STRUCTURAL INTEGRITY TEST OF HELICAL-TYPE INTERMEDIATED HEAT-EXCHANGER

An intermediate heat exchanger (IHX) for the High Temperature Engineer ing Test Reactor (HTTR) is an important component of the cooling syste m and it is important to confirm the structural integrity. Particularl y, a connecting tube would be subjected to thermal stress caused by th e difference of thermal expansion and temperature between the manifold and the helical tube and is under severe design condition which is us ed in over 900 degrees C in normal operation. The structural integrity test of an in-scale model consisted of the manifold and the lower con necting tube of the IHX for the HTTR was carried out under accelerated condition of the normal operation. From the present study, the crack was observed to have grown through the wall of the tube in two heat tr ansfer tubes. The coil portion and the lower elbow portion of the heat transfer tube slightly hung down and the lower connecting tube was in clined. Prediction of fracture life by using the elastic-creep analysi s which used Garofalo type of the creep constitutive equation and the time fraction rule was very conservative as compared with the experime ntal fracture life.