Persona:
López Ochoa, Víctor

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vlopez@ind.uned.es
ORCID
0000-0002-0668-3338
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López Ochoa
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Víctor
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2021 - 20244
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Mostrando 1 - 4 de 4
  • Miniatura
    Publicación
    Sensitivity to nuclear data of the design of the IFMIF-DONES beam dump
    (Frontiers, 2023-06-05) López Ochoa, Víctor; Ogando Serrano, Francisco M.; Sauvan, Patrick
    During the commissioning and start-up phases of IFMIF-DONES, the 40MeV deuteron beam will be stopped in a conical beam stopper made of copper, giving rise to intense neutron fields. Accurate coupled deuteron-neutron transport simulations are required in order to prevent the potential risks to the workers andequipmentinvolved. However, theexperimental data concerning the neutron emission under these circumstances is scarce and limited to a particular range of energies. Different deuteron nuclear data libraries such as JENDL-5 and special f iles of TENDL-2021 exhibit some differences on the spectrum of the emitted neutrons. The differences are present in thehigh energy tails, beyond the available experimental data. Calculations of the prompt neutron fields have been performed employing both deuteron data libraries, as well as employing an estimation of the neutron energy-angle distribution derived from experimental data at different irradiation energies. Even though the high energy tails represent a small part of the flux, they have a major impact on the dose rates. The disparity of the results evinces large uncertainties in the IFMIF-DONES beam dump design process. Further experiments are required in order to resolve the differences among nuclear data libraries and reduce the uncertainty.
  • Miniatura
    Publicación
    Shutdown dose rates calculations due to light ions induced activation using D1S methodology
    (ELSEVIER, 2021-06-01) López Ochoa, Víctor; Sauvan, Patrick; Ogando Serrano, Francisco M.
    One of the main radiation sources in nuclear facilities, which cause exposure of workers conducting maintenance activities, is the decay of radioactive nuclides. The determination of these radiation fields usually requires both radiation transport and activation calculations. The Direct-one-Step methodology allows obtaining response functions associated to the residual activity with a single Monte Carlo transport calculation. This methodology has been widely used in the analysis of nuclear fusion installations like ITER, JET or DEMO, proving to be a very efficient tool for Shutdown Dose Rate calculations. Yet, this methodology has only been applied when the material activation is due to the interaction with a neutron flux. Since, typically, in particle accelerators the D1S assumptions are met, it is proposed in this work to apply the D1S methodology to material activation induced by light ions interactions, namely: protons and deuterons. This methodology has been implemented in the D1SUNED code. In order to show its performance, the D1SUNED has been used to calculate the SDR in the LIPAc geometry, resulting in a good convergence with a reference calculation.
  • Miniatura
    Publicación
    ITER full model in MCNP for radiation safety demonstration
    (Nature Research, 2024-10-03) Juárez Mañas, Rafael; Belotti, Mario; Kolsek, Aljaz; López Ochoa, Víctor; Alguacil Orejudo, Javier; Pedroche Sánchez, Gabriel; López Revelles, Antonio Jesús; Martínez Albertos, Pablo; De Pietri, Marco; Guijosa Araez, Pol; Tonqueze, Y. Le; Loughlin, M. J.; Polunovskiy, E.; Pampin, R.; Fabbri, M.; Sanz, J.
    The development of nuclear fusion as a safe and virtually limitless power source is receiving growing attention in the context of looming energy crisis and climate change. ITER project stands as the flagship international initiative and is advancing steadily. The construction of the Tokamak Complex is nearly finished, and the assembly of core components has begun on site. Simultaneously, the design is being finalized, and the safety case is becoming more concrete. Current approaches to radiation safety demonstration using 3D nuclear analysis with the Monte Carlo code MCNP require sophisticated artifacts to sew together simulations in separate models for the Tokamak and the rest of the facility. This results in cumbersome studies and, consequently, challengeable conclusions. To address this issue, we have built the an integral MCNP model of the ITER facility: the ITER full model. Along with improvements to the D1SUNED code, we illustrate its computational practicality and pertinence in two meaningful simulations for ITER safety case. This work represents the culmination of a two-decade-long effort of ITER modelling aiming to demonstrate adequate radiation safety. Beyond supporting the remaining design tasks, this model simplifies the corresponding 3D nuclear analysis and improves the robustness of the ITER safety case.
  • Miniatura
    Publicación
    Beam-facing material selection for mitigation of residual doses in the HEBT of IFMIF-DONES
    (ELSEVIER, 2024) Ogando Serrano, Francisco M.; Macià, Llorenç; López Ochoa, Víctor; Podadera Aliseda, Ivan; Sánchez Herranz, Daniel; https://orcid.org/0000-0001-5599-336X; https://orcid.org/0000-0002-3459-4631; https://orcid.org/0000-0001-7090-2550
    IFMIF-DONES will be an irradiation facility based on a 40 MeV deuteron accelerator. Unavoidable beam losses along the accelerator result in deuterium interactions with the beam facing materials of the vacuum beam pipe, some of them leading to material activation. The initial design of the beam pipe was based on stainless steel, but an evaluation of the residual doses from the pipe showed high values after operation of the accelerator. The accelerator beam line must be periodically maintained, and excessive cooling times for reaching acceptable dose levels may result in poorer availability of the facility. A deeper study of the High Energy Beam Transport line (HEBT) showed that a direct reaction between deuterons and iron in steel resulted in the production of Co-56, with a half-life of 77 days. This radioisotope is the main source of the radiation and makes it impractical to wait for a proper attenuation of the radiation field. A redesign of beam line elements has been performed to avoid the presence of stainless steel as a beam facing material and to replace it with aluminum where possible, resulting in faster decay of residual doses. This work contains a summary of the nuclear analysis performed for the computation of residual doses with stainless steel beam pipe, stressing the uncertainties of the calculations, based on the limited availability of nuclear data for the relevant nuclear reaction Fe56 (d,2n). The proposed replacement of element materials is also described, and an updated nuclear analysis shows the reduction of residual radiation, and its impact on possible maintenance operations.