The effect of neutron fluence on the Creep and growth of annealed zircaloy-4 at 340 k PDF Download
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Author: A. R. Causey
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Category :
Languages : en
Pages : 0
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Book Description
The possibility of accelerating creep at low temperature in annealed zircaloy at high fluences, similar to previously reported growth 'breakaway' behaviour at temperatures above 500 k, has been investigated at 340 k using stress relaxation and irradiation growth tests on annealed zircaloy-4 pre-irradiated at 580 k to 5 x 10sup(24) and 8 x 10sup(25) n.m-2 e1 mev. test results suggest that both creep and growth rates are higher for the specimens pre-irradiated to the higher fluence, however, the stress relaxation data are not conclusive. the presence of c component dislocations, revealed by transmission electron microscopy, only in the high fluence material has been related previously to the growth 'breakaway' at 580 k, and appears to result in higher growth and creep rates at 340 k.
Author: A. R. Causey
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ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The possibility of accelerating creep at low temperature in annealed zircaloy at high fluences, similar to previously reported growth 'breakaway' behaviour at temperatures above 500 k, has been investigated at 340 k using stress relaxation and irradiation growth tests on annealed zircaloy-4 pre-irradiated at 580 k to 5 x 10sup(24) and 8 x 10sup(25) n.m-2 e1 mev. test results suggest that both creep and growth rates are higher for the specimens pre-irradiated to the higher fluence, however, the stress relaxation data are not conclusive. the presence of c component dislocations, revealed by transmission electron microscopy, only in the high fluence material has been related previously to the growth 'breakaway' at 580 k, and appears to result in higher growth and creep rates at 340 k.
Author: BF. Kammenzind
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Category : Irradiation
Languages : en
Pages : 27
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Book Description
Analytical electron microscopy (AEM) was used to study the separate effects of the irradiation parameters on the evolution of the microstructure in recrystallized alpha-annealed Zircaloy-4 under controlled irradiation conditions. The effects of fast neutron flux from ~4 x 1013 n/cm2-s to ~1.5 x 1014 n/cm2-s (E > 1 MeV)3 neutron fluence in the range of ~15 x 1020 n/cm2 to ~50 x 1020 n/cm2 and temperature from ~270 to ~330°C were studied. The completeness of the test matrix and the exposure in the controlled environment of the advanced test reactor permitted the separate effects of fast neutron flux, fluence, and irradiation temperature to be delineated for the first time. It was found that an increase in the neutron flux increases the degree of amorphization of the second-phase precipitates but retards the redistribution of iron out of the amorphous region (neutron fluence and irradiation temperature remaining the same), whereas increasing temperature (neutron flux and neutron fluence remaining the same) has a reverse effect. Overall, the rate of amorphization of the second-phase precipitates observed in this work was larger than that predicted by many existing literature models. Finally, neither segregation of alloying elements to grain boundaries nor precipitation of any new phases were encountered.
Author: F. Garzarolli
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Category : Fluence
Languages : en
Pages : 17
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Book Description
Irradiation of Zircaloy affects its microstructure and macroscopical properties, for example, influencing its irradiation growth. To gain more insight into these phenomena, experimental fuel rods and growth specimens with various fabrication parameters were irradiated in a pressurized water reactor (PWR) to high fluences. Some of the growth specimens were exposed to a fast neutron fluence of up to 2.3 x 1022 cm-2 (?0.82 MeV) over a period of 10 years. Following exposure, the irradiation-induced alterations of the microstructure and the intermetallic precipitates were studied by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). At a temperature of 300°C during irradiation to fluences up to 7 x 1021 cm-2, growth increases with increasing yield strength. Recrystallized material, which has a low yield strength, exhibits an increased growth rate at very high fluences (?1 x 1022 cm-2). Postirradiation annealing studies indicate that the early irradiation growth of the recrystallized material can be recovered, whereas the later accelerated growth does not seem to be recoverable.
Author:
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Category : Nuclear energy
Languages : en
Pages : 736
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Author: R. W. L. Fong
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Category :
Languages : en
Pages : 0
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Book Description
The possibility of accelerating creep at low temperature in annealed zircaloy at high fluences, similar to previously reported growth 'breakaway' behaviour at temperatures above 500 k, has been investigated at 340 k using stress relaxation and irradiation growth tests on annealed zircaloy-4 pre-irradiated at 580 k to 5 x 10sup(24) and 8 x 10sup(25) n.m-2 e1 mev. test results suggest that both creep and growth rates are higher for the specimens pre-irradiated to the higher fluence, however, the stress relaxation data are not conclusive. the presence of c component dislocations, revealed by transmission electron microscopy, only in the high fluence material has been related previously to the growth 'breakaway' at 580 k, and appears to result in higher growth and creep rates at 340 k.
Author: OJV Chapman
Publisher:
ISBN:
Category : Alloys
Languages : en
Pages : 32
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Book Description
Proton irradiation creep and in-pile creep and growth tests have been conducted on specimens cut from the same rolled and annealed Zircaloy-2 plate. The proton irradiation creep tests were carried out over the following ranges: stress, 0 to 267 MPa; damage rate, 0.15 to 7.0 x 10-7 dpa/s; temperature, 513 to 613 K; and dose, up to 1.44 dpa.
Author: RB. Adamson
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Category : Annealed
Languages : en
Pages : 27
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Irradiation growth behavior of Zircaloy-2 and -4 was studied on specimens irradiated in the Experimental Breeder Reactor II to fluences of 1.4 to 6.3 x 1025 neutrons (n).m-2 (E > 1 MeV) in the temperature range 644 to 723 K. Measurements in the three principal directions on annealed and cold-worked/stress-relieved Zircaloy-2 slab materials provided evidence that growth is a constant-volume process up to about 680 K. The growth strains were shown to be determined by the crystallographic texture, that is, proportional to (1-3(1-3fdc)), where), where fdc is the fraction of basal poles, is the fraction of basal poles, fc, in the direction d. The growth strains for annealed and cold-worked Zircaloy were large relative to previously reported data, were similar in magnitude, were strongly dependent on irradiation temperature, and varied linearly with fluence over the range investigated. Transmission electron microscopy on annealed Zircaloy-4 specimens revealed a few small voids and larger cavities, a grain boundary second phase, and dislocation loops, tangles, and arrays. The high growth strains in annealed Zircaloy appear to be governed by dislocation arrays formed during irradiation. This implies a change in growth mechanism from that pertaining at lower temperatures in annealed material. The data suggest a transition from saturating steady-state growth at lower temperatures to increasing and eventually high steady-state rates under the conditions of these tests.
Author:
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Category : Metallurgy
Languages : en
Pages : 732
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Author: EC. Darby
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ISBN:
Category : Alloys
Languages : en
Pages : 18
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The irradiation growth behavior of annealed polycrystalline Zircaloy-2 has been investigated in the DIDO reactor at Harwell at fluences up to 1 x 1025 neutrons (n)m-2 (E > 1 MeV) and in the temperature range 513 to 673 K. Growth strain data for two batches of rolled, annealed Zircaloy plate did not obey the G ? (1 - 3f) texture relationship with transverse direction specimens (f = 0.25 and f = 0.35) exhibiting negative growth following an initial positive transient. The effect of irradiation temperature on growth was not marked over the range studied except that, at 673 K, growth strains appeared to saturate at low fluences. Apart from this, longitudinal and transverse growth strains decreased slightly with increasing temperature above 573 K. Specimens of large grained, ?-annealed Zircaloy with a completely random structure showed virtually no sensitivity of growth to either fluence or temperature under the conditions studied. The apparently anomalous growth behavior of the transverse annealed plate materials cannot be explained by the influence of density changes during growth. It is proposed that the deviation from the expected growth-texture relationship is due to the effects of intergranular stresses which occur as a result of, and in opposition to, irradiation growth in polycrystalline materials.
Author: WJS Yang
Publisher:
ISBN:
Category : Amorphous transformation
Languages : en
Pages : 15
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Book Description
Zircaloy-4, a zirconium base alloy used extensively as cladding and core structural material in water cooled nuclear reactors, was examined by transmission electron microscopy after neutron irradiation and postirradiation annealing. Phase instabilities found during irradiation include the amorphous transformation and the dissolution of intermetallic precipitate Zr(Fe,Cr)2 in the ?-recrystallized matrix and the dissolution of the metastable precipitate Zr4(Fe,Cr) in the ?-quenched matrix. The alloy is driven toward a single phase solid solution during the irradiation. The presence of fast diffusion iron species in the matrix due to the precipitate dissolution may have caused the irradiation growth breakaway phenomenon. The microstructural evolution during irradiation consists of ̄c dislocation development and grain boundary migration. The presence of ̄c dislocations indicates permanent strain in the matrix. The postirradiation annealing at 833 K does not anneal out the ̄c dislocations. The ̄c dislocation is postulated to have developed due to the intergranular constraints under the continuous growth in the breakaway region.
