Aseismic design and it's test of multiwalled pipings for an elevated temperature helium gas cooling system

Multiwalled pipings are used for the inpile gas loop, named ''OGL-1'', of which maximum helium gas temperature is 1,0000C. Authors carried out the vibration test of the inpile tube and the multiwalled pipings, and obtained the natural frequencies and damping ratios of which were compared with the design values. It is confirmed that the vibration of the inpile tube is not induced by the cooling water flow. After the vibration test, the multiwalled pipings are analyzed further as single-walled pipings using some assumptions which are included in the effect of the supporting structure. The obtained natural frequencies and vibration modes by analyses coincide with the measured values. The obtained damping ratio of the multiwalled pipings and tube shows the design value 0.5% is very conservative