Author: G. K. Shek
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Round robin studies of delayed hydride crack velocity in zr-2.5 nb pressure tubes
Delayed hydride crack velocities in zr-2.5 nb pressure tubes at high stress intensity factors
Effects of thermal history on delayed hydride crack velocity in zr-2.5 nb pressure tubes at 130 degrees c - interim report
Initiation of Delayed Hydride Cracking in Zr-2.5Nb Micro Pressure Tubes
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.
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.
Delayed Hydride Cracking Velocity and Crack Growth Measurement Using DCPD Technique in Zr-2.5Nb Pressure Tube Material
IAEA Co-ordinated Research Program: "Round Robin" on Measuring the Velocity of Delayed Hydride Cracking (DHC)
Delayed hydride cracking (dhc) velocity (axial) at 250 degrees celsius for zr-2.5nb chepetski pressure tube materials
Threshold stress intensity factor for delayed hydride cracking at 250 degrees c in zr-2.5nb pressure tube material supplied by cezus
Crack initiation at long radial hydrides in zr-2.5 nb pressure tube material at elevated temperatures
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.
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.