Response of Soviet-Designed VVER-440 Steam Generator Vessel to Pressurization.

摘要

The Soviet-designed VVER (Water-Cooled, Water-Moderated Energy Reactors) pressurized water reactors use horizontal steam generators to transfer energy from the primary to secondary coolant systems (DOE/NE-0084 Revision 2, 1989). Primary coolant flowing from the reactor vessel enters the steam generator through a vertical, circular, manifold header that also serves as the tubesheet distributing coolant to the horizontal tube bundle. Primary coolant exits the tube bundle and steam generator through a second similar vertical manifold header. The header design includes the provision for access by a person to inspect the mainfolds through bolted down closure heads atop each manifold. The internal diameter of each header exceeds that of the connected primary coolant system piping. The postulated failure of a manifold closure head or the manifold itself provides a pathway for primary coolant to enter the secondary system. Steam formation due to flashing of primary coolant inside the steam generator secondary side region can result in pressurization of the steam generator shell to values above the nominal secondary side operating pressure. The present work involves the investigation of the consequences of manifold failure for the case of the VVER-440 reactor system. An analysis has been performed of the loadings upon and the mechanical response of the steam generator shell for the case of a postulated large break in the manifold wall. The objectives were to calculate the maximum pressure attained inside the shell and to predict the shell failure pressure as well as the failure mechanism. 6 refs., 8 figs., 1 tab.