Factors Affecting the Swelling of Nuclear Fuels at High Temperatures

Models and computer codes, developed based on them, for simulating the swelling of uranium dioxide (BARS) and the stress-deformation state of a fuel element (SDS) under high-temperature irradiation are presented. It is shown that when developing a design for high-temperature fuel elements and validating their serviceability the quantitative indicator required for the swelling of uranium dioxide in the range ≥1400°C is the change in the external dimensions of the fuel caused by constant formation and growth of bubbles containing gaseous fission products during irradiation. The results of computational investigations using the models indicated are examined. These results eliminate the inconsistency of the data on the effect of the main operating parameters -the temperature and burnup -on the radiation characteristics and service life behavior of a fuel element. It is shown that the central channel in the fuel kernel and strengthening of the cladding improve the dimensional stability fuel elements.The cladding deformation caused by swelling of uranium dioxide is one of the main factors which limit the service life of high-temperature fuel elements of space nuclear power systems [1]. The computational-theoretical and experimental data on swelling under high-temperature irradiation are limited and contradictory [2]. According to some data, the swelling increases linearly with burnup, while according to other data the swelling saturates. Some works predict the existence of a maximum temperature dependence of swelling, while other works predict a sharp increase of swelling with temperature. These discrepancies could be due to the characteristic behavior of uranium dioxide due to the migration of bubbles of gaseous fission products and structural changes under high-temperature irradiation. The existing computational-theoretical models do not fully take into account the combined effect of these processes. The BARS statistical model of swelling (Bubble Analysis of Radiation Swelling of Fuel), which takes account of the characteristic behavior of bubbles of gaseous fission products and the change in the size and shape of uranium dioxide grains at high temperature, is proposed for analyzing the effect of the operational parameters on high-temperature swelling of uranium dioxide and to search for ways to increase the radiation resistance of oxide fuel.Reactor tests of samples [3] have made it possible to obtain data on free (not restrained by cladding) swelling of various modifications of uranium dioxide at high temperature and to develop a model of the deformation behavior of fuel elements SDS (Stress-Deformation State of Fuel Element). Fuel samples tested for density, oxygen content, grain size and shape, phase composition, and impurity content were used to obtain data on unrestrained swelling. This made it possible to determine the specific nature of the high-temperature radiation behavior of uranium dioxide and its modifications and to provide representative input data for the SDS codes. This factor and the possibility of...

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“…was observed to increase [9]. The change of the outer dimensions of the samples at high temperature was a linear function of burnup.…”

Section: Bars Computational Resultsmentioning

confidence: 82%

“….˜, below 1700°C fuel filled the central opening in the kernel and the deformation rate of the cladding continued to increase sharply [9]. Figures 10 and 11 display the computational results for the same fuel element with working temperature increased by 350°C (T cl = 1650°C, T c = 2065°C) with the same fuel burnup rate.…”

Section: Bars Computational Resultsmentioning

confidence: 97%

Simulation of high-temperature swelling of uranium dioxide and deformation behavior of a fuel element

Gontar

Nelidov

2007

At Energy

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“…The thermal expansion of UO 2 fuel particles relative to 300 K can be expressed as [24] Dl=l 0 ¼ À3:0289 Â 10 À4 þ 8:4217 Â 10 À6 ðT À 273Þ þ 2:1481…”

Section: The Constitutive Model Of Fuel Particlesmentioning

confidence: 99%

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

Ding

Wang

2010

Journal of Nuclear Materials

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“…For our FEM calculations, the following simplified relations [17][18][19] for UO 2 in PWRs will be used b gs V ¼ 1:122 Â 10 3 expðÀ1:645 Â 10 4 =ðT À 100ÞÞ; ð11Þ…”

Section: Fuel Particle Swellingmentioning

confidence: 99%

“…Due to the solid fission products and the gaseous fission products, the conductivities of the fuel particles degrade with increasing burnup [17]. The effects of the degraded conductivities of the fuel particles corresponding to burnup increase on the temperature variations are examined, shown as Fig.…”

Section: Effects Of Burnup On the Temperature Distributionmentioning

confidence: 99%

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

Ding

Yan

2009

Journal of Nuclear Materials

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Factors Affecting the Swelling of Nuclear Fuels at High Temperatures

Cited by 21 publications

References 19 publications

Simulation of high-temperature swelling of uranium dioxide and deformation behavior of a fuel element

Simulation of high-temperature swelling of uranium dioxide and deformation behavior of a fuel element

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

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

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