Thermal fatigue evaluation method considering fluid-structure interaction against fluid temperature fluctuation

Kasahara, Naoto; Kawasaki, Nobuchika ; Kamide, Hideki ; Sakai, Shinsuke*; Okajima, Satoshi*

Fluid temperature fluctuates at an incomplete mixing area of high and low temperature fluids in nuclear components. It induces random variations of local temperature gradients in structural walls, which lead to cyclic thermal stresses. When thermal stresses and cycle numbers are large, there are possibilities of fatigue crack initiations and propagations. It is recognized that there are attenuation factors depending on fluctuation frequency in the transfer process from fluid temperature to thermal stresses. Considering above fluid-structure interaction against fluid temperature fluctuation, authors has proposed a fatigue evaluation method related to frequencies. JAEA has the plan to develop thermal load modeling guidelines, which has consistency with JSME guidelines for light water reactors.