Thermal creep effects of aluminum alloy cladding on the irradiation-induced mechanical behavior in U-10Mo/Al monolithic fuel plates

Jian, Xiaobin,Ding, Shurong Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.4

Three-dimensional finite element simulations are implemented for the in-pile thermo-mechanical behavior in U-Mo/Al monolithic fuel plates with different thermal creep rates of cladding involved. The numerical results indicate that the thickness increment of fuel foil rises with the thermal creep coefficient of cladding. The maximum Mises stress of cladding is reduced by ~85% from 344 MPa on the 98.0^th day when the creep coefficient of cladding increases from 0.01 to 10.0, due to its equivalent thermal creep strain enlarged by 3.5 times. When the thermal creep coefficient of Aluminum cladding increases from 0 to 1.0, the maximum mesoscale stress of fuel foil varies slightly. At the same time, the peak mesoscale normal stress of fuel foil can reach 51 MPa on the 98.0^th day for the thermal creep coefficient of 10, which increases by 60.3% of that with the thermal creep un-occurred in the cladding. The maximum through-thickness creep strain components of fuel foil differ slightly for different thermal creep coefficients of cladding. The dangerous region of fuel foil becomes much closer to the heavily irradiated side when the creep coefficient of cladding becomes 10.0. The creep performance of Aluminum cladding should be optimized for the integrity of monolithic fuel plates.

Effects of sizes and mechanical properties of fuel coupon on the rolling simulation results of monolithic fuel plate blanks

Xiangzhe Kong,Shurong Ding,Hongyan Yang,Xiaoming Peng 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.8

High-density UMo/Zr monolithic nuclear fuel plates have a promising application prospect in high fluxresearch and test reactors. The solid state welding method called co-rolling is used for their fabrication. Hot co-rolling simulations for the composite blanks of UMo/Zr monolithic nuclear fuel plates are performed. The effects of coupon sizes and mechanical property parameters on the contact pressures betweenthe to-be-bonded surfaces are investigated and analyzed. The numerical simulation resultsindicate that 1) the maximum contact pressures between the fuel coupon and the Zircaloy cover existnear the central line along the plate length direction; as a whole the contact pressures decrease towardthe edges in the plate width direction; and lower contact pressures appear at a large zone near thecoupon corner, where de-bonding is easy to take place in the in-pile irradiation environments; 2) themaximum contact pressures between the fuel coupon and the Zircaloy parts increase with the initialcoupon thickness; after reaching a certain thickness value, the contact pressures hardly change, whichwas mainly induced by the complex deformation mechanism and special mechanical constitutive relationof fuel coupon; 3) softer fuel coupon will result in lower contact pressures and form interfaces beingmore out-of-flatness.

A mesoscale stress model for irradiated U – 10Mo monolithic fuels based on evolution of volume fraction/radius/internal pressure of bubbles

Xiaobin Jian,Xiangzhe Kong,Shurong Ding 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.6

Fracture near the Ue10Mo/cladding material interface impacts fuel service life. In this work, a mesoscalestress model is developed with the fuel foil considered as a porous medium having gas bubbles andbearing bubble pressure and surface tension. The models for the evolution of bubble volume fraction,size and internal pressure are also obtained. For a Ue10Mo/Al monolithic fuel plate under locationdependentirradiation, the finite element simulation of the thermo-mechanical coupling behavior isimplemented to obtain the bubble distribution and evolution behavior together with their effects on themesoscale stresses. The numerical simulation results indicate that higher macroscale tensile stressesappear close to the locations with the maximum increments of fuel foil thickness, which is intensivelyrelated to irradiation creep deformations. The maximum mesoscale tensile stress is more than 2 times ofthe macroscale one on the irradiation time of 98 days, which results from the contributions of considerablevolume fraction and internal pressure of bubbles. This study lays a foundation for the fracturemechanism analysis and development of a fracture criterion for Ue10Mo monolithic fuels.

Theoretical models of threshold stress intensity factor and critical hydride length for delayed hydride cracking considering thermal stresses

Jingyu Zhang,Jiacheng Zhu,Shurong Ding,Liang Chen,Wenjie Li,Hua Pang 한국원자력학회 2018 Nuclear Engineering and Technology Vol.50 No.7

Delayed hydride cracking (DHC) is an important failure mechanism for Zircaloy tubes in the demandingenvironment of nuclear reactors. The threshold stress intensity factor, KIH, and critical hydride length, lC ,are important parameters to evaluate DHC. Theoretical models of them are developed for Zircaloy tubesundergoing non-homogenous temperature loading, with new stress distributions ahead of the crack tipand thermal stresses involved. A new stress distribution in the plastic zone ahead of the crack tip isproposed according to the fracture mechanics theory of second-order estimate of plastic zone size. Thedeveloped models with fewer fitting parameters are validated with the experimental results for KIH andlC. The research results for radial cracking cases indicate that a better agreement for KIH can be achieved;the negative axial thermal stresses can lessen KIH and enlarge the critical hydride length, so its effectshould be considered in the safety evaluation and constraint design for fuel rods; the critical hydridelength lC changes slightly in a certain range of stress intensity factors, which interprets the phenomenonthat the DHC velocity varies slowly in the steady crack growth stage. Besides, the sensitivity analysis ofmodel parameters demonstrates that an increase in yield strength of zircaloy will result in a decrease inthe critical hydride length lC , and KIH will firstly decrease and then have a trend to increase with the yieldstrength of Zircaloy; higher fracture strength of hydrided zircaloy will lead to very high values ofthreshold stress intensity factor and critical hydride length at higher temperatures, which might be themain mechanism of crack arrest for some Zircaloy materials

Three-dimensional Numerical Simulation of Hydrogen-induced Multi-field Coupling Behavior in Cracked Zircaloy Cladding Tubes

Zhongjia Xia,Bingzhong Wang,Jingyu Zhang,Shurong Ding,Liang Chen,Hua Pang,Xiaoming Song 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.1

In the high-temperature and high-pressure irradiation environments, the multi-field coupling processes ofhydrogen diffusion, hydride precipitation and mechanical deformation in Zircaloy cladding tubes occur. Tosimulate this hydrogen-induced complex behavior, a multi-field coupling method is developed, with theirradiation hardening effects and hydride-precipitation-induced expansion and hardening effects involvedin the mechanical constitutive relation. The out-pile tests for a cracked cladding tube after irradiation aresimulated, and the numerical results of the multi-fields at different temperatures are obtained andanalyzed. The results indicate that: (1) the hydrostatic stress gradient is the fundamental factor to activatethe hydrogen-induced multi-field coupling behavior excluding the temperature gradient; (2) in the localcrack-tip region, hydrides will precipitate faster at the considered higher temperatures, which can befundamentally attributed to the sensitivity of TSSP and hydrogen diffusion coefficient to temperature. Themechanism is partly explained for the enlarged velocity values of delayed hydride cracking (DHC) at hightemperatures before crack arrest. This work lays a foundation for the future research on DHC.

Modelling of effective irradiation swelling for inert matrix fuels

Zhang, Jing,Wang, Haoyu,Wei, Hongyang,Zhang, Jingyu,Tang, Changbing,Lu, Chuan,Huang, Chunlan,Ding, Shurong,Li, Yuanming Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8

The results of effective irradiation swelling in a wide range of burnup levels are numerically obtained for an inert matrix fuel, which are verified with DART model. The fission gas swelling of fuel particles is calculated with a mechanistic model, which depends on the external hydrostatic pressure. Additionally, irradiation and thermal creep effects are included in the inert matrix. The effects of matrix creep strains, external hydrostatic pressure and temperature on the effective irradiation swelling are investigated. The research results indicate that (1) the above effects are coupled with each other; (2) the matrix creep effects at high temperatures should be involved; and (3) ranged from 0 to 300 MPa, a remarkable dependence of external hydrostatic pressure can be found. Furthermore, an explicit multi-variable mathematic model is established for the effective irradiation swelling, as a function of particle volume fraction, temperature, external hydrostatic pressure and fuel particle fission density, which can well reproduce the finite element results. The mathematic model for the current volume fraction of fuel particles can help establish other effective performance models.

Thermal-fluid-structure coupling analysis on plate-type fuel assembly under irradiation. Part-II Mechanical deformation and thermal-hydraulic characteristics

Li, Yuanming,Ren, Quan-yao,Yuan, Pan,Su, Guanghui,Yu, Hongxing,Zheng, Meiyin,Wang, Haoyu,Wu, Yingwei,Ding, Shurong Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect stress conditions, mechanical behaviors and thermal-hydraulic performance of the fuel assembly. This paper is the Part II work of a two-part study devoted to analyzing the complex unique mechanical deformation and thermal-hydraulic characteristics for the typical plate-type fuel assembly under irradiation effect, which is on the basis of developed and verified numerical thermal-fluid-structure coupling methodology under irradiation in Part I of this work. The mechanical deformation, thermal-hydraulic performance and Mises stress have been analyzed for the typical plate-type fuel assembly consisting of support plates under non-uniform irradiation. It was interesting to observe that: the plate-type fuel assembly including the fuel plates and support plates tended to bend towards the location with maximum fission rate; the hot spots in the fuel foil appeared at the location with maximum thickness increment; the maximum Mises stress of fuel foil was located at the adjacent location with the maximum plate thickness increment et al.

Thermal-fluid-structure coupling analysis for plate-type fuel assembly under irradiation. Part-I numerical methodology

Li, Yuanming,Yuan, Pan,Ren, Quan-yao,Su, Guanghui,Yu, Hongxing,Wang, Haoyu,Zheng, Meiyin,Wu, Yingwei,Ding, Shurong Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.5

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect its stress conditions, mechanical behavior and thermal-hydraulic performance. A reliable numerical method is of great importance to reveal the complex evolution of mechanical deformation, flow redistribution and temperature field for the plate-type fuel assembly under non-uniform irradiation. This paper is the first part of a two-part study developing the numerical methodology for the thermal-fluid-structure coupling behaviors of plate-type fuel assembly under irradiation. In this paper, the thermal-fluid-structure coupling methodology has been developed for plate-type fuel assembly under non-uniform irradiation condition by exchanging thermal-hydraulic and mechanical deformation parameters between Finite Element Model (FEM) software and Computational Fluid Dynamic (CFD) software with Mesh-based parallel Code Coupling Interface (MpCCI), which has been validated with experimental results. Based on the established methodology, the effects of non-uniform irradiation and fluid were discussed, which demonstrated that the maximum mechanical deformation with irradiation was dozens of times larger than that without irradiation and the hydraulic load on fuel plates due to differential pressure played a dominant role in the mechanical deformation.

Thermo-mechanical coupling behavior analysis for a U-10Mo/Al monolithic fuel assembly

Mao, Xiaoxiao,Jian, Xiaobin,Wang, Haoyu,Zhang, Jingyu,Zhang, Jibin,Yan, Feng,Wei, Hongyang,Ding, Shurong,Li, Yuanming Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.9

A typical three-dimensional finite element model for a fuel assembly is established, which is composed of 16 monolithic U-10Mo fuel plates and Al alloy frame. The distribution and evolution results of temperature, displacement and stresses/strains in all the parts are numerically obtained and analyzed with a self-developed code of FUELTM. The simulation results indicate that (1) the out-of-plane displacements of Al alloy side plates are mainly attributed to the bending deformations; (2) enhanced out-of-plane displacements appear in fuel plates adjacent to the outside Al plates, which results from the occurred bending deformations due to the applied constraints of outside Al plates; (3) an intense interaction of fuel foil with the cladding occurs near the foil edge, which appears more heavily in the fuel plates adjacent to the outside Al plates. The maximum first principal stresses in the fuel foil are similar for all the fuel plates and appear near the fuel foil edge; while, the through-thickness creep strains of fuel foil in the fuel plate near the central region of fuel assembly are larger, and the induced creep damage might weaken the fuel skeleton strength and raise the fuel failure risk.