Lifetime evaluation of cracked shaft sleeve of reactor coolant pump under thermal striping

Thermal striping of a shaft sleeve of a reactor coolant pump at a nuclear p ower plant is caused by incomplete mixing of the low temperature cooling wa ter flow from water seals and high temperature cooling water flow from the reactor. Temperature fluctuation results in a significant thermal fatigue d amage and therefore, a network of longitudinal cracks is found on the outer surface of sleeve. After conservative computation and evaluation by consid ering thermal and mechanical stresses and fracture mechanics, it was found that the crack on the surface of sleeve will become deeper according to hig h frequency fatigue model if the depth of the crack is larger than 10% of s leeve wall thickness. Although the sleeve will not break dramatically befor e one crack through the wall of sleeve they may combine with one another an d cause damage to the sleeve. Therefore, in this paper the life time of the sleeve is assumed to be the time needed for one crack to propagate through the wall of the sleeve. The life assessment for the sleeve, subject to sur face temperature fluctuation, is presented. (C) 2001 Elsevier Science Ltd. All rights reserved.