Study on the Control and Fabrication of Thermal Fatigue Crack for Reliability Enhancement of NDT in Reactor Coolant System
Damages in nuclear facilities during the operation of the Reactor Coolant System (RCS) are caused by cyclic loadings due to mechanical or thermal fatigue. Therefore, the development of an integrated technology including fabrication of standard specimens and their practical usage is needed to enhance the reliability of nondestructive testing for surge lines or main feed water lines. In this study, thermal fatigue cracks on STS 304 plates (t = 6mm) and tubes (O.D = 89.7mm. t = 7.7mm) for performance demonstration inspection were fabricated for the Reactor Coolant System (RCS) in nuclear power plants. In case of plates, cyclic thermal changes, from 20 to 450, were loaded on the V-notched specimens under tensile stressed conditions. The applied tensile stress was 1,700MPa at the notch portion. In the case of tubes, cyclic thermal changes, from 35 to 355, were applied on the V-notched specimens under compressive stressed conditions. In the case of plates, the initial crack was generated at 17,000 cycles and the depth of crack was 2.54mm at 22,000 cycles. Unlike the plates, in the case of tubes, the initial crack formed at 14,000 cycles and the crack penetrated the tube at 25,000 cycles. In this paper, shapes and fractographies of fabricated thermal fatigue cracks, and the used cyclic thermal loads are presented.
Seung-Seok Lee, Joon Hyun Lee, Ik Keun Park, Sung-Jin Song, Man Yong Choi
B. Y. Lee et al., "Study on the Control and Fabrication of Thermal Fatigue Crack for Reliability Enhancement of NDT in Reactor Coolant System", Key Engineering Materials, Vols. 321-323, pp. 739-742, 2006