Hydride distribution around a blister in Zr–2.5Nb pressure tubes

Domizzi, G.; Vigna, G.; Bermúdez, S.; Ovejero-Garcı́a, J.

doi:10.1016/s0022-3115(99)00130-0

Cited by 18 publications

(16 citation statements)

References 17 publications

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“…Region III is the region of single-phase hydride. The boundary between regions II and III appears darker under the optical microscope because of uneven etching [13,16]. Single-phase region III etches evenly and appears brighter.…”

Section: Resultsmentioning

confidence: 99%

Stress field estimation around a semi-constrained inclusion and its validation by interpreting hydride platelet orientation around a blister in a Zr–2.5Nb alloy

Singh

Kishore

Sinha

et al. 2003

Materials Science and Engineering: A

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Section: Resultsmentioning

confidence: 99%

Stress field estimation around a semi-constrained inclusion and its validation by interpreting hydride platelet orientation around a blister in a Zr–2.5Nb alloy

Singh

Kishore

Sinha

et al. 2003

Materials Science and Engineering: A

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“…The reason of the discrepancy between the ratio in Zircaloy-4 blister from our study and Zr-2.5%Nb is not due (at least not completely) to a very low hydrogen content in Zr-2.5% blisters. XRD experiments showed that the hydrogen content in the core of a Domizzi et al [7] blister is of about 80% in volumetric fraction [75] .…”

Section: Comparison Of Different Laboratory Grown Blistersmentioning

confidence: 95%

“…Blister induced failure was observed in 1983, when an axial crack developed in a CANDU Zircaloy-2 pressure tube along an array of hydride blisters on the external surface that was placed against the cold calendria tube [4]. This finding has motivated several experimental studies on hydride blister formation and growth, mainly focused on Zirconium-2.5%Nb [5,6,7,8,9,10], which is the material that replaced Zircaloy-2 alloy for pressure tubes in the CANDU reactors. In all these studies, hydride blisters were obtained in laboratories with thermo-diffusion setups.…”

Section: Introductionmentioning

confidence: 99%

Formation and characterization of hydride blisters in Zircaloy-4 cladding tubes

Ménibus

Auzoux

Dieye

et al. 2014

Journal of Nuclear Materials

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This article is focused on the formation of hydride blisters in zirconium alloys an experimental and theoritical standpoint, and their characterization in terms of morphology, hydrides crystallographic phases, hardness and hydrogen concentration. An experimental setup was developed to grow hydride blisters on pre-hydrided Zircaloy-4 cladding tubes by thermo-diffusion. The thermal conditions were optimized based on thermo-diffusion calculations, that take into account the hysteresis in the hydrogen solubility limit, to obtain a high blister growth rate. Micro X-Ray Diffraction (XRD), nano-hardness and Elastic Recoil Detection Analysis (ERDA) showed that the blisters contain a hydrogen gradient, with pure δ-hydride phase close to the external surface over one third of the blister depth. thermo-diffusion * Tel.: +33 1 69 08 39 43; e-mail: arthur.hellouin-de-menibus@cea.fr 1 calculations showed these half thickness blisters should grow in only a few days in PWR conditions. Eventually, the Diffusion Equilibrium Threshold (DET) was defined as a criterion that limits the blister growth, and emphasizes that the hysteresis in the hydrogen solubility limit in zirconium must be taken into account to model hydrogen thermo-diffusion in zirconium alloys.

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“…Even the deterioration or removal of the cladding external oxide is enough to produce an increase. In the absence of stresses, hydrides normally precipitate on the circumferential-axial plane, producing no ductility reduction with hydrogen content below 700-800 ppm [3][4][5][6][7], well above the available amount. However, when radial hydrides are present, this critical concentration is significantly reduced, 55 ppm according to MARSHALL and LOUTHAN [8].…”

Section: Hydride Embrittlement (He)mentioning

confidence: 99%

“…They have shown that large hydride lens and rim initiate specimen rupture during burst test at 350°C (burst pressure = 262-453 bar), but small hydride lens (1-3 mm 2 ) did not contribute to burst opening. Nevertheless, these small lenses may present cracks inside as were observed in blisters with area lower than 1 mm 2 , grown in laboratory in Zr-2.5Nb [6][7], which are potential stress concentrators, promoting DHC during storage.…”

Section: Blisters and Rimsmentioning

confidence: 99%

Effect of blisters and rims on radial hydride precipitation in fuel elements under dry storage conditions

et al. 2018

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Hydrogen enters in Zry clads during fuel element life in service; when hydrogen exceeds the terminal solid solubility, circumferential hydrides are precipitated. In the presence of thermal gradients, produced for instance by oxide spallation, localized concentration of hydrides -known as blisters -can be formed. Due to the fact that zirconium hydrides have a lower density that zirconium alloys, stresses are produced around blisters. These stresses may overcome the necessary threshold to precipitate radial hydrides. Moreover, cracks inside blisters may act as initiators of delayed hydride cracking (DHC). In the dry storage facilities developed for Atucha 1, Zry -4 clads of spent fuel elements (SFE) must withstand environmental conditions which include maximum temperature of 200°C and internal SFE pressure of ~ 75 bar (value at end of cycle). During dry storage, if blisters are present, stresses around them are superposed to circumferential stresses generated by the internal pressure due to fission gasses helping precipitation and/or growth of radial hydrides and DHC process. In order to assess this possibility, in the present work sections of Zry-4 cladding were hydrided. Blisters have been grown by thermal gradient under different conditions of temperature and shapes of thermal contact in order to obtain different blister dimensions and fraction of radial hydrides. After blister formation, some specimens were subjected to Hydride Reorientation Test (HRT) by applying an internal pressure of 75 bar at 200°C. Finally, tubes were sectioned and metallographically analyzed looking for radial hydrides. In some samples radial hydrides were observed, which effectively grew by the internal pressure of Zrycladding during HRT.

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Hydride distribution around a blister in Zr–2.5Nb pressure tubes

Cited by 18 publications

References 17 publications

Stress field estimation around a semi-constrained inclusion and its validation by interpreting hydride platelet orientation around a blister in a Zr–2.5Nb alloy

Stress field estimation around a semi-constrained inclusion and its validation by interpreting hydride platelet orientation around a blister in a Zr–2.5Nb alloy

Formation and characterization of hydride blisters in Zircaloy-4 cladding tubes

Effect of blisters and rims on radial hydride precipitation in fuel elements under dry storage conditions

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