Corrosion and Hydrogen Uptake in Zirconium Claddings Irradiated in Light Water Reactors PDF Download
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Author: Holger Wiese
Publisher:
ISBN:
Category : High burnup
Languages : en
Pages : 34
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Book Description
The objective of this paper is to summarize the results of the latest observations performed at Paul Scherrer Institut on irradiated fuel claddings, to characterize their corrosion and hydrogen-uptake behavior. Two categories of studies have been performed. (1) A series of destructive tests were achieved on the fuel rods irradiated in a boiling-water reactor (BWR), including hydrogen concentration by hot-gas extraction. These results provided the hydrogen content of the cladding at different stages of irradiation, at different elevations along the rod. (2) Another series of examinations using a correlative microscopy method, i.e., using different techniques, including transmission electron microscopy (TEM), electron probe microanalysis (EPMA), and secondary ion mass spectrometry (SIMS), on the same material and in the same region of the metal-oxide interface have provided useful data regarding the oxide layer combining the signals from oxides and from hydrides. Furthermore, the effect of the type of alloying element has been examined for in-reactor oxidation. These studies are subsequently combined with the findings from out-of-pile studies, using techniques, such as neutron radiography, to confirm the in-reactor observations. Results have shown that: (i) the hydrogen pickup fraction varies at different conditions and could even decrease as the oxide thickness increases; (ii) the distribution of hydrogen in the cladding is usually inhomogeneous; (iii) the most determining parameter for hydrogen uptake seems to be the microstructure of the oxide, and the nature of the alloying element will influence to a certain extent this parameter; (iv) furthermore, the stress in the oxide layer can modify the crack distribution in the latter, cracks will in turn shorten the route for the hydrogen to access the metal. These results will be discussed as a contribution to the available knowledge about hydrogen uptake and will provide a global support for the models of the uptake phenomenon.
Author: Holger Wiese
Publisher:
ISBN:
Category : High burnup
Languages : en
Pages : 34
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Book Description
The objective of this paper is to summarize the results of the latest observations performed at Paul Scherrer Institut on irradiated fuel claddings, to characterize their corrosion and hydrogen-uptake behavior. Two categories of studies have been performed. (1) A series of destructive tests were achieved on the fuel rods irradiated in a boiling-water reactor (BWR), including hydrogen concentration by hot-gas extraction. These results provided the hydrogen content of the cladding at different stages of irradiation, at different elevations along the rod. (2) Another series of examinations using a correlative microscopy method, i.e., using different techniques, including transmission electron microscopy (TEM), electron probe microanalysis (EPMA), and secondary ion mass spectrometry (SIMS), on the same material and in the same region of the metal-oxide interface have provided useful data regarding the oxide layer combining the signals from oxides and from hydrides. Furthermore, the effect of the type of alloying element has been examined for in-reactor oxidation. These studies are subsequently combined with the findings from out-of-pile studies, using techniques, such as neutron radiography, to confirm the in-reactor observations. Results have shown that: (i) the hydrogen pickup fraction varies at different conditions and could even decrease as the oxide thickness increases; (ii) the distribution of hydrogen in the cladding is usually inhomogeneous; (iii) the most determining parameter for hydrogen uptake seems to be the microstructure of the oxide, and the nature of the alloying element will influence to a certain extent this parameter; (iv) furthermore, the stress in the oxide layer can modify the crack distribution in the latter, cracks will in turn shorten the route for the hydrogen to access the metal. These results will be discussed as a contribution to the available knowledge about hydrogen uptake and will provide a global support for the models of the uptake phenomenon.
Author: Adrienn Baris
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
In light water reactors the fuel is encapsulated in Zr-based claddings that withstand the harsh environment (neutron bombardment, high temperature and water under pressure); without absorbing too many neutrons to sustain the chain reaction in the reactor core. Relatively high corrosion resistance of Zr is achieved when alloyed (e.g. with Sn, Fe, Cr, Ni, or Nb). Some elements form second phase particles (SPPs) and provide protection against rapid corrosion. The cladding undergoes compositional and microstructural changes, such as irradiation induced SPP dissolution. Zr oxidizes at the metal-oxide interface by diffusion of the oxidizing species through the oxide layer. Therefore, a protective inner barrier oxide is essential to prevent the metal from fast reaction with different species. Hydrogen is released as a by-product of the oxidation, and by the radiolysis of the coolant. If H enters the metal it precipitates as brittle Zr-hydrides degrading the cladding's mechanical properties. The H-uptake is a critical safety issue. Although, extensive literature is available on this topic, there are some aspects that need better understanding. Increasing H-uptake of certain cladding types at high burnups was reported. The causes are not yet fully understood. To better understand the causes of increased H-uptake at high burnups, an extremely high burnup cladding (9 cycle LK3/L Zircaloy-2) from boiling water reactor provided the basis of the study. The same type of cladding after different service times was examined revealing the compositional and microstructural evolution. Two types of cladding from pressurized water reactor with medium burnup were studied to separate the reactor- and alloy-specific parameters from the generic ones. FIB tomography was used for the 3D reconstructions of the microstructure; EPMA and ChemiSTEM for the micro- and nanometric chemical analysis. It is revealed that regardless of alloy- and reactor-type, crack-free oxide and the absence of large hydrides in the vicinity of the metal-oxide interface; undulated interface; and presence of SPPs are among the essential factors for the cladding's high performance. It is demonstrated that the oxidation of the hydrides at the metal-oxide interface induces crack formation in the oxide, reducing its protectiveness. High level of SPP dissolution, large hydride phases in the metal and high level of porosity in the oxide at the interface, straight metal-oxide interface, stoichiometric oxide, increased Ni concentration in the inner oxide, segregation of Fe, Ni, Sn and slightly Cr in the metal grain boundaries, Sn segregation at the interface oxide are identified as the causes of increased H-uptake of the LK3/L cladding at high burnups. Although all of these factors are present after 9 cycles, the cladding does not show extremely fast oxidation and H-uptake even beyond the designed service time.
Author: VF. Urbanic
Publisher:
ISBN:
Category : Corrosion
Languages : en
Pages : 17
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Book Description
The in-reactor corrosion and hydrogen pickup of Zircaloy-2 and Zr-2.5Nb pressure tube materials are being studied in two test loops: a light water loop in the NRU research reactor, and a new heavy water loop in the Halden reactor. The complimentary test programs examine the corrosion behavior of small specimens as a function of fast neutron flux and fluence, temperature, water chemistry, and specimen pre-oxidation.
Author: Raul B. Rebak
Publisher: Elsevier
ISBN: 0128175044
Category : Technology & Engineering
Languages : en
Pages : 237
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Book Description
Accident Tolerant Materials for Light Water Reactor Fuels provides a description of what an accident tolerant fuel is and the benefits and detriments of each concept. The book begins with an introduction to nuclear power as a renewable energy source and the current materials being utilized in light water reactors. It then moves on to discuss the recent advancements being made in accident tolerant fuels, reviewing the specific materials, their fabrication and implementation, environmental resistance, irradiation behavior, and licensing requirements. The book concludes with a look to the future of new power generation technologies. It is written for scientists and engineers working in the nuclear power industry and is the first comprehensive work on this topic. Introduces the fundamental description of accident tolerant fuel, including fabrication and implementation Describes both the benefits and detriments of the various Accident Tolerant Fuel concepts Includes information on the process of materials selection with a discussion of how and why specific materials were chosen, as well as why others failed
Author: A. M. Garde
Publisher: ASTM International
ISBN: 0803120117
Category : Nuclear fuel claddings
Languages : en
Pages : 805
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Book Description
Author: J. H. Schemel
Publisher: ASTM International
ISBN: 9780803106017
Category : Business & Economics
Languages : en
Pages : 656
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Author:
Publisher: ASTM International
ISBN:
Category :
Languages : en
Pages : 490
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Author: Aditya Shivprasad
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Hydrogen pick-up of zirconium-based fuel cladding and structural materials duringin-reactor corrosion can degrade fuel component performance in existing light waterreactors (LWRs) and advanced nuclear reactors, such as the LWR-like supercriticalwater reactors (SCWRs), as the ingress of corrosion hydrogen can lead to the formationof brittle hydrides. In the boiling water reactor (BWR) environment, Zircaloy-2 fuelcladding and reactor core components, such as water rods and channel boxes, canexperience accelerated hydrogen pick-up (higher pickup fraction) at high burnup whenexposed for one extra 24-month cycle, while Zircaloy-4 components under similarconditions do not. Because the principal difference between the two alloys is thatZircaloy-2 contains nickel, this accelerated hydrogen pick-up has been hypothesizedto result from the presence of nickel and its role in the corrosion process whenincorporated into the protective oxide layer.Zircaloy-2 and Zircaloy-4 sister samples were corroded in 360 _C water and anadditional set of Zircaloy-2 samples was corroded in 400 _C steam. Total weightgain, assumed to be due mostly to oxygen, and hydrogen content were measured asfunctions of exposure time. The results indicate that Zircaloy-2 samples absorbed morehydrogen than did Zircaloy-4 samples on the basis of total weight gain (hydrogen pickupfraction), though both exhibited similar corrosion kinetics parameters. Microbeamsynchrotron radiation X-ray absorption near-edge spectroscopy (XANES) of selectedZircaloy-2 samples at the Advanced Photon Source (APS) was used to probe theoxidation states of nickel and iron in these materials and understand the evolutionof the oxidation states of these alloying elements as functions of distance from theoxide/metal interface. Result showed that a significant fraction of nickel atomsremained metallic upon incorporation in the oxide layer. In contrast, iron atomsoxidized much earlier than did nickel atoms and, in most cases, fully oxidized withinseveral micrometers from the oxide/metal interface. A general hypothesis was madethat metallic nickel in contact with the coolant may catalyze the surface reactionsinvolved in the hydrogen pick-up mechanism.To understand accelerated hydrogen pick-up of certain Zircaloy-2 samples at highburn-up, additional XANES examinations were performed on Zircaloy-2 water rodsexposed in-reactor to high burn-up in commercial BWRs. The first set of samples wascorroded in the Limerick-1 reactor, while the second set was corroded in the Dresden-2reactor. Within each set of samples, fluences, oxide thicknesses, and sample elevationswere similar, but hydrogen pick-up fractions were vastly different. In the first setof samples, oxide thicknesses ranged from 28 - 35 m, but hydrogen pick-up rangedbetween 15 and 51%. In the second set of samples, oxide thicknesses ranged between3.5 m and 16 m, but hydrogen pick-up ranged from 28 - 69%. All samples wereirradiated to fluences between 9.4 and 13.1 1021 n/cm2 for neutron energies above1 MeV. Results of XANES examinations showed a similar correlation between thedelayed oxidation of nickel and higher hydrogen pick-up of Zircaloy-2 at high burn-up.A significant fraction (greater than 30%) of nickel atoms were found to be in themetallic state in the porous oxide layer. It was hypothesized that this metallic nickelis responsible for enhancing hydrogen pick-up by catalyzing the surface reactions thataffect the overall hydrogen pick-up reaction. This would allow for easier absorptionof hydrogen into the protective oxide layer from the coolant. Ab initio modeling ofXANES of selected iron- and nickel-containing compounds was also performed andcompared to experimental results to help understand how different populations ofalloying elements oxidized upon incorporation into the oxide layer.A concurrent study of the microstructure of oxide layers formed on these sameirradiated water rods was performed to understand if there was a characteristicmicrostructure associated with accelerated hydrogen pick-up. Microbeam X-raydiffraction (XRD) at the APS was performed on water rod samples to study oxidetexture, phase content, and grain size. A similar examination was performed onsteam-corroded Zircaloy-2 to serve as a comparison. Results showed that the oxidelayers formed on these samples consisted primarily of highly-oriented monoclinic phasezirconium oxide with a small fraction of tetragonal phase oxide. Monoclinic phasegrains were shown to grow as a function of distance from the oxide/metal interface,while tetragonal phase grains remained a constant size, indicating a tetragonal-to-monoclinic phase transformation above a critical grain size of approximately 10 nm.The tetragonal phase fraction was also calculated and observed to maximize nearthe oxide/metal interface, coinciding with the appearance of the (002)-tetragonalphase diffraction reflection, which appeared to be highly-oriented and strained, butdisappeared away from the oxide/metal interface. Findings were consistent withprevious microbeam XRD examinations of oxide layers formed on Zircaloy-4 underautoclave conditions. Transmission XRD examinations were also performed on aselected steam-corroded sample to serve as an additional comparison.The observations presented in this study helped to propose a mechanism foroxidation of different populations of iron and nickel upon incorporation into theZircaloy-2 oxide layer and the effect on the hydrogen pick-up mechanism.
Author: David O. Pickman
Publisher:
ISBN: 9780803184213
Category : Corrosion
Languages : en
Pages : 16
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Book Description
Various aspects of zirconium alloy development for light water reactors in the UK and Scandinavia are reviewed, including the contribution made by some unique nuclear testing facilities. Among the problems encountered were the irradiation enhancement of corrosion and hydrogen pickup, crud deposition, iodine-induced stress-corrosion cracking on power ramping, and severe cladding deformation in loss-of-coolant accident conditions. The causes and behavior of defect, including hydride defects and fretting corrosion, are discussed. The original paper was published by ASTM International in STP 1245, Zirconium in the Nuclear Industry: Tenth International Symposium, 1994, pp. 1932.
Author: DO. Pickman
Publisher:
ISBN:
Category : Corrosion
Languages : en
Pages : 14
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Book Description
Various aspects of zirconium alloy development for light water reactors in the UK and Scandinavia are reviewed, including the contribution made by some unique nuclear testing facilities. Among the problems encountered were the irradiation enhancement of corrosion and hydrogen pickup, crud deposition, iodine-induced stress-corrosion cracking on power ramping, and severe cladding deformation in loss-of-coolant accident conditions. The causes and behavior of defects, including hydride defects and fretting corrosion, are discussed.
