Shurong Ding

Mechanical behaviors of the dispersion nuclear fuel plates induced by fuel particle swelling and thermal effect II: Effects of variations of the fuel particle diameters

0022-3115/

Effects of Fission Heat and Fuel Swelling on the Thermal-mechanical Behaviors of Dispersion Fuel Elements

see front matter 2010 Elsevier B.V. A doi:10.1016/j.jnucmat.2009.12.012 * Corresponding author. E-mail address: dsr1971@163.com (S. Ding). In order to predict the irradiation mechanical behaviors of plate-type dispersion nuclear fuel elements, the total burnup is divided into two stages: the initial stage and the increasing stage. At the initial stage, the thermal effects induced by the high temperature differences between the operation temperatures and the room temperature are mainly considered; and at the increasing stage, the intense mechanical interactions between the fuel particles and the matrix due to the irradiation swelling of fuel particles are focused on. The large-deformation thermo–elasto-plasticity finite element analysis is performed to evaluate the effects of particle diameters on the in-pile mechanical behaviors of fuel elements. The research results indicate that: (1) the maximum Mises stresses and equivalent plastic strains at the matrix increase with the fuel particle diameters; the effects of particle diameters on the maximum first principal stresses vary with burnup, and the considered case with the largest particle diameter holds the maximum values all along; (2) at the cladding near the interface between the fuel meat and the cladding, the Mises stresses and the first principal stresses undergo major changes with increasing burnup, and different variations exist for different particle diameter cases; (3) the maximum Mises stresses at the fuel particles rise with the particle diameters. 2010 Elsevier B.V. All rights reserved.

Three-Dimensional Elastic-Plastic Analysis of the Interlaminar Stresses for the AS4/PEEK Composite Laminate with a Circular Hole

Thermal-mechanical behaviors of dispersion fuel elements were investigated through the finite element method. A representative plate element was developed for the thin fuel plate considering both the heat transfer conditions on its boundaries and the mutual actions of large numbers of fuel particles immersed. This research focuses on the thermal elastoplastic behaviors of the metal matrix. It was found that the thermal stresses could be of rather high level due to the high temperature working conditions, and that the temperature field was not homogeneous because of the fission heat; Irradiation induced swellings might further enhance the Mises stresses and the equivalent plastic strains very strongly. The heat transfer coefficients might have a large impact on the temperatures and the thermal-mechanical behaviors as well.

Irradiation-induced thermomechanical behavior in ADS composite fuel pellets: Mechanism and main influencing factors

Considering the thermoplastic AS4/PEEK laminate with a hole, the suitable finite element model is selected. Making use of the developed three-dimensional elastic-plastic finite element procedure, the numerical simulation of the mechanical behaviors for the thick AS4/PEEK composite laminate is carried out. The interlaminar stresses along the hole edge at different interfaces are obtained and presented. The critical locations prone to delamination are predicted. The research results indicate that delamination at the hole edge of the interface 90/0 tends to take place due to existence of maximum interlaminar tensile stresses together with larger interlaminar shear stresses; and the next critical position exists at the interface −45/90.

Qualitative Analysis of the Evolution Behaviors of Irradiation-Induced Point Defects

ABSTRACT The main irradiation-induced mechanisms are considered to simulate the multiscale in-pile behavior evolution in composite fuel pellets. The effects of the fission rate and particle volume fraction are investigated. The obtained results indicate that (1) the increased fission rate and particle volume fraction could effectively increase the maximum temperature and gas swelling and strengthen the mechanical interaction between the fuel particles and the matrix; and (2) at the initial stage, the thermal stress in the matrix mainly results from the temperature variation, while at higher burnup the combined effects of matrix creep and particle swelling are responsible for the stress evolution.

Simulation of the in-pile behaviors evolution in nuclear fuel rods with the irradiation damage effects

Point defects created by the collisions of high-energy particles and their subsequent evolutions form the foundation for all observed irradiation effects. Qualitative analysis is performed for the local and global behaviors of the planar system of nonlinear ordinary differential equations for the point defects balance model. The results indicated that the evolution behavior for the in-pile process is qualitatively very similar to the more simple annealing process, but very different from the degenerated systems that possess analytical solutions. However, quantitatively, irradiations in the in-pile process will shift the stable node away from the defect free state and change the local behaviors. A too strong irradiation may result in a nonphysical stable node and produce amorphous states, thus making the model inadequate.

Effects of Irradiation Growth on the Thermo-Mechanical Behaviors Evolution in Inert Matrix Fuel Elements

Based on the commercial computational software, a three-dimensional finite element model to simulate the thermo-mechanical behaviors in a nuclear fuel rod is established; By taking into consideration irradiation-swelling of the pellet and the irradiation damage effects in the cladding together with the coupling effects between the temperature field and the mechanical field, the user subroutines to define the special material performance and boundary conditions have been developed independently and validated. Three-dimensional numerical simulation of the thermo-mechanical coupling behaviors in a nuclear fuel rod is carried out, and the evolution rules of the important thermal and mechanical variables are obtained and analyzed. The research results indicate that: (1) the fuel pellets will be in contact with the cladding at high burnup, which will induce a strong mechanical interaction between them; (2) the irradiation creep effect plays an important role in the mechanical behavior evolution in the nuclear fuel rod.

Reliability analysis of dispersion nuclear fuel elements

Inert matrix fuel elements consisting of metal cladding and fuel meat with the fuel particles embedded into the inert matrix have higher lifetime compared to the traditional fuel elements used in the present nuclear plants. They have promising prospects to be used in the advanced nuclear reactors and disposal of nuclear wastes, and nowadays are widely used in the research and test reactors. In order to precisely predict their in-pile thermo-mechanical coupling behaviors, the relative simulation methods and several ABAQUS subroutines are built with the following irradiation damage effects involved as irradiation hardening in the metal matrix and cladding, irradiation swelling in the fuel particles and the irradiation growth effect for the cladding. Specially, the irradiation growth of the cladding is modeled in the way of anisotropic thermal expansion, and then its effects on the micro-thermo-mechanical behaviors in the inert matrix fuel elements can be investigated. The comparison of the results for the two cases with and without the irradiation growth shows: (1) irradiation growth will remarkably enhance the mechanical interactions in the cladding, such as the Mises stresses; (2) it will weaken the interaction between the fuel meat and the cladding; (3) the increment of the plate thickness will become a little smaller at low burnup, and then become larger at high burnup.© 2013 ASME