Detailed characterization of a PWR fuel rod at high burnup in support of LOCA testing

Cappia, Fabiola; Wright, Karen E.; Frazer, D.; Bawane, Kaustubh; Kombaiah, Boopathy; Williams, W.; Finkeldei, Sarah; Teng, Fei; Giglio, Jeffrey J.; Cinbiz, Mahmut Nedim; Hilton, B.; Strumpell, J.; Daum, R.; Yueh, Ken; Jensen, Colby; Wachs, Daniel M.

doi:10.1016/j.jnucmat.2022.153881

Cited by 12 publications

(17 citation statements)

References 38 publications

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“…These comments are meant to show that more work is to be done to really address the question about the real reasons for this restructuring and about the real conditions for it to occur and evolve. Also, in the case reported in 36 , the rod had experienced higher linear powers than those reported in this article, leading to a fission gas release fraction of 16%, clearly higher than in our cases. In 36 , the bubbles were larger at 0R than on the periphery of the central restructured area.…”

Section: Discussioncontrasting

confidence: 67%

“…For all Std samples examined, the restructuring and bubble evolutions were therefore more advanced on the periphery of the central area than at 0R. The restructuring was also more advanced on the periphery of the central area than at 0R in the work reported recently by Cappia et al 36 . An explanation for this trend could be that higher temperatures during the irradiation promoted defect annealing and fission product diffusion in the center thus decreasing the local defect build-up leading to restructuring.…”

Section: Discussionsupporting

confidence: 60%

“…Such grain restructuring was also observed in Al-Si and Al-Cr doped fuels, by Jädernäs et al in 35 . Very recently, Cappia et al 36 reported similar restructuring in a 76 GWd/t U PWR UO 2 fuel section.…”

Section: Introductionmentioning

confidence: 74%

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Restructuring in high burn-up pressurized water reactor UO2 fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy

Noirot

Dowek

Zacharie-Aubrun

et al. 2022

Journal of Applied Physics

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Focussed ion beam - scanning electron microscope (FIB-SEM) 3D examination was conducted on three standard UO2 and one Cr doped UO2 high burn-up pressurized water reactor (PWR) fuel samples. This work complemented other microanalysis examination, including an electron backscattered diffraction (EBSD) work on the polished surface. A parallel article giving the EBSD results was submitted simultaneously. Together, they found, in all the central area of these high burn-up samples: (i) a restructuring of the initial grains into smaller sub-grains forming low angle boundaries and with crystal orientations around that of their parent grains; and (ii) intragranular bubbles mostly situated on these low angle boundaries. The FIB-SEM 3D examination showed how such inter-sub-grain bubbles start as small compact but also small lenticular bubbles, similar to typical small intergranular lenticular bubbles. With increasing burn-up, these lenticular bubbles get thicker and locally interlink to form more complex bubbles. However, no long distance networks, between the sub-grains or between the original grains, were found. Such networks could have been a path for part of the fission gases to reach the grain boundaries, the grain edges (the intersection line of three grain boundaries), and the rod free volumes. These FIB-SEM 3D examinations brought details on the intragranular and intergranular bubbles situation for each studied volume. The distribution of the intragranular bubbles according to their sizes and shapes was exposed. The central restructuring, studied in this work, is likely to play a role in the increase of the fission gas release fractions at high burn-up. This work is an incentive to study further this restructuring and the bubbles formed, combining different approaches.

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Section: Discussioncontrasting

confidence: 67%

Section: Discussionsupporting

confidence: 60%

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Restructuring in high burn-up pressurized water reactor UO2 fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy

Noirot

Dowek

Zacharie-Aubrun

et al. 2022

Journal of Applied Physics

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“…It has been used for comparison with our new results. More recently, Cappia et al 19 published a post-irradiation characterization of a pressurized water reactor (PWR) fuel at high burn-up (76 GWd/tM) at different scales, by optical microscopy, EPMA, SEM, EBSD and TEM. The rod fission gas release at the end of the irradiation was 16% of the production.…”

Section: Previous Ebsd Studies On High Burn-up Lwr Fuelsmentioning

confidence: 99%

“…However, only a few experiments have used electron back-scattered diffraction (EBSD) to study this phenomenon. This is mainly because only a few hot laboratories have access to such a device for irradiated fuel studies on LWR (Bengstsson et al 15 , Jädernäs et al 16 , Gerczak et al 17 , Noirot et al 18 , Cappia et al 19 ) and on FR (Teague et al 20 , Frazer et al 21 ). In the same burn-up range in which HBS forms on the rim of the LWR UO 2 fuel pellets, micrometric or submicrometric fission gas bubbles form in the central area of the pellets.…”

Section: Introductionmentioning

confidence: 99%

Restructuring in high burn-up UO2 fuels: Experimental characterization by electron backscattered diffraction

Zacharie-Aubrun

Dowek

Noirot

et al. 2022

Journal of Applied Physics

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This paper discusses the use of electron backscattered diffraction to characterize restructuring in a set of UO2 samples, irradiated in a pressurized water reactor at a burn-up between 35 and 73 GWd/tU, including standard UO2 samples and Cr-doped UO2 samples, to provide a better understanding of restructuring occurring both on the periphery and in the center of high-burn-up pellets. The formation of a high burn-up structure on the periphery of high burn-up UO2 was confirmed in our experiment. We found restructuring associated with bubble formation of all the samples in the central area, with higher irradiation temperatures when the burn-up exceeded 61 GWd/tU, regardless of their initial microstructure. This restructuring tended to progress with the increasing burn-up and to sub-divide the initial grains into sub-grains, with orientations close to that of the parent grains. Radial changes and differences between these samples showed that the burn-up and the temperature were not the only relevant parameters involved in restructuring.

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Towards simulations of fuel rod behaviour during severe accidents by coupling TRANSURANUS with SCIANTIX and MFPR-F

Zullo

Pizzocri

Luzzi

et al. 2023

Annals of Nuclear Energy

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Detailed characterization of a PWR fuel rod at high burnup in support of LOCA testing

Cited by 12 publications

References 38 publications

Restructuring in high burn-up pressurized water reactor UO2 fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy

Restructuring in high burn-up pressurized water reactor UO2 fuel central parts: Experimental 3D characterization by focused ion beam—scanning electron microscopy

Restructuring in high burn-up UO2 fuels: Experimental characterization by electron backscattered diffraction

Towards simulations of fuel rod behaviour during severe accidents by coupling TRANSURANUS with SCIANTIX and MFPR-F

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