Estimation of the chemical compositions and corresponding microstructures of AgInCd absorber under irradiation condition

Chen, Hongsheng,Long, Chongsheng,Xiao, Hongxing,Wei, Tianguo,Le, Guan Korean Nuclear Society 2020 Nuclear Engineering and Technology Vol.52 No.2

AgInCd alloy is widely used as neutron absorber in nuclear reactors. However, the AgInCd control rods may fail during service due to the irradiation swelling. In the present study, a calculational method is proposed to calculate the composition change of the AgInCd absorber. Calculated results show that neutron fluence has significant impact on the chemical compositions. Ag and In contents gradually decrease while Cd and Sn conversely increases from the center to the rim of AgInCd absorber due to the depression of neutron flux. The composition change at the surface is higher almost two times than that at the center. Based on the calculated compositions, six simulated AgInCdSn alloys were prepared and examined. With the increase of Cd and Sn, the simulated AgInCdSn alloys transform from a single fcc phase into the mixed fcc and hcp phases, and finally into the single hcp phase. The atomic volume of the hcp phase is obviously larger than the fcc phase. The fcc-hcp transformation results in considerable volume swelling of the AgInCd absorber. Moreover, the lattice parameters of the fcc and hcp phases gradually increase with Cd and Sn contents, which also can induce small volume swelling.

Modeling of pore coarsening in the rim region of high burn-up UO2 fuel

Hongxing Xiao,CHONGSHENG LONG 한국원자력학회 2016 Nuclear Engineering and Technology Vol.48 No.4

An understanding of the coarsening process of the large fission gas pores in the high burnupstructure (HBS) of irradiated UO2 fuel is very necessary for analyzing the safety andreliability of fuel rods in a reactor. A numerical model for the description of pore coarseningin the HBS based on the Ostwald ripening mechanism, which has successfullyexplained the coarsening process of precipitates in solids is developed. In this model, thefission gas atoms are treated as the special precipitates in the irradiated UO2 fuel matrix. The calculated results indicate that the significant pore coarsening and mean pore densitydecrease in the HBS occur upon surpassing a local burn-up of 100 GWd/tM. The capabilityof this model is successfully validated against irradiation experiments of UO2 fuel, in whichthe average pore radius, pore density, and porosity are directly measured as functions oflocal burn-up. Comparisons with experimental data show that, when the local burn-upexceeds 100 GWd/tM, the calculated results agree well with the measured data.

CORROSION BEHAVIOR OF AUSTENITIC AND FERRITIC STEELS IN SUPERCRITICAL WATER

Luo, Xin,Tang, Rui,Long, Chongsheng,Miao, Zhi,Peng, Qian,Li, Cong Korean Nuclear Society 2008 Nuclear Engineering and Technology Vol.40 No.2

The general corrosion behavior of austenitic and ferritic steels(316L, 304, N controlled 304L, and 410) in supercritical water is investigated in this paper. After exposure to deaerated supercritical water at $480^{\circ}C$/25 MPa for up to 500 h, the four steels studied were characterized using gravimetry, scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction(XRD). The results show that the 316L steel with a higher Cr and Ni content has the best corrosion-resistance performance among the steels tested. In addition to the oxide layer mixed with $Fe_{3}O_{4}$ and $(Fe,Cr)_{3}O_{4}$ that formed on all the samples, a $Fe_{3}O_{4}$ loose outer layer was observed on the 410 steel. The corrosion mechanism of stainless steels in supercritical water is discussed based on the above results.

A model for calculating the irradiation swelling of AgInCd absorber in nuclear control rods

Hongsheng Chen,Hongxing Xiao,Chongsheng Long,Xuesong Leng Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.2

The actual swelling of AgInCd absorber might exceed the predicted swelling value after years of service in pressurized water reactors, and the chemical and microstructural changes of AgInCd absorber induced by transmutation reactions are the main reason for the swelling acceleration of AgInCd absorber. In the present study, a model for calculating the irradiation swelling of AgInCd absorber in nuclear control rods is developed according to chemical and microstructural changes of AgInCd absorber. In this model, the chemical compositions of AgInCd absorber as a function of the thermal neutron fluence are firstly calculated, and then the volume of AgInCd absorber after irradiation is obtained on the basis of the crystallographic parameters of phases in the AgInCd absorber, and the irradiation swelling of AgInCd absorber is finally calculated. The crystallographic parameters can be obtained by preparing the simulated AgInCd alloys and fitting the experimental data. The model calculating results of irradiation swelling are in good agreement with the actual swelling data in literature. More importantly, the present model can well explain the EPRI results of the acceleration in the diametral swelling rate above 6-8 × 10²⁰ n/cm² and the decrease in the diametral swelling rate above about 2 × 10²¹ n/cm².

Atomistic simulations of nanocrystalline U0.5Th0.5O2 solid solution under uniaxial tension

Hongxing Xiao,Xiaomin Wang,CHONGSHENG LONG,Xiaofeng Tian,Hui Wang 한국원자력학회 2017 Nuclear Engineering and Technology Vol.49 No.8

Molecular dynamics simulations were performed to investigate the uniaxial tensile properties of nanocrystalline U0.5Th0.5O2 solid solution with the Borne-Mayere-Huggins potential. The results indicated that the elastic modulus increased linearly with the density relative to a single crystal, but decreased with increasing temperature. The simulated nanocrystalline U0.5Th0.5O2 exhibited a breakdown in the HallePetch relation with mean grain size varying from 3.0 nm to 18.0 nm. Moreover, the elastic modulus of U1-yThyO2 solid solutions with different content of thorium at 300 K was also studied and the results accorded well with the experimental data available in the literature. In addition, the fracture mode of nanocrystalline U0.5Th0.5O2 was inclined to be ductile because the fracture behavior was preceded by some moderate amount of plastic deformation, which is different from what has been seen earlier in simulations of pure UO2.

CORROSION BEHAVIOR OF NI-BASE ALLOYS IN SUPERCRITICAL WATER

QIANG ZHANG,RUI TANG,CONG LI,XIN LUO,CHONGSHENG LONG,KAIJU YIN 한국원자력학회 2009 Nuclear Engineering and Technology Vol.41 No.1

Corrosion of nickel-base alloys (Hastelloy C-276, Inconel 625, and Inconel X-750) in 500 °C, 25 MPa supercritical water (with 10 wppb oxygen) was investigated to evaluate the suitability of these alloys for use in supercritical water reactors. Oxide scales formed on the samples were characterized by gravimetry, scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that, during the 1000 h exposure, a dense spinel oxide layer, mainly consisting of a fine Cr-rich inner layer (NiCr2O4) underneath a coarse Fe-rich outer layer (NiFe2O4), developed on each alloy. Besides general corrosion, nodular corrosion occurred on alloy 625 possibly resulting from local attack of ” clusters in the matrix. The mass gains for all alloys were small, while alloy X-750 exhibited the highest oxidation rate, probably due to the absence of Mo.

CORROSION BEHAVIOR OF NI-BASE ALLOYS IN SUPERCRITICAL WATER

Zhang, Qiang,Tang, Rui,Li, Cong,Luo, Xin,Long, Chongsheng,Yin, Kaiju Korean Nuclear Society 2009 Nuclear Engineering and Technology Vol.41 No.1

Corrosion of nickel-base alloys (Hastelloy C-276, Inconel 625, and Inconel X-750) in $500^{\circ}C$, 25MPa supercritical water (with 10 wppb oxygen) was investigated to evaluate the suitability of these alloys for use in supercritical water reactors. Oxide scales formed on the samples were characterized by gravimetry, scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that, during the 1000h exposure, a dense spinel oxide layer, mainly consisting of a fine Cr-rich inner layer ($NiCr_{2}O_{4}$) underneath a coarse Fe-rich outer layer ($NiFe_{2}O_{4}$), developed on each alloy. Besides general corrosion, nodular corrosion occurred on alloy 625 possibly resulting from local attack of ${\gamma}$" clusters in the matrix. The mass gains for all alloys were small, while alloy X -750 exhibited the highest oxidation rate, probably due to the absence of Mo.

CORROSION BEHAVIOR OF NI-BASE ALLOYS IN SUPERCRITICAL WATER

Zhang, Qiang,Tang, Rui,Li, Cong,Luo, Xin,Long, Chongsheng,Yin, Kaiju Korean Nuclear Society 2009 Nuclear Engineering and Technology Vol.41 No.2

Corrosion of nickel-base alloys (Hastelloy C-276, Inconel 625, and Inconel X-750) in $500^{\circ}C$, 25 MPa supercritical water (with 10 wppb oxygen) was investigated to evaluate the suitability of these alloys for use in supercritical water reactors. Oxide scales formed on the samples were characterized by gravimetry, scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results indicate that, during the 1000 h exposure, a dense spinel oxide layer, mainly consisting of a fine Cr-rich inner layer ($NiCr_2O_4$) underneath a coarse Fe-rich outer layer ($NiFe_2O_4$), developed on each alloy. Besides general corrosion, nodular corrosion occurred on alloy 625 possibly resulting from local attack of ${\gamma}"$ clusters in the matrix. The mass gains for all alloys were small, while alloy X-750 exhibited the highest oxidation rate, probably due to the absence of Mo.