Influence of hydrogen content on fracture toughness of CWSR Zr–2.5Nb pressure tube alloy

Effect of direction of approach of test temperature on fracture toughness of Zr–2.5Nb pressure tube material

“…Being brittle, the presence of substantial quantities of hydrides can cause embrittlement of the host matrix resulting in loss of ductility, impact and fracture toughness. Both impact and fracture toughness of this alloy shows strong influence of hydrides below 150 1C [8][9][10] and above 150 1C, the influence of hydrides on impact [8] and fracture toughness [9,10] is insignificant.…”

“…The polished tube was charged gaseously with target hydrogen content of 100 ppm by weight in a modified Sievert's apparatus [21]. The standard Curved Compact Toughness (CCT) specimens of width 17 mm were machined using EDM wire cutting for fracture toughness evaluation [9,10]. Total 24 samples were prepared for fracture toughness evaluation.…”

“…In most of the cases, the test temperatures for carrying out elevated temperature impact and fracture toughness tests [8][9][10][15][16][17][18][19] are attained by heating the samples from ambient temperature to the test temperature. The stress field imposed on matrix by hydride is expected to depend on whether hydride is expanding (as happens during cooling) or contracting (as happens during heating) [11,20].…”

Influence of loading rate and hydrogen content on fracture toughness of Zr-2.5Nb pressure tube material

“…The critical crack-length (CCL) values for the catastrophic failure of the pressure tube under PHWR operating conditions were computed by matching the crack-driving force (CDF) modified by Folias factor (M) to the crack-growth resistance of the material. This was achieved by using J max values as crack-growth resistance of the material and by following an iterative method [8,9]. The aforementioned fracture toughness parameters were determined as a function of the hydrogen content and pulling rate in the temperature range of 25e300 C. For metallography, the specimens were sectioned along the radialecircumferential (RC) and the axial-radial (AR) planes of the pressure tube.…”

“…To meet LBB criteria, the critical crack length (CCL) causing catastrophic failure of the pressure tube should be sufficiently large. The CCL is calculated using fracture toughness parameters mainly J max [8,9] and tangency criteria [9,11]. There is no data available in literature showing the effect of loading rate on the fracture toughness of the Zr-2.5Nb pressure tube material.…”