Damage Stucture in Zirconium Alloys Irradiated at 573 to 923°K. [Neutron Fluence 1 X 1025 N. M−2]. PDF Download
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Languages : en
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The microstructures of annealed zirconium, Zircaloy-2 and Zr-2.5 wt % Nb alloy and of Zr-2.5 Nb containing .cap alpha.' were studied after neutron irradiation to fluences approximately equal to 1 x 1025 n x m−2 in the temperature range 573 to 923°K. The principal form of damage was dislocation loops which increased in size and decreased in density with increasing temperature and which did not exist above 773°K. The Burgers vector of the loops was consistent with a/3 1120. Half or more of the loops were of vacancy type. No dislocation networks or voids were seen. It is argued that the bias of loops for self-interstitial atoms in .cap alpha.-zirconium is very weak, permitting competitive vacancy and interstitial loops, preventing growth of loops into gross dislocation structure, and depressing the vacancy super-saturation so that voids cannot arise.
![Damage Stucture in Zirconium Alloys Irradiated at 573 to 923°K. [Neutron Fluence 1 X 1025 N. M−2]. PDF](https://books.google.com/books/content/images/frontcover/oEZsAQAACAAJ?fife=w80-h100)
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Languages : en
Pages :
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The microstructures of annealed zirconium, Zircaloy-2 and Zr-2.5 wt % Nb alloy and of Zr-2.5 Nb containing .cap alpha.' were studied after neutron irradiation to fluences approximately equal to 1 x 1025 n x m−2 in the temperature range 573 to 923°K. The principal form of damage was dislocation loops which increased in size and decreased in density with increasing temperature and which did not exist above 773°K. The Burgers vector of the loops was consistent with a/3 1120. Half or more of the loops were of vacancy type. No dislocation networks or voids were seen. It is argued that the bias of loops for self-interstitial atoms in .cap alpha.-zirconium is very weak, permitting competitive vacancy and interstitial loops, preventing growth of loops into gross dislocation structure, and depressing the vacancy super-saturation so that voids cannot arise.
Author: C. E. Coleman
Publisher: [Amsterdam] : North-Holland Publishing Company
ISBN:
Category :
Languages : en
Pages : 12
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Author: V. Fidleris
Publisher:
ISBN:
Category : Dislocations
Languages : en
Pages : 17
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We report the dislocation microstructures of annealed Zircaloy-2, cold-worked Zr-2.5 wt% Nb and extruded Excel (Zr-3.5 wt% Sn-0.8 wt% Nb-0.8 wt% Mo) neutron irradiated in EBR-II at 670-690 K to fluences of 1.7-6.3 x 1025 n/m2 (E>1 MeV) and also of cold-worked Zr-2.5 wt% Nb irradiated to 1.2 x 1025 n/m2 (E>1 MeV) at 550 K in Unit 4 of Pickering Nuclear Generating Station.
Author: M. Griffiths
Publisher:
ISBN:
Category : Congress
Languages : en
Pages : 23
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X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to characterize microstructural and microchemical changes produced by neutron irradiation in zirconium and zirconium alloys. Zircaloy-2, Zircaloy-4, and Zr-2.5Nb alloys with differing metallurgical states have been analyzed after irradiation for neutron fluences up to 25 x 1025 n.m-2 (E > 1 MeV) for a range of temperatures between 330 and 580 K.
Author:
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Category : Nuclear reactors
Languages : en
Pages : 18
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As indicated in Chapter 1, one of the variables of importance in describing the irradiation creep of zirconium alloys is the degree of exposure of the material to irradiation, often described in terms of neutron fluence. The primary reason for this neutron fluence dependence is that during irradiation an irradiation-induced microstructure evolves, and this microstructure in turn dramatically affects mechanical properties. This microstructure, and hence these property changes, are not entirely fluence dependent, but are functions of the irradiation temperature, the stress state, the neutron energy spectrum, and the initial metallurgical conditions. Consequently, a discussion of irradiation creep in zirconium and the Zircaloys must be prefaced by some review of the nature of the irradiation microstructure, its observed dependence on material and operating conditions, and its effect on deformation behavior.
Author: RB. Adamson
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 23
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Irradiation growth behavior of zirconium, Zircaloy-2 and Zircaloy-4,Zr-2.5Nb, and Zr-3.5Sn-0.8Mo-0.8Nb (EXCEL) was studied on specimens irradiated in the Experimental Breeder Reactor II (EBR-II) to fluences of 1.2 to 16.9 x 1025 neutrons (n).m-2 (E > 1 MeV) in the temperature range 644 to 725 K. In Zircaloy, growth and growth rate were observed to increase continuously with fluence up to 16.9 x 1025 n.m-2 with no indication of saturation in either recrystallized or cold-worked materials. Positive growth strains of 1.5% and negative strains of approximately 2% to 2.5% were observed in both recrystallized and cold-worked Zircaloy. The formation of both a-type loops and c component dislocations is recrystallized Zircaloy under irradiation appears to be the basis in this material for growth strains similar in magnitude to those in cold-worked Zircaloy. Alloy additions to zirconium can increase growth by as much as an order of magnitude for a given texture at the higher irradiation temperatures and fluences. A sharp change to increasing growth rate with temperature occurs in Zircaloy at ~670 K, with a similar trend indicated for the other alloys. Although growth in all these alloys is a strong function of crystallographic texture, an exact (1-3f) type of dependence is not always apparent. In Zr-2.5Nb the dependence of growth on texture appears to be masked by the precipitation of betaniobium, with a transition to a well-defined texture dependence being a function of fluence and temperature. Significant differences in growth behavior were observed in nominally similar Zircaloys, apparently due to minor microstructural or chemical differences.
Author: CE. Coleman
Publisher:
ISBN:
Category : Electron microscopy
Languages : en
Pages : 19
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Book Description
Structures developed in zirconium alloys during irradiation creep have been characterized by transmission electron microscopy (TEM). Alloys investigated were annealed Zircaloy-2, cold-worked Zircaloy-2 and cold-worked Zr-2.5Nb pressure tube material. Thin films were taken from material deformed in the NRU, NRX and Pickering-3 reactors at temperatures of 530 to 600 K under stresses of 117 to 552 MPa giving strains in the range 0.14 to 8.8 percent. Stress-induced orientation of dislocation loops makes a negligible contribution to irradiation creep at all stresses. At the lower stresses (and hence strains), the size and distribution of the damage is unaffected by stress, being the same in the head and gage sections of creep specimens. At higher stresses (strains), there is much clearing of the damage by plastic deformation. The deformation however is very uneven, producing structures in different grains of the same specimen that can show no deformation, swaths cleared of irradiation damage, or dislocation tangles or cell formation. The relevance of these TEM observations to irradiation creep mechanisms is discussed.
Author: RG. Blake
Publisher:
ISBN:
Category : Crystal defects
Languages : en
Pages : 16
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Book Description
A transmission electron microscope (TEM) was used to study the neutron irradiation-induced defect structures in zirconium from various sources irradiated to fluences up to 1.3 x 1025 neutrons (n)/m-2 > 0.1 MeV and temperatures in the range 478 to 823 K. Below 673 K the predominant form of damage consists of 1/3 1120 dislocation loops. At higher irradiation temperatures, depending on specimen purity, the defects may include faulted 1/6 2023 loops and voids in addition to the perfect 1/3 1120 loops. The temperature regime of the stability of the various defects was defined. Quantitative measurements showing the effect of irradiation temperature and specimen purity are presented and discussed.
Author:
Publisher: ASTM International
ISBN:
Category :
Languages : en
Pages : 308
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Author: P. M. Kelly
Publisher:
ISBN: 9780642997654
Category : Zirconium alloys
Languages : en
Pages : 9
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