The Passive Heat Removal Systems, which are studied in the frame of future nuclear plant reactor, use for the most part, a condenser immersed in a cooling pool.The circuit loop has two parts at very different temperatures, as a consequence thermalmechanical constraints on the isolating valves are present when these valves are closed. Moreover, thermalhydraulic instabilities can affect the heat removal behaviour and cause important local constraints at the valves opening. The system reliability is reduced.The Thermal Valve device (TV) allows to avoid the presence of mechanical valves on the Heat Removal Loops, in order to increase the system reliability. Moreover the device is applicable for all the in-pool heat exchangers operating with mechanical valves. With this device, the control of the thermal exchange is made by modifying the thermal exchange conditions in the pool.In order to confirm the thermalhydraulic stability of the natural convection in the different scenarios expected, some theoretical analyses have concerned the utilization of Thermal-Hydraulic Best Estimate codes (CATHARE 2 and RELAP 5) to calculate the thermalhydraulic behaviour of the Isolation Condenser system at steady state and transient conditions. The IC heat exchanger, taken as a reference here, is based on the condenser designed for the SBWR (GE's advanced Boiling Water Reactor).The benchmark approach chosen for the theoretical assessment, apart from confirming in an analytical way the capability of IC system to remove the residual heat, allows comparing the two codes on a same scenario. On this purpose similar nodalizations of the IC system and of the TV device for RELAP and CATHARE codes have been developed in order to reduce the user's effect.
Theoretical Design and Assessment of Isolation Condenser System Controlled with Thermal Valve Device
Meloni, P.
1998-05-10
Abstract
The Passive Heat Removal Systems, which are studied in the frame of future nuclear plant reactor, use for the most part, a condenser immersed in a cooling pool.The circuit loop has two parts at very different temperatures, as a consequence thermalmechanical constraints on the isolating valves are present when these valves are closed. Moreover, thermalhydraulic instabilities can affect the heat removal behaviour and cause important local constraints at the valves opening. The system reliability is reduced.The Thermal Valve device (TV) allows to avoid the presence of mechanical valves on the Heat Removal Loops, in order to increase the system reliability. Moreover the device is applicable for all the in-pool heat exchangers operating with mechanical valves. With this device, the control of the thermal exchange is made by modifying the thermal exchange conditions in the pool.In order to confirm the thermalhydraulic stability of the natural convection in the different scenarios expected, some theoretical analyses have concerned the utilization of Thermal-Hydraulic Best Estimate codes (CATHARE 2 and RELAP 5) to calculate the thermalhydraulic behaviour of the Isolation Condenser system at steady state and transient conditions. The IC heat exchanger, taken as a reference here, is based on the condenser designed for the SBWR (GE's advanced Boiling Water Reactor).The benchmark approach chosen for the theoretical assessment, apart from confirming in an analytical way the capability of IC system to remove the residual heat, allows comparing the two codes on a same scenario. On this purpose similar nodalizations of the IC system and of the TV device for RELAP and CATHARE codes have been developed in order to reduce the user's effect.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
