PURPOSE: To shorten construction period of the supporting and containing structure of a reactor pressure vessel.

CONSTITUTION: Outside the pedestal 3 of an RPV(reactor pressure vessel), column supports 18 are stood and fixed at specific intervals. By using the column support 18, diaphragm floor 11 for separating upper drywell 12 and a suppression chamber 9 is laid. On the diaphragm floor 11, a pipe whip structure 13 is placed. The liner construction on the side wall 5 of the containment is preceded iron construction. By leaving the column support 18, a top slab 6 is put on the upper end of the side wall 5 to complete a reactor containment 7.