Critical Temperatures for Initiating and Arresting Delayed Hydride Cracking in a Zr-2.5Nb Pressure Tube

2005 ◽  
Vol 297-300 ◽  
pp. 1685-1690
Author(s):  
Young Suk Kim ◽  
Kyung Soo Im ◽  
Yong Moo Cheong
Keyword(s):  
Hydrogen Concentration ◽  
Solid Solubility ◽  
Driving Force ◽  
Stress Gradient ◽  
Zirconium Alloys ◽  
Concentration Limit ◽  
Critical Temperatures ◽  
Terminal Solid Solubility ◽  
Delayed Hydride Cracking ◽  
Hydride Cracking

The hydrogen concentration limit and critical temperatures for a delayed hydride cracking (DHC) in zirconium alloys have been reanalyzed using Kim’s DHC model that a driving force for DHC is not the stress gradient but the supersaturated hydrogen concentration or ∆C arising from a hysteresis of the terminal solid solubility on a heating and on a cooling. The DHC initiation occurs generally at the temperatures corresponding to the terminal solid solubility for precipititation (TSSP), demonstrating that the supercooling from the terminal solid solubility for dissolution (TSSD) is required to initiate the DHC. The DHC arrest temperatures correspond to the temperatures where the ∆C is reduced to zero. Therefore, we conclude that the ∆C is the driving force for the DHC and that the Kim’s DHC model is feasible.

Initiation and Arrest of Delayed Hydride Cracking in Zr-2.5Nb Tubes

2006 ◽  
Author(s):  
Young S. Kim ◽  
Sang B. Ahn ◽  
Yong M. Cheong
Keyword(s):  
Hydrogen Concentration ◽  
Solid Solubility ◽  
Thermal Cycle ◽  
Driving Force ◽  
Critical Temperatures ◽  
Terminal Solid Solubility ◽  
Delayed Hydride Cracking ◽  
Hydride Cracking

Using Kim’s delayed hydride cracking (DHC) model, this study reanalyzes the critical temperatures for DHC initiation and arrest in Zr-2.5Nb tubes that had previously been investigated with Dutton and Puls’s DHC model. At temperatures over 180 °C along with a hydrogen concentration of over 15 ppm H, the DHC initiation in a CANDU Zr-2.5Nb tube was suppressed, which required a cooling or ΔT from the terminal solid solubility for dissolution (TSSD) temperatures. With the number of the thermal cycle increasing, the DHC initiation temperatures or Tcs gradually shifted towards the TSSD. At a hydrogen concentration as low as 7 ppm H and temperatures lower than 180 °C, a DHC initiation occurred at temperatures near the TSSD with little ΔT. Different DHC initiation temperatures with hydrogen concentrations are discussed in view of precipitation of hydrides in the zirconium matrix either by a cooling or by a stress-induced γ- to δ-hydride transformation. The DHC arrest temperatures were governed by the critical supersaturated hydrogen concentration or ΔC regardless of the thermal cycle treatment. By correlating the DHC cracking and arrest temperatures with the supersaturated hydrogen concentration or ΔC for the DHC cracking and arrest, we conclude that the ΔC arising from the hysteresis of the terminal solid solubility of hydrogen on a heat-up and on a cool-down is the driving force for the DHC.

Initiation and Arrest of Delayed Hydride Cracking in Zr–2.5Nb Tubes

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Young S. Kim
Keyword(s):  
Hydrogen Concentration ◽  
Solid Solubility ◽  
Thermal Cycle ◽  
Bulk Region ◽  
Critical Temperatures ◽  
Concentration Difference ◽  
Terminal Solid Solubility ◽  
Delayed Hydride Cracking ◽  
Increasing Temperature ◽  
Hydride Cracking

Using Kim’s delayed hydride cracking (DHC) model, this study reanalyzes the critical temperatures for DHC initiation and arrest in Zr–2.5Nb tubes that had previously been investigated with the previous DHC models. At the test temperatures above 180°C, DHC initiation temperatures fell near the terminal solid solubility for precipitation temperatures, requiring some undercooling or ΔT from the terminal solid solubility for dissolution (TSSD) temperatures, and increased toward TSSD with the number of thermal cycles. At the test temperatures below 180°C, DHC initiation occurred at temperatures near TSSD with little ΔT. DHC arrest occurred on heating toward TSSD where the hydrogen concentration difference between the bulk region and a crack tip ΔC decreased to a minimum ΔCmin, under which nucleation of the hydrides was restrained. ΔCmin after the first thermal cycle increased with increasing temperature, demonstrating that nucleation of the hydrides becomes more difficult with increasing temperatures. Different DHC initiation and arrest temperatures with the test temperatures or hydrogen concentrations are discussed in view of a supersaturation of hydrogen (ΔC) for nucleation of hydrides in the zirconium matrix.

scholarly journals Hydride Rim Formation in E110 Zirconium Alloy during Gas-Phase Hydrogenation

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 247
Author(s):  
Viktor Kudiiarov ◽  
Ivan Sakvin ◽  
Maxim Syrtanov ◽  
Inga Slesarenko ◽  
Andrey Lider
Keyword(s):  
Mechanical Properties ◽  
Gas Phase ◽  
Zirconium Alloy ◽  
Zirconium Alloys ◽  
Subsequent Formation ◽  
Delayed Hydride Cracking ◽  
Hydrogen Penetration ◽  
Significant Change ◽  
Hydride Cracking

The work is devoted to the study of the laws of the formation of a hydride rim in E110 zirconium alloy claddings during gas-phase hydrogenation. The problem of hydrogen penetration and accumulation and the subsequent formation of hydrides in the volume of zirconium cladding tubes of water-cooled power reactors remain relevant. The formation of brittle hydrides in a zirconium matrix firstly, leads to a significant change in the mechanical properties, and secondly, can cause the destruction of the claddings by the mechanism of delayed hydride cracking. The degree of the hydride’s effect on the mechanical properties of zirconium cladding is mainly determined by the features of the hydride’s distribution and orientation. The problem of hydride rim formation in zirconium alloys with niobium is quite new and poorly studied. Therefore, the study of hydride rim formation in Russian zirconium alloy is important and necessary for predicting the behavior of claddings during the formation of the hydride rim.

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