Fission gas release behaviour of a 103GWd/tHM fuel disc during a 1200°C annealing test

Noirot, J.; Pontillon, Yves; Yagnik, Suresh; Turnbull, J.A.; Tverberg, Terje

doi:10.1016/j.jnucmat.2013.12.002

Cited by 28 publications

(27 citation statements)

References 6 publications

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“…It has been established that almost all the gas that is depleted from the grains during fuel restructuring is captured in the newly formed pores, and that only a negligible fraction escapes to the rod free volume [86]. This conclusion is based on ceramographic examinations of the HBS, which generally show that the porosity is closed and not connected to the fuel free surface [96,97], and it is also corroborated by SIMS measurements on restructured fuel samples [95,106]. These measurements typically show that most of the gas produced in the fuel pellet rim region is retained in the HBS.…”

Section: Formation Of the Hbs (Restructuring)mentioning

confidence: 76%

“…With X-ray fluorescence (XRF) and secondary ion mass spectrometry (SIMS) techniques, it is possible to measure the average gas content in larger volumes, which comprise gas also on grain boundaries and in pores. By combining EPMA with XRF or SIMS, it has been shown that only a minor part of the fission gas that is depleted from the grain matrix is released to the rod free volume during the restructuring [92,94,95]. The major part is trapped in newly formed, micron-sized closed pores [96] that make the rim zone microstructure appear as cauliflower in micrographs [85].…”

Section: Evolution Of Pores In the High Burnup Structure (Hbs)mentioning

confidence: 99%

“…In our model, we assume that 80 % of the intragranular gas that is depleted during restructuring is transferred to the pores in the HBS, while the remaining 20 % is released to the rod free volume. This partitioning of gas makes the model reproduce fission gas release data from fuel rods with moderately high burnup that have been irradiated in commercial power reactors, but it does not reproduce the results of separate effect tests that have been carried out on fuel samples with non-prototypical design, which have undergone irradiation to very high burnup under non-prototypical conditions [95,104]. The fission gas release measured in this kind of tests is usually low.…”

Section: Formation Of the Hbs (Restructuring)mentioning

confidence: 99%

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Modelling of fine fragmentation and fission gas release of UO₂ fuel in accident conditions

Jernkvist

2019

EPJ Nuclear Sci. Technol.

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In reactor accidents that involve rapid overheating of oxide fuel, overpressurization of gas-filled bubbles and pores may lead to rupture of these cavities, fine fragmentation of the fuel material, and burst-type release of the cavity gas. Analytical rupture criteria for various types of cavities exist, but application of these criteria requires that microstructural characteristics of the fuel, such as cavity size, shape and number density, are known together with the gas content of the cavities. In this paper, we integrate rupture criteria for two kinds of cavities with models that calculate the aforementioned parameters in UO2 LWR fuel for a given operating history. The models are intended for implementation in engineering type computer programs for thermal-mechanical analyses of LWR fuel rods. Here, they have been implemented in the FRAPCON and FRAPTRAN programs and validated against experiments that simulate LOCA and RIA conditions. The capabilities and shortcomings of the proposed models are discussed in light of selected results from this validation. Calculated results suggest that the extent of fuel fragmentation and transient fission gas release depends strongly on the pre-accident fuel microstructure and fission gas distribution, but also on rapid changes in the external pressure exerted on the fuel pellets during the accident.

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Section: Formation Of the Hbs (Restructuring)mentioning

confidence: 76%

Section: Evolution Of Pores In the High Burnup Structure (Hbs)mentioning

confidence: 99%

Section: Formation Of the Hbs (Restructuring)mentioning

confidence: 99%

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Modelling of fine fragmentation and fission gas release of UO₂ fuel in accident conditions

Jernkvist

2019

EPJ Nuclear Sci. Technol.

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“…When the concentration of gas in the pores is deduced from the difference in the concentrations of retained Xe measured by LA-ICP-MS and EPMA the gas pressure in the pores is found to vary between 57 and 127 MPa (see Table 5). These values, however, could be too low based on current understanding that little fission gas release occurs from the HBS during normal reactor operation (see e.g., results from more recent investigations using SIMS [36,37] and an NFIR (Nuclear Fuel Industry Research) irradiation [38]). This Table 5 Average pressure of fission gas in the pores of the high burn-up structure at several radial positions in the outer region of the fuel in sample 12G2-GC.…”

Section: Gas Pressure In the Pores Of The High Burn-up Structurementioning

confidence: 99%

On the condition of UO2 nuclear fuel irradiated in a PWR to a burn-up in excess of 110 MWd/kgHM

Restani

Horvath

Goll

et al. 2016

Journal of Nuclear Materials

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“…HBS may play a role, but no direct evidence of that was found, though, prior to the ramps, high strain of the HBS can be seen in the large fabrication pores decrease as well as on free surface HBS major swelling. In loss of coolant accident (LOCA) type conditions, out of pile heating tests on fuel sections as well on specially designed experimental discs have shown, like during in-pile LOCA tests, the fragmentation of HBS [7][8]. The areas prone to fragmentation are the HBS areas but also the high precipitation areas [9].…”

Section: Fig 1: Sharp Limit Between Hbs and Non-hbs Areas In A 55 Gwmentioning

confidence: 99%

High Burn-up Structure in Nuclear Fuel: Impact on Fuel Behavior

Noirot

Pontillon

Lamontagne

et al. 2016

EPJ Web of Conferences

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When UO 2 and (U,Pu)O 2 fuels locally reach high burn-up, a major change in the microstructure takes place. The initial grains are replaced by thousands of much smaller grains, fission gases form micrometric bubbles and metallic fission products form precipitates. This occurs typically at the rim of the pellets and in heterogeneous MOX fuel Pu rich agglomerates. The high burn-up at the rim of the pellets is due to a high capture of epithermal neutrons by 238 U leading locally to a higher concentration of fissile Pu than in the rest of the pellet. In the heterogeneous MOX fuels, this rim effect is also active, but most of the high burn-up structure (HBS) formation is linked to the high local concentration of fissile Pu in the Pu agglomerates. This Pu distribution leads to sharp borders between HBS and non-HBS areas ( Fig.1). Fig. 1: Sharp limit between HBS and non-HBS areas in a 55 GWd/t HM MOX MIMAS fuel (from [1]).In these MOX fuels, the HBS forming at various radial positions, and not only at the rim, it was shown that the size of the new grains, of the bubbles and of the precipitates increase with the irradiation local temperatures. Other parameters have been shown to have an influence on the HBS initiation threshold, such as the irradiation density rate, the fuel composition with an effect of the Pu presence, but also of the Gd concentration in poisoned fuels, some of the studied additives, like Cr, and, maybe some of the impurities. However, not all the differences in the UO 2 HBS rim extent measured by different teams on various fuels have been explained [2][3]. The effect of impurities may be the main reason for these differences, but it has not been documented enough yet. It has been shown recently, with examinations of a UO 2 fuel in which 235 U was heterogeneously distributed, that a high Pu concentration is not mandatory for HBS formation [4].Several changes in the fuel behavior occur concomitantly with the HBS formation. An increase of the fission gas release and an increase in the fuel swelling rate are measured [3]. It was shown by indirect and direct approaches that HBS formation was not the main contributor to the increase of fission gas release at high burn-up [1,[5][6]. Indeed, studying the Kr/Xe ratio or some isotopic ratio in the gases collected during rod puncturing and using the differences in the gas productions as a function of the radial position, it was shown that the HBS areas were not the main source of the released gases. SIMS measurements of the local retention confirmed this trend. Nonetheless, the formation of a strong bonding between the fuel pellet periphery and the inner surface of the cladding, with the formation of the inner zirconia layer induces tensile stresses in the fuel during power

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Fission gas release behaviour of a 103GWd/tHM fuel disc during a 1200°C annealing test

Cited by 28 publications

References 6 publications

Modelling of fine fragmentation and fission gas release of UO₂ fuel in accident conditions

Modelling of fine fragmentation and fission gas release of UO₂ fuel in accident conditions

On the condition of UO2 nuclear fuel irradiated in a PWR to a burn-up in excess of 110 MWd/kgHM

High Burn-up Structure in Nuclear Fuel: Impact on Fuel Behavior

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Fission gas release behaviour of a 103GWd/tHM fuel disc during a 1200°C annealing test

Cited by 28 publications

References 6 publications

Modelling of fine fragmentation and fission gas release of UO2 fuel in accident conditions

Modelling of fine fragmentation and fission gas release of UO2 fuel in accident conditions

On the condition of UO2 nuclear fuel irradiated in a PWR to a burn-up in excess of 110 MWd/kgHM

High Burn-up Structure in Nuclear Fuel: Impact on Fuel Behavior

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Modelling of fine fragmentation and fission gas release of UO₂ fuel in accident conditions

Modelling of fine fragmentation and fission gas release of UO₂ fuel in accident conditions