13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- changes only 0.5 K, it is obvious that the temperature variation with burnup is very slight with a constant irradiation condition. Meanwhile, from comparison of the results along Path 1 and Path 2, it can be found that the maximum temperature in Path 1 is about 9K higher than the one in Path 2, which is for the reason that Path 2 is closer to the coolant water. (a) (b) Figure.3 (a) Temperature distribution at 144.1days and (b) the paths to output the results 0 100 200 300 400 588 591 594 597 600 603 606 609 612 615 1.1days-path1 with uniform irradiation condition Temperature(K) Distance along path(mm) 134.1days-path1 58.3days-path1 1.1days-path1 1.1days-path2 Figure. 4 Temperature distribution in the fuel meat 4.3. Mechanical behaviors in the cladding The cladding is the first barrier to keep the radioactive substance from leakage. It’s of huge importance to maintain its integrity. For the metal material, the Mises stress is firstly concerned. The contour plot at 144.1days is given in Fig.5. One can see that a stress concentration zone exists in the corner of cladding with the largest Mises stress reaching 468.4MPa, which is caused by the fixed boundary condition. To investigate the Mises stress distribution in the zone, two paths were taken in Fig.6. Through comparison of the results on path1 and path2, it can be discovered that path1 has slightly higher Mises stress than path2, as is shown in Fig. 6(a). Also, one can find that with increasing time the Mises stress demonstrate the same variation law on path1 as that the maximum numerical result always appears at the tip of the stress concentration zone. Meanwhile, from 29.7days to 144.1days, the maximum Mises stress on path1 increases from 341.52MPa to 465.4MPa. Observation of Mises stress distribution in the cladding part with the fuel meat
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