The necking riser is used at the top of the spent fuel container, and the riser is designed according to the sectional proportion method.
The wall thickness of spent fuel container made of ductile iron is 520mm
Dr = 0.6 ＞＜ 520 = 312mm, rounded to 320mm;
HR = 1.5 ＞＜ 520 = 624mm, rounded to 630mm;
B = 0.55×320 = 176mm, rounded 180mm
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Through calculation, the weight of single riser is 557kg. For ductile iron castings, the top reducing riser is only used for liquid phase shrinkage. The expansion and self feeding effect of graphite should be fully exerted, so the number of risers should be reduced as much as possible. The shrinkage of liquid phase of ductile iron is about 0.8% – 1%
Total weight of riser = 135500×0.9% = 1355kg
The number of risers = 2.39, rounded to 2.