THE EFFECT OF STEAM SEPARATOR EFFICIENCY ON TRANSIENT FOLLOWING A STEAM LINE BREAK

Detailed thermalhydraulic simulations for CANDU 6 steam line break ins ide containment are performed to predict the response of the primary a nd secondary circuits. The analysis is performed using the thermalhydr aulic computer code, CATHENA, with a coupled primary and secondary cir cuit model. A hue-loop representation of the primary and secondary cir cuits is modelled. The secondary circuit model includes the feedwater line from the deaerator storage tank multi-node steam generators and t he steam line up to the turbine. Two cases were carried our using diff erent assumptions for the efficiency of the steam separators. Case I a ssumes the efficiency of the steam separators becomes zero when the wa ter level in the steam drum increases to the elevation of primary cycl ones, or the outlet flow from the steam generator becomes higher than 150 % of normal flow. Case 2 assumes the efficiency becomes zero only when the water level in the steam drum reaches the elevation of primar y cyclones. The simulation results show that system responses are sens itive to the assumption for the efficiency of the steam separators and case I gives higher discharge energy. Fuel cooling is assured, since primary circuit is cooled down sufficiently by the steam generators fo r both cases. Copyright (C) 1996 Elsevier Science Ltd