Delayed hydride crack initiation from simulated bearing pad fretting flaws in the rolled joint of pressure tube p3b15 PDF Download
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Author: Z. L. Pan Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Results are presented of mechanical tests on the standard brazed bearing pad and three types of anti-crevice corrosion bearing pad. the tests were performed at conditions representative of static and impact loads on the bearing pads during handling and in-reactor service.
Author: Z. L. Pan Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Results are presented of mechanical tests on the standard brazed bearing pad and three types of anti-crevice corrosion bearing pad. the tests were performed at conditions representative of static and impact loads on the bearing pads during handling and in-reactor service.
Author: Ravi Kumar Sundaramoorthy Publisher: 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.
Author: GK. Shek Publisher: ISBN: Category : Crack initiation Languages : en Pages : 30
Book Description
CANDU Zr-2.5Nb pressure tubes are susceptible to a crack initiation mechanism known as Delayed Hydride Cracking (DHC), which is a process that involves hydrogen diffusion, hydride precipitation, hydride region formation, and fracture at a flaw tip. An overload occurs when the hydrided region is loaded to a stress higher than that at which this region is formed. Service-induced flaws are present in some pressure tubes, which can act as crack initiation sites. Most experimental data to assess DHC initiation are obtained under constant loading conditions in which hydride formation and fracture occur at the same load, and therefore they are not suitable to assess crack initiation under overload condition. A series of step-wise increasing load experiments was performed on unirradiated Zr-2.5Nb pressure tube samples to determine the fracture stress of hydrides formed at notches with 15 ?m root radius under different hydride formation stresses and thermal histories. Crack initiation in the overload tests was detected by the acoustic emission technique. The notch tip hydride morphologies were examined by optical and scanning electron microscopy. Test results indicated that the resistance to overload fracture was dependent on the hydride formation stress and thermal histories, which affected the notch tip hydride size, density, and distribution. Overload tests were performed at different temperatures, and a transition temperature to high resistance to overload fracture was observed.
Author: B. J. S. Wilkins Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Electrical and mechanical transients were used to simulate acoustic emission (ae) signals expected during a crack-growth experiment by temperature-pressure cycling of a pressure tube. electric noise simulated heater noise, while mechanical transients from pencil-lead breaks and ballpoint-pen impacts on a pressure tube, respectively simulated ae from crack growth and mechanical noise in an operating fuel channel. simulations were used, before cycling, to assess the method's capability to discriminate against noise, calibrate instruments for sensitivity, and interpret ae events observed during cycling. digital signal processing (dsp) techniques, using correlation and frequency analyses, were applied to digitized transients. results show that: (i) a spatial filter on the ae instrument provides about 60 db discrimination against extraneous electrical and mechanical noise, (ii) ae bursts from ballpoint-pen impacts and pencil-lead breaks, on a pressure tube, contain low (
Author: R. Choubey Publisher: 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.
Author: Z. L. Pan
Author: Z. L. Pan
Author: Z. Pan
Author: J. H. Van Der Kuur
Author: Ravi Kumar Sundaramoorthy
Author: M. P. Puls
Author: GK. Shek
Author: B. J. S. Wilkins
Author: R. Choubey
Author: J. H. Van Der Kuur
Author: J. H. Van Der Kuur