Costas de la Peña, Luis

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Costas de la Peña, Luis
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Costas de la Peña, Luis

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  • Publication
    Dynamic analysis of the nonlinear response of high density fuel storage racks
    (2016-08-30)
    Gonzalez Merino, Alberto 
    ;
    Costas de la Peña, Luis 
    ;
    González, Arturo 
    High Density Spent Fuel Storage racks are steel structures designed to hold nuclear spent fuel assemblies removed from the nuclear power reactor. Weighing around 60 tons, they are 5m high free-standing structures resting on the floor of a 12m depth pool and separated by only a few centimetres. Their underwater seismic response is a troubling safety issue, especially after Fukushima nuclear disaster. However, only limited basic guidelines have been provided as regulatory design criteria to date. The racks’ design deals with a very highly nonlinear behaviour, a transient dynamic response and a fluid-structure interaction problem. Industry is currently using available computer-aided finite element analysis software to solve the design problem in a cost-effective manner but some dispersion of results still exists. Hence, the nuclear regulatory authorities are requiring an evaluation of the current uncertainty associated to the assessment of rack displacements, rocking and maximum forces on supports. This paper discusses the main difficulties faced during the seismic analysis and presents an ad-hoc analysis methodology based on the hydrodynamic mass concept which takes advantage of a simplifying thermal analogy. The methodology, implemented in ANSYS FE Mechanical is hereby described for a reduced scale 2-rack model where the coupling effect of water in the dynamic motion of immersed racks is quantified and displacements and forces are provided. Finally, methodology assumptions are discussed and lessons learnt about the behaviour trends are summarized.
      327
  • Publication
    Sources of uncertainty in the seismic design of submerged free-standing racks
    (Elsevier, 2017-09-20)
    Gonzalez Merino, Alberto 
    ;
    Costas de la Peña, Luis 
    ;
    González, Arturo 
    Free-standing racks are 5 m tall structures that store spent fuel removed from the nuclear power reactor on the depths of a spent fuel pool. Rack units are arranged on the floor of this 12 meters deep pool separated by only a few centimeters. Their response to an earthquake event is a troubling safety issue as they are in submerged and free-standing conditions. Such a seismic analysis deals with a highly nonlinear behavior, a transient dynamic response and a fluid-structure interaction problem. To overcome these difficulties in a cost-effective manner, the current analysis methodology implements the hydrodynamic mass concept in commercial finite element analysis software. However, some dispersion of results still exists in the application of this ad-hoc methodology. This paper reviews the seven major sources of uncertainty inherent to the current analysis methodology together with the main challenges of the seismic analysis.
      298Scopus© Citations 5
  • Publication
    Uncertainties in seismic design of free-standing HDSFS Racks
    (2016-07-30)
    Gonzalez Merino, Alberto 
    ;
    Costas de la Peña, Luis 
    ;
    González, Arturo 
    High Density Spent Fuel Storage (HDSFS) racks are structures designed to hold nuclear spent fuel assemblies removed from the nuclear power reactor after having been irradiated. They are used in the first step of the waste management process, during the wet storage. The underwater seismic response of HDSFS racks is a troubling safety issue. Since they are 12 m submerged free standing multi-body structures loaded with radioactive fuel, their design remains as complex as crucial [1] [2]. The design deals with a Fluid-Structure Interaction (FSI) problem, a transient dynamic response and a very highly nonlinear behaviour. Several cost-effective industrial approaches have been used in these calculations to date, but some dispersion of results still exists. Therefore, the regulatory authorities are requiring an evaluation of the uncertainties in the methodology. Equipos Nucleares, S.A. (ENSA) is a worldwide expert in racks design and construction [3] and has recently launched a research project to improve the understanding of the phenomena. The latter is funded by the European Comision1 and aimed to identify, evaluate and reduce the uncertainties involved in the calculations. In this paper, the state of the art and the current sources of uncertainty are discussed.
      332