Numerical and experimental analysis of the impact of a nuclear spent fuel cask (original) (raw)
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Dynamic and quasi-static FE calculation of impact from 9 metre drop of spent fuel transport cask
Packaging, Transport, Storage & Security of Radioactive Material, 2009
The drop from 9 m height onto a rigid target is one of the required proofs of safety for packages of radioactive materials. Direct dynamic finite element method (FEM) calculations and combined two step analytical quasi-static finite element (FE) calculations are both applied for the simulation of a 9 m drop test. This paper gives a comparative example of both approaches for the 9 m side drop simulation of the spent fuel transport cask with wood filled impact limiter. The model for dynamic FEM consists of cask body and impact limiter. Detailed material properties and geometry descriptions from each component of the impact limiter are required. The results (stress fields in the cask body) are obtained directly from the calculation. The combined method provides as intermediate results the force-deformation characteristic of impact limiter. The maximum impact limiter force determined by the law of energy conservation during the drop is then-in a second step-applied on the cask body in a quasi-static FE model in order to calculate the stresses. In this paper, the rigid body deceleration and the maximum stress in the middle of the cask body are used for the comparison between the dynamic FEM and the combined method. Similar maximum rigid body deceleration-time curves were obtained by both methods for the horizontal 9 m free fall. Concerning the stress in the cask body the dynamic FEM results oscillate about values calculated by the combined quasi-static approach. If the combined quasi-static approach is used in the safety assessment of a cask, a suitable factor has to be applied on its results to take into account the additional dynamic effects.
The 9 meter drop onto an unyielding target is one of the important mechanical tests within the safety assessment of transport casks for radioactive material. In general, the cask is equipped with impact limiters to reduce the dynamic load on the cask body by absorbing a major part of the kinetic energy. The impact limiters are often made of wood or aluminium. In this study an elastic-plastic material model with volume change was used to describe the stress-strain behaviour of wood found in crush tests. For aluminium, an elastic-incremental plastic material model with Cowper-Symonds parameters for strain rate depending material hardening was used to model the adiabatic stress-strain relations measured at specimens at constant ambient temperature. Hereafter simulations with a sophisticated finite element model were carried out and compared with different drop tests. Four drop tests of a half-scale cask model equipped with wood and aluminium impact limiters with different drop positions were selected to investigate the impact limiter behaviour during a 9 meter drop test. All drop tests were simulated with the same FE mesh but under different boundary and initial conditions.
Annals of Nuclear Energy, 2010
In Part 1 of this study, an advanced numerical simulation method was proposed to investigate the impact characteristics of the KN-18 spent nuclear fuel (SNF) transport cask recently developed in Korea and verified against the experimental results. In this study, sensitivity analyses are carried out using the proposed numerical simulation method to investigate the effects of the various modeling and design parameters, such as material model assumption, modeling methodology, analytical assumptions, and design variables that can affect the impact characteristics of a cask and the accuracy of the numerical results. These parametric analyses were also performed to provide a basis for correlations with test results that is closer to reality than merely conservative as a means of benchmarking the numerical models. In addition, the parametric analysis results are compared against the experimental results, and the sensitivities of each parameter are summarized to provide references for the future design and analysis of SNF transport casks.
Simulation of 9 m drop test of the cask for transport of radioactive material
The paper deals with finite element simulation of drop tests of the steel cask designed for transport of radioactive waste. Two simulations of hypothetical accident conditions defined as drops of the cask from height of 9 meters are described and results are analyzed for purposes of the cask qualification. The main attention is devoted to procedures and methods of evaluation of results.
Slovak Journal of Civil Engineering, 2010
Deterministic and probabilistic analysis of damping device resistance under impact loads from nuclear fuel container drop This paper presents a deterministic and probabilistic solution of damping devices for the protection of the reinforced concrete structure of a nuclear power plant (NPP) from impact loads from a container of nuclear fuel of the type TK C30 drop. The finite element idealization of the building structure is used in space. The interaction soil-structure, as well as the fluid-structure of the deactivated basin is considered in space. A steel pipe damper system is proposed for the dissipation of the kinetic energy of the container in free fall. The Newmark integration method is used for the solution of the dynamic equations. The sensitivity and probabilistic analysis of the damping devices was realized using the AntHILL and ANSYS software.
Containment structures are designed not only to provide leak tight barrier against release of radioactivity but also play a role in ensuring that it can withstand the impact load from projectile or missile impacts or internal plant accidents. In assessing the containment structures of nuclear power plants, predicting the characteristics of impact resistance in relation to design and safety considerations is relevant. The impact may result from missiles, aircraft crash, and internal accidents. Therefore the impact resistance of the concrete should be known, for design and safety of the containment structures. Here an attempt has been made to work out the analysis of the reinforced concrete target due to an impact in terms of penetration, spalling, scabbing and perforation. The experiments done by Sugano et al have been simulated in the present analysis. The results from present finite element analysis are then compared with the experimental results as well as empirical/semi-empirical...
2020
During the transportation of fuel elements, the cask has to provide shielding to protect workers, the public and the environment against the effects of radiation, to prevent an unwanted chain reaction, damage caused by heat and also to provide protection against dispersion of the contents. In order to standardize the design of fuel assembly transportation devices by numerical analysis, a set of dynamic analyzes was conducted to converge in a representative way the phenomena found in the drop tests used in the project qualification. Thus, this paper aims to present and discuss updated recommendations for contacts, material models and general configurations in three benchmarks. These benchmarks represent the phenomena found in numerical simulations of drop trials. Moreover, they are important to obtain an adequate correlation with the lowest possible use of computational resources. From the simulations, it was possible to observe the influence of an analysis carried out in plane strai...
Impact loading of a space nuclear powerplant.PDF
Preferred formulation of the problem in two space dimensions are described for solving the three fundamental equations of mechanics (conservation of mass, conservation of momentum, and conservation of energy). Models of the behavior of materials provide the closure to the three fundamentals equations for applications to problems in compressible fluid flow and solid mechanics. Models of fracture and damage are described. A caloric model of the equation of state is proposed to describe thermodynamic properties of solid materials with the phase transitions. Two-dimensional problems of a high-velocity impact of a space nuclear propulsion system reactor are solved. High-velocity impact problems of destruction of reactor are solved for the two cases: 1) at its crash landing on the Earth surface (the impact velocity being up to 400 m/s); 2) at its impact (with velocity up to 16 km/s) with the space debris fragments.
Impact stress reduction by shell splitting in cask for transporting radioactive material
Annals of Nuclear Energy, 2015
Casks designed for transporting radioactive material are mandated to withstand drop from specific heights on hard ground. The maximum internal stress in the shell of the cask after such an impact needs to be as low as possible to ensure safety of the material being transported. This paper investigates the concept of splitting the shell of the radioactive transport container into multiple layers to reduce these stresses after impact. Different geometrical configurations which are likely to be encountered while designing such containers have been studied through plane 2D and 3D finite element analysis and the efficacy of this idea has been explored on each of them. Considerable reduction of stress has been reported and an explanation based on elastic deformation of layered beams has been suggested. Simulations on a cask with the currently prevalent design also show the benefit of implementing this idea.