Irradiation Creep of Zr-Alloys

Microstructural Effects on Irradiation Creep of Reactor Core Materials

“…The mechanistic modelling of irradiation creep by slip and diffusional mass transport are complex and are outlined in the supplementary material for the case of Zr-2.5Nb pressure tubing, which is the focus of the modelling outlined in Section 3.4 . As sink strengths for point defects are central to rate theory, the typical microstructures for cold-worked pressure tubes are first described and illustrated in Section S2 [ 8 , 10 , 50 , 72 , 73 ], Figures S1–S4 . To make a case for diffusional mass transport one must understand the strengths and shortcomings of dislocation slip.…”

“…The role of dislocation slip is discussed in Section S3; firstly with respect to the potential effect of gliding prismatic dislocation loops on creep [ 8 , 76 , 77 , 78 ], Figure 5 , and then with respect to the glide by network dislocations in a polycrystalline material [ 5 , 6 , 18 , 24 , 25 , 26 , 48 , 49 , 70 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 ], Figures S6–S11 . Finally, the fundamentals of rate theory are described by formulating a set of simple balance equations for dislocations [ 9 , 43 , 69 , 71 , 88 , 89 ], Figure S12 , and then for grain boundaries [ 10 , 50 ], Figure S13 .…”

“…The evolution in the creep response at high doses is apparent from published creep rates for creep capsules [ 26 , 49 ] and pressure tubing [ 50 ], and is plotted in Figure 6 [ 10 ]. It is clear from Figure 6 that the irradiation creep rate as a function of dose is continually decreasing over a large dose range.…”

“…Two types of models have been applied in two different studies, one empirical [ 22 ] and one semi-empirical [ 25 ]. In both cases the creep was shown to be strongly dependent on variations in grain structure [ 49 , 50 ]. Even though front-to-back variations in texture and grain structure are subsumed into the temperature term in [ 22 ] and the front-to-back variation in grain structure was accounted for by the K 4 ( x ) term in [ 25 ], the normalisation models for operating conditions allow for the assessment of the relative creep rates of different pressure tubes at the same axial locations [ 49 , 50 ].…”

“…In both cases the creep was shown to be strongly dependent on variations in grain structure [ 49 , 50 ]. Even though front-to-back variations in texture and grain structure are subsumed into the temperature term in [ 22 ] and the front-to-back variation in grain structure was accounted for by the K 4 ( x ) term in [ 25 ], the normalisation models for operating conditions allow for the assessment of the relative creep rates of different pressure tubes at the same axial locations [ 49 , 50 ]. Using grain dimensions, crystallographic texture and dislocation density, a rate theory model was developed that accounted for the relative irradiation creep behaviour of different tubes based on differences in microstructure [ 49 , 50 ].…”