Influence of Composition and Fabrication Process on Out-of-Pile and In-Pile Properties of M5 Alloy

Mardon, J.P.; Charquet, D.; Senevat, J.

doi:10.1520/stp14314s

Cited by 94 publications

(54 citation statements)

References 4 publications

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“…In addition, under agreements among NRC-Studsvik-AREVA and NRC-Studsvik-Westinghouse, high-burnup defueled M5 cladding from the European Ringhals PWR reactor and ZIRLO cladding from the North Anna PWR reactor, respectively, were supplied to ANL for post-quench ductility testing. Cladding materials from these high-burnup rods are characterized in sections (5,6) relevant to the tests conducted.…”

Section: Description Of Cladding Alloys and High-burnup Fuel Segmentsmentioning

confidence: 99%

Cladding embrittlement during postulated loss-of-coolant accidents.

Billone¹,

Yan²,

Burtseva³

et al. 2008

135

105

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The effect of fuel burnup on the embrittlement of various cladding alloys was examined with laboratory tests conducted under conditions relevant to loss-of-coolant accidents (LOCAs). The cladding materials tested were Zircaloy-4, Zircaloy-2, ZIRLO, M5, and E110. Tests were performed with specimens sectioned from as-fabricated cladding, from prehydrided (surrogate for high-burnup) cladding, and from high-burnup fuel rods which had been irradiated in commercial reactors. The tests were designed to determine for each cladding material the ductile-to-brittle transition as a function of steam oxidation temperature, weight gain due to oxidation, hydrogen content, pre-transient cladding thickness, and pre-transient corrosion-layer thickness. For short, defueled cladding specimens oxidized at 1000-1200ºC, ring compression tests were performed to determine post-quench ductility at ≤135ºC. The effect of breakaway oxidation on embrittlement was also examined for short specimens oxidized at 800-1000ºC. Among other findings, embrittlement was found to be sensitive to fabrication processes -especially surface finish -but insensitive to alloy constituents for these dilute zirconium alloys used as cladding materials. It was also demonstrated that burnup effects on embrittlement are largely due to hydrogen that is absorbed in the cladding during normal operation. Some tests were also performed with longer, fueledand-pressurized cladding segments subjected to LOCA-relevant heating and cooling rates. Recommendations are given for types of tests that would identify LOCA conditions under which embrittlement would occur. ForewordFuel rod cladding is the first barrier for retention of fission products, and the structural integrity of the cladding ensures coolable core geometry. In the early 1990s, new data from foreign research programs showed degraded cladding behavior for high-burnup fuel compared with low-burnup fuel in tests designed to simulate postulated accidents. Interim actions were taken, but it became clear that extrapolation from a low-burnup data base needed to be reassessed more carefully for regulatory purposes.One of NRC's central regulations used in plant licensing deals with postulated loss-of-coolant accidents (LOCAs). A portion of that regulation in 10 CFR 50.46(b) specifies criteria that were derived from tests with unirradiated Zircaloy cladding, and these criteria limit the peak cladding temperature and the maximum cladding oxidation during the accident. These two limits are known as embrittlement criteria. Their purpose is to prevent cladding embrittlement during a LOCA, thus ensuring that the general core geometry will be maintained and be coolable.In the mid-1990s, NRC sponsored a cooperative research program at Argonne National Laboratory to reassess these limits for the possible effects of fuel burnup. The program's industry partners included the Electric Power Research Institute, Framatome ANP (now AREVA), Westinghouse, and Global Nuclear Fuel; in general, the industry partners were responsible fo...

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Section: Description Of Cladding Alloys and High-burnup Fuel Segmentsmentioning

confidence: 99%

Cladding embrittlement during postulated loss-of-coolant accidents.

Billone¹,

Yan²,

Burtseva³

et al. 2008

135

105

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“…Therefore, the development of advanced Zr alloys for a fuel cladding is being progressed in various countries. [1][2][3] The general properties of industrial materials are dependent on the microstructure of the materials and that of the materials is affected by the chemical composition and manufacturing process. 4) The corrosion kinetics and mechanical properties of a Zr alloy are affected by the alloying element and the precipitates that were formed by adding various alloying elements.…”

Section: Introductionmentioning

confidence: 99%

“…Since the corrosion behavior of a Zr alloy is largely affected by a Nb addition as an alloying element, most of the advanced Zr alloys for a fuel cladding contain Nb to improve their corrosion resistance. [1][2][3] It has been reported that the corrosion behavior of a Nb-containing Zr alloy was very complex depending on the Nb content and annealing condition. [5][6][7] From these reports, it was confirmed that a Nb addition to Zr alloys improved their corrosion resistance.…”

Section: Introductionmentioning

confidence: 99%

Recrystallization Behavior of Zr-<I>x</I>Nb Alloys

2008

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The effect of Nb contents on the recrystallization behavior of a binary Zr-xNb was studied. The specimens of Zr-xNb alloys containing 0.2, 0.4, 0.8 and 1.0 mass % Nb were prepared under various heat-treatment conditions for a cold rolled sheet. The recrystallization behavior was evaluated by using a polarized optical microscope, TEM, and a Vickers hardness tester. The recrystallization temperature of the binary alloys was slightly increased with the Nb content. It was caused by an increment of the activation energy due to an increasing Nb content. The grain growth at the high temperature region was decreased with the Nb content, because the fraction of the beta-phase, which is determined by the Nb content, was increased by increasing the Nb content. Because the minimum hardness value was observed in the temperature range between 600 and 700 C, the annealing was performed in this range to obtain a good ductility in a high Nb-containing Zr alloy.

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Section: Introductionmentioning

confidence: 99%

“…Nevertheless, Nb-containing alloys are oxidised faster than recrystallised Zircaloy in oxygen and in water vapour [4,[8][9][10][11][12], at the beginning of the oxidation, but the kinetic transition is not so sharp in Nb-containing alloys and it occurs after a longer time. In autoclave, different results are obtained, these alloys showing in most cases a better resistance to corrosion [14,15].Another difference between the two alloys is related to the effect of platinum on the oxidation rate: if platinum is deposited on the surface of an oxide layer grown on ZrNbO, in pre-transition, the oxidation rate increases, in oxygen [10] or in water vapour [11], whereas Pt has no effect on the oxidation of Zy4 [11,12].Moreover, it has been shown that the oxidation rate depends on the niobium concentration in the zirconium alloy [16], and on the oxygen pressure [17].In order to account for these results, the pre-transition stage of the oxidation of ZrNbO is suggested to be controlled by a mixed diffusion-reaction regime, and therefore in steady conditions [10,13].Finally, due to the lack of consistent data on the effect of water vapour on the oxidation rate before and after the transition, and in order to confirm (or not) these interpretations, we have studied the oxidation of a Nb-containing zirconium alloy, ZrNbO alloy, at 530°C, following the same methodology as in the case of . This approach is principally based on the verification of kinetic assumptions that are usually made a priori.…”

mentioning

confidence: 99%

Oxidation kinetics of ZrNbO in steam: Differences between the pre- and post-transition stages

Tupin

Pijolat

Valdivieso

et al. 2005

Journal of Nuclear Materials

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Zirconium based alloys (and particularly Zircaloy-4) are widely used as cladding material of fuel rods in water-cooled nuclear reactors. However, advanced alloys are now used for longer operation time in more severe conditions. One of these new alloys is a ZrNbO, which contains 1% of Nb as alloying element (instead of Sn in the case of Zircaloy-4).This ZrNbO alloy, like many zirconium alloys, undergoes a kinetic transition, which is a sharp increase in the oxidation rate when the oxide thickness exceeds a critical value. In the pre-transition stage, the kinetic oxidation curves are approximately parabolic (which is generally interpreted by a diffusion controlling step), and tend towards a quasi-linear behaviour after the transition. Recent studies have shown that the oxygen pressure has an accelerating effect on the oxidation rate of ZrNbO; a platinum layer deposited on the oxide surface has the same effect, both in oxygen and in water vapour. Thus it has been suggested that the oxidation in the pre-transition stage could be described by a mixed reaction-diffusion kinetics. Due to the lack of consistent data on the effect of water vapour on the oxidation rate of ZrNbO before and after the transition, and to confirm (or not) these interpretations, we have studied the oxidation of ZrNbO by isothermal thermogravimetry at 550°C, under controlled partial pressures of water vapour (13 to 80 hPa) and hydrogen (10 hPa). The aim is to verify if the oxidation proceeds in a steady state and if there is a rate-limiting step in one (or both) stages, and to clearly evidence the differences between the pre-and post transition stages from the kinetic point of view.TG-DSC experiments have shown that the system is in a steady state from the beginning of the oxidation, in the pre-and post-transition stages. Then, the existence of a ratelimiting step was verified using an experimental method based on temperature or pressure jumps: it has been concluded that this assumption is valid in both stages, which is not compatible with the assumption of a mixed reaction-diffusion controlled rate). Moreover, it comes out that the kinetic behaviour is different before and after the transition: the influence of temperature jumps is greater in pre-transition, whereas the effect of water vapour partial pressure is more pronounced in post-transition (nevertheless, an accelerating effect is also observed before the transition). No influence of hydrogen partial pressure has been observed. Besides, the higher the Nb content in the alloy, the higher the oxidation rate (in pre-transition). A mechanism has been proposed to account for the results obtained in pretransition, involving the diffusion of adsorbed species in the porous part of the oxide layer as rate-determining step.Keywords: ZrNbO ; oxidation ; kinetics ; water vapour ; steady state ; rate-limiting step. 1 IntroductionDespite numerous works dedicated to the oxidation kinetics of zirconium alloys by pressurized water, water vapour or oxygen, the mechanisms and the rate-limiting steps...

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Influence of Composition and Fabrication Process on Out-of-Pile and In-Pile Properties of M5 Alloy

Cited by 94 publications

References 4 publications

Cladding embrittlement during postulated loss-of-coolant accidents.

Cladding embrittlement during postulated loss-of-coolant accidents.

Recrystallization Behavior of Zr-<I>x</I>Nb Alloys

Oxidation kinetics of ZrNbO in steam: Differences between the pre- and post-transition stages

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