Publicación: Development of a methodology to estimate the statistical SDR uncertainty with R2S-UNED
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2021
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info:eu-repo/semantics/openAccess
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Resumen
The 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.
Descripción
The registered version of this article, first published in “Fusion Engineering and Design, Volume 168, 2021", is available online at the publisher's website: Elsevier, https://doi.org/10.1016/j.fusengdes.2021.112696
La versión registrada de este artículo, publicado por primera vez en “Fusion Engineering and Design, Volume 168, 2021", está disponible en línea en el sitio web del editor: Elsevier, https://doi.org/10.1016/j.fusengdes.2021.112696
Categorías UNESCO
Palabras clave
Rigorous-two-steps, Uncertainty propagation, Monte carlo, Shutdown dose rate
Citación
J. Alguacil, P. Sauvan, J.P. Catalan, J. Sanz, Development of a methodology to estimate the statistical SDR uncertainty with R2S-UNED, Fusion Engineering and Design, Volume 168, 2021, 112696, ISSN 0920-3796, https://doi.org/10.1016/j.fusengdes.2021.112696
Centro
Facultades y escuelas::E.T.S. de Ingenieros Industriales
Departamento
Ingeniería Energética