The development of three-dimensional structure analysis method of the dished tubesheets

Takasho, Hideki*; Kasahara, Naoto; Kazuteru Garatani/CRC Solution*

Commercialized fast reactors, intend to adopt large scale heat exchangers, since they aim at capacity enlargement and reduction of the cooling loops from a demand of the economical efficiency. And, they have planned the adoption of the double-wall heat transfer tubes for reliable design against sodium coolant, which become straight type without tube welding. As the result, steam generators change to large double straight pipe types and the large-scale dished tubesheets are required from a balance with the pressure proof design. The establishment of method of structural analysis for the complicated and three-dimensional shape is required in order to realize the large-scale dished tubesheets. Conventional analysis models for tubesheets are equivalent solid plates with stress multipliers, which are difficult to be applied to dished tubesheets since their un-homogeneity. A large-scale three-dimensional analysis model is desirable to consider precious configurations around holes.. The iterative solver for efficiently calculating, when the large-scale analysis is carried out, was developed, and it was mounted to FINAS code. A dished tubesheet model for commercialized fast reactors was made in three-dimensional element which exceeded 1 million degrees of freedom. FINAS code with the iterative solver analyzed thermal transient stress under the manual trip condition. 20 step calculation was carried out within 72 hours on PC. As the result, it was confirmed that applicability of three dimensional analysis methods to dished tubesheets.