Monte Carlo (LMC) for uncertainty quantification is applied to the characterisation of spent nuclear fuel. The propagation of nuclear data uncertainties to the output of calculations is an often required procedure in nuclear computations. Commonly used methods such as Monte Carlo, linear error propagation, or surrogate modelling suffer from being computationally intensive, biased, or ill-suited for high-dimensional settings such as in the case of nuclear data. The LMC method combines multilevel Monte Carlo and machine learning to compute unbiased estimates of the uncertainty, at a lower computational cost than Monte Carlo, even in high-dimensional cases. Here LMC is applied to the calculations of decay heat, nuclide concentrations, and criticality of spent nuclear fuel placed in disposal canisters. The uncertainty quantification in this case is crucial to reduce the risks and costs of disposal of spent nuclear fuel. The results show that LMC is unbiased and has a higher accuracy than simple Monte Carlo.Comment: Conference paper from the 12th International Conference on Nuclear Criticality Safety (ICNC), Sendai, Japan, October 2023. Submitted to the Arxiv with the permission of the conference organiser

Lasso Monte Carlo, a Novel Method for High Dimensional Uncertainty Quantification

Uncertainty quantification (UQ) is an active area of research, and an essential technique used in all fields of science and engineering. The most common methods for UQ are Monte Carlo and surrogate-modelling. The former method is dimensionality independent but has slow convergence, while the latter method has been shown to yield large computational speedups with respect to Monte Carlo. However, surrogate models suffer from the so-called curse of dimensionality, and become costly to train for high-dimensional problems, where UQ might become computationally prohibitive. In this paper we present a new technique, Lasso Monte Carlo (LMC), which combines surrogate models and the multilevel Monte Carlo technique, in order to perform UQ in high-dimensional settings, at a reduced computational cost. We provide mathematical guarantees for the unbiasedness of the method, and show that LMC can converge faster than simple Monte Carlo. The theory is numerically tested with benchmarks on toy problems, as well as on a real example of UQ from the field of nuclear engineering. In all presented examples LMC converges faster than simple Monte Carlo, and computational costs are reduced by more than a factor of 5 in some cases

Fast Uncertainty Quantification of Spent Nuclear Fuel with Neural Networks

The accurate calculation and uncertainty quantification of the characteristics of spent nuclear fuel (SNF) play a crucial role in ensuring the safety, efficiency, and sustainability of nuclear energy production, waste management, and nuclear safeguards. State of the art physics-based models, while reliable, are computationally intensive and time-consuming. This paper presents a surrogate modeling approach using neural networks (NN) to predict a number of SNF characteristics with reduced computational costs compared to physics-based models. An NN is trained using data generated from CASMO5 lattice calculations. The trained NN accurately predicts decay heat and nuclide concentrations of SNF, as a function of key input parameters, such as enrichment, burnup, cooling time between cycles, mean boron concentration and fuel temperature. The model is validated against physics-based decay heat simulations and measurements of different uranium oxide fuel assemblies from two different pressurized water reactors. In addition, the NN is used to perform sensitivity analysis and uncertainty quantification. The results are in very good alignment to CASMO5, while the computational costs (taking into account the costs of generating training samples) are reduced by a factor of 10 or more. Our findings demonstrate the feasibility of using NNs as surrogate models for fast characterization of SNF, providing a promising avenue for improving computational efficiency in assessing nuclear fuel behavior and associated risks

Development of a reference signal source to verify electromagnetic emissions test benches

Electromagnetic Compatibility (EMC) laboratories must ensure the quality of the tests they perform. In this regard, periodic calibrations and internal verifications should be carried out systematically to provide evidence that the test benches are in compliance with the standard requirements of measurement accuracy and instrumentation uncertainty. In particular, the electromagnetic emissions test consists of measuring the interference produced by the equipment under test (EUT). The failure or misfunctioning of any of the elements in the electromagnetic emissions test benches can lead to significant errors in the measurement results and, ultimately, to an incorrect assessment of the EUT compliance with regards to the standard emissions requirements. Just-before-test verifications are a mean for detecting such problems in the test benches, thus preventing the test laboratory from delivering wrong results to their clients. The Electromagnetic Compatibility Group from the UPC is aware of the importance of such calibrations and verification activities. Furthermore, GCEM-UPC is also a TECNIO agent, which means that it has been accredited by ?Generalitat de Catalunya? as an excellent, experienced, and high-quality technology service provider. In practice, this means that GCEM-UPC must demonstrate it has a quality assurance process and it is periodically audited. Therefore, GCEM-UPC is continuously improving the established EMC testing methods as well as developing new, better ones alongside with their required verification and calibration procedures. In this regard, this work aims at developing a reference signal source capable of generating specific waveform patterns with useful properties for accelerating the verification of electromagnetic emissions test benches. This implies designing and implementing an easy to use device ready for performing just-before-test verifications with a single apparatus.Los laboratorios de Compatibilidad Electromagnética (EMC) deben garantizar la calidad de los ensayos que realizan. En este sentido, se deben realizar calibraciones periódicas y verificaciones internas de manera sistemática para proporcionar evidencia de que los bancos de ensayo cumplen con los requisitos estándar de precisión e incertidumbre de la instrumentación. En particular, el ensayo de emisiones electromagnéticas consiste en medir la interferencia producida por el equipo sometido a ensayo (ESE). El fallo o mal funcionamiento de cualquiera de los elementos de los bancos de ensayos de emisiones electromagnéticas puede dar lugar a errores importantes en los resultados de la medida y, en última instancia, a una evaluación incorrecta del cumplimiento del ESE con respecto a los requisitos de emisiones estándar. Las verificaciones justo antes de la prueba son un medio para detectar tales problemas en los bancos de ensayo, evitando así que el laboratorio entregue resultados incorrectos a sus clientes. El Grupo de Compatibilidad Electromagnética de la UPC es consciente de la importancia de este tipo de actividades de calibración y verificación. Además, GCEM-UPC también es un agente TECNIO, lo que significa que ha sido acreditado por la Generalitat de Catalunya como proveedor de servicios tecnológicos de excelencia, con experiencia y de calidad. En la práctica, esto significa que GCEM-UPC debe demostrar que tiene un proceso de seguimiento de la calidad y que es auditado periódicamente al respecto. Por lo tanto, GCEM-UPC está mejorando continuamente los métodos de ensayo de EMC establecidos, así como desarrollando métodos nuevos y mejores junto con los procedimientos de verificación y calibración requeridos. En este sentido, este trabajo tiene como objetivo desarrollar una fuente de señal de referencia capaz de generar patrones de forma de onda específicos con propiedades útiles para acelerar la verificación de los bancos de ensayo de emisiones electromagnéticas. Esto implica diseñar e implementar un dispositivo fácil de usar listo para realizar verificaciones justo antes del ensayo con un único aparato.Els laboratoris de Compatibilitat Electromagnètica (EMC) han de garantir la qualitat dels assaigs que realitzen. En aquest sentit, s'han de realitzar calibracions periòdiques i verificacions internes de manera sistemàtica per proporcionar evidència que els bancs d'assaig compleixen amb els requisits estàndard de precisió i incertesa de la instrumentació. En particular, l'assaig d'emissions electromagnètiques consisteix a mesurar la interferència produïda per l'equip sotmès a assaig (ESE). La fallada o mal funcionament de qualsevol dels elements dels bancs d'assaigs d'emissions electromagnètiques pot donar lloc a errors importants en els resultats de la mesura i, en última instància, a una avaluació incorrecta de l'acompliment de l'ESE pel que fa als requisits de emissions estàndard. Les verificacions just abans de la prova són un mitjà per detectar aquests problemes en els bancs d'assaig, evitant així que el laboratori lliuri resultats incorrectes als seus clients. El Grup de Compatibilitat Electromagnètica de la UPC és conscient de la importància d'aquest tipus d'activitats de calibratge i verificació. A més, GCEM-UPC també és un agent TECNIO, el que significa que ha estat acreditat per la Generalitat de Catalunya com a proveïdor de serveis tecnològics d'excel·lència, amb experiència i de qualitat. A la pràctica, això significa que GCEM-UPC ha de demostrar que té un procés de seguiment de la qualitat i que és auditat periòdicament al respecte. Per tant, GCEM-UPC està millorant contínuament els mètodes d'assaig d'EMC establerts, així com desenvolupant mètodes nous i millors juntament amb els procediments de verificació i calibratge requerits. En aquest sentit, aquest treball té com a objectiu desenvolupar una font de senyal de referència capaç de generar patrons de forma d'ona específics amb propietats útils per accelerar la verificació dels bancs d'assaig d'emissions electromagnètiques. Això implica dissenyar i implementar un dispositiu fàcil d'utilitzar preparat per fer verificacions just abans de l'assaig amb un únic aparell