Author: Ahmed Fathi ShalabiPublisher:
ISBN:
Category : Cracking process
Languages : en
Pages : 490
Book Description
Initiation of Delayed Hydride Cracking in Zirconium-2.5 Wt.% Niobium Pressure Tubes
Author: Ahmed Fathi ShalabiPublisher:
ISBN:
Category : Cracking process
Languages : en
Pages : 490
Book Description
Initiation of Delayed Hydride Cracking in Zr-2.5Nb Micro Pressure Tubes
Author: Ravi Kumar SundaramoorthyPublisher:
ISBN:
Category :
Languages : en
Pages : 280
Book Description
Pressure tubes pick up hydrogen while they are in service within CANDU reactors. Sufficiently high hydrogen concentration can lead to hydride precipitation during reactor shutdown/repair at flaws, resulting in the potential for eventual rupture of the pressure tubes by a process called Delayed Hydride Cracking (DHC). The threshold stress intensity factor (KIH) below which the cracks will not grow by delayed hydride cracking of Zr-2.5Nb micro pressure tubes (MPTs) has been determined using a load increasing mode (LIM) method at different temperatures. MPTs have been used to allow easy study of the impact of properties like texture and grain size on DHC. Previous studies on MPTs have focused on creep and effects of stress on hydride orientation; here the use of MPTs for DHC studies is confirmed for the first time. Micro pressure tube samples were hydrided to a target hydrogen content of 100 ppm using an electrolytic method. For DHC testing, 3 mm thick half ring samples were cut out from the tubes using Electrical Discharge Machining (EDM) with a notch at the center. A sharp notch with a root radius of 15 mu m was introduced by broaching to facilitate crack initiation. The direct current potential drop method was used to monitor crack growth during the DHC tests. For the temperature range tested the threshold stress intensity factors for the micro pressure tube used were found to be 6.5-10.5 MPa.m1/2 with the value increasing with increasing temperature. The average DHC velocities obtained for the three different test temperatures 180, 230 and 250oC were 2.64, 10.87 and 8.45 x 10-8 m/s, respectively. The DHC data obtained from the MPTs are comparable to the data published in the literature for full sized CANDU pressure tubes.
The Initiation of Delayed Hydride Cracking in Zirconium-2.5 Niobium
Author: Delayed Hydride Cracking in Zirconium Alloys in Pressure Tube Nuclear Reactors
Author: International Atomic Energy AgencyPublisher: IAEA
ISBN:
Category : Business & Economics
Languages : en
Pages : 102
Book Description
Dated October 2004. With CD-ROM containing additional information inside back cover
Initiation of Delayed Hydride Cracking in Zirconium-2.5 Niobium
Author: Douglas Keith RodgersPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Delayed Hydride Cracking (DHC) occurs in Zr-2.5Nb when certain requirements are met. The mechanism of DHC consists of diffusion of hydrogen to a stress concentrator, such as a crack-tip, precipitation then fracture of a hydride at the crack-tip, and repetition of the process; the crack advances in steps. Incubation times, to the start of cracking and crack-tip hydride morphologies have been measured in pre-cracked cantilever beam specimens tested at applied K$\rm\sb I$'s up to 20 MPam$\sp{1/2}$ and temperatures ranging from 100 to 250$\sp\circ$C. The incubation time for DHC was found to vary inversely with DHC velocity. Contrary to previous research, the incubation time is highly variable, even for a given temperature and applied K$\rm\sb I,$ and the crack-tip hydride morphology is much more complicated than the simple model of a single hydride at a crack-tip.
Crack initiation at long radial hydrides in zr-2.5 nb pressure tube material at elevated temperatures
Author: R. ChoubeyPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Deuterium buildup in pressure tubes arises as a consequence of corrosion on pressure tube surfaces exposed to both the primary coolant and annulus gas. because there is a potential for pressure tube failure by delayed hydride cracking once the solubility limit for hydrogen isotopes in the pressure tube material is exceeded, there is a need to develop a predictive capability for corrosion and deuterium ingress in candu pressure tubes. this predictive capability is being set up through the development of a design equation, beginning with simple empirical correlations but evolving as a model with an increasingly more mechanistic basis as our understanding of the physical processes involved improves. the preliminary version of the design equation described here attempts to account for the observed effects of temperature, neutron flux and water chemistry on corrosion in the primary coolant. functional relationships describing how corrosion varies with temperature, oxide thickness, dissolved oxygen in the water and irradiation are derived using data from out-reactor autoclave tests, in-reactor loop tests and out-reactor autoclave tests using pre-irradiated pressure tube material. deuterium uptake by the pressure tube is accounted for as a percentage of the total amount of deuterium released through the corrosion process. reasonable agreement between predictions of oxide thickness and deuterium concentrations in pressure tubes with actual measurements from bruce pressure tube surveillance examinations is encouraging. the current model predicts that the rate of deuterium ingress in pressure tubes is not constant but increasing with time.
The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components
Author: Manfred P. PulsPublisher: Springer Science & Business Media
ISBN: 1447141954
Category : Science
Languages : en
Pages : 475
Book Description
By drawing together the current theoretical and experimental understanding of the phenomena of delayed hydride cracking (DHC) in zirconium alloys, The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Components: Delayed Hydride Cracking provides a detailed explanation focusing on the properties of hydrogen and hydrides in these alloys. Whilst the emphasis lies on zirconium alloys, the combination of both the empirical and mechanistic approaches creates a solid understanding that can also be applied to other hydride forming metals. This up-to-date reference focuses on documented research surrounding DHC, including current methodologies for design and assessment of the results of periodic in-service inspections of pressure tubes in nuclear reactors. Emphasis is placed on showing how our understanding of DHC is supported by progress in general understanding of such broad fields as the study of hysteresis associated with first order phase transformations, phase relationships in coherent crystalline metallic solids, the physics of point and line defects, diffusion of substitutional and interstitial atoms in crystalline solids, and continuum fracture and solid mechanics. Furthermore, an account of current methodologies is given illustrating how such understanding of hydrogen, hydrides and DHC in zirconium alloys underpins these methodologies for assessments of real life cases in the Canadian nuclear industry. The all-encompassing approach makes The Effect of Hydrogen and Hydrides on the Integrity of Zirconium Alloy Component: Delayed Hydride Cracking an ideal reference source for students, researchers and industry professionals alike.
Author: B. A. Cheadle
Author: M. P. Puls
Author: G. K. Shek