Operational capability of heat transport pumps under two-phase flow conditions

Abstract

There are very few test data available which quantify the mechanical behaviour of large centrifugal pumps under two-phase flow conditions. In this paper an assessment of the mechanical capability of the CANDU heat transport (HT) pumps under two-phase flow conditions is described. A CANDU HT pump/motor set was tested under various postulated loss-of-coolant-accident (LOCA) conditions in a test loop. Based on the results of the tests, during which extensive data were obtained, it has been concluded that the pumps are capable of operating as required for all postulated LOCA conditions. Despite high vibration levels and pump shaft run-outs during the LOCA tests, the pump hydrostatic bearing and the mechanical seals did not have any significant damage. The pump/motor set also retained its pressure boundary integrity under various postulated LOCA conditions. In addition to the LOCA testing, the results of a rotor dynamics analysis are also presented. The analytical results also predict successful operability of the pump hydrostatic bearing under various LOCA conditions as was confirmed by the test program. © 1989.