Persona: Sauvan, Patrick
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psauvan@ind.uned.es
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0000-0002-9128-8817
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Sauvan
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Patrick
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Publicación GEOUNED: A new conversion tool from CAD to Monte Carlo geometry(Elsevier, 2024-05-30) Catalán Pérez, Juan Pablo; Sauvan, Patrick; García, J.; Alguacil Orejudo, Javier; Ogando Serrano, Francisco M.; Sanz Pérez, JavierThe GEOUNED code is specifically designed to convert CAD models, defined using the B-rep approach, into MC radiation transport models, defined using the CSG approach, and vice versa from MC to CAD. This code incorporates standard features commonly found in conversion tools, including decomposition, conversion, and automatic void generation. Additionally, it introduces innovative features, mainly in the automatic void generation part, which are described in this article. GEOUNED has demonstrated successful application in highly detailed 3D models used in fusion neutronics, which are known for their complex geometries, particularly those utilized in ITER. The article includes examples showcasing GEOUNED’s performance in these challenging models, as well as custom applications that highlight its flexibility in addressing non-standard problems. The code is open-source and utilizes Open CASCADE as the geometry engine, with FreeCAD serving as the Python API.Publicación Construction of GVR weight windows maps from very low density transport simulations(Elsevier, 2024-05) Farga Niñoles, Gonzalo; Ogando Serrano, Francisco M.; Alguacil Orejudo, Javier; Sauvan, PatrickFusion-related facilities present relevant neutron radiation fields even after penetrating through a considerable thickness of shielding material. Neutronic analyses performed via Monte Carlo codes, then, need Global Variance Reduction (GVR) techniques so that low statistical uncertainty is reached efficiently throughout the geometry. Mesh-based Weight Windows is a flexible methodology used extensively for variance reduction purposes, both for Local and Global Variance Reduction. Purely stochastic GVR methodologies based on Weight Windows usually construct weight maps so that they are proportional to the forward particle flux, which is unknown a priori. Therefore, an iterative cycle is established. In each iteration, a weight map is obtained from the forward flux that allows the next iteration to reach further into the geometry, until all of it is populated. However, this iterative cycle may take a considerable amount of computer time, as many iterations are needed to fully populate the geometry. An alternative to achieve relevant penetration in a single iteration is to perform calculations at very low densities. However, a reconstruction method is needed to estimate the flux at the real density. This work studies a scheme to reconstruct the fluxes from low density calculations and compares it to already existing techniques.Publicación A full and heterogeneous model of the ITER tokamak for comprehensive nuclear analyses(Nature Research, 2021-01-04) Juárez Mañas, Rafael; Pedroche Sánchez, Gabriel; Loughlin, M. J.; Pampin, R.; Martínez Albertos, Pablo; De Pietri, Marco; Alguacil Orejudo, Javier; Ogando Serrano, Francisco M.; Sauvan, Patrick; López Revelles, Antonio Jesús; Kolsek, Aljaz; Polunovskiy, E.; Fabbri, M.; Sanz Pérez, JavierITER is the flagship project, conceived as an experiment to select and develop the technologies for the first demonstration reactor, DEMO. Nuclear analysis is a core discipline in support of the design, commissioning and operation of the machine. To date it has been conducted with increasingly detailed partial models, which represented toroidal segments of the tokamak. However, the limitations of this methodology became evident as estimates of quantities relevant to design, safety and operation showed unquantifiable uncertainties, which is a risk. Here, we present a detailed and realistic 360° MCNP model of the ITER tokamak called E-lite. We demonstrate the model’s usability and practicality. Two examples are used to illustrate qualitatively and quantitatively how it solves previously intractable problems with marked benefits for the future nuclear analysis of ITER, with applications to DEMO and future reactors. E-lite constitutes a milestone in the field of nuclear analysis in terms of realism in the evaluation of key quantities.Publicación D1SUNED system for the determination of decay photon related quantities(Elsevier, 2019-11-18) Sauvan, Patrick; Juárez Mañas, Rafael; Pedroche Sánchez, Gabriel; Alguacil Orejudo, Javier; Catalán Pérez, Juan Pablo; Ogando Serrano, Francisco M.; Sanz Pérez, JavierThe neutron fields alter the radioactive inventory of the irradiated materials leading to subsequent decay photon fields. In some cases, these fields are of relevance either intended or undesired, normally involving safety and economics aspects. The determination of these fields can be of paramount complexity if high spatial resolution is required. The determination of these fields requires both radiation transport and activation calculations. The Direct-one-Step methodology, under the assumption that the radioactive inventory activity is lineal with the neutron flux, can address the problem with only one coupled neutron-photon transport calculation. In this paper the D1SUNED code for the calculation of decay photon field and related quantities using D1S methodology is presented. Calculation capabilities including the determination of 3D decay photon sources, filtering options, and other relevant features are presented. In terms of computational load, D1SUNED, which is based on MCNP5 code, presents improvements with respect to MCNP. It can save a 79% of the RAM memory used to store the geometry, a 98% of the loading time, and an acceleration of a factor two by controlling the decay photon emission, boosting the simulations for ITER-like problems. D1SUNED has been validated with the FNG benchmark experiment considering the null hypothesis rejection test and the C/E ratio with very positive results. As a consequence, D1SUNED has become a reference tool for the design of ITER, and other relevant nuclear fusion facilities.Publicación Development of a methodology to estimate the statistical SDR uncertainty with R2S-UNED(ELSEVIER, 2021) Alguacil Orejudo, Javier; Catalán Pérez, Juan Pablo; Sanz Gozalo, Javier; Sauvan, Patrick; https://orcid.org/0000-0002-9128-8817The Rigorous-Two-Steps (R2S) is one of the most useful methods to estimate the Shutdown Dose Rate (SDR). The most advanced R2S tools couple neutron and photon transport, which are often simulated using Monte Carlo (MC) codes, through an activation simulation using mesh-based techniques to improve the spatial resolution of the neutron flux and the decay gamma source. One of the problems of the methodology is that the statistical uncertainty of the neutron flux due to the MC method used by the transport codes is not considered by most R2S implementations. Consequently, larger tolerance must be assumed affecting to the design of the nuclear facilities. This article describes a scheme allowing the calculation of the SDR statistical uncertainty without any additional assumptions than those used in the R2S methodology. The approach proposed in this article is suitable for cell- and mesh-based R2S implementations. In this work, the methodology was implemented in the R2S-UNED code. The accurate application of the methodology requires the full the neutron flux uncertainty (covariance matrix) as input data. MCNP was modified to calculate this matrix, although, it cannot be calculated for most of the realistic R2S simulations due to its size. If that is the situation, we propose a guideline to reduce the size of the covariance matrix to be calculated according to its element contribution to the SDR. When this guideline cannot be applied, the methodology still allows calculating the upper and lower SDR uncertainty bounds. In this article, the guideline is applied to the calculation of the SDR uncertainty in the computational benchmark of ITER. In addition, we also study the possible impact of the neutron flux correlation degree on the SDR uncertainty in this benchmark.