Helium diffusion in uranium and plutonium oxides

Gadolinium (Gd), in the form of gadolinia (Gd 2 O 3 ), has been used as integral burnable absorber to UO 2 fuel by different companies. Recently, alternative burnable absorber materials are under investigation. In this paper, the results of the study on the use of boron mixed in UO 2 as an integral burnable absorber are presented. Boron nitride was selected as the form of B to be added to UO 2 fuel based on the stability of B during sintering. Fuel performance analysis code FRAPCON-UNI, which is based on FRAPCON code and has the modifications for boron and helium generation and gasses release models, was used for the calculation of fuel performance. Helium generation was calculated using a model and the result was verified against ORIGEN calculation results. Gas release calculation was based on Forsberg Massih model and different characteristics of the gasses were considered. Power histories of maximum burnup rods (B rod, no B rod, and Gd rod) were selected from reactor physics data. The results indicated significant increases in rod internal pressure by 500 ppm boron addition at the end of life with minimum influence of a grain boundary boron fraction due to high diffusivity of helium and nitrogen.

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“…Helium behaviors in irradiated UO 2 and MOX fuel were investigated by different authors [15][16][17][18][19][20].…”

Section: Helium Releasementioning

confidence: 99%

“…Ronchi and Hiernaut [17] measured helium diffusivity from α-doped spent fuel samples. They used thermal annealing in a Knudsen-cell with a mass spectrometer, and obtained helium release fraction curves, but their diffusivities were not measured in isothermal environment.…”

Section: Helium Releasementioning

confidence: 99%

Gas releases and rod internal pressure of BN-added UO₂fuel

Jeong

Yang

2015

Journal of Nuclear Science and Technology

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“…The helium atom can be introduced into metals by two ways: α-decay of initial fissile atoms, and formation of heavier nuclides by neutron capture. 1 Much attention has been paid on the study of the behavior of helium in metals until today. The experimental and theoretical researches demonstrate that helium is mobile already in metals below room temperature.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of migration and diffusion mechanisms of helium in α-Be

Yang

et al. 2016

AIP Advances

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The behavior of interstitial helium in α-Be has been studied with first-principles method. It is found that the most favored position for helium is the basal octahedral (BO) site, closely followed by the basal tetrahedral (BT) site, in agreement with previous predictions. The interaction energy between the helium and the neighborhood Be atoms and the deformation energy of α-Be matrix are calculated. The feasible minimum-energy pathways (MEP) of interstitial helium atoms in α-Be matrix and the corresponding atomic structures of the saddle points associated with the each MEP are investigated. The temperature-dependent diffusion coefficients have also been predicted. It is confirmed that the interstitial helium diffuses two-dimensionally at low temperatures; however, it can diffuse three-dimensionally at higher temperatures. Besides, the microscopic parameters in the pre-factor and activation energy of the diffusion coefficients are obtained. Both diffusion coefficients are higher than the available experiment data, which may attribute to the fact that under real condition the diffusion is not free, i.e. the actual α-Be matric has various defects and impurities which heavily affect the diffusion of helium. Therefore, our theoretical prediction is the upper bound for helium diffusion in α-Be matrix.

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“…The diffusion of helium in UO 2 and MOX fuels has been measured [6][7][8][9][10] or calculated [11][12][13][14] by several researchers. However, bubble swelling by helium has not been studied sufficiently.…”

Section: Introductionmentioning

confidence: 99%

Dependence of vacancy concentration on morphology of helium bubbles in oxide ceramics

Matsunaga¹,

Sakamoto²,

Muta

et al. 2014

Journal of Nuclear Science and Technology

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Since the formation of helium bubbles degrades swelling property and thermal conductivity of minor actinide-containing mixed oxide (MA-MOX) fuel, it is essential to understand the conditions of the bubble formation. In order to examine the dependence of vacancy concentration on morphology of helium bubbles, helium was infused into (Zr,Fe)O 2−x . The oxygen vacancy concentration was controlled by addition of solute Fe 3 + into ZrO 2 . Helium was infused by hot isostatic pressing. The helium-infused specimens were observed by field emission scanning electron microscopy (FE-SEM) and field emission transmission electron microscopy (FE-TEM). In addition, X-ray fluorescence, X-ray diffraction analysis, conversion electron yield-X-ray absorption near-edge structure and FE-SEM/EDX (energy dispersive X-ray) analyses were also made to interpret the results of microstructure observations. As a result of the helium infusion treatment, numerous 0.5-10 nm bubbles were observed and its number density clearly depended on oxygen vacancy concentration. On the other hand, sizes of the helium nano-bubbles in all specimens were almost constant.

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Helium diffusion in uranium and plutonium oxides

Cited by 90 publications

References 7 publications

Gas releases and rod internal pressure of BN-added UO₂fuel

Gas releases and rod internal pressure of BN-added UO₂fuel

First-principles study of migration and diffusion mechanisms of helium in α-Be

Dependence of vacancy concentration on morphology of helium bubbles in oxide ceramics

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Helium diffusion in uranium and plutonium oxides

Cited by 90 publications

References 7 publications

Gas releases and rod internal pressure of BN-added UO2fuel

Gas releases and rod internal pressure of BN-added UO2fuel

First-principles study of migration and diffusion mechanisms of helium in α-Be

Dependence of vacancy concentration on morphology of helium bubbles in oxide ceramics

Contact Info

Product

Resources

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Gas releases and rod internal pressure of BN-added UO₂fuel

Gas releases and rod internal pressure of BN-added UO₂fuel