Irradiation-enhanced deformation of zr-2.5nb tubes at high neutron fluences
Author : A. R. Causey
Publisher :
Page : 0 pages
File Size : 39,90 MB
Release : 2000
Category :
ISBN :
Irradiation-Enhanced Deformation of Zr-2.5Nb Tubes at High Neutron Fluences
Author : RA. Holt
Publisher :
Page : 12 pages
File Size : 19,7 MB
Release : 2000
Category : Creep (materials)
ISBN :
Book Description
The effects of neutron flux and temperature on irradiation creep of 10-mm- diameter Zr-2.5Nb tubes are being assessed in end-of-life experiments in the Osiris reactor in France. The tubes have crystallographic texture, grain shape, and dislocation densities that are similar to those of full-size CANDU reactor pressure tubes. The experiments are performed at nominal operating temperatures of 553 and 583 K in fast neutron fluxes up to 2.0 x 1018 n . m-2 . s-1 (E > 1 MeV). Transverse and axial strains are reported as functions of fluence for specimens internally pressurized to hoop stresses from 0 to 160 MPa and irradiated to fluences up to 1.5 x 1026 and 1.3 x 1026 n . m-2 at 553 and 583 K, respectively. The measured transverse and axial strain rates in these high-fluence experiments are shown to be in good agreement with a creep model relating crystallographic texture to the in-reactor deformation of CANDU pressure tubes. The anisotropy of irradiation creep does not change with fluence, but the temperature dependencies of creep and growth are changing; the activation temperature for creep is increasing, while the magnitude of the activation temperature for irradiation growth (a negative value) is becoming less negative with fluence.
Irradiation-enhanced Creep of zr-2.5nb tubes at high neutron fluences
Author : A. R. Causey
Publisher :
Page : 0 pages
File Size : 38,66 MB
Release : 1998
Category :
ISBN :
Book Description
Irradiation-enhanced Creep of Cold-worked Zr-2.5Nb Tubes and Helical-springs
Author : A. R. Causey
Publisher : Chalk River, Ont. : Reactor Materials Research Branch, Chalk River Laboratories
Page : 34 pages
File Size : 49,49 MB
Release : 1993
Category : Anisotropy
ISBN :
Book Description
This report investigates the anistrophy of irradiation-enhanced creep of cold-worked Zr-2.5Nb at 548-563 K using internally-pressurized capsules and axially loaded helical-springs. The test specimens were machined from small diameter extruded and cold-worked tubing that had crystallographic texture and microstructure similar to that of CANDU power reactor pressure tubes. The biaxial creep capsules and the helical-springs were irradiated for 9,525 and 16,670 hours, respectively, in a fast neutron flux.
High-Fluence Irradiation Growth of Cold-Worked Zr-2.5Nb
Author : RA. Holt
Publisher :
Page : 19 pages
File Size : 10,95 MB
Release : 2000
Category : Iron
ISBN :
Book Description
Irradiation growth specimens manufactured from cold-worked Zr-2.5Nb pressure tube material have been irradiated in Osiris at a fast flux of ~1.8 x 1018 n . m-2 . s-1E > 1 MeV, at nominal temperatures of 553 and 583 K, to growth strains of 1%. The pressure tubes have a pronounced crystallographic texture, with ~95% of the basal plane normals in the radial/transverse plane, predominantly in the transverse direction. Both longitudinal specimens, which generally exhibit positive growth strains, and transverse specimens, which generally exhibit negative strains with approximately 50% of the magnitude of the axial strains, show nonlinear growth, the rate increasing gradually with fluence up to 1.3 x 1026 n . m-2, E > 1 MeV (580 K) and 1.7 x 1026 n . m-2, E > 1 MeV (550 K).
Effect of Stress on Radiation Damage in Neutron Irradiated Zirconium Alloys
Author : CE. Coleman
Publisher :
Page : 19 pages
File Size : 46,94 MB
Release : 1977
Category : Electron microscopy
ISBN :
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.
Microstructural Effects on the Irradiation Growth of Zr-2.5Nb
Author : JD. Parker
Publisher :
Page : 15 pages
File Size : 47,51 MB
Release : 1987
Category : Dislocation substructure
ISBN :
Book Description
Irradiation growth tests at 553 K and a fast (E > 1.6 x 10-13 J) neutron flux of about 6.5 x 1017 n m-2s-1 were performed on specimens of Zr-2.5Nb pressure tubes to a neutron fluence of 3.5 x 1025 n m-2. The tubes were produced by different routes designed to change texture, grain shape, and dislocation density, but X-ray diffraction studies showed only minor changes in texture and dislocation density. However, electron microscopy revealed marked differences in dislocation substructure and second-phase distribution.
Influence of Neutron Irradiation on Dislocation Structure and Phase Composition of Zr-Base Alloys
Author : VN. Shishov
Publisher :
Page : 20 pages
File Size : 48,15 MB
Release : 1996
Category : Composition
ISBN :
Book Description
Studied were evolution of dislocation structure, phase, and element composition of binary alloys Zr-1Nb and Zr-2.5Nb and multicomponent alloys Zr-1Nb-1.2Sn-0.4Fe and Zr-1.2Sn-0.4Fe under neutron irradiation. The investigations were carried out using cladding and pressure tubes before and after irradiation to a fluence of ~1026 n/m2 (E >= 0.1 MeV) in experimental and commercial reactors at 300 to 350°C using TEM, EDX, and XRD. In most cases, irradiation-induced defects are in the form of dislocation loops with Burgers vector 1/3 ?1120?. The density of dislocations with a ?c? component is less than 2 x 1014 m-2. A higher fluence or the presence of strain results in the ordering of the dislocation structure of ?c? component and ?a?-type dislocation loops. Before irradiation, the multicomponent alloys contain fine precipitates of Zr-Nb-Fe composition, and the matrix is depleted in Fe. Under irradiation, recrystallization proceeds intensively (as distinct from Zr-Nb alloys), changes take place in size, distribution, and composition of precipitates (with a relative decrease of Fe content compared to Nb), and the Fecontent of ?-Zr matrix is increased. None of the materials studied showed any significant evidence of secondary phase particle amorphization. The density of dislocations with ?a? and ?c? components and irradiation-induced defects, their mean size, the extent of ordering, and the planes of their occurrence were determined. A comparison was made between irradiation-induced evolutions of microstructures of the different alloys.
Damage Stucture in Zirconium Alloys Irradiated at 573 to 923°K. [Neutron Fluence 1 X 1025 N. M−2].
Author :
Publisher :
Page : pages
File Size : 11,39 MB
Release : 1978
Category :
ISBN :
Book Description
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.
The Effects of Microstructure and Operating Conditions on Irradiation Creep of Zr-2.5Nb Pressure Tubing
Author : L. Walters
Publisher :
Page : 33 pages
File Size : 16,14 MB
Release : 2014
Category : In-reactor deformation
ISBN :
Book Description
Creep experiments have been performed on biaxially stressed 10 mm diameter Zr-2.5Nb capsules. As the pressurized capsules were obtained from micro-pressure tubes, which were fabricated by the same process as CANDU power reactor pressure tubes, they have a similar microstructure to that of the full-size tubes. The experiments were performed in the OSIRIS test reactor at nominal operating temperatures ranging from 553 and 613 K in fast neutron fluxes up to 2 x 1018 n.m-2.s-1 (E > 1 MeV). Diametral and axial strains are reported as functions of fluence for specimens internally pressurized to hoop stresses from 0 to 160 MPa and irradiated to 26.5 dpa. The effects of microstructure, temperature, and cold work on irradiation creep are shown. The analysis of OSIRIS data combined with data from in-service CANDU tubes has revealed some significant observations regarding pressure tube deformation: (i) that irradiation creep anisotropy varies with temperature, (ii) texture appears to have a more significant effect on axial creep than on diametral creep, (iii) diametral strain appears to be strongly dependent on grain size and aspect ratio, and (iv) that whereas cold-work correlates with the axial creep of the capsules, there appears to be no statistically significant dependence of diametral creep on cold-work.
